Microplastic pollution in water and sediment in the Henan section of the Yellow River based on the MultiMP comprehensive evaluation method

This study investigates the current state of microplastic (MP) pollution and ecological risks in the middle and lower reaches of the Yellow River, focusing on the Henan section. Using the advanced MultiMP risk assessment method, both surface water and sediment environments were comprehensively evaluated. Results indicate that MPs were detected in both environments, with surface water abundance ranging from 3.35 to 12.6 n/L and sediment abundance from 206 to 1647 n/kg. In terms of the main characteristics of MPs, the most common particle size ranged from 25 to 150 μm; fibrous shapes were the most abundant in both surface water and sediments; transparent MPs had the highest proportion in terms of color; and in terms of polymer composition, polyethylene (PE) and polypropylene (PP) were the main polymers found in surface water, while PE and polyethylene terephthalate (PET) were more common in sediments. Environmental factors influencing the MP distribution were also investigated. The abundance of MPs in surface water was closely related to total phosphorus (WTP) and total nitrogen (WTN), while the abundance of MPs in sediments was closely associated with the sediment particle size. MultiMP assessment results show medium risk for surface water and high risk for most sediments in the Henan section of the Yellow River Basin, with differing main factors affecting risk levels in the two environments. These findings fill regional research gaps and provide data support and theoretical foundations for effective MP pollution management in the Yellow River Basin.