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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. Outline. POPs and CSIA

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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


Outline
Outline Process Identification of Selected POPs by CSIA

  • POPs and CSIA

  • Study Approach

  • Source Identification for POPs in the Environment

  • Isotopic Fractionation during Photolysis Process of POPs

  • Conclusion


POPs Process Identification of Selected POPs by CSIA

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)


(‰) Process Identification of Selected POPs by CSIA

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).


EA Process Identification of Selected POPs by CSIA

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)


Application of CSIA in Environmental Science Process Identification of Selected POPs by CSIA

  • 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…


Aim of this study Process Identification of Selected POPs by CSIA

  • 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.


Outline1
Outline Process Identification of Selected POPs by CSIA

  • POPs and CSIA

  • Study Approach

  • Source Identification for POPs in the Environment

  • Isotopic Fractionation during Photolysis Process of POPs

  • Conclusion


GC-C-IRMS FOR PAHs, OCPs, and PCBs standard Process Identification of Selected POPs by CSIA


Low Signal and UCM Encountered in CSIA Application Process Identification of Selected POPs by CSIA

Signal is too low (<Detection limit)

Unresolved Complex Mixture (UCM)


Clean up by dmf pentane biphasic system lle
Clean up Process Identification of Selected POPs by CSIA 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.


The result of LLE Clean up for Sediment Sample Process Identification of Selected POPs by CSIA


LOD, Recovery, RSD of POPs for CSIA Process Identification of Selected POPs by 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 .


Outline2
Outline Process Identification of Selected POPs by CSIA

  • POPs and CSIA

  • Study Approach

  • Source Identification for POPs in the Environment

  • Isotopic Fractionation during Photolysis Process of POPs

  • Conclusion


UCM Removed by DMF-Pentane biphasic system Process Identification of Selected POPs by CSIA


-26.2 Process Identification of Selected POPs by CSIA~-23.7‰

Source Identified by Compound Specific Isotope Analysis(CSIA)


Outline3
Outline Process Identification of Selected POPs by CSIA

  • POPs and CSIA

  • Study Approach

  • Source Identification for POPs in the Environment

  • Isotopic Fractionation during Photolysis Process of POPs

  • Conclusion


Isotope Fractionation for Compound during Reaction Process Process Identification of Selected POPs by CSIA

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)



Photochemical degradation of HCB in hexane photolysis Process of PCBs

t1/2 = 387min, r = 0.997

t1/2 = 387min, r = 0.997

t1/2 = 394min, r = 0.997



HCB photochemical process at different time photochemical process

t=600min

t=0min

t=1200min


δ photochemical process13C values for HCB in different concentration


The δ photochemical process13C value of HCB and PCB versus percent conversion


δ photochemical process13C value of the residual HCB versus fraction remaining

ε= -14.8

n=28, r=0.96


δ photochemical process13C value of the product PCB versus fraction producing

ε = 22.7

n=14, r=0.84


Isotope Fractionation for Compound during Reaction Process photochemical 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)


Outline4
Outline photochemical process

  • POPs and CSIA

  • Study Approach

  • Source Identification for POPs in the Environment

  • Isotopic Fractionation during Photolysis Process of POPs

  • Conclusion


Conclusion
Conclusion photochemical process

  • 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.


Thank You! photochemical process


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