Nano- and Macroscale Physico-chemical Processes Impacting Arsenic Mobilization

含水层管理补给(MAR)是一种具有满足日益增长的用水需求的水回用技术。在3月份，回收的废水被注入含水层以供以后使用。虽然渗流带和地下含水层的过滤和吸附可以去除再生水中的一些污染物，但不利的土壤-水相互作用可能会从含砷含水层中动员砷。这项工作将研究水与含砷黄铁矿(如毒砂/砷黄铁矿)之间的相互作用如何影响MAR期间砷的移动性，并将为研究人员提供新的定量和定性的基础信息，了解氧化还原促进的含砷黄铁矿的溶解机制以及随后与砷的活化和衰减密切相关的氧化铁(氢氧化物)纳米粒子的成核、生长和相变。通过将新的多学科方法与现场观测相结合，包括使用电化学控制的原子力显微镜、小角X射线散射和间歇反应器实验测量，他们将获得定量参数，并更清晰地定性描述矿物-水界面初始氧化铁(Hydr)晶核演化的热力学和动力学。首次将有关成核的新信息纳入到地球化学反应输运模型中，以提高预测精度。实验结果还将与美国环保局位于俄亥俄州辛辛那提的测试和评估设施以及MAR现场的中试柱子实验的可用数据进行比较。研究结果将有助于确定再生水源地的预处理要求，并将为制定更可持续的MAR运行指南提供依据。除这一应用外，所获得的知识还可应用于相关的地球化学系统，包括与地下水普遍存在的砷污染作斗争的地区，以及对纳米级氧化铁(氢氧化物)沉淀物上砷吸附的量化是一个极不确定的来源的环境。拟议的外展计划将为初中生、高中生、本科生和研究生提供教育、研究、公众参与和职业发展机会。它将产生深远的社会影响。此外，将鼓励传统上代表人数不足的学生参加。为了实现这一目标，调查人员将与华盛顿大学学校合作研究所和圣路易斯初中和高中的教师合作，开发一个以水质概念为重点的“热点话题”网站和相关研讨会。为了鼓励高中生和本科生及早参与科学和工程，他们将提供科研项目，并开设水质公开讲座。

Managed aquifer recharge (MAR) is one water reuse technique with the potential to meet growing water demands. In MAR, reclaimed wastewater is injected into aquifer formations for later use. Although filtration and adsorption in the vadose zone and underlying aquifer can remove some contaminants from reclaimed water, unfavorable soil-water interactions can mobilize arsenic from arsenic-bearing aquifer formations. This work will investigate how the interactions between water and arsenic-bearing pyrite, such as arsenopyrite/arsenian pyrite, impact arsenic mobility during MAR, and investigators will provide new quantitative and qualitative fundamental information on the redox-promoted dissolution mechanisms of arsenic-bearing pyrite and the consequent nucleation, growth, and phase transformation of iron (hydr)oxide nanoparticles, which are closely linked with arsenic mobilization and attenuation. By combining novel multidisciplinary approaches and in situ observations, including atomic force microscopy using an electrochemical control, small angle X-ray scattering, and batch reactor experimental measurements, they will obtain quantitative parameters and clearer qualitative descriptions of the thermodynamics and kinetics of initial iron (hydr)oxide nuclei evolution at the mineral-water interface. For the first time, new information on nucleation will be incorporated into geochemical reactive transport models to improve the prediction accuracy. The experimental results will also be compared with available data from pilot-scale column experiments at the U.S. EPA's Test & Evaluation Facility in Cincinnati, OH, and from MAR field sites. The results will help determine pretreatment requirements for reclaimed water sources and will provide a basis for developing more sustainable MAR operation guidelines. Beyond this application, the knowledge gained can be applied to related geochemical systems, including regions struggling with pervasive arsenic contamination of groundwater and environments where quantification of arsenic sorption onto nanoscale iron (hydr)oxide precipitates is a source of great uncertainty. The proposed outreach plan will provide educational, research, public engagement, and professional development opportunities for middle school, high school, undergraduate, and graduate students. It will have far-reaching societal impacts. In addition, the participation of traditionally underrepresented students will be encouraged. To achieve this goal, investigators will develop a "Hot Topics" website and related workshops focused on water quality concepts, in collaboration with Washington University's Institute for School Partnership and teachers from St. Louis' middle and high schools. To encourage high school and undergraduate students' early involvement in science and engineering, they will provide scientific research projects and offer public lectures on water quality.