Microplastics in the Typical Mulched Farmland of Sichuan Province: Characteristics That Vary Across Farming Scales and the Risk Significantly Contributed by Priority Polymers

Microplastics (MPs) in agricultural soils pose risks to human health in their potential accumulation along the food chain, and their characteristics require further understanding to implement targeted measures. This study investigated the MP characteristics in typical mulching soils from different farming scales in Sichuan Province, which is one of China’s key agricultural regions, and it also innovatively measured the ecological risk by incorporating size into assessments. The investigated sites showed average microplastic abundances of 19696.81 ± 13226.89, and these were dominated by small-sized ethylene–propylene copolymer (E/P), polypropylene (PP), and polyethylene (PE) particles in yellow-to-brown and black-to-shallow-gray soil. Size-considered evaluation suggested that most of the sites were at a high level of risk. It was found that microplastic pollution varies with farming scales. Larger-scale farming sites primarily received MPs from plastic mulching, while smaller-scale sites were likely affected by a range of non-agricultural sources. The risk assessment showed significant contributions from polyamide (PA) and polyphenylene sulfide (PPS). These results indicate that environmental management strategies should tailor source control measures according to agricultural scales and prioritize high-risk polymers, as well as that MP risk evaluations should include “size” along with “pollution load” and “chemical composition” to better reflect the impact of MPs on ecosystems.