Background Values Of Heavy Metal In Surface Dust In The Vicinity Of Kaifeng And Their Application

Researches on background values of heavy metal in soil and water are many at present, but study onbackground values of heavy metal in surface are less. Kaifeng is located in the North China Plain, and it isan important chemical industry area of Henan Province, the region surrounding the city is an importantmain grain producing area of Henan province. Based on field investigation and sampling and laboratoryanalysis, we carry out the study on background values of elements in surface dust.In accordance with the principle of less human disturbance, uniformity and randomness of sampledistribution,96dust samples and49soil samples in the region surrounding Kaifeng are collected. Thesampling points are selected from Ancient graves, large scale woodland, loaning, larger permanent fieldedges and canal banks and long-term desert ground, which are more than10kilometers away from KaifengCity and more than5kilometers from counties or towns,0.5kilometers from villages and1kilometer frommain road.11trace element contents of Cu, Zn, Ni, Pb, Cr, Cd are measured by ICP-MS. Recovery testand mean control chart are applicated in checking process for quality control, the recovery ratio is between95%and105%, the assurance sample values are all between upper and lower limit and meet the qualityrequirements. Referring to GB/T4883–2008, dust and soil heavy metal values are respectively checkedby Grubbs test and Deviation-kurtosis test,15discrete data of dust and2of soil are eliminated, and1578effective data are got.According to methods of the analysis of background values of elements in soils, we carry out thestudy on heavy metal background value in surface dust and soil in the region surrounding Kaifeng, and campare it with background value in surface soil of different regions in China, then assess the level ofheavy metal pollution in surface dust in kindergarten of Kaifeng, and the main conclusions are as follows：1. Data distribution test methods of W test, confidence band test and the Deviation-kurtosis test areused to check the distribution of11sets of data. The results show that V、Co、Ni and Sr show normaldistribution, Cr、Cu、Zn、Cd and Pb show log-normal distribution, and Ga and Sb skewed distribution.2. Arithmetic mean and standard deviation are used to describe the normally distributing elements’background value and their range, geometric mean and Geometric standard deviation are used to describethe log-normally distributing elements’ background value and their range, and median is used to describeskewed distributing elements’ background value and5-95%corresponding interval to describe their range.The results are as follows.The background value of V、Cr、Co、Ni、Cu、Zn、Ga、Sr、Cd、Sb and Pb respectively are85.12,46.51,9.72,26.43,20.54,77.21,36.30,24.99,0.304,1.20, and24.58，and the range41.08～129.16mg/kg,1.64～68.37,5.32～14.12,12.55～40.32,11.38～37.08,47.80～124.71,32.59～42.19,177.82～272.15,0.152～0.610,0.88～1.76and14.73～41.02mg/kg.3. The background values of Cu, Zn, Pb, Cd, Cr and Sb in surface dust are higher than the soilbackground value of the region, they are respectively1.02,1.06,1.07,101,1.26and1.35times of it.According to significance testing, the background value of Sb in surface dust and soil is significantlydifferent (p＜0.05) from Cr, and there is no significant difference among the others. The backgroundvalues of Co, Sr, Ni and Ga in surface dust are lower, but not significantly, to that in surface soil, which arerespectively0.85,0.95,0.87and0.92times of that in surface soil. And camparing with the backgroundvalue of in moisture soil in area of the lower reaches of the Yellow River and surface soil in Henanprovince, we get a similar conclusion. It is probably because of that the heavy metals of Cu, Zn, Pb, Cr and Sb in surface dust are mainly attach on relatively minor soil particles so they are easily to occuratmosphere transport, and Co, Sr and Ga on relatively large soil particles so hardly to occur atmospheretransport. It is also probably because of that the first ones is more significantly influenced by humanactivities so accumulate more on the surface of soil and higher in surface dust after atmosphere transportand sedimentation but the surface background value is the mean value from0to20cm in soil.4. Respectively based on background values in surface dust and moisture soil of the lower reaches ofthe Yellow River, the condition of heavy metal pollution in dust in kindergarten of Kaifeng is assessed byIgeoand RI. The results show that when it is assessed by Igeobased on the two standards, the class ofpollution of both Cu and Pb is though not changed, but it is smaller based on background value in surfacedust, and the pollution of Cr and Zn based on background value in dust is less than that based onbackground value in soil. When it is assessed by RI, the pollution of all the heavy metals is within the sameclass based on the two standards, but it is4.32-7.34%lower based on background value in dust thanbackground value in soil. So it will be on the high side when surface dust pollution is aassessed based onsoil background value, in other words, it will be overvalued. Then it is more accordant with reality toassess the pollution of surface dust based on background value in surface dust.