Occurrence, source modeling, influencing factors and exposure assessment of polycyclic aromatic hydrocarbons in water sources: A mega-study from mainland China

This study investigates the composition and distribution of 16 priority polycyclic aromatic hydrocarbons (PAHs) in 70 water samples collected from centralized drinking water sources (CDWSs) across 30 provinces (cities) in mainland China. Additionally, water quality and socio-economic data were collected to determine the influencing factors. The study discovered that the total concentrations of 16 priority PAHs (Sigma(16)PAHs) varied from 0.17 to 176.71 ng/L (mean: 56.49 +/- 38.58 ng/L). Lakes and reservoirs had significantly higher concentrations of PAHs than groundwater. The primary pollutants were low-molecular-weight (LMW) PAHs, such as phenanthrene, naphthalene, and fluorene. There was a strong correlation between LMW PAHs and Sigma(16)PAHs (p < 0.05). The mean Sigma(16)PAHs in the seven geo-environmental zones were ranked as follows, under the comprehensive influence of emission density, natural, and social environmental factors: Northwest China (78.42 +/- 66.96 ng/L) > Northeast China (73.70 +/- 33.23 ng/L) > East China (64.35 +/- 45.66 ng/L) > North China (50.95 +/- 31.87 ng/L) > Southwest China (44.05 +/- 32.56 ng/L) > Central China (41.68 +/- 19.44 ng/L) > Southern China (40.99 +/- 16.54 ng/L). The source modeling analysis revealed that the majority of PAHs came from chemical production and metal smelting (42.36%), as well as from the combustion of coal, wood, and biomass (34.17%), and other mixed sources. In addition, the study found a strong correlation between water quality and socio-economic factors with concentrations of PAHs, indicating that these factors may contribute to the re-enrichment, transport, and transformation of PAHs in overlying water to varying degrees. The mean incremental lifetime cancer risk (ILCR) was lower than the risk threshold. These findings provide scientific references for managing hazardous substances in the aquatic environment.