熟污泥改良土壤中Cd的形态分布特征和生物有效性

通过苜蓿盆栽实验和Tessier五步提取法，研究了不同比例的堆肥污泥施入黄土后，土壤中Cd的形态分布和生物有效性及重金属在施污土壤-苜蓿中的迁移转化规律。结果表明：不同比例的污泥施入黄土后，随着污泥施入量的增加，土壤中Cd的主要赋存形态由对照组的不可利用态(残渣态)向潜在有效态(铁锰氧化态)转化，污泥的施入提高了重金属Cd的生物有效性；苜蓿的种植对施污根际土中Cd的活性产生了钝化作用，使施污黄土根际土壤中潜在有效态Cd主要向不可利用态的Cd转化；苜蓿各器官对Cd均有富集和转移能力，苜蓿各部位重金属Cd含量的分布规律为：根部>茎叶部；线性回归分析结果表明：碳酸盐结合态Cd是苜蓿茎叶部和根部吸收Cd的主要贡献形态；因此在实际生产时须严格控制污泥的施用量，以避免Cd在苜蓿体内富集危害动物和人体健康。

Morphological Distribution and Bioavailability of Cd in Soil Amended with Sludge

The morphological distribution and bioavailability of cadmium (Cd) in soil and the migration and transformation of Cd in soil-alfalfa system were studied by carrying out pot experiments. Cooked sludge were added to loess at the ratios of (0%, 0.5%, 1.5%, 3%, 6%, 10% and 15%). With the increases in sludge ratios, some Cd in unusable state (or residual state) in the soil was transformed to potential available state (iron-manganese oxidation state). Also, the sludge application increased the bioavailability of Cd. The planting of alfalfa had a passivation effect on the morphology of Cd in the rhizosphere soil, where the form of Cd was transformed from the potential available state to the unusable state. All organs of alfalfa plants had the ability to accumulate and transfer Cd. The regularities of the distribution of Cd in the organs of alfalfa plant were root > stem and leaf. A stepwise regression analysis showed the carbonate-bound Cd was the main contributor to the accumulation of Cd in the leaves and roots of alfalfa. Therefore, the application amount of sludge must be strictly controlled in agricultural practices to avoid the accumulation of Cd in alfalfa that may pose risks to animals and human health.