Accumulation of soil microplastics and phthalate esters in nine typical Chinese croplands using plastic mulch film

Plastic mulch film (PMF) can release microplastics (MPs) and phthalate esters (PAEs) into agricultural soils. These materials can contaminate the food chain, thereby posing a potential risk to human health. However, inconsistent methodologies hinder cross-regional comparisons of MP and PAE concentrations in agricultural soils, preventing an accurate assessment of the actual risk. To address this knowledge gap, a harmonized analysis of MPs and PAEs was conducted in soil across nine typical mulching region in six provinces of China (Gansu, Inner Mongolia, Liaoning, Shandong, Xinjiang and Zhejiang). The results showed that the abundance of MPs in the 0–30 cm soil layer ranged from 2.4 × 106 to 1.5 × 107 items m−2 (equivalent to 5.5 × 103 to 4.9 × 104 items kg−1 soil), with the highest abundance in Shandong and the lowest in Xinjiang. These MPs were mainly composed of rubber, polyolefin, polyester, resin, polystyrene, fluoropolymer, polyamide and polyurethane, of which polyolefin (primarily PMF-derived) accounted for up to 35%. Additionally, six PAEs (di(2-ethylhexyl) phthalate, diisobutyl phthalate, dibutyl phthalate, di-n-pentyl phthalate, diethyl phthalate and dimethyl phthalate) were detected, with total residues ranging from 3.6 to 22.3 mg·kg−1. It was estimated that the total PAE input from PMF constitutes < 0.1% of the measured PAEs at all the sampling sites. Overall, these findings indicate that PMFs are not the main contributor to MP and PAE contamination in agricultural soils under continued PMF application. While removal and recycling of PMF is essential in reducing PMF-derived MP accumulation in soil, further research into other sources is required to establish impactful mitigation strategies and regulations.