Abstract: The concentrations of 16 EPA-priority polycyclic aromatic hydrocarbons (PAHs) in surface sediments of Baiyangdian Lake were detected using Gas Chromatography-Mass Spectrometry (GC-MS) method. The components, spatial distribution, pollution sources, and ecological risk of the 16 EPA-priority PAHs were analyzed using statistical analysis integrated with isomer ratio analysis, inverse distance weighted interpolation, and ecological risk evaluation. The results showed that total concentrations of PAHs in surface sediments of Baiyangdian Lake ranged from 1.79 to 1618.90 ng·g^-1, with an average value of 411.12 ng·g^-1. The composition of PAHs was dominated by four and five rings, which accounted for 42.22% and 28.21% of the total concentration, respectively. With respect to monomer concentration, benzo\[b\]fluoranthene (16.47%) was the highest and acenaphthene was the lowest (0.26%), indicating that PAHs were mainly imported from local sources rather than transported by air masses. Spatially, the concentration of PAHs was higher in the central areas of the lake and lower in the surrounding areas. Pollution was especially heavy in the northwest and south of the lake center. The sampling sites with the highest concentrations of PAHs were Anxin Bridge, Shaochedian and Caiputai, followed by Zhainan and Duancun. The results of pollution source analysis showed that PAHs in the surface sediments mainly came from the combustion of biomass, coal, and oil. Results of the risk assessment showed that the concentration of one-third of the sampling sites exceeded the effects range-low, which indicated that PAHs might have ecological hazards to Baiyangdian Lake. The comparison of the detection data in 2007, 2008, 2009 and 2016 showed that the average concentration of PAHs dropped, which might be related to the decrease of population density in the lake area and the use of electricity instead of coal.

Key words: PAHs, surface sediment, source identification, spatial distribution, ecological risk assessment.