Microplastics in the seawater of the Beibu Gulf, the northern South China Sea: occurrence, sources, and ecological risk

In this study, the occurrence, sources, and ecological risk of microplastics (>60 µm) in the surface and bottom seawater were investigated in the Beibu Gulf, the northern South China Sea. The average abundance of microplastics in surface and bottom waters was 1.35±0.93 and 0.79±0.50 items/m³, respectively. Microplastics in both surface and bottom waters were predominantly in the form of fragments, and mostly in green. The composition of microplastics in surface water was primarily poly (methyl methacrylate) (PMA), whereas in bottom water, polyethylene (PE) dominated. Positive matrix factorization (PMF) modeling revealed that the primary sources of microplastics were pipeline abrasion, fishing activities, plastic waste, landfill disposal, transportation, aquaculture, and construction activities. The pollution load index (PLI) indicated that the overall risk of microplastic pollution in the Beibu Gulf was low. Conversely, the polymer hazard index (PHI) for microplastics was relatively high. These data underscore the importance of timely and effective reduction of human-intensive activities contributing to microplastic pollution and provide valuable information for further research in microplastic ecotoxicology and biogeochemistry.