Microplastic and Heavy Metals Distributions in Urban Rivers Sediments, China

This study investigated the distribution of microplastics and heavy metals, along with the interaction between the two in the sediments of urban rivers in China. Results showed that the abundance of microplastics ranged from 2412 ± 187.5 to 7638 ± 1312 items kg⁻¹ dry sediment across different survey stations, with an average abundance at (4388 ± 713) items kg⁻¹ dry sediment. Upon further categorization, it was found that transparent fragments were the primary color and type of microplastics present. The potential ecological risk index (RI) of heavy metals in sediments suggested a low level of ecological risk within a majority of the urban rivers studied. Cd was identified as the main potential ecological risk factor in the sediments of the studied areas. There was a relatively good significant linear relationship between the RI of heavy metals and the abundance of microplastics, bolstering the linkage between these two environmental pollutants. However, the concentrations of heavy metals in microplastics were not dependent on their corresponding contents in sediments. In fact, the concentration of Cu, Cd, and As in microplastics were higher than those in the sediments. This finding confirmed that microplastics could serve as carriers of heavy metals and introduce potential risks to aquatic wildlife and human through the food chain.