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

Abstract

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 ¹⁴C-chlorpyrifos concentration accumulated in the form ¹⁴CO₂ 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.