Sources and ecological risk of polycyclic aromatic hydrocarbons in water and air of the Yangtze River

Identifying the accurate sources of polycyclic aromatic hydrocarbons (PAHs) in water is crucial for protecting the aquatic eco-health of the Yangtze River. In this study, we investigated 16 types of PAHs in the air and water along the Yangtze River, spanning from Chongqing to Shanghai. Similar spatial distribution pattern of total PAH concentrations that higher levels in the west and lower levels in the east were found between water and air. This distribution may be influenced by factors such as water temperature, energy transformation, and the input of exogenous air masses. Further analysis using diagnostic ratios, the principal component analysis coupled with absolute principal component score (PCA-APCS) model, and air-water exchange fugacity fractions allowed us to apportion the sources of PAHs in the water and air. Interestingly, we found that the sources of PAHs in the water and air were completely different, with ship-transportation contributing to PAHs in the water and biomass combustion contributing to PAHs in the air. To assess the ecological risk to freshwater biodiversity, we employed species sensitivity distribution (SSD) and found that PAHs in the water of the Yangtze River are likely to exert chronic long-term effects on more than 5% of aquatic organisms, which may lead to changes in the ecosystem stability. Although acute lethal effects were insignificant with an msPAF_Total value below 5%, it is important to monitor their changes, especially in the upper and middle regions of the Yangtze River. In conclusion, our study highlights that the burden of PAHs in the water of the Yangtze River, primarily caused by shipping activities, has significant adverse effects on the aquatic ecosystem. Therefore, it is necessary to implement further control measures for ship-transportation to mitigate these impacts of PAHs in the Yangtze River.