黄石沿江土壤镉的形态特征及生物可利用性

为了解黄石市沿长江冲积土壤中重金属镉直接和潜在的危害程度,为重金属污染防治提供科学依据,采用总量测定、Tessier连续提取法,分析研究了湖北黄石市沿江冲积土壤中重金属镉的总量及不同形态含量,镉含量采用火焰原子吸收分光光度法测定。结果表明,研究区土壤Cd全量都大于2mg/kg,不同形态Cd含量相对大小依次为残渣态铁锰氧化物结合态碳酸盐结合态有机物结合态离子交换态。其中残渣态占全量比例为58%,铁锰氧化物结合态为26%,碳酸盐结合态、有机物结合态、离子交换态分别为8%、4%和3%。可见研究区Cd的生物可利用态含量低,生物潜在可利用态较高,生物不可利用态含量最高;现有环境条件下的土壤Cd比较稳定,生物可利用性较低,对农作物的危害性较小。

Speciation Characteristics and Bioavailability of Cadmium in Soils along Yangtze River in Huangshi

To understand the direct and potential harm of cadmium in alluvial soils along the Yangtze River in Huangshi,Hubei Province, total content of Cd and its speciation characteristics were studied using Tessier sequential extraction method and flame atomic absorption spectrophotometry. Results showed that total Cd content of all soil samples were greater than 2mg/kg.Content of Cd ranked as residual fraction, Fe-Mn oxide bound fraction, carbonate bound fraction, organic bound fraction and ion exchange fraction, in which residual Cd accounted for 58%, and iron manganese oxide bound for 26%, while carbonate bound, organic matter bound and ion exchangeable were only for 8%, 4% and 3% respectively. It was concluded that bioavailable content of Cd was low, and speciation which cannot be used by plant was the highest. Cd in soils under the studied conditions was relatively stable and had little harm to crops.