Impacts of polyethylene microplastics on the performance and mechanism of di-2-ethylhexyl phthalate (DEHP) degradation by two ecotype earthworms
Changhong Yang, Zhen Zhen, Weilong Wu, Guiqiong Yang, Jin Li, Yan‐Qiu Liang, Mengke Song, Dayi Zhang, Lin Zhong, Jing Bai
Abstract
Di-(2-ethylhexyl) phthalate (DEHP), a ubiquitous agricultural plasticizer, readily leaches into soils. Earthworm-mediated DEHP biodegradation and microplastics (MPs) co-contamination effects on vermicomposting remain uncharacterized. This study evaluated DEHP biodegradation and metabolic pathways in polyethylene microplastic-added soil under earthworm activity. Both epigeic and endogeic ecotypes of earthworms significantly accelerated DEHP degradation. In the treatment without microplastics, the highest degradation efficiency was 72.29 % by endogeic Pheretima guillelmi , while in the treatment with added microplastics, the degradation rate was up to 51.09 %. It was attributing to the increasing soil pH and humus (FA, HA, HM), and the elevated abundance of potential DEHP-degradation microorganisms ( Sphingomonas , Lysobacter , and Flavobacterium ) and genes ( fadA , paaH , and ACAT ). Particularly, vermicomposting improved anaerobic benzoyl-CoA degradation pathway, in which Sphingomonas , Lysobacter , and Flavobacterium might carry fadA , paaH , and ACAT genes. Polyethylene-MPs significantly delayed DEHP degradation to 18.48 % in soils without earthworms and 51.09 % in vermicomposting treatments by reducing the abundance of DEHP-degrading microorganisms and genes. Findings revealed polyethylene-MPs effects on earthworm-mediated DEHP degradation and guided agricultural soil management strategies. • Both epigeic and endogeic ecotypes of earthworms significantly accelerated DEHP degradation. • Vermicomposting raised soil pH and humus, and the elevated abundance of potential DEHP-degradation microorganisms and genes. • Vermicomposting improved anaerobic benzoyl-CoA degradation pathway of DEHP. • Polyethylene-MPs significantly delayed DEHP degradation by reducing the abundance of DEHP-degrading microorganisms and genes.