Estudos ecotoxicológicos com ênfase na avaliação da toxicidade de surfactantes aniônicos aos cladóceros Daphnia similis, Ceriodaphnia dubia e Ceriodaphnia silvestrii
Coelho, Katiuscia da Silva
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The main anionic surfactants world widely used are the sodium dodecyl benzene sulfonate (LAS) and sodium dodecyl sulfate (DSS), which are mainly used in the manufacturing of domestic and personal hygiene products. As a consequence of the great and increasing consumption of LAS and DSS there is an increasing wareness regarding the adverse effects of these compounds to the organisms and environment. The present study aimed to evaluate the acute and chronic toxicity of the compounds LAS and DSS to the cladocerans Daphnia similis, Ceriodaphnia dubia and Ceriodaphnia silvestrii. It was also evaluated the toxicity of the water and sediments of four reservoirs and one stream of São Paulo State Analyses of LAS concentrations in the water of these reservoirs were also performed by Liquid chromatography. Acute toxicity tests indicated a value of CE(I)50;48h for LAS of 14.17 mg L-1 to D. similis, 11.84 mg L-1 to C. dubia and 13.51 mg L-1 to C. silvestrii. Significant changes in the viability of the cladoceran offsprings were observed for C. dubia and C. silvestrii exposed to the LAS, with values of CENO equal to 1.0 mg L-1 to C. dubia and 2.5 mg L-1 to C. silvestrii. It was concluded that the maximum permissible concentration of 0.5 mg L-1 surfactants as established by the resolution CONAMA nº. 357/2005 (Brazilian Ministry of Environment) in order to protect aquatic communities is adequate, considering the sensitivity of the native species C. silvestrii. The results of the acute toxicity tests with DSS indicated a CE(I)50;48h value of 12.82; 4.37 and 5.42 mg L-1, for D. similis, C. dubia and C. silvestrii, respectively. A CENO value of 2.0 mg L-1 was obtained in the chronic toxicity tests for C. silvestrii. The surfactant LAS was detected in all the water samples collected in the Lobo (Broa), Lagoa Dourada and Fazzari reservoirs, but at concentrations lower than 5 mg L-1 (the method limit of detection). The toxicity tests with environmental samples revealed that there is no toxicity in the water of the Lobo and Lagoa Dourada sampled, however the water of Monjolinho Reservoir was toxic to D. similis and Fazzari stream was toxic to D. similis and C. dubia. Only the sediment of Monjolinho Reservoir was not toxic to cladocerans.