Study On Vertical Concentration Distribution And Exchange Process Of Water-sediment In Chaohu PAHs

With the rapid development of the social economy and the accelerating urbanization and industrialization,the problem of environmental pollution has become increasingly prominent,and water pollution has gradually received attention.Persistent organic pollutants Polycyclic aromatic hydrocarbons have received increasing attention due to their trigenic"teratogenic,carcinogenic,mutagenic"effects and their widespread presence in environmental media.In this study,we used our in-situ passive sampling device,using LDPE membrane as the adsorption phase,and using the calibration method of performance reference compounds（PRCs）to simultaneously determine the free dissolved concentration of PAHs in the upper water and sediment pore water at different depths.We chose two typical rivers in Chaohu Lake（NanFei River,GuiShang）as research areas.Based on this,we investigate the vertical concentration distribution characteristics and interfacial diffusion flux of PAHs in the upper water bodies and sediment pore waters of the Chaohu Lake region.We further demonstrate whether the PAHs accumulated in the sediments at the bottom of Chaohu Lake are secondary sources of PAHs in the upper waters,and invert the historical pollution process to clarify the environmental fate of the pollutants.In this paper.we use the characteristic ratio method to analyze the source of polycyclic aromatic hydrocarbons in Chaohu Lake,and use the risk coefficient quotient method（RQ）to characterize the pollution risk of polycyclic aromatic hydrocarbons on Chaohu Lake.At the same time,we assessed the ecological risk of PAHs in Chaohu Lake.The main conclusions are as follows:（1）The concentration of polycyclic aromatic hydrocarbons in the upper waters of Chaohu Lake is not much different,and the concentration is 102¹82 ng L^-1.There is a significant difference in the concentration of the“west high and low east”spatial region in the sediment pore water.The sedimentary water in the sediment of the Nanfei River is∑₁₆6 252⁴98 ng L^-1,and the pore water in the sediment of the Guishan area is∑₁₆175³40 ng L^-1.This reflects the difference in polycyclic aromatic hydrocarbon concentrations in the sediment.The concentration of polycyclic aromatic hydrocarbons in the sediments at the bottom of the Nantun River is relatively high.（2）The vertical concentration distribution of polycyclic aromatic hydrocarbons in the water of Chaohu Lake will have bimodal characteristics,mainly due to the dual effects of atmospheric deposition and water-sediment interface diffusion.The vertical concentration distribution of sediment pore water reflects the sedimentation of the bottom layer.The influence of historical sediments.（3）Through the flux model to calculate the flux of the Nanhu River into the lake mouth and the Guishan area,the sediment-water exchange of polycyclic aromatic hydrocarbons in the summer and autumn of the East and West Lakes of Chaohu Lake is from the bottom sediment to the upper water body.Transmission,that is to say,part of the PAHs in the waters of Chaohu Lake at this stage is secondary pollution from the sediments at the bottom of Chaohu Lake.（4）Most of the PAHs in the waters of Chaohu Lake come from the combustion source,including the combustion of biomass and coal.The probability of the turtle mountain area is highly polluted by petroleum.（5）The PAHs in the Chaohu Lake are at low ecological risk,but the ecological risk of the Weihe Lake in the western part of Chaohu Lake is significantly higher than that in the Chaoshan Lake.