Microplastic in tropical island estuaries in China: Source identification and management framework development

This study investigates a comprehensive assessment of microplastic (MP) pollution in the contrasting estuarine systems of Hainan Island, China: the urbanized Nandu River Estuary and the less-developed Wanquan River Estuary. Analysis of surface water samples revealed an overall MP abundance ranging from 0.05 to 0.60 particles/m³. A notable finding was the significantly higher concentration in the Wanquan Estuary (0.32 ± 0.13 particles/m³) compared to the Nandu Estuary (0.17 ± 0.10 particles/m³), suggesting that tourism and agricultural activities may be more significant contributors than urbanisation alone in this context. Morphologically, MPs were predominantly linear and fibrous, with white and blue being the most common colors, and a size distribution concentrated in the 500-2000 μm range. Polymer composition analysis identified Polyolefins, polyester, and polyethylene as dominant, with signatures pointing to distinct anthropogenic sources for each estuary: packaging, textiles, and fisheries for the Nandu, and agricultural films and tourism-related waste for the Wanquan. Statistical correlations indicated that water temperature and pH enhanced MP suspension, while turbidity facilitated sedimentation. Source apportionment via Principal Component Analysis and Multiple Linear Regression confirmed these links, highlighting tourism (wet wipes, textiles), fisheries (abandoned gear), and inadequate waste management as primary pathways. The relatively low abundances, compared to global estuaries, potentially reflect the positive impact of Hainan's stringent plastic bans. However, the persistence of specific polymers underscores the need for continued, targeted management strategies. This research establishes a critical baseline for MP pollution in tropical estuaries and offers valuable insights for policy-making aimed at mitigating marine plastic pollution.