Dissipation of pesticides and responses of bacterial, fungal and protistan communities in a multi-contaminated vineyard soil

Abstract The impact of pesticide residues on non-target microorganisms in multi-contaminated soils remains a subject of limited understanding. Here we investigated the dissipation of commonly used pesticides in a multi-contaminated vineyard soil and its influence on bacterial, fungal, and protistan communities. We conducted laboratory soil microcosm experiments under varying temperature (20°C and 30°C) and water content (20% and 40%) conditions. Pesticide dissipation half-lives ranged from 27 to over 300 days, contingent upon the physicochemical properties of the pesticides and the soil conditions. In both the autoclaved and non-autoclaved soil experiments, more than 50% of hydrophobic pesticides (dimethomorph > isoxaben > simazine = atrazine = carbendazim) dissipated within 200 days at 20°C and 30°C. However, the contribution of biodegradation to the overall dissipation of soluble pesticides (metalaxyl > isoproturon = pyrimethanil > S-metolachlor) increased to over 75% at 30°C and 40% water content. This suggests that soluble pesticides became more bioavailable and degradation activity increased with higher temperature and soil water content. In contrast, the primary process contributing to the dissipation of hydrophobic pesticides was aging. An analysis of high-throughput amplicon sequencing indicated that water content, temperature, and pesticides had domain-specific impacts on the diversity and taxonomic composition of bacterial, fungal, and protistan communities. Soil physicochemical properties exhibited a more significant effect than pesticides on the various microbial domains in the vineyard soil. However, pesticide exposure emerged as a secondary factor explaining the variations in microbial communities. Pesticides had a more substantial impact on protists compared to bacterial and fungal communities. Altogether, our results highlight the variability in the dissipation kinetics and processes of pesticides in a multi-contaminated vineyard soil, along with their effects on bacterial, fungal, and protistan communities.