广西都安县典型水田硒地球化学特征及影响因素

为发展富硒水稻种植和巩固脱贫成果，在广西都安县百旺镇开展水稻种植区地球化学调查，采集21件岩石和193件水稻根系土-籽实协同调查样品，利用统计学和相关分析方法研究水田土壤硒的分布特征和影响因素.结果表明，百旺镇水田土壤和水稻籽实富硒率分别为67.4%和64.8%，但富硒土壤和富硒水稻籽实样品中镉含量普遍较高；对比显示百旺镇南部种植区水稻籽实富硒率达到61.1%，重金属风险低，发展无污染富硒水稻种植优势明显.相关分析表明次生富集作用是研究区土壤富硒的主要原因，根系土pH和质地不同程度影响土壤硒含量；水稻籽实硒含量主要受根系土硒含量、有效硒含量、pH和Al₂O₃等影响.镉膳食暴露风险评估显示研究区水稻整体安全，但中部区域水稻膳食暴露风险较高.

Selenium Geochemical Characteristics and Influencing Factors of Paddy Fields in Du'an County, Guangxi

This study used 21 rock samples and 193 sets of paddy soil and rice grain samples collected form Baiwang Town, an area of clastic sedimentary rocks in Guangxi, China, to evaluate the potential for selenium-rich agriculture. We analyzed the concentrations of selenium and heavy metals in the soil and rice samples, and discuss the influencing factors by means of statistics and correlation analysis. The results showed that the selenium-rich rate of paddy soil and rice grain in Baiwang Town were 67.4% and 64.8%, respectively, but the content of cadmium in the selenium-rich soil samples was generally higher than the baseline value for China and the background value for Guangxi. In comparison to the screening value of soil pollution risk for agricultural land(GB 15618-2018), the over-standard rate of cadmium was 46.1%, while the over-standard rates of other heavy metals were negligible. The comparison shows that the selenium-rich rate of rice was 61.1% in the southern area of Baiwang Town with a negligible heavy metal content, and the advantages of green selenium-rich rice planting were clear. The correlation analysis showed that secondary enrichment was the main form of selenium enrichment in the study area. The soil pH and texture of the root-zone soil also affected the selenium content of the soil. The selenium content of rice seeds was mainly affected by the selenium content, active selenium content, pH, and aluminum oxide content of the root-zone soil. The risk assessment showed that the level of dietary exposure to cadmium is generally within safe limits, but it is still necessary to strengthen the monitoring of cadmium in rice and control cadmium pollution to reduce the levels of dietary exposure, especially in the central region of Baiwang Town.