Huixian wetland stands as one of the largest karst wetland systems in China, exhibiting both karst and wetland characteristics, thereby playing a pivotal role in ecological buffering within the Guilin region.Due to the toxicity and ubiquity of PAHs in aquatic system, understanding the distribution, flux, sources and risk assessment is much crucial to for the sustainable development of the reserve. To explore the PAHs pollution of the area, 29 water and surface sediment samples in low-flow period, 33 water and 29 surface sediment in high-flow period were collected from Huixian wetland in Guilin. The results revealed that the water in the study area exhibited a low level of pollution, whereas the concentration of pollutants in the surface sediment was significantly higher compared to other wetlands. Both diagnostic ratios and the Positive Matrix Factorization (PMF) model indicated that biomass burning and traffic emissions are potentially the primary sources of PAHs. A fugacity analysis of water and sediment revealed that sediment serves as a sink for PAHs, particularly for the High Molecular Weight (HMW) PAHs. Furthermore, the sediments also act as secondary sources of PAHs, capable of releasing them back into the water. Species sensitivity distribution analysis indicated that Phe and Fla should be closely monitored, as the concentrations of most sites exceeded the value of the Hazardous Concentration for 5% of species (HC₅). Overall, the ecological risks within the study area generally were low-moderate, with certain individual sites, such as SD1-1 and SD2-1, exhibited high levels of contamination, thus necessitating closer attention and monitoring.
 

Polycyclic aromatic hydrocarbons,Water-sediment exchange,Risk assessment,Huixian Wetland