Microplastics in Surface Water in the Yangtze River, China: Basin-Wide Observation, Multiple Ecological Risk Assessment and Sustainability

The Yangtze River Basin (YRB) is an important source of marine microplastics (MPs). However, unscientific research methods in previous studies have led to inaccurate estimates of the occurrence and ecologic risk of MPs. This study aimed to comprehensively assess the distribution and ecological risks of MPs in the YRB, through investigating the occurrence of full-size MPs in the surface waters of the YRB over 3 years. The Size Effect was developed based on the impact of size and MP-carried pollutants on human health, and combined with multiple methods to evaluate the potential risks of MPs. The average MP abundance in the YRB was 8797 ± 12,281 items/m3, dominated by polypropylene and fragments. The small MPs (<0.3 mm; 92.52%) were the driving factor of the MP spatial heterogeneity. Interestingly, the Three Gorges Dam significantly altered the MP distribution and weakened the MP transportation. Agricultural activities, wastewater treatment plants, and atmospheric deposition were the main sources of MPs in the YRB. Multiple ecological risk assessment indicated that the MP risk in the YRB was at the middle–low level. This study addresses the occurrence of <0.05 mm MPs in the YRB, provides insights for MP risk assessment, and serves as a reference for sustainable management.