Driving Factors and Potential Offshore Pollution of Plastic Mulch Residue in Farmland in the Yellow River Delta, China

Abstract

Agricultural pollution plays a major role in the Yellow River Delta in China. Mulch residue from farmlands pollutes surrounding soil and near-shore waters. There is a lack of knowledge regarding the environmental pollution effects of mulch residue in this region. This study examined mulched farmlands within 5 km of the main entering-sea rivers of this region combining soil aggregation and microbial community characteristics and using analytical methods to identify the key drivers of mulch residue characteristics and potential offshore pollution. Mulch residue pollution in the study area was found to be heavily present (mean value of 51 kg/hm2), posing a high risk of offshore pollution in southeast and northwest coastline. Large mulched fields with low residue levels and small debris showed a scale effect in mitigating mulch residue pollution. PBAT mulch usage was prone to the transport of small-sized residues with PE and other hard-to-degrade substances, indicating an increased offshore pollution risk. Large agglomerates in the soil, formed after using PE mulch, had poor water stability and low soil organic carbon content. Mulch residues significantly reduced the abundance of the soil fungi Ascomycota and Basidiomycota. This study provides a reference for controlling mulch residue pollution and managing offshore plastic pollution.

Keywords: driving factor, mulch residue, offshore pollution risk, the Yellow River Delta