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Microplastic distribution, historical accumulation and influencing factors in sediments of Caohai Lake, a plateau lake in Southwest China
Summary
Scientists studying a remote mountain lake in China found tiny plastic particles buried in its sediment layers going back years, showing that even isolated, high-altitude waters aren't safe from plastic pollution. Some of the plastics found, like PVC and polystyrene, are considered especially harmful to ecosystems, and since these lakes often feed into drinking water and food sources, this pollution could eventually work its way into what we eat and drink. The findings matter because they show plastic contamination is driven by nearby human activity and development, meaning better waste management could help protect these vulnerable water sources going forward.
Microplastics (MPs) are broadly recognized as ubiquitous contaminants in aquatic environments and pose considerable risks to ecosystems worldwide. Lake sediments act as important sinks for MPs, recording their long-term accumulation and reflecting historical anthropogenic influences. However, the accumulation characteristics and influencing factors of MPs in plateau lake sediments remain poorly understood. This study used sedimentological and geochemical approaches to analyze surface sediments and sediment cores from Caohai Lake on the Yungui Plateau to investigate MP pollution, ecological risks, and the factors governing their accumulation. MP abundance ranged from 200 to 1300 items/kg, with higher levels observed in surface sediments (average of 873 items/kg) than in the sediment core (average of 690 items/kg). MPs were dominated by polyethylene terephthalate (PET) fibers and polyethylene (PE)/polypropylene (PP) films, with most particles smaller than 0.5 mm. Moreover, detection of high-hazard polymers, including polyvinyl chloride (PVC) and polystyrene (PS), resulted in high zone-averaged polymer hazard index (PHI >1000) and potential ecological risk index (PERI) values. Meanwhile, the zone-averaged pollution load index (PLI = 2.0) indicated a relatively low overall pollution level. Geochemical analysis of the 0–50 cm sediment core identified four sedimentary units recording historical changes in the sedimentary environment. The vertical distribution of MPs displayed pronounced fluctuations, indicating marked temporal variations in MP accumulation. Integrating sedimentological, geochemical, and socioeconomic information reveals that these variations are jointly driven by fluctuations in external inputs, sedimentary environmental conditions, regional socioeconomic development, and environmental management. These findings provide novel insights into the historical evolution and driving mechanisms of MP accumulation in plateau lake sediments.