Resolving time scales of groundwater flow and saline water displacement using noble gas radionuclide tracers

使用惰性气体放射性核素示踪剂解析地下水流和盐水置换的时间尺度

• 批准号: 2114036
• 负责人: Andrew Davis
• 金额: $ 27.25万
• 依托单位: University of Chicago
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2021
• 资助国家: 美国
• 起止时间: 2021-08-01 至 2024-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2114036&HistoricalAwards=false
• 关键词: Resolving; time; scales; groundwater; flow

Groundwater is one of the largest freshwater resources on Earth, providing 40% of drinking water to the global population. It is stored in the pores of subsurface rocks and flows slowly. As the chemical composition of incoming water changes, the porewater composition also changes, the rate of which depends on the pore sizes. Smaller pores tend to retain the older water for a longer time, but the rate of this process is generally slow and difficult to quantify, which makes remediation of contaminated groundwater difficult. This project will determine the rate of change by collecting groundwater samples from the Milk River Aquifer in Canada and analyzing the chemical and isotopic compositions including novel radioisotopes. A graduate student will receive extensive training in various hydrological methods. An Odyssey & Empower scholar (a program for honors undergraduate students from under-resourced backgrounds) will be trained and acquire research experience in state-of-the art techniques. Project outcomes will have long-term impacts on estimations of sustainable yields from this aquifer, which serves as one of the most valuable freshwater resources in the region straddling northern Montana and southern Alberta.The ‘dynamic storage’ of solutes in small pores acts as a source to advective flow and impacts the quality of groundwater over the long term. Using the Milk River Aquifer as a natural laboratory, this project will apply 81Kr along with other geochemical tracers to determine the time scale of the advective flow. The goal is to deduce the rates of solute displacement, diffusion, and dispersion by establishing an integrated geochemical model. The proposed project will also have two important technical implications: (i) determining the secular variation of the input 36Cl/Cl ratios with varying climates and (ii) establishing the feasibility of using 39Ar/40Ar* ratios as a chronometer of old (much great than 1000 years in age) groundwater.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.

地下水是地球上最大的淡水资源之一，为全球人口提供40%的饮用水。它储存在地下岩石的孔隙中，流动缓慢。随着来水的化学成分发生变化，孔隙水的组成也会发生变化，变化的速度取决于孔隙的大小。较小的孔隙往往会将较老的水保留更长时间，但这一过程的速度通常很慢，很难量化，这使得修复受污染的地下水变得困难。该项目将通过收集加拿大Milk River含水层的地下水样本并分析化学和同位素组成，包括新的放射性同位素，来确定变化的速度。研究生将接受各种水文方法的广泛培训。一名奥德赛与赋能奖学金获得者将接受培训，并获得最先进技术方面的研究经验。项目成果将对该含水层可持续产量的估计产生长期影响，该含水层是蒙大拿州北部和阿尔伯塔省南部地区最有价值的淡水资源之一。在小孔隙中动态储存溶质是平流流的来源，并长期影响地下水质量。利用牛奶河含水层作为天然实验室，该项目将应用81Kr和其他地球化学示踪剂来确定平流流的时间尺度。其目的是通过建立一个综合的地球化学模型来推导出溶质置换、扩散和扩散的速率。拟议的项目还将有两个重要的技术影响：(I)确定输入的36Cl/Cl值在不同气候下的长期变化，以及(Ii)确定使用39Ar/40Ar*值作为古老(远远大于1000年)地下水的计时器的可行性。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。