Jason Polk

Application of a cave inventory system to stimulate development of management strategies: the case of west-central Florida, USA.

The active management of air-filled cave systems is virtually non-existent within the karst landscape of west-central Florida. As in every karst landscape, caves are important because they contain a wide variety of resources (e.g., biota, speleothems) and can act as direct connections between surface and subsurface hydrological processes, potentially exacerbating the pollution of groundwater. Before sound management policies can be drafted, implemented, and enforced, stakeholders must first have knowledge of the management requirements of each cave. However, there is an informational disconnect between researchers, stakeholders, and the recreational caving community. Here, we present a cave inventory system that simplifies the dissemination of resource knowledge to stakeholders so that cave management and protection policies can be drafted and implemented at the state and local level. We inventoried 36 caves in west-central Florida, located on both public and private land, and analyzed cave resource data to provide insights on cave sensitivity and disturbance using two standardized indices. The data revealed that both public and private caves exhibit a wide range of sensitivity and disturbance, and before management strategies can be drafted, the ownership of each cave must be considered. Our inventory geodatabase serves as a link between researchers, landowners, and the public. To ensure the conservation and protection of caves, support from county or state government, combined with cave inventory data, is crucial in developing sound management policy.

A GIS-based modeling approach to predicting cave disturbance in karst landscapes: a case study from west-central Florida

We present a GIS-based cave disturbance model (CDM) that can be used as a tool to predict the disturbance of cave systems. To validate our model, we compare results to an in situ cave disturbance index (CDI) that was applied to 36 terrestrial caves during the year 2007 in west-central Florida. The CDM demonstrated high-performance skill and produced similar disturbance scores compared to the CDI. The CDM disturbance scores ranged from 0.22 (minimum) to 0.78 (maximum), and the mean disturbance score for all 36 caves was 0.45. The mean of the CDI scores was 0.40, but the difference between means was not significantly different (p = 0.147, t-test). Disturbance scores from the CDM and CDI were significantly correlated (R = 0.45, R2 = 0.20; p < 0.001), but a linear model of the data only explains ca. 20% of the variance. We demonstrate that land managers, who are unable to conduct an in situ inventory of caves to determine inherent disturbance, can use the GIS-based CDM tool as a proxy. In theory, the design of the CDM makes it applicable to other areas, but more research is needed to increase model accuracy in west-central Florida, as well as in other karst regions around the world.

Climatic Influences on Coastal Cave and Karst Development in Florida

Coastal karst development in Florida is a complex, temporally variable phenomenon that was influenced by eustatic processes and long-term climatic variability through the Cenozoic up through the present. Much of the past history involving coastal and climatic influences on cave and karst evolution in Florida is still not well understood. Currently, Florida is home to almost 20 million people that reside one of the world’s largest and most productive karst aquifer systems, featuring hundreds of springs, caves, and sinkholes as part of its karst geomorphology. The large carbonate platform is exposed to hurricanes, sea level rise, and continued groundwater withdrawal. Therefore, it is important to consider Florida’s karst landscape as an evolving geomorphological system under both past and current environmental conditions. It is important to understand the rock, structure, gradient, fluid, and time elements of Florida’s karst development, with a particular emphasis placed on the climatic influences that shaped the landscape. Focusing on the central and northern regions of the peninsula where the ridgelands and coastal lowlands contain the most exposed karst features, the elements of gradient, fluid, and time interact with climate in such a way that the karst landscape development can be partially explained by changes in the hydrology related to water table fluctuations, sea-level changes, and variability in precipitation patterns over time. Aquifer development, speleogenesis, and paleoclimatic changes on these processes are discussed, while noting that the primary mechanisms controlling cave development,sinkhole occurrence, and karst evolution are past changes in sea level and water table movement. The state’s karst regions are described within this context to organize the discussion of the coastal karst development of peninsular Florida under variable climatic conditions.

Delineating vulnerability of karst aquifers using hydrochemical tracers in Southwestern China

Karst groundwater is particularly vulnerable to contamination. Long-term hydrochemistry auto-monitoring combined with laboratory analyses has shown that the chemograph demonstrates changes in the system. In order to determine the primary groundwater vulnerability, a relationship between hydrochemical changes and the origin of vulnerability in six karst spring catchments in Southwestern China is discussed. The reason and physical meaning of the hydrochemical changes in the spring are explained based on tracer tests and physical–chemical process in the S31 spring. The results prove that the hydrochemical changes show the origin of vulnerability and also can be its expression. Generally, autogenic recharge in bare karst is concentrated in epikarst zone, forming bypass flow and shaft flow, which causes dilution of Ca2+. The chemograph reflects the percentage of concentrated and diffuse recharge. The higher the ratio of concentrated recharge, the higher the grade of groundwater vulnerability. Due to Ca2+, HCO3−, SEC, pH, and temperature in water can change for kinds of reasons during their transport, more karst systems with variable natural and human factors are discussed. Protective layer, allogenic water recharge, and transform of surface stream and subterranean river can change the origin shape of hydrochemical curve. Under this circumstance, more indicators need to be monitored, especially contaminant-related ions such as nitrate, in order to clearly understand the contribution of concentrated and diffuse recharge to water chemistry. After comparing the traditional groundwater vulnerability assessment and the methods based on hydrochemical change, rainfall, protective layer, epikarst, transient storage and karst network should be more concerned when the work is done. Auto-monitoring of karst is more and more popular in Southwestern China; therefore, it is suggested that the hydrochemical methods should be used as a primary expression of vulnerability, giving a direct reference for karst water management.

Hypogene Karst Influences in the Upper Floridan Aquifer

Dissolution of eogenetic carbonates in the Upper Floridan aquifer has produced the world’s densest assemblage of first-magnitude cave springs. Conceptual and numerical models of cave origin in the aquifer have emphasized epigenic and mixing-dissolution processes. We draw upon recent research concerning phreatic caves in the Suwannee River Basin, and dry caves in the west and central Florida, to suggest instead that many caves in the aquifer formed by hypogenic processes. Formerly, undersaturation generated in the subsurface has usually been ascribed to the mixing of, or temperature changes in, subsurface fluids. Here, we describe an alternate process. Cave formation at modern water tables in the aquifer has been linked to respiration of CO2 in the deep vadose zone and at water tables. Respired CO2 generates carbonate mineral undersaturation when it hydrates to carbonic acid at water tables. Because undersaturated waters are created at the water table, caves form as isolated macropores. Caves at modern water tables in the aquifer lack initial connections to the surface (e.g., entrances) and have morphologies that are unrelated to surface drainage, making them similar in many respects to flank margin caves (see Mylroie and Mylroie, Chap. 51). Since many caves that are below the modern water table have similar morphologies to caves that are at the modern water table, it is likely that they formed by similar processes operating at water tables associated with lower sea levels. These caves became sources of springs and flooded sinkholes when Holocene sea-level rise elevated water tables close to, and above, the land surface.

Evaluating Weather Research and Forecasting Model Sensitivity to Land and Soil Conditions Representative of Karst Landscapes

Due to their particular physiographic, geomorphic, soil cover, and complex surface-subsurface hydrologic conditions, karst regions produce distinct land–atmosphere interactions. It has been found that floods and droughts over karst regions can be more pronounced than those in non-karst regions following a given rainfall event. Five convective weather events are simulated using the Weather Research and Forecasting model to explore the potential impacts of land-surface conditions on weather simulations over karst regions. Since no existing weather or climate model has the ability to represent karst landscapes, simulation experiments in this exploratory study consist of a control (default land-cover/soil types) and three land-surface conditions, including barren ground, forest, and sandy soils over the karst areas, which mimic certain karst characteristics. Results from sensitivity experiments are compared with the control simulation, as well as with the National Centers for Environmental Prediction multi-sensor precipitation analysis Stage-IV data, and near-surface atmospheric observations. Mesoscale features of surface energy partition, surface water and energy exchange, the resulting surface-air temperature and humidity, and low-level instability and convective energy are analyzed to investigate the potential land-surface impact on weather over karst regions. We conclude that: (1) barren ground used over karst regions has a pronounced effect on the overall simulation of precipitation. Barren ground provides the overall lowest root-mean-square errors and bias scores in precipitation over the peak-rain periods. Contingency table-based equitable threat and frequency bias scores suggest that the barren and forest experiments are more successful in simulating light to moderate rainfall. Variables dependent on local surface conditions show stronger contrasts between karst and non-karst regions than variables dominated by large-scale synoptic systems; (2) significant sensitivity responses are found over the karst regions, including pronounced warming and cooling effects on the near-surface atmosphere from barren and forested land cover, respectively; (3) the barren ground in the karst regions provides conditions favourable for convective development under certain conditions. Therefore, it is suggested that karst and non-karst landscapes should be distinguished, and their physical processes should be considered for future model development.

Comparing and refining karst disturbance index methods through application in an island karst setting

The interconnected nature of surface and subsurface karst environments allows easy disturbance to their aquifers and specialized ecosystems from anthropogenic impacts. The karst disturbance index is a holistic tool used to measure disturbance to karst environments and has been applied and refined through studies in Florida and Italy, among others. Through these applications, the karst disturbance index has evolved into two commonly used methods of application; yet, the karst disturbance index is still susceptible to evaluation and modification for application in other areas around the world. The geographically isolated and highly vulnerable municipality of Arecibo, Puerto Rico’s karst area provides an opportunity to test the usefulness and validity of the karst disturbance index in an island setting and to compare and further refine the application of the original and modified methods. This study found the both methods of karst disturbance index application resulted in high disturbance scores (Original Method 0.54 and Modified Method 0.69, respectively) and uncovered multiple considerations for the improvement of the karst disturbance index. An evaluation of multiple methods together in an island setting also resulted in the need for adding additional indicators, including Mogote Removal and Coastal Karst. Collectively, the results provide a holistic approach to using the karst disturbance index in an island karst setting and suggest a modified method by which scaling and weighting may compensate for the difference between the original and modified method scores and allow interested stakeholders to evaluate disturbance regardless of his or her level of expertise.

Recharge mixing in a complex distributary spring system in the Missouri Ozarks, USA

Toronto Springs is a complex distributary karst spring system with 11 perennial springs in the Missouri Ozarks, USA. Carroll Cave (CC) and Wet Glaize Creek (WG) were previously identified as principal recharge sources. This study (1) characterized physical and chemical properties of springs and recharge sources; (2) developed end-member mixing models to estimate contributing proportions of CC and WG; and (3) created a conceptual model for the system. Samples analyzed for major ions and specific conductivity, in conjunction with a rotating continuous monitoring program to identify statistically comparable baseflow conditions, were used to assess differences among the sites. Monitoring data showed that the springs differed depending upon recharge proportions. Cluster analysis of average ion concentrations supported the choice of CC and WG as mixing model end members. Results showed a range in the proportions of the recharge sources, from surface-water to groundwater dominated. A conceptual model suggests that a system of distinct conduits beneath the WG flood plain transmits water to the individual springs. These conduits controlled the end-member recharge contributions and water chemistry of the springs. Interpretation of relative proportions of recharge contributions extends existing knowledge of karst hydrologic geometry beyond that of point-to-point connections to revealing complex surface-water/groundwater mixing in heterogeneous distributary spring systems.RésuméLes sources Toronto constituent un système complexe de distribution de sources karstiques avec 11 émergences pérennes dans les Ozarks du Missouri, Etats-Unis d’Amérique. La grotte Carroll (CC) et la rivière Wet Glaize (WG) ont été au préalable identifiées comme constituant la principale recharge. La présente étude (1) caractérise les propriétés physiques et chimiques des émergences et des vecteurs de la recharge; (2) développe des modèles de mélange à polarités pour estimer les contributions de CC et de WG; et (3) élabore un modèle conceptuel pour le système. Des analyses d’échantillons pour les ions majeurs et la conductivité spécifique, conjointement à un programme de surveillance continu à rotation destiné à identifier des conditions d’écoulement de débit de base statistiquement comparables, ont été utilisées pour estimer les différences entre les sites. Les données de suivi montrent que les différences entre les émergences dépendent du pourcentage de recharge. L’analyse typologique des concentrations moyennes des ions permet de choisir CC et WG comme les pôles du modèle de mélange. Les résultats montrent une variation en terme de pourcentage des vecteurs de recharge, depuis les eaux de surface jusqu’à une dominante d’eaux souterraines. Un modèle conceptuel suggère que le système de conduits situé en-dessous de la plaine d’inondation WG assure le transfert de l’eau jusqu’aux émergences individualisées. Ces conduits contrôlent les contributions des différents pôles de recharge identifiés dans le modèle de mélange et l’hydrochimie des émergences. L’interprétation des pourcentages relatifs des contributions à la recharge étend la connaissance de la configuration hydrologique du karst au-delà de celle des connexions point à point, révélant un mélange complexe d’eaux de surface et d’eaux souterraines dans des systèmes hétérogènes de distribution d’émergences.ResumenLos manantiales de Toronto Springs constituyen un sistema distributario complejo de manantiales kársticos con 11 manantiales perennes en el Missouri Ozarks, EEUU. Carroll Cave (CC) y Wet Glaize Creek (WG) fueron previamente identificados como las principales fuentes de recarga. Este estudio (1) caracterizó las propiedades físicas y químicas de los manantiales y las fuentes de recarga; (2) desarrolló modelos de mezcla de los miembros extremos para estimar las proporciones contribuyentes de CC y WG; y (3) creó un modelo conceptual del sistema. Se utilizaron las muestras analizadas orientadas a iones mayoritarios y conductividad específica, en conjunción con un programa rotativo de monitoreo continuo para identificar condiciones estadísticamente comparables del flujo de base, con el objeto de evaluar las diferencias entre ambos sitios. Los datos de monitoreo mostraron que los manantiales diferían en función de las proporciones de la recarga. El análisis de cluster de las concentraciones promedio de los iones apoyó la elección de CC y WG como un modelo de mezcla de los miembros extremos. Los resultados mostraron un intervalo en las proporciones de las fuentes de recarga, desde ser dominadas por agua superficial a agua subterránea. Un modelo conceptual sugiere que el sistema de distintas conductos por debajo de la planicie de inundación de WG transmite agua a los manantiales individuales. Estos conductos controlaban las contribuciones a la recarga de los miembros extremos y de la química del agua de los manantiales. La interpretación de las proporciones relativas de las contribuciones de la recarga extiende el conocimiento existente de la geometría hidrológica del karst más allá que las conexiones punto a punto para revelar la complejas mezclas agua superficial/agua subterránea en sistemas distributarios heterogéneos de manantiales.抽象摘要:多伦多泉系统是一个复杂的支流泉系统,这个泉系统包括美国密苏里州欧扎克市11个常流泉。Carroll Cave 和 Wet Glaize Creek 曾被确认为主要补给源。这项研究(1)描述了泉和补给源的物理和化学特性;(2)开发了端元混合模型,以估算Carroll Cave 和 Wet Glaize Creek贡献比例;(3)创立了系统的概念模型。用于分析主要离子及电导率的样品,连同确认统计上可比较的基流条件的循环连续监测程序用来评价各地点的差别。监测资料显示,泉的差别取决于补给比例。平均离子浓度聚合分析支持选择Carroll Cave 和 Wet Glaize Creek作为混合模型端元。结果显示了从地表水到地下水主导的补给源比例范围。概念模型表明,Wet Glaize Creek洪泛平原之下的独特的管道系统向各泉输水。这些管道控制着端元补给贡献率及泉的化学成分。补给贡献率的相对比例论述不但扩充了岩溶水文化学现有的认知,而且还扩充了揭示异质支流泉系统中复杂的地表水/地下水混合点对点的连接认知。ResumoAs nascentes Toronto correspondem a um sistema distributário cárstico complexo, com 11 nascentes perenes na porção Missouri dos montes Orzaks, EUA. As Cavernas Carroll (CC) e o Córrego Wet Glaize (WG) foram inicialmente identificadas como as principais fontes de recarga. Esse estudo (1) caracterizou propriedades físicas e químicas de nascentes e fontes de recarga; (2) desenvolveu um modelo misturado de membros finais para estimar a contribuição proporcional das CC e do WG; e (3) criou um modelo conceitual para o sistema. As amostras analisadas para os principais íons e condutividade específica, em conjunto com um programa de monitoramento contínuo de rotação para identificar as condições de escoamento de base estatisticamente comparáveis, foram utilizados para avaliar diferenças entre as áreas. Os dados de monitoramento mostraram que as nascentes diferiram dependendo das proporções de recarga. A análise de agrupamento das concentrações médias de íons apoiou a escolha das CC e do WG como um modelo misturado de membros finais. Os resultados mostraram uma faixa nas proporções das fontes de recarga, a partir de um domínio por parte das águas superficiais para um domínio por parte das águas subterrâneas. O modelo conceitual sugere que um sistema de condutos distintos sob a planície de inundação do WG transmite água para as nascentes individuais. Estes condutos controlam as contribuições dos membros finais de recarga e a química da água das nascentes. A interpretação de proporções relativas das contribuições de recarga estende-se ao conhecimento existente de geometria hidrológica do carste, além daquela de conexões ponto-a-ponto, ao revelar misturas complexas entre águas superficiais/águas subterrâneas em sistemas distributários heterogêneos de nascentes.

Use of Molecular Markers to Compare Escherichia coli Transport with Traditional Groundwater Tracers in Epikarst

Bacterial contamination of karst aquifers is a global concern as water quality deteriorates in the face of decreasing water security. Traditional abiotic groundwater tracers, which do not exhibit surface properties similar to bacteria, may not be good proxies for risk assessment of bacterial transport in karst environments. This study examined the transport and attenuation of two isolates of in relation to traditional groundwater tracers (rhodamine WT dye and 1-μm-diam. latex microspheres) through ∼30 m of epikarst in western Kentucky. Differential movement of the four tracers was observed, with tracer behavior dependent on flow conditions. Dye arrived at the sampling site prior to particulates. Molecular biology techniques successfully detected bacteria in the cave and showed attenuation was greater for a bacterial isolate with high attachment efficiency compared with an isolate known to have low attachment efficiency. Microspheres were first detected simultaneously with the low-attachment isolate but attained maximum concentrations during increases in discharge >11 d post-injection. Bacteria were remobilized by storm events >60 d after injection, illustrating the storage capacity of epikarst with regard to potential contaminants. The two bacterial strains were not transported at the same rate within the epikarst, showing breakthroughs during differing storm events and illustrating the importance of cell surface chemistry in the prediction of microorganism movement. Moreover, this study has shown that molecular analysis can be successfully used to target, quantify, and track introduced microbial tracers in karst terrains.

Salt transport and weathering processes in a sandstone cultural relic, North China

Salt crystallization in pore spaces will usually cause major damage to natural sandstone. Salt distribution and movement are hard to detect in the field within a small scale. Understanding salt generation and transportation in semi-arid regions can help to protect natural cultural relics and control the salt weathering damage. Salt transportation behavior and deposition processes in Yungang Grotto were studied through a detailed hydrochemistry analysis within the context of the atmosphere–rock–water environmental system. Changes of salt types in different media were analyzed according to the sequence of water and salt transportation, integrating the results of atmospheric dry and wet deposition, soil in the aeration area and sandstone, and salt on the rock surface. The study shows the generation of salt is related to vertical transport in the soil and rock weathering zone. Salt transportation originates from soil cover, passes through the sandstone weathering zone, and finally accumulates in the grottoes. Due to coal burning pollution, acid deposits leading to sulfate bind to the soil. Salt generation in soil is the result of neutralization among sulfate, carbonate, and carbonate minerals, leading to cations of soluble salt that give priority to bonding with Ca2+ and Mg2+, while the anions are mainly HCO3− and SO42−. Salt in sandstone weathered crust is not only impacted by soil, but also carbonate dissolution from CO2-rich water, its inverse process, and feldspar dissolution. Rock surfaces in the inner grottoes suffer intense evaporation, resulting in salt accumulation, and carbonate and sulfate mineral deposition or dissolution, producing the salt type of MgSO4 or NaSO4, while HCO3− and Ca2+ are heavily consumed. The result can provide a scientific basis for engineering measures that reduce the hazard of salt accumulation.