Lindane degradation potential of methanotrophs and soil microbial biomass from HCH contaminated sites

Abstract

In the present study, soil physico-chemical properties, hexachlorocyclohexane (HCH) isomers, lindane degrading soil methanotrophs and soil microbial biomass-C, N and P were investigated by selecting 6 study sites in Lucknow and Renukoot region of Uttar Pradesh, Northern India. The ANOVA revealed significant variations soil physico-chemical properties (P<0.001), HCH residues concentrations (P<0.001) and lindane degradation by soil methanotrophs (P<0.001), across different study sites. The GC and GC-MS/MS analysis revealed soil contamination by α, β-, γ-, and δ-HCH, along with organochlorine pesticides (OCPs) including aldrin, β-endosulphan, and dichlorodiphenyltrichloroethane (DDT). The concentration of soil HCH isomers (0.43-310.97 μg g⁻¹) was higher in the soil samples of Lucknow region, compared to the Renukoot (0.12–194.44 μg g⁻¹) region. These results depict that methanotrophic isolates SBRJS01, SBIJS02 and SBJS03 compared to control, showed better growth at selected environmental parameters. During lindane degradation the maximum Cl⁻ release among the methanotrophic isolates showed the trend as SBJS03> SBRJS01> SBIJS02> ControlURRH3. A positive linear relationship (R²=0.7951) was noted between lindane degradation and Cl⁻ release during the methanotrophic isolates incubation period. A greater SMB–C, –N and –P values (365.2, 65.5, and 26.8 μg g⁻¹ soil, respectively), having higher HCH residues were, recorded in the soil samples of Renukoot region, compared to the soils of Lucknow region.The negative correlation between SMB–C, –N, and –P values and different soil HCH isomers suggests that higher concentrations of lethal HCH residues persisting in soils negatively impacts the quantity of soil microbial biomass. Therefore, on-site monitoring and methanotrophic mediated bioremediation of HCH soil residues might be a viable and eco-friendly option in removal of this particular persistent soil pesticide from the contaminated area.