碳酸盐岩地区水旱轮作土壤重金属垂直分布特征及赋存形态研究

Study on Vertical Distribution Characteristics and Occurrence Forms of Heavy Metals in Soil of Water and Drought Rotation in Carbonate Area

以贵州遵义播州区石板镇水旱轮作的石灰性水稻土为试材,利用电感耦合等离子发射光谱,测定了土壤中重金属Cd、Cr、Cu、Zn和Pb的含量,研究了碳酸盐岩地区水旱轮作土壤重金属赋存形态、垂直分布、淋滤迁移特征以及生态危害,以期为碳酸盐岩地区农田土壤重金属污染综合防治、农产品质量安全和地下水安全提供参考依据。结果表明:在国家土壤环境质量标准(GB15618-2018)规定范围内,土壤重金属Cd超标率达80%,重金属Cr、Cu、Zn和Pb样点达标率为100%;研究区土壤除了Cr之外,土壤pH、有机质、重金属Cd、Zn、Cu和Pb含量均随着土层深度的加深呈下降趋势;各土层重金属淋失率呈现Zn>Cu>Cd>Cr>Pb的特征;5种重金属各形态含量随着土层深度的加深无明显变化,且5种重金属在各土层中主要以残渣态存在;地累积综合污染指数法中,研究区各土层均无污染,而综合潜在生态风险指数法中,研究区各土层均为轻微风险等级,其中Cd是最主要的生态风险元素,其次是Pb。

Taking the calcareous paddy soil in Shiban Town,Bozhou District,Zunyi,Guizhou Province as the test material,the contents of heavy metals Cd,Cr,Cu,Zn and Pb in the soil were determined by inductively coupled plasma emission spectrometry.The occurrence forms,vertical distribution,leaching and migration characteristics and ecological hazards of heavy metals in the soil of water and drought rotation in carbonate rock area were studied,in order to provide reference for the comprehensive prevention and control of heavy metal pollution in farmland soil in carbonate rock area and scientific basis for the quality and safety of agricultural products and groundwater safety.The results showed that within the scope of national soil environmental quality standard(GB15618-2018),the exceeding standard rate of soil heavy metal Cd was 80%,and the reaching standard rate of heavy metal Cr,Cu,Zn and Pb was 100%.In addition to Cr,the contents of soil pH,organic matter,heavy metals Cd,Zn,Cu and Pb decreased with the deepening of soil depth.The leaching rate of heavy metals in each soil layer showed the characteristics of Zn>Cu>Cd>Cr>Pb.The content of each form of the five heavy metals did not change significantly with the deepening of soil depth,and the five heavy metals mainly existed in residual form in each soil layer.In the cumulative comprehensive pollution index method,all soil layers in the study area were free of pollution,while in the comprehensive potential ecological risk index method,all soil layers in the study area were at a slight risk level,in which Cd was the most important ecological risk element,followed by Pb.