Microplastic Pollution in China’s Inland Waters Surpasses Coastal Seas under Anthropogenic Pressures

Microplastics are emerging as a global environmental challenge, yet the role of inland waters in shaping their distribution and risks has remained largely overlooked. By synthesizing over 13,000 records from 500 studies across China’s 10 river basins and 4 seas, we show that inland waters are not only conduits but also dominant sinksrivers exhibit 0.9–7.7 MP L–1 and reservoirs exhibit 1.2–8.3 MP L–1, both significantly exceeding adjacent seas (0.1–2.2 MP L–1). Fibers and fragments dominate (>60%) morphological profiles, while polymer compositions mirror intensive human activities, linking urban emissions and agricultural plastic use directly to freshwater burdens. Machine learning (R2 = 0.85) reveals that population density and night-time lights are the strongest predictors of abundance, surpassing climatic and geographic variables, underscoring the primacy of anthropogenic pressures in shaping spatial heterogeneity. Ecological risk assessments further demonstrate that 33.1% of freshwater samples exceed medium-risk thresholds (RQ > 0.1), and 2.4% reach high risk (RQ ≥ 1), in stark contrast to uniformly low-risk marine sites. These findings challenge the ocean-centric paradigm of plastic pollution, positioning inland waters as critical hotspots of accumulation and risk, and highlight the urgent need for integrated, source-to-sink management strategies across the land–freshwater–ocean continuum.微塑料（Microplastics）已成为全球性环境挑战，然而内陆水域（inland waters）在调控其分布与风险方面的作用却长期被忽视。本研究通过整合中国10大流域与4大海域共500项研究的13000余条记录，结果显示：内陆水域不仅是微塑料的输运通道，更是主要的汇——河流中微塑料浓度为0.9~7.7 MP·L⁻¹，水库中为1.2~8.3 MP·L⁻¹，均显著高于邻近海域（0.1~2.2 MP·L⁻¹）。纤维与碎片类微塑料占形态组成的60%以上，其聚合物组成与高强度人类活动高度匹配，直接关联城市塑料排放、农用塑料使用与淡水微塑料负荷。机器学习（R²=0.85）分析表明，人口密度与夜间灯光数据是微塑料丰度的最强预测因子，其解释力超过气候与地理变量，凸显了人为压力在塑造微塑料空间异质性中的主导地位。生态风险评估进一步显示，33.1%的淡水样品超过中等风险阈值（风险商RQ>0.1），2.4%达到高风险等级（RQ≥1），与风险水平普遍较低的海洋采样点形成鲜明对比。本研究结果挑战了塑料污染以海洋为中心的研究范式，明确内陆水域是微塑料累积与风险的关键热点区域，并强调亟需在陆地-淡水-海洋连续体中推行一体化源-汇管理策略。