Characteristics of microplastics in dryland soils after long‐term film mulching and the effect of cropping type in western Liaoning Province, China

Abstract

AbstractMicroplastic (MP) pollution poses a significant environmental challenge on a global scale. In the semi‐arid region of western Liaoning, China, agricultural films have been widely utilized to enhance crop production over an extended period. However, there is a scarcity of research on the presence of MPs in the soil of farmlands in this area. Consequently, a total of 25 dryland soil samples from western Liaoning that had been mulched for more than 10 years and had been used to grow a variety of crops were gathered for the current study. The abundance, particle size, shape, and potential sources of MPs were examined, and the impact of different crop varieties on MPs characteristics was investigated. MPs abundance ranged from 6960 ± 1939 to 34,710 ± 9974 n kg−1, with the average and median of 14,305 ± 7015 and 12,270 ± 1621 n kg−1. MPs with sizes of less than 0.05, 0.05–0.1, and 0.1–0.4 mm were found in 42.7%, 33.8%, and 18.8% of cases, respectively. The most common shapes were fragments, microbeads, and films, with percentages of 47.1%, 22.3%, and 17.9%, respectively. A total of three polymers were found: polyethylene, polypropylene, and polystyrene in a proportion of 44.8%, 43.7%, and 11.5%, respectively. Based on the shape of the MPs, principal component analysis and cluster analysis revealed that the primary sources for MPs may be agricultural mulch, irrigation water, and the weathering of hard plastics like agricultural packaging. Compared to other crop types, soils growing sweet potato and peanut had significantly higher MP abundances. Moreover, soils growing sweet potato had significantly higher percentages of MPs with 0.05–0.1 mm particle size. Regardless of the crop type grown, fragments are the most common shape, while the proportion of other shapes varies depending on the crop type. The aforementioned findings suggest that MP pollution in farmland soil in western Liaoning is more severe and that the kind of crop cultivation affects the characteristics of MPs in the soil.