| The soil, the material basis of agricultural production activities,is one complicatedform and evolution of history and nature complexes. The spatial variability of soil heavymetals is not only able to reveal the distribution of heavy metals in soil and its variabilitycharacteristics, but also explain the natural and human activities on the impact of heavymetals to guid mankind agricultural production and provide rational scientific basis forfertilization.The study was based on the three mountain area vegetable matrix in Wuhu.72soilsamples were collected. Soil samples were analyzed for Cu, Zn, Pb, Cd and Cr, Hg, As,organic matter and pH.The spatial variability of heavy metals were analyzed through theway of Geo-statistics,GIS spatial analysis and sequential Gaussian simulation method;the spatial distribution pattern of soil properties was revealed; the uncertainty evaluationwas assessed under the condition of more than a given threshold on the heavy metalindicators. What’s more, the potential ecological risk assessments of various metalswhich may cause hazards were evaluated too.The coefficient of variation of soil heavy metals in the region was between21.99%and61.50%.The coefficient of variation of Cu, Pb, Cr and Cd were relatively large.Itcould be inferred that the distribution of these four heavy metals was largely influencedby human. Cu, Zn, Pb, Cr, Cd, Hg and As all showed various degrees of the nuggeteffect; Cu, Cr, Hg, the nugget effect less than25%had strong spatial correlation; Zn,Cd, from27%to50%,belonged to the moderate spatial correlation; Pb, As, more than75%,had weak correlation.In order to determine the spatial distribution pattern of soil heavy metals, theordinary kriging interpolation method was applied to the region of soil heavy metals data.Consequently, the results can objectively reflected the heavy metal content distribution.The region with more Cu was mainly concentrated in the northeast and southwest.However, southwest was the most serious; the highest value was found near the Best Industrial Area in the southwest. Zn which presented predominantly zonal distributiondecreased from the Best to the surrounding radially.Yet the area were not heavilypolluted by Zn, the highest value reached to102.86mg/kg. Pb mainly distributed in theBest Industrial Area and Country Garden, then descended.Similarly, Hg mainly presentedzonal distribution, maximum value in Takaoka, radially descended, and were relativelyevenly distributed. Cr in the three mountains in eastern Country Garden District,presented high value distribution as an island and radially decreased from the center tothe surrounding. Cd, far exceeding the national soil background value (0.2mg/kg), waspatchy or zonal distribution and the pollution was more serious.The highest value of Asin the region was22.264g/kg, it located in the center of the three mountainous areas anddecreased outwards gradually.Sequential gaussian simulation method was applied to uncertainty analysis of theproperty index which exceeded the threshold. The threshold of Cu, Zn, Pb, Cd,Cr, Hgand As were35,100,35,0.2,90,0.15and15mg/kg. After1000times sequential gaussiansimulation, the greater probability areas where the heavy metals index were more thanthese threshold were significantly smaller than the simulated pictures. What’s more, theprobabilities were more than80%, indicating that these high probability areas coulddetermine the range of greater than the threshold. Due to the low probability of greaterthan the threshold, the other low-probability areas can not be determined.The results of the ecology risk warning evaluation showed that from the singleindex Cu, Zn, Hg, and As belonged to the no warning level. In addition to Baoding streetwas no pollution of Pb, three shan street, longhu street, three mountain belonged to thewarning evaluation. In the all of three mountainous regions Cd pollution belonged to theno warning level. From comprehensive index we can see three shan street in the heavymetal pollution early warning range, the other were no risk warning.Based on the ecological risk index, all kinds of vegetables were not contaminated byCu, Zn. In addition to the average of Pb pollution index more than1in tomatoesbelonging to light pollution, the rest were free from contamination. Following were thepollution status of Cd: of all the vegetables the Cd pollution status in pepper was themost serious. Conversely, the pollution was minimized in beans, tomatoes and huzi.Others had no pollution.The enrichment coefficients of the heavy metal in vegetables showed that the mobility of Cd was strong and easily absorbed by plants. Relatively, the mobility of Pb,Cu, Zn was poorer with the sequence of Cd>Cu>Pb>Zn. According to the calculationand evaluation of human body health risk index of Cu, Zn, Pb and Cd, it was found thatHQ of nine kinds of vegetables were all less than1showing that nine vegetables in threemountainous area would not cause the health of the residents risk. |
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