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Study of the toxicological effects of emerging contaminants on Daphnia similis associating polyethylene microplastics with the agrochemical imidacloprid.
Summary
Brazilian researchers tested the ecotoxicological effects of combining polyethylene microplastics with the insecticide imidacloprid on the freshwater crustacean Daphnia, finding combined exposures were more toxic than either pollutant alone. These results suggest that microplastics and pesticides together pose greater risks to aquatic organisms than studies of single pollutants indicate.
A crescente preocupação com poluentes emergentes e seus impactos sobre corpos hídricos tem impulsionado diversos estudos. As análises ecotoxicológicas são uma das alternativas que auxiliam na investigação dos potenciais tóxicos de xenobióticos quando inseridos em sistemas ambientais, através das respostas de organismos modelos. Microplásticos (MPs) e pesticidas, em especial o imidacloprido (IMI), são compostos que têm sido cada vez mais verificados, mesmo em concentrações na ordem de micro ou nanogramas, em corpos d\'água. Esses compostos apresentam uma capacidade química sinérgica com grande risco potencial para os ecossistemas. O objetivo deste estudo foi avaliar os efeitos toxicológicos do imidacloprido comercial (IMIc) e padrão (IMIp), associados ou não aos microplásticos de polietileno, em partículas virgens e fragmentadas, através de seus efeitos toxicológicos agudos, crônicos e de estresse oxidativo sobre o organismo modelo, o microcrustáceo Daphnia similis. A caracterização físico-química dos MPs foi realizada por Espectroscopia de Infravermelha por Transformada de Fourier (FTIR-ATR), Microscopia Eletrônica de Varredura (MEV) e quantificação e mensuração por câmara de Sedgewick e Malvern 2000. Os IMIs foram caracterizados por espectrofotometria UV-Vis e submetidos a teste e avaliação de cinética de adsorção junto aos MPs. A combinação e mistura dos compostos apresentaram mudanças significativas na resposta de estresse oxidativo, no desbalanço redox dos organismos, apresentando maiores variações de atividades enzimáticas para os MPs quando associados aos pesticidas em relação aos compostos analisados isoladamente, expressando maior potencial tóxico quando em combinações. Assim, o estudo ecotoxicológico das amostras de IMI comercial e padrão mostraram-se fundamental no processo de avaliação dos MPs quando associados aos pesticidas, fornecendo informações sobre os potenciais impactos desses compostos no ecossistema aquático, além de verificar-se como mais uma ferramenta de contribuição no controle, regulamentação e remediação dos mesmos.
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