Status, source and health risk assessment of polycyclic aromatic hydrocarbons (PAHs) in soil from the water-level-fluctuation zone of the Three Gorges Reservoir, China

• PAHs in the water-level-fluctuation zone (WLFZ) of the Three Gorges Reservoir.
• The concentration and distribution of PAHs in one cycle of water fluctuation.
• The correlations among MBC and PAHs.

The paper discussed the distributions, sources and health risk of polycyclic aromatic hydrocarbons (PAHs) in the water-level-fluctuation zone (WLFZ) of the Three Gorges Reservoir (TGR), China, in where the rapid transfer of pollutants between the water and terrene environment cased by the cycle of water fluctuation is of great concern. Twenty-four soil samples were collected in two sampling campaigns, i.e., in September 2012 (the water levels started rising from 145 m) and in June 2013 (the water levels just fell to 145 m), and subsequently they were analyzed for 16 USEPA priority PAHs. Total PAH concentrations (Σ16PAHs) ranged from 18.40 to 392.29 ng·g− 1 (mean 87.66 ng·g− 1) in 2012, and 54.00 to 463.08 ng·g− 1 (mean 133.84 ng·g− 1) in 2013. The concentrations of ΣPAHs in soil sample in 2013 were significantly higher than those in 2012. The concentrations of ΣPAHs in the upstream counties (Banan, Changshou, Fuling and Fengdu) were significantly higher than that in the middle and the lower reaches counties (Zhongxian, Wanzhou, Yunyang, Fengjie, Wushan, Badong, Guizhou and Lanlingxi). The compounds of 3-rings and 4-rings were the major components of PAHs in this area. Individual PAH concentrations were not significantly correlated with total organic carbon (TOC) and microbial biomass carbon (MBC), possibly due to the soil microbial mineralized or degraded PAHs and the semi-continuous inputs from anthropogenesis sources. Source identification indicated that PAHs were mainly derived from river transport and combustion. The incremental lifetime cancer risks ranged from 10− 9 to 10− 6, indicated that the carcinogenic risk for the residents was negligible.