Pesticide degradation in a ‘biobed’ composting substrate

Abstract

Pesticides play an important role in the success of modern farming and food production. However, the release of pesticides to the environment arising from non-approved use, poor practice, illegal operations or misuse is increasingly recognised as contributing to water contamination. Biobeds appear to offer a cost-effective method for treating pesticide-contaminated waste. This study was performed to determine whether biobeds can degrade relatively complex pesticide mixtures when applied repeatedly. A pesticide mixture containing isoproturon, pendimethalin, chlorpyrifos, chlorothalonil, epoxiconazole and dimethoate was incubated in biomix and topsoil at concentrations to simulate pesticide disposal. Although the data suggest that interactions between pesticides are possible, the effects were of less significance in biomix than in topsoil. The same mixture was applied on three occasions at 30-day intervals. Degradation was significantly quicker in biomix than in topsoil. The rate of degradation, however, decreased with each additional treatment, possibly due to the toxicity of the pesticide mixture to the microbial community. Incubations with chlorothalonil and pendimethalin carried out in sterile and non-sterile biomix indicated that degradation, rather than irreversible adsorption to the matrix, was the main mechanism responsible for the reduction in recovered residues. Results from these experiments suggest that biobeds offer a viable means of treating pesticide waste.

Influence of novel lignocellulosic residues in a biobed biopurification system on the degradation of pesticides applied in repeatedly high doses

“…Repeated use of some pesticides in soils can result in enhanced pesticide degradation due to the adaptation and proliferation of specific microbial communities (Torstensson et al 1975). However, our studies showed that the rate of pesticide degradation in the biomixtures decreased with each application of the pesticides, similar to the results found by Fogg et al (2003) for isoproturon, chlorothalonil, chlorpyriphos, dimethoate and pendimethalin. Our decreasing degradation rates may be due to the high pesticide concentrations used, so the negative effects of these high concentrations masked any increase in individual microbial activity.…”

Enhanced Dissipation of Selected Herbicides in a Simulated Organic Matrix Biobed: A System to Control On‐Farm Point‐Source Pollution

“…Similar to atrazine, pendimethalin had a half‐life of 25.5 d in soil (Table 2), and its half‐life was shorter by 53.3, 41.9, 46.7, and 49.0% in Biomix 1, Biomix 2, Biomix 3, and Biomix 4, respectively. Fogg et al (2003) incubated a mixture of pesticides, including pendimethalin, in biomix and topsoil, finding significantly faster dissipation in biomix than in topsoil. They also concluded that degradation, rather than adsorption, was the main mechanism for biomix to reduce the pendimethalin and chlorothalonil concentrations.…”

Effect of Pesticide Inoculation, Duration of Composting, and Degradation Time on the Content of Compost Fatty Acids, Quantified Using Two Methods

“…A recent pesticide database (Footprint, 2007; http://www.eu -footprint.org/ppdb.html, accessed April 2010) reports half-life values (days) in soil, derived from laboratory studies at 20°C, of 73.5 for azoxystrobin, 59 for chlorotoluron, and 226 for epoxyconazole. However, a certain variability exists, and in other research half-lives are longer, i.e., more than 2 years (at 10°C) for epoxyconazole (4), 62 to 107 days for azoxystrobin (10), and 30 to 200 days for chlorotoluron (36), showing that significant degradation should be measured on a time scale of months or years (8,9) according to the results of a recent review on pesticide persistence (3).…”