Distribution Characteristics,risk Assessment And Adsorption Of Polycyclic Aromatic Hydrocarbons By Biochar In Chaohu Lake Basin

In Chaohu lake and 9 major rivers surrounding the discrepancy in hukou as the study area,collects the surface water of Chaohu lake basin 33 points and the surface sediment samples,using gas chromatography-mass spectrometry instrument of polycyclic aromatic hydrocarbons in the sample test Polycyclic Aromatic Hydrocarbons concentration,The concentration,spatial and composition distribution characteristics of PAHs in surface water,suspended particulate matter and surface sediment of Chaohu Lake were analyzed.The main sources of PAHs in surface water,suspended particulate matter and surface sediment of Chaohu Lake were analyzed by the feature ratio method and principal component analysis method.The risk entropy method was used to evaluate the ecological risks caused by PAHs in surface water,suspended particulate matter and surface sediments of Chaohu Lake.Finally,the adsorption kinetics and isotherm experiments were carried out on the typical PAHs monomer-Phenanthophylla by corn straw biochar to explore the adsorption performance of phenanthophylla by the biochar.The main research conclusions of this paper are as follows:（1）The concentration of∑₁₆PAHs in the surface water of Chaohu Lake Basin ranges from 32.6-224.3 ng·L^-1,and the average concentration is 139.6 ng·L^-1,which is at a medium low level in lakes and rivers at home and abroad.The relationship of PAHs concentration in surface water of Chaohu Lake was West Lake>Middle Lake>East Lake.The concentration of PAHs in surface water of main surrounding rivers was the highest in Nanfei River and the lowest in Yuxi River,and the concentration of PAHs in its tributary was higher than that in surface water of Chaohu Lake.Phe accounted for the highest proportion of all sampling sites,while DBA was the lowest.The relationship between PAHs of different ring numbers in surface water of Chaohu Lake Basin is 2-3ring PAHs>4 ring PAHs>5-6 ring PAHs.The pollution of PAHs in surface water of Chaohu Lake Basin is mainly affected by the high temperature combustion of biomass and coal and the pyrolysis sources.In the surface water of Chaohu Lake Basin,the ecological risk of Ba A is high risk,and the other 15 PAHs are medium risk.The sampling points S9,S12-S24,T4 and T7-T9 of∑₁₆PAHs are low risk,and the other 15sampling points are medium risk.（2）The concentration of∑₁₆PAHs in suspended particulate matter in Chaohu Lake Basin ranges from 146.8-1117.5 ng·g^-1,and the average concentration is 655.0 ng·g^-1,which is at the medium pollution level in lakes and rivers at home and abroad.The relationship of PAHs concentration in suspended particulate matter in Chaohu Lake was West Lake>Middle Lake>East Lake.The concentration of PAHs in suspended particulate matter in main surrounding rivers was the highest in Nanfei River and the lowest in Yuxi River,and the concentration of PAHs in tributaries was higher than that in Lake.Phe was the highest and In P was the lowest in all sampling sites.The relationship of PAHs with different ring numbers in suspended particulate matter in Chaohu Lake Basin is 2-3 ring PAHs>4 ring PAHs>5-6 ring PAHs.Compared with the composition characteristics of PAHs in surface water,the proportion of 2-3 ring low ring PAHs decreases,while the proportion of 4 ring PAHs and 5-6 ring high ring PAHs increases.The sources of PAHs pollution in suspended particulate matter in Chaohu Lake Basin are mainly affected by high temperature combustion of biomass and coal and pyrolysis sources.In the suspended particulate matter of Chaohu Lake Basin,only Ba A and Bb F are high risk,and the other 14 PAHs are medium risk.The S19-S24 and T8-T9 sampling points of∑₁₆PAHs are medium risk,and the other 25 sampling points are high risk.（3）The concentration of∑₁₆PAHs in the surface sediments of Chaohu Lake Basin ranges from 708.0-2041.7 ng·g^-1,and the average concentration is 1459.9 ng·g^-1,which is at the medium pollution level in lakes and rivers at home and abroad.The relationship of PAHs concentration in surface sediments of Chaohu Lake was West Lake>Middle Lake>East Lake.The concentration of PAHs in surface sediments of main surrounding rivers was the highest in Nanfei River and the lowest in Yuxi River,and the concentration of PAHs in its tributaries was higher than that in surface sediments of Chaohu Lake.DBA accounted for the highest proportion of all sampling sites,and Flu was the lowest.The relationship of PAHs in surface sediments of Chaohu Lake Basin with different cyclic numbers was 5-6 cyclic PAHs>2-3 cyclic PAHs>4 cyclic PAHs,and the relationship of PAHs concentration in different environmental media was surface sediment>suspended particulate matter>surface water.The sources of PAHs pollution in the surface sediments of Chaohu Lake Basin are mainly affected by the combined factors of petroleum combustion,high temperature combustion of biomass and coal,and pyrolysis sources.In the surface sediments of Chaohu Lake Basin,only the ecological risk of Chr is low risk,the ecological risk of the other 15 PAHs is medium risk,the sampling points of S1,T1 and T5 of∑₁₆PAHs are medium risk,and the other30 sampling points are low risk.（4）The adsorption kinetics of corn straw biochar for phenanthrene solution is mainly controlled by the fast adsorption stage.The quasi-second-order kinetic model is the best fit,which also indicates that the adsorption process is mainly achieved by chemisorption.Both Langmuir and Freundlich adsorption isotherm models can fit the isotherm process well,but the Langmuir adsorption isotherm model has a higher degree of fitting.The saturated adsorption capacity of corn straw biochar for phenanthene reached 1186.67μg·g^-1,and the adsorption process showed nonlinear adsorption and favorable adsorption.