ABSTRACT
In recent years atrazine has evoked considerable concern all over the world because of its appearance in ground and surface waters. The published literature abounds in studies relating to ecotoxicological effects of atrazine using single-species-tests, indoor microcosms, outdoor microcosms and mesocosms as well as indoor and outdoor experimental streams. In singlespecies-tests, with comparable exposure times (96 h), the concentration of atrazine producing measurable effects varies from 0.012 mg/L to more than 1.000 mg/L. Aquatic macrophytes and algae appear to be the most sensitive organisms, whereas fishes and invertebrates generally show a low sensitivity. Commonly, the experimental results from single-species-tests vary greatly. Many model studies have also been conducted for both standing and flowing waters. Whereas in two studies the effects of atrazine on photosynthesis or on growth of phytoplankton have been registered at concentrations as low as 0.001 mg/L, in many other studies a clear impact on phytoplankton could be recorded only at concentrations of 0.018 to 0.1 mg/L with an exposure period of 10 to 20 days. Even in long term studies, conducted over periods of 136 to 400 days, measurable effects did not appear until a concentration of 0.02 mg/L or more was applied. These results were supported by additional data on functional ecosystem parameters in different test systems. These ecotoxicological threshold concentrations for standing limnic systems must be adjusted upwards to 0.1 mg/L for flowing water systems. Since the observed concentrations of atrazine in surface waters range from 0.002 mg/L for standing to 0.087 mg/L for flowing waters (and this normally only for few a minutes), it is likely that at concentration levels of up to 0.02 mg/L, atrazine may not cause any serious and permanent damage to aquatic ecosystems.
