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Toxicity assessment and prediction of a realistic pesticide mixture from a portuguese agricultural area using concentration-response surface statistics
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Orientador(es)
Resumo(s)
Previous work showed the co-occurrence of the organophosphate chlorpyrifos and the striazine
herbicide terbuthylazine in surface waters of agricultural areas in “Lezíria do Tejo”,
Portugal. In the present study, we examine the effects of these pesticides singly and as a
binary mixture on the immobility of Daphnia magna and on the growth rate of the microalgae
Pseudokirchneriella subcapitata. Terbuthylazine and chlorpyrifos at single exposure caused
a very toxic or toxic response in both organisms. Usually, the toxicity of mixtures is evaluated
in relation to the reference models Concentration Addition (CA) and Independent Action (IA).
Initially, in this study was used the CA and IA model was to evaluate the joint effects of
chlorpyrifos and terbuthylazine. For immobility endpoint, the data fits better to the IA model,
due to different mode of action of the pesticides, however a specific pattern was showed; at
low dose levels the immobility was lower than modelled (antagonism), whereas at high dose
levels the immobility was higher than modelled (synergism). On the other hand, no deviation
was observed from independent action in algal tests. This study represents an important step
to understand the interactions among pesticides detected previously in field monitoring
studies of agricultural areas in “Lezíria do Tejo”, Portugal. Observed mixture toxicity was
compared with predictions, calculated from the concentration response functions of
chlorpyrifos and terbuthylazine at two realistic concentration ratios by applying the
biologically relevant patterns in which deviations occurred. The assumption of these last
yielded accurate predictions, although worst for the mixture ratio chlorpyrifos 0.17 and
terbuthylazine 85 μg/L under consideration.
Descrição
Mestrado em Engenharia do Ambiente - Instituto Superior de Agronomia - UL
Palavras-chave
mixture chlorpyrifos terbuthylazine Daphia magna Pseudokirchneriella subcapitata toxicity
Contexto Educativo
Citação
Martins, C.A,H, - Toxicity assessment and prediction of a realistic pesticide mixture from a portuguese agricultural area using concentration-response surface statistics. Lisboa: ISA, 2016, 44 p.