Open Access. Powered by Scholars. Published by Universities.®
Articles 1 - 6 of 6
Full-Text Articles in Geology
Preliminary Geophysical Characterization Of The Karst Within A Transverse Glade In The Atlantic Coastal Ridge, Miami-Dade County Florida, Usa, Lee J. Florea, Jeff Ransom, Dallas Hazelton
Preliminary Geophysical Characterization Of The Karst Within A Transverse Glade In The Atlantic Coastal Ridge, Miami-Dade County Florida, Usa, Lee J. Florea, Jeff Ransom, Dallas Hazelton
Lee J Florea, PhD, P.G.
In this paper we present results of two DC Electrical Resistivity Tomography surveys at Deering Estate at Cutler in the Atlantic Coastal Ridge of Miami-Dade County, Florida. This County Natural Area encompasses Deering Glade and hosts one of the largest remaining tropical hardwood-hammock ecosystems in the USA. A canal extension, wetland restoration, and pump station recently constructed at Deering Estate by the South Florida Water Management District is designed to re-hydrate Deering Glade to pre-development conditions thus helping to sustain the hammock ecosystem and reverse trends in salt-water intrusion in this portion of the Biscayne aquifer. For these transects, we …
Isotopes Of Carbon In A Karst Aquifer Of The Cumberland Platea Of Kentucky , Usa, Lee J. Florea
Isotopes Of Carbon In A Karst Aquifer Of The Cumberland Platea Of Kentucky , Usa, Lee J. Florea
Lee J Florea, PhD, P.G.
In this study, the concentration and isotopic composition of dissolved organic carbon (DOC) and dissolved inorganic carbon (DIC) are measured in the karst groundwater of the Otter Creek watershed of the Cumberland Plateau of Kentucky, USA. Comparisons among these data and with the geochemistry of carbonate and gypsum equilibrium reactions reveal that DOC concentration is inversely related to discharge, multiple reaction pathways provide DIC with isotopic enrichment that may be directly related to mineral saturation, and oxidation of reduced sulfur is possible for dissolution. DOC is derived from C3 vegetation with an average δ13CDOC of ‒27‰. DIC in groundwater is …
Fractal Characterization Of Fracture Networks: An Improved Box-Counting Technique, Ankur Roy, Edmund Perfect, William M. Dunne, Larry Mckay
Fractal Characterization Of Fracture Networks: An Improved Box-Counting Technique, Ankur Roy, Edmund Perfect, William M. Dunne, Larry Mckay
Larry McKay
Box counting is widely used for characterizing fracture networks as fractals and estimating their fractal dimensions (D). If this analysis yields a power law distribution given by N $\propto$ r−D, where N is the number of boxes containing one or more fractures and r is the box size, then the network is considered to be fractal. However, researchers are divided in their opinion about which is the best box‐counting algorithm to use, or whether fracture networks are indeed fractals. A synthetic fractal fracture network with a known D value was used to develop a new algorithm for the box‐counting method …
Evaluation Of Chloride And Pesticide Transport In A Fractured Clayey Till Using Large Undisturbed Columns And Numerical Modeling, Peter R. Jorgensen, Larry Mckay, Niels H. Spliid
Evaluation Of Chloride And Pesticide Transport In A Fractured Clayey Till Using Large Undisturbed Columns And Numerical Modeling, Peter R. Jorgensen, Larry Mckay, Niels H. Spliid
Larry McKay
Saturated groundwater flow and tracer experiments using fluorescent dye, chloride, and the herbicides mecoprop and simazine were carried out in the laboratory using three large-diameter (0.5 m) undisturbed columns of fractured clayey till. Hydraulic conductivity of the columns ranged from 10−5 m/s in the shallowest column (1 m dept)) to 10−7 m/s in the deepest column (4 m depth) and were similar to field-measured values for these deposits. Results of the tracer experiments are consistent with a conceptual model of advective transport along the fractures combined with diffusion into the fine-grained matrix between the fractures. Arrival of the chloride tracer …
Field Experiments In A Fractured Clay Till: 2. Solute And Colloid Transport, Larry Mckay, Robert W. Gillham, John A. Cherry
Field Experiments In A Fractured Clay Till: 2. Solute And Colloid Transport, Larry Mckay, Robert W. Gillham, John A. Cherry
Larry McKay
A field tracer experiment was conducted in a lateral flow field in the weathered and highly fractured upper 6 m of a 40-m-thick clay-rich till plain in southwestern Ontario. In the upper 3 m where fractures are closely spaced (<0.13 m) the advancing front (C/C0 = 0.01) of the nonreactive solute tracers, bromide and 18O, migrated at rates of 0.01 to 0.07 m/d, over distances of 4 and 6 m and under a lateral hydraulic gradient of 0.24. In this same zone, two strains of colloid-sized bacteriophage tracers migrated at rates of 2 to >5 m/d. Simulations with a discrete fracture/porous matrix flow and transport model, which used the cubic law for flow in fractures, showed that diffusion of the solutes, but not the much larger colloids, into the matrix pore water between fractures is sufficient to cause the observed difference in solute and colloid transport rates. Transport-derived and hydraulic conductivity-derived fracture aperture values …
Field Experiments In A Fractured Clay Till: 1. Hydraulic Conductivity And Fracture Aperture, Larry Mckay, John A. Cherry, Robert W. Gillham
Field Experiments In A Fractured Clay Till: 1. Hydraulic Conductivity And Fracture Aperture, Larry Mckay, John A. Cherry, Robert W. Gillham
Larry McKay
Field values of horizontal hydraulic conductivity measured in the upper 1.5–5.5 m of a weathered and fractured clay-rich till were strongly influenced by smearing around piezometer intakes, which occurs during augering, and by the physical scale of the measuring device. Values measured in conventional augered piezometers were typically 1–2 orders of magnitude lower than those measured in piezometers designed to reduce smearing. Measurements of hydraulic conductivity in small-scale seepage collectors or piezometers, which typically intersect fewer than 10 fractures, vary over a much greater range, 10−10 to 10−6 m/s, than large-scale values based on infiltration into 5.5-m-deep trenches which intersect …