湖南某尾矿库周边农田土壤中重金属迁移转化规律研究
Study on Movement and Transformation of Heavy Metals in Agricultural Soils around a Tailing Pond in Hunan Province, China

为了探究湖南某尾矿库周边农田土壤中Cd、As的迁移转化规律，通过室内土柱淋滤实验，对土壤中Cd、As的含量和形态进行测定，并对其淋出特征进行分析。结果表明：淋滤前期两种条件下表土层和底土层中两种元素含量的削减率大小关系为Cd > 0 > As，中部土层中性条件下削减率为Cd > As > 0，酸性为Cd > 0 > As；淋滤中期两种条件下表土层两种元素削减率均表现为Cd > As > 0，其它层位含量变化差异明显；淋滤后期除表土层外其余各土层中Cd、As在不同淋滤条件下迁移规律相似。淋出液检测结果表明，酸性淋滤条件下两种元素的累积释放量表现为As > Cd，中性条件下表现为Cd > As，0~48天内酸性条件下淋出液中两种元素的浓度大小关系为As > Cd，中性条件关系为Cd > As，酸性条件促进了As的释放，同时淋出液中Cd、As两种元素的浓度随淋滤时间的延伸呈下降或平稳趋势，其对淋滤液酸度的敏感程度顺序为Cd > As。形态分析表明：土壤中有效态的Cd以酸可提取态为主，As主要以残渣态的形式存在于土壤中；相关性分析发现，有效态的Cd与土壤pH呈显著负相关，As与土壤有机质为负相关关系。酸可提取态(占比)的Cd随土壤中粘粒含量的增多而增大。酸可提取态和可氧化态的As含量随土壤粘粒的增多而显著增大。本研究为后续农田土壤重金属污染防治提供科学依据。
In order to explore the migration and transformation of Cd and As in the agricultural soil around a tailing pond in Hunan Province, the content and form of Cd and As in the soil were determined by the soil column leaching experiment, and the leaching characteristics were analyzed. The results showed that: In the early stage of leaching, the relationship between the reduction rate of the two elements in the topsoil and subsoil is Cd > 0 > As, that in the middle soil is Cd > As > 0, and that in the acid is Cd > 0 > As; In the middle stage of leaching, the reduction rates of the two elements in the topsoil were Cd > As > 0, and the content of the other layers changed significantly; in the later stage of leaching, except for the topsoil, the migration of Cd and As in other soil layers was similar under different leaching conditions. The results showed that the cumulative release of the two elements was As > Cd under acid leaching condition, and As > Cd under neutral condition. The concentration of the two elements in the leaching solution was As > Cd within 0~48 days under acid condition, and Cd > As under neutral condition. Acid condition promoted the release of As, At the same time, the concentration of Cd and As in the leaching solution decreased or stabilized with the extension of leaching time, and the order of sensitivity to the acidity of the leaching solution was Cd > As. The morphological analysis showed that the available Cd in soil was mainly acid extractable, and As was mainly in the form of residue; the correlation analysis showed that the effective Cd was negatively correlated with soil pH, and As was negatively correlated with soil organic matter. The ratio of acid extractable Cd increased with the increase of clay content. The content of As in