Spatial distribution, source identification, and risk assessment of polycyclic aromatic hydrocarbons and their alkylated derivatives in China's coastal zones

Polycyclic aromatic hydrocarbons (PAHs) and their alkylated derivatives (A-PAHs) have posed significant threats to coastal ecosystems due to their toxicity and persistence. To clarify their environmental behavior, sources, and ecological risks in China's coastal zones, this study collected seawater and surficial sediment samples from major bays and estuaries. We quantified 16 U.S. EPA priority parent PAHs (P-PAHs) and 12 A-PAHs, with waterborne concentrations of Σ₁₆P-PAHs and Σ₁₂A-PAHs varying in the range of 13.5-2078 ng/L and 11.3-1876 ng/L, respectively. Both Σ₁₆P-PAHs and Σ₁₂A-PAHs showed the highest concentration in the Yangtze River Estuary. In surficial sediments, the concentration ranges of Σ₁₆P-PAHs and Σ₁₂A-PAHs were 1.23-213 ng/g dry weight (dw) and 0.51-332 ng/g dw, respectively, with the highest concentrations detected in the East China Sea coast. Principal component analysis and positive matrix factorization were employed to identify the primary sources of PAHs and their alkylated derivatives. Seawater-associated P-PAHs and A-PAHs were mainly affected by petroleum/shipping activities, while in sediments, the target chemicals were affected mainly by petrogenic, coal combustion, and biomass burning. Ecological risk assessment showed that most seawater monitoring sites posed low ecological risks, but localized hotspots exhibited medium to high risks due to occurrences of high-molecular-weight PAHs. In sediments, some A-PAHs generally posed risks in nearshore areas. Results of Toxicity Potential Index calculations showed that 2-Methylnaphthalene, 1-Methylnaphthalene, Benzo[g,h,i]perylene, and 1,3-Dimethylnaphthalene required priority attention in China's coastal zones.