Organochlorine Compounds in the North-western Black Sea Water: Distribution and Water Column Process

Individual polychlorobiphenyl (PCB) congeners (IUPAC Nos 28, 52, 101, 118, 149, 153, 138, 180, 187 and 170), dichlorodiphenylethanes (DDTs), hexachlorocyclohexanes (HCHs), hexachlorobenzene(HCB) and dieldrin were determined in 37 samples (25 surficial and three vertical profiles) of suspended particulate matter (>0·7 m) (SPM) and 10 dissolved phase (DP) samples (six surficial) collected in the north-western Black Sea waters. The highest concentrations of PCBs in the SPM were found at the Danube mouth (57·4 pg l 1), the north continental shelf (3·7–36·9 pg l 1) and offshore Constantza (33 1 pg l 1), while the most contaminated area (70·7–102 pg l 1) was found to be in the DP of the Danube estuary. Organochlorine compounds (DDTs, HCHs, HCB and dieldrin) were found one or two orders of magnitude higher in the DP than in the corresponding particulate phase. The high concentrations of HCHs (2·3–368 pg l 1 in the DP) as well as the distribution pattern of DDT-related compounds seem to indicate recent chlorinated pesticide use in the riparian countries of the Black Sea despite the regulations. Vertical profiles of SPM showed a general depletion of PCBs and organochlorine compounds (OCs) with depth and two accumulation zones, at the biomass maximum and the redoxcline. A bottom enrichment of OCs was observed when resuspension was favoured.