Pollution Characteristics,Potential Sources And Risk Assessment Of Polycyclic Aromatic Hydrocarbons In Surface Sediments And Surrounding Soils Of Lakes And Surrounding Soils Of Lakes And Rivers In The Qinghai-Tibet Plateau

The Qinghai-Tibet Plateau is located in western China,in the central part of the Eurasian continent.It is the highest altitude plateau in the world and is less affected by human activities.It is also an important source of water in China.Under natural conditions,the content of PAHs(polycyclic aromatic hydrocarbons)in the Qinghai-Tibet Plateau is relatively low.With the changes of climate,social and economic factors,the ecological environment is affected,and the PAHs in the environment are gradually increasing.Sediment is one of the most important storage media for PAHs in the environment.The enrichment of PAHs in sediments poses a great potential risk to local ecosystems and human health.The major results are as follows:(1)Sixteen PAHs were detected in total 106 samples.The total PAHs(?16PAHs)in the lakes and river sediments of the Qinghai-Tibet Plateau were:38.1?743.8?g·kg-1.The content of?16PAHs in Lake of DQC,XRC,DJC,KLK and AR is higher than 300 ?g·kg-1;the lowest content of ?16PAHs in SLC Lake is 38.1 ?g·kg-1.The total amount of ?16PAHs in river sediments were 107.7?743.8?g·kg-1,with an average of 218.1 ?g·kg-1.The highest value of?16PAHs appears at the river sediment sampling point of BMCZL-SQ.The ?16PAHs in the 46 soil samples ranged from 95.0 to 1173.0 ?g·kg-1,with a mean value of 240.3 ?g·kg-1.The PAHs in the sediments and surrounding soils of the Qinghai-Tibet Plateau are seperatly dominated by 3?5 rings,3?4rings,followed by 2 rings,and low percentage of high-rings PAHs.The proportion of PAHs with different ring numbers are:3 rings>4 rings>2 rings>5 rings>6rings.(2)Distribution characteristics of PAHs in the study area:the PAHs of sampling points near towns and roads are relatively high;for example,nine natural villages are distributed within the 1000m range of BMCZL-SQ,and S-1 and S-2 samples are located in provincial road S20 and near Huaitoutala Town.The distribution of PAHs in lakes and rivers on the Qinghai-Tibet Plateau is consistent with that in soil,and the distribution pattern is closely related to human activities.The concentration of PAHs in lakes and rivers on the qinghai-tibet plateau is lower than that in lakes and rivers at home and abroad,and far lower than that in urban lakes.Compared with other regions of the Qinghai-Tibet Plateau,soil PAHs concentration is relatively low,and far lower than that of agricultural and InPustrial soils greatly affected by human beings.(3)The content of high-ring PAHs and carcinogenic PAHs in sediments had a good positive correlation with TOC,while low-ring and total PAHs content were not significantly correlated with TOC.The contents of high-rings PAHs and total PAHs in soil were positively correlated with TOC,while the contents of low-rings and carcinogenic PAHs were not significantly correlated with TOC.High-ring PAHs are more easily adsorbed by TOC.(4)The results of characteristic ratio method and principal component analysis showed that the sediments and soil PAHs were mainly derived from the mixture of combustion source and petroleum source.Biomass combustion source is the characteristic combustion source.(5)The ecological risk of PAHs in the surface sediments of lakes and rivers on the Qinghai-Tibet Plateau was evaluated by sediment quality standard,average effect interval median quotient method and benzopyrene equivalent concentration.The ecological toxicity of PAHs in the surface sediments of lakes and rivers on the Qinghai-Tibet Plateau is low and there is a weak ecological risk.Compared with the Dutch soil quality standards,the percentage of soil samples exceeding the standard is 78.26%.The results of benzopyrene equivalent concentration and lifetime carcinogenic risk evaluation showed that the soil around the lake was generally less toxic and had no health risks.