Distribution, Source Identification, and Risk Assessment of Polycyclic Aromatic Hydrocarbons in a Large Drinking Water River-Reservoir System

Rivers and downstream reservoirs formed a connected river-reservoir system that played an important role in regulating the aquatic environment. The polycyclic aromatic hydrocarbon (PAH) pollution in individual river or reservoir has caused widespread concern. However, the distribution and potential environmental behaviour of PAHs in the river-reservoir system are still scarce. This study focused on the occurrence, distribution, and risk assessment of PAHs in a representative river-reservoir system in South China. The concentration of Σ₁₆PAHs in the water phase of the river-reservoir system was 102.2 − 407.6 ng/L and at a low level compared to other typical aquatic environment, with the main monomer being naphthalene. The PAHs in the river system were mainly from the volatilization of petroleum products, while they were from combustion and petroleum volatilization sources in the reservoir system. For the river system, higher runoff and temperature could contribute to the volatilization of low molecular weight PAHs and their solubility in the water phase. In contrast, longer hydraulic retention time in the reservoir system could reduce the occurrence level of 3-ring PAHs through the biogeochemical cycles. Redundancy analysis further indicated that significant factors affecting PAHs in river system and reservoir system were different. In common, the water temperature could influence the PAHs both in the river system and reservoir system. Generally, the ecological risk of PAHs in the water phase was at a moderate risk and their health risk was at a low risk.