| Polycyclic Aromatic Hydrocarbons（PAHs）,as a group of semi-volatile and persistent toxic pollutants,are widely existing in various environmental media.They can pose hazards to animals,plants and human bodies through the migration and transmission of various environmental media,triggering potential ecological security risks and attracting extensive attention from the international community.Pollution of PAHs in soil has become a thorny problem both at home and abroad.At present,the study of Soil PAHs pollution is one of the hotspots in the environmental field.In terrestrial ecosystems,topsoil is the most important sink of PAHs,and a series of physical and chemical changes will occur after PAHs enters the soil.To solve these problems,a large number of experiments has conducted for PAHs in soil environment and exploration in recent years,but most previous studies of PAHs monitoring and attribution of concentration within the scope of the small scale area,and lack for the national scale of PAHs in soil research in environmental media,this is bad for our further understanding of the spatial and differential rules of under a wide range of PAHs.In order to understand the content status and spatial distribution of PAHs in surface soil in China comprehensively,this paper collected and sorted out the content data of 16 PAHs listed as the priority control by US EPA in 208 published literatures from 1999 to 2018,so as to build the content and attribute database of PAHs in the national surface soil.The scope of this study includes 31 provinces（cities and autonomous regions）except Hainan province,Taiwan province and Macao special administrative region,which are divided into six regions according to geographical location,namely northeast,north,east,central and south,southwest and northwest regions.Based on semi-variance analysis and Arc GIS spatial interpolation technology,the content characteristics and spatial distribution of PAHs in surface soil in China were obtained.The main sources and influencing factors of PAHs were quantitatively analyzed by using a variety of statistical methods and geographical detector models.The research results have certain reference value for the scientific control and prevention of soil PAHs pollution in China,and also have certain positive significance for China to actively implement the Stockholm convention.The research results show that:（1）The surface soil of China was within the concentration range of ND（undetected）～ 65500 ng·g-1,with the median value of 381.9 ng·g-1 and the average value is 1217ng·g-1.Only fluoranthene（Fla）in 16 kinds of PAHs was moderately variable,and the remaining 15 kinds of PAHs components were strongly variable.The range of concentration of 2-3 ring low-cyclic aromatic hydrocarbons is nd-5210 ng·g-1,with an average value of 53.1 ng·g-1,accounting for 26.8% of the total.The PAHs concentration of ring 4 was between nd-14733 ng·g-1,and the average was 106.8 ng·g-1,The PAHs concentration of ring 5-6 was between nd-4671 ng·g-1,and the average was 65.4 ng·g-1,and the middle and high PAHs accounted for about 73.2% of the total.（2）According to the analysis of variance and the parameters obtained from the fitting,and carry out the ordinary kriging interpolation,extraction and analysis of the content of the interpolation to get value,find out that our country average content of PAHs in the surface soil spatial distribution has obvious regional characteristics,from north China,northeast China,east China,central south and northwest to the decreasing in southwest China,the average contents of ∑ 16 PAHs in soils in north China is about 2.5 times of the southwest;The content of soil PAHs in China is generally at the level of medium and low pollution,and the proportion of medium pollution,slight pollution and unpolluted soil is about 22.6%,71.1% and6.3%,respectively.（3）Relative abundance method,isomer ratio method and principal component analysis method were used to determine and identify the sources of PAHs in surface soil qualitatively and quantitatively,and it was found that the three analysis results were relatively consistent.PAHs comes from a wide range of sources in China’s soil environment,including coal,biomass,liquid fossil fuel combustion and petroleum pollution sources.The relative abundance of rings reflects that PAHs mainly comes from combustion sources.According to the molecular ratio of four isomers,the combustion source is the main pollution source of soil PAHs in China.The results of principal component analysis show that traffic emission source,coal burning source and biomass combustion source are the most important three sources,and their contribution rates are 46.4%,36.8% and 16.8% respectively.（4）The use of the geographical probe factor of detectors,ecological detector and interaction detector respectively for seven kinds of natural factors and 11 kinds of social and economic factors of quantitative analysis,detection results show that the soil type,land use type,annual average temperature,annualaverage precipitation and elevation significantly are all affect the distribution of the soil PAHs contents in our country,It is the main impact factor of all kinds of natural factors;National key polluting enterprises are the main influencing factors of social and economic factors,while population density and coal consumption are the secondary influencing factors of PAHs spatial distribution.The interaction between multiple factors is reflected in the synergistic effect of nonlinear enhancement and dual-factor enhancement,among which the interaction between soil type and average annual temperature,and between pollution enterprises and per capita GDP has the largest impact on soil PAHs. |
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