Isomerspecific determination of sorption/desorption, transformation and bioaccumulation of hexachlorocyclohexanes at the case site Bitterfeld with special regard to ageing effects

The production of hexachlorocyclohexanes (HCHs) at Bitterfeld, Germany, caused heavy contamination of sediments in the receiving waters and soils of riverbanks and floodplains of the Spittelwasser creek with adverse effects on the rivers Mulde and Elbe. This study was launched to investigate the isomer specific behaviour of aged and non-aged hexachlorocyclohexanes focusing on their transformation, sorption and bioaccumulation. Spiked residues of α- and γ-HCH were transformed in aerobic water/sediment systems, while no elimination was observed for β-, δ- and ε-HCH. In contrast, aged residues of all HCH isomers were entirely stable under these aerobic conditions, while under anaerobic conditions a significant transformation was found for all spiked HCH isomers. Desorption hysteresis was identified for all isomers. Ageing led to an increase in the binding strength of HCH isomers to sediment, indicated by elevated logKOC-values and increased the persistence of HCH isomers in aerobic water/sediment systems. HCH bioaccumulated in benthic organisms of Spittelwasser creek and Schachtgraben canal. After their confluence the lipid normalised HCH concentrations in benthic organisms of Spittelwasser creek increased by a factor of 10, indicating the central role of HCH residues from the Schachtgraben canal for the HCH exposure of benthic biota in the aquatic system of the Spittelwasser creek.