Collaborative Research: Geophysical characterization of a karst aquifer using dynamic recharge events

合作研究：利用动态补给事件对岩溶含水层进行地球物理表征

• 批准号: 1740481
• 负责人: Jonathan Martin
• 金额: $ 3.34万
• 依托单位: University of Florida
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2018
• 资助国家: 美国
• 起止时间: 2018-04-01 至 2022-03-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1740481&HistoricalAwards=false
• 关键词: Collaborative; Research; Geophysical; characterization; karst

Karst aquifers are important water resources, providing water for up to a quarter of the world?s population. These aquifers are complex hydrogeologic systems, where flow and transport predominantly occur through preferential flow paths or conduits that range in size from cm-scale openings to passages much larger than required for human access (caves). Despite their hydrologic importance, the location of karst conduits and characteristics of the larger aquifer are typically poorly constrained. To address these problems, we will monitor recharge-induced responses that arise as water flows into the subsurface in a karst aquifer in Florida using geophysical instrumentation to characterize the conduits, subsurface flow, and the larger karst system. The noninvasive remote sensing investigation will generate knowledge for direct societal benefit, including tools to improve the creation of karst hazards maps that highlight areas susceptible to sinkhole formation, the identification of preferential flow paths relevant to contaminant transport, and the development of a methodology to determine subsurface flow for water supply considerations. We will develop a temporary, interactive traveling exhibit in collaboration with the National Cave and Karst Research Institute that will frequent visitor centers near the field site in Florida and in New Mexico to increase public engagement and scientific literacy about karst hydrogeology and environmental seismology. The project will also contribute to the education of the next generation of the scientific workforce through the involvement of two graduate students at New Mexico Tech, an undergraduate student at the University of Florida, two undergraduate student interns through the IRIS undergraduate student intern program, and two early career scientists and a mid-career female scientist in an EPSCoR state. Finally, collected datasets will be incorporated into lecture material and homework sets of undergraduate and graduate courses at New Mexico Tech, which is a Hispanic-serving institution.A previous pilot study demonstrated the generation of seismic signals during artificial recharge experiments and a natural recharge event in a karst aquifer. These and other geophysical signals are caused by processes during flow through karst aquifers and includes pressure pulses generated as recharge enters conduits with full pipe flow, pore pressure changes in fractures and the rock matrix, mass loading induced subsidence due to changes in water mass, and turbulent interaction of flow with the wall rocks. To capitalize on the information content provided by these signals, we will use simultaneous, large-scale observations of recharge events at two co-located geophysical sensor networks to characterize the conduit network, flow processes within this network, and material properties of the larger karst system. Seismometers, tiltmeters, and other instruments will be deployed at the Santa Fe River Sink-Rise system in Florida to observe karst recharge events over a two-year period. This field site has a well-constrained conduit network, and thus it permits verification of the interpreted geophysical signals that arise from hydrologic processes. This transformative project will not only enable delineation of the karst conduit network, but will do so while providing a regionally integrated analysis of the karst aquifer flow system based on deformation observations on the timescales between fractions of a second to months. As recharge activates new flow paths, geophysical monitoring enables extensive 3D characterization of the dynamics and evolution of flow during recharge-induced changes in the aquifer. Furthermore, the signals will help to determine the architecture in the subsurface between the conduits and the surface, advancing knowledge of critical zone environments, for example, by specifically determining soil and regolith thicknesses and depths to the soil-rock interface. The young field of environmental seismology encompasses studies of a range of Earth surface processes, and this project will use and expand the respective methods to transform the understanding of karst aquifers across the full frequency range of deformation and develop techniques in preparation for a future karst critical zone observatory.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.

喀斯特含水层是重要的水资源，为世界上四分之一的地区提供水。年代人口。这些含水层是复杂的水文地质系统，其中的流动和运输主要通过优先的流动路径或管道进行，其大小从厘米尺度的开口到比人类所需的通道（洞穴）大得多。尽管具有重要的水文意义，但岩溶管道的位置和较大含水层的特征通常不太清楚。为了解决这些问题，我们将利用地球物理仪器对佛罗里达喀斯特含水层的管道、地下流和更大的喀斯特系统进行表征，监测水流入地下时引起的补给响应。非侵入式遥感调查将产生直接社会效益的知识，包括改进喀斯特灾害地图创建的工具，突出易受天坑形成影响的区域，识别与污染物运输相关的优先流动路径，以及开发一种确定地下水供应考虑的方法。我们将与国家洞穴和喀斯特研究所合作，举办一个临时的互动式旅游展览，该展览将经常在佛罗里达州和新墨西哥州的实地附近的游客中心举行，以增加公众对喀斯特水文地质学和环境地震学的参与和科学素养。该项目还将通过参与新墨西哥理工学院的两名研究生、佛罗里达大学的一名本科生、IRIS本科生实习生计划的两名本科生实习生，以及EPSCoR州的两名早期职业科学家和一名中期职业女性科学家，为下一代科学劳动力的教育做出贡献。最后，收集到的数据集将被纳入新墨西哥理工大学（New Mexico Tech）本科和研究生课程的讲课材料和作业集，这是一所为西班牙裔服务的机构。之前的一项试点研究表明，在喀斯特含水层的人工补给实验和自然补给事件中会产生地震信号。这些和其他地球物理信号是由流经喀斯特含水层的过程引起的，包括补给进入全管流管道时产生的压力脉冲、裂缝和岩石基质中孔隙压力的变化、由于水质量变化引起的质量加载引起的下沉以及流体与围岩的湍流相互作用。为了利用这些信号提供的信息内容，我们将在两个位于同一位置的地球物理传感器网络上同时对补给事件进行大规模观测，以表征管道网络、该网络中的流动过程以及更大的喀斯特系统的物质特性。地震仪、倾斜仪和其他仪器将被部署在佛罗里达州的圣达菲河下沉-上升系统，在两年的时间里观察喀斯特补给事件。这个现场有一个约束良好的管道网络，因此它允许验证由水文过程产生的解释的地球物理信号。这一变革性的项目不仅能够描绘喀斯特管道网络，而且还可以根据几秒到几个月不等的时间尺度上的变形观测，提供喀斯特含水层流动系统的区域综合分析。由于补给激活了新的流动路径，地球物理监测可以对含水层中补给引起的变化过程中的流动动态和演变进行广泛的三维表征。此外，这些信号将有助于确定管道和地表之间的地下结构，提高对关键区域环境的认识，例如，通过具体确定土壤和风化层的厚度和土壤-岩石界面的深度。年轻的环境地震学领域包括一系列地球表面过程的研究，该项目将使用和扩展各自的方法，在整个变形频率范围内改变对喀斯特含水层的理解，并开发技术，为未来的喀斯特临界带观测站做准备。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。

项目成果

Nitrous oxide processing in carbonate karst aquifers

• DOI: 10.1016/j.jhydrol.2020.125936
• 发表时间: 2021-03
• 期刊: Journal of Hydrology
• 影响因子: 6.4
• 作者: M. Flint;Jonathan B. Martin;T. Summerall;A. Barry-Sosa;B. Christner