Microplastics (MPs), a new type of pollutant, pose a significant threat to the environment at high concentrations. One of the primary sources of MPs in the ocean is river runoff, highlighting the need to investigate the spatial and temporal variations of MPs in rivers that flow into the sea, as well as their contributing factors. In this study, we analyzed MPs distribution and their influence factors in the Lincheng River, China. The Lincheng is the second largest river in Zhoushan island that directly flows into the ocean. MPs in the river water and sediments were detected during the wet season (July 2021), the dry season (November 2021) and the typhoon season (September 2021), and MPs were present in all reaches of the river. The abundance of MPs in the river was moderate compared to other studies, with the river water exhibiting a concentration of 15 ± 2.64 n/L and the sediment containing 318.24 ± 49.53 n/kg of MPs. In surface water, the most commonly found MP was blue man-made cellulose (CE), while the sediment contained mostly fragments of polypropylene (PP) and polypropylene polyethylene blends (PP + PE) in blue and green colors. The abundance of MPs showed significant seasonal differences, with higher abundance during the wet season compared to the dry season and typhoon period. Furthermore, local construction activities may contribute to higher MP abundance. To explore the influence factors of MPs, the Basin Development Index (BDI) was proposed, and a positive correlation between BDI and MP abundance was founded. This correlation indicates that the increase in land use for construction highly contributes to the MP pollution. In conclusion, future long-term monitoring of the abundance of MPs in the Lincheng River is necessary.

This study investigates the pollution characteristics and environmental risks of crushed microplastics (MPs) generated during plastic recycling, emphasizing their adsorption capacity for heavy metals, particularly lead (Pb). SEM-EDS analysis revealed that crushed MPs exhibit significantly higher adsorption capacity than primary MPs due to their larger surface area and more available adsorption sites, including oxygen-containing functional groups. The adsorption behavior of MPs was influenced by key factors such as MP size, MP quantity, pH, salinity, and biofilm formation. Smaller MPs demonstrated higher adsorption efficiency, while elevated pH enhanced Pb adsorption. Conversely, increased salinity reduced adsorption due to competition for adsorption sites. Increasing MP concentrations improved Pb removal efficiency, but higher MP quantities led to a decrease in maximum adsorption capacity, demonstrating a trade-off between removal efficiency and adsorption capacity. Isothermal adsorption experiments revealed that Pb adsorption on MPs follows a multi-layer mechanism, best characterized by the Freundlich model. The adsorption capacity increased nonlinearly with Pb concentration and stabilized as surface sites became saturated. The formation of biofilms on MPs further enhanced their adsorption capacity by providing additional functional groups and facilitating multi-layer adsorption, increasing ecological risks. Adsorption kinetics were best described by pseudo-second-order and intra-particle diffusion models, indicating chemical adsorption and boundary layer diffusion as dominant mechanisms. Magnetic Fe₃O₄ nanoparticles demonstrated a high recovery efficiency of 99.3% for MPs, highlighting their potential for environmental remediation. However, the presence of adsorbed Pb slightly reduced recovery performance, emphasizing the need to optimize recovery conditions for maximum efficiency. These findings underscore the dual threat posed by crushed MPs: their capacity to adsorb and concentrate harmful substances, increasing ecological toxicity, and the challenges associated with their recovery. This research provides critical insights into mitigating MP pollution and developing effective recovery strategies under realistic environmental conditions.