Background PM_2.5 pollution has become a widely concerned environmental health problem. Polycyclic aromatic hydrocarbons(PAHs) are the main harmful components of PM_2.5, and their sources and carcinogenic risk deserve attention.

Objective To analyze the source apportionment of PAHs in ambient PM_2.5 in Fuzhou, and to evaluate the potential carcinogenic risk through inhalation due to exposure to PAHs.

Methods In this study, two sampling sites were set up in Cangshan (industrial area) and Taijiang (commercial and residential area) districts in Fuzhou City. PM_2.5 was collected from 10th to 16th of each month from 2017 to 2020 by membrane filtration method. The concentrations of ambient PM_2.5 were measured by weighing, and the concentrations of 16 PAHs, including naphthalene(NAP), acenaphthylene(ACY), acenaphthene(ACE), fluorene(FLU), phenanthrene(PHE), anthracene(ANT), fluoranthene(FLT), pyrene(PYR), benzoaanthracene(BaA), chrysene(CHR), benzobfluoranthene(BbF), benzokfluoranthene(BkF), benzoapyrene(BaP), indeno1,2,3-cdpyrene(IcdP), dibenzoa,hanthracene(DahA), and benzog,h,iperylene(BghiP), were determined by ultra-high performance liquid chromatography coupled with diode array detector and fluorescence detector. The concentrations of PM_2.5 and PAHs were compared in the two districts and the concentrations of PAHs were also compared in different seasons. The diagnostic ratio FLT/(FLT+PYR), IcdP/(IcdP+BghiP), BaA/(BaA+CHR), and BaP/BghiP method and positive matrix factorization (PMF) analysis were used to determine the sources of PAHs in PM_2.5 in Fuzhou. The excess carcinogenic risk (ECR) model was used to assess the potential health risk of inhalation exposure to PAHs.

Results During 2017–2020, the M (P₂₅, P₇₅) concentration of ambient PM_2.5 in Cangshan and Taijiang districts of Fuzhou were 35.0 (25.0, 47.5) and 34.0 (25.5, 46.0) μg·m⁻³ respectively, and the percentages of PM_2.5 exceeding the national standard in Cangshan and Taijiang were 2.68% and 4.17%, respectively, without significant differences (P＞0.05). The M (P₂₅, P₇₅) concentrations of ΣPAHs in Cangshan was 5.03 (3.07, 7.67) ng·m⁻³, higher than that in Taijiang, 3.20 (2.05, 5.59) ng·m⁻³ (P＜0.05). The M (P₂₅, P₇₅) concentrations of PAHs monomers except ACY, FLU, and ACE in Cangshan were higher than those in Taijiang (P＜0.05). The concentrations of ΣPAHs in PM_2.5 in four seasons in Cangshan were higher than those in Taijiang (P＜0.05). In both districts, the concentration of ΣPAHs in winter was higher than those in spring, summer, and autumn (P＜0.05). According to the diagnostic ratio method, the median ratios of FLT/(FLT+PYR) in the two districts ranged from 0.4 to 0.5, and those of IcdP/(IcdP+BghiP), BaA/(BaA+CHR), and BaP/BghiP were from 0.2 to 0.5, from 0.2 to 0.35, and less than 0.6, respectively. The results of PMF analysis showed the proportions of four factors in Cangshan were 37.9%, 13.2%, 24.0%, and 24.9%, respectively. The major load contributors to factor 1 included FLT, PHE, and PYR; to factor 2, FLU, ACY, and ACE; to factor 3, DahA; to factor 4, BghiP, IcdP, and BaP. The proportions of four factors in Taijiang were 23.6%, 19.3%, 22.0%, and 35.1%, respectively. The main load contributor to factor 1 was DahA; to factor 2, BghiP; to factor 3, FLT, PHE, and PYR; to factor 4, IcdP, BaP, BbF, BkF, CHR, and BaA. The benzoapyrene equivalences (BEQ) in Cangshan and Taijiang districts were 1.87 ng·m⁻³ and 1.61 ng·m⁻³, respectively. The excess carcinogenic risks of PAHs through inhalation exposure was 3.83×10⁻⁶ and 3.30×10⁻⁶, respectively.

Conclusion The complex sources of PAHs in ambient PM_2.5 include dust, vehicle emissions, industrial emissions in Fuzhou, and are different in selected two districts. The level of PAHs in ambient PM_2.5 may pose a potential carcinogenic risk to local population.