Karst Conduit Hyporheic Zone Exchange

新墨西哥州采矿与技术研究所的约翰·L·威尔逊该项目将首次尝试测量岩溶管道边缘(地下水位以下的洞穴)的地下水位交换。地表河流中的表生交换是一个相对较新的领域，但随着对流动污染物传输、停留时间分布、生物地球化学和生物学的影响的认识，相关的出版物正在呈指数级增长。潜流带的一个定义是地下体积，在这里水从溪流进入，流经地下，然后返回溪流。河流中的潜流带存在于各种嵌套的空间和时间尺度上，无论沿途是否有净收益、净损失，甚至没有净交换。岩溶管道的基本流体动力学与河流基本流体动力学没有什么不同，岩溶管道具有引起河流系统地下水流的相同特征。该项目将调查是否与河流一样，在岩溶管道中发生地下交换，而不考虑与含水层进行更大规模的净交换。岩溶-导管潮汐交换和相关的生物地球化学作用，成为岩溶水循环的基本组成部分。该项目将在无承压的弗洛里丹含水层的潜水管道现场进行；此外，附近还将有一个充满空气的模拟现场，在过去的地质历史中，该现场曾经历过类似的过程。岩心将从潜水和模拟地点提取。孔隙度、渗透率和岩石物理测量将作为过去导管渗流的替代指标。潜水现场的岩心孔将配备多级采样器和注射器，并将进行一系列染料示踪，以观察岩溶-管道渗流。建模将在整个项目中使用，首先帮助规划实地工作，然后合成数据。数据和模型的结果将使人们对低渗流的时间和空间尺度有深入的了解。该项目将以模型作为预测工具来概括我们的结果。岩溶含水层为美国25%的地区供水，几乎所有的水都供应给某些地区，例如佛罗里达州90%的人口。新的数学模型和实地研究将被用来阐明一个以前不为人知的过程，即流动的岩溶管道边缘的岩溶潜水交换过程，在该过程中，管道和周围的岩溶岩石基质交换水，从而对岩溶化学和生物产生影响。就像地表河流中的地下交换一样，喀斯特地下交换可能会影响供水、水质和生态，并将引起地方、州和联邦一级的环境机构和利益集团的兴趣。

Karst Conduit Hyporheic Zone ExchangeJohn L. Wilson, New Mexico Institute of Mining and TechnologyThis project will attempt to measure, for the first time, hyporheic exchange at the margin of a karst conduit (cave below the water table). Hyporheic exchange in surface streams is a relatively new field, but related publications are growing exponentially as the implications for flow contaminant transport, residence time distributions, biogeochemistry and biology are realized. One definition of the hyporheic zone is the subsurface volume where water enters from the stream, travels through the subsurface, and returns to the stream. Hyporheic zones in streams exist at a variety of nested spatial and temporal scales whether there is net gain, net loss, or even no net exchange along the course. The fundamental fluid dynamics of karst conduits are not different from streams, and karst conduits have the same features that cause hyporheic flow in fluvial systems. This project will investigate whether, as with streams, hyporheic exchange occurs in karst conduits, regardless of larger-scale net exchange with the aquifer. Karst-conduit hyporheic exchange, and related biogeochemical processing, then becomes a fundamental component of the karst water cycle. The project will be conducted in a phreatic conduit field site in the unconfined Floridan Aquifer; additionally there will be a nearby air-filled analog site that was exposed to similar processes at some time in the geologic past. Cores will be taken from the phreatic and analog sites. Porosity, permeability, and petrophysical measurements will be used a proxy indicators of past conduit hyporheic flow. The core holes at the phreatic site will be equipped with multilevel samplers and injectors, and a series of dye traces will be conducted to observe karst-conduit hyporheic flow. Modeling will be used throughout the project, first to help plan the field work and then to synthesize the data. Results from the data and models will give insights into the temporal and spatial scales of hyporheic flow. The project will end with modeling as a predictive tool to generalize our results.Karst aquifers supply water to 25% of the United States, and almost all water to some regions, e.g. 90% of Florida's population. New mathematical models and field studies will be used to illuminate a previously unrecognized process, karst hyporheic exchange at the margin of a flowing karst conduit, in which the conduit and surrounding karst rock matrix exchange water with consequences for karst chemistry and biology. As does hyporheic exchange in surface streams, karst hyporheic exchange may impact water supply, water quality, and ecology, and will be of interest to environmental agencies and interest groups at the local, state and federal level.