Aqueous Crystal Growth and Dissolution Kinetics of Calcium Carbonate Minerals at the Amarigosa Desert Research Site, Nevada Active
The USGS studies calcium carbonate mineral reactions in soils at the Amarigosa Desert Research Site (ADRS) near Beatty, Nevada, in order to better understand carbon dioxide transport to and from the soil surface, as well as sequestration of toxic elements in the soil.
Calcium Carbonate Reactions in Arid Soils at the Amargosa Desert Research Site (ADRS) Located Near Beatty, Nevada
Carbonate mineral reaction in ADRS soils is examined to identify surface-soil carbonate crusts and other soil carbonate features participating in carbon dioxide transport to and from the soil surface, and sequestration of toxic elements such as arsenic, strontium-90, and uranium. WEBMOD, which simulates hydrologic fluxes and solute concentrations using process modules coupled within the United States Geological Survey (USGS) Modular Modeling System (MMS), is used for modeling carbonate mineral reaction at the ADRS, broadening plot-scale studies to landscapes. ADRS plot photographs and surveys of carbonate encrusted surface rock are also done.
Surveys at ADRS identify carbonate reactions participating in carbon dioxide transport to and from the soil surface and contaminant sequestration. Measurements of single crystals at the ADRS Grid Area include: weight and dimension changes, repeat macro photography, and Environmental Scanning Electron Microscopy (ESEM).
Calcite single crystals, under glass domes at ADRS study plots, characterize calcite crystal reactivity in the absence of wind, and reduced water vapor transport from the soil surface. Grid plot photographs and crystal macro photographs document changes in carbonate crust occurrence at two grid locations over time. Calcium ion release rate from volcanic rock at ADRS study plots are examined to determine their contribution to calcium carbonate mineral reaction.
On-site measurements of calcium carbonate single crystals (surrogates for soil carbonate crusts) at two grid locations assess carbonate mineral reactivity in ADRS surface soils.
Measurements of single crystal weight changes show that crystals have not had a statistically significant weight change over a 21 month exposure, suggesting that measureable calcium carbonate crust development occurs at long time scales and/or occurs preferentially on volcanic substrates.
ADRS rock crusts were also examined by (ESEM) with Energy Dispersive X-ray Analysis (EDXA). This examination demonstrated each crust exhibits complex mineral morphology and chemical composition.
Aqueous Crystal Growth and Dissolution Kinetics of Earth Surface Materials
- Overview
The USGS studies calcium carbonate mineral reactions in soils at the Amarigosa Desert Research Site (ADRS) near Beatty, Nevada, in order to better understand carbon dioxide transport to and from the soil surface, as well as sequestration of toxic elements in the soil.
Calcium Carbonate Reactions in Arid Soils at the Amargosa Desert Research Site (ADRS) Located Near Beatty, Nevada
Sources/Usage: Public Domain. View Media DetailsAn aerial photo of the Amarigosa Desert Research Site grid area (near Beatty, Nevada) showing elevation contours and sampling site locations for the Aqueous Crystal Growth and Dissolution Kinetics of Calcium Carbonate Minerals research project. Carbonate mineral reaction in ADRS soils is examined to identify surface-soil carbonate crusts and other soil carbonate features participating in carbon dioxide transport to and from the soil surface, and sequestration of toxic elements such as arsenic, strontium-90, and uranium. WEBMOD, which simulates hydrologic fluxes and solute concentrations using process modules coupled within the United States Geological Survey (USGS) Modular Modeling System (MMS), is used for modeling carbonate mineral reaction at the ADRS, broadening plot-scale studies to landscapes. ADRS plot photographs and surveys of carbonate encrusted surface rock are also done.
Surveys at ADRS identify carbonate reactions participating in carbon dioxide transport to and from the soil surface and contaminant sequestration. Measurements of single crystals at the ADRS Grid Area include: weight and dimension changes, repeat macro photography, and Environmental Scanning Electron Microscopy (ESEM).
Calcite single crystals, under glass domes at ADRS study plots, characterize calcite crystal reactivity in the absence of wind, and reduced water vapor transport from the soil surface. Grid plot photographs and crystal macro photographs document changes in carbonate crust occurrence at two grid locations over time. Calcium ion release rate from volcanic rock at ADRS study plots are examined to determine their contribution to calcium carbonate mineral reaction.
On-site measurements of calcium carbonate single crystals (surrogates for soil carbonate crusts) at two grid locations assess carbonate mineral reactivity in ADRS surface soils.
Measurements of single crystal weight changes show that crystals have not had a statistically significant weight change over a 21 month exposure, suggesting that measureable calcium carbonate crust development occurs at long time scales and/or occurs preferentially on volcanic substrates.
ADRS rock crusts were also examined by (ESEM) with Energy Dispersive X-ray Analysis (EDXA). This examination demonstrated each crust exhibits complex mineral morphology and chemical composition.
Sources/Usage: Public Domain. View Media DetailsEnvironmental Scanning Electron Microscopy (ESEM) of mineral crusts obtained from ADRS surface soils near grid location G7,7. Color differences reflect differences in the signal strength between the secondary electron detector and the backscatter electron detector.
Sources/Usage: Public Domain. View Media DetailsA rock crust thin section obtained from the Amarigosa Desert Research Site (ADRS) Grid Area (impregnated with a blue epoxy). The photomicrograph is obtained with a crossed polarized light illumination. Crust exhibits porosity (shown as a blue color in the interior of the section) and a complex layered mineral structure. Scale marker is at the lower right hand corner of the photomicrograph. - Science
Aqueous Crystal Growth and Dissolution Kinetics of Earth Surface Materials
Although calcium carbonate reaction kinetics has important application in several areas of Earth Science, the mechanism of natural organic matter mediation of carbonate minerals growth and dissolution rates remains largely unknown. This project uses multiple approaches to study calcium carbonate formation and dissolution rates in surface water and groundwater systems.