Collaborative Research: Changes in river-aquifer exchange induced by groundwater pumping, and their effect on arsenic contamination in the Red River Delta, Vietnam

摘要世界上至少有20亿人，其中包括大约4000万美国人，使用家庭水井作为饮用水。地下水的质量可能对人类健康产生重大影响，但我们对广泛抽取地下水（主要用于农业和城市供水）如何影响地下水质量知之甚少。该项目研究地下水抽取对受砷（一种天然致癌物）影响的含水层系统水质可持续性的影响。在南亚和东南亚，广泛的抽水影响了地下水中砷污染的空间范围和浓度。这个实地项目研究水文变化如何影响含水层的生物地球化学，进而影响地下水中的砷含量。具体而言，该项目调查了越南城市用水如何改变含水层水文和调动砷的河流-地下水相互作用。这项研究的结果将提供一般性的见解，从而更有效地管理其他环境中受自然发生的污染物影响的地下水资源。研究活动将包括来自哥伦比亚大学、巴纳德学院和麻省理工学院的本科生和研究生，以及纽约市贫困高中的学生。在越南北部，红河西岸地下水流动的逆转是由为河内市抽取地下水引起的。这种水流逆转将高砷的地下水从灰色的全新世含水层引入相邻的低砷橙色更新世含水层，而橙色更新世砂则随着铁氧氢氧化物被平流溶解的有机碳（DOC）还原而变成灰色。该项目研究了抽水如何影响河岸含水层补给的来源和组成，在那里可获得不稳定的砷，新沉积的沉积物释放出高水平的DOC。为了量化城市抽水的影响，将受抽水影响的红河西岸含水层的水文和生物地球化学与不受抽水影响的东岸含水层进行比较。这项对照研究量化了人为扰动对地下水和含水层沉积物化学成分的影响程度。

Collaborative Research: Changes in river-aquifer exchange induced by groundwater pumping and their effect on arsenic contamination in the Red River Delta, VietnamAbstractAt least two billion people in the world, including an estimated 40 million in the United States, use domestic wells for potable drinking water. The quality of this groundwater can have a large impact on human health, yet we know little about how extensive groundwater pumping, primarily for agricultural and urban water supplies, impacts groundwater quality. This project studies the effect of groundwater pumping on the sustainability of water quality in aquifer systems affected by arsenic, a naturally occurring carcinogen. In South and Southeast Asia, extensive pumping has influenced the spatial extent and concentration of arsenic contamination in groundwater. This field-based project examines how hydrological changes impact the biogeochemistry of aquifers and, subsequently, the arsenic levels in groundwater. Specifically, this project investigates how urban water use in Vietnam is changing aquifer hydrology and river-groundwater interactions that mobilize arsenic. The results of this study will provide generalizable insights leading to more effective management of groundwater resources impacted by naturally occurring contaminants in other settings. The research activities will involve undergraduate and graduate students from Columbia University, Barnard College, and Massachusetts Institute of Technology and engage underprivileged high school students in New York City. In northern Vietnam, the reversal of groundwater flow along the western bank of the Red River has been induced by groundwater pumping for the city of Hanoi. This flow reversal draws high-As groundwater from a gray Holocene aquifer into an adjacent low arsenic, orange Pleistocene aquifer, and the orange Pleistocene sands are turning gray as iron oxyhydroxides are reduced by advected dissolved organic carbon (DOC). This project examines how pumping influences the source and composition of aquifer recharge at the riverbank, where labile arsenic is available and high levels of DOC are released by freshly deposited sediments. To quantify the impact of urban pumping, the hydrology and biogeochemistry of the western bank aquifers of the Red River influenced by pumping are compared to the eastern bank aquifers that are insulated from the effects of pumping. This controlled study quantifies the extent to which human perturbations have affected the chemical composition of groundwater and aquifer sediments.