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2F - Site Specific Testing (MOP/104) Impact of pesticides on the quality of water issued from rice fields (Camargue, France). Devez, Aurelie1, Fenet, Helene1, Gomez, Elena1, Casellas, Claude1, 1 Faculty Pharmacy, Montpellier, France, France ABSTRACT- An ecotoxicological study of water discharged from rice fields treated with pesticides was performed from May to August 2002 in Camargue (France) by using a combination of bioassays and chemical analyses. This work aimed to study the impact of pesticides treatment on the quality of water resulting from rice plantations. It was important to elucidate their effects on algal communities as some of them, such as herbicides, were not selective. Water samples were collected once a week from two rice plots, one cultivated using classical pesticides (P) and one using traditional treatment (T). Each two weeks, water was sampled from river Rhone (water used for irrigation), and from three drainage channels. The toxicity of the particulate fractions, after extraction, and the dissolved fraction, directly and after extraction, was evaluated by an algal growth inhibition test (Pseudokirchneriella subcapitata). Pesticides residue concentration was determined by HPLC/UV (Azimsulfuron-Herbicide) and GC/MS (Pretilachlor, Oxadiazon -Herbicides- and Fipronil, Alphacypermethrin -Insecticides-). Moreover, the toxic effect of each pesticide on algal growth was investigated and the reference EC50-72h was evaluated. No toxicity was noted on the T plot, and toxicity of the P plot was detected during the period when herbicides were applied (May to June). No toxicity of the river waters was noted while, toxicity was observed in the drainage channels from end of June until beginning of July. The study of the substances toxicity showed synergic and/or antagonist effects of organic pesticides. This leads to a difficulty in establishing relationships between pesticides concentrations and toxicological effects. Moreover, in the final interpretation, we must consider that metabolites or other undetected compounds could contribute to the global toxicity. Key words: algal toxicity, pesticides, paddy field, Camargue |
