Distribution, Source Identification And Ecological Risk Assessment Of Polycyclic Aromatic Hydrocarbons In Surface Sediments Of The Lake From The Cold And Arid Reagions

Polycyclic aromatic hydrocarbons (PAHs) are typical persistent organic pollutants. PAHs are difficult to degrade in the environment and it can get into the water through the ways of the surface runoff, atmospheric precipitation, farmland water and so on. Since PAHs have strong adsorption and hydrophobic, making it easier to accumulate in sediments. PAHs can be biological accumulated and biological amplificated through the food chain, and then can easily flow into the organisms, even a serious threat to human health, eventually leading to a potential threat to the decay and degradation of lake ecosystems. Therefore, the study on PAHs have profound meaning, so as to provide reliable basis to control pollution for Wuliangsuhai Lake and Dalinuoer Lake. At the same time, the results of the study can also provide a scientific reference for the reasonable water pollution control programs and regional environmental planning for the relevant environmental protection departments.This paper focus on the distribution of PAHs in the Wuliangsuhai Lake and Dalinuoer Lake, analyzing the content distribution, composition characteristics, sources and ecological risk of the PAHs in the study area. We can draw the following conclusions:(1) The contents of the sixteen PAHs of the surface sediments in the Wuliangsuhai Lake were among 129.086-2162.287ng/g, and the average contents was 405.45ng/g. Wherein the percentage of high molecular weight PAHs (4～6 rings)is up to 71.21%, which is the dominated monomers, and the percentage of low molecular weight PAHs (2 rings and 3 rings) is at a lower level, the proportion was 28.79%.The contents of the sixteen PAHs of the surface sediments in the Dalinuoer Lake were among 100.397-～1035.756ng/g, and the average contents was 479.57ng/g. Wherein the percentage of high molecular weight PAHs (4～6 rings) is up to 58.94%, which is the dominated monomers, and the percentage of low molecular weight PAHs (2 rings and 3 rings) is at a lower level, the proportion was 41.06%.(2)The results showed that there was no correlation between PAHs and TOC in the sediments from Wuliangsuhai Lake and there was significant correlation between PAHs and TOC in the sediments Dalinuoer Lake. The reason may also be the lower content of the surface sediment of the study area.(3) There was no significant correlation between PAHs content and the silt composition and sand composition in the sediments from Wuliangsuhai Lake, and there was significant correlation between PAHs content and the clay composition.And for the PAHs content in the sediments from Dalinuoer Lake, And there is significant correlation between silt composition and the degree of the enrichment of PAHs, there is significant correlation between clay composition and the degrere of the enrichment of PAHs and there is Significant negative correlation between sand composition and the degree of the enrichment of PAHs.(4) According to the isomer ratio method of the different PAHs and the ratio method of low molecular weight PAHs and high molecular weight PAHs, the PAHs in surface sediment from the Wuliangsuhai Lake originated largely from combustion source and a small amount of oil spill and the PAHs in surface sediment from the Dalinuoer Lake originated largely from combustion source and oil spill.(5) The sediment had a low probability of ecological risk in the two lakes.On the basis of ecological risk evaluation of the PAHs in the surface sediments of Wuliangsuhai Lake and Dalinuoer Lake, the content of PAHs in sediments is certain ecological risks.According to SQC (Sediment quality criteria), the Acy and Ace in surface sedeiments from Wuliangsuhai Lake exceeded the ERL value in the most of the sediment sampling points, especially BghiP and InP were detected in all sampling points. The Ace in surface sedeiments from Dalinuoer Lake exceeded the ERL value in the most of the sediment sampling points, especially BghiP and InP were detected in all sampling points.The potential ecological risks of PAHs were evaluated on the basis of SQG(Sediment quality guidelines).The results showed that the Acy, Ace, DbA and Naph in surface sediments all exceeded the ERL value in the Wuliangsuhai Lake and Dalinuoer Lake. Especially the content of Chry exceeded the REL value.The results showed that both two lakes has certain ecological risk, risk mainly comes from acenaphthene and acenaphthylene.