成都平原东北部高地质背景下水稻土镉生物有效性及稻米中镉积累的影响因素

Effectiveness of Cadmium Bioavailability in Paddy Soil and Effective Factors of Cadmium Accumulation in Rice in the High Geological Background of Northeast Chengdu Plain

在运积型高镉地质背景土壤中,土壤镉的生物有效性与稻米中镉含量高度相关。在成都平原东北部绵竹地区高镉运积型酸性水稻土分布区采集了20组土壤和稻米样品,研究土壤中镉生物有效性和镉在稻米中积累的影响因素。结果表明:土壤中总镉含量为0.36~0.78 mg/kg,其含量与土壤中的钙、铁含量呈显著正相关(R^(2)>0.96,P<0.05),表明镉和钙、铁元素来源于相同的物源区。土壤镉的活性比(AR)、生物富集系数(BCF)与土壤pH值呈显著负相关(R^(2)>0.75,P<0.05),土壤中的钙和pH值之间具有显著的正相关关系(R^(2)=0.86,P<0.05),因此土壤pH值与土壤钙是水稻土镉生物有效性和稻米中镉积累最主要的影响因素。建立了土壤中镉和稻米中镉的耦合模型,预估了控制稻米中镉含量满足国标限值0.2 mg/kg的土壤中镉的阈值。成都平原东北部高地质背景水稻土种植的稻米镉含量超标的风险较高,需进行土壤重金属污染修复治理。

In the soil of transport-accumulation under the high cadmium geological background,cadmium bioavailability in soil is highly correlated with cadmium content in rice.20 groups of soil and rice samples were collected in the distribution area of acidic paddy soil of high cadmium transport-accumulation in Mianzhu area in northeast Chengdu Plain to study the bioavailability of cadmium in soil and the effective factors of cadmium accumulation in rice.The results show that when the content of total cadmium in soil is 0.36-0.78 mg/kg,there is a significant positive correlation with the content of calcium and iron in soil(R^(2)>0.96,P<0.05),indicating that cadmium,calcium and iron come from the same provenance area.The activity ratio(AR)of cadmium in soil and bioconcentration factor(BCF)were significantly negatively correlated with soil pH(R^(2)>0.75,P<0.05),and there is a significant positive correlation between calcium in soil and pH(R^(2)=0.86,P<0.05).Therefore,soil pH and calcium in soil are the most main influencing factors of cadmium bioavailability in paddy soil and cadmium accumulation in rice.On this basis,the coupling relationship between cadmium in soil and cadmium in rice is established,and the threshold value of cadmium in soil where the cadmium content in rice is controlled to be within the national limit of 0.2 mg/kg is estimated.The risk of exceeding the standard of cadmium content in rice,which is planted in the paddy soil of high geological background of northeast Chengdu Plain,is high.It is urgent to carry out remediation and treatment of soil heavy metal pollution.