Pine Litter and Vermicompost as Alternative Substrates for Biobeds: Efficiency in Pesticide Degradation

Pesticide use generates wastewaters from its handling and from washing of spraying equipment, bringing concern about punctual discharge. Biobeds are biopurification systems for pesticide residues disposal, representing safe alternatives to avoid soil contamination. Peat that composes the original biomixture is not available all around Brazil. The aim of this work was to evaluate the efficiency of two alternative, accessible biomixtures, replacing peat, for treating phosmet (organophosphate insecticide) residues in biobeds and reducing its ecotoxicological effects. We hypothesized that the new biomixtures with pine litter (PB) or vermicompost (VB) could show the same degradation and detoxification efficiency as the standard biobed’s biomixture (SB) using peat. Small size bioreactors received 35 mg kg−1 of phosmet (Imidan®) in a laboratory-scale experiment. The pesticide degradation was monitored by chemical analysis. The decrease of ecotoxicity was determined by reproduction tests with collembolans (Folsomia candida) and enchytraeids (Enchytraeus crypticus), following ISO guidelines. Degradation curves showed that all biomixtures reached almost complete degradation of phosmet after 90 days. Collembolans were more sensitive than enchytraeid, confirming their usefulness in biomonitoring insecticide degradation. This work showed that both pine litter and vermicompost are potentially substitutes for peat in alternative biomixtures, since they were efficient in degrading the pesticide and reducing its ecotoxicity. Our results contribute for the development of newly, accessible biobeds for south Brazil, bringing the first study reports involving such biobeds capacity to degrade phosmet, which is a commonly used pesticide in this region.