Individual and Joint Toxicity of Three Chloroacetanilide Herbicides to Freshwater Cladoceran Daphnia carinata.
ABSTRACT Individual and joint toxicity of three chloroacetanilide herbicides to a freshwater cladoceran were studied. The 48 h-LC(50) values of alachlor, acetochlor and butachlor to Daphnia carinata Dc42 were 11.1, 11.8 and 3.45 mg L(-1), respectively. The toxicity was significantly (p < 0.05) related to hydrophobicity. The additive indexes of binary mixtures of three herbicides were less than zero and it showed antagonism. The body length of D. carinata treated with high concentration of herbicides was shorter than that of control group significantly (p < 0.05). It suggests that joint actions must be considered when assessing the acute toxicity of chloroacetanilide herbicides to D. carinata.
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ABSTRACT: Various pesticides have become widespread contaminants of soils due to their large applications in agriculture and homes. An earthworm assay was used to assess the acute toxicity of butachlor, imidacloprid and chlorpyrifos with different modes of action. Ecotoxicities of these pesticides were compared for earthworm Eisenia fetida separately and in combination in artificial soil and contact filter paper tests. Imidacloprid was the most toxic for E. fetida with LC50 (lethal concentration 50) values three orders magnitude lower than that of butachlor and chlorpyrifos in both tests. The toxicity of the mixtures was compared to that predicted by the concentration addition (CA) model. According to the CA model, the observed toxicities of all binary mixtures were less than additive. However, for all the mixtures in 14d artificial soil test, and mixtures of butachlor plus chlorpyrifos and imidacloprid plus chlorpyrifos in 48h contact filter paper test, the difference in toxicity was less than 30%, hence it was concluded that the mixtures conformed to CA. The combined effects of the pesticides in contact filter paper tests were not consistent with the results in artificial soil toxicity tests, which may be associated with the interaction of soil salts with the pesticides. The CA model provides estimates of mixture toxicity that did not markedly underestimate the measured toxicity, and therefore the CA model is the most suitable to use in ecological risk assessments of the pesticides.Chemosphere 12/2013; · 3.14 Impact Factor