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

地下水位波动会影响养分和污染物在土壤、地下水和地表水之间的迁移。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。地下水位的波动将氧气引入浅层地下水，这些氧气可以与有机碳、硝酸盐、铁和锰等具有生态重要性的溶解物质发生反应，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系列时间尺度上随地下水位波动而演变。现场观察、受控实验室柱实验和计算机模型将量化变化的地下水位下的活泼溶质，如氧、硝酸盐、铁和锰的运动。结果将提高我们对地下水和河流水质的动态变化以及对这些重要水资源的管理的了解。该项目还将通过创建实际操作的室外实验室设施和博物馆展览，向广大公民和未来的科学家介绍动态的地表水-地下水相互作用。地下水位波动对河流附近的反应性溶质运移和水质起着重要作用。当地下水位上升时，被困住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。氧气供应的增加刺激了好氧呼吸、硝化-反硝化作用以及地下水中溶解的铁和锰的氧化。水位波动可以传播到几十到几百米的含水层，以响应河流水位的变化。然而，人们对河流附近的反应性交通和水质的影响仍然知之甚少。该项目的总体目标是量化地下水位波动、氧化还原转化和从含水层到河流的溶质输出之间的关系。该项目利用新的传感器技术，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。这项研究中的四个野外站点经历了一系列水位波动，以响应潮汐、风暴和季节。每个地点都有独特的性质，这些性质会影响地下水位附近的反应迁移。然而，这两个地点在气候、岩性、流域规模、土地利用和地貌方面也有共同点。数值流体流动和反应运移模型将量化这些河岸含水层中生物地球化学转化速率和溶质通量的动态。观察结果和模型结果将被综合起来，以产生对动态河岸含水层中地下水位波动对反应溶质迁移的影响的定量理解。该奖项反映了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。

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.