An Assessment Of Soil Heavy Metal Pollution And Farm Products Health Risk On The Rare-earth Tailings Area

This paper analyzed the basic physical and chemical property and heavy metals of the soil in the rare-earth tailings area in Maoniuping, Mianning County, Sichuan Province. Taking soil environmental quality standards as a foundation for contrast, this paper discussed the relationship between heavy metals and the changes of distance and elevation change. Through analyzed the heavy metal content in regional agro-product, established the risk evaluation model for human health effects by soil heavy metals, and applied Monte Carlo method to control the non-determinacy, it discusses sensitivity factors that have impacted on evaluation results, and comparative analyzes the heavy metal element chemistry carcinogenicity risk and chemistry non-carcinogenicity risk probability in the region. Brings the soil pollution and the risk assessment of human health research to the region has the important significance. Research results show that:(1) In soil survey area, from the gross of eight kinds of heavy metal elements, it found that the most serious pollution problem is the Cd, compared with the soil environmental quality standard exceeded the rate of up to12times, followed by Ni, Cr,Cu elements common to exceed the standard, exceeded the range of1to2times; Pb element over of sampling point is less, but over range is larger; although the average of Zn, As, and Hg elements gross is not over standard value, but the gross of Zn element has approximately alert level standard; through Nemero pollution index method and geological cumulative method analyzed four species agricultural products of barley, rape, corn and rice, it found that the grosses of heavy metals is rape land＞barley land＞corn land＞rice land.(2) Looked from the directional distribution of heavy metals,8kinds of heavy metals in4different kinds of soils of entire tailings dam have fluctuated, but the trend shows that the content gradually decreases with the distance increases in the total sum; analyzed from an elevation position, in the rape oil, except that Cu is negatively related to the elevation position, the other7heavy metal elements are all positively related to it; in the rice oil, except that Ni is negatively related to the elevation position, the extra7heavy metal elements are all positively related to it; in the barley soil, the relations between Cu and Ni and the elevation position is positive correlation, other6kinds of elements assume negative correlation; in the corn soil, the relations between eliminates Pb and Zn and the elevation position is positive correlation, other6kinds of elements assume negative correlation.(3) The crowd’s health risk exposition appraisal result in the tailings dam region through the Monte Carlo simulation method shows that heavy metal enrichment coefficient is the maximal sensitivity index of the average daily exposure doses’ effect. Simultaneously, calculate the risk quotients of heavy metal element. Meanwhile, calculate the risk quotient of all heavy metal elements. Since the quotients of Pb, Cu, Cr, and Cd are over1. there is a potential risk of exposure. The maximum quotients of Pb and Cd have exceeded22and9respectively, while the quotient values of As, Hg and Zn are all below1.(4) Looked from the results of the assessment on the health risks of the four kinds of agricultural products’ food pathway in survey area based on the crystal ball software of the Monte Carlo method, in the four chemical elements of Cd, As, Pb, and Cr with carcinogenic, total carcinogenic lifetime risk average value and annual carcinogenicity risk average value of Cr are4.07E-03and5.82E-05, more than the standard levels of3.5E-03and5.0E-05set by the International Commission on Radiological Protection, and three elements of Cd, As and Pb are less than this standards; but contrast to the human health hazards maximum acceptable non-carcinogenic risk standard level of1.0E-06and the maximum acceptable lifetime non-carcinogenic risk level of7.0E-05, which proposed by the Swedish Environmental Protection Agency and Netherlands Department of Built Environment, in the seven elements of Cd, As, Pb, Hg, Cu, Zn and Cr, year non-carcinogenicity risk and lifetime non-carcinogenicity risk is significantly lower than international standards...