Selenium (Se), one of the trace elements essential to human body, plays an antagonistic role toward the toxicity of heavy metals. The most important, safe, and feasible way for human body to take Se is to transform Se via food chain. This study collected and analyzed 30 groups of samples of rice seeds and corresponding root soil from the natural high-quality Se-rich farmland that is widely distributed in Libo County. Based on this, this study evaluated the edible safety of rice, studied the selenium content in the rice-root soil system, and investigated the influence of the physical and chemical conditions of soil on rice's absorption and transport of selenium, aiming to provide a scientific basis for the development of Se-rich agriculture in the study area. The results are as follows. Most root soil of rice in the study area is Se-rich, with an average Se content of 0.41×10-6. The rice in the study area has an average w(Se) of 0.030 7×10-6, and green and safe rice accounted for 70%. For the root soil of rice in the study area, there is a significant positive correlation between w(Se) and w(Fe2O3), w(Al2O3), w(MgO), and w(organic matter), and there is associated relationship between w(Se) and some heavy metals including Cr and Cd. There was a significant positive correlation between Se content of rice seeds and that of root soil. By contrast, there is a significant negative correlation between the Se enrichment coefficient of rice and the contents of Se, As, Cd, Cr, Hg, Ni, Al2O3, Fe2O3, and organic matter in root soil. The results indicate that the absorption and fixation of Se by the organic matter and Fe-Al oxides in soil reduce rice's absorption and utilization rate of selenium. The negative correlation between Se enrichment coefficient of rice and the heavy metal contents of root soil suggests that Se may play a certain antagonistic role toward the absorption and transport of heavy metals in the soil-rice system. The study area is rich in Se-rich farmland resources, yet there is a risk that the contents of Cr and Cd in rice slightly exceeds relevant standards. Therefore, it is necessary to pay attention to the ecological effects of heavy metal elements in the development of Se-rich agriculture in the study area.
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