Remediation of chlorpyrifos and deltamethrin in different salinity soils and its impact on soil bacterial composition

Pesticides are chemicals widely used in agricultural industry, but their ecotoxicological effects on the environment are not still well understood. In this study, remediation of chlorpyrifos (CP) and deltamethrin (DM) and their impacts on soil microbial diversity were investigated. Four different soils with various salinities (0%, 1%, 2% and 4%) were artificially contaminated by CP and DM. Then, bioremediation of the pesticides in soil microcosms was monitored and their effects on soil microbial composition were studied by metagenomics. The pesticide degradation analysis showed higher CP remediation in slightly saline soils with 1% and 2% salinity and higher removal of DM in 1% saline soil in comparison to non-saline control microcosm. The complete remediation of contaminants took around 60 days. The metagenomic analysis indicated that pesticide contamination had significant impacts on soil flora and some dominant species in control microcosm were completely eliminated in CP and DM amended microcosms. Paenibacillus (2% salinity and DM), Bacillus (4% salinity and CP), Paeniclostridium (1% salinity and DM) and Lachnospiraceae (1% salinity and CP) were the dominant genera by 77%, 50%, 41% and 39% relative abundances, respectively. At phylum level, sequences belonging to Firmicutes , Proteobacteria , Bacteroidetes and Actinobacteria were considerably enriched during remediation of both pesticides. Shannon and Simpson Indexes were identified to be more sensitive to microbial community evenness, while, Chao1 and ACE indexes were changed by community abundance. It was revealed that the highest negative impacts of deltamethrin and chlorpyrifos on the culturable and unculturable communities were related to the non-saline soil. Graphical abstract