Fate of Cadmium and Arsenic Under Engineered Physico-Chemical Gradients in the Soil-Water-Rice Nexus

大米是世界上一半人口的主食。 尽管其重要性，水稻的产量和质量受到土壤中砷和镉吸收的威胁。 水稻在常规土壤淹水条件下生长时会吸收并富集砷，因为砷会通过土壤中的生物化学反应释放到水中。 即使土壤砷浓度很低，也会发生这种过程。 虽然尽量减少土壤淹水可以减少水稻的砷污染，甚至节省水资源，但这样做会增加水稻从土壤中吸收镉。 该研究项目的目标是开发同时限制水稻吸收砷和镉的方法。 锰（II）对植物的毒性低于镉或砷，最近已被证明与镉共享根运输途径。 因此，应该有可能利用锰的地球化学特性，通过工程土壤电化学来减少植物对镉的吸收。 该研究项目采用多学科方法，结合了地球化学和植物生物学方法，并将利用NSF资助的水稻调查，交流和教育（RICE）设施的资源。这项工作将有助于培训和促进下一代STEM专业人员的专业发展，以应对可持续粮食供应的巨大挑战。 对高中的额外推广工作将提高学生的科学素养，并希望他们对STEM职业感兴趣。大米通常是婴儿食用的第一种食物，也是全球一半人口的主食。 然而，在水稻种植过程中，土壤淹水过程中有毒的砷和镉的吸收威胁着水稻的产量和品质。 尽管在过去的二十年里砷的循环已经得到了很好的研究，但镉的循环和水稻的吸收还不太清楚。 该研究项目背后的假设是，控制锰（II）的可用性可以提供一种工程解决方案，以限制水稻对镉和砷的吸收。 本项目的具体目标是：1）了解在简单水培系统中增加锰（II）的有效性在降低水稻对镉吸收中的作用; 2）评估在水稻围隔生态系统中，工程化氧化还原状态对金属（类）（包括锰、铁、镉和砷）在水稻中的溶解、植物吸收和定位的影响;和3）比较传统的氧化还原测量的土壤（IRIS）膜的还原指标的量化新技术。 IRIS薄膜技术将被评估为一种低成本的手段，使农民知道何时排水，以限制水稻吸收有毒的类金属。 这项研究的成果将改变水稻农学家，湿地科学家，农民和其他利益相关者的能力，以防止有毒金属的吸收，从而保障数十亿人的粮食供应。 这项研究的结果应该适用于水稻以外的许多其他植物，因为许多植物也会积累镉。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Rice is a staple food for half the world's population. Despite its importance, the yield and quality of rice are threatened by arsenic and cadmium uptake from soil. Rice will uptake and concentrate arsenic when it is grown under conventional soil flooding, because arsenic is released into the water from biogeochemical reactions in the soil. This process can happen even when soil arsenic concentrations are low. Although minimizing soil flooding can decrease arsenic contamination of rice and even save water resources, doing so can increase rice grain uptake of cadmium from the soil. The goal of this research project is to develop methods that simultaneously limit rice uptake of both arsenic and cadmium. Manganese(II) is less toxic to plants than cadmium or arsenic and has been recently shown to share a root transport pathway with cadmium. Therefore, it should be possible to exploit the geochemical characteristics of manganese to decrease uptake of cadmium into the plant via engineered soil electrochemistry. This research project takes a multidisciplinary approach that incorporates geochemistry and plant biology methods and also will utilize resources at the NSF-funded Rice Investigation, Communication, and Education (RICE) Facility. This work will help train and foster the professional development of the next generation of STEM professionals to tackle the grand challenge of a sustainable food supply. Additional outreach efforts to high schools will increase scientific literacy of students and hopefully interest them in STEM careers.Rice is often the first food consumed by infants and is also a staple food for half of the global population. However, the yield and quality of rice are threatened by the uptake of toxic arsenic and cadmium during the soil flooding process integral to rice cultivation. Although arsenic cycling has been well studied over the last two decades, cadmium cycling and uptake by rice is less well understood. The hypothesis behind this research project is that controlling manganese(II) availability can provide an engineered solution to limit cadmium and arsenic uptake by rice. The specific objectives of this project are 1) to understand the role of increasing manganese(II) availability in decreasing cadmium uptake by rice in simple hydroponic systems; 2) to evaluate the impact of engineered redox states on dissolution, plant uptake, and localization of metal(loid)s including manganese, iron, cadmium, and arsenic, in rice plants grown in rice paddy mesocosms; and 3) to compare traditional redox measurements to novel techniques for quantifying indicators of reduction in soil (IRIS) films. IRIS film technology will be evaluated as a low-cost means for farmers to know when to drain their fields in order to restrict rice uptake of toxic metalloids. The outcomes of this research will transform the ability of rice agronomists, wetland scientists, farmers, and other stakeholders to prevent toxic metal uptake and thereby safeguard the food supply of billions of people. The results of this study should be applicable to many other plants beyond rice, because many plants also accumulate cadmium.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.