Polycyclic aromatic hydrocarbon pollution and risk assessment in semi-enclosed bays

Limited water exchange in semi-enclosed bays promotes the accumulation of polycyclic aromatic hydrocarbons (PAHs). This review synthesizes data from 52 peer-reviewed studies (1999–mid-2024) to evaluate PAH contamination in water, sediment, and fish across six Chinese semi-enclosed bays. Pollution levels and ecological risks were assessed using widely accepted classification and toxicity threshold guidelines. Documented PAH sources include industrial discharges in Bohai Bay, petrogenic inputs in Jiaozhou Bay, fishing boat activities in Xiangshan Bay, mixed combustion in Hangzhou Bay, agricultural runoff in Daya Bay, and vehicle emissions in Xiamen Bay. Although decreasing PAH trends were observed in Daya Bay and Hangzhou Bay over the past two decades, these findings are based on limited studies and should be interpreted cautiously. Source apportionment using PCA-MLR (principal component analysis-multiple linear regression) in Daya Bay water attributed 52 % of PAHs to vehicle emissions, 33 % to coal combustion, and 15 % to biomass burning, while PMF (Positive Matrix Factorization) analysis in Xiangshan Bay sediments indicated contributions of 38 % from oil spills, 25 % from gasoline combustion, 22 % from diesel emissions, and 15 % from biomass combustion. Overall, PAH pollution in Chinese semi-enclosed bays ranges from low to moderate, with ecological risks remaining low to moderate in water and sediments based on the Mohammed and Baumard scales, respectively. Although no fish samples exceeded the carcinogenic risk threshold (>10⁻⁴), further research is needed to assess long-term human health risks through fish consumption. This review provides updated insights to guide effective bay management and pollution mitigation strategies. • Systematic review of PAH pollution in semi-enclosed bays over the past 25 years. • Ecological risks are low to moderate in water and sediments. • 2–3 ring PAHs dominate fish muscle tissue. • Nationwide long-term PAH monitoring in semi-enclosed bays is advised.