RESUMO
A biopurification system based on the adsorption and degradation capacity of a biomixture to degrade a mixture of pesticides (atrazine, chlorpyrifos, iprodione; 50 mg kg-1 each) in repeated applications (0, 30, and 60 days) was evaluated. Tanks of 1 m3 packed with a biomixture (ρ 0.29 g mL-1) with and without vegetal cover were used. The biomixture contained soil, peat, and wheat straw in a proportion 1:1:2 by volume, respectively. Pesticide concentrations, biological activities (urease, phenoloxidase, and dehydrogenase), and microbial community changes (DGGE and qPCR) were evaluated periodically. Pesticide dissipation was higher in tanks with vegetal cover (> 95%) and no variation was observed after the three applications; contrarily, pesticide dissipation decreased in the tank without vegetal cover after each application. The presence of vegetal cover decreased the half-life of pesticides by at least twice. Biological activities were in general not affected by the application and reapplication of pesticides in the same treatment; however, they exhibited some differences between tanks containing and lacking the vegetal cover. High similarity between microbial groups (actinobacteria, bacteria, and fungi) was observed, suggesting no influence ascribable to the successive pesticide applications. The number of copies of bacteria and actinobacteria remained almost constant during the assay. However, the number of copies of fungi was significantly higher in the uncontaminated tank without vegetal cover.
Assuntos
Aminoimidazol Carboxamida/análogos & derivados , Atrazina/metabolismo , Clorpirifos/metabolismo , Poluição Ambiental/prevenção & controle , Hidantoínas/metabolismo , Microbiologia do Solo , Actinobacteria/metabolismo , Aminoimidazol Carboxamida/análise , Aminoimidazol Carboxamida/metabolismo , Atrazina/análise , Bactérias/metabolismo , Biodegradação Ambiental , Clorpirifos/análise , Enzimas/análise , Fungos/metabolismo , Hidantoínas/análise , Praguicidas/análise , Praguicidas/metabolismo , Plantas , Solo , Poluentes do Solo/análise , Poluentes do Solo/metabolismoRESUMO
The use of biopurification systems can mitigate the effects of pesticide contamination on farms. The primary aim of this study was to evaluate the effect of pesticide dissipation on microbial communities in a pilot biopurification system. The pesticide dissipation of atrazine, chlorpyrifos and iprodione (35 mg kg-1 active ingredient [a.i.]) and biological activity were determined for 40 days. The microbial communities (bacteria, actinomycetes and fungi) were analyzed using denaturing gradient gel electrophoresis (DGGE). In general, pesticide dissipation was the highest by day 5 and reached 95%. The pesticides did not affect biological activity during the experiment. The structure of the actinomycete and bacterial communities in the rhizosphere was more stable during the evaluation than that in the communities in the control without pesticides. The rhizosphere fungal communities, detected using DGGE, showed small and transitory shifts with time. To conclude, rhizosphere microbial communities were not affected during pesticide dissipation in a pilot biopurification system.