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.
