USGS - science for a changing world

Ground Water Chemistry

Aqueous Crystal Growth and Dissolution Kinetics of Calcium Carbonate Minerals - Project Activity at the Amarigosa Desert Research Site (ADRS), Beatty, Nevada

Michael M. Reddy

Homepage

Welcome

Project Staff

Activities for Teachers and Students

Research Activities

Project Activity at the USGS Toxics Program Research Site, the Amargosa Desert Research Site (ADRS), near Beatty, Nevada

Projects Safety Activities

Amargosa Desert Research Site (ADRS), Beatty, Nevada


Calcium Carbonate Reactions in Arid Soils at the Amargosa Desert Research Site (ADRS) Located Near Beatty, Nevada

A rock crust thin section obtained from 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 (photo by Michael Reddy)

A rock crust thin section obtained from 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 (photo by Michael Reddy)

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 (Webb, R.M.T., Linard, J.I., and Wieczorek, M.E., 2006, The Water, Energy, and Biogeochemical Model (WEBMOD): A TOPMODEL Application Developed Within the Modular Modeling System, in Proceedings of the 3rd Federal Interagency Hydrologic Modeling Conference, Reno, NV, April 2-6, 2006, ISBN 0-9779007-0-3.) WEBMOD 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, to 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.

Environmental 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 (photo by Michael Reddy)

Environmental 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 (photo by Michael Reddy)
ADRS Grid Contours NAIP
ADRS Gride Area

Accessibility FOIA Privacy Policies and Notices

Take Pride in America logo USA.gov logo U.S. Department of the Interior | U.S. Geological Survey
URL:http://wwwbrr.cr.usgs.gov/projects/GWC_Crystal/ADRS.html
Project Contact Information:Michael M. Reddy
Page Contact Information:Charmaine Gunther
Page Last Modified: April 27, 2015