English Abstract This report presents the first experiments carried out
in a study to develop standardized sediment toxicity tests. The acute
toxicities of chlorpyriphos to the waterflea Daphnia magna and the midge
larvae Chironomus riparius were determined in a sediment/water system, pore
water and two elutriates. The methods chosed fulfilled requirements of
toxicity testing regarding the choice of test species, duration,
possibilities for standardization and easiness to conduct. The toxicity of
chlorpyriphos appeared not to be dependent on the systems used. The nominal
96 hr-EC50 of chlorpyriphos to D.magna was 0.45 mg/kg dw in an elutriate
and 0.42 mg/kg dw in the other test systems. The nominal 96 hr LC50 for
C.riparius was 0.09 mg/kg dw in the sediment/water-system and 0.14-0.24
mg/kg dw in the other systems.
