Response of soil biochemical properties and ecosystem function to microplastics pollution.

Microplastics (MPs)-induced changes in soil nutrient cycling and microbial activity may pose a potential risk to soil ecosystem. Although some studies have explored these topics, there is still a large space for exploration and a relative lack of research on the mechanism by which soil health and its functions are affected by these changes. Thus, this study investigated the effects of polyethylene (PE) MPs with two particle sizes (13 μm and 130 μm) at five concentrations (0%, 1%, 3%, 6% and 10%, w/w) on soil biochemical properties and ecosystem function. The findings revealed that the exposure to 13 μm MPs significantly reduced soil respiration (Res) rate, β-glucosidase (Glu) and catalase (CAT) activity, which accompanied with enhanced urease activity and decreased soil pH, available phosphorus (AP), dissolved reactive phosphorus (DRP), dissolved organic carbon (DOC) and available potassium (AK) content in most cases. However, 130 μm MPs exerted negligible influence on the DOC and DRP content, Glu and CAT activity. High concentrations of 130 μm MPs significantly reduced soil pH, total dissolved nitrogen (TDN), AP and AK content, but significantly increased soil Res rate. Overall, soil ecosystem function was significantly reduced by the addition of MPs. The Res rate, soil AP and DRP content and Glu activity were the most important predictors of soil ecosystem function. We found that the risk posed by MPs to soil ecosystem function was dose-dependent and size-dependent. These findings underscore that MPs can alter soil functions related to soil nutrient cycling and provide further insights into MPs behavior in agroecosystems.