Characterization and source apportionment of harbor-derived atmospheric PAHs and the potential risk for public and marine ecosystem health.

Harbor emissions introduce carcinogenic polycyclic aromatic hydrocarbons (PAHs) into the marine environment, posing significant risks. This study investigated the distribution, sources, and risks of 16 priority PAHs in the atmosphere of Tianjin Harbor, one of the world's largest industrial harbors in northern China. A one-year sampling campaign from June 2020 to May 2021 was conducted to collect 35 samples for TSP, PM2.5, and gas phase, respectively, with surrogate recoveries ranging from 75%-125%. Annual mean total PAH concentrations in TSP, PM2.5 and gas phase were successively 104.49 ± 88.06 ng/m3, 56.19 ± 49.93 ng/m3, and 246.34 ± 169.30 ng/m3, with peak levels occurring in winter. The partitioning mechanism (slopes > -0.6) was dominated by the absorption into organic matter based on the gas-particle partitioning analysis, indicating strong local source influence. Local combustion sources, including biomass/coal burning (dominant in winter) and vehicle/ship emissions (year-round) were identified as the main contributors based on convergent evidence from PSCF, diagnostic ratio analysis, and positive matrix factorization (PMF). The incremental lifetime cancer risk (ILCR) from inhalation exposure exceeded the acceptable level of 10-6, with >99% of Monte Carlo simulations indicating a potential carcinogenic risk. The estimated dry deposition flux of total PAHs (ΣPAHs 138.26 ± 114.87 μg/m2/day) was higher than values reported for other coastal regions, implying the substantial input to the adjacent Bohai Sea. These findings underscored the dominance of local combustion emissions and the associated health risks, while suggesting potential ecological concerns related to atmospheric PAH deposition, providing a scientific basis for targeted mitigation measures in major industrial harbors.