PET microplastics influenced microbial community and heavy metal speciation in heavy-metal contaminated soils

Abstract

Co-occurrence of microplastics and heavy metals is common in soils. The interactions between microplastics and heavy metals have received increasing attention in recent years, particularly for revealing the mechanisms underpinning their interactions. In the present study, Polyethylene Terephthalate (PET) microplastics are added in soil, which have led to variations in soil physicochemical properties, enzymatic activity, microbial community structure, and chemical speciation of chromium (Cr), cadmium (Cd), copper (Cu), and zinc (Zn) in heavy metal contaminated soils. Soil physicochemical properties (pH, SWC and SOC) and enzymatic activities (urease and dehydrogenase) alter as result of PET addition, which promoted the transformation of heavy metal chemical speciation from bioavailable fraction to oxidizable and residual fraction. The results suggested that PET microplastics in heavy metal contaminated soil may reduce the heavy metal bioavailability by altering the properties of the soil microenvironment. The significant variations in microbial community have been observed. The relative abundance of Gp6, Gaiella, Nocardia, Herbaspirllum and Gp16 changed dramatically throughout the incubation period, which were either heavy metal tolerant or played crucial roles in modifying the chemical composition of heavy metals. This work contributes to an in-depth understanding of the effects of microplastics on the biochemical transformation of heavy metal contaminated soils, which will be valuable to the development of clean up strategy for soils with co-contaminant of microplastics and heavy metals.