Distribution of 16 Polycyclic Aromatic Hydrocarbons in Dianchi Lake Surface Sediments After the Integrated Water Environment Control Project

: The external pollution of Dianchi Lake has been effectively controlled with the implementation of the integrated water environment control project. However, further attention should be paid to endogenous pollutants, such as surface sediments. To investigate the distribution of 16 polycyclic aromatic hydrocarbons (PAHs) in surface sediments of Dianchi Lake, PAH concentrations in 19 surface sediment samples (collected in December 2016) were quantitatively measured by gas chromatography-mass spectrometry (GC-MS). The spatial and temporal distribution, sources, and ecological risks were also analyzed. The concentration of total PAHs (TPAHs) in the Dianchi Lake surface sediments varied in the range of 92.31-1546.78 ng·g-1 with an average of 496.30 ng·g-1. The average concentration of TPAHs in the surface sediments from Caohai (932.37 ng·g-1) was much greater than that from Waihai (380.02 ng·g-1). With the implement of the integrated water environment control project, the concentration of TPAHs in the surface sediments from Dianchi Lake was significantly lower than those detected in 2012, and was already relatively low level among other key waterbodies in China. The PAH with the highest concentration was fluoranthene (80.65 ng·g-1) and the substance with the highest toxic equivalent quantity (TEQ) was dibenz[a, h] anthracene (42.97 ng·g-1). The PAHs were mainly composed of 4 ring and 5-6 ring compounds (with the concentration ratio of 40.38% and 40.22%, respectively), which indicated that the proportions of middle-ring and high-ring compounds were generally consistent. The results of the molecular diagnostic ratio analysis showed that the primary source of PAHs in Dianchi Lake surface sediments are biomass and coal combustion. Based on the potential ecological risk marker comparison method, the entire lake was classified as having a low ecological risk, while the ecological risk of Caohai was relatively higher, which should be concerned further. The results provide initial data and act as an important reference for the conservation and improvement of water quality in Dianchi Lake.