Nano- and Macroscale Physico-chemical Processes Impacting Arsenic Mobilization

含水层管理补给（MAR）是一种有潜力满足日益增长的水需求的水再利用技术。在MAR中，回收的废水被注入含水层以备后用。虽然渗流带和下层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-水相互作用可以从含砷含水层中动员砷。这项工作将研究水和含砷黄铁矿之间的相互作用，如毒砂/砷黄铁矿，如何影响MAR过程中砷的流动性，研究人员将提供新的定量和定性的基本信息含砷黄铁矿的氧化还原促进溶解机制和随之而来的成核，生长和铁（氢）氧化物纳米颗粒的相变，这与砷的迁移和衰减密切相关。通过结合新的多学科方法和原位观察，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和更清晰的定性描述初始铁（氢）氧化物核在矿物-水界面演化的热力学和动力学。首次将成核作用的新信息纳入地球化学反应输运模型，以提高预测精度。实验结果还将与美国环保署在俄亥俄州辛辛那提的试验评估设施进行的中试规模柱实验和MAR现场的可用数据进行比较。研究结果将有助于确定再生水源的预处理要求，并为制定更可持续的MAR操作指南提供依据。除此之外，所获得的知识可以应用于相关的地球化学系统，包括与地下水和环境中普遍存在的砷污染作斗争的地区，在这些地区，砷吸附到纳米级氧化铁（氢）沉淀物上的定量是一个很大的不确定性的来源。拟议的外展计划将为初中、高中、本科和研究生提供教育、研究、公众参与和专业发展机会。它将产生深远的社会影响。此外，将鼓励历来代表性不足的学生参加。为了实现这一目标，调查人员将与华盛顿大学的学校伙伴关系研究所和圣路易斯初中和高中的教师合作，开发一个“热门话题”网站和有关的水质概念研讨会。为了鼓励高中生和本科生早期参与科学和工程，他们将提供科学研究项目，并提供关于水质的公开讲座。

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.