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In the present investigation the influence of exposure duration and lipophilicity on the lethal body burdens (LBBs) of thirteen organophosphorus insecticides are investigated. The LBBs are found to differ widely between compounds, varying from 0.011 to 29 μmol·g−1 wet weight. Compounds of high hydrophobicity (log Kow > 4) tend to have high LBBs (2–29 μmol·g−1 wet weight) which are not dependent on exposure concentrations. Some, but not all, of the less hydrophobic compounds had lower LBBs which were dependent on the exposure concentration. The use of LBBs for the interpretation of aquatic toxicity data of specifically acting chemicals is discussed. The wide variation in the observed LBBs makes the solely use of LBBs for toxicity assessment far from straightforward for more specificically acting compounds.

The fate of the urea-herbicide linuron was studied in experimental ditches. Eight ditches were sprayed three times at monthly intervals, while two served as controls. As a simulation of spray drift, four doses (nominal: 0.5; 5; 15 and 50 pg.dni3) were applied in duplicate. After each herbicide application, the ditches were kept stagnant for a week, followed by a flow period of three weeks with fresh water. No clear stratifican n of linuron could be found in the water compartment. During the stagnant period, half-lives ‘a for the disappearance of linuron in the water compartment ranged from 7.2 to 11.8 days. The rate of disappearance was slower in the ditches treated with the highest dose and in colder treatment periods. A maximum of 6% of the linuron dose was found in the sediment and 1% in the macrophyte compartment. Approximately 20% of the fraction in the sediment compartment was present in the pore water. 01998 Else&r Science Ltd. All rights reserved