Co-occurrence of light microplastics and phthalate esters in soils of China

The terrestrial environment is both a critical source and sink for microplastics (MPs). However, further efforts into the risk assessment, management, and mitigation activities of MPs in the terrestrial environment were limited by the scant data on their occurrence. In this study, we investigated the co-occurrence and correlations of light MPs and phthalate esters (PAEs) in the soils of China's hotspots and non-hotspot regions. Light MPs and PAEs were detected in all agricultural and urban soils (n = 125). In soils from hotspots (Shihezi, Xinjiang) where intense plastic mulching was used, the concentrations of MPs and phthalate diesters (di-PAEs) were 650-36,450 pcs kg^-1 and 55.60-1236.64 μg kg^-1, respectively. In hotspots but not in non-hotspot regions of China, a positive correlation between MPs and PAEs was established, suggesting PAEs may serve as an indicator of MP contamination in hotspots. High quantities of MPs (1143-5911 pcs kg^-1) and PAEs (67.3-1236.64 μg kg^-1) were also detected in urban park soils, demonstrating a need for future research on MP in urban soils. In addition, the ubiquitous co-occurrence of MPs and PAEs in all 125 investigated soils revealed that potential joint toxicity, co-transformation, and co-transportation of MPs and PAEs should not be disregarded.