不同类型土壤镉含量对香芋镉吸收的影响

为探明香芋(Colocasia esculenta)镉(Cd)超标的关键原因,在湖南临武香芋主产区分别选择紫色页岩和第四纪红壤发育的Cd污染水稻土,研究土壤Cd含量、Cd活性及土壤基本理化性质对香芋Cd吸收的影响,以期为香芋的安全种植提供技术支撑。结果表明,两个试验点所有香芋Cd质量分数皆超过食品安全国家标准(0.1 mg·kg^-1),且各试验点内田块间土壤Cd含量、pH差异显著,而土壤有机质和阳离子交换量变异较小;紫色页岩发育的中碱性水稻土壤Cd活性、Cd在土壤-香芋系统中的转移系数(TFstem/taro、TFtaro/soil)皆低于第四纪红壤发育的酸性水稻土;紫色页岩发育的中碱性水稻土中,香芋Cd含量主要受土壤全Cd、TFtaro/soil的正调控;而第四纪红壤发育的酸性水稻土壤中,香芋Cd含量既受土壤全Cd、DTPA-Cd、TFtaro/soil的正调控,还受土壤pH的负调控。为实现香芋的安全生产,紫色页岩发育的中碱性水稻土中,应优先选择Cd吸收能力较低的香芋品种,或选择土壤全Cd低于0.65 mg·kg^-1的土壤进行种植;而在第四纪红壤发育的酸性水稻土壤中,则可优先选择Cd吸收能力较低的香芋品种,或选择土壤全Cd含量低于0.41 mg·kg^-1的土壤,或调理土壤pH至6.26以上,以及钝化土壤DTPA-Cd至0.19 mg·kg^-1以下的技术措施,抑制土壤Cd向香芋的迁移转运。

Effects of Cadmium Content in Different Soil Types on Cadmium Absorption in Taro

In order to identify the key factor for cadmium(Cd)contamination of taro(Colocasia esculenta),the Cd polluted soil derived from purple shale and quaternary red soil in Linwu,Hunan,were selected to study the effects of soil Cd content,activity and soil physical-chemical proprieties on Cd uptake by taro,providing technical support for the safe planting of taro.The results showed that all taros in two sites exceeded the national food safety standard(0.1 mg·kg^-1),and there were significant differences in soil Cd content and pH between the plots in each site,while the soil organic matter and cation exchange capacity had little variation.In the soil-taro system,the Cd activity and Cd transfer coefficient(TFstem/taro and TFtaro/soil)in the alkaline paddy soil derived from purple shale were lower than that in the acid soil developed from quaternary red soil.Moreover,the taro Cd content was positively regulated by total soil Cd content and TFtaro/soil in the alkaline paddy soil derived from purple shale;while in the acid soil developed from quaternary red soil,the taro Cd content was not only positively regulated by total soil Cd content,DTPA-Cd and TFtaro/soil,but was negatively controlled by soil pH.Therefore,aiming at the safety production of taro,a preference is to choose the taro species with low Cd absorption capacity,or to select the soil with the total Cd content<0.65 mg·kg^-1 in the alkaline paddy soil derived from purple shale.As for the acid soil developed from quaternary red soil,it is also preferential to plant taro species with low Cd absorption capacity.Future,the following actions can be conduct to inhibit the migration of soil Cd to taro in acid soil:selecting the soil with the total Cd content<0.41 mg·kg^-1,adjusting soil pH above 6.26,and reducing soil DTPA-Cd below 0.19 mg·kg^-1.