Study On Pollution Characteristics And Risk Assessment Of Soil Heavy Metals On Highway Roadside

With the rapid development of highway construction and the sustained increase of highway mileage,aerosol particles produced by traffic activities,which have become one of the main sources of heavy metals(HMs)pollution in highway soil environment system.On the one hand,highway construction occupies a number of cultivated land,on the other hand,the HMs pollution sources sustained produced by traffic activities,which will cause concealment,permanent and potential hazards for highway roadside soil.Therefore,it is particularly important to future study soil HMs pollution and confirm pollution degree,distribution characteristics and influencing factors of soil highway roadside.The study was conducted on the roadside soil of different operating ages in the territory of Anshun,and chose three highway roads(Xixiu section of G60 highway,Xixiu section of G320 highway,Pingbai section of S102 highway).Detailed analysis the concentration distribution characteristics of different horizontal distances and spatial variations of different vertical depths in three roadside soil HMs(Cu,Zn,Ni,Cr,Cd and Pb)and explained the influenced factors.Based on geological accumulation index and modified potential ecological risk assessment index to evaluate soil HMs pollution,and applicated multivariate statistical method to analysis of source of HMs in soil highway roadside.The main conclusions of the study are as follows:(1)The mean values of soil HMs in the selected three highway were higher than the soil background value of Guizhou Province.The calculation results of the coefficient of variation showed that Cd in the three highway roadside soil shown high variation,which illustrated that the element greatly influenced by the external environment.(2)Highway as a linear pollution source,the migration velocity and settlement distance of different sizes of aerosol particles produced by traffic activities are different on both sides of the highway due to the influence of air turbulence of road surface caused by vehicle driving,which presented a different distribution pattern.The concentrations of Ni,Zn,Cr,Pb and Cd in three highway roadside soil increased to peak values as the distance from the roadside increasing,and decreased trend after peak,which appeared skewness distribution,the peak values areas located at the place where are apart from the roadbed about 5~20 meters.While the concentration of Cu in roadside soil decreased with the increasing distance,which appeared exponential decline distribution and the peak value located at the roadbed.(3)The concentrations of Ni,Cu,Cr and Cd in the North vertical section of three highway sections were accumulated in the place where are apart from the soil surface about 0~10 centimeter,however the concentrations of Pb was accumulated in the soil surface about 16~20 centimeter,and the concentration of Zn appeared pattern of sawtooth multimodal in vertical soil section.(4)The geological accumulation index showed Cd and Ni in soil HMs of three highway roadsides have reached the level of mild contamination,all other elements overall belong to pollution-free state,but some of them have reached the level of mild contamination.(5)The modified potential ecological risk assessment index showed that Cd has reached the level of moderate potential ecological risk,and the maximum single potential ecological risk index of all other elements were far from reaching the upper limit of slight risk.The three highway sections overall belong to moderate comprehensive potential ecological risk,minority samples have reached intensity comprehensive potential ecological risk.(6)According to the results of correlation analysis,principal component analysis and cluster analysis,the sources analysis results of HMs Ni,Zn,Cu,Cr,Pb and Cd in three highway sections are the same,its concentration are mainly influenced by traffic pollution sources.