A concept for studying the transformation reaction of hexachlorocyclohexanes in food webs using multi-element compound-specific isotope analysis.

An analytical concept using stable isotope fractionation for analyzing persistent organic pollutants (POPs) in food webs was developed and tested. We have evaluated methods for the extraction and clean-up of hexachlorocyclohexane isomers (HCHs) as the model compounds of POPs from water, soil, plant, milk, fish oil and pork liver in order to study the reactive transport processes of HCHs in food webs using multi-element compound-specific isotope analysis (CSIA). The extraction and clean-up methods were evaluated for recovery efficiency and isotope effects. The precision and accuracy for carbon, hydrogen and chlorine isotope analysis were within the analytical precision of ±0.5‰, ±5‰ and ±0.3‰, respectively. The method was applied for stable isotope analysis of HCHs in possible food webs from soil to plants, and to animals. Isotope compositions of HCHs in cow/buffalo milk and dung, wild animal livers and seal blubber were obtained and compared to the sources of HCHs. The magnitude of isotope enrichment demonstrated the potential of CSIA for analyzing reactive transport processes of HCHs in the food web. The concept using multi-element stable isotope analysis can be applied for source identification, characterization of degradation mechanisms, and particularly contaminant accumulation in the food web, which demonstrates the potential in new scientific areas for CSIA.