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Temporal Dynamics of Microplastic Pollution in the Meishe River: Decreasing Surface Water Abundance versus Increasing Sediment Accumulation
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Good news and bad news: a Chinese river had less microplastic floating in its water in 2025 than in 2020, thanks to better pollution controls, but the plastic that remains is breaking into smaller, harder to remove pieces and building up in the riverbed sediment. Since tinier particles can be easier for organisms (and eventually us, through food and water) to absorb, this shift matters even as overall risk stayed moderate.
A comprehensive understanding of the changes in microplastic pollution in urban rivers is a key prerequisite for effective pollution control and management. The Meishe River, the longest urban river in Haikou (Hainan Island, China), transports microplastic pollution from terrestrial to marine ecosystems. This study investigated the spatiotemporal distribution, characteristics, and ecological risks of microplastics by analyzing surface water and sediment samples collected from nine sites in 2020 and 2025. Microplastics were extracted via density separation and digestion, identified by Fourier Transform Infrared Spectroscopy (FTIR), and assessed for risk with the Pollution Load Index (PLI). Results showed a significant decrease in surface water microplastic abundance (from 1638.5 ± 796.1 to 601.5 ± 241.9 pieces·m⁻3, P = 0.001) but a concurrent significant increase in sediments (from 711.5 ± 537.6 to 1139.6 ± 610.8 pieces·kg⁻1, P = 0.010). Fragments dominated both compartments. A notable temporal shift occurred from larger (> 1.0–5.0 mm) to smaller (0.1–0.5 mm) particles. Primary polymers were polyethylene (PE), polypropylene (PP), polystyrene (PS), and polyethylene terephthalate (PET). Overall ecological risk was moderate, with a significant decrease in surface water PLI (P = 0.001). These findings indicate targeted regulations and enhanced wastewater management effectively reduce urban river microplastic contamination. Limitations include potential seasonal bias between sampling campaigns, requiring future long-term monitoring.
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Occurrence, potential sources, and ecological risk assessment of microplastics in the inland river basins in Northern China
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Researchers surveyed microplastic pollution in a typical urban river system in Northern China, examining both surface water and sediment samples. They found that river sediments contained dramatically more microplastics than surface water, acting as a sink for this pollution, with polypropylene and polyethylene being the most common types. The study suggests that small fiber and fragment-shaped particles under 0.5 mm dominate these environments, likely originating from everyday plastic products and wastewater discharge.
Preferential accumulation of small (<300 μm) microplastics in the sediments of a coastal plain river network in eastern China
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Researchers found that small microplastics (under 300 micrometers) preferentially accumulated in the fine sediments of a coastal plain river network in eastern China, explaining why they are underrepresented in ocean surface trawl surveys. The results suggest that river networks act as filters retaining the smallest plastic particles, contributing to the "missing plastics" in ocean mass balance estimates.
Research Progress of Microplastic Pollution Status and Risk Assessment of Typical Rivers in China
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Rivers across China carry substantial microplastic loads, and this review finds that abundance is closely tied to population density, with urban rivers showing higher concentrations than rural ones. More than 60% of microplastics detected in most rivers were smaller than 1 mm — the size range most readily ingested by aquatic organisms and most difficult to remove by conventional treatment. The authors identify sewage plants, surface runoff, and atmospheric deposition as the main sources, and flag gaps in current risk assessment frameworks for river microplastics.
Spatial Distribution and Source Apportionment of Microplastics in a Typical Urban River: A Case Study of Pingshan River, Shenzhen, China
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Researchers found high levels of tiny plastic particles (microplastics) in both the water and sediment of an urban river in China, with construction sites nearby making pollution worse. The good news: despite the large amounts found, the specific types of plastic detected were classified as lower risk based on their chemical makeup—but since these waterways can connect to drinking water sources and the food chain, tracking where this pollution comes from is an important step toward reducing our everyday exposure to plastics.
Microplastic reorganization in urban river before and after rainfall
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Researchers monitored microplastic abundance, stability, and pollution risk in the Qing River in Beijing before and after rainfall events. Rainfall diluted microplastic concentrations by increasing flow velocity and opening barrages, but altered the size distribution by preferentially transporting smaller particles, shifting the composition of the remaining microplastics.
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