Although tons of disperse dyes are used worldwile, little information on their ecotoxicity is available. While in silico models can be used to predict their ecotoxicity, experimental results from Daphnia can show significantly higher toxicity than predicted. Thus the objective of this work was to extend the knowledge base in this area by evaluating the ecotoxicity of three widely used disperse dyes and comparing the results to predicted values. Bearing in mind that generating ecotoxicity data on azo disperse dyes is complicated because they are not readily found as homogeneous compounds, we employed chromatographic methods to purify three commercially dyes C.I. Disperse Violet 93, Blue 291, and Blue 373 already found in the aquatic environment. No acute toxicity was observed for Daphnia similis. These results seems to be in general agreement when compared with ECOSAR predicted values. We hypothesize that differences in Kow values could explain the variations in results.
The present work assessed the ecotoxicity of the commercially available form of the azo dye Disperse Red 1 (DR1) and the main degradation products generated during photo-Fenton degradation. The acute toxicity tests with the microcrustacean Daphnia similis showed that toxicity increased after 10 min of treatment, when 35% of the original concentration of the dye has been degraded but without decrease in total organic carbon concentration (TOC). The increase of toxicity was a consequence of generation of degradation products of higher toxicity than DR1, which achieved maximum concentration after 10 min reaction. The structures identified using LC/MS indicated that most of the intermediates were formed after addition of hydroxyl radical to benzenic ring but the cleavage of azo bond was also observed. The intermediates were further degraded and toxicity was then reduced to non toxic levels after 45 min experiment, when 98% of the initial concentration of DR1 was degraded and mineralization achieved 55%. The results of this study showed that the textile dye DR1 can be degraded by photo-Fenton process with removal of acute toxicity to D. similis even with incomplete mineralization.
RESUMOObjetivou-se, com este trabalho, avaliar a influência espacial e temporal da fitotoxicidade e da citogenotoxicidade da água e do sedimento de córrego urbano quanto às características germinativas e de crescimento inicial de Lactuca sativa. Amostras de água e de sedimento foram coletadas em 5 pontos do Córrego do Pântano (Alfenas, Minas Gerais), no período de outubro de 2010 a julho de 2011 e as concentrações dos metais Cd, Pb e Zn foram quantificadas. Os ensaios de fitotoxicidade e de citogenotoxicidade foram realizados com as amostras de água e extratos aquosos dos sedimentos. Os parâmetros avaliados foram taxa de germinação, comprimento de raízes, biomassa fresca e seca, índice mitótico e a frequência de anormalidades cromossômicas. Constataram-se maiores concentrações de Cd e Pb nas amostras de água coletadas nos meses com a ocorrência de precipitações pluviométricas. Água e sedimento apresentaram efeito fitotóxico sobre germinação, biomassa fresca e seca de Lactuca sativa. O comprimento de raízes foi estimulado e apenas as amostras de água reduziram o índice mitótico. Evidenciou-se, também, variação temporal significativa relacionada com o regime pluviométrico apenas para o teste de fitotoxicidade. Palavras-chave: alface, toxicidade, sazonalidadePhytotoxicity and cytogenotoxicity of water and sediment of urban stream in bioassay with Lactuca sativa ABSTRACT The aim of this study was to evaluate the spatial and temporal influence of the phytotoxicity and cytogenotoxicity of water and sediment of urban stream on the germination and initial growth of Lactuca sativa. Samples were collected from water and sediment at five sites of the Pântano Stream (Alfenas, Minas Gerais) during the period from October 2010 to July 2011. The concentrations of the metals Cd, Pb and Zn were quantified. Moreover, phytotoxicity and cytogenotoxicity were tested with samples of water and aqueous extracts of sediments. The evaluated end points were the germination rate, root length, fresh and dry weight, mitotic index and frequency of chromosomal abnormalities. Higher levels of Cd and Pb were verified in water samples collected during the rainy months. Water and sediment showed phytotoxic effect on germination, fresh weight and dry weight of Lactuca sativa. Root length was stimulated and only samples of water reduced the mitotic index. Significant temporal variation related to rainfall was observed only for phytotoxicity tests.
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