Occurrence characteristics, source analysis, and risk assessment of microplastics in agricultural soils: A case study on Shihezi Reclamation Area, Xinjiang, China

Prolonged application of plastic mulch in farming led to considerable microplastics (MPs) accumulation in agricultural soils, endangering soil ecosystems and posing serious risks to human health. Xinjiang, with its long history of plastic film mulching, is considered a potential "hotspot" for microplastics research in China. However, the current understanding of the occurrence characteristics, risk levels, and pollution sources of MPs in the agricultural fields of Xinjiang remains limited. In this study, we investigated MPs in the Shihezi Reclamation Area of Xinjiang. The characteristics of MPs were identified using Laser Direct Infrared Spectroscopy. Additionally, the risks associated with soil MPs were assessed. The average MPs abundances in the 0-30, 30-60, and 60-100 cm soil layers across all soil samples were 7040 ± 814, 5653 ± 808, and 4457 ± 1102 n·kg, respectively. MPs abundance exhibited a positive correlation with cumulative years of plastic mulch application. 94.61 % of MPs were in the range of 20-100 μm. Polyethylene dominated soil samples (38.78 %), followed by polyurethane (18.09 %), comprising the predominant polymer types. Agricultural mulch film, slow-release fertilizer coating, plastic wastes in the farmland, deterioration and abrasion of drip irrigation tapes, and wear of automobile and agricultural machinery were the main sources of contamination from MPs inputs to the farmland soil. The study area uniformly exhibited Category I ecological risk, with no noncarcinogenic health hazards. Therefore, this study is crucial for elucidating MPs pollution levels and environmental risk in farmland.