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，但水稻的产量和品质受到从土壤中吸收砷和镉的威胁。水稻在常规土壤淹水条件下生长时会吸收和浓缩砷，因为砷是通过土壤中的生物地球化学反应释放到水中的。即使在土壤砷浓度较低的情况下，这一过程也会发生。虽然减少土壤淹水可以减少水稻的砷污染，甚至节约水资源，但这样做可以增加水稻对土壤中镉的吸收。这项研究项目的目标是开发同时限制水稻对砷和镉的吸收的方法。与镉或砷相比，锰(II)对植物的毒性较小，最近被证明与镉具有共同的根运输途径。因此，应该有可能利用锰的地球化学性质，通过工程土壤电化学来减少植物对镉的吸收。这项研究项目采用了多学科的方法，结合了地球化学和植物生物学的方法，并将利用美国国家科学基金会资助的水稻调查、传播和教育(水稻)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重大挑战。对高中的更多外展努力将提高学生的科学素养，希望他们对STEM职业感兴趣。大米通常是婴儿消费的第一食物，也是全球一半人口的主食。然而，水稻种植过程中土壤淹水过程中对有毒砷和镉的吸收威胁着水稻的产量和品质。虽然在过去的二十年里，人们对砷的循环进行了很好的研究，但对水稻对镉的循环和吸收的了解较少。这项研究项目背后的假设是，控制锰(II)的有效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。该项目的具体目标是1)了解在简单的水培系统中增加锰(II)的有效性在减少水稻对镉的吸收中的作用；2)评估基因工程氧化还原状态对水稻中金属(Loid)S的溶解、植物吸收和定位的影响；3)比较传统的氧化还原方法和土壤还原指示物的新技术。虹膜技术将被评估为一种低成本的手段，让农民知道何时排水，以限制水稻吸收有毒金属。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防止有毒金属吸收的能力，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，因为许多植物也积累镉。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势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.