The use of radio-isotope tracing in studying the
fate of organic pollutants in the environment
Vassilis Kouloumbos - Biology V, RWTH Aachen
AQUAbase workshop on Analytical Methods, 18.01.2006
Contents …
fate of organic pollutants
Topic
Difficulties
radio-isotope tracing
Principle / Advantages
Applications
Disadvantages
Conclusions
Fate of organic pollutants in the environment
fate = transport + transformation
Difficulties in environmental fate studies: complex matrix
“ Accumulation of PAHs on the leaves of pear (Pyrus calleryana) ”
extraction with 2M KOH in MeOH/H2O
filtering through porcelain filter
dilution with water, partition extraction
3 times with hexane
washing with water
Jouraeca et al., 2002
Kömp et al., 1997
drying with Na2SO4 overnight
evaporation to 1ml
addition of internal standard
clean-up on a Silica gel column
evaporation by N2 gas
analysis by GC-MS (SIM mode)
complex matrix Æ thorough preparation is needed before analysis
Difficulties in environmental fate studies: lack of mass balance
“ Chlordane uptake and its translocation in food crops ”
air sampling
vegetation extraction
soil extraction
Mattina et al., 2000
amount of non extractable residues?
amount of transformation products?
quantification of technical mixture?
?
mass balance is missing
Difficulties in environmental fate studies: unclear conversion pathway
“ Degradation of alachlor in natural and sludge-amended soils ”
soil extract
?
GC-MS
LC-MS (SIM)
Rodruigez-Cruz et al., 2005
complex matrix Æ not easy to detect transformation products
difficult to establish the conversion mechanisms
Difficulties in environmental fate studies: an overview
complex matrix of
environmental media
non analyzable
fractions
Complicated preparation
procedures
Bound residues not
determined
High detection limits
Distinction between losses
and bound residues difficult
Need for high spiking levels
Analysis of some
compartments impossible
cycles of matter
Evidences for conversion
pathways / mechanisms are
weak or non existent
Distinction between natural
and freshly spiked
contaminants not possible
Quantification without
standards usually impossible
Interaction between pollutants
and natural media non
observable
Mass balance is missing
The experiment of Hevesy
1913
Frederick Soddy formulates the concept of isotopes.
“atoms of the same elements, with
identical outsides but different insides”
12
6
C
14
6
C
Isotope: An atomic nucleus having the same number of protons as a more
commonly found atomic nucleus but a different number of neutrons.
Radio-isotope: An unstable isotope of an element that decays or disintegrates
spontaneously, emitting radiation.
1923
George de Hevesy employs 212Pb as a radioactive tracer, the
first such use of a radioactive isotope.
207
Pb2+
212
Pb2+
1934
Irene and Frederic Joliot-Curie create the first artificiallyradioactive isotope (30P). Enrico Fermi demonstrates that
is possible to produce radioactive isotopes from any
element by bombarding it with particles.
Principle and advantages of radio-isotope tracing
Radio-isotopes
3
1
H
14
6
C
32
15
P
33
15
P
35
16
S
radiation: β particles (e-)
t1/2
12y
5730y
14d
25d
87d
Radio-isotope tracing
Principle:
The active atoms are recognized by their radiation and, being faithful companions
of the inactive atoms of an element, they serve as markers for them.
Advantages:
• high specificity
• high sensitivity
• simplicity in the techniques involved
• interpretation of processes at an atomic level
How radio-labeled organic compounds are obtained
1. Radioisotopes are formed by nuclear reactions on targets in a reactor
or cyclotron:
(AlN)
14
7
1
N + 0n
Æ
14
6
C + 1p
1
2. “Naked” radioisotopes require further processing in almost all cases to
obtain them in a form suitable for use:
14
6
C - - - Æ Ba CO3
14
3. Radiolabelled compounds are synthesized by appropriate radiochemical
organic synthesis reactions:
OH
OH
14
Ba CO3
---Æ
---Æ
H19C9
Analytical methods for detecting radio-labeled compounds
> Gas-filled detectors
Geiger-Müller detector
> Autoradiography (e.g. for Thin Layer Chromatography)
> Scintillation detectors
Liquid Scintillation Counting (LSC)
radioactive molecule
liquid
scintillation
cocktail
fluor molecule
solvent + emulsifier
HPLC-UV/LSC
Catalytic sample oxidizer
237 8
dpm
Applications of radio-isotope tracing: general fate
“ Fate of nonylphenol (NP) in soil ”
OH
OH
NP extraction from soil: recovery determination
LSC
H19C9
H19C9
Incubation of NP spiked soil: total residues determination
CO2
LSC
Oxidizer
Incubation of NP spiked soil: losses (NP volatilization, volatile conversion products)
EtGl
NaOH
pump
volatiles
LSC
CO2
Incubation of NP spiked soil: detection of conversion products
soil extract
HPLC-UV/LSC
Applications of radio-isotope tracing: assimilation by microorganisms
“ Metabolism of the nonylphenol (NP) by Sphingomonas TTNP3 ”
CO2
Sphingomonas culture
extraction
(EtAc)
org. phase
biomass
filtering
aq. phase
filtrate
+
[NP + NP]
org. phase
biomass
Corvini et al., 2004
aq. phase
CO2
Applications of radio-isotope tracing: type of bound residues
“ Binding of p-coumaric acid to soil humic acids ”
CO2
precipitation of
humic acids
(acidification)
p-coumaric acid
14C
centrifugation
humic acids
pellet
supernatant
p-coumaric acid
humic acids
redissolving
(NaOH)
humic acids
bound
p-coumaric
acid
HPLC-UV/LSC
Li et al., under preparation
Applications of radio-isotope tracing: transformation pathways
“ Metabolism of dimethoate in plants and animals ”
dimethoate
14C
dimethoate
32P
dimethoate
Dauterman et al., 1960
Hacskaylo et al., 1963
Lucier, 1967
Applications of radio-isotope tracing: mechanisms of transport
“ Transport of PCB compounds from sediment to water and from
water to air in laboratory model systems ”
jet drops
Tefflon collector
air
jet drops
glass surface
water
soil upper layer
soil middle layer
soil bottom layer
macroinvertebrates
invertebrates
Most of the PCBs added were found on the upper sediment.
Larsson, 1982
PCBs dissolved in water are absorbed to the bubbles rising
through the water column.
The bioturbation effect caused a transport of particles
from the sediment to water.
Most of these particles adhered to the walls of the glass
tube…
Applications of radio-isotope tracing: fate during sewage treatment processes
% Applied radioactivity
“ Fate of nonylphenol (NP) in a lab-scale membrane bioreactor (MBR) ”
effluent radioactivity
Time (days)
Cirja et al., under preparation
absorption on
sludge
MBR
volatilized
CO2
sludge excess
(cumulative)
effluent (cumulative)
Disadvantages of using radio-isotopes as tracers
• harmful effects of ionizing radiation to humans and environment
• possible lack of control over experimental conditions
• production of radioactive waste
• safety requirements – laboratory practice
• costs for labeling and waste disposal
McGill University, Canada
Conclusions
Use of radio-isotope tracing
in environmental fate studies
Practical advantages
Simplicity – Accuracy – Sensitivity on analyses
Mass balance for pollutants
Deep interpretation of processes
Disadvantages
Health and environment risk
Radioactive waste
Laboratory practice
Associated costs
Acknowledgments
Philippe Corvini
Andreas Schäffer
Rong Ji
Chengliang Li
Magdalena Cirja