Distribution and migration of polycyclic aromatic hydrocarbons in sediment and water of the three gorges reservoir across various water level stages and assessment of their ecological risks

Sediment and water samples were collected from Xiangxi Bay in the Three Gorges Reservoir area of China to study the spatial distribution, migration, and potential health 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 5.26 to 1325.25 ng g−1 in sediments, leading to a classification of moderate pollution in Xiangxi Bay relative to that in other estuarine systems. PAH levels varied across the four stages, with the proportion of 2–4 ringed PAHs increasing in water and 5–6 ringed PAHs decreasing in sediment across these periods. Pearson correlation analysis showed that the amount of 5- and 6-ringed PAHs in water significantly and positively correlated with the amount of suspended solids (p < 0.05) and 3-ringed PAHs in sediments were significantly and positively correlated with the amount of soil organic matter (p < 0.05). Based on fugacity fraction estimation, 2-ringed PAHs mainly diffused from sediment to water, whereas 5- and 6-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. This article is protected by copyright. All rights reserved