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 Kellogg Soil Survey Laboratory, located in the National Soil Survey Center, Lincoln, NE. This current version of the website was completed in August 2009 and reflects all geochemistry data produced as of that time.

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

1. Current Geochemistry Project— The Soil Geochemistry Spatial Dataset is a collection of soil geochemistry data produced by the U.S. Department of Agriculture, Natural Resources Conservation Service, Kellogg Soil Survey Laboratory in Lincoln, Nebraska. The website is ongoing and updated periodically to reflect additional available data. Soil 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. Sites are indentified as either contaminated or non-contaminated (cited as “unknown”) based on knowledge of land use history. When labeled as “unknown”, it suggests the elemental concentrations represent native values. These data are represented in four layers: Site Info, Major Elements, Trace Elements, and Selected Characterization Data. Data in Major Element and Trace Element tiers are defined by specific digestion. Digestion method for elements in the “Major Elements” tier consists of an acid combination of HF+HNO3+HCL. Elements in the “Trace Elements” tier are recovered from soil with a HNO3+HCL digestion. Elemental data are incomplete on certain samples. Additional elements have been added 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.
   
   Currently, the dataset contains data for over 1,400 sites, and greater than 4,800 and 6,000 samples with trace and major elemental data, respectively. Each point or location on the map represents one or more pedons. Data for pedons generally include multiple horizons listed sequentially in a tabular format. Each location has four types of data associated: site, trace element, major element, and characterization data. For certain sites, only trace or major elemental data may be available. Fields without data are filled with “-99999”, and data below detection limits is shown as “-11111”.
   
   The Soil Geochemistry Spatial Dataset 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 U.S. Department of Agriculture, Natural Resources Conservation Service, Kellogg Soil Survey Laboratory, located in the National Soil Survey Center, Lincoln, Nebraska.
   
   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.
   
   Wilson, M.A., R. Burt, S.J. Indorante, A.B. Jenkins, J.V. Chiaretti, M.G. Ulmer, J.M. Scheyer. 2008. Geochemistry in the modern soil survey program. Environmental Monitoring and Assessment. 139:151–171

   For detailed information on Kellogg Soil Survey Laboratory (KSSL) methods (e.g., procedures, interferences), refer to “Soil Survey Laboratory Investigations Report No. 42” accessed at http://soils.usda.gov/technical/lmm/.
   
   For information on the applications of laboratory data, refer to “Soil Survey Laboratory Investigations Report No. 45” accessed at http://soils.usda.gov/survey/nscd/lim/index.html.
   
   For the complete characterization data dataset, pedon and site information, additional qualifications and limitations on the regarding characterization data, refer to the National Cooperative Soil Survey Soil Characterization Database at http://ncsslabdatamart.sc.egov.usda.gov.
   
   Locations of each site are identified as either “Geographic”, a known location identified by latitude and longitude or “Centroid”, the location is unknown within county and the point on the map is located at the latitude and longitude of the county centroid. Note that 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 or WGS84) can be indentified for each point. It can be assumed that data prior to 1990 was recorded from maps with a NAD27 datum and with a WGS84 datum 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.

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.

Use Constraints

The U.S. Department of Agriculture, Natural Resources Conservation Service and the National Cooperative Soil Survey, should be acknowledged as the data source in products derived from these data.

This dataset is not designed for use as a primary regulatory tool in permitting or citing decisions, but may be used as a reference source. This is public information and may be interpreted by organizations, agencies, units of government, or others based on needs; however, they are responsible for the appropriate application. Federal, State, or local regulatory bodies are not to reassign to the Natural Resources Conservation Service or the National Cooperative Soil Survey any authority for the decisions that they make. The Natural Resources Conservation Service will not perform any evaluations of these data for purposes related solely to State or local regulatory programs.

Digital data files are periodically updated. Files are dated, and users are responsible for obtaining the latest version of the data.

Process Description

A SQL query was used to select data from the Laboratory Information Management System (LIMS). The selected data were extracted and imported to Microsoft Office Excel 2003. The Microsoft Office Excel Workbook was saved as a DB$ 4 (dBASE IV) file type. The dBASE file was added to ArcMap 9.2, with x defined as Long DD and y defined as Lat DD. Coordinate system of input coordinates was established as Geographic Coordinate System GCS North American 1983 and an event file created. The event file is exported as a shapefile. A feature dataset was created in ArcCatalog. The FeatureClass to Geodatabase tool was used to convert the event shapefiles to geodatabase feature classes.

For information regarding the analytical procedures and data, contact:

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