The Study On The Spatial Distribution And Pollution Assessment Of Heavy Metal Elements In Soil Of Hefei Area Based On Environmental Geochemical Baseline

The heavy metal elements pollution is the important factor that breaks thesoil environment and endanger to the human body health directly or indirectly.This paper studies the spatial distribution of heavy metal elements based onenvironmental geochemical baseline in the soil of DaXing and YiCheng townswhere are representatived in HeFei, and assesses the pollution degree.A geochemical baseline for an element refers to its natural variations inconcentration in surficial environment and is the basis of environmentalpollution analysis. With the use of normalization approach and statisticallyanalyzing method,the environmetal geochemical baseline of heavy metalelements in Hefei area is ascertained. Obtain the thresholds of heavy metalelements in soil of Hefei area by the Fractal Method, Compare thegeochemical baseline with background value and threshold.The research results express that, the spatial variation regulation of theelements in soil of DaXing area is as follows: The ratios of nugget value to sillvalue are [C₀/(C₀+C)] Cu＞Hg＞Cd＞Pb＞As＞Zn, The ratios of nugget valueto sill value of Cu elements is larger than 75%, belong to low correlation inspace. The other are between 25% and 75%, they belong to median correlationin space.The spatial variation regulation of the elements in soil in YiCheng area isas follows: The ratios of nugget value to sill value are [C₀/(C₀+C)]Cd＞Hg＞Zn＞As＞Pb＞Cu, The ratios of nugget value to sill value of Cd,Hgelements are larger than 75%, belong to low correlation in space. The other arebetween 25% and 75%, they belong to median correlation in space.Comparing the results of the three methods: Kriging,inverse distance w-eighting and radial basis functions interpolation methods, ascertain the best m-ethod for each method:in DaXing area, Cu(Kriging), Pb(radial basisfunctions -interpolation), Zn(radial basis functions interpolation),Cd(Kriging), A -s(Kriging), Hg(radial basis functions interpolation); and inYiCheng area, Cu(Kriging), Pb(radial basis functions interpolation), Zn(inverse distance weighting), Cd(radial basis functions interpolation),As(Kriging), Hg(radial basis functions interpolation).The index of geoaccumulation is important parameter to assessing heavymetal pollution in soil and sediments.Through the Geoaccumulation Indexcalculation of elements in DaXin area,it is shown that most elements are incontamination level of 1 to 2,uncontaminated/slightly contaminated;someelements are in contamination level of 3 to 5,slightly contaminated/moderatelycontaminated.According to Geoacuumulation Index,the contamination degreefrom strong to weak is Zn＞Pb＞As＞Cu＞Cd＞Hg; Through the GeoaccumulationIndex calculation of elements in YiCheng area,it is shown that most elementsare in contamination level of 1 to 2,uncontaminated/slightly cont amina-ted;some elements are in contamination level of 3 to 4,slightly contain inat-ed/moderately contaminated.According to Geoacuumulation Index,the conta-mina tion degree from strong to weak is Zn＞Cu＞Cd＞Pb＞As＞Hg.The Enrichment Factor of six heavy metal elements in DaXin area are allbiger than 1,which demonstrates the above regions are more seriouslyinfluenced by human activity.In YiCheng area, The Enrichment Factor of Zn,Cd,Hg are biger than 1,the other elements are smaller than 1, whichdemonstrates the above regions are weak influenced by human activity,uncontaminated/slightly contaminated.The analysis of Pollution Load Index shows:In DaXin area,the mainpolluted areas are centered on steel mill,chemical plant,passenger transportstation,tile mill,packinghouse,lime mill and paper mill; In YiCheng area,only around breeding fields,water factory,ChaoHu are slightly contaminated.The distributing rule of section plane of soil is: the capacity of portraittransfer about Hg,Cd elements is weak, they have been enrichment in 0～20cmof topsoil, the capacity of portrait transfer about As element is strong, the capacity of portrait transfer about Cu,Zn elements is strong, they have been enrichment in depth of section plane. The content of Pb doesn't change in all sectionplanes.The different pollution characeristics of heavy metals in different function region shows: DaXin as a industrial estate is higer than YiCheng as a farmbelt. DaXin can be classified into two groups: Cu-Zn-Cd-Pb-As,Hg;and YiCheng can be classified into three groups: Cu-Pb-Zn-As,Cd,Hg. In addition, DaXin town has the possibility to break out DGH of Cu,Zn elements.