Driving factors of the distribution of microplastics in the surface soil of the typical uninhabited and habited areas in the Qinghai-Tibet plateau, China

Microplastics (MPs) are widely detected in the soil of the Qinghai-Tibet Plateau with increasing economic activities. However, studies concerning the driving factors affecting the presence of these surface soil MPs for the typical regions with different geographic conditions are still lacking. Here we chose three representative regions (Ali, Yushu, and Haixi) from east to west across the plateau to investigate the distribution and further explore the contributing factors of surface soil MPs. The Spearman rank correlation, Geodetector, Random Forest Regression and Principal Component Analysis were used to unveil how the driving factors influence MPs distribution across the plateau. The results revealed that the MPs abundance, type, size, color and polymer across the Ali, Yushu, and Haixi were different. Microplastic abundance was inversely correlated with the distance from roads and residential areas, but was positively related to precipitation. Moreover, traffic elements were the primary source of MPs pollution in the Ali and Yushu but residential activities were the leading source of MPs contamination in the Haixi. Besides, backward trajectory simulations suggested that atmospheric transport may also contribute to the presence of soil MPs in the representative regions. These results further indicated that different regions may require different measures for controlling MPs pollution in surface soil. This study provides new insights into the distribution and source of MPs and further offers valuable methodology for future research aimed at uncover driving factors contributing MPs pollution across different regions with various geographical conditions.