Behaviour of particulate polychlorinated biphenyls and polycyclic aromatic hydrocarbons in the Scheldt estuary
van Zoest, R.; van Eck, G.Th.M. (1990). Behaviour of particulate polychlorinated biphenyls and polycyclic aromatic hydrocarbons in the Scheldt estuary. Neth. J. Sea Res. 26(1): 89-96. http://dx.doi.org/10.1016/0077-7579(90)90059-P
Temporal and spatial variations in Polychlorinated Biphenyl (PCB) and Polycyclic Aromatic Hydrocarbon (PAH) contents were studied in the Scheldt estuary during a one-year period (August 1987-June 1988). Concentration levels in the Scheldt river (up to 206 ng·g-1 for individual PCB congeners and 14.6 µg·g-1 for individual PAH compounds) were higher than in any other river in the North Sea area. The annual input into the estuary was approximately 160 kg for total PCBs (10 congeners) and 12000 kg for total PAHs (13 compounds). A small fraction of the riverine PCB and PAH load (10%) was transported to the North Sea, whereas most organic pollutants were stored in estuarine sediments. Particulate PCBs and most particulate PAHs behaved conservatively in the Scheldt estuary. PCB and PAH contents decreased when salinities increased, as a result of the mixing of riverine with marine particulates. Moreover, the PCB patterns gradually shifted in that the fraction of less chlorinated biphenyls increased compared to more chlorinated congeners. Possible mechanisms are discussed. It is suggested that emissions of PCB mixtures enriched in less chlorinated congeners took place in the proximity of the mouth of the estuary. Low molecular weight PAHs (phenanthrene, anthracene and fluoranthene) were removed in the lower salinity range. This observation may be explained by microbial degradation at low salinities under (near) anoxic conditions, favoured by the long residence time of the particulates in the high-turbidity zone.
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