CAREER: Dynamic water table controls on reactive solute transport near the groundwater-surface water interface

地下水位的波动影响养分和污染物在土壤、地下水和地表水之间的运输。地下水位在短时间和长时间内上下移动，特别是在河流附近。地下水位波动将氧气引入浅层地下水，它可以与生态上重要的溶解物质如有机碳、硝酸盐、铁和锰发生反应，并对砷等污染物产生级联效应。该项目旨在了解地下水化学如何在一定时间尺度上响应地下水位波动而演变。野外观察、受控的实验室柱实验和计算机模型将量化在波动的地下水位下活性溶质（如氧、硝酸盐、铁和锰）的运动。研究结果将提高我们对地下水和河流水质动态变化以及这些重要水资源管理的理解。该项目还将通过创建一个动手户外实验室设施和博物馆展览，向广大市民和未来的科学家介绍地表水与地下水的动态相互作用。地下水位波动对反应性溶质运移和河流水质有重要影响。当地下水位上升时，被困的土壤空气与周围的孔隙水交换氧气，当地下水位下降时，孔隙水向下流动。氧气供应的增加促进了好氧呼吸、硝化-反硝化作用以及地下水中溶解的铁和锰的氧化。地下水位的波动可以随着河段的变化向地下含水层传播几十到几百米。然而，对河流附近的反应性运输和水质的影响仍然知之甚少。该项目的首要目标是量化地下水位波动、氧化还原转化和溶质从含水层向河流的出口之间的关系。本项目利用新型传感器技术，在控制柱实验和天然河岸含水层中观察地下水位波动对地下水化学的影响。本研究中的四个野外站点经历了一系列的地下水位波动，以响应潮汐、风暴和季节。每个地点都有影响地下水位附近反应性输运的独特性质。然而，成对的地点在气候、岩性、流域规模、土地利用和地貌等方面也有共性。数值流体流动和反应输运模型将量化这些河岸含水层的生物地球化学转化速率和溶质通量的动力学。将综合观测结果和模式结果，以定量了解地下水位波动对动态河岸含水层中反应性溶质输送的影响。该奖项反映了美国国家科学基金会的法定使命，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。

Water table fluctuations influence the transport of nutrients and contaminants between soils, groundwater, and surface water. The water table moves up and down over short and long timespans, particularly near rivers. Water table fluctuations introduce oxygen to shallow groundwater, which can react with ecologically important dissolved substances like organic carbon, nitrate, iron and manganese and have cascading effects on contaminants like arsenic. This project aims to understand how groundwater chemistry evolves in response to water table fluctuations over a range of timescales. Field observations, controlled laboratory column experiments, and computer models will quantify the movement of reactive solutes such as oxygen, nitrate, iron, and manganese beneath a fluctuating water table. Results will improve our understanding of dynamic changes in both groundwater and river water quality and the management of these vital water resources. This project will also introduce a broad audience of citizens and future scientists to dynamic surface water-groundwater interactions through the creation of a hands-on outdoor laboratory facility and museum exhibit. Water table fluctuations play an important role in reactive solute transport and water quality near rivers. When the water table rises, entrapped soil air exchanges oxygen with surrounding pore water, which travels downward when the water table falls. The enhanced supply of oxygen stimulates aerobic respiration, nitrification-denitrification, and oxidation of dissolved iron and manganese in groundwater. Water table fluctuations can propagate tens to hundreds of meters into an aquifer in response to changes in river stage. Yet the implications for reactive transport and water quality near rivers remain poorly understood. The overarching goal of this project is to quantify relationships between water table fluctuations, redox transformations, and solute export from aquifers to rivers. This project leverages novel sensor technology to observe the effects of water table fluctuations on groundwater chemistry in controlled column experiments and natural riparian aquifers. The four field sites in this study experience a range of water table fluctuations in response to tides, storms, and seasons. Each site has unique properties that influence reactive transport near the water table. However, pairs of sites also have commonalities in climate, lithology, catchment scale, land use, and geomorphology. Numerical fluid flow and reactive transport models will quantify dynamics in biogeochemical transformation rates and solute fluxes in these riparian aquifers. Observations and model results will be synthesized to generate a quantitative understanding of the effects of water table fluctuations on reactive solute transport in dynamic riparian aquifers.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.