Distribution, source identification, and ecological risk of PAHs in a large river- reservoir system

Abstract

Rivers and their reservoirs form a connected river-reservoir system that plays an important role in regulating the water environment. However, the distribution and potential environmental behaviour of polycyclic aromatic hydrocarbons (PAHs) in the river-reservoir system are scarce. This study focused on the occurrence, distribution and risk assessment of PAHs in a river-reservoir system based in the Dongjiang river source area. 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, with the main monomer being naphthalene (Nap). The main pollution source was dominated by a mixture of charcoal, coal and gasoline combustion. The proportion of gasoline and diesel combustion in the reservoir system was higher than the river system. In contrast, the occurrence level of Σ16PAHs in the reservoir system was relatively higher than the river. On the time scale, the levels of Nap were greatly enhanced in the spring, which might be correlated with its abundant input of stormwater runoff. The composition of the PAHs remained stable during the transition from river to reservoir, suggesting their durability and stability in the aquatic environment. Redundancy analysis indicated that temperature, NO3-, and NH4+ could impact the PAHs content. In general, the environmental risk of PAHs in the aqueous phase was at moderate risk and low health risk, with no effect on the safety of drinking water.