Microplastic risk assessment in freshwater and marine sediments of China

Microplastic (MP) pollution has emerged as a critical environmental issue, particularly in China—the world's largest plastic producer. This study provides a comprehensive study of MP abundance, polymer distribution, and analytical methods applied to freshwater and marine sediments across China. Various analytical approaches, including optical and spectroscopic techniques, have enhanced the accuracy and reliability of MP identification. However, the density separation method commonly used for MP extraction from sediments remains non-standardized and dependent on limited salt solutions, introducing potential uncertainty to results. Different MP polymers exhibit distinct toxicity profiles, largely determined by their monomer composition and particle size. To assess ecological risks associated with MP exposure, a semi-quantitative risk assessment model was developed. The model ranks MP risks across China based on potential health concerns, incorporating factors such as concentration, degradability, particle size, and chemical toxicity. Six environmental categories were evaluated according to their final risk scores. Sensitivity analysis identified the hazard factor as the most sensitive parameter, followed by mean particle size, degradation status and microplastic concentration. This integrated framework enables the quantification of MP abundance, spatial distribution, and associated health risks, supported by visualization and spatial mapping to identify ecological hotspot regions and high-risk provinces across China.