Accumulation And Influencing Factors Of Heavy Metals In The Soil Along The Road In Hohhot

The important component of urban ecosystems, urban soil, not only can be able to accommodate buffering substances contamination and decontamination, but also may go through the ecosystem pollutants especially heavy metal pollutants on human beings.With the increasing of urban population, motor vehicles, and the development of industry, the intensity of heavy metals is increasing day by day. So, in the process of urbanization, doing a deep survey of accumulating and evaluating heavy metals of urban roads is very necessary.In this paper, Using multi-factor comprehensive evaluation method to study the developing process of Hohhot, especial in the accumulation of heavy metals in soil.First, the researcher according to the different levels of the road pick up soil samples to measure soil pH value, organic matter content, heavy metals Fe, Pb, Cu, Mn, Cr content, totaling 130 samples. Measurements show that the longer opening, the greater traffic, the concentration and accumulation of heavy metals in the soil would be greater, the heavy metal content of Highway> National>Provincial highway> Country highway. In addition to Cu, Mn, Cr element of the Country highway, the average content of heavy metals in soil of the remaining soil road were higher than background values of Inner Mongolia Autonomous Region. The heavy metals of Fe, Pb, Cu, Mn, Cr contents of the road surface soil are 1.49 times; 2.74 times; 1.39 times; 1.22 times and 1.43 times of the background value of Inner Mongolia Autonomous Region. Studies have shown that heavy metal content of the road surface soil in the side of the road reaches a maximum and then decreases with increasing distance, within the vicinity of 30-50m reaches to the second peak, and then gradually declines to the soil background values. Heavy metal concentrations peak appears for the reasons of leaving the roadside embankment at a distance, it may be due to fast moving vehicles leading to turbulence caused by nearby embankment. And after leaving the roadbed some distance, turbulence disappears in favor of particle sedimentation, resulting from heavy metals of the street soil beside the road was skewed distribution. Secondly, through analyzing soil paired sample and T-test on the upwind side and downwind side, statistics show that:the average concentration of heavy metals in soil and peak concentration content of the upwind side is generally appears closer to the road in downwind side. Through correlation analysis, there is strong correlation among Fe, Pb, Mn, and Cr of heavy metals. They might have the same source. Cu and other elements of the correlation coefficient are less than 0.6. After cluster analysis and principal component analysis, to identify the source of heavy metals in sediments road, five heavy metals are identified as two main components:the first principal component (contribution rate of 70% or more) major comes from traffic activities, including Fe, Pb, Cr, Mn;the second element is the main component of Cu, named "natural source factor"; Finally, using the national secondary standard soil environmental quality standards (GB15618-1995) to calculate the accumulation degree of heavy metals in soil on both sides of the road in Hohhot (Highway> National>Provincial highway>Country highway.),which integrated digital potential ecological risk:RI=EEri= 1.77. The roads of Hohhot show heavy metals Cu, Cr, Pb around the surface of soil of overall environment are good. Five kinds of heavy metals accumulate degree lower than those in Tokyo, Guangzhou and other cities significantly. This may be concerned with Hohhot is strengthening ecological construction in recent years and the short history of urban development.