Fate, source, and ecological risk of microplastic in the surface sediment of the Beibu Gulf, the Northern South China sea

A large-scale investigation of the surface sediments in the Beibu Gulf was conducted in this study to reveal the contamination characteristics of microplastics in the surface sediments of the Beibu Gulf. The results showed that the abundance of microplastics ranged from 12.91 to 251.69 items/kg, dry weigh (DW), with an average abundance of 84.34 ± 51.85 items/kg (DW). The highest abundance of microplastics was found in the estuary of northwestern Hainan, influenced by the West Guangdong Coastal Current. The overall distribution of abundance showed a decreasing trend from nearshore to offshore. Microplastics in the surface sediments were predominantly in the form of fiber (87.51%), with a predominant white color. The polymer of microplastics in surface sediment was primarily polyester (43.43%). The main sources of microplastics include household items, textile products, food packaging, fishing activities, industrial activities, sewage discharges, and biochemical materials, of which household products and textile products are the most important sources. The results of the risk evaluation showed that the sediment of Beibu Gulf was contaminated with microplastics (pollution load index >1) and the polymer risk was at low to extremely high levels. The high abundance of microplastics and highly toxic polymers resulted in increased ecological risk. These findings highlight the urgent need to implement timely and effective measures to reduce the impact of intensive human activities on microplastic pollution. At the same time, the study data provide an important reference for future ecotoxicological investigations, pollution management strategies and microplastic policy development.