The occurrence and effect of altitude on microplastics distribution in agricultural soils of Qinghai Province, northwest China

Microplastic (MPs) is a new type of environmental pollutant that has been widely detected in recent years. It is one of the main environmental problems faced by the global ecosystem and has attracted widespread attention. However, few studies have focused on the occurrence and distribution of MPs in agroecosystems. Therefore, Qinghai Province, a typical northwest region of China, was selected as the research area to study the distribution characteristics of MPs in agricultural soils in the low-altitude areas. The results indicated that MPs were detected in all soil samples. The abundance of MPs in agricultural soils in Qinghai Province ranged from 240 to 3660 items·kg. MPs with size less than 0.5 mm dominated, accounting for 50% of the total MPs. The main types of MPs were film and fiber, accounting for 67% and 29% respectively. It was proved that the use of mulching film and sewage irrigation are the main sources of MPs, and the recovery and treatment of agricultural waste can reduce MPs pollution. At the same time, the spatial distribution characteristics of MPs in the soil of Qinghai Province were analyzed, and the results showed that the heavily polluted areas of MPs were mainly concentrated in the densely populated areas in the east of the province. In addition, the influence of altitude on MPs abundance was investigated, and there was a negative correlation between altitude and MPs abundance, and ultraviolet light may accelerate the aging and degradation of MPs. This study revealed the distribution characteristics of farmland soil pollution in typical northwest China, and provided an important theoretical basis for the subsequent study of MPs in agricultural ecosystems.