Performance and Mechanisms of Biochar-Assisted Vermicomposting in Accelerating Dehp Biodegradation in Farmland Soil

Abstract

Either biochar or earthworms can accelerate di-(2-ethylhexyl) phthalate (DEHP) degradation in soils, by physically immobilizing organic pollutants or encouraging indigenous and intestinal degraders. However, very limited information is known about the biochar-assisted vermicomposting on soil DEHP degradation and the underlying mechanisms. This study investigated DEHP degradation performance and bacterial community change in soils with either earthworm, biochar or their combination. Both biochar and earthworms significantly improved DEHP degradation, and biochar exhibited a stronger impact on soil bacterial communities than earthworms. Burkholderiaceae, Pseudomonadaceae and Flavobacteriaceae were potential DEHP degraders and enriched in biochar-assisted vermicompsoting. Particularly, Burkholderiaceae and Sphingomonadaceae were enriched in earthworm guts and charosphere, possibly explaining the mechanisms of accelerated DEHP degradation in biochar-assisted vermicomposting. The increase of soil pH, SOM and humus (humic acid, fulvic acid and humin) also helped in encouraging DEHP degradation. These findings imply that earthworms coupled with biochar could enhance DEHP removal by improving soil physicochemical variables and microbial composition in soils, earthworm guts and charosphere.

Keywords: DEHP, soil, biochar, earthworm, microbial communities