Karl J Ellefsen
Karl Ellefsen is an Emeritus with the Geology, Geophysics, and Geochemistry Science Center.
Science and Products
Filter Total Items: 65
Phase and amplitude inversion of crosswell radar data Phase and amplitude inversion of crosswell radar data
Phase and amplitude inversion of crosswell radar data estimates the logarithm of complex slowness for a 2.5D heterogeneous model. The inversion is formulated in the frequency domain using the vector Helmholtz equation. The objective function is minimized using a back-propagation method that is suitable for a 2.5D model and that accounts for the near-, intermediate-, and far-field regions...
Authors
Karl J. Ellefsen, Aldo T. Mazzella, Robert Horton, Jason R. McKenna
Chromium(VI) generation in vadose zone soils and alluvial sediments of the southwestern Sacramento Valley, California: a potential source of geogenic Cr(VI) to groundwater Chromium(VI) generation in vadose zone soils and alluvial sediments of the southwestern Sacramento Valley, California: a potential source of geogenic Cr(VI) to groundwater
Concentrations of geogenic Cr(VI) in groundwater that exceed the World Health Organization’s maximum contaminant level for drinking water (50 μg L−1) occur in several locations globally. The major mechanism for mobilization of this Cr(VI) at these sites is the weathering of Cr(III) from ultramafic rocks and its subsequent oxidation on Mn oxides. This process may be occurring in the...
Authors
Christopher T. Mills, Jean M. Morrison, Martin B. Goldhaber, Karl J. Ellefsen
Monitoring soil geochemistry in the urban environment: A comparison of studies in 1972 and 2005 in Denver, Colorado Monitoring soil geochemistry in the urban environment: A comparison of studies in 1972 and 2005 in Denver, Colorado
No abstract available
Authors
David B. Smith, Karl J. Ellefsen, Ronald G. Garrett, L. Graham Closs
Geochemical data for Colorado soils: Results from the 2006 state-scale geochemical survey Geochemical data for Colorado soils: Results from the 2006 state-scale geochemical survey
In 2006, soil samples were collected at 960 sites (1 site per 280 square kilometers) throughout the state of Colorado. These samples were collected from a depth of 0-15 centimeters and, following a near-total multi-acid digestion, were analyzed for a suite of more than 40 major and trace elements. The resulting data set provides a baseline for the natural variation in soil geochemistry...
Authors
David B. Smith, Karl J. Ellefsen, James E. Kilburn
Soil geochemical data for the Wyoming Landscape Conservation Initiative study area Soil geochemical data for the Wyoming Landscape Conservation Initiative study area
In 2008, soil samples were collected at 139 sites throughout the Wyoming Landscape Conservation Initiative study area in southwest Wyoming. These samples, representing a density of 1 site per 440 square kilometers, were collected from a depth of 0-5 cm and analyzed for a suite of more than 40 major and trace elements following a near-total multi-acid extraction. In addition, soil pH...
Authors
David B. Smith, Karl J. Ellefsen
High-Frequency, Crosswell Radar Data Collected in a Laboratory Tank High-Frequency, Crosswell Radar Data Collected in a Laboratory Tank
Crosswell radar data were collected among three wells in a laboratory tank filled with dry sand. Embedded within the sand was a long plastic box, which was the target for the data collection. Two datasets were collected between each pair of wells, making a total of six datasets. The frequencies in the data ranged from 0.5 to 1.5 gigahertz, and the peak frequency was 0.9 gigahertz. The...
Authors
Bas Peters, Craig W. Moulton, Karl J. Ellefsen, Robert Horton, Jason R. McKenna
Science and Products
Filter Total Items: 65
Phase and amplitude inversion of crosswell radar data Phase and amplitude inversion of crosswell radar data
Phase and amplitude inversion of crosswell radar data estimates the logarithm of complex slowness for a 2.5D heterogeneous model. The inversion is formulated in the frequency domain using the vector Helmholtz equation. The objective function is minimized using a back-propagation method that is suitable for a 2.5D model and that accounts for the near-, intermediate-, and far-field regions...
Authors
Karl J. Ellefsen, Aldo T. Mazzella, Robert Horton, Jason R. McKenna
Chromium(VI) generation in vadose zone soils and alluvial sediments of the southwestern Sacramento Valley, California: a potential source of geogenic Cr(VI) to groundwater Chromium(VI) generation in vadose zone soils and alluvial sediments of the southwestern Sacramento Valley, California: a potential source of geogenic Cr(VI) to groundwater
Concentrations of geogenic Cr(VI) in groundwater that exceed the World Health Organization’s maximum contaminant level for drinking water (50 μg L−1) occur in several locations globally. The major mechanism for mobilization of this Cr(VI) at these sites is the weathering of Cr(III) from ultramafic rocks and its subsequent oxidation on Mn oxides. This process may be occurring in the...
Authors
Christopher T. Mills, Jean M. Morrison, Martin B. Goldhaber, Karl J. Ellefsen
Monitoring soil geochemistry in the urban environment: A comparison of studies in 1972 and 2005 in Denver, Colorado Monitoring soil geochemistry in the urban environment: A comparison of studies in 1972 and 2005 in Denver, Colorado
No abstract available
Authors
David B. Smith, Karl J. Ellefsen, Ronald G. Garrett, L. Graham Closs
Geochemical data for Colorado soils: Results from the 2006 state-scale geochemical survey Geochemical data for Colorado soils: Results from the 2006 state-scale geochemical survey
In 2006, soil samples were collected at 960 sites (1 site per 280 square kilometers) throughout the state of Colorado. These samples were collected from a depth of 0-15 centimeters and, following a near-total multi-acid digestion, were analyzed for a suite of more than 40 major and trace elements. The resulting data set provides a baseline for the natural variation in soil geochemistry...
Authors
David B. Smith, Karl J. Ellefsen, James E. Kilburn
Soil geochemical data for the Wyoming Landscape Conservation Initiative study area Soil geochemical data for the Wyoming Landscape Conservation Initiative study area
In 2008, soil samples were collected at 139 sites throughout the Wyoming Landscape Conservation Initiative study area in southwest Wyoming. These samples, representing a density of 1 site per 440 square kilometers, were collected from a depth of 0-5 cm and analyzed for a suite of more than 40 major and trace elements following a near-total multi-acid extraction. In addition, soil pH...
Authors
David B. Smith, Karl J. Ellefsen
High-Frequency, Crosswell Radar Data Collected in a Laboratory Tank High-Frequency, Crosswell Radar Data Collected in a Laboratory Tank
Crosswell radar data were collected among three wells in a laboratory tank filled with dry sand. Embedded within the sand was a long plastic box, which was the target for the data collection. Two datasets were collected between each pair of wells, making a total of six datasets. The frequencies in the data ranged from 0.5 to 1.5 gigahertz, and the peak frequency was 0.9 gigahertz. The...
Authors
Bas Peters, Craig W. Moulton, Karl J. Ellefsen, Robert Horton, Jason R. McKenna