Study On The Sedimentary Records Of Polycyclic Aromatic Hydrocarbons And Their Influencing Factors In Typical Chinese Lakes

Polycyclic aromatic hydrocarbons are persistent toxic pollutants.Due to their carcingenic,teratogenic and mutagenic effects,they have been listed as the priority pollutants by the US Environmental Protection Agency.China is the country with the largest amount of PAHs in the world.PAHs pollution has become one of the most prominent environmental issues in China and has received extensive attention.Due to the lipophilic hydrophobicity of PAHs,they are easily endowed with lake sediments rich in organic matter.Therefore,lake sediments,as the source and sink of PAHs,are an ideal place for researching PAHs.In this study,four typical lakes of Fuxian Lake,Bosten Lake,Taihu Lake and Chaohu Lake were selected and the sediment cores were collected as the research objects.The content of PAHs in sedimentary cores was determined by gas chromatography-mass spectrometry.The potassium dichromate oil bath method was used to test the content of organic matter.The Determination of total nitrogen was adopted by alkaline potassium persulfate digestion.The total phosphorus content was investigated by molybdenum perchlorate digestion—molybdenum antimony colorimetric method.By doing these,we can analyze the sedimentary records of PAHs content in sediments from four lakes and the vertical characteristics of nutrient levels.By reviewing the statistical yearbooks of the cities in the four lake basins,the total GDP,total population,crop yields,coal consumption,and oil consumption in the four lake basins were sorted out,and emission factors method was used to estimate the content of PAHs discharge about human activities in historical periods.In turn,the factors influencing the records of PAHs in different lakes were analyzed from three aspects:socio-economic parameters,PAHs content emitted by human activities during historical periods,and trophic level.The main findings are as follows:(1)According to the average sedimentary rates of the four lakes,the approximate age of deposition have been determined.Through the PAHs content determination of core in four lakes,the history of PAHs pollution in four lakes over the past 100 years has been reconstructed.The content of 16 PAHs in Fuxian Lake was in the range of 219.80～1730.58 ng·g-1,and the content of 16 PAHs in Taihu Lake was in the range of 93.53 to 1228.95 ng·g-1.Both of them were in the medium level;the range of 16 PAHs in Bosten Lake was changed from 132.84 to 325.75 ng·g-1,the range of 16 PAHs content in Chaohu Lake was from 130.03 to 387.75 ng·g-1,both of which were at low levels.The vertical variation trends of polycyclic aromatic hydrocarbons in four Lakes vary,and changes in the pollution history reflect the continuous changes in the socio-economic development of the lake basin.The contents of organic matter in sediments from different lakes are ranked from high to low:Bosten Lake>Fuxian Lake>Taihu Lake>Chaohu Lake;total nitrogen contents are sorted from high to low:Fuxian Lake>Bosten Lake>Chaohu Lake>Taihu Lake;total phosphorus contents are arranged from high to low:Fuxian Lake>Bosten Lake>Taihu Lake>Chaohu Lake.(2)The correlation analysis of 16 PAHs content in Fuxian Lake,Bosten Lake,Taihu Lake,and Chaohu Lake with social and economic parameters,PAHs emissions from human activities in historical periods,and nutrition levels were conducted.The results showed that:the PAHs content of four lakes has a significant positive correlation with the total population of the river basin,total GDP,total coal consumption,PAHs emissions from human activities in historical periods,total nitrogen content,and total phosphorus content,indicating that the content of PAHs in lakes was affected by the total population,total GDP,total coal consumption,PAHs emissions from human activities in historical periods,total nitrogen content,and total phosphorus content.In addition,the increase of oil consumption in Fuxian Lake and Taihu Lake Basin will increase the content of PAHs in sediments of the two lakes.Due to the physical adsorption of PAHs by the organic matter,the organic matter content of Fuxian Lake,Bosten Lake and Taihu Lake will affect PAHs in the lake sediments.