Maas-Diepeveen JLLutter WJDikkenberg RP van denGuchte C van deCanton JH2012-12-122012-12-121989-05-31http://hdl.handle.net/10029/258853for information about this report: Roghair CJ.Contamination of aquatic sediments may cause toxic effects on organisms. Sediment toxicity tests, especially those with benthic organisms, have to be standardized. In this study (semi)-chronic research were performed using Daphnia magna and larvae of Chironomus riparius. The testorganisms were exposed to both sediments and extracted pore waters. In order to compare the reproducibility of the testmethods, work with D. magna was carried out in two different laboratories. Two aquatic sediments were sampled in the river Rhine and one reference sample was taken from a nature reservate. Based on classification according to the Dutch interim procedure to classify sediments the contaminated sediments belong to class 3 and the reference sediment to class 2. With D. magna effects in pore-water were stronger than effects in sediment-water systems. Results of the two laboratories were not identical, possibly due to differences in practical handling and in sensitivity of the daphnias. Effects on C. riparius were not clear. High contents of ammonium and salt may have caused serious side-effects. Such effects were also noticed in tests with the reference material. the use of this material has to be reconsidered. A test with a recirculating-water system requires much labour and gives no further information in (semi)-static tests.Abstract not available38 pnl07Report2012-12-12