Luochuan Apple Woodland Soil Heavy Metal Environment Evaluation Research

In order to check the quality of soil environment for apple trees land in Luochuan and protect the pollution-free green apple production area in China, the paper studied the content change, migration, accumulation characteristics, the correlation among the elements and correlation between elements and particle size for the erght heavy metals such as As, Co., of Cr and Cu, Mn, Ni and Pb and Zn in soil in Luochuan and seven major elements such as Fe, Ca, K, Mg and Na, Si, Al, and explored the soil heavy metals availability and their influencing factors. The paper also evaluated and analysed soil heavy metal pollution state and the sources of heavy metal. The main conclusions and cognitions are described as follows:(1) The absolute content of the soil elements did not fully reflect the degree of heavy metal under the influence of human factors, but the relative variation of the soil element content can well reflect the depth of soil heavy metal pollution under the influence of human factors.(2) In the study area, As gathered at the depth range from0to2.0m, and Mn, Ni from0to1.5m. Pb, Cu, Co, Cr, Zn from0to0.5m, which indicated pollution depth of the metals under the influence of human factors. In addition, the major elements such as Fe, K element gather in the depth range from0to1.0m, which also showed that the pollution depth of the metals under the influence of human factors.(3) Pb presents lower degree of similarity with the content variation of other14elements. Ca and Na have a significant inverse relationship with other12elements apart from Pb element. The content variation between Fe, K, Al, Co, Cr, Cu, Mn and Ni has a significantly positive correlation respectively. The relation between As, Zn, Si and Mg respective and the ralation beteween As, Zn, Si, Mg and other11elements were positively related, but not significantly.(4) At the0.01confidence level,15elements have a the composition with the particle size less than0.05mm in the soil basically, and a negative correlation with the particle size greater than0.05mm, which indicated that the thinner soil particle size has higher ingredient content (<0.05mm), which was good for the cumulative enrichment of the soil elements. (5) As a reference value to the heavy metal content of the black loam soil environmental background values, the weakest regolith Nemero Composite Index and the evaluation of potential ecological risk index results showed that there are four sample plots greaterly influrenced by soil heavy metals, their soil are in the state of light pollution. In terms of the polluted inflution of apple tree land, the25-year was the most,20-year,15-year, and12-year less. According to the value of Nemero Composite Index and the potential ecological risk index, only the25-year apple tree land influenced by heavy metal greatly, which was is more than vigilance value0.7. Their soil is in a relatively clean state, and other plots are in a clean state. At present, the soil heavy metal environment of apple tree land in Luochuan is in line with the national green food producing soil environmental quality standards. Above three kinds of evaluation reference value of the single-factor evaluation results showed that As, Cr, Cu, soil had greater impacts on heavy metals in the soil environment, and other elements had smaller impacts.(6) The long-term utlization of pesticides and fertilizers is a major source of heavy metals in Luochuan apple tree lands. In order to avoid further soil contamination, appropriate restriction on the usage of pesticides is necessary.