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Preliminary study on Source Apportionment and Photolysis Process Identification of Selected POPs by CSIA

Preliminary study on Source Apportionment and Photolysis Process Identification of Selected POPs by CSIA. Z.L. Zhang, G. Yu, J. Cheng, X. Wang, J.L. Zhou Center for Environmental Research, University of Sussex, UK POPs Research Center, Tsinghua University, China. Outline. POPs and CSIA

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Preliminary study on Source Apportionment and Photolysis Process Identification of Selected POPs by CSIA

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  1. Preliminary study on Source Apportionment and Photolysis Process Identification of Selected POPs by CSIA Z.L. Zhang, G. Yu, J. Cheng, X. Wang, J.L. Zhou Center for Environmental Research, University of Sussex, UK POPs Research Center, Tsinghua University, China

  2. Outline • POPs and CSIA • Study Approach • Source Identification for POPs in the Environment • Isotopic Fractionation during Photolysis Process of POPs • Conclusion

  3. POPs Persistent Organic Pollutants (POPs) are defined as ‘a set of organic compounds that: (i) posses toxic characteristics; (ii) are persistent; (iii) are liable to bioaccumulate; (iv) are prone to long-range atmospheric transport and deposition; (v) can result in adverse environmental and human health effects at locations near and far from their sources’ Dirty Dozen: Aldrin, Endrin, Dieldrin, DDT, Chlordane, Hexachlorobenzene, Heptachlor, Mirex, Toxaphene, PCBs, PCDDs and PCDFs Relative Candidates: PAHs, Hexchlorohexane(HCH), PBDEs... Source: Convention on Long-Range Transboundary Air Pollution (CLRTAP), a protocol on persistent organic pollutants (POPs) under the auspices of the United Nations Economic Commission for Europe (UN-ECE)

  4. (‰) Compound Specific Stable Isotope Analysis(CSIA) • Compound Specific Stable Isotope Analysis(CSIA) is an analytical Method which using Gas Chromatography-Isotope Ratio Mass Spectrometry (GC/IRMS) was developed in many application areas over the last decades. • Carbon: Radioactive Isotope-14C; Stable Isotope-12C(99.89%),13C(0.11%). Stable Isotopic composition expressed as δvalues in per mil (‰) Eq(1), Definition ： where RA and Rst are the ratios of heavy isotope to the light isotope(R=13C/12C) in compound X and international standard(usually Vienna Peedee Belemnite, VPDB).

  5. EA CO2 BSIA Sample µmol d13C Bulk Sample IRMS 950°C V.S. GC Separation of all individual compounds GC/CIII CO2 CO2 CO2 Sample nmol IRMS CSIA GC 950°C d13C of all Individual Compounds Compound Specific Isotope Analysis(CSIA)

  6. Application of CSIA in Environmental Science • Allocate and distinguish sources of organic compounds on a local, regional, and global scale. e.g.PAHs, PCBs source apportionment… • Identify and quantify transformation process, characterize of elementary reaction mechanisms that govern product formation. e.g. microbial degradation process identification…

  7. Aim of this study • To develop sample pretreatment method for CSIA analysis organic pollutants in environmental matrices. • Apply the developed method for CSIA to identify the selected POPs sources • Investigate isotope fractionation by CSIA during the photolysis of selected POPs, to explore it as a potential tool for monitoring the photodegradation process.

  8. Outline • POPs and CSIA • Study Approach • Source Identification for POPs in the Environment • Isotopic Fractionation during Photolysis Process of POPs • Conclusion

  9. GC-C-IRMS FOR PAHs, OCPs, and PCBs standard

  10. Low Signal and UCM Encountered in CSIA Application Signal is too low (<Detection limit) Unresolved Complex Mixture (UCM)

  11. Clean up by DMF-Pentane biphasic system (LLE) 95%DMF H2O HEX DMF HEX PET Cu、N2 PET HEX+ DCM Hex/DCM PSE Principle：DMF (Dimethylformamide) –Pentane(PET) biphasic system，PAHs、PCBs etc. are easy to stay in DMF phase，the UCM will be removed from the system by affinity to pentane.

  12. The result of LLE Clean up for Sediment Sample

  13. LOD, Recovery, RSD of POPs for CSIA a LOD1、LOD2 are calculated for LOD of POPs- POPs-δ13C by equation C = M /（LNc）、C ＝（S-b）/ k ＝（100-b）/ k respectively .

  14. Outline • POPs and CSIA • Study Approach • Source Identification for POPs in the Environment • Isotopic Fractionation during Photolysis Process of POPs • Conclusion

  15. UCM Removed by DMF-Pentane biphasic system

  16. -26.2~-23.7‰ Source Identified by Compound Specific Isotope Analysis(CSIA)

  17. Outline • POPs and CSIA • Study Approach • Source Identification for POPs in the Environment • Isotopic Fractionation during Photolysis Process of POPs • Conclusion

  18. Isotope Fractionation for Compound during Reaction Process Rayleigh equation : Rt/Ro = f (α-1) …… （2） α: isotope fractionation factor ; Rt and Ro are the isotope compositions, f is the fraction of substrate remaining (f) which equals to Ct/Co, and Ct and Co are the concentrations of the compound at times t and zero, respectively. ε=(α-1)×1000 ……（3） ε: enrichment factor ln（(10-3×δ13Ct+1)/(10-3×δ13 Co)）＝（α-1）×lnf ……（4）

  19. Primarily Observed Carbon Isotope Effect Occurred in the photolysis Process of PCBs

  20. Photochemical degradation of HCB in hexane t1/2 = 387min, r = 0.997 t1/2 = 387min, r = 0.997 t1/2 = 394min, r = 0.997

  21. Relative conversion and Mass balance over time for photochemical process

  22. HCB photochemical process at different time t=600min t=0min t=1200min

  23. δ13C values for HCB in different concentration

  24. The δ13C value of HCB and PCB versus percent conversion

  25. δ13C value of the residual HCB versus fraction remaining ε= -14.8 n=28, r=0.96

  26. δ13C value of the product PCB versus fraction producing ε = 22.7 n=14, r=0.84

  27. Isotope Fractionation for Compound during Reaction Process Rt/Ro = f (α-1) …… （2） α: isotope fractionation factor ; Rt and Ro are the isotope compositions, f is the fraction of substrate remaining (f) which equals to Ct/Co, and Ct and Co are the concentrations of the compound at times t and zero, respectively. ε=(α-1)×1000 ……（3） ε: enrichment factor ln（(10-3×δ13Ct+1)/(10-3×δ13 Co)）＝（α-1）×lnf ……（4）

  28. Outline • POPs and CSIA • Study Approach • Source Identification for POPs in the Environment • Isotopic Fractionation during Photolysis Process of POPs • Conclusion

  29. Conclusion • The method of CSIA applied in POPs study is primarily established, include sample pretreatment and the related analytical properties. • In identifying the source of POPs, CSIA is primarily applied in PAHs source apportionment. • Isotopic Fractionation during Photolysis Process of HCB indicated that CSIA might serve as a potential tool to monitor the photo-chemical process for POPs in environment.

  30. Thank You!

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