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 … Topic fate of organic pollutants 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/H 2 O filtering through porcelain filter dilution with water, partition extraction 3 times with hexane washing with water drying with Na 2 SO 4 overnight Jouraeca et al., 2002 evaporation to 1ml Kömp et al., 1997 addition of internal standard clean-up on a Silica gel column evaporation by N 2 gas analysis by GC-MS (SIM mode) complex matrix � 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? mass balance is missing amount of transformation products? ? quantification of technical mixture?
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 � not easy to detect transformation products difficult to establish the conversion mechanisms
Difficulties in environmental fate studies: an overview complex matrix of non analyzable cycles of matter environmental media fractions Complicated preparation Bound residues not Evidences for conversion procedures determined pathways / mechanisms are weak or non existent Distinction between losses High detection limits Distinction between natural and bound residues difficult and freshly spiked Need for high spiking levels Analysis of some contaminants not possible compartments impossible Quantification without standards usually impossible Interaction between pollutants and natural media non observable Mass balance is missing
The experiment of Hevesy Frederick Soddy formulates the concept of isotopes. 1913 “atoms of the same elements, with 14 12 C C identical outsides but different insides” 6 6 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 212 Pb as a radioactive tracer, the first such use of a radioactive isotope. 207 Pb 2+ 212 Pb 2+ 1934 Irene and Frederic Joliot-Curie create the first artificially- radioactive isotope ( 30 P). 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 14 3 32 33 35 C H P P S 6 1 15 15 16 radiation: β particles (e - ) t 1/2 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: N + n � C + p 14 1 14 1 (AlN) 7 0 6 1 2 . “Naked” radioisotopes require further processing in almost all cases to obtain them in a form suitable for use: - - - � 14 14 C Ba CO 3 6 3 . Radiolabelled compounds are synthesized by appropriate radiochemical organic synthesis reactions: OH OH - - - � - - - � 14 Ba CO 3 H 19 C 9
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 fluor molecule scintillation solvent + emulsifier 2 3 7 8 dpm cocktail HPLC-UV/LSC Catalytic sample oxidizer
Applications of radio-isotope tracing: general fate “ Fate of nonylphenol (NP) in soil ” NP extraction from soil: recovery determination OH OH LSC H 19 C 9 H 19 C 9 Incubation of NP spiked soil: total residues determination LSC CO 2 Oxidizer Incubation of NP spiked soil: losses (NP volatilization, volatile conversion products) EtGl NaOH pump volatiles LSC CO 2 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 ” CO 2 org. phase extraction biomass (EtAc) filtering aq. phase Sphingomonas culture filtrate + [NP + NP] aq. phase org. phase biomass CO 2 Corvini et al., 2004
Applications of radio-isotope tracing: type of bound residues “ Binding of p-coumaric acid to soil humic acids ” CO 2 precipitation of centrifugation humic acids (acidification) humic acids supernatant p-coumaric acid pellet 14 C p-coumaric acid redissolving (NaOH) humic acids 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 14 C dimethoate 32 P 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 ” air jet drops jet drops Tefflon collector glass surface water soil upper layer soil middle layer soil bottom layer invertebrates macroinvertebrates Most of the PCBs added were found on the upper sediment. 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 Larsson, 1982 tube…
Applications of radio-isotope tracing: fate during sewage treatment processes “ Fate of nonylphenol (NP) in a lab-scale membrane bioreactor (MBR) ” effluent radioactivity sludge excess % Applied radioactivity absorption on sludge MBR (cumulative) Time (days) volatilized effluent (cumulative) CO 2 Cirja et al., under preparation
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
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