This review quantitatively examines a number of published studies that evaluated survival and inactivation of public-health-related microorganisms in groundwater. Information from reviewed literature is used to express microbial inactivation in terms of log10 decline per day for comparison to other studies and organisms. The geometric mean value for inactivation rates for coliphage, poliovirus, echovirus, coliform bacteria, enterococci, and Salmonella spp. were similar at approximately 0.07−0.1 log10 day-1, while geometric mean inactivation rates for hepatitis A virus, coxsackievirus, and phage PRD-1 were somewhat less at 0.02−0.04 log10 day-1. Viruses show a temperature dependency with greater inactivation at greater temperatures; however this occurs largely at temperatures greater than 20 °C. Coliform bacteria dieoff in groundwater does not show the temperature dependency that viruses show, likely indicating a complex interplay of inactivation and reproduction subject to influences from native groundwat...

/pdf/review-of-factors-affecting-microbial-survival-in-emqkmjoi5c.pdf

Review of factors affecting microbial survival in groundwater.

http://www.evergladeshub.com/lit//pdf10/Chen'10ApplGeochem-81-OrgMatGroundwater.pdf

Comparative study of dissolved organic matter from groundwater and surface water in the Florida coastal Everglades using multi-dimensional spectrofluorometry combined with multivariate statistics

Solute and colloid transport in karst aquifers under low and high flows was investigated by tracer tests using fluorescent dyes (uranine) and microspheres of the size of pathogenic bacteria (1 microm) and Cryptosporidium cysts (5 microm), which were injected into a cave stream and sampled at a spring 2.5 km away. The two types of microspheres were analyzed using an epifluorescence microscope or a novel fluorescence particle counter, respectively. Uranine breakthrough curves (BTCs) were regular shaped and recovery approached 100%. Microsphere recoveries ranged between 27% and 75%. During low flow, the 1-microm spheres displayed an irregular BTC preceding the uranine peak. Only a very few 5-microm spheres were recovered. During high flow, the 1-microm-sphere BTC was regular and more similar to the uranine curve. BTCs were modeled analytically with CXTFIT using a conventional advection dispersion model (ADM) and a two-region nonequilibrium model (2RNE). The results show that (1) colloids travel at higher velocities than solutes during low flow; (2) colloids and solutes travel at similar velocities during high flow; (3) higher maximum concentrations occur during high flow; and (4) the 2RNE achieves a better fit, while the ADM is more robust, as it requires less parameters.

/pdf/solute-and-colloid-transport-in-karst-conduits-under-low-and-4ldw3qh7zd.pdf

Solute and colloid transport in karst conduits under low- and high-flow conditions.

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/pdf/documentation-of-a-conduit-flow-process-cfp-for-modflow-2005-3hq7u02yg3.pdf

Documentation of a Conduit Flow Process (CFP) for MODFLOW-2005

Water Budgets: Foundations for Effective Water-Resources and Environmental Management

Proposed expansion of extractive lime-rock mines near the Miami–Dade County Northwest well field and Everglades wetland areas has garnered intense scrutiny by government, public, environmental stakeholders, and the media because of concern that mining will increase the risk of pathogen contamination. Rock mines are excavated to the same depth as the well field's primary producing zone. The underlying karst Biscayne aquifer is a triple-porosity system characterized by (1) a matrix of interparticle porosity and separate vug porosity; (2) touching-vug porosity that forms preferred, stratiform passageways; and, less commonly, (3) conduit porosity formed by thin solution pipes, bedding-plane vugs, and cavernous vugs. Existing ground-water flow and particle tracking models do not provide adequate information regarding the ability of the aquifer to limit the advective movement of pathogens and other contaminants. Chemical transport and colloidal mobility properties have been delineated using conservative and microsphere-surrogate tracers for Cryptosporidium parvum . Forced-gradient tests were executed by introducing conservative tracers into injection wells located 100 m (328 ft) from a municipal-supply well. Apparent mean advective velocity between the wells is one to two orders of magnitude greater than previously measured. Touching-vug, stratiform flow zones are efficient pathways for tracer movement at the well field. The effective porosity for a continuum model between the point of injection and tracer recovery ranges from 2 to 4 percent and is an order of magnitude smaller than previously assumed. Existing well-field protection zones were established using porosity estimates based on specific yield. The effective, or kinematic, porosity of a Biscayne aquifer continuum model is lower than the total porosity, because high velocities occur along preferential flow paths that result in faster times of travel than can be represented with the ground-water flow equation. Tracer tests indicate that the relative ease of contaminant movement to municipal supply wells is much greater than previously considered.

/pdf/assessing-the-vulnerability-of-a-municipal-well-field-to-27pf5gvdf6.pdf

Assessing the Vulnerability of a Municipal Well Field to Contamination in a Karst Aquifer

Combined analyses of cores, borehole geophysical logs, and cyclostratigraphy produced a new conceptual hydrogeologic framework for the triple-porosity (matrix, touching-vug, and conduit porosity) karst limestone of the Biscayne aquifer in a 0.65 km2 study area, SE Florida. Vertical lithofacies successions, which have recurrent stacking patterns, fit within high-frequency cycles. We define three ideal highfrequency cycles as: (1) upward-shallowing subtidal cycles, (2) upward-shallowing paralic cycles, and (3) aggradational subtidal cycles. Digital optical borehole images, tracers, and flow meters indicate that there is a predictable vertical pattern of porosity and permeability within the three ideal cycles, because the distribution of porosity and permeability is related to lithofacies. Stratiform zones of high permeability commonly occur just above flooding surfaces in the lower part of upward-shallowing subtidal and paralic cycles, forming preferential groundwater flow zones. Aggradational subtidal cycles are either mostly high-permeability zones or leaky, low-permeability units. In the study area, groundwater flow within stratiform high-permeability zones is through a secondary pore system of touching-vug porosity principally related to molds of burrows and pelecypods and to interburrow vugs. Movement of a dye-tracer pulse observed using a borehole fluid-temperature tool during a conservative tracer test indicates heterogeneous permeability. Advective movement of the tracer appears to be most concentrated within a thin stratiform flow zone contained within the lower part of a high-frequency cycle, indicating a distinctly high relative permeability for this zone. Borehole flow-meter measurements corroborate the relatively high permeability of the flow zone. Identification and mapping of such high-permeability flow Cunningham, K.J., Renken, R.A., Wacker, M.A., Zygnerski, M.R., Robinson, E., Shapiro, A.M., and Wingard, G.L., 2006, Application of carbonate cyclostratigraphy and borehole geophysics to delineate porosity and preferential flow in the karst limestone of the Biscayne aquifer, SE Florida, in Harmon, R.S., and Wicks, C., eds., Perspectives on karst geomorphology, hydrology, and geochemistry—A tribute volume to Derek C. Ford and William B. White: Geological Society of America Special Paper 404, p. 191–208, doi: 10.1130/2006.2404(16). For permission to copy, contact editing@geosociety.org. ©2006 Geological Society of America. All rights reserved.

Application of carbonate cyclostratigraphy and borehole geophysics to delineate porosity and preferential flow in the karst limestone of the Biscayne aquifer, SE Florida

[1] The Biscayne aquifer is a highly transmissive karst limestone that serves as the sole source of drinking water to over two million residents in south Florida. The aquifer is characterized by eogenetic karst, where the most transmissive void space can be an interconnected, touching-vug, biogenically influenced porosity of biogenic origin. Public supply wells in the aquifer are in close proximity to lakes established by surface mining. The mining of the limestone has occurred to the same depths as the production wells, which has raised concerns about pathogen and chemical transport from these surface water bodies. Hydraulic and forced gradient tracer tests were conducted to augment geologic and geophysical studies and to develop a hydrogeologic conceptual model of groundwater flow and chemical transport in the Biscayne aquifer. Geologic and geophysical data indicate multiple, areally extensive subhorizontal preferential flow zones of vuggy limestone separated by rock with a matrix pore system. The hydraulic response from an aquifer test suggests that the Biscayne aquifer behaves as a dual-porosity medium; however, the results of the tracer test showed rapid transport similar to other types of karst. The tracer test and concurrent temperature logging revealed that only one of the touching-vug flow zones dominates transport near the production wells. On the basis of the rising limb of the breakthrough curve, the dispersivity is estimated to be less than 3% of the tracer travel distance, which suggests that the fastest flow paths in the formation are likely to yield limited dilution of chemical constituents.

https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/2007WR006058

Pathogen and chemical transport in the karst limestone of the Biscayne aquifer: 1. Revised conceptualization of groundwater flow

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A cyclostratigraphic and borehole-geophysical approach to development of a three-dimensional conceptual hydrogeologic model of the karstic Biscayne aquifer, southeastern Florida

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/pdf/origins-and-delineation-of-saltwater-intrusion-in-the-555nt6aps2.pdf

Michael A. Wacker

Papers

Assessing the Vulnerability of a Municipal Well Field to Contamination in a Karst Aquifer

Application of carbonate cyclostratigraphy and borehole geophysics to delineate porosity and preferential flow in the karst limestone of the Biscayne aquifer, SE Florida

Pathogen and chemical transport in the karst limestone of the Biscayne aquifer: 1. Revised conceptualization of groundwater flow

A cyclostratigraphic and borehole-geophysical approach to development of a three-dimensional conceptual hydrogeologic model of the karstic Biscayne aquifer, southeastern Florida

Origins and delineation of saltwater intrusion in the Biscayne aquifer and changes in the distribution of saltwater in Miami-Dade County, Florida