Compound-specific stable chlorine isotope analysis : A versatile tool for investigating biochemical and geochemical processes of organochlorine substances
Abstract: Chlorinated organic compounds (OCls) from anthropogenic sources are generally considered to be a class of chemicals with high potential for ecotoxicity, including infamous substances such as polychlorinated biphenyls (PCB), dichloro-dibenzo-trichloroethane (DDT) and polychlorinated dibenzo-p-dioxins (PCDD). OCls are also produced naturally, sometimes at the same order of magnitude as anthropogenic compounds. The scope of this thesis was to develop and apply a method for isotope analysis of OCls, as a part of compound-specific chlorine isotope analysis (CSIA-?37Cl) of trace level compounds. Isotope analysis of chlorine was performed with sealed-tube combustion and thermal-ionization mass spectrometry (TIMS), in order to improve the analytical sensitivity by a factor 20 relative to conventional techniques. Chlorine isotope signatures of organochlorines (?37Cl-OCl) can be used for source apportionment in the natural vs. anthropogenic spectrum. CSIA-?37Cl was tested as a tool to resolve the origin of putatively natural PCDD found in ball clay from the Mississippi Embayment, USA. Combined with results from 14C analysis, the ?37Cl-PCDD was consistent with a natural abiotic formation of PCDD. Reactions involving the scission of a chemical bond to a molecular chlorine substituent will induce a shift in the ?37Cl-OCl of the remaining reactant. This concept was used to calculate the undegraded fraction of DDT in the Baltic marine environment (~7% DDT remaining) based on ?37Cl-OCl measurements of DDT harvested from seal blubber. Hence, it is suggested that CSIA-?37Cl may be very useful in studies of fate and origin of OCls in the environment, and that further applications of the technique are warranted.
This dissertation MIGHT be available in PDF-format. Check this page to see if it is available for download.