酸性土壤改良对土壤镉形态改变及树仔菜镉含量的影响

Impact of acid soil improvement on form transformation of cadmium in soils and cadmium content in Sauropus androgynus(L.)Merr.

【目的】镉(Cd)是有毒重金属元素,是农产品质量安全的质量控制指标。研究酸性土壤改良肥对土壤Cd形态转化及树仔菜中Cd含量的影响,为栽培低镉优质树仔菜提供科学依据。【方法】以液态酸性土壤改良肥对树仔菜种植试验区土壤进行改良处理,用原子吸收技术在试验过程中定期监测试验区和对照区土壤镉离子(Cd2+)形态含量及树仔菜样品中的Cd含量,并对其变化规律进行分析。【结果】施用液态酸性土壤改良肥后,试验区土壤p H由酸性调节至弱酸性,Cd的水溶态、离子交换态、碳酸盐结合态、铁锰氧化物结合态、有机结合态和总有效态等含量均显著低于对照区(P<0.05),而残渣态约是对照区的3倍;对照区和试验区土壤有效态Cd含量分别为0.066和0.023 mg/kg,试验区树仔菜样品中的Cd含量极显著低于对照区(P<0.01),且符合无公害蔬菜安全标准限量值(0.05 mg/kg)要求。【结论】液态酸性土壤改良肥可有效提高土壤p H,降低土壤中Cd2+活性,提高树仔菜的品质,达到无公害蔬菜安全标准要求。

【Objective】Cadmium（Cd） is a toxic heavy metal element and a control index of quality and safety for agricultural products. The effects of acid soil improvement fertilizer on soil Cd form transformation and Cd content in Sauropus androgynus（L.）Merr. were studied to provide scientific basis for cultivation of high quality S. androgynus with low Cd.【Method】The liquid acidic soil improvement fertilizer was used to make meliorative treatment on the soil in S. androgynus planting test area,then the content of Cd in ion morphology（Cd2＋）in S. androgynus in the experimental plot and control plot were monitored regularly during the experiment process by atomic absorption technique,and the change rule was also analyzed.【Result】After the treatment of liquid acidic soil improvement fertilizer,the pH value of soil in the experiment plot increased from acidic to weakly acidic,the content of water-soluble state,ion-exchangeable state,carbonate state,and the binding sate of iron-manganese oxide,the organic binding state and the total available state of the Cd were significantly lower than those of the control plot（P〈0.05）,while the Cd content of residual state was as three times as that of control. The available state of Cd in the control plot as and experimental plot were 0.066 and 0.023 mg/kg respectively. The Cd content of S. androgynus sample in the experimental plot was extremely significantly lower than that of the control（P〈0.01）,meeting the limiting value of safety standard for pollution-free vegetables（0.05 mg/kg）.【Conclusion】The liquid acidic soil improvement fertilizer not only effectively improves pH value of the soil,but also reduces Cd2＋ ironic activity in the soil. Consequently,it can improve the quality of S.androgynus and meet the requirements of pollution-free vegetables.