Seasonal variations and risk assessment of PAHs in Xiamen: Insights into the impacts of local and long-range transport sources

Polycyclic aromatic hydrocarbons (PAHs) are among the most toxic pollutants in air pollution with severe health implications, yet their seasonal characteristics and health risk based on specific sources from local and long-range transport in coastal cities are insufficiently studied. This research presents a detailed seasonal analysis of 29 PAHs in atmospheric particulate matter across five districts of Xiamen, China. The study found clear seasonal variations due to monsoon climate, with the highest PAH concentrations observed in winter (mean 69.70 ng/m³), 2.9 times higher than in summer (mean 23.88 ng/m³). The higher winter concentrations are mainly attributed to the influx of pollution-laden air masses from northern China. In contrast, the reduced levels in summer might be due to frequent rainfall, stronger photochemical degradation and the dilution effect of clean air masses from the ocean. The main sources were transportation emission (32.1 %), petrogenic source (30.5 %), biomass combustion (28.5 %), and coal combustion (8.9 %). Health risk assessments indicated that winter posed the greatest health risks, with carcinogenic and mutagenic risks up to 5.35 times higher than in summer, particularly in districts like Jimei, where traffic-related PAHs contributed to 43.3 % of the total risk, while Oil spill-related emissions in Haicang were responsible for 50 % of the carcinogenic toxicity in that district. Women face higher health risks than men, with greater risks near transportation hubs and industrial areas. These findings underscore the impact of external pollution on Xiamen's atmospheric PAHs, emphasizing the need for targeted winter pollution control.