Pesticide dissipation capacity of an organic biomixture used in the agriculture exposed to copper oxychloride

Abstract

On-farm biopurification systems (OBS) or biobeds, comprise an environmentally friendly tool worldwide used during farm activities. This biological system is used to treat wastewater containing pesticides or pesticide spills in order to avoid groundwater contamination. During farm activities copper oxychloride (Ox) is normally co-applied with pesticides to treat fungal diseases. However, it is still uncertain if wastewater containing copper may be treated in OBS without cause deleterious effects on normal pesticide dissipation and biological activities. Therefore, our main objective was to evaluate the effect of Ox (at 10, 100 and 1000 mg kg-1) on the dissipation of a mixture of three active ingredients (atrazine, carbendazim and diazinon at 10 mg kg-1 each) in an OBS at laboratory scale. After simultaneous application of Ox and pesticides, OBS were incubated in dark at 25 °C, and for 30 days residual pesticide, enzyme activities and microbial communities were evaluated. The results demonstrated that a negative dose-dependent effect on pesticide dissipation and biological activities occurred with a simultaneous presence of Ox and pesticides. Significant differences were found in pesticide half-lives (t1/2). Enzyme activities were initially affected but recovered. Molecular analysis (DGGE and qPCR) revealed slight differences in microbial communities, and mostly in fungal communities. Overall data demonstrated that disposal of Ox residues in OBP could be appropriated at concentrations ≤ 100 mg kg-1, as they did not compromise the pesticide dissipation capacity of the matrix in the short time.