Herbicide bioconcentration in algae: studies on lipophilicity-sorption-activity relationships (LSAR) with Chlorella fusca

Lipophilicity-sorption-activity relationships (LSAR) were studied for a congeneric series of 15 herbicidal phenylureas with the unicellular green alga Chlorella fusca as a model organism. Data for substance lipophilicity (log kw), algal bioconcentration (log BCF) and algal toxicity (pI50 CV/CN) were experimentally determined and subsequently subjected to a series of regression analyses. These studies revealed only moderate correlations between log kw and log BCF and between log kw and pI50 values. In contrast, a highly significant relationship was observed between bioconcentration and toxicity. The following conclusions were drawn on basis of the results. (i) The predictive value of lipophilicity for estimating herbicide bioconcentration and toxicity in microalgae is limited. (ii) Different levels of phenylurea toxicity for Chlorella seem to be attributable to different degrees of bioconcentration. (iii) An integrated consideration of lipophilicity, bioconcentration and toxicity should be advantageous in aquatic ecotoxicological hazard assessment.