Study On The Status Of Heavy Metal Contamination In Urban Roadside Soil In Xi’an

The paper took the topsoil (depthfrom0to20cm) of Xi ’an highway roadside as researchobject. It studied the conductivity, salinity, pH, ammoniumnitrogen, availableP, available K,organic matter, cation exchange capacity and granularity of soil systematically.Theconcentrations of Cd, Cr, Cu, Ni, Pb, Zn in soil was measured via ICP-OES and engageinductively coupled plasma emission spectrometer. The paper analyzed the distributionregularity of heavy metals in topsoil and pollution characteristics. Using the corrected singlefactor pollution index, Nemerow pollution index and geoaccumulation index,the heavy metalpollution of Soil samples were evaluated.The heavy metal pollution and potential risks of soilwere analyzed by the index method of potential ecological risk. The correlation between theamount of heavy metals and soil pHysicochemical property,the amount and traffic volume anddifferent elements had been achieved by employing Statistical software SPSS18.0.Specificresearch results are as follows:1. The topsoil of Xi’an was alkaline,5.56%of samples were salinization.The contentsof availableP and K stayed in higher level in research area. The distribution frequency of thecontent of soil organic matter were8.33%,33.33%,41.67%,11.11%and5.56%at level2,3,4,5and6respectively. Through testing soil granularity, among soil samples, particle soil was75%, while sticky soil was25%of them.2. In soil from Xi’an roadside, apart from Ni, the concentrations of all other5heavymetal elements were higher background value. It indicated that the topsoil had been pollutedby heavy metals in different degrees.3. In study area, heavy metals like Cd, Cu, Pb and Zn in topsoil were mostly influencedby traffic volume.4. The analysis of correlation between heavy metal concentration and traffic volumeshowed that only Cr and Ni did not demonstrate good correlation. The other were alldecreased via the reduction of traffic volume. But the max of six elements’ concentrationstayed in the sampling point of north, west and east2nd ring which had lower traffic volumethan south2nd ring. This was due to that west and east surburb were old industrial regions,and there were many large and medium-sized machinery manufacturing enterprises existed innorth surburb.5. Zn had a notable correlation with Cd, Cu and Pb and Cu had a notable correlationwith Pb as well. Except for Cr and Ni, the amount of last four elements were all positively correlated to organic matter, conductivity, salinity, which means absorbing and storing heavymetals were all affected by organic matter, conductivity, salinity.6. Using Nemerow pollution index and geoaccumulation index that based on correctedsingle factor pollution index to evaluate the soil in research area both found that it wasseriously polluted by Cd and clean of Ni. The heavy metal potential ecological risk levels ofXi’an roadside soil were order as Cd>Pb>Cu> Ni> Zn> Cr, and the comprehensive potentialecological risk was medium-high level. The potential ecological risk levels of differentlyfuntional roads were order as2nd ring> high speed highway> high speed side road.