Assessment of Organic Compounds in the Rhine Estuary

Abstract

Over the past centuries the Rhine estuary has changed from a natural, hardly disturbed estuary into an anthropogenetically influenced area that extends into the North Sea. The impact of the River Rhine on the adjacent coastal zone of the North Sea has thus increased dramatically, with relatively high loads of suspended matter and associ- ated as well as dissolved compounds reaching as far as theWadden Sea and further north. This chapter briefly discusses the historical changes in morphology and hydrology and reviews the concentrations of organic substances in the lower River Rhine and their pos- sible effects on the estuarine and adjacent coastal zones. Gradually the loadings of these zones fromriverine inputs have shifted fromthe more persistent chemicals such as HCHs and drins to PCBs and PAHs, and today to the more polar persistent compounds includ- ing surfactants and pharmaceuticals.Most of the concentrations of the persistent organic compounds have decreased, although a few, including the brominated flame retardants, show an increasing trend. Because of the large area involved and the technical problems of effect assessments in marine areas, a proper effect assessment can hardly be made for the area. Although effects related to specific exposure (e.g. organotins) have been observed occasionally, in general neither in vivo nor in vitro responses have been ob- served in the Dutch coastal zone of the North Sea, not even at dumping sites for harbour dredge. Regulatory bodies disagree remarkably about the compounds that should be pri- oritised, or the bioassay batteries that should be involved in evaluating actual exposure. Harmonisation of procedures is urgently needed in this respect.