Research Collection
Doctoral Thesis
Arsenic uptake of common crop plants from contaminated soils
and interaction with phosphate
Author(s):
Gulz, Petra
Publication Date:
2003
Permanent Link:
https://doi.org/10.3929/ethz-a-004525606
Rights / License:
In Copyright - Non-Commercial Use Permitted
This page was generated automatically upon download from the ETH Zurich Research Collection. For more
information please consult the Terms of use.
ETH Library
DissETHNo. 14879
Arsenic
Uptake
of Common
Crop
Plants from
Contaminated Soils and Interaction with
Phosphate
Dissertation submitted to the
Swiss Federal Institute
for the
of
Technology Zurich
degree
of
Doctor of Natural Science
presented by
Petra Angela Gulz
Dipl. Geogr., University
born 9
in
Accepted
September
of Munich
1969
Munich, Germany
on
the recommendation of
Prof. Dr. Rainer
Dr. Satish-Kumar
Schulin, examiner
Gupta, co-examiner
Prof. Dr. Hans Rudolf Pfeifer, co-examiner
Zurich, 2002
Table of Contents
Page
I
Table of Contents
V
Summary
VII
Zusammenfassung
1
1.1
Phytoextraction
1.2 Research
1.3
2
1
Introduction
on
1
of arsenic
arsenic in Switzerland and framework of this
Fundamentals of Arsenic in Soils and Plants
-
a
symbol
for
2.2 Historical and modern
poison
use
and crime
of arsenic
compounds
2.4
2.3.1
General characteristics of arsenic
2.3.2
Geogenic
2.3.3
Atmospheric deposition
2.3.4
Agricultural
Physicochemical
2.4.1
Speciation
2.4.2
Sorption
2.4.3
Organic
of arsenic in the environment
arsenic
inputs
5
5
6
7
2.3 Arsenic in the environment
sources
2
3
Objectives of this study
2.1 Arsenic
study
7
8
9
into soils
9
behaviour of arsenic in soils
10
and transformation
10
and
desorption
arsenic
compounds
11
12
I
13
2.5 Arsenic and human health
2.5.1
Exposure pathways
13
2.5.1.1 Air
13
2.5.1.2
Food, beverages and drinking
2.5.1.3 Soil
13
water
14
ingestion
14
2.5.2 Toxicokinetics of arsenic
2.5.2.1 Acute arsenic
2.5.2.2 Chronic arsenic
poisoning
2.5.2.3 Chronic arsenic
poisoning
2.6 Arsenic in the
15
in
15
Bangladesh
16
soil-plant relationship
2.6.1
Arsenic in the soil and
2.6.2
Phytotoxicity
16
plant growth
17
of arsenic
2.6.3 Mechanisms of arsenic
uptake
2.6.4 Influence of phosphate
on
2.6.5
14
poisoning
Hyperaccumulation
arsenic
18
19
uptake by plants
19
of arsenic
Arsenic Accumulation of Common Plants from Contaminated Soils
21
3.1 Introduction
22
3.2 Materials and methods
25
Soils
25
3.2.2 As addition
26
3.2.3 Plant material and cultivation
27
3.2.1
3.2.4 Plant and soil
3.2.5 Statistical
27
sampling and analysis
28
analysis
28
3.3 Results
3.3.1
Soluble As and P concentrations and
3.3.2 As distribution and concentrations in
3.3.3 Effect of As addition
on
28
pH
plants affected by As
37
As accumulation and distribution in different
3.4.2 Effect of As addition
II
30
35
yield
3.4 Discussion
3.4.1
treatment
on
plant growth
plant parts
37
39
Effects of Phosphate
on
Arsenic
Availability in
Soils and
Growth of Sunflower
41
4.1 Introduction
42
4.2 Materials and methods
44
4.2.1
44
Soils
4.2.2 Batch
4.2.3 Pot
45
experiment
46
experiment
4.2.4 Plant and soil
46
analysis
47
4.3 Results
Effect of P treatments
on
soluble P and As in the batch
4.3.2 Effect of P treatments
on
soluble P and As in the pot
4.3.3 Effect of P treatments
on
As and P
4.3.4 Effect of P treatments
on
As
4.3.1
uptake by
toxicity
and
experiment
experiment
sunflower
yield
of sunflower
Effect of P addition
on
soluble P and As concentrations
4.4.2 Effect of P addition
on
As
uptake by
4.4.3 Effect ofP addition
on
As
toxicity
P-enhanced
Soil
using
49
51
54
55
4.4 Discussion
4.4.1
47
Phytoextraction
sunflower
and
yield
of sunflower
55
56
57
of Arsenic from Contaminated
59
Sunflower
5.1 Introduction
60
5.2 Materials and methods
62
62
5.2.1
Soil material
5.2.2
Experimental design and phosphate
5.2.3
Soil and
plant sampling
5.2.4 Statistical
and
treatments
63
analysis
64
analysis
64
5.3 Results
5.3.1
Effect of P addition
5.3.2 Arsenic and
5.3.3 Visual
on
phosphate
soluble P and As concentrations
accumulation
toxicity symptoms
and
growth
Effect of P addition
64
sunflower
66
of sunflower
70
by
71
5.4 Discussion
5.4.1
62
on
soluble As and P concentrations
71
III
5.4.2 Effect of P addition
on
As and P
5.4.3 Effect of P addition
on
growth
5.4.4
6
Efficiency
of As
sunflower
phytoextraction using
uptake
sunflower
and
growth
6.3 P-enhanced
Literature
on
77
plants
As-solubility
in the soil and
As-uptake
78
of sunflower
phytoextraction
6.4 Outlook and open
74
77
of common crop
6.2 Effects of P addition
72
73
of sunflower
Concluding Summary
6.1 Arsenic
7
uptake by
questions
of As from contaminated soils
78
79
81
Appendix
1
90
Appendix
2
91
Appendix
3
93
Acknowledgments
97
Curriculum vitae
99
IV
Summary
Large-scale groundwater pollution by geogenic
Bangladesh
prime
recently promoted
has
Since then
concern.
this element into
widespread water,
(As)
arsenic
in
environmental
an
and
West-Bengal
pollutant
soil and crop contaminations have been
identified in many parts of the world. Evoked
by
the risk of As
the food
entering
chain, the detection of As-contaminated agricultural soils has renewed the interest
studying the dynamics of As
In
Switzerland, until
arsenic soil
pollution
Swiss limit of 50 ]ig
as
well
L"1
was
as
arsenic concentrations in
research
part of
interdisciplinary project between
Protection and
Agriculture (IUL),
Zurich and the
University
effect of
as
of this PhD thesis
goal
the
phosphate (P)
possibility
the
Following
loam).
a
P
groundwater
to examine the
on
plants
that
to
with the title:
calcareous
»Speciation
and
As-uptake and growth
for
phytoextraction
phosphate
and arsenate
Regosol (silty loam)
were
and transfer
plants«.
on
are
of crop
and
same
a
plant,
plants
as
the
well
As-contaminated soils.
taken up via the
demanding and biomass producing plants
Different doses of arsenic
is
Technology (ETH)
transfer of As from soil to
ryegrass, rape and sunflower. The
maize, English
experiments:
was
of using crop
uptake mechanisms, high
(CAM)
pathways
study
the former Institute of Environmental
the Swiss Federal Institute of
fertilization
hypothesis
on
of Lausanne
of arsenic in contaminated soils:
The
water above the
arsenic in Switzerland. The present
more
an
drinking
Recently,
found in the cantons Wallis, Graubünden and Ticino.
This led to
systematic
in
in the soil environment.
little is known about arsenic in the environment.
now
of
two soils
non-calcareous
were
were
same
chosen:
used in all
Regosol (sandy
added to the soils to obtain different soluble As
concentration levels.
The
soils
uptake
was
of As
by maize,
studied in
nations most As
was
a
ryegrass, rape and sunflower from arsenic contaminated
pot experiment in the greenhouse. In all soil-plant combi¬
accumulated in the roots.
Although
accumulation above
ground
V
remained much lower, As concentrations in stems, leaves and seeds reached values
above the Swiss tolerance limits for food
As
kg-1, respectively),
from roots to
In batch
fertilization
production
kg"1)
well
as
phosphorous
growth
P and As
was
a
as
chamber
availability
in the
soil,
As
growth
To
(greenhouse)
replicated
P.
silty loam, indicating
the
was
potential
that
on
a
uptake by
the
was
soluble As concentrations
at
only
soluble As led to
applied
capacity
plant
effect in the
pot experiment
a
levels, each
contaminated soil enhanced As accumulation
were
not
loam this effect occurred
silty
increased
the
on
as
increase As accumulation in the
reported
for the
demanding plants
the food chain,
especially
silty
of the soil
fertilization did not affect
in different concentration
was
plants,
11.42 mg As
hyperaccumulating
on
sandy
loam.
but also reduced
when these sites
of As-contaminated soils.
as
plant-1.
well
as
a
are
was
This is close
ferns. However,
As contaminated soils
As concentrations in sunflower shoots demonstrate
VI
fixation
heavy root damages, decreased growth
Cultivation of high P
phytoextraction
mg P
low As concentrations. The maximum rate of As-extraction
to the maximum values
entering
(56
lower in the
was
significant growth enhancing
a
obtained at low soluble As concentrations and
As
base P-fertilization
deficiency.
P
two times. P addition to As
toxicity
sunflower and biomass
of sunflower to extract As from soil,
carried out. P
Addition of P did not
a
soluble As
in roots and shoots of sunflower. On the calcareous
although
phosphourous (P)
the effects of
high
Phosphorous
soil, but had
in As-contaminated
investigate
As translocation of sunflower
in the roots and shoots of sunflower
uptake
sandy loam, indicating
mobilizing effect of
uncontaminated
has to be taken
increase of soluble P and As concentrations in the soil. P
at low soluble As concentrations. The P-effect
lessened the
high
the addition of
addition further tended to increase As
sand than in the
and 4 mg
kg"
performed by using this plant species.
experiments
investigated. Already
significant
were
plants
demand of the
of crops. Due to the
shoots, further experiments
on
led to
as
predict As uptake
well
as
mg As
(0.2
except for maize. Results suggest that beside As solubility,
phosphorous availability
into account to
fodder crops
or
high
As-export.
can
create a risk of
fertilized with P. The
large potential
of this
high
plant
for
Zusammenfassung
Arsenbelastungen des
Grundwassers in
West-Bengalen
den letzten Jahren das hoch toxische Element Arsen in den
forschung
von
Bangladesch
und
Brennpunkt
rücken lassen. Seither sind in vielen Teilen der Welt
haben in
der Umwelt¬
Arsenbelastungen
Grundwasservorkommen, Böden und den darauf angebauten Pflanzen identifi¬
Entdeckung
ziert worden. Vor allem die
arsenbelasteten landwirtschaftlichen
von
Flächen und das damit verbundene Risiko eines Arsentransfers über den Boden-
Pflanzenpfad
in die
Nahrungskette
haben das Interesse
an
der
dieses
Erforschung
Wirkungspfads geweckt.
Bis heute ist in der Schweiz über das Ausmass
wenig bekannt.
In den Kantonen
von
Arsenbelastungen
Wallis, Graubünden und dem Tessin hat
Grundvorkommen, die den schweizerischen Grenzwert für Arsen
von
überschritten, arsenbelastete Böden entdeckt. Dies hat die Erforschung
der schweizerischen Umwelt intensiviert. Die hier
interdisziplinären Forschungsprojekts zwischen
schutz und Landwirtschaft
(IUL),
(ETH) Zürich und der Universität
ierung
und der Transfer
wasser
und
Im
zu
von
der
dem
Mittelpunkt
der hier
vom
ihrer Nutzung für die
von
L'1
Arsen in
ehemaligen
Institut für Umwelt¬
Technischen Hochschule
in dessen Rahmen die
Arsen in belasteten Böden:
vorgestellten
Boden in
Arbeit stand die
Kulturpflanzen,
Wirkungspfad
zum
»SpeziGrund¬
die
Pflanzen
Versuchspflanzen
Untersuchung des
Wirkung
der
Arsen-
Phosphatdüngung
Pflanzen, sowie die Möglichkeit
Phytoextraktion.
Die Pflanzenauswahl basierte auf der
hohen
50 ng
Arbeit ist Teil eines
(CAM),
auf die Arsenaufnahme und das Wachstum dieser
den
neben
präsentierte
Eidgenössischen
Lausanne
man
den Pflanzen« untersucht wurde.
Wirkungspfads
von
der Umwelt
über
den
Tatsache, dass Phosphat (P) und
Arsenate
gleichen Mechanismus aufgenommen
wurden somit Pflanzen mit einem hohen
(AsV)
werden.
Phosphatbedarf und
Biomassenproduktion ausgewählt: Mais, Englisches Raygras, Raps
Als
einer
und Sonnen-
VII
blumen. Die verwendeten Böden
und ein
Sonnenblumen
aus
von
eingestellt.
Mais, Raygras, Raps und
vom
in
hauptsächlich
kontaminierten Böden untersucht. Arsen wurde
Abgesehen
Arsen
an
Mais überschritten die Arsen-Gehalte der
Blätter und Früchte die schweizerischen Grenzwerte für Arsen in Futter- und
Lebensmittel
(4
mg
kg"1
bzw. 0.2 mg
sage der Arsenaufnahme
von
im Boden
wurde die Arsenaufnahme
der Wurzel akkumuliert.
Stengel,
Zugabe abgestufter Mengen
Arsengehalte
wurden unterschiedliche lösliche
Topfversuch
kalkhaltiger Regosol (schluffiger Lehm)
Durch die
Regosol (sandiger Lehm).
In einem
ein
waren
Phosphat
Der Einfluss
sowie der
von
von
kg"1).
Ergebnisse zeigen,
Die
dass
Pflanzen neben der Arsenlöslichkeit, die
zur
Vorher¬
Verfügbarkeit
Phosphorbedarf der Pflanzen berücksichtigt werden müssen.
Phosphat
Phosphor-
auf die
und
Arsen-Verfügbarkeit
im
Boden,
die Arsenaufnahme der Sonnenblume sowie deren Biomasse wurde in einem Batch-
und einem
löslichen
Fixierung
sandigen
Topfversuch untersucht.
Phosphordes
Vor
Phosphor-Zugabe
allem
dem
im
wurde die
(Gewächshaus)
untersucht. Die
Fähigkeit
als im
erhöhte
die
der Sonnen¬
Phosphorzugabe erfolgte
von
der Höhe der
Lehm beobachtet, obwohl die
gleichen
Phosphor-Zugabe erniedrigte
vor
Masse wie im
in unter¬
Zugabe erhöhte
Wurzelschädigungen,
Der maximale
Phosphor-Zugabe
sandigen Lehm erhöht
allem bei tiefen löslichen
Pflanzentoxizität. Bei hohen löslichen As-Gehalten
Arsen-Entzug.
war
die
die Arsenaufnahme der Sonnenblume. Dieser Effekt wurde auch auf
kalkhaltigen schluffigen
ausgeprägten
Phosphor erhöhte die
Lehm schwächer
schluffigen
Dosierungen. Unabhängig
löslichen As-Gehalte nicht im
Die
kg"1
die Arsenaufhahme der Sonnenblume.
Phytoextraktion
Phosphorzugabe
56 mg
niedrigen löslichen Arsengehalten
bei
In einem weiteren Gefässversuch
schiedlich hohen
von
wie auch Arsen-Gehalte, wobei dieser Effekt wegen der hohen
zugegebenen Phosphors
Lehm.
blume für die
Zugabe
Die
gehemmtem
Arsenentzug
von
hatte.
Arsengehalten
hingegen führte die P-Zugabe
Wachstum
und
die
die
zu
vermindertem
11.42 mg As pro Pflanze
liegt
in der
Grössenordung hyperakkumulierender Farne.
Vor allem auf arsenbelasteten und
Anpflanzen
von
Nahrungskette
Kulturpflanzen
führen. Die hohen
gleichzeitig Phosphor gedüngten
mit einem hohen
Arsengehalte
im
P-Bedarf,
Problemen in der
Spross der Sonnenblume zeigen das
grosse Potenzial dieser Pflanze für einen Einsatz in der
VIII
zu
Böden kann das
Phytoextraktion.
Introduction
1
Large-scale
has
water
pollution by geogenic
recently promoted
this element into
(see 2.5.2.3). Since then, widespread
release of arsenic from
of arsenical
agricultural
soils
pesticides
the
flooded
more
has
worldwide
led
pollutant of prime
concern
by natural
to
contamination
extensive
Given the known
toxicity
(Smith, 1998). Furthermore,
arable land and parts of the
after
park (Rauret, 1999; Sassoon, 1998)
of As, indiscriminate
occurrence
in 1997, where arsenic
Spain
km2
than 4'300
Bangladesh
of As, the
the accident at the
containing
tailings
mine
Donana National
nearby
dam break revealed
a
of
the world has renewed the interest in
throughout
of As in the soil
Aznalcöllar Mine in Southern
and
water and crop contaminations created
(Smith, 1998; Woolson, 1975).
dynamics
West-Bengal
environmental
Beside the natural
detection of As-contaminated sites
studying
an
in
(As)
rocks have been identified in many parts of the world
aquifer
(Smedley and Kinniburgh, 2002).
use
arsenic
a
serious lack of
management and remediation technologies for As contaminated arable land.
1.1
Phytoextraction
of arsenic
A number of authors have
from soil
plants
soil
to accumulate
McGrath et al,
pollutants
on
alternative to soil-destructive treatments. Suitable
accumulate very
do not
high
amounts
produce
remains limited. Arsenic
a
large
of
a
are
pollutant
capability
the
as
a
of certain
those is the
low-cost, in situ and
for
plants
phytoextraction
hyperaccumulators.
in the harvestable
biomass. Therefore the total
hyperaccumulators
contaminant metals
considerably exceeding
proposed
has been
be divided into two groups. The first
usually
to remove
1993). Based
in concentrations
(Brook, 1998), phytoextraction
'green'
can
(Baker, 2001;
proposed phytoextraction
These
plant parts,
pollutant
have been identified
plants
only
but
extraction
very
recently
1
Chapter
1
(Francesconi
accumulators, but produce
may
even
a
large
biomass
that the total removal of the
so
exceed that of hyperaccumulators. While there is
accumulation of
most of the recent studies have
plants,
1992; Peryea, 1998) and the influence of phosphate
al., 2002; Clark
so
far to As
possible
use
on
As
focussed
on
Meharg
uptake
pollutant
and Macnair,
kinetics
(Abedin
uptake by
common
of these
plants
for
crop
from As contaminated soils and the
plants
Therefore almost
phytoextraction.
literature
no
this
topic.
1.2
Research
on
arsenic in Switzerland and framework of this
In Switzerland little is known about the extent of past
of arsenic to the environment.
element has started
only
waters have been found
L"1,
early
1990s
of persons
of former
research
exposed
these
et
on
arsenic
water
kg"1
on a
1999,
NABO
a
in the cantons
Cases of chronic
As-contaminated drinking water have been
sites and in
areas
dry weight
basis
on
soil contaminations in the
where the soil is derived from As
was
found to accumulate
these sites. This value is 10 times
plants (FMV, 1995).
report summarizing the As data of the Swiss Soil Monitoring Network
(Knecht
et
background value
prime
environmental
as an
mining sites
above the allowed Swiss limit for As concentrations in fodder
In
study
anthropogenic inputs
(FIV, 1998).
moraine material have been identified. Grass
than 40 mg As
be
with arsenic concentrations well
(Peters, 2001). Additionally,
mining
can
al., 2002). Accidentally, arsenic rich
areas
drinking
to
actual
or
abandoned
on
al., 1999; Pfeifer
clearly outside
in Graubünden
neighbourhood
more
et
Systematic
the Swiss limit for
poisoning
containing
in the
(Pfeifer
Ticino and Wallis
recognized
et
al., 2000; Meharg and Macnair, 1994). Little attention has been paid
et
concerning
arsenic
genetic
the
found
above 50 \xg
hyper¬
interest into As
increasing
and Macnair, 1991;
(Meharg
identification of As tolerance
than
pollutant concentrations
which accumulate lower
plants
consists of
al., 2001; Tu and Ma, 2002). The second group
Ma et
al., 2002;
et
concern
al., 1999) pointed
out that
only
few
of As. The authors concluded that arsenic
and therefore
no
effort
was
samples
was no
necessary to introduce
exceeded the
contaminant of
guide and
limit
values for As concentrations in soils. It has to be considered that the NABO sites
2
Introduction
represent the background concentrations of pollutants in Swiss soils without
As contamination
considering possible
attention has been devoted
This
study
is
a
1.3
Objectives
Until
now
pathways
of this
results in
focus
on
consequences
particular,
•
the
How is As
on
for
focussing
binding
practice
phosphate
uptake and
As
of
transfer
and
in
arsenic
plants«.
common
biomass
crop
Is soil amendment of phosphate
a
on
in
the risk of As
entering
the food
similarity between phosphate
sites
in the soil
and
plant uptake.
and
agriculture. Therefore,
production
it is
important
of
plants.
crop
common
In
were:
plants
related to As concentrations in the soil
and how is accumulated As distributed in crop
•
Foundation) project (No.
addition to As-contaminated soils and the
following questions addressed
uptake by
and
The chemical
a common
the effect of
scant
study
competition
is
only
from this report,
Science
»Speciation
groundwater's
soil-plant pathway.
Phosphate fertilization
to
to
little research has been done
chain via the
arsenate
(Swiss National
20.61860.00) titled:
contaminated soils:
Apart
far to the status and fate of As in Swiss soils.
result of the NSF
and
21.52758.97
so
sources.
plants?
suitable method to enhance As
uptake by
crop
plants?
•
How efficient
The fundamentals
in the
For
are
plants
concerning
soil-plant relationship
studying the
ryegrass, rape and
using
crop
two
As
in
removing
As sources, As
are
described in
uptake potential
sunflower)
a
As from contaminated soils?
chemistry and the behaviour of arsenic
Chapter
of
2.
common
crop
plants (maize, English
pot experiment in the greenhouse
soils, different in soil properties but similar in soluble
(Chapter 3). Sunflower proved
subsequent investigations
were
to
be
the
most
restricted to this
efficient
As
was
carried out
As concentrations
accumulator
and
plant.
3
Chapter
The
1
mobilising
three different
effect of
phosphate salts
pot experiment in
Finally,
phosphate
a
assess
a
the
growth
efficiency
in batch
This effect
chamber
experiments,
was
in which
verified later
on
in
a
(Chapter 4).
of sunflower to extract As from As-
pot experiment in the greenhouse
different levels of phosphate addition
4
investigated
compared.
climate-controlled
in order to
contaminated soils,
were
was
(Chapter 5).
was
carried out with four
Fundamentals of Arsenic in Soils and Plants
2
2.1
Arsenic
-
The word arsenic
a
symbol for poison
(As)
it
properties. Currently
and
myth,
has made its way
belongs
and crime
through history
general vocabulary,
to the
synonym for »toxic«. Since white arsenic
as a
the
on
strength
surrounded
(AS2O3)
of its
killing
by mystery
is odourless and
tasteless, it has remained the »king of poisons« for people with evil intentions.
France, the jocose
arsenic
to
laughing
was no
regard
name
matter to the heads of the
all relatives and friends with extreme
White arsenic sublimes
poisoned
»poudre de succession«,
wicks
were
on
to
the
point
powder,
great families who
suspicion (Azcue
I of Austria in 1670
Leopold
the nineteenth century, white arsenic
practitioners,
inheritance
and
for white
were
inclined
Nriagu, 1994).
and it has been claimed that candles with
heating,
used to kill
or
In
was
where laws
the
were
Until
(Bagachi, 1969).
preferred poison
of most homicidal
of it
passed against the possession
(Emsley, 1985).
Beside the criminal
use
poisoning due
use
wallpapers,
the
to the
soaps and
of arsenical
wrapping
wallpaper (Bagachi, 1969).
Ambassador to
Italy might
arsenate-containing
pigments
was
of accidental arsenic
colouring artificial flowers, toys,
A vast literature discusses
reported.
due to arsenic
have been due to arsenic
flakes of green
cases
containing pigments
in his
Also the death of Clare Boothe Luce, the U.S.
paint, falling
seventeenth-century embassy that
caused her death
for
paper have been
hypothesis that Napoleon's death
bedroom
the
of white arsenic, also many
she used
poisoning. Supposedly
from the
as
a
ceiling
lead
of the bedroom in
private office,
have
possibly
(Lenihan, 1988).
5
Chapter
2.2
2
Historical and modern
use
of arsenic
about and the first
uses
of arsenic in
knowledge
The
Some authors believe it
topic.
tendency
some
countries, Coghlan (1975) suggested
accepted Copper Age.
The
properties
an
BC)
copper-arsenic alloys
(Lechtman, 1980).
silvery
Arsenic
surface effect
ingredients
on
mirrors and animal statuettes and
in the manufacture of
copper white
the whiteness of
Although
in
mainly realgar (AsS)
a
role in alchemical
operations
the
widely been used for alloying
antiquity
as a
were
pharmaceutical
widely
used to treat
and diabetes
(Leonard, 1991). Finally,
Paul
to turn
acquires
belief that copper
his
philosophy
of arsenic
variety
that
as
only
use
part of the modern
the
was
of illnesses
»de
of
use
of the sixteenth century,
(1% potassium arsenite)
a
uses
dosage
discovered and
over
Valagin's«
makes
the next 150
solution
(arsenic
rheumatism, arthritis, asthma, malaria, tuberculosis,
it
by
Arsenic
who recommended the
beginning
(arsenic iodide) and
trichloride),
1909
yellow
capability
ores, the main
(469-377 BC)
used medication for
years. Like »Donovan's« solution
was
red and
and medicinal. The medical
treatment for ulcers. At the
In 1786 »Fowler's« solution
became the most
6
to the
revolutionary Paracelsus (1493-1541 AD) designated arsenic
poison.
fluxing
(Meyer, 1975).
pharmacopoeia (Hunter, 1978), following
the
because of its
silver); indeed, this contributed substantially
realgar paste
a
of the
one
recipes previously described by Greek philosophers.
arsenic dates back to the time of Hippocrates
of
produce
red copper oxide is heated with white arsenic oxides it
arsenic has
compounds
Andes
Central
bright
(fourth
and Arabic alchemists have
be transmuted into silver
can
in Iran
by
during antiquity. Mainly Egyptian
important
(when
valued
orpiment (AS2S3), continued
studied and tested the
an
Yahya
as
The
glass (Coghlan, 1975).
in
alloys
and
to fascinate chemists
played
were
of the
artisans
strong
rather than the
also used in the third millennium BC to
was
colours of the arsenic minerals,
also
Chimu
pre-Columbian
the
to
a
of arsenical copper in
prevalence
metal smiths in many parts of the world, from those of the Tape
millennium
controversial
to copper
Arsenical-Copper Age,
of the
a
but there is
antiquity,
deliberately added
Because of the
(Brown, 1948).
times
was
remains
antiquity
not known in
support the theory that arsenic
to
prehistoric
was
compounds
the
discovery of »Salvarsan« (arsphenamine)
in
Ehrlich, the founder of modern chemotherapy, made it the main
Fundamentals
medicine
and
against syphilis
until the
ofArsenic
in the
discovery of antibiotics
in Soils and Plants
early
1940s
(Azcue
Nriagu, 1994).
of other useful
findings
With the
in the last 150 years.
Being
silver, cobalt, lead, gold,
used
as
pesticide
a
maximum
the
in
an
the
properties
use
of arsenic increased
inexpensive by-product
manganese, and tin
of the
smelting
(Leonard, 1991), arsenic
exponentially
of copper, iron,
widely
became
in the wake of the industrial revolution. This usage reached
Then
1950s.
it
progressively
was
and
largely replaced by
organochlorine pesticides (Azcue and Nriagu, 1994). Nevertheless, the major
arsenic
today
primarily
is still in the
fireworks
glass, electronics, pigments
minor constituent to Cu and Cu-based
metals
(Azcue
and
and
alloys
antifouling agents,
2.3
given
in
chapter
cosmetics and
to raise the corrosion resistance
1994),
as
a
of the
remains to be used
desiccant, rodenticide, and herbicide (Bhumbla and Keefer,
discussion is
of
include the manufacture of
agriculture, arsenic
In
Nriagu, 1994).
uses
times, arsenic is also still added
As in the ancient
(Leonard, 1991).
use
field. For industrial purposes, arsenic is
agricultural
used in the form of As trioxide. Industrial
ceramics and
a
as
a
detailed
a
2.3.4.
Arsenic in the environment
2.3.1
General characteristics of arsenic
Arsenic is
a
metalloid of
not sufficient to
give
metalloid.
oxidation
The
phosphorus.
As
Group
and
states
alloys
oxygen, and
forms
inorganic
form
Arsines
are
(grey being
as
most
electron
It
occurs
crystalline
stable).
trivalent arsenite
volatile As
Its
electronegativity
orbitals
are
similar
to
as
those
is
a
of
with various metals and bonds covalent with
sulphur.
+III and +V. Elemental arsenic is
allotropie
periodic system.
metallic character. Therefore it is often described
a
Arsenic forms
carbon, hydrogen,
VA in the
in different oxidation states:
and exists in
yellow, black
In nature, arsenic exists
(As (III))
or
(-III) compounds deriving
pentavalent
from
organic
or
grey
predominantly
arsenate
or
-III, 0,
in
(As (V)).
inorganic
arsenic
compounds.
7
Chapter 2
2.3.2
Geogenic
Arsenic is
every
sources
ubiquitous
environmental
of arsenic in the environment
in nature and small amount of this element
compartment.
shows
2.1
Figure
can
sources
and
common
As-
arsenic
the
be found in
distribution in the environmental compartments.
Arsenic is
a
constituent of
major
containing mineral
when
exposed
to
than 245 minerals. The most
(Woolson, 1983). Arsenic-sulphides readily oxidize
air, yielding inorganic arsenic salts which
The arsenic content of
(Woolson, 1983).
kg"1);
is FeAsS
more
the average content is 2 to 3 mg
igneous
kg"1.
are
rocks varies
Sedimentary
highly
water-soluble
widely (up
to 100 mg
rocks also vary in their
arsenic content, from small amounts in limestone and sandstone up to 15'000 mg
in
some
manganese
0.1 and 40 mg As
ores
kg"1,
(Yan-Chu, 1994).
8'000 mg As
kg"1
can
Fig.
2.1 Schematic
L'1,
1987).
(see 2.5.2.3). The
the
at
representation
kg"1 (Colburn
of the arsenic
Due to the
high pH,
al, 1975;
solubility
of certain
As concentrations in
drinking water,
is 10 ug As
set
by
L"1 (WHO, 2001).
cycle illustrating
compartments.
et
may have concentrations up to
limit for As in
provisional guideline
in the various environmental
8
deposits
decreasing sorption
be elevated
the WHO, is 50 u.g As
ore
and Peterson,
(Chilvers
arsenic minerals and the
groundwater
Uncontaminated soils contain between
the average content is 5 to 6 mg
O'Neill, 1995). Soils overlying sulphide
kg"1
the fate of arsenic
Fundamentals
in Soils and Plants
ofArsenic
Atmospheric deposition
2.3.3
naturally present
Arsenic is
in most
of these metals, arsenic is released
atmosphere by
removed from the
into the
source
(Peterson
is
atmosphere
through
et
ores
and
during
the
smelting
gaseous and solid waste emission. As it is
rainfall in the
(Woolson, 1983),
concentrations remain low
the emission
lead, copper, and gold
of smelters,
vicinity
atmospheric
while it accumulate in the soils around
al., 1981). Another important
coal-burning during electrical
source
of As emission
production
power
and
heating.
Arsenic concentrations in coal from the USA, Australia and the UK range from
around 0.5
93
to
Czechoslovakia)
largely
exists
was
plants. Fly ash particles
be
(Peterson
et
al., 1981). Brown coal (from the
found to contain up to 1'500 mg As
arsenopyrite
as
Consequently,
kg"1
mg As
can
in coal. It is emitted
as
kg"1
(Peterson
et
of coal-fired power
surrounding
Arsenic
arsenic trioxide from power
contain up to 1'700 mg As
soil contaminations in the
kg"1 (Piver, 1983).
al., 1981).
plants
can
significant.
Agricultural
2.3.4
Pesticides
are
Numerous
pesticides
cases
et
Woolson
sources
into soils
of As contamination of
reported (Merry
et
soils
agricultural
of As in
lead arsenate
(PbAs04),
agricultural
al., 1986;
(ZnAs04),
zinc arsenate
Peterson et
and Paris green
in
al., 1983). Soil pollution by
As
extensively
as
(Jiang
Singh, 1994).
containing
al., 1981; Woolson
et
dichlorodiphenyltrichloro-
(CaAs04), magnesium
arsenate
[Cu(CH3COO)2*3Cu(As02)2]
agriculture (Anastasia
pesticides
and
soils due to arsenic
calcium arsenate
pesticides
used
Merry
inputs
From the late 1800s until the introduction of
(DDT),
(MgAs04),
were
major
have been
al., 1971a).
ethane
the
arsenic
has been
and Kender, 1973;
extensively reported by
(1975), Merry et a. (1983), and Nriagu (1994).
With the introduction of
inorganic
to the
organochlorine pesticides
acid
Due to the essential role of As in animal
role
a
shift from the
organic pesticides (monosodium methylarsonate (MSMA), disodium
methylarsonate (DSMA), dimethylarsinic
important
there has been
as
(cacodylic acid),
and arsenic acid).
nutrition, organic arsenicals play
food additives to promote the
growth
of farm animals
an
(Christen,
9
Chapter 2
2001).
In addition
they
solutions
control
2.4
are
as
an
as
used for
ingredient
desiccants and defoliants in the cotton
in cattle and
arsenic
sodium arsenite
and in
sheep dips,
aquatic weed
(Azcue and Nriagu, 1994).
Speciation
behaviour of arsenic in soils
and transformation
The chemical forms of arsenic present in soils
sorbing
industry
immense controversy, also arsenic
preservatives, while
of wood
debarking trees,
Physicochemical
2.4.1
used
(Woolson, 1975). Despite
and for weed control
acid is still used
are
soil components, the
species
which
are
pH,
depend
on
the types and amounts of
potential (Eh). Figure
and the redox
2.2 shows the
present under typical soil conditions.
i
1200
1
i
l
i
20
H3As04°
15
800
HjAs04
10
P^^
400
HAs042
\^
B
H3As03D
0
AsO„3
-
\^
-400
H2As03
\As<V
10
HAs032
-800
i
i
^~""L15
iii-
i
10
12
14
PH
Figure
and
10
species in dependency
Kinniburgh, (2001)
2.2 Arsenic
on
pH and Eh
at 25
°C, Source: Smedley
Fundamentals
arsenate.
over
As forms
important inorganic
The most
H2ASO4" is dominant
and
conditions
H3ASO4 and
conditions
at
Eh. Under
decreasing
ASO43"
stable
occur
also
Under
reducing
important
in the environment. In soil systems
Iron oxides
since arsenite is about 5
(Woolson,
oxidation and reduction of arsenic forms
biological
and
are
water-soluble than arsenate
more
often lead to substantial deviations form
•
extremely acidic and alkaline
(Sadiq, 1997).
plants and
toxic to
1983). Both, chemical
known to
dominate
oxidizing conditions
present, respectively.
be
may
The oxidation/reduction of arsenite/arsenate
more
(V) should
pH values below 9, the uncharged arsenite species H3ASO3 is
thermodynamically most
times
that As
pentavalent
pH (< 7) and high Eh (> +100mV), while HAs042~ becomes
at low
higher pH
dominant at
predict
conditions. Under
strongly reducing
in all but
(III)
As
in Soils and Plants
the trivalent arsenite and the
are
calculations
Equilibrium thermodynamic
ofArsenic
heterogeneity
are
and kinetic effects
theoretically expected equilibrium speciation:
promote oxidation of arsenite. Yan-Chu (1994) found that
can
after 72 hours little oxidation had occurred in
a
batch
experiment
and that
the kinetics of the redox reaction between arsenite and iron oxides is
relatively
low.
system and
are
Manganese oxides
very effective oxidants with
Even at very low Eh
microbial oxidation
Woolson and Kearney
they
are
Consequently
dominated
Due
to
arsenate
and
physical
induced
et
some
respect
depend
on
to
arsenite.
the microbial
arsenate may still
activity.
remain, due
to
al., 1996).
that arsenicals,
regardless
of the form in
become oxidized and metabolized to arsenate.
systems, except flooded soils, the chemistry of arsenic is
in most soil
of arsenate.
desorption
and
competes for the
phosphate
(Peters
(1973) postulated
by the chemistry
the
values,
applied, eventually
Sorption
2.4.2
also active components in the soil
Redox reactions of arsenic in soils also
•
which
are
chemical
same
similarity
adsorption
ligand exchange.
The
between
phosphate
and arsenate,
sites in the soil and will be mobilized
sorption/desorption capacity
by
of a soil for As
11
Chapter
2
primarily depends
other
clay and sesquioxide content,
its
on
such
compounds
extensive literature
as
adsorption by
As
on
phosphate (Peterson
oxides, little information is available
on
pure and
As
as
well
the presence of
as on
al., 1981). Compared
et
and
desorption
the
silicates and
synthetically produced
adsorption
to
in natural soils
(Smith, 1998).
Arsenate adsorbs
specifically
surface
area
and low content of
al., 1997). Arsenate
for soil calcium while
can
can
At
Organic
In the last two
transformation of
»methylation«,
of this reaction
1993)
As
inorganic
to
as one or more
are
a
cations
preference
significant
the
of fulvic
OH-groups
bindings (Lippke
present in soils and form
a
preference
for soil aluminium. Arsenate
forming sparingly
of
organic
arsenic
OH-groups
found
arsenic
species
monomethylarsonic
compounds
pathway represents
sources
shows
and aluminium,
organic
anaerobic conditions,
a
numerous
the low
soluble
compounds.
compounds
are
are
volatile.
apparently by
a
in
to
Methylation
Microbial
occurs
replaced by CH3-groups.
and di- and
separate the
soil.
the
compounds generally
The
through
products
trimethylarsines (O'Neill, 1995).
exist in both, the trivalent and
and most of them
Although
assumed that the
to
investigated
decades, experimental techniques have been developed
inorganic and the
Organic
adsorption capacity due
Few studies have
Pfeifer,
and carbonates
clay minerals
higher concentrations, arsenicals show
phosphate
arsenic
on
and
(Halter
of arsenic acids form ester-like
react with
precipitate with phosphate
2.4.3
12
OH-groups
compounds.
stable insoluble
sesquioxides.
matter. It is
organic
on
and humic acids and the
et
also
Sand and silt fractions show little
of arsenic
adsorption
Al- and Fe-Oxides
to a lesser extent
1999; Sadiq and Mian, 1983),
(Smith, 1998).
hydrous
on
pentavalent
can occur
states
(Vaughan,
under either aerobic
or
variety of micro-organisms (Woolson, 1983).
fraction of arsenic may be lost from soil
by volatilization,
this
less than 0.01 % of the total arsenic emissions from natural
(Woolson, 1983).
Fundamentals
Arsenic and human health
2.5
2.5.1
Exposure pathways
Humans may be
air and
drinking
water
and
2.5.1.1
Air
People
who
drinking
be
exposed
and
Pulmonary
and Lin,
arsenic
commonly associated
processing
from airborne
In
of arsenic
of elevated
wood
or
workplaces
preservatives
generally
below 10
control
^ig/m (WHO, 2001).
As/day for non-smokers
atmospheric arsenic,
higher,
containing
up-to-date
with
i.e. in the
vicinity
There
are
few data
beverages
on
the
organoarsenic compounds
appears to pose little health risk to animals and
compounds
1992).
As
In
are
rapidly excreted
general,
in
uncharged
L'1 (Abernathy, 2001), except
in
areas
are
low
in marine seafood
humans, because the ingested As
forms
arsenic levels in natural waters
lies
concen¬
tration of arsenic in human breast milk. Available data indicate that levels
of
of
however.
of food and
consumption
|ag/day (Abernathy, 2001).
(Abernathy, 2001). Accumulation
metal
water
of total arsenic from the
between 20 and 300
pesticides
non-ferrous
as
the inhalation of arsenic
by
in
are
Food, beverages and drinking
Daily intake
has been
with As contamination of
averages around 1 |o,g
particles
areas
of
industrial manufactories, exposure may be much
2.5.1.2
poisoning
As
such
industries
application
good hygiene practices
(Abernathy, 2001).
1994). Chronic
levels of arsenic
levels
particles. Nowadays,
equipment
(Chen
higher
to
Food
of arsenic intake, smaller contributions from
source
manufacture and
smelting, pesticide
sources.
water.
in
work
variety of environmental
a
largest
and is most
occasionally reported
ground-
from
to As
exposed
constitutes the
generally
can
in Soils and Plants
ofArsenic
are
(Tamaki
and
Frankenberger,
well below the limit of 50 ^g
where the
groundwater
lies
in As
containing aquifers (see 2.5.2.3).
13
Chapter
2
2.5.1.3
Soil
ingestion
soil and dust
Although arsenic uptake by
source
of arsenic intake in adults, it may be
locations
ingestion
so
in the
unlikely
is
case
of
to be
a
children, particularly in
industrial and hazardous waste sites. In many countries, except
near
Switzerland, guidelines have been developed
to
provide
a
framework for the pre¬
vention, assessment, clean-up, and management of As-contaminated sites.
quoted soil-contamination
the most often
significant
criteria for As
are
In
Europe,
those of the Netherlands.
Toxicokinetics of arsenic
2.5.2
Arsenic concentrations in human blood and urine of about 100 and 15 ng As
respectively,
depending
considered
are
on
normal,
as
environmental exposure.
concentrations
but
Approximately
deposited
also be
higher
As
gastrointestinal
in the
amounts of As
poisoning
chemical
through
in
kidney, lungs, spleen,
absorption.
bones, hair, nails, and skin. Children
direct
depend
in humans
speciation,
tract within 24 hours of
particular
widely
ingested by
5-15% of As
humans is absorbed. Absorbed As is distributed in the liver,
and the wall of the
vary
may
L"1,
Some As may
may be
exposed
to
ingestion
of soil. Effects of acute and chronic
sex, age,
dose, the duration
on
oxidation state
heavy metals, organic arsenic compounds
are
(WHO, 2001).
of exposure and
In contrast to
some
inorganic arsenic
less toxic than the
compounds.
2.5.2.1
Acute arsenic poisoning
Acute arsenic
poisoning
has become
rare.
humans range between 70 and 180 mg,
toxic elements
severe
(Jarup, 1992). Symptoms
diarrhoea
functions.
well
Depending
survivors, bone
encephalopathy
14
as
on
marrow
as
The lethal dose of
indicating
ingested AS2O3
that arsenic is
one
of acute As intoxication
are
disturbances of cardiovascular and
the dose, acute arsenic
poisoning
can
of the most
vomiting
nervous
(Abernathy, 2001).
and
system
lead to death. In
depression, haemolysis, melanosis, polyneuropathy
may be observed
for
and
Chronic arsenic poisoning
2.5.2.2
arsenic
Inorganic
Skin
cancer.
is
carcinogen.
human
a
arsenic increases the risk of
inorganic
cancer
on
various
areas
For internal cancers,
(Abernathy, 2001).
studies in Taiwan have
oesophagus, stomach,
lymphoma
by arsenic
caused
of exposure
beginning
as
in Soils and Plants
ofArsenic
Fundamentals
suggested that
evidence that
was
body, including
latency
a
of 40 years
the
was
Arsenic is
effects
a
are
hours
mutagenic. They
cancers
able to
neutral
in
In contrast to
able
are
a
administration
tube
of the
defects,
but
of
as
well
to
cause
co-mutagen by
teratogenic
foetal
arsenic;
also
may
include
skull, abnormally small jaws, and
organoarsenic compounds,
barriers in many mammalian
placental
cross
of the
in vitro transformation of
exchange, and
after
incomplete development
eyes,
are
observed. Several
al., 1985).
4
result
other skeletal anomalies.
arsenate
et
within
primarily
and feet
(Abernathy, 2001).
repair (Belton
initiated
abnormalities
protruding
palms
known teratogen in several classes of vertebrates. In humans,
are
and skin
bone and prostate,
larynx,
mammalian cells. Studies with bacteria suggest that arsenite is
DNA
of
observed to arise 20 years after the
of the
chromosomal aberrations, sister-chromatid
inhibiting
ingestion
developing bladder, liver, kidney
small intestine, colon, nose,
and leukaemia
is
arsenic may also be related to
inorganic arsenic compounds
Several
There
arsenite and
species (Eisler,
1994).
Chronic arsenic poisoning
2.5.2.3
The first
was
of
case
of
a
Bangladesh
health
large-scale
problem caused by
identified 1968 in Taiwan. Scientific interest
an
which
epidemiological study
concentrations in
blackfoot disease
drinking
as
well
Dhar, 1997). Ever since,
also in
India, Vietnam,
water
as
Inner
clearly showed
and the
cancers
many
was
cases
a
arsenic in
initially attracted by
relationship
occurrence
of arsenic
water
the results
between
high
As
of skin cancer, keratosis,
of the excretory organs
(Chakraborti, 1997;
of arsenic intoxication have been documented
Mongolia, Greece, Hungary, USA, Thailand, Ghana,
Chile, Argentina and Mexico (Smedley and Kinniburgh, 2002).
biggest calamity
drinking
poisoning
takes
place
in
At present, the
Bangladesh.
15
Chapter 2
In the
early 1970s,
resulting
Bangladesh
in
population
in
insufficient
access
had led to
levels of morbidity and
high
installed between 1980 and 1990,
when
mortality.
the wells
were
of As in
large
a
installed, arsenic
was
testing procedures
Although
the release mechanism is not yet
water
concentration of As in the
the
Arsenic in the soil and
be
phytotoxicity
expected,
et al.
drinking
in
include
by
tests
et
water
and
arsenic.
for
appears that the
the reduction of As
bearing
amounts of
organic
conditions due to
high
al., 2001).
plant growth
to relate As
concentrations in soil to
are
that
are
compared (Jacobs
plant growth
growth
of maize
of As
good predictor
a
(1971a) reported that correlation
Sadiq (1986) reported
plant growth.
not
widely differing properties
and water-soluble As than between
in the soil.
problem
fully understood, it
controlled
1980s,
detected. At the time when
did not
total soil As concentrations
when soils with
1970). Woolson
in the late
soil-plant relationship
Many researchers have attempted
growth
as a
(Kränzlin, 2000). Only
reported
were
aquifer (DPHE/BGS/MML, 1999; Hug
Arsenic in the
might
are
reducing
minerals under
oxyhydroxide
matter in
aquifers
areas
were
water from
drinking
pure
cases were
not known
standard
As
to
access
number of wells
therefore
2.6.1
than 4 million tubewells
more
that the
poisoning
number of As
increasing
high concentrations
2.6
With financial support of the
water increased from 37 % to 96 % in the rural
an
rapidly increasing
Diarrhoea accounted for 30 % of
(Black, 1990).
so
a
microbial contamination of surface water,
Bangladesh
UNICEF and the Government of
sanitation for
adequate
severe
death in children under five years
ground
to
was
better between
et
al.,
plant
and total As concentration
was
significantly
correlated
with the water-extractable As but not with the total As concentrations in calcareous
soils. There is
of root
growth
and Arndt
no
plant growth, although
with small amounts of As in solution culture
(1931). Liebig
solution culture
16
evidence that As is essential for
was
et al.
enhanced
by
(1959) reported
1 ppm of arsenate
that
or
was
growth
stimulation
reported by
of lemon
Albert
plants
in
arsenite addition. However, at
Fundamentals
5 ppm of either form of As, both
top and
growth
root
increases have been observed at low levels of As,
such
as
potatoes, rye, and wheat (Jacobs
by
Growth stimulation
by
As:
(Woolson
et
al, 1970; Woolson
2,4-D, stimulate plant growth
as
at
al., 1971a).
growth
exist for
possibilities
Two
et
only temporary, and
occur, is sometimes
growth.
plants
for tolerant
especially
first, stimulation of plant systems by small
pesticides, such
other
always
of top
in the reduction
may result
stimulation
As does not
et
reduced. In addition, small
was
yield
corn,
in Soils and Plants
ofArsenic
amount of
As, since
sub-lethal dose levels
al., 1971b); second, displacement of phosphate ions from the soil by
ions, with the resultant increase of phosphate availability (Jacobs and
arsenate
Keeney, 1970).
Phytotoxicity
2.6.2
relationship
The
availability of
of arsenic
arsenic in the soil.
inorganic compounds
arsenate
>
organic
depends primarily
toxicity
effects
on
and the
plants
as
important
As
kg"1)
to be
factor of influence
that
reported
inorganic
than in
decreases in the
As
secondly
soils become
as
more
on
The
the
on
was
clay (mean
=
phytotoxicity
five times
200 mg As
more
kg"1)
the form and
on
less toxic than
are
following order: arsenite
There is
an
>
of As in soils
phytotoxicity
pH.
increase in As
acid, particularly when the pH drops
Fe- and Al- oxides
are
of
dissolved
only
that soil type is the
inorganic
toxic to
(O'Neill, 1995).
As. In that
plants
soils. Arsenic
in sand
it
study,
(mean
phytotoxicity
is
=
was
40 mg
expected
greater in sandy soils than in other soil types, because sandy soils generally
contain low amounts of Fe and Al oxides and
Arsenic is known to alter and disturb
(Päivöke
for
compounds
arsenic
Sheppard (1992) concluded
literature review,
a
toxicity
soil texture and
below 5 and As sorbents such
From
Organic
compounds (Adriano, 1986).
As
on
phytotoxicity depends
soil As and
between
and
uptake and transport
the most
include leaf
(Liebig, 1965).
frequent sign
wilting,
This is often
followed
of As
toxicity.
by retardation
accompanied by
et
al., 1981).
plants
of nutrients in
Simola, 2001). Disturbance of plant mineral nutrition
yield decrease,
phytotoxicity
clay minerals (Peterson
is the main
cause
Visual symptoms of
of root and shoot
growth
root discoloration and necrosis of leaf
17
Chapter 2
and
tips
in death from
wilting (Woolson
attributed to its
ability
al., 1971a). The phytotoxicity of arsenic is
et
phosphate
substitute for
to
well-aerated soils,
In
chemically
same
mechanism
expected
is
arsenate
orthophosphate,
very similar to
uptake
uptake
as
in
phosphate
a
is
have, however,
soil
a
pH, phosphate
lower
thought
is taken up
arsenate is taken up at low
et
pH
as
as
et
H2PO4" and
H2ASO4" and
al., 1998). Phosphate uptake is
an
to enter the root cell
by
the
variety of organisms (Asher and Reay,
al, 1998). This mechanism
for As than for P
affinity
which is
predominate. Arsenate,
to
1979; Meharg and Macnair, 1994; Schachtman
to
in
catalyzed reactions,
plant (Liebig, 1965).
Mechanism of arsenic
2.6.3
in enzyme
and thus to interfere with the energy
particular to uncouple phosphorylation reactions
status of the
uptake and ultimately resulting
inhibition of root water
margins, indicating
at
(Asher and Reay, 1979).
high pH
at
high pH
as
seems
At low
HPO4 ". Similarly
as
"
HASO4
(Schachtman
consuming process, mediated by
energy
transport proteins (Bieleski, 1973; Bieleski and Ferguson, 1983; Marschner, 1995).
Kinetic studies suggest that at least two
high affinity system (Meharg
low
affinity system has
concentrations. The
of phosphate
primary
human health
is slow and
at
operates
low and
1984).
high
a
The
substrate
only induced under conditions
damages
are <
shoots
to
2 mg As
when As reaches
is
low.
generally
kg"1 (O'Neill,
1995),
are
phytotoxic
levels.
Typical
and crop
As
damage
is
considered critical for
(Peterson et al., 1981).
elements, the degree of As uptake varies widely from species
species (Woolson, 1975).
Uptake
concentrations
18
It
before As reaches concentrations which
As for other trace
were
site of
P, translocation of As
to
usually expected
seeds.
high uptake capacity.
a
deficiency (Clarkson and Lüttge, 1991).
concentrations in aerial parts
or
and Macnair, 1990; Ullrich-Eberius et al.,
high affinity system
The root system is the
Compared
a
phosphate uptake systems exist,
Roots accumulate
increases with
generally
increasing
higher concentrations
than stems, leaves
arsenic concentration in the soil. While As
remain below 1 mg
found to contain up to 3'460 mg As
to
kg"1
fresh
weight
kg"1 (dry weight)
in food crops, grasses
grown
on
spoil material
Fundamentals
ofArsenic
kg"1.
on
with As concentrations up to 26'430 mg As
kg"1
20 mg As
and Peterson,
phosphate
similarity
the
influencing
antagonistic
1936; Woolson
of
phosphate
phytotoxicity
greater, phytotoxicity
stunting occurred
plants.
further fate of As in
have been
Both
at
on
is
wheat
a
was
markedly reduced. However,
concentrations of 10 ppm and
(Rumberg
of crops
wide
Keeney (1970)
found that
amount added. Woolson et al.
significantly
increased
The effect of P
on
As
corn
al., 1960; Tsutsumi, 1983).
corn
yield was
(1973) reported
growth
uptake
et
at low P but
appears to
reduced
and
decrease As
2.6.5
Until
Hyperaccumulation
now
only
few
arsenic. The term
was
will
later
plants
decreased
depend
to
on
soil
on
yield at high P
as
are
both
1973).
of the P
kg"1
soil
levels in soil.
the P demand of the
plant (Otte
well
as
plant
et
plant specific
P additions to soils enhance
have been identified which
was
first used for
plants accumulating
its concentration in the soil
and Kearney,
or
conditions.
of arsenic
hyperaccumulators
generalized
Pteris vittata
depend
P levels in¬
that additions of 100 mg As
Lüttge, 1991). Therefore whether
phytotoxicity
as
by As regardless
al., 1990), and the sensitivity of the plant for As, which
(Clarkson
of 1:1,
higher. Others obtained similar
(Benson, 1953; Woolson
of crops
variety
Hurd-Karrer
at a ratio
culture, several investigators noted reduction in phytotoxicity
Jacobs and
and
function of P concentration. At P/As ratios of 4:1
In soil
variety
a
synergistic
plant growth.
influences
(P/As ratio)
on a
on
main
reported (Hurd-Karren,
results
creased
a
al., 1973). Several nutrient culture studies have demonstrated that
et
that
and arsenate, the presence of P is
uptake by plants
As
on
the amount of P relative to As
or
kg dry weight (Porter
uptake by plants
arsenic
on
uptake and
effects of P
(1936) found
containing
1975).
Due to the chemical
factor
urban soils
found to accumulate up to 3 mg As per
were
Influence of
2.6.4
Grasses
in Soils and Plants
(Reeves
and
(brake fern) accumulated
a
metal
able to
hyperaccumulate
plants accumulating
more
Baker, 2000).
7'234 mg As
are
than 100-fold relative to
Ma et al.
kg"1
Ni and
(2002) found
that
in the fronds. Francesconi
19
Chapter 2
et
al.
(2002) identified another hyperaccumulator, Pityrogramma calomelanos
kg"1 (dry weight)
accumulated up to 8'350 mg As
contained
only
88-310 mg As
a
means
research into this
20
of
topic
removing
is
just
in the fronds while the roots
kg"1.
The bioaccumulation of arsenic
provide
which
by hyperaccumulator
or
even
crop
plants
may
this element from contaminated soils. However,
at the
beginning.
Arsenic Accumulation of Common Plants from
3
Contaminated Soils
P. A.
Gulz, S. K. Gupta, R. Schulin
Submitted for publication in Plant and Soil
Abstract
A pot
experiment
was
concentrations of arsenic
rape and sunflower
calcareous
on
conducted to
(As)
investigate
relationship
the
by maize, English
in soil and its accumulation
Regosol (silty loam)
two different soils: a calcareous
Regosol (sandy loam).
Arsenic
between soluble
(Na2HAs04
7
*
H2O)
was
ryegrass,
and
applied
to
a non-
obtain
As concentrations in the two soils.
comparable soluble
In both soils soluble As
concentrations, extracted with 0.1
correlate better with As concentrations in
concentrations, extracted with 2
M
plants
M
NaNÛ3,
after four month of
were
growth
found to
than total
HNO3. With all four plant species, the relation
between soluble concentration in the soil and As accumulation
non-linear, following
was
Michaelis-Menten kinetics. Similar soluble As concentrations in the two soils did not
result in similar As accumulation
roots to
shoots
was
by plants. Except
significant, resulting
for maize, arsenic transport from
in As concentrations in the leaves and seeds
above the Swiss tolerance limits for fodder and food crops
kg"
,
respectively). Results suggest that
demand, which
crop
plants
are
plant specific,
beside As
(4
mg As
solubility,
P
have to be taken into account to
from As contaminated soils and to
predict the
kg"1 and 0.2 mg As
availability and
P
uptake
of
predict
risk of arsenic
As
entering
into the
food chain.
21
3
Chapter
Introduction
3.1
Large-scale
this element into
promoted
water
an
and crop contaminations
environmental
originating
in
(As)
arsenic
pollution by geogenic
water
pollutant
of
has
Bangladesh
prime
concern.
recently
Widespread
from natural release of arsenic from
aquifer
Mongolia, Greece, Hungary,
rocks have also been identified in India, Vietnam, Inner
USA, Ghana, Chile, Argentina, Thailand and Mexico (Chakraborti, 1997; O'Neill, 1995;
Kinniburgh, 2002).
Smedley
and
Southern
Spain
4'300
to a
km2
containing mine dump contaminated
in 1997, where arsenic
nearby
arable land and parts of the
of As in the
(Woolson
desiccants
1998),
metal
as
of
application
than
park (Rauret, 1999)
led
of soils and to renewed interest into the
pollution
smelting, coal combustion and glass
containing fertilizers, pesticides,
As
al., 1971a) and growth promoters
et
more
Beside natural and accidental arsenic
soil-plant system.
(Smith,
Donana National
pollution
soils, also industrial activities such
manufacture
in the Aznalcöllar Mine in
addition, the accident
re-evaluation of anthropogenic As
dynamics
of
In
for
poultry
pigs (Christen,
and
2001) have led to wide-spread As pollution of soils.
Arsenic does not
concentrations it
only play
can
an
essential role in animal nutrition
also be beneficial for
1970; Woolson
et
et
Yield increases due to small
al., 1998; Gulz, 1999; Gulz and Gupta, 2000; Jacobs
al, 1971b;
concentration As becomes
eventually
very toxic
the root system. Because arsenic is not
plant parts
already
even
are
low in As
(<
at concentrations that do not
failure is
animal
generally
or
assumed to
usually
human health
for all
2 mg
kg"1).
occur
a
health risk for
may accumulate
high
Peterson et
22
consumers
or
human
even
kg"1 (Adriano,
1986).
primarily
at soil
For
occurs
to
highly
primarily
shoots, edible
toxic to
plants
health, crop damage
are
of
concern
or
for
al., 1981). Jacobs and Keeney (1970)
of crops grown
levels of arsenic
level of 5 to 40 mg As
Because As is
before As levels in shoots
concluded that arsenic contamination of soils
presenting
al,
plants, causing chlorosis,
readily translocated
yet affect animal
(O'Neill, 1995;
et
Thornton, 1985). However, with increasing
Xu and
necrosis, inhibition of growth and finally death. Uptake of As by plants
through
at very low
for corn, potatoes, rye, and wheat
especially
additions of As have been observed
(Carbonell-Barrachina
plant growth.
although
affects
on
productivity,
these soils. But
concentrations
near
the
rather than
some
plants
background
instance, Bhumbla and Keefer (1994)
Uptake of Common Crop
Arsenic
found arsenic concentrations of 6 to 12 mg As
soil
on
grass grown
concentrations up to 149 mg
kg"1 (fresh weight)
kg"1.
25 to 50 mg As
containing
kg"1
Plants from Contaminated Soils
in rice straw at
in alfalfa and pasture
(1983)
Tsutsumi
found arsenic
arsenic concentration of 312 mg
an
kg"1
in soil.
Although
Ernst
(1994), Sheppard (1992)
composition
of soils
As
that As
was more
found that
on
inorganic
As
kg"1) than on clay (mean
=
not
availability
five times
than
kg"1)
on a
toxic to
plants
soils at the
expected
is
application
are
rate
soluble As concentration is lower in
in
species
are
agricultural
predominant
As
is sorbed
calcium oxides, but this
on
same
to be
Although Woolson
et
logarithm of total
uptake by
et
sand
clay minerals
was
Few studies
reported
As
was
organic
and
a
sandy soils.
than in
As
given
In acid
In alkaline
soils,
arsenate
pH
on
a
significant
growth reduction in
was
linear correlation between
corn,
water-soluble As
total soil arsenic.
was
Sadiq (1986) found
correlated with the water-extractable As, but not with
of
focussing
applied
on
arsenic
As to soils have
solubility.
uptake by different plant species. Wauchope (1983)
that As accumulation in
concentrations and
Arsenic
less intense than that at lower
without consideration of its
compared
40 mg As
of arsenate, which is the
uptake by plants, however, only the effects of total doses
compared, mostly
=
al., 1971a).
plant growth than
maize
loamy
the total As concentration in calcareous soils. In most studies
been
(mean
application.
rate of
(Pongratz, 1998).
(1971b) observed
soil arsenic and
better correlated with
that As
al.
soils
(1998)
greater in sandy soils than in
primary sorbents
adsorption is
(Woolson
iron and aluminum oxides
the
Lakeland loamy
strong sorbents of As (Sadiq, 1997). Therefore, for
soils, iron and aluminum oxides
by
on
crops
plants.
of As to
silt loam soil. Smith et al.
other soils, because of their low contents of Fe and Al oxides,
matter, which
between
Keeney (1970) reported that
loam. Jacobs and
more
phytotoxicity
vegetable
toxic to
sandy
200 mg As
and hence
uptake by plants
was
to corn on a
was
(1985), the relationship
factors that govern the
Hagerstown silty clay
phytotoxic
g. Otte and
e.
is still not well understood. Texture and chemical
important
are
(1971b) reported
sand and lowest
and Xu and Thornton
plant uptake
arsenic in soil and
Woolson
by plants,
many researchers have studied arsenic accumulation
plant
similar in
shoots
plants
was
proportional
of different
species
to
soluble soil As
grown in the
same
23
Chapter 3
may be
different between
quite
and Inskeep,
phosphate (Darland
anions
strongly compete
surface
specific binding by
surfaces.
not
the
only
unspecific
in
versa.
binding of
from soil
complexation
anion
e.g.
on
in soils is
arsenate
similarity, these
Due to their chemical
1997).
Increasing phosphate concentrations, thus,
arsenate and vice
uptake
plant species.
primary importance influencing
A factor of
found that arsenic
(1994)
solution. On the other hand, Otte and Ernst
but also in
exchange reactions,
iron and aluminium
are
expected
hydroxides
to cause release
plant
to
by the
roots
activity and
and Macnair
Meharg
in
availability
P
arsenate and
(1994)
phosphate
mechanism. P nutrition status, which
same
soil
the
plants
may thus be
accumulation and
in
toxicity
The similarities in soil and
demand of crop
(1999)
plants
plant chemistry
may be
an
important
Gupta (2000) found
and Gulz and
in the shoots of
plants reported
English
wheat, plants which
in
known for
a
respectively.
when these
In the
plants
For this purpose,
were
present study,
are
a
of arsenate and
grown at
we
hydroponic system
P
artificially spiked with
As
to
on
As
In
that P
fact, Gulz
that As accumulation
rape, tobacco and
demand, exceeded significantly the
plants (4
investigated
was
results
uptake.
soybean, sunflower,
and 0.2 mg As
kg"1 ),
how far these results also
apply
mg As
comparable phytoavailable
pot experiment
As
P status of
phosphate suggest
factor promoting As
high
Swiss tolerance value for fodder and food
uptake
in the literature.
ryegrass, pea, maize,
are
P
influence
apparently contradictory
for
a reason
roots.
taken up into
regulates
strongly
therefore
may
are
accumulation, independently of the availability of As itself. Differences in
soils and
of
between As and P is not limited to soil matrix
Competition
sites, but also affects As binding by living organisms, in particular plant
According
two
kg"1
As concentrations in soils.
carried out with two different soils which
achieve
defined
levels
of
soluble
As
concentrations.
Beside the
crop
on
relationship between
plants,
uptake
the distribution of accumulated As between different
plant growth,
as
well
as
by plants were investigated.
24
soluble As concentrations and
the influence of As
on
of these
plant parts,
phosphate mobility
common
the effects
in soil and
uptake
Arsenic
3.2
3.2.1
Uptake of Common Crop
Material and methods
Soils
Two different soil materials
Regosol (silty loam)
manufacture
were
sieved to
and mixed
cm
uncontaminated calcareous
brass smelter and
a
to the
greenhouse
non-calcareous
by arsenic emissions
pits by
they
where
were
use
of
a
glass
properties.
of
a
The
spade, filled
dried under
a
cover,
homogeneously.
properties
experiment
Table 3.1 Selected soil
the
a
1999 excavated from
early April
transported
1
of
an
than four decades. Table 1 lists selected soil
in PE boxes and
<
surrounding
study:
which had been contaminated
over more
collected in
used in this
were
from the
Regosol (sandy loam),
soils
Plants from Contaminated Soils
of the
silty loam and
the
loam
Soil characteristics
Silty
Soil
Calcareous
type
sandy
loam at the start of
Sandy loam
Regos
Regosol
pH (1:2.5 H20)
7.4
7.1
CaC03 (%)
13.4
1.5
Corg(%)
4.2
1.9
Clay(%)
32
18
50
2
18
59
25.9
17.8
Cu
503
22
Pb
46
38
Zn
604
67
Silt
(%)
Sand
(%)
CECOneqlOOg"1)
Total As
(2
M
HN03, [mg
kg"1]
25
Chapter
3
As addition
3.2.2
silty
The
loam had
initially
a
kg-1.
concentration of 0.02 mg
225 and 255 mg As
control treatment without any As addition
sandy loam
concentration in the
concentration
H2O)
was
was
plastic pots (0
29
7
s
SS
0
B
«
*
26
soluble As
kg"1 (Na2HAs04
*
7
and
spiking.
were
designated
as
As_6.9, according
As_0, As_l.l, As_2.8,
to the
target values of
The amount of As necessary to obtain these
determined in
equilibrate
kg dry
are
preliminary
batch
for four weeks before
experiments.
they
were
After
filled into
soil per pot.
resulting
total and soluble As and P concentrations
[mg kg" ]
Total As**
Soluble As***
Soluble P***
As_0
0
3
0.02
1.45
As_l.l
110
93
1.10
2.02
As_2.8
180
165
2.75
2.25
As_4.7
225
210
4.68
2.67
As_7.1
255
240
7.12
3.23
As 2.8
0
189
2.83
3.22
As 4.2
25
212
4.12
3.51
As_6.9
60
240
6.89
4.17
as
extracted
***
corresponding
Na2HAs04
by 2 M HNO3 after equilibration before seeding
extracted by 0.1 M NaN03 after equilibration before seeding
added
**
the
As addition*
As treatment
0
A
in the soils
Table 3.2 As addition and
S
H20).
resulting total and soluble arsenic concentrations
left to
cm),
7
*
kg"1
The added
soluble As concentrations
were
soluble As
kg"1, respectively.
soluble As concentrations after
soils
kg"1 (Na2HAs04
The addition of 25 and 60 mg As
As_4.7 and As_7.1, As_2.8, As_4.2
spiking,
a
also included. The initial total As
kg-1,
189 mg
listed in Table 3.2. The As treatments
>>
was
raised the soluble concentration to 4.2 and 6.9 mg
arsenic amounts and the
are
kg"1.
2.8 mg
and
Soluble As concentrations of 1.1, 2.8,4.7 and 7.1 mg
adjusted by adding 110, 180,
were
kg-1
total As concentration of 3 mg
Arsenic
all soils
seeding
Prior to
kg"1
kg"1
(50%
K
seedlings
was
adjusted daily.
no
runs
130 mg
K2S04),
as
was
kg"1
carried out in
triplicates. Lolium
in
kg"1
130 mg
by adding
a
N
and Helianthus
(rape)
annuus
perenne
water-holding capacity
of the soil
and 40 mg
with climatic
(English Ryegrass)
was
(maize, Magister),
mays
San
180
(Ca(H2P04)2,
(NH4NO3)
Luca) the number of
Water content
plants, respectively.
reduced to one, six and two
The
(sunflower,
P
greenhouse
pot. One week after germination of Zea
5 g per
Brassica napus
fertilized
experiment
The
control. Each treatment
as
were
KCl and 50%
as
Mg (MgS04).
seed
Plants from Contaminated Soils
Plant material and cultivation
3.2.3
mg
Uptake of Common Crop
was never
was
exceeded, therefore
leaching occurred.
Plants
Aerial
were
separated
early May
seeded in
plant parts
into
and
sampling
Plant and soil
3.2.4
were
cut
analysis
and harvested after four month in
approximately
one
early September.
centimeter above soil surface and
shoots, leaves and seeds, including the
cop for maize and
corn
thalamus for sunflower. To simulate field conditions, Lolium perenne
firstly
and
after 10 weeks and
secondly
at
carefully washed with several
the end of the
from the root surface. Plant parts
constant
weight
samples
of 0.5 g
obtained. Dried
were
(30 %). NANOpure
chemical
analysis.
Soil
samples
sieve. Soil
Soil
were
water was
homogenized,
analysis
were
carried out
concentrations with
samples
were
a
analyzed
were
were
in
a
added to obtain
according
was
remove
in
a
an
to
aliquot of
2 M HNO3
(0.1
M
out
all soil
until
oven
a
2
mm
relating
(1:2.5).
(65 %),
NaNÛ3).
and 3
25 ml for
through
the Swiss Ordinance
boiling
dug
(65 %)
measured in NANOpure water
extracted with
twice,
titanium mill. Plant
mixture of 5 ml HNO3
week neutral salt solution
for As
ground
cut
were
dried at 60 °C in the
dried at 40 °C for 72 h and sieved
Impact (VBBo, 1998). Soil pH
total metal concentrations
were
plants
microwave-digested
ml H2O2
Roots
rinses of deionizised water to
particles
was
experiment.
was
to
The
the soluble
Plant and soil
by AAS-GF-HG (Perkin Elmer) and for P, Cu, Pb and
ZnbylCP-AES(Varian).
27
Chapter 3
Statistical
3.2.5
analysis
All statistical
was
Significance
distribution.
analysis
statistical
analysis
was
performed
on
of differences
carried out
log-transformed
tested
was
using Systat
10
data to obtain normal
by analysis
of variance. All
(SPSS, 2000).
Results
3.3
Soluble As and P concentrations and
3.3.1
solubility
Arsenic
slightly higher
was
at same
total As concentrations in the
loam. About 10 % of added As
sandy
loam than in the
pH
could not been extracted
was
by
silty
adsorbed irreversibly
2 M HNO3. No
at
significant
the end of the
experiment and
changes
found between initial and final soluble As concentrations in the two soils
were
(Figure 3.1).
In both
the
the
soils, arsenic addition led to
P
more
solubilized
was
silty
than in the
sandy
concentrations of soluble P
control treatments of the
experiment
an
loam.
were
silty
Significant
found in the
the
In the
experiment,
The initial soil
While
(7.4)
on
with
sandy
i.e.
pH
silty
no
was
added
stronger in
differences between initial and final
silty
loam
(results
not
shown).
In the
during the
was
loam
not
over
affected
the
for
an
P concentrations
by
were
constant
throughout
occurred.
As addition
growth period
(results
not
shown). However,
in most As treatments
it
(Figure 3.3).
maize, English ryegrass and sunflower decreased the initial pH
initial
maize,
As treatment soluble P rather tended to
B. napus reduced soluble P in all treatments
significant changes
increasing soluble As,
loam with
significant
28
highest
sandy loam, soluble
significantly
the
was
loam soluble P concentrations decreased
during the experiment. Only
decreased
As
about 75 % of the initial P concentration. Addition of As reduced this
to
significantly.
more
This P mobilisation effect
(Figure 3.2).
"immobilization" effect, and in the
increase
increase of soluble P. The
pH
rape did not influence the
of 7.1, all
rape and
plants raised the pH,
English ryegrass.
pH significantly.
but this increase
On the
was
only
Arsenic
Uptake of Common Crop
Plants from Contaminated Soils
O)
E
o
'&
ra
c
a>
o
c
o
o
id
<
n
o
CO
As_0 As_1.1 As_2.8 As_4.7 As_7.1 As_2.8 As_4.1 As_6.9
As treatment level
Figure
3.1 Mean and standard
growth
error
of soluble As concentrations
[mg
kg"1]
after
of Zea mays, Lolium perenne, Brassica napus and Helianthus
annuus, n=3.
U)
D)
E
(^
c
o
<D
U
c
o
o
Q.
SI
3
o
CO
As_0
As_1.1 As_2.8 As_4.7 As_7.1 As_2.8 As_4.1 As_6.9
As treatment level
Figure
3.2 Mean and standard
growth
error
of soluble P concentrations
[mg kg" ]
after
of Zea mays, Lolium perenne, Brassica napus and Helianthus
annuus, n=3.
29
Chapter 3
6,4
J
1
'
'
'
'
'
'
'
As_1.1 As_2.8 As_4.7 As_7.1 As_2.8 As_4.1 As_6.9
As_0
As treatment level
pH after growth
Mean of soil
Figure 3.3
of Zea mays, Lolium perenne, Brassica
napus and Helianthus annuus, n=3.
As distribution and concentrations in
3.3.2
Arsenic
accumulation by maize,
rape,
plants
English
affected
ryegrass
by
and
As treatment
sunflower varied
plant species, plant parts and soils (Table 3.3).
considerably
between
responded
to
increasing
the roots.
Figure
soluble As concentration with
3.4 shows
a
close
increasing
relationship between
All
plants
As accumulation in
As concentration in roots
and soluble As concentration in soil.
On the
silty
loam As concentrations in roots of Zea mays increased
about 565 mg
kg"1
as
soluble soil concentrations of about 4.2 mg
were
H. annuus,
30
151 mg
to
kg"1.
In
the soluble As concentration increased to about 7.6 mg
uptake
B. napus, L. perenne and H. annuus, however As
roots
monotonously
kg"1
kg"1.
for B. napus, 288 mg
respectively.
into the roots levelled off at
The maximum As concentrations in
kg"1
for L. perenne and 339 mg
kg"1
for
Arsenic
Uptake of Common Crop
Table 3.3 Means and standard
errors
Plants from Contaminated Soils
of As concentrations
[mg
kg-1]
in different
plant
of variance and post hoc pair
organs. Letters indicate results from analysis
wise comparisons of As concentrations of plant species in different As
treatment
levels within
column with
a
letter in
one
soil. Arsenic concentrations within the
common
are
not
significantly
different at
same
p<0.05,
n.d.=not detectable, n=3, Lolium perenne: stems=first cut, leaves=second cut.
laut
Soil
^
I
«
E
s
As treatment
Roots
Stems
Leaves
Seeds
As_0
As_l.l
n.d.
n.d.
n.d.
n.d.
101.8±5.9a
l.l±0.2a
2.9±0.9a
n.d.
As_2.8
257.0±36.1b
2.9±0.5a
n.d.
As_4.7
As_7.1
420.3±12.0C
1.3+0. lab
1.7±0.3bc
n.d.
565.5±27.3d 2.5±0.3C
4.3±1.0b
5.4±2.2b
As_2.8
As_4.1
As_6.9
150.5±6.7e
7.0±0.4d
9.0±1.7C
0.2±0.01a
n.d.
«8
>*
-o
C
es
ce
_
S
CS
o
—
As_0
As_l.l
su
SI
1
>>
a
*
S
«
s
Ci,
SJ
^
>*
_
-d
S
C
es
o
es
>>
E
"S .S
s:
212.1±8.7e
9.6+0.76
8.8±0.6C
0.2+0.023
276.7±22.4g
8.9±0.3e
10.7±0.4C
0.1+0.013
n.d
148.9±4.7a
n.d
9.7±l.la
n.d
8.3+0.23
10.8±0.5ab
10.4±0.8b
As_7.1
240.1±18.5b 12.2±1.9a
259.6±9.7b 14.2±4.7ab
288.3±ll.lc 18.9±2.9b
As_2.8
154.6±2.3d
13.6±1.7a
7.9±0.8a
As_4.1
206.7±2.0e
As_6.9
254.6±6.8f
16.8±1.2b
15.7±2.0b
8.5±1.2ab
10.8±0.6b
As_2.8
As_4.7
As_0
As_l.l
As_2.8
n.d.
n.d.
n.d.
1.3±0.1a
8.2±0.7a
14.5±1.2a
13.6±1.0b
17.7±1.5bc
20.3+1.lb 2.3±0.2b
23.7±2.3bc 2.8±0.1b
20.8±0.8C
25.8+0.3c
199.4±19.1c
13.1±1.8b
14.3±2.2bc
27.9±2.0C
261.0±27.1d
19.6±2.2C
63.3±14.4a
As_7.1
136.4+5.8b
150.7±27.5b
151.3±48.7b
As_2.8
140.2±4.6b
As_4.7
n.d.
15.8+1.0C
3.4±0.1c
?»
»5
"«
S
es
E
es
o
As_4.1
As_6.9
As_0
As_l.l
<3
a»
>»
E
S
es
»
2
05
a:
"S
«
>?
"S
«
es
~
E
5
©
203.5± 0.5a
n.d.
8.5+0.53
As_4.7
288.5±19.1b 14.2±1.3b
337.2±45.0bc 15.1±0.5b
As_7.1
339.3±34.7C
As_2.8
As_4.1
408.8±24.4d 29.1±0.9d
457.9±51.0d 28.5±0.8d
As 6.9
600.8±10.0e
As_2.8
s:
1
n.d.
19.6±1.4C
32.6±2.0e
22.0+0.8b 3.5+0.3c
4.5±0.2cd
37.3+2.6d 4.3±0.1d
n.d.
n.d.
33.5±0.9a 0.5±0.01b
37.7+0.8b 0.4±0.04b
39.2±1.7bc 0.5±0.02b
41.8±2.3C 0.6±0.03b
107.9+3.7d
99.2±2.2d
97.1±2.5d
1.0±0.02c
l.l±0.01c
1.2±0.01c
31
Chapter
3
700
(0
-
Z. mays
r2
=
0.97
H00
—*
L. perenne
r2
=
0.96
500
.-• B. napus
r2
=
0.91
r2
=
0.97
**
o
o
k.
c
1—1
r-
J£
—à.
H.
annuus
silty loam
400
c
300
o
4-i
m
i_
200
c
a>
u
c
100
o
u
(A
<
0
4
3
2
[mg
Soluble As concentration
3.4 Soluble As concentrations
Figure
in the roots
[mg
kg"1]
of maize,
bars denote the standard
model
</)
curves
L.
700
600
c
!"!
"o>
500
.*
rn
F
in the
kg'1]
silty loam versus As concentrations
ryegrass, rape and sunflower. Error
Curves represent best-fit Michaelis-Menten
English
error.
[3.1].
-*Z.mays
1^
=
0.99
-*L. perenne
1^
=
0.94
r+B. napus
r2
=
0.98
-±H.
r2
=
0.99
+*
o
o
[mg kg" ]
6
5
annuus
sandy
loam
400
bml
C
o
300
+-I
m
k.
c
<1>
A){)
Ü
c
o
o
100
If)
<
n
2
4
3
Soluble As concentration
Figure
[mg
sunflower. Error bars denote the standard
Michaelis-Menten model
kg'1]
[mg kg" ] in the sandy
[mg kg"1] of maize, English
3.5 Soluble As concentrations
concentrations in the roots
32
6
5
curves
[3.1].
error.
loam
versus
As
ryegrass, rape and
Curves represent best-fit
Arsenic
The non-linear
on
the
Uptake of Common Crop Plants from Contaminated Soils
relationships
silty loam are well described by "Michaelis-Menten" kinetics,
ASplant
where
Aspiant
(max)
=
ASplant (max)
affinity of plants
uptake
of nutrients
In the
sandy loam,
M
(0.1
NaNÛ3) and
k
a
was
only reached
approximately
twice
[3.1]
Assol)]
plant tissue, Assoi
parameter characterizing
typical
pattern
same
and B. napus
much As
as
as
(Figure
and root
3.6 and
uptake
3.7).
was
linear but weaker
For the
relationships
were
sandy
silty
almost identical.
the other
to root
species.
uptake
silty loam, the correlation between
still strong, but for the
in the
(Figure 3.5). Arsenic
As treatment, accumulation of sunflower roots reached 600 mg As
more
for the
into the cells.
with L. perenne
as
roots
i.e.:
A Michaelis-Menten kinetic is
roots of Z mays, L. perenne
by
*
k
As accumulation in roots followed the
Total soil As showed
As
Assol) / ( 1+
*
through the plasma membrane
Sunflower accumulated
highest
[(k
uptake of As.
for
loam. However, saturation
accumulation
*
is the calculated maximum As concentration in
the soluble As fraction in the soil
the
uptake by
between soluble As concentrations and
kg"
At the
.
than soluble
total As in soil
loam the correlation
was
much
weaker than for the non-linear Michaelis-Menten kinetics between soluble As and
root
uptake.
A
comparison
of
corresponding
of Z. mays and L. perenne accumulated
sandy loam, while
the
opposite
was
As treatment levels shows that the roots
more
As from the
observed for H
loam 97 %, 90 %, 80 % and 78 % of As taken up
and sunflower
were
was
located in the roots. For the
slightly lower,
but the differences
were
annuus
and B. napus. In the
the
soils.
Increasing soluble
On the
sandy loam,
kg"1, by
ryegrass, rape
corresponding values
considerably
As concentrations in the
increased As concentrations in the stems of Z. mays, B. napus and H
Maize accumulated 2.5 mg As
silty
statistically significant.
Arsenic concentrations in stems, leaves, and seeds differed
plant species and
loam than from the
by maize, English
sandy loam,
not
silty
silty
annuus
between
loam led to
(Table 3.2).
far the lowest As concentrations in the stems.
As concentrations in maize stems
were
four times
higher. English
of As in all As treatment levels like
ryegrass and rape accumulated similar amounts
on
the
silty
loam.
Only sunflower increased
As accumulation
on
the
sandy loam.
33
Chapter 3
700
--Z. mays
(ft
•*-•
o
600
c
.r-1
500
-*rL. perenne
-
ß. napus
-±
H.
O)
.*
F
annuus
r2
=
0.94
r2
=
0.89
r2
=
0.89
r2
=
0.90
silty
loam
*
400
k»j
c
o
^5
300
re
k.
+>
c
200
o
c
o
u
100
(A
<
100
50
Total As concentration
Figure
Total
3.6
As
concentrations
concentrations in the roots
[mg
(0
-*Z.mays
o
O
i_
600
c
,__,
O)
500
.*
O)
F
c
o
-^L. perenne
-•-B. napus
rH.
kg'1]
error.
Lines represent best fit
regressions.
700
+»
300
[mg kg"1] in the silty loam versus As
[mg kg"1] of maize, English ryegrass, rape and
sunflower. Error bars denote the standard
of linear
250
200
150
annuus
^
=
0.67
r2
=
0.66
r2
=
0.63
r2
=
0.90
sandy
loam
*—
400
300
4-*
(0
i-
c
CD
o
c
o
200
100
o
(0
<
0
50
100
Total As concentration
Figure
3.7
Total
As
concentrations
concentrations in the roots
[mg
34
regressions.
300
kg"1]
[mg kg'1] in the sandy loam versus
[mg kg"1] of maize, English ryegrass, rape
sunflower. Error bars denote the standard
of linear
250
200
150
error.
As
and
Lines represent best fit
Arsenic
Menten kinetics
on
silty
the
As treatments caused
increasing
Like in the stems,
as
As
uptake by
loam from 33 mg As
around 100 mg As
increasing
The accumulation followed the
plants.
the leaves of all
Uptake of Common Crop Plants from Contaminated Soils
kg"1
[3.1].
roots
kg"1
As concentrations in
type of Michaelis-
same
ranged
Arsenic in leaves of sunflower
in all As treatment levels
on
As_7.1 and
in
kg"
in Asl. 1 and 42 mg As
was
sandy loam. Also,
the
As
accumulation of rape increased with As treatment level and the maximal As
concentrations in the leaves
were
26 mg
kg"1
on
the
silty
loam. The first cut of English ryegrass contained
sandy
of As than the second. This effect
in the leaves of maize increased from 2.9 mg
sandy loam, concentrations
On the
seeds
on
on
the
were
silty loam,
sandy loam (Table 3.3).
the
in
in maize leaves
Arsenic concentrations of the seeds
in the seeds of maize
kg"1
loam. Arsenic
on
As_l.l
were
the
to
twice
5.4 mg
as
low. While
kg"1
mg As
kg"1
in
As_6.9 (silty loam).
were
same
observed for sunflower, but the maximal As concentrations
kg"1
in
As_7.1
and
As_7.1.
no
As
was
found
were
found in the
in
As_7.1 (silty
kg"
accumulation pattern
were
only 0.6
was
and 1.2 mg As
As_6.9, respectively.
Effects of As addition
3.3.3
in
accumulated in the
As concentrations
The
kg"1
high.
seeds of rape, where As concentrations reached values of 3.4 mg As
sand) and 4.3
the
sandy
about 0.2 mg As
highest
on
concentrations
generally very
The
kg"1
slightly higher
pronounced
was more
loam and 37 mg
on
yield
and As_7.1.
Chlorosis, necrosis, and delayed flowering occurred in As_2.8, As_4.7
On the
silty
loam As inhibited
The most
(Table 3.4).
severe
growth
the lowest As treatment level
seeds
were
of 2 mg
growth
in all four
reduction
(As_l.l),
in the treatments from
was
in all
plant parts
observed in Z. mays. Already
at
total biomass of roots, stems, leaves and
40 % lower than in the controls
kg"1
plant species and
As_l.l
(As_0).
to
As soluble As increased in steps
As_7.1, biomass decreased by
a
factor
H.
of around 2 from treatment to treatment. Growth of L. perenne, B. napus and
annuus was
less
strongly affected by As treatments.
35
On
LO
***
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Zea mays
sandy
Lolium perenne
Brassica napus
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sandy
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Arsenic
reduction
between As treatment and root,
relationship
While the
was
Uptake of Common Crop Plants from Contaminated Soils
similar for each
and leaf biomass
stem
reduction of seed biomass
plant species,
was more
pronounced.
sandy
On the
loam As treatments reduced
loam. Necrosis, chlorosis, and
delayed flowering
were
less than
observed
only
toxicity symptoms. ANOVA analysis (Table 3.4) showed that yield
considerably higher
on
the
sandy
loam than
soils, only biomass of seeds
3.4
larger
was
on
the
sandy
general
in
was
for rape.
between the
production
loam.
Discussion
plant parts
As accumulation and distribution in different
3.4.1
In contrast to the
findings of Sadiq (1986),
between soluble As and
Since
Sadiq (1986).
and
independent,
plant uptake,
some
relationship
in
(1971b),
typical
for nutrient
been found for As and P
soluble
and
the
relationship
to the
uptake
uptake by
proportional
to
conclusions of
of Woolson
findings
concentrations
a
between soluble As and
are
not
which is mediated
many authors
et
al., 1994a).
was
the available As concentration in the soil. Maize,
same
in
uptake
general
English
amounts of As at the
concentrations in the two soils. The variations in As
has
al., 2002; Meharg and
Wauchope (1983) arsenic uptake
the
rape and sunflower did not accumulate
uptake
by transport proteins and
(Abedin
et
plant uptake
This
Michaelis-Menten kinetics.
Macnair, 1990; Meharg and Macnair, 1991; Meharg
Contrary
relationship
obtained for the
which confirms the
total
(calcareous) silty
for the
expected.
general non-linear, following
kinetics is
were
relationship
rather close linear
between total As concentrations in the soil and As
concentrations in the roots should be
In contrast to Woolson
a
plant uptake
higher correlation coefficients
loam. But still
(1971b)
found
we
between total As concentrations in soil and
was
silty
for maize, rape
silty loam, except
the
on
Sunflower did not show great differences in leaf and stem
two
the
on
the mentioned
ryegrass did not show any of
As_6.9. English
and sunflower in
plant growth much
between
not
ryegrass,
same
soluble
plant species
37
Chapter 3
explained by different
may be
silty loam,
in the two soils. In the
plants and different
P demands of the
P
was
probably
by reduced growth of English ryegrass and maize
to
sandy loam).
the
the
was
Due
also indicated
ryegrass and sunflower.
in
our
accumulation
results from
English
shortage
The
significantly
on
Marschner
a
widespread
quality
weight basis (FMV, 1995).
stems
and leaves
separated
and
was
not
confirmed in
This limit
was
As_7.1, though
surpassed
This value
were
FIV
was
first
(1998),
our
plants by
exceeded
kg"1,
cutting
cutting
kg"1.
clearly exceeded by
in this
that maize and
more
limits
so
plant uptake
experiment.
The maximum As
Swiss law is 4 mg
on
the
silty
they could
kg"1
Only
be used
the cobs of Z
as
forage
was
crops
higher
probably
the Swiss ordinance
production.
a
As
due to
a
cuttings
relating
on
kg"1.
the seeds of both B. napus and H. annuus, which
In contrast to other
experiment accumulated relatively high
edible parts and would thus pose
dry
sandy loam, however,
than of the second. However, both
to
on a
loam in the leaves of
of L. perenne contained
According
of As
the maximum concentration of As in oils is 0.2 mg As
therefore not safe for oil
investigated
confirm the
known to suffer less from P
are
both soils than the second. This
the As limit of 4 mg
quality
As
the activation of P
2000)
the limit in all As treatment levels.
on
longer growth period of the
food
between
As and suffered
more
not in the stems. On the
from straw. The first
amounts in all treatments
surpassed
English
root response to
experiment
Gulz and Gupta,
deficiency, accumulated
4 mg As
mays did not exceed the limit of
when
shortage
plants, maize increased
The results of this pot
concentration tolerated in crops and fodder
As_4.7
P
species.
levels of crop
Z mays in
loam. P
sandy
silty loam, supposedly through
deficiency.
experiment,
(1995). Responses differed
than rape and sunflower, which
than other
the start of the
wide-spread assumption (e.g. Lepp, 1981) that toxicity
to safe
38
is
the other
hydroponic systems (Gulz, 1999;
toxicity
at
(compared
decrease of pH in pots with maize,
by the
to
the
ryegrass, grown under P
from As
applied
loam than in the
In contrast to
experiments.
in response to P
uptake
in the control treatment
higher sorption capacity, soluble
its
silty
limiting growth factor, indicated
a
Rhizosphere acidification
phosphorus deficiency according
plants
was
to
much lower in the
were
silty loam was
in the
fertilization, which
for both soils.
same
concentrations
P
P availabilities
studies, all plants
As concentrations in their
risk for animal and human health.
Arsenic
Effects of As addition
3.4.2
Our results
concerning the
English
rape,
on
the
only
silty
implying
in the
at
plants
inhibition
decreased with
ryegrass
plant growth
ryegrass and sunflower
particular growth
yield
on
in contrast to most
are
usually found
have
(Peterson
treatment levels. On the
comparable
or even
that As concentrations in
experiment. Supposedly,
to cause
were
As in all
where
higher phytotoxicity,
silty loam,
On the
plants, although
in
sandy loam, yield was higher than
As concentrations in the
higher
plants
existing studies
al., 1981; Smith, 1998).
et
increasing levels of soluble
higher As
loam at
uptake and biomass production of maize,
interaction of As
As concentrations in
higher
in
Soils
Uptake of Common Crop Plants from Contaminated
not the
only
plant parts,
governing growth
factor
the better P nutrition status reduced the
toxicity of As
of growth.
present in the plants and thus also the inhibition
Although
the
silty
yield
two
loam than from the
were
in all
means
the
that in
higher
P
sandy loam
plants smaller
on
the
at the same
silty
our
availability
in the
and suggest that this factor
P nutrition
sunflower and rape
experiment
sandy
requires
loam than
more
soluble As concentration in soil,
loam. This result does not agree with
(1970). Assuming different
Jacobs and Keeney
is
i.e. B. napus and H annuus, accumulated less As from
plant species,
as
the
were more
negatively by
investigation
responsible factor,
positively
the
affected by
higher
As
uptake
in order to understand As
uptake by plants.
Acknowledgements
We
gratefully acknowledge
O.
Bachmann for their continuous
This
project
(Grants
was
Wyss,
help
B.
Schüpbach,
and support in the
financially supported by
No. 21-52758.97 and
R. Hort, Ch. Dähler and H.J.
greenhouse
and laboratory.
the Swiss National Science Foundation
20-61860.00).
39
Seite Leer /
Blank leaf
Effects of Phosphate
4
on
Availability
Arsenic
in Soils and
Growth of Sunflower
P. A.
Gulz, S. K. Gupta, R. Schulin
Preparedfor publication
in the Journal
ofEnvironmental Quality
Abstract
Using
on
batch and pot
experiments,
we
investigated
soluble As concentrations in the soil
sunflower
(Helianthus annuus L.).
non-calcareous
were
Regosol (sandy loam)
compared. Phosphate
was
soils,
at
of the form in which P
a
a
as
on
calcareous
As
phosphate
addition
uptake and growth
Regosol (silty loam)
and
in three different chemical forms
was
lower in the
high binding capacity
addition increased As
rate
was
of 56 mg P
kg"1
soil.
the addition of phosphate increased
applied,
especially
the
at low
silty loam than
of the soil reduced
as
well
as
P
in the
uptake
only
a
between P and As.
on
that the
Phosphate
into the roots and shoots of the
plants,
soluble As concentrations. Increased P accumulation did not protect
plants against yield reduction, especially
not
sandy loam, indicating
competition
on
arsenic contaminated soils rather increased As
was
a
(N^HPOV
The P effect
soluble P and As concentrations in the two soils to different extents.
soluble As
of
with various initial soluble As concentrations
applied
NaH2P04, NH4H2PO4, (NH4)2HP04)
Independent
Two
well
as
the effects of
the
sandy loam.
phytotoxicity
P addition to the
than decreased it and
function of soluble As and P concentrations in the soil.
41
Chapter 4
Introduction
4.1
Due to its
arsenic has
high toxicity
Enrichment of arsenic in soils
containing arsenical
and
mining
pesticides during
the
early
Under oxic soil conditions arsenic is
chemically
which is
phosphate
dissolved
Already
Hurd-Karrer
have
or
distinguished:
high
P
phosphate
is
energy
an
al.,
low and
seems
via the
1960).
a
phosphate uptake
Two
high affinity system.
to have
a
higher affinity
Plant responses to arsenate and
and arsenate
to
plants
can
be
uptake by plants
al., 1994b; Naylor
et
for
a
at
et
al.,
by transport
Arsenate is taken
(Asher
are
and Reay,
generally
affinity system operates
P
deficiency. Although
phosphate
than for arsenate
at
the
they do
(Asher and Reay, 1979).
on
P:As ratio
growth
[mg
against As toxicity. Rumberg
phosphate addition improved plant growth
1991).
mechanism
The low
phosphate depend
found that in nutrient solution
needed to protect wheat roots
42
toxicity
uptake systems
different P
discriminate well between these two anions
(1936)
(Asher
concentration
process, mediated
consuming
concentrations, the high affinity system
mechanisms
not
a
sites in the soil
determining uptake and
and Ferguson, 1983; Clarkson and Lüttge,
et
similarity,
and
Peryea, 1994; Meharg and Macnair, 1990; Meharg
and
phosphate analogue
1979; Rumberg
this
to
Since then many researchers
by phosphate addition.
the interactions between
1996). Phosphate uptake
as a
(Pongratz,
phosphate
factor
Macnair, 1992; Meharg and Macnair, 1994; Meharg
up
arsenate
of the root cells
the
that arsenic
(1936) demonstrated
(Benson, 1953; Creger
proteins (Bieleski
extensive
binding
same
prime
as
Due
plasma membranes
as a
use
plants.
at least reduced
investigated
e.g.
to
led
has
phosphate.
of
Meharg and Macnair, 1991). Therefore,
of arsenate in
of rocks
(Smith, 1998).
and arsenate compete for the
toxicity
weathering
concern.
anthropogenic origins,
from
mid-1900s
to
analogue
of the soil solution must be considered
prevented
result of
a
predominantly present
and at the walls and
(Wauchope, 1983)
and Reay, 1979;
an
of the elements of public
1987). Additionally indiscriminate
contaminations of agricultural soils worldwide
1998)
as
commonly,
and Peterson,
smelting (Chilvers
of arsenical
one
either
occurs
more
or,
ores
long been
conditions. Hurd-Karrer
kg"1]
of at least 4:1
et al.
(1960) reported that
in nutrient solutions
was
containing sufficient
Effects of Phosphate
Arsenic
on
systems, results
arsenate to be toxic at low P concentrations. In soil
deleterious, negligible
growth
et
have been
al., 1973). One
designed.
were
uptake
beneficial effects of P addition
Jacobs and
reported (Hurd-Karrer, 1936;
reason
for this
In most studies
soils,
in
or even
P and As
added
As
on
the effect of P
simultaneously
ambiguous;
were
and
uptake
on
experiments
and
toxicity
As
et
al.
(1971b), however,
by the total
their concentrations in the soil solution rather than
several
reasons
the chemical
similarity, sorption
mechanisms, but
addition,
P forms
is
arsenate
organic complexes,
with
a
high organic
generally
sorbed less
with
with the result of
higher
already present
on
the latter. Due to
by
occurs
than
the
same
phosphate.
In
soluble As concentrations in soils
effects may influence As and P in
in the soil and sorbed
soil
on
particles
the amount of
may influence the
of added As and P.
focussing
and P to soils, the relevant situation in
practice
As contaminated
already
by
amount added. For
equilibration. Additionally,
While there has been much research
to
strongly
already
soil matter, while As does not
organic
matter content. Also kinetic
the soil, due to different time necessary for
competition
and arsenate
phosphate
of
organic complexes
form
As and P
simply depend
concentrations in solution do not
are
is determined
uptake by plants
As and P
plant
soil and effects
to the
related to the rates and ratios of P and As added. As has been demonstrated
by Woolson
plant
Keeney, 1970; Woolson
may lie in the way how the
diversity
investigating
were
ofSunflower
in Soils and Growth
Availability
on
the simultaneous addition of As
usually that P
is
soil, i.e. soils which
are
well
fertilizers
equilibrated
are
applied
with As, but
not with P.
The
objective of our study
growth
out to
to
investigate the
of sunflower
{Helianthus
determine the As mobilization
chamber to
Sunflower
to take up
effects of phosphate addition
in two different As contaminated soils
availability
and
was
investigate the
was
high
annuus,
as
L.).
capacity
well
as on
A batch
of P,
a
on
As
the As accumulation
experiment
was
pot experiment in
a
carried
climate
P
the two soils.
response of sunflower to the addition of to
chosen for this
study
because in
amounts of As in roots
previous studies this plant
and shoots without
was
able
showing toxicity.
43
Chapter
4.2
4
Materials and methods
4.2.1
Soils
The two soils used in this
surrounding of a brass
texture
of
a
were
smelter and the
had been contaminated
four decades
study
by arsenic
(Table 4.1).
the
topsoil of a Regosol
emissions of
The first
a
of
a
sandy
as
Table 4.1
weakly alkaline pH
due to carbonate
properties
experiment.
of the
Selected soil
the
industrial site which
Calcaric
a
are
Regosol,
had the
are
further characterized
silty
loam
Regosol
sandy
Regosol
CaC03 (%)
13.4
1.5
Corg(%)
4.2
1.9
Clay(%)
32
18
50
2
18
59
25.9
17.8
Cu
503
22
Pb
46
38
Zn
604
67
(%)
CEC
(meq
Total As
(2
100
M
g"1)
by
loam
7.1
Sand
used
a
at the start of
7.4
(%)
than
buffering.
Calcaric
type
more
pH (1:2.5 H20)
Silt
44
an
silty loam and the sandy loam
Soil characteristics
Soil
at
arable field from the
loam. These textures
henceforth to refer to the two soil materials, which
neutral to very
an
manufacture for
glass
soil, classified
silty loam, the second
of
plough layer
HN03, [mg kg"1]
Effects ofPhosphate
The soils
were
collected in
filled in PE boxes and
were
investigate
2003a
As
one
plants
the soil
different As pre-treatments
designation
soil
at
dried under
were
sandy
a
of both soils
spring,
silty loam
Four
and two
chosen. The
were
of a treatment refers to the soluble As concentration
[mg kg" ]
total
As
corresponding
3 mg
kg"1 (As_0),
100 mg
kg"
kg"1 (As_2.2), 225 mg kg"1 (As_5.2) in the silty loam and
190 mg
kg"1
(As_3.5)
and 225 mg
were
kg"1 (As_4.9) in the sandy loam.
experiment
kg"1
The P concentration of 56 mg
fertilization which is
of
al,
et
study.
of the present
of the
to
for each As pre-
winter. In the next
(As_3.5, As_4.9)
loam
pot experiment
The
150 mg
Batch
a
separately
over
beginning of the experiment.
the
(AsJ.l),
possibility
spade,
a
described elsewhere (Gulz
experiments
concentrations, extracted with boiling 2 M HNO3
4.2.2
used in
(As_0, As_l.l, As_2.2, As_5.2)
different As pre-treatments of the
number in the
as
greenhouse
used to set up the pots for
was
were
re-collected
was
treatment, mixed, dried and stored in the
of the
of
use
homogeneously. Aliquots
month the soils
different crop
uptake by
submitted.). Afterwards
the soil
pits by
they
where
greenhouse,
the
and mixed
cm
for
equilibration
and
to
from
with various amounts of As added in the form of Na2HAs04. After
spiked
spiking
early April 1999, excavated
1
<
ofSunflower
Arsenic Availability in Soils and Growth
transported
cover, sieved to
plastic
on
yield
soil used in this
normally applied
arable land in
to
increase and enhanced As
three different chemical forms, i.e.
as
experiment
was
spring.
based
With
uptake by sunflower,
P
on
regard
was
the P
to the
added in
Na2HP04/NaH2P04 1:1, NH4H2PO4, and
(NH4)2HP04.
sodium
Di-sodiumhydrogenphosphate (Na2HP04),
ammonium
phosphate ((NH4)2HP04)
the P treatments
are
were
labelled
NH4H2PO4 addition and
samples
as
without P addition
NaH2P04 resulted in
sodium salts
(NH4H2PO4)
di-hydrogenphosphate
was
a
pH of
+Na for
and
hydrogen-
di-ammonium
following,
from Fluka Chemicals. In the
purchased
as
di-hydrogenphosphate (NaH2P04),
Na2HP04/NaH2P04 addition,
as
+NH4 for
+di-NH4 for the addition of (NH4)2HP04. Control
are
labelled
10 and
needed to get
a
as
0 P. The solution of Na2HP04 and
4, respectively; therefore
pH
of 7, which
was
a
1:1 mixture of the
the desired
pH of
the
45
4
Chapter
solution. The solution of the other two salts resulted in
application
and
((NELO2HPO4)
application a
1.8 M stock solution of each P salt
corresponding
ml of the
therefore
(NH4H2PO4),
7
stock solution
adjusting
was
prepared.
runs
in
triplicates.
centrifugation,
shaken at 125 rpm for 24 h. After
was
pH of
6.5
For
necessary.
In each P treatment, 1
diluted 1:50 with 0.1 M NaNOß and than
was
added to 20 g dried soil. Each treatment
no
a
suspensions
The
the supernatants
were
were
filtered
(0.45 um) and immediately analyzed (see 4.2.4).
experiment
The pot
h
experiment
Pot
4.2.3
/ 8 h
(25°C)
umol m" s"
4
grains
.
was
was never
the soil did not
For
(Helianthus
containing
1
a
humidity
annuus
was
of 80 % and
L., San Luca)
kg dried soil. Sprouts
Water content
days after germination.
of the soil
climate-controlled growth chamber with
a
(16°C) day/night cycle,
Sunflower
in pots
carried out in
were
was
the
density
of
single plant
10
seeded at
reduced to
adjusted daily;
level of 450
light
a
a
a
water-holding capacity
exceeded, consequently leaching of As and
other elements from
occur.
application the
and P treatments
stock solution of the batch
same
are
labelled in the
same
way
experiment (see 4.2.2)
already described
in 4.2.2
was
by NANOpure
water and added to the
used
(+Na, +NH4,
stock solutions
+di-NH4 and 0 P). Three weeks after seeding, 10 ml of the
diluted 1:10
16
a
pots. All experiments
were
run
in
triplicates.
4.2.4
Plant and soil
Plants
were
analysis
harvested 5 weeks after seeding. Shoots
centimetre above soil surface. Roots
rinses of deionisized water to
and shoots
plants
were
digested
was
46
were
in
a
were
remove
dried at 60 °C in the
ground
in
a
dug
all soil
oven
(65 %)
added to obtain 25 ml for chemical
particles
samples
approximately
one
with several
from the root surface. Roots
weight
was
of 0.25 g
and 3 ml H202
analysis.
cut
carefully washed
until constant
titanium mill. Plant
mixture of 5 ml HN03
out and
were
obtained. Dried
were
microwave-
(30 %). NANOpure
water
Effects ofPhosphate on Arsenic Availability
samples
Soil
analyzed according
were
relating
Swiss Ordinance
sieved
homogenized,
were
extracts
analyzed
were
ICP-AES
through
for As
2
a
mm
sieve and dried at 40 °C for 72 h. Soil
metal amount
pH
extracted with
was
0.1 M NaN03. Plant and soil
by AAS-GF-HG (Perkin Elmer) and
for
Cu, P and Zn by
(Varian).
Effect of P treatments
4.3.1
In the
silty
phosphate
treatments
kg"1
in
In the
in
was
by
a
As_5.2.
As_0 and
on
soluble P and As in the batch
As_5.2 (Figure 4.1). Independently
added, it increased the soluble
factor of 2.6,
resulting
Most of the added P
10 % in
As_5
sandy loam,
(4.4 and
was
a
soil,
factor of 3.2,
no
differences
Phosphate addition
kg"1).
kg"1
sorbed after 24 h of
in
As_0
to
and 8.2 mg
shaking; only
was
5 % in
lower, therefore 20 % of the added P could be
were
As_3.5
and
As_4.9
P addition increased soluble P in both As
resulting
in P average concentrations of 15 mg
were
similar in
pre-treatments
kg"1.
Also in this
observed between +NH4, +di-NH4 and +Na treatments.
also increased soluble As concentrations in all As
phosphate
As_0
concentration in all As pre-
except in As_0 (Figure 4.2). Again, the mobilizing effect
which
in
of the added P amount remained soluble.
P fixation
4.6 mg
P
kg"1
of the chemical form in which
in averages of 3.9 mg
found in the soluble fraction. P concentrations in
0 P
experiment
loam initial soluble P concentrations varied from 1.4 mg
kg"1
3.2 mg
by
the
procedures given by
Results
4.3
by
ofSunflower
Impacts (VBBo, 1998). The soil samples of each pot
(65 %), soluble concentrations with
2 M HNO3
boiling
Soil
to the extraction
NANOpure H2O (1:2.5). Total
measured in
was
to
in Soils and Growth
was
added, but it
increase of soluble P. In all As
was,
was
pre-treatments,
independent
of the salt
however, slightly smaller than the
pre-treatments soluble As concentrations
were
doubled by the addition of P.
47
Chapter
4
14
P>
--
O)
E
c
g
'&
re
i_
+^
c
0)
o
c
o
u
As_0
As_2.2
As_1.1
As_5.2
As 3.6
As 4.9
As treatment
Figure
spiked soils after the
(batch experiment). Error bars
4.1 Soluble P concentrations of the two
+NFL, +di-NH4 and
error
+Na
treatment with 0
P,
denote the standard
(n=3).
E,
c
o
^p
re
i_
4-*
c
0)
u
c
o
o
(A
<
As_0
As_1.1
As_2.2
As_5.2
As_3.6
As_4.9
As treatment
Figure
0 P, +NH4, +di-NH4 and +Na
standard
48
spiked soils and the
(batch experiment). Error
4.2 Soluble As concentrations of the two
error
(n=3).
treatments with
bars denote the
Effects ofPhosphate
The initial P:As ratio
increasing
P:As ratio
1.3:1 in
was
largest
Availability
in Soils and Growth
highest
in
As pre-treatment to 0.6:1 in
As_5.2.
In the
As_3.5
general,
effects occurred in
loam
silty
in the
and 1:1 in
As_4.9.
of Sunflower
As_l.l (1.9:1)
was
sandy
and
loam the
In both soils P addition increased
increase of soluble P concentrations than soluble As
higher
this ratio due to the
concentrations. In
kg"1]
[mg
decreased with
Arsenic
on
the observed increase
As_3.5,
P addition resulted in
a
The
pronounced.
not very
was
P:As of 2:1
compared
to
1.3:1 without P addition.
4.3.2
In the
Effect of P treatments
on
soluble P and As in the
pot experiment
in all As prepot experiment, P addition enhanced soluble P concentrations
but
lower
the
in
than
experiment.
batch
treatments
(Figure 4.3)
Comparing
the initial with the final soluble P concentration in the control treatment,
a
significant
decrease of P
was
to
a
extent
observed in all As pre-treatments and both soils. The
experiment
decline varied between 20 and 25 %. Like in the batch
concentrations
were
lower in the
silty
sandy
loam than in the
increased soluble P in both soils but less than in the batch
loam soluble P concentrations increased with
to the
P),
control pots (0
the increase
increasing
factor of 1.6 in all As pre-treatments. In the
P concentrations
experiment, initial soluble
effect of P addition
was more
pronounced
were
as
added had
no
effect, neither
than in the
concentrations due to P addition
were
silty loam and the
soluble P
experiment,
nor on
lower than in the batch
concentrations to 1.4, 2.8 and 6.1 mg As
respectively (Figure 4.4).
30 %. In the
a
batch
P fertilization doubled the soluble P
initial As concentrations, P addition to the
treatments,
to the
a
the type of
soluble As in the pot
Similar to the increases in soluble P, the increases of soluble As
experiment.
to the
on
silty
averaging
constant,
sandy loam, similar
higher
In the
pre-treatment. Relative
As
concentrations in both As pre-treatments. As in the batch
phosphate
loam. P treatments
experiment.
quite
once more
was
soluble P
sandy loam,
factor of 1.6.
loam increased the soluble As
As_l.l, As_2.2
in the
corresponds
to
and
As_5.2
increases between 20 and
the addition of P increased the soluble As concentrations
Although
factors in response to P
This
kg"1
silty
experiment. Compared
soluble P and As concentrations increased
addition, the
P:As ratio did not
by
by
different
significantly change.
49
Chapter 4
O)
E,
c
o
re
i_
*j
c
©
o
c
o
Ü
As 3.6
As_5.2
As_2.2
As_1.1
As_0
As 4.9
As treatment
Comparison of
experiment and
4.3
Figure
with 0 P,
+
the initial soluble P concentrations at the start of the
the
NH4,
resulting soluble
+
P concentrations after the treatment
di-NH4 and +Na and the cultivation of sunflower.
Error bars denote the standard
error
(n=3)
10
D initial As
silty loam
D0P
O)
0
E
+NH4
+di-NH4
a +Na
o
re
c
o
c
o
u
(0
<
As_0
As_2.2
As_1.1
As_3.6
As_5.2
As_4.9
As treatment
Figure
4.4
Comparison
experiment
of the initial soluble As concentrations at the start of the
and the resulting soluble As concentrations after the
treatment with 0
P,
+
NH4, di-NH4 and
sunflower. Error bars denote the standard
50
+
Na and the cultivation of
error
(n=3).
Effects of Phosphate
on
Effect of P treatments
4.3.3
Most As
was
Arsenic
on
in root
In the
silty loam,
kg"1
within
were
As_l.l
in the
plants (Figure 4.5). The
was
a
only significant (p<0.05)
increase of
similar in¬
As_5.2.
in
arsenic concentrations in the roots varied between 201 and 279 mg
and between 517 and 764 mg As
sandy loam root concentrations did not
They
of Sunflower
sunflower
the addition of P translated into
by
the increase
uptake, although
crease
As
uptake by
As and P
accumulated in the roots of the
soluble As concentrations caused
in Soils and Growth
Availability
same
range
differ
within
As_5.2.
In the
significantly between As_ 3.6 and As_4.9.
the As concentrations in
as
kg"1
As_5.2
of the
silty
loam.
1000
900
1—1
'o
800
.*
o>
b
fawl
r
700
600
o
re
500
£
C
400
o
c
300
o
u
m
200
<
100
As 0
As
As_5.2
As_2.2
1.1
As 3.6
As 4.9
As treatment
Figure 4.5 Effect of phosphate
treatment
on
of sunflower. Error bars denote the standard
error
Arsenic concentrations in the shoots increased with
treatment in the two soils
proportional
(Figure 4.6).
to the increase of
shoots contained
and
As_5.2
treatments. These are
effects
on
for crop
increasing level
in the roots
of As pre-
In contrast to the roots, this increase
already
growth
normally reported
kg"1]
was
the initial soluble As concentrations in the soils. After
5 weeks of
As_4.9
[mg
(n=3).
As concentrations
plants
grown
soluble As, P treatments had
more
high
on
no
than 20 mg As
As concentrations
kg"1
in the
compared
As_3.5,
to values
As contaminated soils. In contrast to the
significant
influence
on
As accumulation
51
Chapter 4
by
shoots. Nevertheless, there
tendency
was a
shoots upon P addition to soil with
a
towards reduced As concentrations in
soluble As concentration and
high
a
tendency
towards increased As in shoots upon P addition to soil with low soluble As
concentrations.
E
c
o
re
0)
o
c
o
u
If)
<
As 4.9
As 3.6
As_5.2
As_2.2
As_1.1
As_0
As treatment
4.6 Effect of
Figure
phosphate
treatment on As
concentrations
shoots of sunflower. Error bars denote the standard
Compared
unspiked soil,
to
P
with and without P treatment
concentrations in the roots
accumulation
to increase P
increase
shoots
was
in
were
treatments on
significant
silty loam,
treatments.
52
was
no case
by
uptake by
roots was
pronounced
roots in all As
significant (p<0.05).
similar to those in roots
shoot P concentrations
in the
tendency
for such
an
sandy loam.
effect
on
P
P addition tended
two
soils, but this
In all P treatments, P concentrations in
(Fig. 4.8). Thus,
were
in the
As-pretreated soils
pre-treatments in the
the effects of As and P
similar to those of root
increase in shoot P due to P fertilization
a
reduced in
This effect of As pre-treatment
(Figure 4.7).
less
error
[mg kg" ]
(n=3).
was
was
observed
uptake.
only
in
While
As_0
a
of the
present, also in the other As pre-
Effects ofPhosphate on Arsenic Availability
in Soils and Growth
ofSunflower
O)
B
c
_o
re
C
0)
u
c
o
o
As_0
As_1.1
As_2.2
As_5.2
As 3.6
As 4.9
As treatment
Figure
4.7 Effect of
phosphate
treatment on P
concentrations
of sunflower. Error bars denote the standard
error
[mg
(n=3).
kg"1]
in the roots
O)
x:
E,
c
o
re
C
0)
u
c
o
o
As_0
As_1.1
As_2.2
As_5.2
As_3.6
As_4.9
As treatment
Figure
4.8 Effect of phosphate treatment
on
[mg kg" ]
(n=3).
P concentrations
of sunflower. Error bars denote the standard
error
in the shoots
53
Chapter 4
Effect of P treatments
4.3.4
shoot As concentrations
Although
of As
the
but
toxicity other
as
decreased
P fertilization
in the soil
induced
growth
distinctive in
more
toxicity
high
were
in
the
to
of sunflower
treatments,
were
observed
visual symptoms
no
on
the
silty
loam. In
visual As symptoms like necrosis of the older leaves
were
as
apparent in both As pre-treatments
increased root biomass
In the other As
nor
P induced
silty loam,
only
in the absence of As
(As_0)
pre-treatments of the silty loam, neither As
yield
increase
the other hand, root biomass decreased with
similar
some
growth
of roots and shoots
significantly
decrease
yield
and
As_4.9.
(Figure 4.9).
yield
As
than reduced shoot
sandy loam, however,
well
on
was
found. In the
increasing soluble
P fertilization did not affect root
sandy loam,
As in the
on
soil, but
growth.
u>
.C
D)
"53
a
o
o
As_1.1
As_0
As_5.2
As_2.2
As 3.6
As 4.9
As treatment
Figure
4.9 Effect of phosphate treatment
standard
error
fertilization increased shoot
effect
root and shoot
54
on
increasing
growth
only significant
was
root
dry weight [g].
Error bars denote the
(n=3).
Shoot biomass decreased with
increase
on
in
soluble As concentrations in both soils. P
in all As
As_0, As_5.2
growth was
pre-treatments (Figure 4.10), but this
and
lower in the
As_4.9. Generally,
sandy loam than
in the
the fertilizer
silty
loam.
Effects ofPhosphate
Arsenic
on
in Soils and Growth
of Sunflower
As_4.9
As_3.6
As_5.2
As_2.2
As_1.1
As_0
Availability
As treatment
Figure
4.10 Effect of phosphate treatment
the standard
4.4
4.4.1
error
on
shoot
dry weight [g].
(n=3).
Discussion
Effect of P addition
In the batch
as
well
as
on
soluble P and As concentrations
in the pot
soluble P and As concentrations,
experiment,
regardless
P addition
significantly
of the form in which P
soil. The lower increase of soluble P and As concentrations in the
attributed to the
high
P and As fixation
by
exchange
addition of P
of sorbed arsenate
was
competition between
capacity
of this
matter content. The increase of
carbonate, and organic
anion
Error bars denote
found
by Davenport
arsenate
and
and Peryea
silty
can
loam
to
can
the
be
higher clay,
be attributed to
A similar mobilization of As
(1991)
for surface
phosphate
applied
due to its
soil,
soluble As
against phosphate.
was
increased
and also attributed to
binding
sites and anion
exchange.
Different
experimental
conditions may have been
and As concentrations in the pot
were
water-saturated and
pot experiment, P
was
experiment.
In the batch
intensively shaken for
not mixed
one reason
24 h after
with the soil, but
for the lower soluble P
experiment, soil samples
phosphate
addition. In the
applied by watering
onto the
55
Chapter 4
surface two weeks before the
complete mixing. Another
effect may have been due to less
uptake. Comparison
third
that P
reason
uptake
in the
was
stronger phosphate fixation and
exchanging
same
P
sites.
adsorption
can
rapid initial adsorption followed by
several weeks
over
(Hongshao
phosphate precipitation
particles
concentrations in the pot
effect in the pot
4.4.2
the
findings
significantly
competition with
phosphate
on
of Woolson et al.
P
uptake
of
kg"1
corn.
step mechanisms,
two
equilibrium
in the pot
adsorption.
P
experiment
phosphate
The
As
uptake by
into soil
soluble
lower
P
As
(1973)
sunflower
uptake by
who
roots due to P
reported
Similar effects
were
also described
phosphate
on
addition confirms
that the addition of P increased
by Peryea (1998)
increased root
roots
was
significantly
uptake by
decreased with
Reay (1979) and Ullrich-Eberius
the two anions for
phosphate uptake
in
plant
binding
of
et
tissues.
sites.
Arabidopsis
al.
roots
increasing
et al.
et al.
thaliana
was
as
(1997),
kg"1, compared
(1973).
As in the soil. Asher
that arsenate decreased
attributed this effect to
Dunlop
well
and shoots in response to
(1984) postulated
They
as
lead arsenate contaminated soils.
by Hurd-Karrer (1939) and Woolson
soil used
phosphate accumulation
56
a
addition may be due to the rather low P addition of 56 mg
uptake by
and
by
of
agree well with the smaller As mobilization
moderate enhancement of As
to 1000 mg P
kinetics
adsorption
the
2001). Therefore,
shoot As concentrations of apricot liners grown
only
on
to
arsenate for anion-
slow reaction that may not reach
who found that the addition of monoammonium
The
experiment, leading
was
experiment.
tendency of increased
As
of the pot
be characterized
higher
in
experiment
Effect of P addition
The observed
a
when P
soil surface and diffusion of
at the
in
added. A
magnitude
Studies
and Stanforth,
resulted
have
may
order of
reduction of
specific sorption
and
phosphate showed that
a
a
plant
added, however, revealed that plant
was
longer duration
may have been the
may be
the reduced As mobilization effect in the pots,
only partially explain
could
provided
phosphate
no
reason
mobilizing
phosphate concentration
of the final with the initial soluble
the control treatment, in which
uptake
So the lower As
experiment was terminated.
competition
of
however demonstrated that
almost not affected
by
arsenate and
Effects ofPhosphate
only
concluded that arsenate is
not confirm the
to be a
for
weak
a
function of its
competitor
only partially
P
was
and Macnair
were
already
first necrotic
visible
compared
to
toxicity symptoms
however.
concentrations
the
on
the
phenomenon
may be
only
a
competition
in
uptake
significant damages
explain
findings,
our
because P
uptake,
but this enhancement
was
higher and
sandy
phosphate
loam
where
tips of the sunflower plants
was
added. Therefore it
higher soluble
be
can
As concentrations in
(at comparable
rhizosphere.
gradient
pore volume of the soil.
As
P
pre-treatment levels). This
differences in P and As
of phosphate and arsenate
concentration
toxicity symptoms occurred,
no
As concentrations not lower in the sunflower
explained by microscopic
by
roots leads to
This results in
a
a
availability
lowering
depletion
zone
in
of the
around
form soil to roots. Diffusion is the main
(Schilling
et
al., 1998) which depends
on
the
Therefore, in light textured soils diffusion is higher (and
than in heavier textured
hence
the leaf
and not due to P-induced As mobilization. These
mechanism for P transport in the soil
rhizosphere and
at
be due to the
silty loam,
P and As concentrations in the
faster)
higher
not found to be related to the As and P concentrations in the
not
rhizosphere. Uptake
the roots with
damages
silty loam,
the
On
shoots than
the
much
a
toxicity and yield of sunflower
week before
one
were
were
As
on
concluded that necrosis could
plants,
has
and Macnair
for the shoots in the uncontaminated control pots.
sandy loam,
this soil
be due to
found that arsenate induced
(1990)
added. P addition seemed to enhance P
Effect of P addition
On the
Meharg
also reduced in the roots of sunflower in the As pre-treatments in which
only significant
4.4.3
P. This does
increasing soluble
that also other effects decreased P
possible
of the root cell metabolism. This effect could also
no
In the
for arsenate. If this is true, decreased P concentrations in
and arsenate. It is
phosphate
was
of Sunflower
phosphate uptake.
phosphate/arsenate uptake system
that the
phosphate than
uptake. Meharg
uptake
for
in the soil. In addition,
availability
the roots and shoots of sunflower may
between
in Soils and Growth
findings of Bieleski and Ferguson (1983) who found that P uptake by
(1994a) demonstrated
affinity
Availability
root P concentrations decreased with
present study,
plants
Arsenic
on
higher
soils, leading
P and As
to
higher
P and As concentrations in the
uptake by plant
roots. Plants have
normally
57
Chapter 4
the
ability
to
detoxify
production, transport
detoxification
in the
capacity
irreparable damages
by
As
different detoxification mechanisms, e.g.
of the
plant,
As
loam in
our
accumulates
experiment might
explained by
be
have exceeded the detoxification
damages
and inhibited root
must not
necessarily
With
increasing
similar
cause
ability
growth. Therefore,
to
Similar results
growth
was a
in sunflower
uptake by
roots
sandy loam, however,
of sunflower
leading
to
As
the
on
which
uptake
heavy
root
similar As concentrations in the roots
was more
pronounced
were
growth
in the
found
growth,
was
increasingly
sandy loam,
toxicity symptoms.
P fertilization did not affect root
concluded that root
leading
roots
toxicity.
in agreement with the differences in other
shoot biomass.
slower As
soluble As concentrations root and shoot
inhibited in both soils. The effect
contamination,
the
the
toxicity symptoms
did not exceed the level of As detoxification. In the
might
in
uptake exceeds
of the cell membranes, disturbances of the hormone system and
the whole cell metabolism. The absence of
silty
to arsenite. If As
vacuoles, reduction
phytochelatin
but had
which is
In presence of As
a
positive
effect
by Creger and Peryea (1994)
poor indicator of As
on
who
toxicity.
Acknowledgements
We thank R.
Hort, Ch. Dähler and H.J. Bachmann for their great help and support in
the climate chamber and
laboratory.
Swiss National Science Foundation
58
This
project
(Grants No.
was
financially supported by
21-52758.97 and
20-61860.00).
the
P-enhanced
5
Phytoextraction
Contaminated Soil
P. A. Gulz, S. K.
Preparedfor publication
of Arsenic from
Using
Gupta,
Sunflower
R. Schulin
in Environmental Science and
Technology
Abstract
The
objective
of this
study
was
annuus,
L., San Luca)
removal
by adding phosphate
pot experiment in
a
to
investigate
the
potential
arsenic from soil and the
to extract
as a
mobilizing agent.
greenhouse, using
loam)
with different concentrations of
added
(0, 28, 56,
84 and 140 mg P
two
(Helianthus
to enhance this
possibility
For this purpose
different soils
aged arsenic
of sunflower
we
performed
(a silty loam and
to which
a
a
sandy
various rates of P
were
kg"1).
Our results show that P addition to As contaminated soil enhanced As accumulation
in roots and shoots. On the calcareous
soluble As concentrations in the soil
silty
were
loam this effect occurred
not increased
loam. At low As concentrations addition of P did not
in the
also reduced the
plants, but
toxicity.
only
as
they
significantly
mg As per
the
decreased
plant,
Maximum rates of As extraction
growth
than 3.4 mg As
kg"1
fern Pteris vittata L.
of sunflower
led to
(0.7-3.4
heavy
mg As
root
and As export. The maximum export of As
which is close to the maximum values
hyperaccumulating
large potential
higher
in the
to
be
used
reported
(ladder brake).
in
the
sandy
increase As accumulation
thus obtained at low to intermediate soluble As concentrations
Soluble As concentrations
were
although
were
kg"1).
damages,
was
11.42
in the literature for
This demonstrates the
phytoextraction
of As
from
contaminated soils.
59
Chapter
5
Introduction
5.1
Arsenic is
in nature and small amounts of this metalloid
ubiquitous
all environmental compartments. Due to
parent material arsenic is
of
weathering
kg"1 (Nriagu,
present in soils at background concentrations between 5 and 40 mg
1994).
addition, soils have been contaminated by arsenic
In
human activities. Emissions
coal combustion
are manure
use
pollution
for
agricultural
of
on
and
poultry
(Christen, 2001). Elevated
effects
soils
(Woolson
pigs due
arsenic
in soil
major topic
To clean up metal
manufacture and
to its
husbandry,
as
polluted
plants
to
concentrations in soils
1998). Suitable plants
are
for
hyperaccumulators.
phytoextraction
These
which
accumulate
produce
that of
very
extraction
a
large
lower
biomass
so
hyperaccumulators.
recently.
Ma et al.
calomelanos)
60
not
found to have
were
the food
proposed
has been
the
on
exceeding
are
as
low-cost,
a
applicable
not
capability
pollutant
(Brook,
those in the soil
be divided into two groups. The first
very
produce
high
a
amounts of
large
concentrations
than
that the total removal of the
Arsenic
kg"1.
hyperaccumulators
a
biomass
pollutant
so
plants
even
(Pteris vittatd)
fern
(Francesconi
et
but
exceed
have been identified
hyperaccumulating
has been identified in southern Thailand
may
in
that total
hyperaccumulators,
pollutant
that the brake fern
Another
to
of certain
remains limited. The second group consists of
(2001) reported
lated up to 4'980 mg As
can
plants accumulate
usually do
altogether
as a
al., 1960; Slekovec and
et
is based
in concentrations
phytoextraction
the harvestable parts, but
pollutant
arsenic is used
protection.
soils
pollutants
sources
Therefore remediation of arsenic contaminated soils
(Baker, 2001). Phytoextraction
accumulate
has
essential role in animal nutrition
which
»green« in situ alternative to soil-destructive treatments,
cultivated land
in soils.
inputs
organisms, impair plant growth and, by entering
soil
Irgolic, 1996; Wauchope, 1983).
a
glass
al., 1971a). Other
et
chain, threaten human and animal health (Rumberg
has become
result of various
containing fertilizers, pesticides, and desiccants
of As
and waste slurries of intensive animal
growth promoter
negative
from smelter wastes,
a
as
the main industrial contributions to arsenic
are
Furthermore, extensive
led to arsenic
originating
be found in
can
only
accumu¬
(Pityrogramma
al., 2002).
ofArsenic from
P-enhanced Phytoextraction
Contaminated Soils Using
Sunflower
uptake by plants
in the
past, little
biomass crop
plants
in arsenic
While there has been substantial research into As
attention has been
paid
phytoextraction.
previous
may be
candidate
a
2001).
Plant
soil
well
as
In
plant
P
the
potential
studies
we
use
was
supply (Gulz
et
of
high
(Gulz
found to
and
depend
al., 2003a; Gulz
Arsenic exists in different oxidation states but the
most
stable and therefore
Arsenate and
phosphate
phosphate
between
Woolson et al.,
solution
predominant species
are
1973). Therefore,
by displacement
of As to be taken up
can
However, P addition
solubility
and
to
not
very similar.
capability
these
Peryea, 1991).
roots. In
sites
specific sorption
a
is the
(Pongratz, 1998).
competition
(Wauchope, 1983;
due to
by adding phosphate
improved
was
the
et
not
and
and arsenate.
found to increase
only
Macnair, 1991), but
(Gulz and Gupta, 2001;
al., 1960).
study
mobilizing agent.
greenhouse pot experiment using
phosphate uptake
phosphate
P nutrition
of the present
as
availability
addition, phosphate fertilization may also
plants by stimulating
objective
through competitive
This in turn increases the
As contaminated soil
the
(AsV)
This leads to
was
of sunflowers to extract arsenic from the soil and the
this removal
performed
findings,
arsenate
sites in the soil
al., 2003b; Hurd-Karrer, 1939; Rumberg
on
pentavalent
discriminate well between
phytotoxicity
Gupta,
al., 2003b).
plant uptake (Asher and Reay, 1979; Meharg
also to reduce As
Based
by plant
and
L.)
soluble As concentrations in
on
et
annuus
P addition to soils may increase As in the soil
enhance As accumulation of
mechanisms, which
Gulz et
and
Gupta, 2000; Gulz
in well aerated soils
binding
of arsenate from
anion-exchange (Davenport
directly
chemically
and arsenate for
(Helianthus
found that sunflower
for this purpose
of arsenic
uptake
as on
to
two
to
investigate
possibility
For this
the
to enhance
purpose
we
different soils with different
concentrations of aged arsenic to which various rates of P
were
added.
61
Chapter
5
Materials and methods
5.2
Soil material
5.2.1
The two soils used in this
surrounding
of
by
(Table 4.1,
the texture of
a
the
were
brass smelter and the
a
had been contaminated
four decades
study
topsoil
neutral to very
The soils
were
soil that of
spiking
and
investigate
collected in
was
early April 1999, excavated
to the
transported
1
<
equilibration
As
for
crop
of
a
Afterwards the soil
of the pot
Regosol,
had
These textures
pits by
they
boiling
kg"1 (As_3.4),
2 M
240 mg
HNO3
were:
kg"1 (As_6.8)
5.2.2
Experimental design
experiment
was
and
use
are
by
of
a
spade,
dried under
were
May and early September
2000.
The
a
over
a
of both soils
pot experiment
separately
(Gulz
et
to
al.,
for each As
winter. In the next
spring,
present study. Four different As
of the
for the
silty
were
loam and two different As
chosen. The number in the
[mg
corresponding total
60 mg
kg"1 (As_0.7),
in the
silty
95
kg"1]
As
of the soil
concentrations,
mgkg"1 (As_1.3),
loam and 190 mg
210
kg"1 (As_3.1)
and
treatments
climate controlled
Aliquots
a
described elsewhere
greenhouse
phosphate
carried out in
used in
soluble As concentration
experiment.
kg"1 (As_6.9) in the sandy loam.
62
than
more
further characterized
from
where
were
as
sandy loam (As_3.1, As_6.9)
250 mg
The
are
re-collected
was
experiments
treatment refers to the
beginning
extracted with
mg
plants
(As_0.7, As_1.3, As_3.4, As_6.8)
designation
Calcaric
as a
homogeneously. Aliquots
month the soils
one
uptake by different
treatments for the
at the
greenhouse,
and mixed
cm
used to set up the pots for
treatments
industrial site which
sandy loam.
a
materials, which
treatment, mixed, dried and stored in the
it
an
with various amounts of As added in the form of Na2HAs04. After
submitted.).
2003a
at
manufacture for
glass
a
arable field form the
an
weakly alkaline pH due to carbonate buffering.
cover, sieved to
spiked
were
Regosol
soil, classified
The first
44).
p.
silty loam, the second
filled in PE boxes and
plastic
of a
arsenic emissions of
used henceforth to refer to the two soil
a
plough layer of
of 7
kg
greenhouse
of sieved and
between
early
homogenized
soil
P-enhanced Phytoextraction
filled into white
were
triplicates.
(50%
One week
KCl
as
(Helianthus
Numbers
and
In order to avoid
never
applied
was
application
a
0.63 M
(NFLt)2HP04
84 mg P
kg"1 (P_84)
and 140 mg P
two times at intervals of 21
Soil and
The sunflower
approximately
per pot.
of the soil
was
plants
(28
mg P
kg"1
Ordinance
and shoots
plant samples
and
in
a
were
were
30
concentrations
concentrations
(P_28),
56 mg P
were
days after seeding and
to Soil
sieved
for
sprinkling
a
water. In
kg"1 (P_56),
applied
(P_0)
was
to each
was
also
repeated
then
analysis
a
2
all soil
in
a
titanium mill.
according
aliquots
to
for chemical
particles
from the
weight
was
of 0.5 g
3 ml H2O2
(30 %).
analysis.
described
was
cut
carefully
Sub-samples
(65 %) and
procedures
were
out and
oven-dried at 60 °C until constant
ground
mm
dug
were
Impact (VBBo, 1998). One kg soil
through
Shoots
seeding.
remove
mixture of 5 ml HNO3
carried out
were
relating
analyzed
soil
kg"1 (P_140), respectively)
water was added to obtain 25 ml
homogenized,
prepared. Using
by adding NANOpure
harvested 18 weeks after
were
microwave-digested
analysis
was
centimetre above soil surface. Roots
one
obtained. Dried
NANOpure
hydrogenphosphate (NH4)2HP04.
days.
plant sampling
root surface. Roots
were
germination.
grains
water-holding capacity
washed with several rinses of deionisized water to
Soil
of 5
density
a
care
stock solution
application started
included. The first P
were
Mg (MgS04). Sunflower
soil. A control treatment without any P addition
pre-treated
5.2.3
kg"1
of As and other elements from the soil,
made up to 200 ml
were
this way, four different P treatments
As
K
was
after
in form of di-ammonium
10, 20, 30 and 50 ml
can,
kg"1
exceeded.
Phosphate
For
leaching
in
Water content
days
in the way that the
watering
taken with
ten
runs
fertilized with 180 mg
was
seeded at
was
plants
reduced to two
were
each pot
and 40 mg
K2S04)
as
L., San Luca)
annuus
adjusted daily.
was
50%
seeding
to
Sunflower
Each As pre-treatment level
plastic pots (0 29).
prior
Contaminated Soils Using
ofArsenic from
by
the Swiss
taken of each pot,
sieve and dried at 40 °C for 72 h. Soil
samples
pH and for soluble and total metal concentrations. Total metal
were
determined with
by extraction with
0.1 M
boiling
2 M HN03
(65 %), soluble
NaN03. Plant and soil
extracts
were
metal
analyzed
63
Chapter
5
by
for As content
Statistical
5.2.4
All statistical
distributions.
were
carried out
were
carried out
performed
were
of variance
Analysis
(ANOVA)
was
performed
to
evaluate the effect of
significant
using
Bonferroni
using Systat
(p<0.05), post
differences
10.0
hoc
plant uptake.
pair
wise
adjusted probabilities procedure.
If the
comparisons
All calculations
(SPSS, 2000).
Results
Effect of P addition
5.3.1
soluble P and As concentrations
amounts of added P.
and also much
differences
They
larger
was
(P_0).
binding
soluble P concentrations in both soils
increasing
The increases were, however, much less than
(Figure 5.1).
addition
on
P addition resulted in
Increasing
were
in the
larger
sandy
already present
It
can
be
at
higher
loam than in the
in the
the
P
all
sandy loam,
background
silty
P
same
treatments
effects
on
increased
increased from 3.1 to 4.7, 5.5, 6.1 and 9.7 mg As
respect
to
to
P_140.
P_0.
In
This
corresponds
proportion,
the
to
an
concentrations without P
phosphate
As in the two soils
soluble
mobilizing
on
kg"1
As
(Figure 5.2).
concentrations.
As_3.1
In
The
As concentrations
in the sequence of P treatments
increase of 50, 75, 100 and 200 % with
effect decreased with
pre-treatment. In As_6.9 As concentrations
silty loam,
the
loam. This pattern of
between arsenate and
mobilization effect increased with the rate of P addition. In
P_0
to
sites.
have the
from
proportional
than at lower As pre-treatment levels
explained by competition
Phosphate addition did
64
data to obtain normal
log-transformed
on
soluble As concentrations in the soil and As
on
F-value indicated
As
ICP-
by
analysis
analyses
the P treatments
for
and for Cu, P and Zn content
(Varian).
AES
5.3
(Perkin Elmer)
AAS-GF-HG
were
the contrary, low addition of P led to
a
increasing
only doubled
slight
in
level of
P_140.
In the
decrease in soluble As.
P-enhanced Phytoextraction
35
.*
silty
DP_0
O)
D>
Sunflower
loam
sandy
loam
ÖP_28
30
Œ3P_56
?5
HP
c
o
Contaminated Soils Using
40
^
E,
ofArsenic from
R4
re
i_
c
u
c
o
20
HP_140
•<
15
fflgi
u
a.
Q)
J2
3
o
(0
10
«
b
0
nraBÉ
As 0.7
nrfflil nfllli
As
As 3.4
1.3
As
Figure
As 6.8
As 3.1
-
As 6.9
pre-treatment
[mg kg"1] in the two soils after P treatments
(P_0, P_28, P_56, P_84 and P_140). Error bars denote the standard error.
5.1 Soluble P concentrations
As 0.7
As
1.3
As 3.4
As
Figure
nnil
l" n
r"p
n
5.2 Soluble As concentrations
(PO, P28, P_56, P_84
As 6.8
As 3.1
As 6.9
pre-treatment
[mg
kg"1]
in the two soils after P treatments
and P140). Error bars denote the standard
error.
65
Chapter
5
increasing
This 'immobilization' effect decreased with
highest levels
concentrations in
and PI 40
P_0
of P addition and at the
rates of P
higher
observed. At
were
Arsenic and
phosphate accumulation by
contained 100 mg As
roots
sandy loam,
5.3).
In the
were
410 mg As
kg"1 in As_3.1
and both soils. On the
and 340 mg As
As_0.7
by
roots
Without P
In the
was
higher.
kg"1 in As_6.8
by
roots in all As
was
decreased
were
uptake
only significant
in roots
increases of P had
P effects
In
on
As_3.1
higher
compared
controls at the
accumulation,
controls at low P treatment
to
highest
P treatment level. Increases
with that at the
found
was
by
As
on
was
higher
treatment level.
observed
on
the
As_6.8
a
doubling
and As
same
independently
kg"1
of the
applied
uptake by
roots
on
As_6.9
was
the
80 %
were
rate. In
for all P rates, which
the arsenic
pattern of
silty sand.
sandy
As
twice the
sandy
loam
loam.
shoots increased without P addition
In the
and increased to 69 mg As
shoots
and
As pre-
pre-treatment in the silty loam, significantly higher
the
pre-treatment level (Fig. 5.4).
As_0.7
As_3.4
loam As concentrations in the roots
P_0. Comparing
Arsenic accumulation
66
roots was
about 1200 mg As
corresponding
As accumulation
by
by
sandy
treatment of the
amount taken up in
In
effects relative to the lowest P level. The
negligible
was
As_1.3.
same
found at the lowest rate of P addition, whereas further
As accumulation
roots
and
As_0.7
with than without P addition,
uptake by
As
was
in
(Figure
pre-treatment levels
P addition resulted in increased As
silty loam,
silty
Root As concentrations
of root As concentrations due to different P treatment levels within the
of As
a
kg"1 in As_6.9.
and 600 mg As
not different from
were
in
As accumulation
As in the soil
although soluble
kg"1
As accumulation
Phosphate addition increased
treatment
addition,
plants.
addition, accumulation increased with increasing As pre-treatment level.
levels and
P
sunflower
As concentrations in the sunflower
highest
Roots accumulated the
loam,
soluble
between
significant difference
no
effect would have occurred also in this soil, if this trend continued.
mobilizing
5.3.2
applications,
of P
rate
silty loam,
kg"1 in As_6.8.
uptake
was
with
increasing
shoots contained 21 mg As
In the
87 mg As
(P_0)
sandy
kg"1 in
loam As accumulation
kg"1, independently on the As pre-
P-enhanced Phytoextraction
ofArsenic from
Contaminated Soils Using Sunflower
1600
DP_0
,-"
1400
D>
X.
D>
1200
E
C
1000
o
re
800
0)
600
-foP
28
HP_56
0P_84
P
140
o
c
o
ü
400
(A
<
200
0
As 0.7
As
As_3.4
1.3
As
Figure
5.3 As accumulation
kg"1]
[mg
As_6.8
As 6.9
As 3.1
pre-treatment
in sunflower roots
depending
on
soil and P
treatments. Error bars denote the standard error, n=3.
250
As_0.7
As_1.3
As_3.4
As
Figure
5.4 As accumulation
[mg
treatments. Error bars
kg"1]
As_6.8
As_3.1
As_ 6.9
pre-treatment
in sunflower shoots
depending
on
soil and P
denote the standard error, n=3.
67
Chapter 5
Arsenic concentrations in the shoots
were
positively
affected
by
P addition in all As
pre-treatment levels, except for As_6.9 (Figure 5.4). Phosphate induced increase of
As accumulation in the shoots
lower in the
was
While all P treatments increased As in the shoots
only reached for P_84
As_3.4.
in
The
highest
kg"1
P_140, respectively.
to the controls. In the
kg"1
in P28 to
As_3.1
P_140
P_140. Comparing similar
in
observed
was
as
significantly
in
and in
As_6.9
uptake
and
roots
with
for
As_6.8.
P
uptake by roots.
P
concentrations
was
sandy
of the shoots
in
uptake only
increasing
enhanced P
to 91 and 96
of 75
to an increase
a
and
131, 140, 152 and 170
kg"1 (P_0)
As
same
P_140
kg"1
to 235 mg As
accumulation pattern
by
shoots
was
in
pre-treatment level and
On the
was
silty loam,
tendency
each P treatment level
As
not
of
observed, but this increase
significantly higher
than
for
P_140
improved
corresponding
P
pre-treatment levels decreased
As_6.9, respectively.
uptake pattern
a
As_0.7 and As_1.3 and
was
As
P
addition
different
on
increased
P
the two soils. On
pre-treatment level. In the As_0.7, As_1.3 and As_3.4 pots P_140
a
factor of 2.5, while the other P treatments doubled P
of the P amount added to the pots. In
uptake only by
significantly
by the
P treatment level
were
to
loam.
(Figure 5.6). Increasing
As_6.8
uptake by
independently
68
P_0
observed
P addition increased shoot P concentrations but this effect decreased
silty loam,
with
silty
sandy loam, however
On the
concentrations of the shoots, but the
the
in
loam arsenic accumulation
(Figure 5.5).
P84 and
P_56,
kg"1 (P_0)
from 88 mg
affected
not
increasing
concentrations of the roots
P
kg"1
was
all rates of P addition led to
pre-treatment levels, the
As
different in the two soils
only significant
As_3.4
As_0.7, As_1.3 and
in
corresponds
This
from 94 mg
for the roots; in the
Phosphate uptake by
was
P_140
shoots in that soil
by
sandy loam,
twice the amount of As accumulation in the
increased P
and for
was
increase in shoot As at both As pre-treatment levels. Arsenic shoot
concentrations increased in
mg As
As_3.4
increase of As accumulation
in P84 and
%, compared
significant
and
silty loam, significance
As concentrations increased from 54 mg
As_3.4. Here,
mg As
As_1.3
in
the
on
loam.
sandy
loam than in the
silty
50 %.
and
On the
already
sandy loam,
P56 led to
higher
As_6.8
uptake,
P addition increased P
P addition increased P
uptake by
shoots
P concentrations in the shoots than
P_84
P-enhanced Phytoextraction
and
P_140
on
the
silty
P addition and the P
loam. As
ofArsenic from
on
uptake patterns
the
in
Contaminated Soils
silty loam,
As_3.1
and
P
uptake
As_6.9
Using Sunflower
increased with
were
increasing
very similar.
5000
4500
_
"o>
4000
|>
3500
^
3000
I
2500
I
2000
I
1500
re
°
0.
iooo -hi
500
As_0.7
As_1.3
As_3.4
As
Figure
5.5 P
uptake [mg
kg"1]
As_6.8
As_3.1
As 6.9
pre-treatment
in roots of sunflower
treatments. Error bars denote the
depending
on
soil and P
standard error, n=3.
20000
18000
_
"c>
16000
|»
14000
c
o
re
4-1
C
0)
u
c
o
u
As_0.7
As_1.3
As_3.4
As
Figure 5.6
P
uptake [mg kg" ]
As_6.8
As_3.1
As. 6.9
pre-treatment
in shoots of sunflower
depending
on
soil and P
treatments. Error bars denote the standard error, n=3.
69
Chapter 5
5.3.3
Visual
toxicity symptoms
In the sunflowers grown
phytotoxicity
than
on
The
with the
to
toxicity
high
earlier
on
sandy
The
more
Without P addition, the
P
growth
was
18
high
on
As
(Figure 5.3).
to
the
sandy loam,
As_6.9 pots, except
On both
As
increasing
of P
soils,
P addition led
plants flowered.
pre-treatment levels by
the other hand
on
silty loam, except
at
considerably
highest
the
As level
smaller at the intermediate than lower levels of As
added, although there
the rate of P
on
to decrease at the
highest
rate of P addition
1.3
As 3.4
.
As
5.7 Root biomass
[g]
As 6.9
As 3.1
As 6.8
was a
(P_140).
.
i
As
for
pre-treatment levels agrees well
depend
As 0.7
Figure
observed in all
not
pre-treatment. The effect did
slight tendency
As concentrations. On the
5.8). Addition
enhanced root and shoot
The enhancement
did not observe other symptoms of As
added the earlier the
plants responded
5.7 and
reduction
(As_6.8).
loam at
was
(Figure
growth
was
As accumulation in the roots
flowering.
we
higher
development
the
of sunflower
growth
silty loam,
reduction at
growth
necrosis and double shoot
P_140.
the
and
pre-treatment
of sunflower
depending
on
soil and P treatments. Error
bars denote the standard error, n-3.
A
quite
the
different pattern of toxicity effects of As and P treatments
sandy
loam. At the lower level of As pre-treatment root
than at all As levels in the
70
silty
loam without P addition
were
growth
(P_0),
observed
was even
whereas shoot
on
larger
growth
ofArsenic from Contaminated Soils Using Sunflower
P-enhanced Phytoextraction
was
intermediate between
of the
and
sandy loam (As_6.9), growth
contrast to the
In
As_1.3
As_6.9 it
160
silty loam,
was
P addition had
rather decreased root
just
no
At the
half
as
higher
strong
positive growth
As
as
pre-treatment level
at the lower level. In
effect
on
the
sandy loam.
growth.
1
.
-1
As_0.7
As_3.4
As_1.3
As
Figure
As_3.4.
5.8 Shoot biomass
[g]
As_6.9
As_3.1
As_6.8
pre-treatment
of sunflower
depending
on
soil and P treatments. Error
bars denote the standard error, n=3.
Discussion
5.4
5.4.1
The
Effects of P addition
reason
compared
soluble As and P concentrations
for the different effects of
two soils can be
of P to the
on
phosphate
related to the different
silty
loam
to the
sandy
explains
loam.
a
soluble As concentrations in the
phosphate sorption capacity. Higher sorption
rather small increase of soluble P concentrations,
Similarly, larger sorption capacity
smaller increase of soluble As with
the reduction of soluble As
on
by
increasing
P addition.
also accounts for the
Contrary
addition of low amounts of
to this
phosphate
in
trend
was
comparison
71
Chapter 5
to the controls with
largest
was
uptake.
A
the lowest level of P addition,
addition of calcium carbonate. In
soluble Ca concentrations
concentrations due to
our
experiment,
high.
were
decreasing pH.
Effects of P addition
plants
As
result
a
As and P
on
added to
loam suggests that
silty
Ca-apatite and
uptake by
Ca-arsenate may
P for root
sunflower
absorption
on
soils. In
our
with
depended
As
on
were
as
As
became
more
cannot
has
a
much
higher affinity
predominant
for
for
suspect that As induced damages of the
Macnair
(1990), played
While As
uptake
a more
uptake increased
was more
decreased with
found
highest
As pre-
Otte et al.
(1990),
the
at
by
increasing
on
In the
in
Urtica dioica grown in
on
As and P
silty
as
uptake by
well
as on
solution, while
As
of the
than for arsenate, than these results
binding sites
root
the
loam P accumulation
soil
the
by
in the
uptake mechanisms.
cells, also postulated by Meharg and
important role.
with
dependent
by
between As and
phosphate/arsenate uptake system
phosphate
fully be explained by competition
of arsenic
P accumulation
as
the ratio of soluble P and As concentration
accumulation increased. If it is true, that the
plants
well
uptake by
availability of these compounds in the soil solution.
decreased
as
P addition
experiments, the effect of
on
competition
addition, except
P
silty loam. Similar results
the
our
As
experiment,
increasing
uptake
found that the
result of
as a
the effect of P addition
investigated
sunflower
sites. In
clearly increased
treatment level
garden
this effect
They explained
sunflower
increasing concentrations of phosphate
from nutrient solutions decreased with
in the medium.
72
was
P addition could have increased soluble Ca
(1979) and Tsutsumi (1983)
Asher and Reay
We
calcium carbonate
no
after
spoils
precipitated from oversaturated solutions.
5.4.2
who
arsenic immobilization in
calcium carbonate content of the
high
the soils, but the
explained by plant
be
As-containing Ca-salts observed
soluble
sparingly
investigated
who
(1999),
only
not
can
of the decrease of soluble As concentrations due to P
be the formation of
Bothe and Brown
have
addition at all. This 'immobilization' effect, which
phosphate
possible explanation
might
addition
by
at
no
increasing
As
the first than
As
on
pre-treatment levels and P addition,
the second. In the
pre-treatment level. It
seems
silty
loam P
that P
P
uptake
uptake
was
by increased
inhibited
increasing
with
similar transport mechanisms.
Effects of P addition
5.4.3
Growth of sunflower
it had
soil
findings
probably
the lower P fixation
capacity
on
the
only depend
availability
a
process induces
certain soil
competition
zone
subsequent
a
depleted
and As
of the
zone
with
organic
a
thus diffusion
might
determine P and As
by
arsenic taken up
on
roots
as
growth
on
their surface
from soil to roots. This
water
transport is
the P demand of the
plant
more
as
well
as
only the
plant
and
and the water content, which
the pore volume
rhizosphere.
uptake
is
Plants roots take up P and
gradient
roots. Due to the
restricted in the
be lower and slower than in the
conditions in the
reason
higher soluble
well
as
P and As concentration
depends
soluble As and P concentrations represent
not the
in
a
Hagerstown
of P and As. The
rhizosphere.
concentration
around the roots
content,
in the
who found
P and As transport to the roots. The extension of the P
properties, mainly
matter
(1973)
sandy loam, resulting
determine the diffusion of P and As from soil to
and
the lowest As pre-
at
between P and As in the soil solution but also
of these two anions in the
depletion
pre-treatment level in the
(sandy loam) than
application
solution, thus lowering the
As from the soil
which creates
on
While P addition
suggest that As and P uptake
P and As concentrations. Our results
does not
As
of Woolson et al.
of corn in the Lakeland
after simultaneous
(silty clay loam)
highest
sandy loam, also
effect in the
treatment level. This agrees with the
higher yield reduction
of sunflower
from the
growth apart
growth
no
growth
on
clearly affected by phosphate addition.
was
increased root and shoot
silty loam,
in the shoots increased
uptake. Phosphate concentrations
As
Sunflower
P addition to the soil. Translocation of As into the shoots is similar to
suggesting
that of P,
Contaminated Soils Using
ofArsenic from
P-enhanced Phytoextraction
sandy
higher clay
loam and
silty
loam. Therefore similar
average conditions of the soil but
rhizosphere
But for
plant
growth.
Plants have the
roots
ability
conditions
to
detoxify
different mechanisms, e.g. reduction to arsenite,
by
transport into the vacuoles and phytochelatin production. The mechanisms have,
however, only
higher
cause
than this
a
certain detoxification
capacity,
significant
cell
As
can
damages.
capacity
accumulate in
In the
and if the As
plant roots,
sandy loam,
uptake by
roots is
substitute for P and thus
diffusion of As and P is
probably
73
Chapter
higher
in the
5
and faster than in the
rhizosphere
capacity
higher
loam. This leads to
P and As
by P
Action sites of
addition in the
plant
The lack of
hormones
flowering
sandy
are
P and As concentrations
on
membranes
(Poovaiah
at
was
not
only
due to
the root cell membranes, but
5.4.4
The
Efficiency
efficiency
and biomass
of As
simple competition
actually damaged
phytoextraction using
of phytoextraction
production
was
transported
the
on
of the harvestable
of the As extracted from the soil
of plant-accumulated As
depends
and
of double shoots
development
disturbance in the hormonal system. This agrees with the
reduction
growth
root and shoot
silty loam,
was
loam.
located
and the
higher
which exceeds the As detoxification
uptake,
of sunflower. Thus, in contrast to the
rather reduced
1976).
and
silty
Leopold,
imply
hypothesis
between P and As for
that
some
growth
uptake
sites
them.
sunflower
product of contaminant accumulation
plant parts.
In
experiment,
our
82 to 92 %
concentrated in the root biomass. The fraction
to the shoots
increasing
As pre-
silty loam
ha-1 yr-1].
and the
decreased with
treatment level.
Table 5.1
As
export via the shoots of sunflower grown
sandy loam calculated in [mg
As
plant""1]
and
on
[kg
the
As
Sandy
Silty loam
As 0.7
P treatments
As 1.3
As
loam
As 6.9
plant"-1]
5.17
1.90
5.70
6.82
2.82
7.37
2.51
3.76
6.94
6.84
2.30
8.64
3.49
3.94
6.58
6.71
3.03
9.93
3.95
6.36
7.44
2.46
11.42
10.69
P 0
P 28
3.03
P 56
P 84
4.73
As
74
As
As 3.1
2.08
2.88
P 0
export [mg
As 6.8
2.84
1.67
P 140
As 3.4
0.48
0.82
export [kg As ha1 yr"
0.81
i]
J
0.60
1.48
0.54
0.72
1.00
P 28
0.86
1.63
1.95
0.81
2.11
P 56
1.07
1.98
1.95
0.66
2.47
P 84
1.13
1.88
1.92
0.87
2.84
1.13
P 140
1.35
1.82
2.12
0.70
3.26
3.06
ofArsenic from Contaminated Soils Using Sunflower
P-enhanced Phytoextraction
pre-treatment levels As accumulation in shoots increased
At low As
growth
of As than
increasing levels
relationship reversed.
As
result
a
a
decreased. At
high
pre-treatment levels this
As
maximum rate of As extraction from the soil
As_1.3
found at low to intermediate As pre-treatment levels, i.e. at
loam and at
silty
P addition
the effect
As_3.1
on
the
was
stronger
export resulted
at the
at the
highest
The As export
which
by
to 2.12
only
highest
kg
As
proportion
As pre-treatment level
As
ha"1
export
treatment of As_3.1: 11.42 mg As
to
the
on
silty loam.
7.44 mg As per
was
y"1
on
the
plant"1
or
sandy loam
3.26
hyperaccumulating
of As from contaminated soils,
plant is
P_140,
kg
observed in the
was
ha"1
As
y"1
was
P_140
extracted in this
of the soluble As concentration in the soil. On
This demonstrates that sunflower has
crop
in
third of the soluble As concentration
or one
basis this is very close to the extraction of 13.8 mg As
the As
As
soil,
On that
plant in As_3.4
plant
(2002) with
on
maximum with intermediate rates of P
a
corresponding
and Ma
the
the amount of added P,
case,
to 15 %
on
found at the lowest As level.
shoots of sunflower
corresponds
in that soil. The
was
As_3.4
lowest level of P addition. The smallest P effect
the enhancement of As export reached
additions. An increase
or
was
silty sand (Table 5.1).
As extraction. In
clearly increased
with
more
a
plant"1
fern Pteris vittata L.
high potential
to be
used in
obtained
a
per
by
Tu
(ladder brake).
phytoextraction
considering
also that the cultivation of this
Schüpbach,
R.
common
well established.
Acknowledgements
We
gratefully acknowledge
their
help and support
supported by
in the
B.
greenhouse
and
Hort, E. Santschi and Ch. Dähler for
laboratory.
the Swiss National Science Foundation
This
(Grant
project
was
financially
No. 21-52758.97 and
20-61860.00).
75
Seite Leer /
Blank leaf
Concluding Summary
6
The
major goals
common
addition
and
crop
on
growth
of this dissertation
plants
as
a
were
investigate (i)
to
the As accumulation of
function of As concentrations in soil
the effect of P
(ii)
As
uptake
of sunflower to be used for
phyto¬
soluble As concentrations in soils and the consequences
of sunflower and
(iii)
potential
the
on
extraction.
6.1
Arsenic
In both
uptake
of
common
plants
crop
soils, soluble As concentrations, extracted with 0.1
correlate better with As
individually
between
plant species
relationship
but also between
Similar soluble As concentrations
accumulation
ryegrass,
by plant.
rape
Arsenic
was
concentrations in the seeds
soil. Results show that
different between
plant
not
general
did not
soils did not result in similar As
a
non-linear
by
a
P
maize, English
on
soluble soil
Michaelis-Menten kinetics. Arsenic
correlated with the soluble As concentrations in
responses to P
shortage and
significant, resulting
As stress
can
be very
arsenic transport from
in As concentrations in the leaves and
above the Swiss tolerance limits for fodder and food crops
availability and
dependence
plant species and soils. Except for maize,
was
kg"1, respectively).
only differ considerably
into roots, stems and leaves of
well described
were
found to
between soluble As concentrations in
in the two
uptake
were
soils, except for Lolium perenne.
and sunflower showed
concentrations, which
roots to shoots
in
by plants
soils and As accumulation
NaNÛ3,
than total amounts extracted with 2 M HNO3,
uptake by plants
for each soil. The
M
(4
mg As
kg"1 and 0.2
grains
mg As
Results suggest that beside soluble As concentrations in soil, P
demand, which is plant specific, have
predict As uptake by
common
crop
plants
to be taken into account to
from As contaminated soils.
77
Chapter
6.2
6
Effects of P addition
on
As
and
solubility
growth
and
As-uptake
of sunflower
The
applied
but did not
experiment
the P:As ratio. From the reduced As mobilization in the pot
change
concluded, that there
be
can
sites than in the batch
lower in the
was
silty
experiment.
loam than in the
not due to sites at which P
Phosphate
by
shoots. The
moderate
only
sunflower in the pot
to the
6.3
polluted
soils.
is
shoots, especially in the low
effect of As,
out in
plants
which
a
promising
a
on
the
As concentrations and
growth
chamber
to the modified soil
new
chemical
method for the
analogue
enhance As accumulation in sunflower
can
but
to
As
although
even
of
be attributed
progressive clean-up
of arsenate, is able to
was
by adding
soluble As concentrations
significantly
were
not
decreased at low rates of P addition. This
in the soil. Addition of P did not
only
be
sorbed
possible
P to the soil. Our results
contaminated soil in fact
of metal-
displace
might
to
show, that
enhanced As
silty
increased
loam this
on
as
again showed
soluble concentration of As alone is insufficient to characterize its
78
growth
conditions after P
accumulation in roots and shoots of sunflower. On the calcareous
sandy loam,
already
of As from contaminated soils
arsenate and thus increase soluble As in the soil. Therefore it
phosphate addition
P
longer growth period.
phytoextraction
Phosphate,
effect occurred
was
soil,
increased As accumulation in roots and
effect of P
experiment carried
due to the
P-enhanced
Phytoextraction
higher sorption
At low soluble As concentrations in the
yield decreasing
increasing
were
pot experiment in the greenhouse, however, this effect
In the
significantly higher
into roots and
uptake
short exposure time of the
application.
time soluble P concentrations
arsenate.
(1936), despite
Hurd-Karrer
same
sorption
with P for
competition
less
loam. This indicates that the
sandy
experiments.
ameliorated the
fertilization
was
At the
displaced
addition increased As
As pre-treatments in all
described
soil,
base P fertilization increased soluble P and As concentrations in the
the
that the
phytoavailability
increase the accumulation of As in the
plants,
Concluding Summary
but also reduced its
up to 3.4 mg As
kg"1
concentrations, i.e. soluble soil concentrations
At low As
toxicity.
soil, growth
was
Maximum rates of As
significantly increased.
extraction were, thus obtained at soluble As concentrations in the range of 1.3 to 3.4
kg"1
mg As
soil.
Higher
significantly decreasing
soluble As concentrations led to
not
maximum rate of As export
values
reported by
phytoextraction
Although the
recently
(2001)
for the
which is close to the maximum
of sunflower to be used in the
toxicity
acute
questions
of arsenic has been known since
that chronic effects have been
reported.
As
a
This
L"1,
rape
of
water from 50 \ig
drinking
chain,
vicinity
As
of As
have been
surveyed
on
a
problem
moderately As-contaminated
low to
only
L"1
to
for the
ryegrass,
soil
clearly
plants. Thus, by entering
threaten animal and human health. In
can
only
quality. English
and food/fodder
water but also for soil
the Swiss limits for As in fodder and crop
surpassed
food
has shown that arsenic in the environment is not
sunflower grown
and
is
except Switzerland.
study
quality
antiquity, it
consequence, many countries
Europe have lowered the limit of arsenic in drinking
10 (ig
fern Pteris vittata L.
hyperaccumulating
large potential
damages,
but also As export. The
growth,
plant"1
root
of As from contaminated soils.
Outlook and open
6.4
11.42 mg As
This demonstrates the
(ladder brake).
in
was
Ma et al.
root and shoot
only
heavy
the
Switzerland, sites in the
emitting industries and agricultural soils where arsenical pesticides
applied
in the past,
to evaluate
especially against
the Colorado beetle, should be
the risk of fodder and food contamination via the
pathway
soil-
plant-animal and/or human.
The bioaccumulation of As
by sunflower
As from contaminated soils. Efficient
possible
in
our
study
is
a
promising technique
phytoextraction
up to 250 mg As
kg"1
soil. At
for the removal of
by
higher
As concentrations
extraction decreased both biomass and As removal. In addition, the
enhance As accumulation of sunflower is
and
organic
matter
higher
in soils with
content, since P sorption is low. A
sunflower
of As
a
efficiency
low
clay,
growth period
was
of P to
carbonate
of 12 weeks
79
Chapter
6
with two
best
applications
applied
of
phosphate
would
in form of a neutral salt. The
soil acidification due to
probably
use
high proton input.
ammonium concentrations in soil limit root
of (NH4)2HP04 has the
In
performed,
further pot
effectiveness
of the
described
of As
80
chemistry
in the soil.
preferable.
greenhouse
are
experimental changes.
arsenate salts due to P addition should be
of
growth (Marschner, 1995). Therefore,
of NH4H2PO4 and KH2PO4 would be
in the
disadvantage
addition, it is well known that high
application
experiments
be most effective. P should be
investigated
to
Before field tests
are
verify
the
precipitation
of
recommended to
the
Also
allow
a
better
understanding
7
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Geochemistry.and Health 7(4):131-133.
Yan-Chu, H. 1994. Arsenic distribution in soils, p. 17-49, In J. O. Nriagu, ed.
Arsenic in the Environment, Part I:
Nriagu,
J.
Cycling
and Characterization, Vol. 26.
O., Ann Arbor.
87
Seite Leer /
Blank leaf
Appendix
Appendix
1
90
Appendix
2
91
Appendix 3
93
89
Appendix
Appendix
1
and
Arsenic accumulation in roots and shoots of Z. mays, L. perenne, B. napus,
solution
nutrient
(0.1%)
free Hoagland
in
H. annuus after 14
phosphate
days
1, 1.5 and 2 mg As
containing 0, 0.5,
solution was adjusted
to
6,
the
L"1,
added
optimum pH
for P
as
Na2HAs04.
The
pH
of the
uptake.
1400
1200
1000
E
-•-
H. annuus
-*
Z. mays
-x-
L. perenne
-*-
S. napus
800
c
o
2
600
c
400
0)
o
c
o
o
200
If)
<
0
As
Figure
[mg
Al.l Arsenic concentrations
L'1]
[mg
kg"1]
in roots of Zea mays, Lolium perenne,
annuus.
1
0.5
[mg
L"1]
1.5
in nutrient solution
Figure A1.2 Arsenic concentrations [mg kg" ] in shoots of Zea
Helianthus
perenne, Brassica napus, and
90
2
in nutrient solution
Brassica napus, and Helianthus
As
1.5
1
0.5
annuus.
mays, Lolium
Appendix
Appendix 2
Means [mg kg"1]
and standard
errors
of copper
(Table A2.1)
and zinc
(Table A2.2)
concentrations in roots, stems, leaves and seeds of Z. mays, L. perenne, B. napus,
on the silty loam and the sandy loam (see chapter 3).
and H. annuus
grown
Table A2.1
Plant
Copper [mg kg"1]
Soil
As treatment
As 0
s
VI
O
5*
1
B
«
«
1
>>
247.76Ü7.53
6.63i0.10 ll.06il.16
232.66±9.97
6.49i0.40
9.93i0.40
7.10i2.26
5.65i0.27
6.07i0.55
228.44±30.46
6.25i0.31
As_7.1
199.52il8.38
6.12i0.58
8.53i0.64
As 2.8
14.31il.29
3.32i0.20
8.05i0.80
2.14i0.32
8.02i0.64
2.03i0.19
7.73i0.52
2.44i0.36
As_6.9
16.llil.31
3.19i0.10
a
.a
S
As 0
360.48i22.75 27.29i0.29 25.99i0.35
As 1.1
310.56ill.93 25.20i0.69 22.54i0.19
As 2.8
331.09i29.47 24.15il.05 21.74i0.49
As_4.7
As_7.1
332.04i21.01 23.93i0.71 20.94i0.39
361.5Ü46.04 22.33il.71 18.57il.07
As 2.8
22.49il.39
9.2Ü0.24
8.39i0.51
22.49il.39
As 4.1
18.61i0.32
8.64i0.37
7.07i0.39
18.6Ü0.32
19.20i0.67
8.19i0.26
6.59i0.28
19.20i0.67
As 0
51.60il0.20
6.24i0.62
As 1.1
79.95il5.22
5.37i0.57
42.3i2.96 13.42i0.69
38.45il.47 13.28i0.68
A4
As_6.9
SS
Vi
§-
As 4.7
8.46Ü.44
15.12i0.43
as
*35
6.11Ü.66
6.49i0.89
As 4.1
VI
t>5
15.57i0.08
As 2.8
n4
fi
6.96i0.16
o
*>
^
185.71±4.40
s
..M
©
Leaves
3.54i0.19
Vi
%>
Stems
As_l.l
Vi
%
39.53il.04 16.57il.23
B
As 2.8
75.05i8.76
5.19i0.38
o
As 4.7
94.07il2.17
4.8Ü0.18
37.47±0.67 14.36i0.85
As_7.1
140.49il9.48
5.39i0.38
33.84il.40 14.16il.13
As 2.8
12.07i0.48
1.94±0.08
4.47i0.24
3.26i0.14
As 4.1
11.17Ü.14
1.91=1=0.10
4.7Ü0.10
3.28i0.15
As_6.9
ll.13il.35
1.89i0.07
4.83i0.58
2.82i0.41
176.51i7.58
7.56i0.16
16.3Ü0.53 14.49±0.40
s
Vi
Vi
g
ßq
B
Vi
o
Vi
As 0
Vi
»
5
S
«
>>
a
As 1.1
148.46il4.48
6.55i0.26
25.30i0.53 16.08i0.30
As 2.8
192.17il4.48
6.85i0.10
28.70il.43 16.12i0.24
As 4.7
239.10i27.05
8.00i0.61
33.38il.21 15.44i0.45
As_7.1
254.34i20.27
7.43i0.32
24.85i0.63 13.53i0.13
As 2.8
25.15il.02
3.23i0.31
8.32i0.08
7.75i0.21
As_4.1
23.67i0.80
2.81=1=0.27
7.46i0.17
8.41=1=0.19
As 6.9
24.92i0.74
2.73i0.30
5.44i0.10
7.38i0.27
fl4
W
VI
_©
Vi
S
s
s
>>
S
e
W
X
Seeds
Roots
a
o
91
Appendix
Table A2.2 Zink
Plant
Soil
>>
vt
Vi
SS
'vi
O
[mg kg"1]
Leaves
Seeds
Roots
Stems
As_0
105.00i9.25
85.54i4.26
178.93Ü1.28 40.32i2.76
As 1.1
132.41Ü3.45
89.38i3.12
135.74i8.47
51.39i6.74
113.54ill.41
133.3Ü9.09
61.78i4.43
As treatment
As 2.8
125.53i9.29
As 4.7
166.59i7.99
99.27i4.73
132.81Ü7.17 60.52i7.19
119.75i8.34
107.07i5.14
71.90i5.06
As_7.1
163.16i6.04
As 2.8
38.6Ü4.33
23.19il.86
55.09i2.22
25.64i2.75
As 4.1
40.56il.88
28.91il.38
52.1Ü3.48
23.73il.67
As_6.9
39.27il.17
26.85i0.63
47.47i0.97
25.28il.18
As 0
452.82Ü2.89
244.20Ü.91
315.52i6.45
As 1.1
454.21il7.17
146.10i0.74
225.4Ü0.62
As 2.8
403.34ill.00
146.86i3.06
201.10i0.65
As 4.7
377.2Ü4.05
156.46ilO.94
182.43i9.49
As_7.1
357.1Ü2.46
170.84i9.21
171.66i7.75
^3
N
TS
fi
B
«
Vi
s
s
>>
B
«4
Vi
AS
Q
^
>->
TS
B
B
C9
At
«
Vi
As 2.8
156.50il2.88
33.52i0.68
41.96il.98
As 4.1
123.97i4.97
39.47i5.03
35.76i0.58
As_6.9
111.54i7.08
30.62il.ll
35.97il.94
96.74il0.24
60.90i0.87
129.61il.37
53.03i0.63
117.38i3.93
48.74il.38
As 0
91.55i6.04
48.28i3.72
As 2.8
83.78i6.03
43.57i0.68
104.44il.10
46.23i3.11
As 4.7
90.05i3.23
37.56i0.84
82.73i5.06
43.85il.78
As_7.1
86.37i3.33
39.26i2.05
79.40i2.29
48.21i3.24
As_2.8
41.43il.47
9.8Ü0.86
38.23i3.32
26.18i0.64
As 4.1
37.18i3.08
10.64i0.29
32.35i0.44
24.25i2.07
22.32il.19
As 1.1
S
Vi
8"
'vi
s
v\
g
BQ
%
B
fi
v3
es
Vi
Vi
3
a
a
a
a
>>
S
ff4
As_6.9
33.83i2.65
10.62i0.29
37.08i3.44
As_0
171.67Ü6.30
78.85i4.64
151.07i5.58
45.69i0.75
As 1.1
205.14i27.07
58.78Ü.21
120.3Ü0.19
47.05i0.46
As 2.8
231.65i21.56
61.94i3.58
112.30i3.32
44.28i0.79
As 4.7
252.00i38.98
65.70i4.07
110.77i2.22
44.31il.35
As_7.1
413.04i62.28
63.1Ü0.36
105.60i6.08
42.69il.97
As 2.8
154.73ilO.84
26.25i0.64
49.77i0.59
23.88i0.48
As_4.1
155.29il0.48
27.07Ü.79
54.60i3.20
27.60i0.74
As 6.9
116.21ill.50
20.28i3.62
44.47il.32
25.05i0.65
va
'vi
Vi
a
"S
a
>>
S
92
fi
v3
CA
B
eu
Appendix
Appendix
3
[mg kg"1], As and P concentrations in
roots and shoots [mg kg"1] (dry weight) and yield [g per pot] of sunflower grown
10
in As_3.4 of the silty loam and in As_3.1 of the sandy loam and harvested
P84 and P140 (see
days after the first, second and third addition of P_26, P_56,
Means of soluble As and P concentrations
chapter 5).
Table A3.1 Means of soluble As and P concentrations
[mg kg" ] after the first,
second, and third application of P28, P_56, P_84, P_140, n=2.
Replication
P treatment
Silty
Sandy
loam
As 3.1
As 3.4
of P addition
soluble As concentration [mg
loam
kg"1]-
P 28
3.3
3.8
After 1st P
P 56
3.7
5.6
addition
P 84
4.7
6.2
P_140
5.0
10.0
P 28
3.3
3.6
P 56
3.5
5.0
P 84
4.8
7.1
P_140
5.3
9.5
P 28
3.0
3.6
P 56
3.0
5.1
P 84
3.9
6.1
P140
4.4
9.0
After
2nd
P
addition
After
3th
P
addition
-soluble P concentration
After
1st
P
addition
After
2nd
P
addition
After
3th
P
addition
[mg
kg"1]-
P 28
3.6
5.5
P 56
4.3
10.2
P 84
6.5
12.9
P_140
10.1
33.9
P 28
3.7
5.0
P 56
4.0
7.2
P 84
5.9
13.7
P_140
10.9
24.1
P 28
3.4
4.8
P 56
3.2
7.4
P 84
4.7
8.2
6.3
19.8
P
140
93
Appendix
[mg kg" ] in roots of sunflower after
the first, second, and third application of P_28, P56, P_84, P_140, n=2.
Table A3.2 Means of As and P concentrations
Replication
P treatment
Silty
of P addition
—
After
1st
P
After
2nd
P
addition
After
3th
As concentration
P
addition
As 3.1
kg"1]—
361.0
598.7
P 56
401.4
814.4
431.4
744.1
P140
411.4
981.4
P 28
455.2
584.3
84
P 56
508.9
814.0
P 84
575.7
679.7
P_140
485.6
926.3
P 28
592.5
831.7
P 56
646.7
860.8
P 84
719.6
770.9
P 140
755.9
1024.5
ion
[mg
kg"1]—-
P 28
1993
1815
After 1st P
P 56
2242
2753
addition
P 84
2095
2666
P140
2102
3814
P 28
1934
1791
P 56
1962
3463
After
2nd
P
addition
After
3th
P
addition
P 84
2202
3875
P140
2019
5416
P 28
1202
2700
P 56
1256
2000
P 84
1556
3716
1589
5581
P
94
[mg
Sandy loam
P 28
P
addition
loam
As 3.4
140
Appendix
[mg kg" ] in shoots of sunflower after
first, second, and third application of P_28, P_56, P_84, P_140, n=2.
Table A3.3 Means of As and P concentrations
the
Replication
P treatment
Silty
loam
As 3.4
of P addition
—
As concentration
[mg
Sandy
loam
As 3.1
kg"1]—
P 28
25.7
55.6
After 1st P
P 56
25.2
66.0
addition
P 84
28.2
56.3
P140
24.2
61.4
P 28
40.8
51.4
P 56
45.2
65.6
P 84
55.9
53.5
P140
45.2
61.1
P 28
81.2
86.1
P 56
89.2
112.7
P 84
105.0
94.2
PI 40
108.1
100.4
After
2nd
P
addition
After
3th
P
addition
—P concentration
After 1st
P
addition
After
2nd
P
addition
After
3th P
addition
[mg
kg"1]—
P 28
3484
2766
P 56
3888
4489
P 84
3446
4275
P_140
3551
6187
P 28
3923
3868
P 56
4257
6115
P 84
4709
6661
PJ40
4159
8485
P 28
8543
12834
P 56
5795
10595
P 84
6122
12219
7128
17028
P
140
95
Appendix
Table A3.4 Means of root and shoot
second, and third application
Replication
of sunflower in g per pot after the first,
of P_28, P_56, P_84, P_140, n=2.
yield
P treatment
Silty
loam
As 3.4
of P addition
Sandy
loam
As 3.1
yield root[g]
After
1st
P
addition
After
2nd
P
addition
After
3th P
addition
2.6
P 28
4.3
P 56
3.3
1.9
P 84
3.7
3.1
P_140
4.1
2.9
P 28
8.0
8.7
P 56
9.7
12.4
P 84
5.3
10.4
P_140
6.2
9.6
P 28
7.6
3.2
P 56
6.9
8.7
P 84
5.3
10.5
P_140
5.9
7.4
yield shoot [g]
P 28
5.6
After 1st P
P 56
9.9
5.3
addition
P 84
10.1
7.3
P_140
11.9
6.9
P 28
23.4
18.1
P 56
22.9
26.0
P 84
14.8
23.2
P140
18.6
24.6
P 28
73.9
40.3
P 56
80.1
72.2
P 84
68.4
85.9
75.2
84.8
After
2nd
P
addition
After
3th
P
addition
P
96
12.0
140
Acknowledgements
I
am
very
grateful
to Prof. Rainer
this dissertation, for the fast
the
opportunity
to carry out
manuscript
and all the
helpful
Schulin who gave
reviewing
of the
me
Gupta
constructive advices. I would like to thank Dr. Satish K.
giving
for
the
me
possibility
work autonomous and
to
practical part
colleagues
all
at the
in
never
shortened
very
have been
never
by
special
forget
helping
charming
smile
for
managing
indepted
me,
to
set up
long lasting
well
as
me
just
the
spirit of
me
personal support,
as
Brigitte Schüpbach,
in the
greenhouse,
when I needed
a
giving
a
to
my
tackle
this work
hand, whenever
sessions in the climate chamber till
and the fun and
not
laughter
only
for
but also for
cheering.
bit of
greenhouse experiments
we
I needed
midnight, just
had most of the time. Also
doing all
giving
the As
me
her
analysis
at
the
friendship and
I would like to thank Otto
and for his continuous
only
at
accurate and fast. I thank Kathrin
professional things. Special
perfect conditions
for my
friend. I would like to thank all
(IUL)
team
help.
I
a
Wyss
very
am
Charlotte Dähler, who has done all the thousands of analysis at the ICP for
incredibly
me, not
our
thank to
AAS and
thanks to
possible.
pizza break,
a
great
IUL, also in the final period of our institute, encouraged
I would like to thank Rosmarie Hort for
Particularly
it. I will
Berne. The
Liebefeld,
arising problems. Without their professional
would
independent. Many
of this thesis has been carried out at the Institute of Environmental
Agriculture (IUL)
Protection and
for his support and
manuscript.
Prof. Hans-Rudolf Pfeifer for the review of this
The
and
for technical
and
in
Marta
helping and supporting
hydroponic systems
helped
and is
a
me
to
great
of the Institute of Environmental Protections
analytical assistance,
friendship: Hans-Jörg Bachmann,
for
thank to Beat Herrmann, who
experiments
colleagues
Wenger
Ejem,
beneficial discussions
Oskar Fankhauser,
or
just
her
Kaspar Grünig,
97
Stufi Jones, Thomas Keller, Uschi Linder, Ariane Rudaz, Elisabeth Santschi, Hossein
Shariat-Madari, Werner Stauffer, Konrad Studer, Elisabeth Wälti and F.X Stadelmann.
I would like to thank all the
their support,
Scheid
-
Last, but
a
especially
very
not
special
least,
Achim
Kayser,
of the Soil Protection group of the ITOe for
Armin
Keller, Markus Jauslin and Susanne
friend.
I would like to thank my sister and my
my visions and ideas I had
98
colleagues
so
far.
parents for supporting all
Curriculum Vitae
Surname
Gulz
Given
Petra
names
Angela
Date of birth
09.09.1969
Place of Birth
Munich, Germany
Citizenship
German
School Education
1976-1980, Grundschule
am
Ravensburgerring,
Munich
1980-1989, Bertolt-Brecht Gymnasium, Munich
Higher Education
1990-1996
Studies of Physical Geography, Diploma, LudwigMaxmimilians-University, Munich, Germany
Occupation
1989-1990
Nursing
assistant at the Klinikum Grosshadem,
Hospital of the
Ludwig-Maxmimilians-University, Munich, Germany
1996-1998
Editor: Thema GmbH Munich;
Weltbild
Verlag, Augsburg
Author: Redaktionsbüro Norbert Pautner,
Verlag Wolfgang Kunth
1998-present
Munich;
GmbH &Co KG, Munich
teaching assistant at the Institute of
(IUL) Liebefeld-Bern and at the Institute
of Terrestrial Ecology, Soil Protection Group, Swiss Federal
Institute of Technology (ETH), Zurich, Switzerland
PhD studies and work
as
Environmental Protection
Bern, 10 October 2002
99