Microplastics in inland freshwater environments with different regional functions: A case study on the Chengdu Plain

As an emerging pollutant, microplastic has been demonstrated to widely cover water and sediments in marine and freshwater environments globally. Due to the differences in the regional functions of cities, the abundance and characteristics of microplastic pollution in rivers are different. Taking the Minjiang River as the research object, which flows through the Chengdu Plain, the abundance, composition, shape, and size of microplastics in the water and sediments of the Minjiang River were investigated. The results showed that serious microplastic pollution occurred in the Chengdu section of the Minjiang River, with an abundance ranging from 6.11-44.08 n/L in the water and from 573.84-2878.97 n/kg in the sediments. By using the "regional function index (Q)", the relationships between the characteristics of microplastic pollution and regional functions were analyzed. Areas with a high Q proved to be more polluted by microplastics. Densely populated areas with large construction areas and high human activity intensity tended to generate microplastics with larger sizes and a more fiber-like shapes. Rayon (RA) and nylon (PA) were identified as typical urban microplastics, while polypropylene (PP) and polyethylene (PE) were identified as typical agricultural microplastics. This study elucidated the microplastic pollution in the Chengdu section of the Minjiang River, a tributary in the upper reaches of the Yangtze River. It also provided a new direction for the study of microplastic pollution characteristics of freshwater environments with different regional functions and microplastic pollution source control.