BEHAVIOR OF PCB, PENTACHLOROBENZENE, HEXACHLOROBENZENE, ALPHA-HCH, GAMMA-HCH, BETA-HCH, DIELDRIN, ENDRIN AND P,P'-DDD IN THE RHINEMEUSE ESTUARY AND THE ADJACENT COASTAL AREA

Organochlorines (pentachlorobenzene, hexachlorobenzene, PCB, α-HCH, γ-HCH, β-HCH, dieldrin, endrin, p,p′-DDD) have been quantitated in water, seston, bottom sediment and interstitial water in samples from the fresh water and estuarine region of the Rhine-Meuse system obtained in 1974, 1976 and 1979. In the estuarine region, the amounts in solution are smaller than in suspension for pentachlorobenzen, hexachlorobenzene and PCB, dissolved concentrations dominating for the hexachlorocyclohexane isomers. In river water, PCB is roughly equally distributed over dissolved and suspended forms while pentachlorobenzene, hexachlorobenzene and the HCHs dominate in solution. Dissolved dieldrin, endrin and p,p′-DDD were below the limits of detection in most river water samples. However dissolved dieldrin and endrin are produced in the upper part of the estuary resulting from local pollution. During estuarine mixing, dissolved concentrations of all compounds were found to be linearly related to salinity (1974 data). Concentration data in seston and sediment in the estuarine region can be explained in terms of mixing of fluviatile and marine derived particles. It is suggested that in particular PCBs are associated specifically with finer particles. Dissolved concentrations in the central part of the Southern Bight are at the very lower end of the range of values reported for various coastal and open ocean areas. Concentrations detected in large volume samples are: penta- and hexachlorobenzene 0.1 ng·1-1; PCB (Aroclor 1254) 0.7 ng·1-1; α-HCH 0.9 ng·1-1; γ-HCH 1.0 ng·1-1; β-HCH 0.04 ng·1-1; dieldrin 0.1 ng·1-1 and endrin and p,p′-DDD < 0.01 ng·1-1. Temperature programmed GLC techniques demonstrate the contribution of lower chlorinated PCB components in the central part of the Bight. This has not been observed in other reports. Adoption of a PCB formulation with a lower degree of chlorination than the usual Aroclor 1254 as the standard for quantitation results in a significant shift of the PCB concentrations from 0.7 (Aroclor 1254 or the equivalent Clophen A50) to 4.1 ng·1-1 (Clophen A30). It is suggested that the lower chlorinated fraction is derived from atmospheric input. River water could not be excluded as a source however. Concentrations in the coastal area are higher than in the central part of the Southern Bight. Analyses of large volume water samples in 1979 are consistent with continuing conservative behaviour in the coastal area. A large fraction of the organochlorine load of the Dutch Wadden Sea is derived from the Rhine-Meuse estuary. © 1979.