Assessment of ametryn contamination in river water, river sediment, and mollusk bivalves in São Paulo state, Brazil.

São Paulo state, Brazil, is one of the main areas of sugar cane agriculture in the world. Herbicides, in particular, ametryn, are extensively used in this extensive area, which implies that this herbicide is present in the environment and can contaminate the surface water by running off. Thereby, residues of ametryn were analyzed in samples of river water an river sediment and in freshwater bivalves obtained from the rivers Sapucaí, Pardo and Mogi-Guaçu in São Paulo State, Brazil. Samples were taken in the winter of 2003 and 2004 in two locations in each river. The specimens of freshwater bivalves collected and analyzed were Corbicula fluminea, an exotic species, and Diplodon fontaineanus, a native species. Additionally, the evaluation of the ability of bioconcentration and depuration of ametryn by the freshwater bivalve Corbicula fluminea was also performed. Ametryn concentrations in the samples were measured by liquid chromatography coupled to mass spectrometry. Residues of ametryn in water (50 ng/L) and in freshwater bivalves (2-7 ng/g) were found in the Mogi-Guaçu River in 2004, and residues in river sediments were found in all rivers in 2003 and 2004 (0.5-2 ng/g). The observation of the aquatic environment through the analysis of these matrixes, water, sediment, and bivalves, revealed the importance of the river sediment in the accumulation of the herbicide ametryn, which can contaminate the biota.

Bioaccumulation of atrazine in freshwater bivalves Anodontites trapesialis (Lamarck, 1819) and Corbicula fluminea (Müller, 1774).

The bioaccumulation of atrazine in bivalves is expected due to its wide use in agriculture and its moderate water solubility (33 mg/l). To assess the capacity of bioaccumulation, we performed a laboratory study in which two bivalves species (Anodontites trapesialis and Corbicula fluminea) were exposed to atrazine (concentrations of 0.06 to 0.34 microg/ml) during 48 h. The results showed that both bivalve species were able to bioaccumulate atrazine in their tissues. In another experiment, groups of bivalves from the specie A. trapesialis were exposed to atrazine at the concentration of 1 mug/ml and different organs of these animals were analyzed. The visceral mass, foot and mantle plus siphon showed the highest values of atrazine bioaccumulation.