Background Microplastic (small plastic with the diameter < 5 mm) has been widely detected in soil worldwide, and soil microplastic pollution has become a globally recognized environmental issue. Soil and water loss is an important migration pathway of microplastics from soil to water. Soil properties, as intrinsic affecting factors of soil and water loss, can influence the migration of soil microplastics by affecting the rainfall infiltration and runoff process, leading to differences in the characteristics of soil microplastics under different land use practices. Yimeng Mountain area has severe soil and water loss, with a large amount of plastic film used, resulting in significant differences in the characteristics of soil microplastics.

Methods In this study, representative land uses in the Yimeng Mountain area, including arable land (peanut (Arachis hypogaea) land) and sweet potato (Ipomoea batatas) land, peach (Prunus persica) orchard, and forest land, were selected as the research subjects. Through field sampling and laboratory analysis, the abundance, diameter, perimeter, and area characteristics of microplastics in the soil were identified. Specifically, the density floatation method using saturated NaCl solution was used to extract microplastics from soil samples. Fluorescence type microscope was used to count the number of microplastics and take photos. The number, diameter, perimeter, and area characteristics of microplastics were obtained by visual analysis using software Image J. The impact of soil characteristics such as bulk density and porosity on microplastic features was analyzed using partial least squares regression.

Results 1) The average abundance of microplastics in peanut (A. hypogaea) fields and forests was significantly higher than that in peach orchards and sweet potato (I. batatas) fields. 2) Sweet potato (I. batatas) fields had the smallest average diameter, perimeter, and area of microplastics among the four land use types, measuring 49.0 μm, 104.3 μm and 991.9 μm², respectively. 3) The average diameter and area of microplastics in peach orchard soils were the largest among the four land use types, and were 57.9 μm and 2060.6 μm², respectively. 4) Overall, the abundance, average diameter, average perimeter, and area of soil microplastics were mainly influenced by soil bulk density, total porosity, capillary porosity, aeration porosity, and saturation water content. They were positively correlated with total porosity, capillary porosity, and saturation water content, and inversely correlated with soil bulk density and aeration porosity.

Conclusions The characteristics of microplastics varied in different land use soils in the Yimeng Mountain area and were affected by soil bulk density and porosity. The study results provide a clear understanding of the characteristics and influencing factors of microplastics in soils under different land use types in the Yimeng Mountain area. The research will provide a scientific basis for the prevention, control, and remediation of soil microplastic pollution.