贵州省毕节市威奢乡农田土壤环境质量特征研究

本文采用元素地球化学的研究理论与方法对贵州省毕节市威奢乡耕作土壤环境特征进行研究并采用单因子指数法和综合污染指数法对其环境质量进行科学评价,得出如下主要研究结果:威奢乡现代耕作土壤总体呈弱酸性,pH值介于5.10~7.38之间,平均值为6.12;有机质含量丰富,介于3.29%~12.06%之间,平均值为5.85%;土壤全氮含量介于1735~6325mg/kg之间,平均值为3722 mg/kg;全磷含量介于667.2~1579.69 mg/kg之间,平均值为1161.4 mg/kg;全钾含量介于5016.06~15063.03 mg/kg之间,平均值为9186.2 mg/kg,对比全国第二次土壤普查养分分级标准,研究区土壤全氮、全磷含量为一级,无需补充,但全钾含量为五级,应适量施加含钾元素肥料,以提高土壤肥力;研究区Ca、Mg元素含量均低于贵州省表层土壤平均值,应注意适量补充Ca、Mg元素;有害重金属元素Cr、Cd、As、Pb含量具有CrPbAsCd的区域特征,且Cr、Cd含量均高于贵州省表层土壤平均值。单因子污染指数法评价结果显示研究区农耕土壤Cd已经明显污染,成为该地区最主要的污染物。内梅罗综合污染指数法评价结果显示,研究区大部分土壤已达到严重污染程度(P综3)。其中,重金属Cd、Zn主要来源于外源污染,且大部分富集在土壤表层,给农业生产带来极大风险。

Research on the Characteristics of Agricultural Soil Environment in Weishe Town, Bijie City, Guizhou Province

This paper has used both element geochemistry theory and method to study the characteristics of the soil environment and applied the single pollution index and comprehensive pollution index to evaluate the environment quality of agricultural soil in Weishe Town, Bijie City, Guizhou Province.The main research results are as follows:modern agricultural soil in Weishe Town is of weak acidity,and its pH value varies between 5.10~7.38 with the mean value of 6.12; soil organic matter is very abundant and the contents are between 3.29%~12.06%, with the mean value of 5.85%; the contents of total N, total P, total K in the study area are between 1735~6325 mg/kg, 667.2~1579.69 mg/kg, 5016.06~15063.03 mg/kg, with the mean values of 3722 mg/kg, 1161.4 mg/kg, and 9186.2 mg/kg, respectively. According to the Classification Standard of the Nutrient Grading of National Second Soil Survey, total N and P in the study area are of the first class, which needn''t to be added. However, total K is at the fifth class which needs to be added in order to increase soil fertilization.The contents of Ca and Mg in the study area are lower than the average content in Guizhou Province, which should be added properly. The contents of the harmful heavy metals Cr, Cd, As and Pb in the surface soil are characterized as being Cr > Pb > As > Cd and the contents of Cr and Cd are higher than the average content in Guizhou Province, but the contents of As and Pb are lower than this value. From the single-factor pollution evaluation results, we can see that heavy metal Cd has become the most serious contaminant material in the agricultural soil, followed by Cu, Ni and Zn.The comprehensive pollution index indicates that most of the soil have been seriously polluted. Cd and Zn mainly come from the extraneous source pollution and most of them are concentrated in the surface soil, which has caused a great risk to agricultural production.