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

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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

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Outline

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

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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)
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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 dvalues in per mil ()
• Eq(1), Definition
• where RA and Rst are the ratios of heavy isotope
  to the light isotope(R13C/12C) in compound X and
  international standard(usually Vienna Peedee
  Belemnite, VPDB).

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Compound Specific Isotope Analysis(CSIA)
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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

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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.

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Outline

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

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GC-C-IRMS FOR PAHs, OCPs, and PCBs standard
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Low Signal and UCM Encountered in CSIA Application
Signal is too low (ltDetection limit)
Unresolved Complex Mixture (UCM)
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Clean up by DMF-Pentane biphasic system (LLE)
HEX
PET
Cu?N2 PET
HEX DCM
Hex/DCM PSE
PrincipleDMF (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.
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The result of LLE Clean up for Sediment Sample
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LOD, Recovery, RSD of POPs for CSIA
a LOD1?LOD2 are calculated for LOD of POPs-
POPs-d13C by equation C M /(LNc)?C (S-b)/ k
(100-b)/ k respectively .
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Outline

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

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UCM Removed by DMF-Pentane biphasic system
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Source Identified by Compound Specific Isotope
Analysis(CSIA)
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Outline

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

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Isotope Fractionation for Compound during
Reaction Process
Rayleigh equation Rt/Ro f (a-1)
(2) a 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.
e(a-1)1000 (3) e enrichment
factor ln((10-3d13Ct1)/(10-3d13 Co))(a-1)lnf
(4)
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Primarily Observed Carbon Isotope Effect Occurred
in the photolysis Process of PCBs
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Photochemical degradation of HCB in hexane
t1/2 387min, r 0.997
t1/2 387min, r 0.997
t1/2 394min, r 0.997
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Relative conversion and Mass balance over time
for photochemical process
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HCB photochemical process at different time
t600min
t0min
t1200min
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d13C values for HCB in different concentration
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The d13C value of HCB and PCB versus percent
conversion
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d13C value of the residual HCB versus fraction
remaining
e -14.8 n28, r0.96
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d13C value of the product PCB versus fraction
producing
e 22.7 n14, r0.84
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Isotope Fractionation for Compound during
Reaction Process
Rt/Ro f (a-1) (2) a 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. e(a-1)1000
(3) e enrichment factor ln((10-3d13Ct1)/(10-3
d13 Co))(a-1)lnf (4)
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Outline

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

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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.

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Thank You!