Distribution characteristics of plastic film residue in long-term mulched farmland soil

Abstract

Soil contamination from film debris following the prolonged application of mulching film has emerged as a worldwide concern. However, the extent that mulching films contribute to soil microplastics, and the spatial distribution of soil contamination from film debris remain unclear. In this study, the cotton field in Xinjiang (China), which underwent film mulching for a prolonged period of 5–30 years, was selected as the research location. A total of 360 soil samples were collected, aiming to study the spatial distribution characteristics of mulching film debris pollution. The samples were extracted using the density flotation method combined with stereomicroscopic; the source, composition, abundance, and distribution characteristics of soil MPs were identified by the scanning electron microscopic, and Fourier transform infrared spectroscopic analyses. In soil mulched for a 30 year period, the abundance of microplastics across the studied soil depth (0–60 cm) was 78.51±2.57 n/(100 g). The μ-FTIR analyses revealed that the composition of the microplastics matched that of polyethylene materials. Therefore, plastic mulching could be inferred as a major contributor to microplastic pollution in agricultural lands. Overall, it is necessary to study the distribution characteristics of plastic film remaining for further study of plastic pollution in farmland soils. [Figure not available: see fulltext.]