重庆市郊稻米Cd风险的原位钝化削减

为筛选适合应用于重庆市郊区稻田土壤及农作物Cd污染的修复技术，采用田间小区原位钝化实验和重金属来源加密监测相结合的方法，比较了石灰、腐殖酸、硅酸钾3种常见修复剂对Cd污染稻田的土壤基本理化性质、水稻各部位Cd富集量、稻米产量和稻米品质的影响。结果表明，该区域土壤Cd污染的主要原因为该区域土壤Cd本底值含量高且土壤酸化严重。在土壤全Cd为0.66 mg·kg-1，有效Cd为0.39 mg·kg-1的污染程度下，施用3种修复剂均可显著降低土壤有效Cd和稻米中Cd含量。其中，施用腐殖酸可显著提高土壤有机质含量，收获期种植2种水稻的土壤中有效Cd含量比CK处理分别减少了32.1%和34.8%，稻米中Cd含量比CK处理分别较少了53.3%和48.2%，同时低于国家食品污染物限量标准 0.2 mg·kg -1，其作用机理主要通过提高土壤有机质含量，降低水稻根系对土壤中Cd的富集量及向茎叶部Cd的运输量。同时，相比于其他修复剂，施加腐殖酸可降低稻米直链淀粉含量，提升稻米品质，但会降低稻米产量。施用石灰可显著提高土壤pH和稻米产量，但水稻收割后稻米中Cd含量高于腐殖酸处理，低于硅酸钾处理。

In-situ passivation in Cd polluted paddy fields of Chongqing suburb for rice healthy control

To select the remediation technologies suitable for Cd polluted paddy fields and crops in Chongqing suburb, the field plot experiments and dense monitoring for heavy metal sources were conducted. The effects of three kinds of common remediation agents of lime, humic acid and potassium silicate on the basic physical and chemical properties of soil, cadmium enrichment in various parts of rice, rice yield and rice quality were compared. The results showed that the main reasons for Cd pollution in this field were high soil background value of cadmium and serious soil acidification. For the polluted soil with total Cd concentration of 0.66 mg·kg-1, and available Cd concentration of 0.39 mg·kg-1, the addition of above three remediation agents could effectively reduce the available Cd in soil and total Cd in rice. In detail, humic acid addition could significantly improve the soil organic matter content, In comparison with CK treatment, the available Cd contents in soil with two kinds of harvest rice were reduced 32.1% and 34.8%, respectively, and total Cd contents in these harvest rice were reduced 53.3% and 48.2%, respectively, which are lower than the national standard limit of 0.2 mg·kg-1 for food contaminant. The corresponding mechanism could be suggested that humic acid addition promotes the content of organic matter in soil, reduce the Cd accumulation in rice root system from soil and Cd transport to stems and leaves. Meanwhile, humic acid addition also reduced the amylose content in rice and improved the rice quality, but cut the rice yield. Besides, lime addition can significantly raise the pH value of soil and rice yield, but the Cd content in harvest rice was higher than humic acid treatment, lower than potassium silicate treatment.