Dissipation of chlorpyrifos, pendimethalin, and thiophanate-methyl pesticides in compost based-versus peat-moss based-biomixture of biobeds

Biobed is a smart bioremediation system used to treat point-source pesticide contamination.Biomixture is the main component of biobeds,and pesticide dissipation is affected by its composition.This study aimed to compare the effectiveness of compost-based(C)versus peat-moss-based(P)biomixtures of biobeds on tested pesticide dissipation.Three concentrations(25,50,and 75 mg/kg)of chlorpyrifos,pendimethalin,and thiophanate methyl were added separately and as a mix to both biomixtures C and P.Our data showed the effect of biomixture type on the dissipation of the tested pesticides.For chlorpyrifos,its dissipation rate in biomixture P was more rapid than that in biomixture C.This result was confirmed by the mineralization kinetic experiment,since 25%of the initial ^(14)C-chlorpyrifos concentration accumulated in the form ^(14)CO_(2) in biomixture P compared to only 14%in biomixture C.In addition,the chlorpyrifos dissipation rate was influenced by the initial concentration when applied individually in biomixture P.In contrast,biomixture C was more effective at pendimethalin dissipation than biomixture P,since>76%of pendimethalin was dissipated in biomixture C versus 67%in biomixture P at the same incubation time.For thiophanate-methyl,the abilities of both biomixtures C and P were similar and less efficient than those of the other tested pesticides.The addition of the three tested pesticides to biomixture C only had a positive effect on both chlorpyrifos and thiophanate-methyl dissipation,while pendimethalin dissipation was similar when applied separately or as a mix.Microbial activity was stimulated by the addition of separately or mixed pesticides to biomixtures C and P as measured by dehydrogenase activity.

Removal of carbofuran is not affected by co-application of chlorpyrifos in a coconut fiber/compost based biomixture after aging or pre-exposure

Biomixtures constitute the biologically active part of biopurification systems（BPS）, which are used to treat pesticide-containing wastewater. The aim of this work was to determine whether co-application of chlorpyrifos（CLP） affects the removal of carbofuran（CFN）（both insecticide/nematicides） in a coconut fiber–compost–soil biomixture（FCS biomixture）, after aging or previous exposure to CFN. Removal of CFN and two of its transformation products（3-hydroxycarbofuran and 3-ketocarbofuran） was enhanced in pre-exposed biomixtures in comparison to aged biomixtures. The co-application of CLP did not affect CFN removal, which suggests that CLP does not inhibit microbial populations in charge of CFN transformation.Contrary to the removal behavior, mineralization of radiolabeled14C-pesticides showed higher mineralization rates of CFN in aged biomixtures（with respect to freshly prepared or pre-exposed biomixtures）. In the case of CLP, mineralization was favored in freshly prepared biomixtures, which could be ascribed to high sorption during aging and microbial inhibition by CFN in pre-exposure. Regardless of removal and mineralization results, toxicological assays revealed a steep decrease in the acute toxicity of the matrix on the microcrustacean Daphnia magna（over 97%） after 8 days of treatment of individual pesticides or the mixture CFN/CLP.Results suggest that FCS biomixtures are suitable to be used in BPS for the treatment of wastewater in fields where both pesticides are employed.