Microbial impact of the pesticide chlorpyrifos on Swedish and Italian biobeds

Abstract

-Biobeds provide a simple and cheap solution to reducing point-source contamination by pesticides from farm activities. In its original design, the Swedish biobed is a clay-lined pit in the ground filled with a biomixture of topsoil, peat and straw and covered with a grass layer. The straw stimulates the growth of lignin-degrading fungi and the formation and activity of ligninolytic enzymes which can degrade many different pesticides. Here we compared the behaviour of the chlorpyrifos pesticide in two biobeds of different composition: a Swedish biobed composed of 50%v vine straw, 25%v peat and 25%v Swedish soil; and an Italian biobed composed of 40%v vine straw, 40%v green compost and 20%v Italian soil. Microbial biomass was measured in the Italian biomix by the fumigation-extraction method. The microbial activity was estimated by measuring mineralisation of a synthetic lignin, 14 C-de-hydrogenative polymerisate ( 14 C-DHP) in the Swedish biomix. Microbial respiration was followed over time in both biomixes. Our results show that the chlorpyrifos half-lives were similar in both biomixes. The microbial biomass content was reduced by 25 and 50% with, respectively, 10 and 50 mg kg −1 chlorpyrifos in the Italian biomix. The respiration activity was affected only at 50 mg kg −1 chlorpyrifos in the Italian biomix. No effect was observed in the Swedish biomix despite the higher chlorpyrifos concentration of 100 mg kg −1 . The mineralisation of 14 C-DHP was not affected by the presence of chlorpyrifos in the Swedish biomix. These findings could be explained by the presence of chlorpyrifos-sensitive microorganisms in the Italian biomix and chlorpyrifosresitant microorganisms in the Swedish biomix. The more robust microflora developed in the Swedish biomix may be explained by its lower nitrogen content, higher C/N ratio and lower pH, all of which are favourable for the development of lignin-degrading fungi and their activity. In Sweden more than 1000 biobeds are in practical use on farms and they have been shown to be efficient at reducing pesticide water-body contamination. The present study compares the capability of an Italian biomix for degrading pesticides to that shown by the Swedish original biomix in order to introduce this biological system for a sustainable Italian agriculture. chlorpyrifos / organic biomixes / pesticide biodegradation / ligninolytic microflora

Chlorpyrifos: pollution and remediation

“…Though the null effect of chlorpyrifos on soil microbial biomass had been reported (Adesodun et al 2005), impacts of chlorpyrifos on soil microbial characteristics including microbial biomass, microbial populations, microbial respiration, enzymatic activities, and mineral cycling have been frequently studied. Findings indicated statistically (2000) Environ Chem Lett significant reduction in soil microbial biomass (Vischetti et al 2007), and soil enzyme activities (Singh et al 2003a) resulted from repeated application of chlorpyrifos and accumulation of 3,5,6-trichloro-2-pyridinol. There are contradictory evidences on changes in microbial population due to chlorpyrifos application.…”

Prediction of Bioavailability of Chlorpyrifos Residues in Soil to Earthworms

“…It is effective against a broad spectrum of agricultural and household pests. The behaviors of chlorpyrifos in soil were studied intensely due to its long persistence in soil environments and harmful impacts upon organisms (e.g., Racke et al, 1998;Yucel et al, 1999;Singh et al, 2003;Ngan et al, 2005;Fang et al, 2006;Vischetti et al, 2007;Fang et al, 2008;Vejares et al, 2010). Earthworms comprise the largest proportion of the biomass of the soil fauna and contribute to the process of cycling of nutrients in terrestrial ecosystems.…”

Degradation and adsorption of terbuthylazine and chlorpyrifos in biobed biomixtures from composted cotton crop residues

“…Compared with northern Europe, little is known about the implementation of biobeds in southern Europe, where agricultural practices and climatic conditions differ greatly. Over the past 5 years, a series of studies in Italy has shown that a biomixture consisting of various composted materials instead of peat, and macerated vine branches instead of straw, has high degradation capacity,11–13 and it has been utilised in a prototype biobed system constructed in northern Italy 14. However, no other studies are available regarding biobeds in the Mediterranean region.…”