Distribution and migration of polycyclic aromatic hydrocarbons in sediment and water of the Three Gorges Reservoir

Abstract

AbstractSediment and water samples were collected from Xiangxi Bay in the Three Gorges Reservoir area of China to study the spatial distribution, migration, and ecological risks of 16 priority polycyclic aromatic hydrocarbons (PAHs) across four periods associated with different water levels from June 2017 to March 2018. Results showed that PAH contents ranged from 178.61 to 250.20 ng L−1 in water and from 5.26 to 1,325.25 ng g−1 in sediments, leading to a classification of moderate pollution in Xiangxi Bay relative to that in other estuarine systems. Polycyclic aromatic hydrocarbon levels varied across the four stages, with the proportion of two‐, three‐, and four‐ringed PAHs increasing in water and five‐ and six‐ringed PAHs decreasing in sediment across these periods. Pearson correlation analysis showed that the amount of five‐ and six‐ringed PAHs in water was significantly and positively correlated with the amount of suspended solids (p < .05) and that three‐ringed PAHs in sediments were significantly and positively correlated with the amount of soil organic matter (p < .05). Based on fugacity fraction estimation, two‐ringed PAHs mainly diffused from sediment to water, whereas five‐ and six‐ringed PAHs mostly migrated from water to sediment across stages. Ecological risk assessment revealed that PAHs present a moderate ecological risk in Xiangxi Bay overall, with low ecological risk in the second and fourth water level stages and moderate ecological risk in the first and third stages in sediment.