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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 Difficulties Principle / Advantages Applications Disadvantages Conclusions fate of organic pollutants radio-isotope tracing

Fate of organic pollutants in the environment fate = transport + transformation

Difficulties in environmental fate studies: complex matrix

extraction with 2M KOH in MeOH/H2O filtering through porcelain filter dilution with water, partition extraction 3 times with hexane washing with water 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)

“ Accumulation of PAHs on the leaves of pear (Pyrus calleryana) ”

Jouraeca et al., 2002 Kömp et al., 1997

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 ”

Mattina et al., 2000

air sampling vegetation extraction soil extraction 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 ”

Rodruigez-Cruz et al., 2005

? soil extract GC-MS LC-MS (SIM) not easy to detect transformation products complex matrix difficult to establish the conversion mechanisms

Difficulties in environmental fate studies: an overview complex matrix of environmental media non analyzable fractions cycles of matter

Complicated preparation procedures High detection limits Need for high spiking levels Bound residues not determined Distinction between losses and bound residues difficult Analysis of some compartments impossible 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

• bservable

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”

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.

George de Hevesy employs 212Pb as a radioactive tracer, the first such use of a radioactive isotope.

C C

6 6 14 12 207

Pb2+

212

1934

Irene and Frederic Joliot-Curie create the first artificially- radioactive isotope (30P). Enrico Fermi demonstrates that is possible to produce radioactive isotopes from any element by bombarding it with particles.

1923

Pb2+

Principle and advantages of radio-isotope tracing Radio-isotopes

C

6 14

H

1 3

P

15 32

P

15 33

S

16 35

12y 5730y 14d 25d 87d radiation: β particles (e-) t1/2 The active atoms are recognized by their radiation and, being faithful companions

• f the inactive atoms of an element, they serve as markers for them.

Principle: Advantages:

• high specificity
• high sensitivity
• simplicity in the techniques involved
• interpretation of processes at an atomic level

Radio-isotope tracing

How radio-labeled organic compounds are obtained

• 1. Radioisotopes are formed by nuclear reactions on targets in a reactor
• r cyclotron:

N + n C + p

7 14 1 6 14 1 1

(AlN)

• 2. “Naked” radioisotopes require further processing in almost all cases to
• btain them in a form suitable for use:

C

6 14

• - -

Ba CO3

14

• 3. Radiolabelled compounds are synthesized by appropriate radiochemical
• rganic synthesis reactions:

Ba CO3

14

• - -

OH

• - -

OH H19C9

Analytical methods for detecting radio-labeled compounds Liquid Scintillation Counting (LSC) radioactive molecule fluor molecule solvent + emulsifier liquid scintillation cocktail 2 3 7 8 dpm > Gas-filled detectors

Geiger-Müller detector

> Scintillation detectors > Autoradiography (e.g. for Thin Layer Chromatography) HPLC-UV/LSC Catalytic sample oxidizer

Applications of radio-isotope tracing: general fate “ Fate of nonylphenol (NP) in soil ”

Oxidizer

OH H19C9 OH H19C9 LSC volatiles CO2 LSC NP extraction from soil: recovery determination Incubation of NP spiked soil: total residues determination Incubation of NP spiked soil: losses (NP volatilization, volatile conversion products) Incubation of NP spiked soil: detection of conversion products soil extract

HPLC-UV/ LSC EtGl NaOH pump

CO2 LSC

Applications of radio-isotope tracing: assimilation by microorganisms Corvini et al., 2004 “ Metabolism of the nonylphenol (NP) by Sphingomonas TTNP3 ” CO2 biomass

• rg. phase
• aq. phase

Sphingomonas culture + [NP + NP] biomass filtrate

• rg. phase
• aq. phase

extraction (EtAc) CO2 filtering

Applications of radio-isotope tracing: type of bound residues “ Binding of p-coumaric acid to soil humic acids ” Li et al., under preparation p-coumaric acid

14C p-coumaric acid

centrifugation supernatant humic acids pellet precipitation of humic acids (acidification) CO2 redissolving (NaOH) humic acids

HPLC-UV/ LSC

humic acids bound p-coumaric acid

Applications of radio-isotope tracing: transformation pathways dimethoate

14C dimethoate 32P dimethoate

“ Metabolism of dimethoate in plants and animals ” Dauterman et al., 1960 Hacskaylo et al., 1963 Lucier, 1967

Applications of radio-isotope tracing: mechanisms of transport

macroinvertebrates

jet drops Tefflon collector air glass surface water soil upper layer soil middle layer soil bottom layer jet drops invertebrates “ Transport of PCB compounds from sediment to water and from water to air in laboratory model systems ” 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… Most of the PCBs added were found on the upper sediment.

Applications of radio-isotope tracing: fate during sewage treatment processes “ Fate of nonylphenol (NP) in a lab-scale membrane bioreactor (MBR) ” Cirja et al., under preparation effluent (cumulative) CO2 sludge excess (cumulative) volatilized sludge absorption on MBR

Time (days) % Applied radioactivity

effluent radioactivity

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