重金属高背景区水稻镉积累与健康安全风险评价：以云南省会泽县娜姑镇为例

调查发现，重金属高背景区存在土壤中的镉含量超标，而农作物中的镉含量并未超标的现象，但对其原因知之甚少。开展区内农作物镉积累研究并探寻制约农作物镉吸收的因素，对土壤环境质量评价和污染土地生态修复都具有重要意义。以云南省会泽县娜姑镇娜姑坝子为研究区，采集了水稻籽实和配套土壤样品各41件，采用ICP-MS方法检测了Cd含量。通过偏相关、R型聚类、逐步线性回归等分析了水稻镉与土壤元素（指标）之间的相关关系。结果显示，水田土壤镉（Cd）含量为 0.467~1.87 mg/kg，平均为 0.78 mg/kg，是全国土壤背景值的 5.69 倍，58.5% 的样品超过农用地土壤污染风险筛选值。水稻（糙米）镉含量为 0.007~0.062 mg/kg，平均 0.016 mg/kg，均低于食品安全国家标准限值。水稻镉与土壤铀（U）、钼（Mo）等呈显著正相关，与土壤有机碳（TOC）、硫（S）等呈显著负相关，与土壤 Cd 总量和酸碱度（pH）无显著相关性。土壤镉超标而水稻镉不超标的现象可能与土壤富含有机碳有关，该地区土壤有机碳（TOC）含量达全国背景值的5.57倍。当 TOC > 3% 时，水稻镉含量迅速下降。据此提出土壤镉环境等级的有机碳修正方法，将研究区3.42 km2（5129 亩）Ⅱ等水田修正为Ⅰ等。此外，还提出了一些土壤养护和修复的建议。

Cd accumulation and human health risk assessment of rice in high background areas of heavy metals: A case study of Nagu Town,Huize County,Yunnan Province

A study comparing cadmium (Cd) accumulation in soil and rice in an area of high background heavy metal concentrations in Huize County, Yunnan, showed that, occasionally, the cadmium content in soil exceeds the standard, whereas the cadmium content in crops remains within the standard. However, our understanding of the reasons for this phenomenon is limited. It is of great significance for soil environmental quality evaluation and ecological restoration to study cadmium accumulation in crops and its control factors in these areas. In this study, 41 rice seed samples and 41 corresponding soil samples were collected from the Nagubazi, Nagu Town, Huize County, Yunnan Province, and their cadmium content was determined by ICP-MS. The correlation between rice cadmium and soil elements (indices) was analyzed by partial correlation, R-type clustering, and stepwise linear regression. The results showed that the soil cadmium content ranged from 0.467 to 1.87 mg/kg, with an average of 0.78 mg/kg, which is 5.69 times that of the national soil background value. Moreover, 58.5% of the soil samples exceeded the soil pollution risk threshold for agricultural land. In contrast, the cadmium content of rice (brown rice) ranged from 0.007 to 0.062 mg/kg, with an average of 0.016 mg/kg, which is lower than the national threshold for food safety.The content of cadmium in rice was significantly positively correlated with the content of U and Mo , and significantly negatively correlated with soil organic carbon (TOC) and the content of S in soil, but not significantly correlated with soil cadmium content and pH value. The phenomenon that soil cadmium exceeds the standard but rice cadmium does not exceed the standard may be related to the enrichment of organic matter in the soil. The content of soil TOC is 5.57 times that of the national background value. When TOC is greater than 3%, cadmium content in rice decreases rapidly. Therefore, the organic matter correction method for soil cadmium environmental grade evaluation was proposed, and the 3.42 km2 (5129 Mu) of paddy field originally classified as Class Ⅱ in the study area was revised to Class Ⅰ. In addition, some suggestions on soil protection and remediation were put forward.