Microplastics distribution and pollution characterization in two typical wetlands on the Qinghai-Tibet Plateau, China

The wetlands of Qinghai-Tibet Plateau (QTP) have important ecological functions on biodiversity conservation and water resources protection, but the pollution and risk of microplastics in those wetlands remains elusive. Herein, the character, source, ecological risk of microplastics in two typical wetlands for 40 samples of QTP were investigated. The results demonstrated that the average abundances of microplastics in surface water of Nianchu river wetland and Maidika wetland were 1615 f 1505.8 items/m3 and 325 f 426.9 items/m3, respectively, while the sediment of them were 680.7 f 550.1 items/kg, 322.8 f 351.6 items/kg, respectively. Microplastics in surface water and sediments were predominantly fragments (Nianchu river wetland), film and sphere (Maidika wetland), transparency, and 100-500 mu m, respectively. Polypropylene was the main types in QTP wetlands based on the intelligently identified by a machine learning algorithm (accuracy of 0.977). Residents, resident's life, tourist flow, agricultural and fishery activities are the main sources of microplastics in the wetlands. In addition, the abundances of microplastics have positively correlation with total nitrogen in water samples, annual precipitation, and nighttime light index. Compared with the incomplete parameters of other algorithms, Potential Ecological Risk Index combined microplastics abundance and type to give a more reasonable assessment of the microplastics risk level of QTP wetlands. That is, 88.9% of surface water and all sediment microplastics pollution are at low risk. However, attention should be paid to the sources of microplastics brought by tourism and residential life. The study is beneficial to supplement the data of microplastics pollution in the wetland areas of Qinghai-Tibet Plateau.