恩施地区土壤与农作物硒镉地球化学特征

Geochemical characteristics of selenium and cadmium in soil and crops in Enshi area

恩施州已开展的1∶25万土地地球化学调查结果显示,恩施地区表层土壤中硒含量丰富,但镉含量同样较高。笔者以该地区3950件表层土壤及362件作物硒、镉等含量指标为基础,讨论了硒、镉元素地球化学特征,共生成因以及不同种类作物对两种元素的吸收富集能力。结果表明,土壤中硒、镉呈伴生关系,含量分布主要受控于该地区二叠系发育的黑色岩系成土母质,赋存状态与土壤中的有机质和硫化物密切相关。不同作物生物富集系数对比结果显示,银杏、玉米和茶叶对硒的吸收能力高于镉,可作为恩施地区富硒农产品开发的优选作物,同时还应考虑土壤的pH值,中碱性土壤农产品镉富集风险较低。此外,硒对于镉有解毒作用,高硒环境将会显著降低镉对人体的健康风险。

The 1∶25 million land geochemical survey conducted in Enshi area shows that the surface soil in Enshi area is rich in selenium,and the content of cadmium is also high.Based on the data of 3950 surface soil samples and 362 crop samples in this area,the geochemical characteristics of selenium and cadmium,co-generation factors,and the capability of different types of crops for absorbing and enriching the two elements are discussed.The results show that the selenium and cadmium in the surface soil of Enshi area is associated with each other.The distribution of the two elements is mainly controlled by the Permian soil parent material,and the occurrence of selenium and cadmium is closely related to organic matter and sulfide in soil.Comparison of BCF of selenium and cadmium in different crops shows that ginkgo,corn and tea have higher absorption capacity for selenium than for cadmium,and hence these crops could be used as the preferred crops for the development of selenium-enriched agricultural products in Enshi area.At the same time,the pH of the soil should also be considered.The medium alkaline soil may be more likely to avoid the risk of cadmium enrichment in agricultural products.In addition,selenium has a detoxifying effect on cadmium.Selenium-rich environment will significantly reduce the harm of cadmium to human body.