Toxic elements and their compounds
at nano and picomolar concetrations
in environmental (air, water,
sediment, soil) and biological
samples
Milena HORVAT
Departments of Environmental Sciences, Jožef Stefan
Institute, Jamova 39, Ljubljana, Slovenia
[email protected]
Introduction
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Speciation of trace elements: toxicity vs.
essentiality
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Cr: Cr(III) vs. Cr(VI)
Hg: organic vs. Norganic Hg compounds
As: As(III) vs. As(V), organo-As compounds
Sn: inorganic vs. organic Sn compounds
Se: deficiency vs. toxicity, speciation and dose
Important application in nutrition, clinical
chemistry, occupational exposure, environmental
sciences and industry
Definitions
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“Speciation analysis is the analytical activity
of identifying and/or measuring the quantities of
one or more individual chemical species in a
sample.
The chemical species are specific forms of an
element defined as to isotopic composition,
electronic or oxidation state, and/or complex or
molecular structure.
The speciation of an element is the distribution
of an element amongst defined chemical species
in a system. “
IUPAC, 2000
Evolution of speciation analysis
Determination
of organometallic
compounds
Identification
of unknown
metallobiomolecules
Sn
Cl
Organotin:
RnSnX(4-n)
Organomercury:
MeHg+, Me2Hg, Et2Hg
Organolead:
MemEtnPb(4-m-n)
Metal complexes with
Proteins,
Nucleic acids,
Carbohydrates
Natural organometalloids
Selenoproteins
Arsenosugars
Studies of bio-chemical
reaction mechanisms
The Significance of Speciation
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In the past, most analytical problems relating to
biological systems were addressed by measuring the
total concentrations of elements.
Now there is increasing awareness of the importance
of the chemical form in which an element is present in
biological systems, e.g., the oxidation state, the nature
of the ligands or even the molecular structure.
Information on speciation is critically required in order
to understand biological processes.
Mercury
Three forms, each with different toxicity
9 Elemental: Hg0
9 Inorganic: Hg+ (mercurous), Hg2+ (mercuric)
9 Organic: (e.g., methylmercury, ethylmercury,
dimethylmercury)
Why mercury?
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Hazardous properties of global relevance
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Impact at local, regional and global scale
Once mobilized Hg persists in the environment where it circulates
among air, water, sediments and biota
High toxicity, dependant on the chemical form, the pathway of
exposure, the amount and the vulnerability of persons exposed
Bioaccumulation and biomagnification
Human populations and ecosystems at risk
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General population primarily exposed to organic Hg through diet
and inorganic Hg through amalgams
Women (pregnant, child bearing age, lactating), children,
occupationally exposed, populations dependant on fish protein
Vulnerable ecosystems and wildlife (i.e. predators in aquatic and
terrestrial environments, arctic ecosystems), soil communities.
Natural mercury –planetary Hg belts
Mercury sources
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Natural vs. antropogenic
Significant increase of Hg
globally due to
anthropogenic activities
Most significant releases to
the atmosphere, also to
waters and land
Industrial and mining sites
Land, water and resource
management activities can
make Hg more bioavailable
Mercury waste
Global mercury emissions of Hg to air
Source: AMAP Norway
Modelling the global
transport of elemental
mercury:
Average elemental
mercury surface
concentrations
3)
20012269
(ng/m
emission:
tonnes
Categories - TotalJan
Stationary Combustion
5%1%
Cement Production
10%
Non-ferrous Metal Production
1%
3%
1%
Pig Iron & Steel Production
Caustic Soda Production
7%
5%
GRAHM (Global/Regional Atmospheric
Heavy Metals Model) simulation – Ashu
Dastoor, Meteorological Service of Canada,
Environment Canada
Mercury Production
67%
Gold Production
Waste Disposal
Other
July 2001 (ng/m3)
2004 EU mercury consumption (tonnes)
Electrical
control &
switching - O ther uses 25
22
Small-scale
gold mining 5
Chlor-alkali 105
Lighting - 21
M easuring
and control 22
Batteries - 10
Dental
amalgam - 70
Mercury uses:
Short-list of products & preparations containing Hg
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AntiAnti-fouling agents
AntiAnti-tamper devices of paypay-phones
Barometers
Batteries
Bubblers/traps (mercury)
CathodeCathode-ray oscilloscopes
Coulter Counters with manometers
DC wattwatt-hour meters
Diffusion pumps
Distillation salts
Dropping Mercury Electrode (DME) technique for
polarography and voltammeter
Fan and air vent controls
Fire alarms
Float switches (in bilge pumps, chemical feed
pumps, septic tanks, and sump pumps)
Fluorescent lights
Furnaces and heating systems
G-Sensor security systems use mercury in some
applications
Heating and ventilation equipment
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HighHigh-intensity discharge (HID) lamps
High voltage equipment
Hot water heaters
Household appliances
Lamps
Manometers for calibration
Natural gas powered equipment
Otoscopes
Pool alarms
pH meters
Plunger/displacement relays (see above chart)
Products containing preservatives (see chemical
sheet)
Rubber flooring
Security alarms (e.g. automotive, building and
computer)
Sequential Multiple Analyzers
Silent light switches
Steam recorders in boiler panels
Switching equipment for telecommunications
Temperature control or environmental testing
equipment
Thermometers
Thermostats
Thermostat probes
Tilt switches
Global environmental mercury budget
All fluxes in Tons/year
PRE-INDUSTRIAL
CURRENT
Atm. 1805 Ton
Atm. 5216 Ton 1.4%/y
0
Hgp
Hg
0
Hgp
0
100
3
401
802
802
Wet &Dry
Deposition
0
Mixed Layer
5817 Ton
Hgp
100m
+
Hg
CH3Hg
2+
Hg
0
+
Hg
Mixed Layer 1.5%/y
10832 Ton
O cea
Evas nic
ion
O c ea
Evas nic
ion
N
Em atur
iss al
ion
s
100
3
Wet &Dry
Deposition
60 2
7
Hg
Deposition Hg
6
200
220
98% Hg0
2% Hgp
2+
2+
Deposition Hg
08
26
N
Em atur
iss al
ion
s
c
ni
ge s
o
p
ro ion
th iss
An E m
98% Hg
2% Hgp
CH3Hg
2+
Hg
Hgp
100m
Upwelling
602
1000m
Particle
Removal
1805
Thermocline 0.4%/y
216648
Upwelling
602
1000m
Burial
Burial
401
401
Adopted from Lamborg et al. 2002
Particle
Removal
1003
Thermocline
180941
Release categories / control mechanisms
Natural
sources
and
re-mobilisation
of anthropogenic Hg
Releases beyond
human control
Hg
impurities
in raw
materials
Human and natural
environment
- reduce consumption
- use alternative raw materials
- “end-of-pipe” techniques
Hg used
internationally
in products &
processes
- reduce consumption
- improve recycling/recovery
- substitute product/processes
- “end-of-pipe” techniques
Trends in mercury emissions in Europe 1980 to 2000
Source category
1980
1985
1990
1995
2000
Combustion of fuels
350
296
195
186
114
Industrial processes
460
388
390
93
99
Other sources
50
42
42
59
26
TOTAL
860
726
627
338
239
Reductions of Hg emissions mainly due to: Flue Gas Desulphurisation, Closing of
obsolete chemical industries, modernisation of industries and power generation.
Emission reductions confirmed by measurements - Total
Gaseous Mercury at Swedish West Coast 1979 to 2002
14
Large influence from European emissions
and regional transport
12
TGM ng/m3
10
8
6
Mainly global sources
4
2
0
1979 1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002
Date
1000000
100000
10000
1000
100
10
1
air
water
soil/sediment
fish
Speciation of Hg
WATER
ATMOSPHERE
EVASION
Hg0(g)
Hg2+(g)
Hg0(g)
Hg0(ads)
DEPOSITION
Hg2+(aq)
Hg2+(ads)
Hg2+ and
MeHg
adsorbed
Hg0(aq)
(CH3)2Hg(g)
Hg2+(aq)
SEDIMENTATION
CH3Hg+
ANCIENT
300 BC 1500 AD
MODERN
Greenland
9
8
7
6
5
4
3
2
1
0
Canadian Arctic
Hg(ug/g)
Historical Increases in Hg
Concentration of Polar
Bear Fur
1300
1973-1977 1985-1994
Adapted from Dietz et al (2005)
Regional case study: Mercury mine, Idrija, Slovenia
Horvat et al., 2000
Biomonitoring:
rivers
Zizek et al., STOTEN, 2007
Critical population groups
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Inorganic Hg:
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Occupational exposure
vs. general population
(amalgam)
Certain genotype
(glomerulonephritis)
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MeHg:
„ women in childbearing
age
„ pregnant women
„ children
What is safe?
Maximum Levels (ML) in
mg/kg
Commission Regulation
(EC) No. 466/2001
Recommendations on
safe levels
Contaminated food and fish is the main source of exposure
What and why to measure?
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Total Hg
CH3Hg+, Hg2+, reactive Hg, other ionic species?
CH3HgCH3, Hg0 (air, water, gas, oil...)
Reactive gaseous Hg, total particulate Hg, Hg bound to
particulates, colloidal Hg, reactive Hg in water
Hg in organic molecules (e.g. proteins), Hg bound to
humic and fulvic acids, etc......
Partitioning and fluxes (soil/air, sediment/water,
vegetation/air, water/air)
Transformations ( methylation, demethylation, reduction,
oxidation, etc..)
Kinetics of uptake, distribution and release, retention,
biological effects
Inventories, mass balances, simulations of scenarios
MeHg
Analytical steps for determination of
MeHg in biota
Hg(II)
Hg(0)
Sample pretreatment
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Liberation of MeHg from its matrix
(acid leaching, alkaline dissolution, volatilization, distillation, superfluid extraction,
microwave assistance)
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Extraction/clean-up/preconcentration
(Solvent extraction, derivatization such as ethylation, buthylation, hydration and
iodination; cryogenic trapping; preconcentration on solid phases)
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Separation of mercury species of interest
(gas chromatography; HPLC; ion-exchange)
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Quantification
(CV AAS, CVAFS, GC-ECD, AED,MS, ICP-MS)
Mercury: Current issues
Analysis and speciation:
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Direct speciation methods
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Improved sensitivity and
specificity
On-line measurement techniques
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Tests for the field work
Fate and transport:
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Atmospheric chemistry and
partitioning,
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Modelling tools
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Biogeochemical cycling - mercury
transfer from emissions to
methylmercury in fish
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Global cycling - role of oceans,
forests etc...
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Health:
Reduction of human and wildlife
exposure
Biomarkers of exposure, effects
and susceptibility
Improvements in risk analysis
Environmental technologies:
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Remediation of contaminated sites
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Reduction of emissions, costefficiency
Alternatives: processes and
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products
Policy response:
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Legal instruments
Voluntary (partnership
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programmes)