Reversals of karst springs: Implications for water budgets, water quality, and speleogenesis

摘要本奖项由2009年美国复苏与再投资法案（公法111-5）资助。知识价值。河流洪水期间泉水的逆转（如estavelles的形成）可能会将有机碳带到贫营养环境中，在那里有机碳将被再矿化，改变营养物和终端电子受体（如溶解氧（DO）、NO3、Fe和Mn氧化物）的浓度，并增加pCO2。二氧化碳分压升高应在排放点而不是下沉的溪流处促使溶解。逆转将由泉水、管道、地下水和河流之间的水头梯度控制，但这种简单的观点会因先决条件、扩散补给率与异体补给率、含水层的水力特性和含水层限制而变得复杂。这些弹簧反转的潜在影响导致这里要解决的问题包括：(1)含水层中的水头、流量、漫射补给和含水层约束之间的关系是什么？(2)回驱水返回地表的速率是多少？(3)控制反驱水成分的主要固流反应是什么？这些问题将在佛罗里达州中北部苏旺尼河沿岸的四个泉水（麦迪逊布鲁，特洛伊，孔雀和范宁）中得到解决，所有这些泉水都经历了频繁的逆转。Madison Blue， Troy和Fanning springs是正在进行的监测项目的站点，这些站点已经产生了许多关于流体和化学的遗留数据，这些数据将补充作为该项目一部分收集的新数据。将在基流期间以低频率收集样品以观察背景化学成分，并在反转事件期间以高分辨率收集样品以构建洪水化学图谱。特定的电导率、温度、DO和pH值将通过可靠的现成测井仪器进行监测。数据收集和分析将包括利用现有和新的放电数据估计反转幅度。Sr同位素比率和水的年龄（3H/3He比率和CFC浓度）将用于分离洪水和地下水的馏分。主要元素的浓度将被用来评估水的饱和状态。测量DO、NO3、NH4、Fe2+、Fe3+、Mn、硫酸盐、硫化物、溶解的无机和有机碳浓度，以及？Ô13CDICvalues将用于估计有机质再矿化的大小。数据建模将包括模拟流动的MODFLOW和估计氧化还原和饱和状态的PHREEQC。更广泛的影响。与许多喀斯特地区类似，苏万尼河流域正在经历土地利用的快速变化和地下水采收率的提高。这个盆地也是各种濒临灭绝的海鞘动物的家园。这些问题需要仔细管理水质和水量，这两者都将受到春季逆转的影响。Suwannee河也被提议作为WATERS网络的站点，其最大的支流圣达菲河是一个资助的“试验台”项目的站点。试验台项目将通过水文信息系统（HIS）的数据处理和存储相结合的方式与本项目联系起来。研究地点位于州立公园，允许与一般人群互动。洞穴潜水在公园里很常见，潜水员会自愿收集样本。该项目将为本科生和研究生提供培训，他们将处理遗留数据，研究生将在他们的论文或学位论文中使用该项目。结果将在佛罗里达大学目前教授的几门课程的正式课堂培训中作为例子。

ABSTRACTThis award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5). Intellectual Merit. Reversal of springs during river flooding (e.g., formation of estavelles) are likely to carry organic carbon to oligotrophic environments where it will be remineralized, changing concentrations of nutrients and terminal electron acceptors such as dissolved oxygen (DO), NO3, and Fe and Mn oxides, and increase pCO2. Elevated pCO2 should drive dissolution at the discharge point rather than at sinking streams. Reversals will be controlled by head gradients between the spring, conduits, groundwater, and rivers, but this simplistic view is complicated by antecedent conditions, the rates of diffuse versus allogenic recharge, hydraulic properties of the aquifer, and aquifer confinement. These potential effects of spring reversals lead to questions addressed here including: (1) What are the relationships between hydraulic head in the aquifer, discharge, diffuse recharge, and aquifer confinement? (2) At what rate is backflooding water returned to the surface? (3) What are the primary solid-fluid reactions controlling backflooded water compositions? These questions will be addressed at four springs (Madison Blue, Troy, Peacock, and Fanning) along the Suwannee River in north-central Florida, all of which experience frequent reversals. Madison Blue, Troy and Fanning springs are sites of on-going monitoring programs that have generated much legacy data about flow and chemistry, which will supplement new data collected as part of this project. Samples will be collected at low frequency during base flow to observe background chemical compositions and at high resolution during a reversal event to construct flood chemographs. Specific conductivity, temperature, DO, and pH will be monitored with reliable off the shelf logging instruments. Data collection and analyses will include estimates of reversal magnitudes using available and new discharge data. Sr isotope ratios and age of water (3H/3He ratios and CFC concentrations) will be used to separate fractions of flood water and groundwater. Major element concentrations will be used to assess saturation states of the water. Measurements of DO, NO3, NH4, Fe2+, Fe3+, Mn, sulfate, sulfide, dissolved inorganic and organic carbon concentrations, and ?Ô13CDICvalues will be used to estimate the magnitude of organic matter remineralization. Data modeling will include MODFLOW to simulate flow and PHREEQC to estimate redox and saturation states.Broader impacts. Similar to many karst areas, the Suwannee River Basin is experiencing rapid land use changes and elevated groundwater withdrawals. The basin is also home to a variety of endangered stygobitic fauna. These issues require careful management of water quality and quantity, both of which will be affected by spring reversals. The Suwannee River has also been proposed as a site for the WATERS network, and its largest tributary, the Santa Fe River, is the site of a funded ¡§test-bed¡¨ project. The test bed project will be linked to this project through combined data handling and storage using Hydrologic Information System (HIS).Study sites are located in state parks, allowing interaction with the general population. Cave diving is common at the parks, and divers will volunteer for sample collection. The project will provide training for undergraduates, who will work with legacy data, graduate students, who will work on the project for their thesis or dissertations. Results will be used as examples in formal classroom training in several courses currently taught at the University of Florida.