桑树修复农田镉和铅的土壤微环境特征分析

在江西某矿区周边重金属污染农田上栽植桑树,栽植三年后,分析桑园土壤中重金属含量、重金属各形态含量分布、土壤微生物分布、土壤酶活。分析结果表明,栽植桑树3年后,农田土壤Cd和Pb的修复指数达到96.87%和81.93%,含量分别为12.31mg/kg和595.44mg/kg。且重金属Cd和Pb均主要是富集在桑树根部。桑树不同部位中的Cd和Pb含量分布都表现为夏季含量最高,其次为春季,随后为秋季,最低为冬季。土壤中的Cd和Pb均存在金属可交换态、碳酸盐结合态、金属残渣态、Fe-Mn氧化物结合态、有机质结合态,分别以可交换态Cd和残渣态Pb作为主要形态分布。同时土壤中Pb和Cd各化学形态含量与土壤中微生物群落分布、土壤理化特征以及酶活性具有显著相关性。研究结果表明桑树修复矿区重金属过程中土壤微环境同步变化和改善,桑树栽植三年后,该矿区土壤环境质量达到三级标准。

Micro-environmental Characteristics of Cd and Pb Polluted Soil After Remediation by Mulberry

Mulberry trees were planted on heavy metal contaminated farmland around a mining area in Jiangxi Province. After 3 years, the contents of heavy metals, the distribution of various forms of heavy metals, the soil microbial distribution and the soil enzyme activities of the farmland were analyzed. The results showed that the remediation index of Cd and Pb reached 96.87% and 81.93%, respectively, and their content were 0.38 and 107.63 mg/kg, respectively. The Cd and Pb were mainly concentrated in the roots of mulberry. The highest content of Cd and Pb in different parts of the mulberry trees were found in summer, followed by spring and autumn, and the lowest content was in winter. The exchangeable metal state, carbonate bound state, metal residue state, Fe-Mn oxide bound state and organic matter bound state of Cd and Pb in soil were all could be detected. Exchangeable Cd and residual Pb were the main forms. At the same time, the chemical forms of Pb and Cd in soil were significantly correlated with the distribution of microbial communities, soil physical and chemical characteristics and enzyme activities. The results showed that the soil microenvironment could be changed and improved synchronously during the process of phytoremediation by mulberry trees in the mining area. After three years of mulberry planting, the quality of the soil environment in the mining area reached the third grade standard.