Soil Geochemistry Spatial Database - General Description

The USDA-NRCS Soil Geochemistry Spatial Database contains data collectively produced by the National Cooperative Soil Survey Program. Sites were generally selected and sampled by soil survey personnel in respective states. Laboratory data were produced by the USDA-NRCS Soil Survey Laboratory, located in the National Soil Survey Center, Lincoln, NE.

The geographic display consists of two major sets of geochemistry data:

1. Current Geochemistry Project— This project is ongoing and the website is updated periodically to reflect additional available data. Pedons were sampled and analyzed by horizons. Pedons represent either the central concept of a soil series, the central concept of a map unit, or unspecified sites on a project specific basis. These data include both sites that are contaminated and non-contaminated. Currently the database contains data for over 800 pedons and 3000 samples. These data are displayed in four geographic layers: Site Info, Major Elements, Trace Elements, and Selected Characterization Data. Data in Major Element and Trace Element tiers are defined by specific digestion methods rather than soil concentration. Digestion method for elements in the “Major Elements” tier consists of an acid combination of HF+HNO₃+HCl. Elements in the “Trace Element” tier are recovered from soil with a HNO₃+HCl digestion. Elemental data are incomplete on certain samples. We have added additional elements to the analytical suite over time and certain data are absent on earlier projects. Also, certain projects were specific for only major or trace elements.

   Summary and analysis of these data are documented in:

   Burt, R., M.A. Wilson, M.D. Mays, and C.W. Lee. 2003. Major and Trace Elements of Selected Pedons in the U.S. J. of Environ. Qual. 32:2109-2121.

   For detailed information on SSL methods (e.g., procedures, interferences), refer to web site: Soil Survey Investigation Report 42.

   Information on the applications of laboratory data, reference: Soil Survey Investigation Report 45.

   For additional qualifications and limitations on the regarding characterization data, refer to the SSL laboratory data website http://soils.usda.gov/soil_survey/nscd/index.html.

   You are most WELCOME to use the database, but you should be aware that the assessment of the accuracy and applicability is strictly a USER RESPONSIBILITY and the NRCS and NCSS take no responsibility for problems that arise from use of these data.

   Locations in the past were recorded only as latitude and longitude in the Soil Survey Laboratory Characterization Database. Therefore, georeference locations for sites can be considered only approximate unless the map datum (NAD27, WGS84) can be identified for each point. It can be assumed that data prior to 1990 was recorded from maps with a NAD27 basis, and with a WGS84 basis after 1995.

2. Holmgren Dataset--A second group of data was produced by the Soil Survey Laboratory during the 1970’s and 1980’s for a project documenting the content of selected trace elements in agricultural soils of the U.S. This dataset contains over 3,400 sites in conterminous U.S. These data are available as a separate spatial layer on a county centroid basis.

   These data are discussed in:

   Holmgren, G.G.S., M.W. Meyer, R.L. Chaney, and R.B. Daniels. 1993. Cadmium, lead, zinc, copper, and nickel in agricultural soils in the United States of America. J. Environ. Qual. 22:335-348.

For information regarding the analytical procedures and data, contact:

Michael A. Wilson, Ph.D.
Research Soil Scientist
USDA-National Soil Survey Center
Soil Survey Laboratory
100 Centennial Mall N., Rm. 152, MS 41
Lincoln, NE 68508-3866
Phone: 402-437-4134
FAX: 402-437-5760

Or

Rebecca Burt. Ph.D.
Research Soil Scientist
USDA-National Soil Survey Center
Soil Survey Laboratory
100 Centennial Mall N., Rm. 152, MS 41
Lincoln, NE 68508-3866
Phone: 402-437-5133
FAX: 402-437-5760

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