Microplastics in beach sediments of the Northern Bay of Bengal, Bangladesh: Insights into occurrence, distribution, pollution indices, and ANN-based risk modeling

Microplastic (MP) pollution in marine ecosystems is a global concern and is increasingly recognized as a pressing issue in the coastal environments of Bangladesh. This study investigates the occurrence, abundance, distribution, and potential risks of MPs in beach sediments of Cox's Bazar and Kuakata beach in the Northern Bay of Bengal, Bangladesh. MPs were prevalent across Cox's Bazar and Kuakata beaches, Bangladesh, with Kuakata exhibiting higher MP abundance (769 ± 271.56 items/kg) than Cox's Bazar (350 ± 163.25 items/kg). Fiber MPs dominated, comprising 77% at Cox's Bazar and 74% at Kuakata. Most MPs were 0.1-0.5 mm in size, indicating debris weathering as a primary source. Colors varied, with blue and black MPs dominating. Low-density polyethylene (LDPE) and polypropylene (PP) were the predominant polymers, comprising 46% of MPs in Cox's Bazar and 47% in Kuakata. Pollution Load Index values exceeded the recommended value (PLI>1) for Cox's Bazar and Kuakata beaches, signifying notable pollution levels. Polymeric hazard analysis indicated hazards ranging from low to considerable at both sites. However, the ecological Risk Index (ERI) values indicated site specific variations in contamination intensity, with Cox’s Bazar showing generally lower risk levels whereas Kuakata exhibited a wider range of risk from low to very high. Targeted mitigation is essential to address environmental risks.