Microplastics in coastal surface waters of Northern Vietnam: Characteristics, seasonal distribution, APCS-MLR-based...

Microplastic pollution has become an increasing concern in marine ecosystems because of its potential impacts on aquatic organisms and human health. However, information on the occurrence, source apportionment, and ecological risks of microplastics in Vietnam's coastal surface waters remains limited. This study investigated the characteristics, seasonal variability, source apportionment, and ecological risks of microplastics in the coastal surface waters of Northern Vietnam. Surface water samples were collected from eight representative sites across six coastal provinces during the rainy and dry seasons. The results revealed a statistically significant seasonal difference in microplastic abundance (p < 0.001), with higher mean concentrations in the dry season (61.61 ± 70.68 items/m³) than in the rainy season (18.51 ± 14.40 items/m³). Small-sized microplastics (< 809 μm) dominated in both seasons, with fibers and fragments being the most prevalent shapes. A total of 25 polymer types were identified, among which polyethylene terephthalate (PET) was the dominant polymer, accounting for 19.88-33.53% of the total microplastics. Ecological risk assessment revealed contrasting risk levels across the study area, ranging from low contamination based on pollution load index values (1.58-2.20) to extremely high ecological risk based on the potential ecological risk index (1538.93-1901.01). APCS-MLR source apportionment identified four major sources of microplastics, with packaging-related materials as the predominant contributor (49.26%). This study provides scientific evidence on the seasonal dynamics, source apportionment, and ecological risks of microplastics in coastal surface waters along Vietnam's northern coastline and supports the development of targeted monitoring and management strategies.