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The Enantioselective Bioaccumulation of Chiral Chlordane and -HCH Contaminants in the Polar Bear Food Chain
Umeå University, Faculty of Science and Technology, Chemistry.
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2000 (English)In: Environmental Science & Technology, Vol. 34, no 13, 2668-74 p.Article in journal (Refereed) Published
Abstract [en]

The enantiomer ratios (ERs) of -HCH and chlordane related compounds (CHLs) were examined in the polar bear food chain (arctic cod-ringed seal-polar bear), using chiral gas chromatography-mass spectrometry (GC-MS). The cod showed near-racemic mixtures (ER = 1) for most of the compounds. In contrast, ERs in ringed seal and polar bear were frequently nonracemic (ER 1), due to enantiomer-specific biotransformation. As (+)--HCH was transferred up the food chain, it became more abundant relative to (-)--HCH. For the CHLs, there was no uniform trend for the ER changes and the increasing trophic level. Apparent chiral biomagnification factors (BFs) were calculated and up to a 20-fold difference in the BF between enantiomers was found. Analysis of chiral BFs relative to CB-153 indicated that oxychlordane was formed by ringed seal and metabolized by polar bears. However, the ERs did not change significantly as a result of these biotransformations. Multivariate statistical methods revealed the clustering of sample categories and were used to investigate the relationships between the ERs, chemical residue concentrations, and biological data. ERs were important variables for the sample groupings and for the class separation of male/female seals and fat/liver tissues. The variance in the cytochrome P450 CYP2B protein content of bear liver could be explained by the variances in chemical residue data. In this analysis the ERs were of secondary importance. The ERs of some highly recalcitrant CHLs in polar bear adipose showed linear relationships with the age of the bears.

Place, publisher, year, edition, pages
2000. Vol. 34, no 13, 2668-74 p.
URN: urn:nbn:se:umu:diva-8945DOI: doi:10.1021/es990740bOAI: diva2:148616
Available from: 2008-02-22 Created: 2008-02-22 Last updated: 2012-06-28Bibliographically approved
In thesis
1. Enantiospecific Analysis and Environmental Behavior of Chiral Persistent Organic Pollutants (POPs)
Open this publication in new window or tab >>Enantiospecific Analysis and Environmental Behavior of Chiral Persistent Organic Pollutants (POPs)
2002 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Many persistent organic pollutants (POPs) are chiral. These pollutants are generally released into the environment as racemates, but frequently undergo alterations in enantiomeric composition as soon as they are subjected to life chemistry processes. Enantiospecific analysis of chiral POPs is important since enantiomers of chiral compounds often exhibit differences in biological activity, and most biochemical processes in nature are stereospecific. For abiotic processes, such as air-water gas exchange, deposition and long-range air transport, enantiomeric patterns of POPs may be used as chemical markers.

The aim of the work described in this thesis was to improve our knowledge about the presence and fate of enantiomers of chiral POPs inthe environment to provide a sound basis for accurate risk assessment. The compounds included were organochlorine (OC) pesticides (α-HCH, chlordanes and o,p’-DDT), atropisomeric PCBs and some of their respective metabolites (heptachlor-exo-epoxide, oxychlordane and MeSO2-PCBs).

Analytical methods for chiral PCBs were developed, and the elution sequences of (+) and (−)-enantiomers were determined. Enantiomeric fraction (EF) was proposed as a better reflector of chiral composition than the conventional enantiomeric ratio (ER).

Enantioselective bioprocessing in various compartments was studied, with the main emphasis on factors controlling chiral composition in biota Correlations were detected between changes in EFs and differences in trophic levels. The changes were, however, not consistent for all compounds. Instead, the enantiomeric composition was found to be species-specific in the polar bear food chain and in aquatic species from the Baltic Sea. The EFs of some POPs in Baltic seals were related tonutritional status and biotransformation capacity.

Enantiomeric and isomeric patterns were used to investigate abiotic processes in the southern Baltic Sea environment and EFs were used tostudy soil as a source of atmospheric heptachlor-exo-epoxide.

90 p.
urn:nbn:se:umu:diva-9 (URN)91-7305-162-4 (ISBN)
Public defence
Available from: 2002-01-25 Created: 2002-01-25 Last updated: 2012-06-28Bibliographically approved

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Wiberg, KarinTysklind, Mats
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