Ambient PM2.5-bound polycyclic aromatic hydrocarbons in Ningbo Harbor, eastern China: seasonal variation, source apportionment, and cancer risk assessment

Field measurements were conducted at a container harbor located in Ningbo-Zhoushan Port, China. Concentrations of fifty-three PAHs in airborne PM2.5 were quantified using gas chromatography-mass spectrometry (GC-MS). The positive matrix factorization model and potential source contribution function analysis were used to evaluate the main sources of PAHs. The PM2.5-bound PAH-associated inhalation lung cancer risks were estimated using a point estimate approach based on relative potency factors. Average concentrations were recorded for PM2.5 (18 +/- 6.0 mu g/m(3)) and n-ary sumation (53)PAHs (8.83 +/- 8.42 ng/m(3)). The 4-6 ring PAHs accounted for approximately 85% of the total PAH concentrations, with the majority of these compounds being deemed carcinogenic. Five sources and mass contributions were determined by the positive matrix factorization (PMF) model: gasoline and diesel exhaust emissions (24.8%); volatilization or spill of petroleum and petroleum-related products (22.3%); heavy fuel oil combustion (18.2%); the mixed combustion emissions composed of coal and biomass combustion (18.1%); and natural gas combustion (16.7%). The potential source contribution function analysis suggested that PAHs in the harbor were greatly affected by long-distance input, especially from the North China Plain and the Yellow Sea. The calculated incremental lifetime lung cancer risk of PAH exposure was 8.07 and 702 cases per million people using the inhalation unit risk of exposure to the BaP value recommended by the California Environmental Protection Agency and the World Health Organization, respectively. Gasoline and diesel exhaust emissions (52.1%) have contributed more to the lung cancer risk. From a health risk standpoint, this measure could help to identify relevant sources of controls in port regions.