毕节岩溶区坡耕地烟草镉安全评价研究

以贵州省毕节地区岩溶环境烟水配套工程为例,通过实地调查和采样,对烟草地土壤-烟草系统镉进行评价。结果表明,烟草地土壤镉含量0.12~0.67 mg.kg-1,平均0.40 mg.kg-1,已遭轻度-中度污染。水溶态、离子交换态、碳酸盐结合态、腐植酸态、铁锰氧化物结合态、强有机结合态和残渣态镉分别为0.024、0.100、0.033、0.067、0.096、0.019 mg.kg-1和0.016 mg.kg-1,其中离子交换态、铁锰结合态和腐植酸态占66%。全镉与水溶态、离子交换态和铁锰结合态,水溶态与离子交换态和碳酸盐结合态,离子交换态与铁锰氧化物结合态显著正相关,揭示了镉形态间的转化关系及其对烟草的潜在影响。烟株上部烟叶镉含量1.04～1.59 mg.kg-1,茎、根中镉残留量为0.2～1.4 mg.kg-1,可能与源自K326的主推和示范品种对镉的提取效率高有关。因此,建议采用吸收镉低的烟草品种和合理的差异性水肥管理措施,固定土壤中活性态镉,降低土壤镉向烟株的转移,以保障烟叶品质,同时妥善处理这些农业废弃物以保护环境。

Evaluation on Cadmium Safety of Tobacco Planted in Slope Farmland of Karst Area in Bijie Prefecture of Guizhou,China

Karst environment is rich in interior cadmium which may influence the cadmium level in tobacco species.The cadmium from soil-tobacco system in karst area of Bijie prefecture of Guizhou Province was evaluated by sampling and analyzing with a case of water-tobacco project.The results showed that the content of soil cadmium from tobacco farmlands averaged 0.4 mg·kg-1,ranging from 0.12 to 0.67 mg·kg-1,so the soil had been mildly to moderately polluted by cadmium.The water-soluble,the ion-exchangeable,the carbonate-bound,the humic acid-bound,the Fe-Mn oxide-bound,the organic matter-strongly bound and the residual of cadmium were 0.024,0.100,0.033,0.067,0.096,0.019 mg·kg-1 and 0.016 mg·kg-1 respectively,the sum of the ion-exchangeable,the Fe-Mn oxide-bound and the humic acid-bound being up to 66% of total cadmium.Evidently present were positive correlations among the water-soluble,the ion-exchangeable,the Fe-Mn oxide-bound and the total cadmium,among the water-soluble,the ion-exchangeable and the carbonate-bound,between the ion-exchangeable and the Fe-Mn oxide-bound,which pointed out the transformation of cadmium speciations and potential effects on tobacco under cultivated conditions.Top leaves were of 1.04~1.59 mg·kg-1 cadmium and 0.2~1.4 mg·kg-1 of cadmium remained in stalks and roots of tobacco,which might be related to high extraction efficiency of cadmium by those tobacco species originating from K326,which hand been promoting and demonstrating in this area.To fix available form of soil cadmium and decrease the transformation of soil cadmium into tobacco organs,some suggestions are to use the tobacco species of lower cadmium absorption,differential management of fertilizers and water applied to tobacco lands so as to harvest good quality of tobacco leaves.Meanwhile,abandoned tobacco stalks and roots need to be disposed properly to protect the environment from cadmium pollution.