Lindane degradation in wet-dry cycling soil as affected by aging and microbial toxicity of biochar

This study determined the degradation of lindane in soil amended with biochar to evaluate the effects of biochar aging and microbial toxicity. Two biochars were prepared at 400 and 600 °C (BC400 and BC600) and subjected to acid washing to remove nutrition (WBC400 and WBC600). After 89 days of incubation under the alternate “wet–dry” conditions, scanning electron microscopy showed that acid washing rendered biochars especially susceptible to aging with structural collapse and fragmentation, with less surface covering. Aging impeded the release of toxic substances in BC400 and BC600 with reduced toxicity to degrading microorganisms. Lindane degradation was somewhat stimulated by biochar nutrition but mainly inhibited by adsorption. Acid washing facilitated the release of toxic substances and additionally reduced lindane degradation. The variations in fatty acid saturation degree (SFA/UFA) in soils confirmed the microbial toxicity of 5% WBC400 > 5% BC400 > 5% BC600 > 5% WBC600. High-throughput DNA sequencing showed that biochar delayed the formation of dominant degrading microbial communities in soil. Lindane degradation was completed by joint Sphingomonas, Flaviolibacter, Parasegetibacter, Azoarcus, Bacillus and Anaerolinaea. These findings are helpful for better understanding the effect of biochar in soil on long-term degradation of persistent organic pollutants. [Display omitted] •Lindane degradation was facilitated by alternate wet-dry cycling in soil.•Acid washing accelerated biochar aging and its effect on lindane degradation.•Aging and toxicity of biochar altered soil microbial community structure.•Lindane in biochar-soil was degraded by consortia of major microbial genera.