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Folkerts AJ

23 p in Dutch   1993

Toon Nederlands

English Abstract
Organic concentrates of the River Rhinewater were tested for toxicity with a 15 minute MICROTOX test on luminescent bacteria Photobacterium phosphoreum. A concentration method with XAD-resins was altered in such a way that water samples with suspended material could be concentrated with XAD without filtration. In total, 11 stations in the German and Dutch lower Rhine were sampled three times, with the interval of two months. (May, July and September 1990), whereas two stations located the most apart in the Netherlands (Lobith and Maassluis) were sampled every two weeks in 1990. In 1991 Maxau (Germany) and Lobith were sampled incidentically together whith station Eijsden (River Meuse). The river samples were concentrated by neutral adsorption on XAD-resins, followed by eluation with acetone. Toxicity is expressed as the pT-value, a relative value on log-scale, based on the first none toxic concentration of a dilution-serie of the organic concentrate. The scale has been chosen such to represent a maximal tolerable risk concentration at 0 and a neglegible risk concentration at 1. According to the results of the investigations in 1990, the quality of the River Rhine does not reach a tolerable level. An increase of toxicity was measured on the German part of the River Rhine, whereas there was no measurable effect of three of the most important side-Rivers (Main, Neckar and Moselle) on the toxicity of the River Rhine. An improvement in water quality was measured in the Dutch sedimentation areas. In 1991, no significant difference was observed between the toxicity of the Rivers Rhine and Meuse. Expressing the toxicity results as a pT-value makes it possible to judge the quality of freshwater with respect to target levels.


RIVM - Bilthoven - the Netherlands - www.rivm.nl

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RIVM - Bilthoven - Nederland - www.rivm.nl

( 1993-04-30 )