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(M/FF211) The impact of the sediment remobilization on the aquatic organisms. Cavaleiro, Lurdes1, Silva, Paula C.1, Antunes, Sara1, Pereira, Ruth1, Santos, Conceição1, Gonçalves, Fernando1, 1 ABSTRACT- In the agricultural lands large quantities of pesticides were utilised and large amount of irrigation implies a leaching of pesticides in the environment. Some studies report that pesticides are detected in surface waters and are extremely toxic to aquatic organisms. In addition, pesticides may leach from applied zones to sensitive areas. The process of preferential flow in soils and associated pesticide movements has been identified as having a great impact on surface water quality. As the major part of the pesticides appear to be bound in the sediment, experiments on laboratory scale were conducted in order to investigate if there was a release of pesticides from the sediment and to evaluate their impact on aquatic organisms. The sediment was spiked with 3 concentrations of Lindane and Lindafor®. For each concentration sediment was placed both in ASTM and in freshwater from the same lake. Toxicity tests using the standard species (Daphnia magna e Vibrio fischeri) and field species (Daphnia longispina) were performed with the elutriated obtained and contamined ASTM. The results showed that the sensitivity of aquatic organisms to the pesticides was significantly increased with increasing of dose. On the other hand, the sediment remobilisation was accompanied by increase of toxicity for D. magna and D. longispina. The results of this study indicate that continued attention should be devoted to irrigation methods, leaching of pesticides and quantities of applied chemicals in agricultural lands in order to provide the desired level of environmental protection. Key words: pesticides, lindane, sediment remobilization, Cladocera |
