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The National Uranium Resource Evaluation (NURE) program of the Department of Energy (DOE) collected a vast amount of chemical data on sediment, soil, and water from the United States in the late 1970's and early 1980's. This element of the NURE program was known as the Hydrogeochemical and Stream Sediment Reconnaissance (HSSR). The NURE HSSR data have long been available to the public in a variety of formats, ranging from the original paper reports produced by the DOE (Averett, 1984), to comprehensive digital releases on CD-ROM by the U.S. Geological Survey in the last few years (Hoffman and Buttleman, 1994; 1996), to digital releases on the Internet of reformatted and cleaned data (Smith, 1998). While these publications remain the best sources of the complete, primary data, and are accompanied by documentation of the sampling protocols, sample characteristics, and analytical methods, they are difficult to use for geochemical research, especially when the study area covers a large part of the United States. This publication is intended to allow the rapid visualization of the geochemical landscape of the United States using the NURE HSSR data. Here, the user is relieved of the responsibility of selecting and processing the raw data.
Database field Sediment codes Soil codes
----------------------------------------------
SAMPLE 2.x or 2.xx 3.x
SAMPMDC 4
LTYPC M
SAMPTYP 11,12,13,14,15 58,59
37,50,55,60,61,
63,64,70,71,72,
73,96,97,99
After surveying each file (through a series of Paradox
queries), a new query was constructed that extracted all
records for stream sediments (wet and dry), lake and pond
sediments (including dry lakes), spring sediments, and soils.
1.2 Field selection
Data fields were chosen from the selected records for further
processing. These included several label fields, the sample-
type fields listed in Table 2, the geographic coordinates,
fields for the 54 chemical elements appropriate for solid
samples (Ag, Al, As, Au, B, Ba, Be, Bi, Ca, Cd, Ce, Co, Cr, Cs,
Cu, Dy, Eu, Fe, Hf, Ho, K, La, Li, Lu, Mg, Mn, Mo, Na, Nb, Nd,
Ni, P, Pb, Pt, Rb, Ru, Sb, Sc, Se, Si, Sm, Sn, Sr, Ta, Tb, Th,
Ti, U, V, W, Y, Yb, Zn, Zr), and 5 miscellaneous fields that
contain chemical data (CONCN01 through CONCN05). A Paradox
query extracted these fields, and all other data were
discarded (including things like stream characteristics,
contamination codes, various labels, and fields not used for
solid sample media).
1.3 Data scaling
Most chemical data in the quadrangle DBF files are stored in
parts-per-billion (ppb). Paradox was used to convert each field
into a more appropriate unit: parts-per-million (ppm) for trace
elements, and weight percent for major elements (Al, Ca, Fe, K,
Mg, and Na).
1.4 Record consolidation
Many samples were analyzed by more than one laboratory, or by
more than one method. In these cases, there are multiple
records in the quadrangle DBF files for an individual sample
location, each with analyses for different elements. These
records were found and combined into a single record.
Paradox was used to sort the records by latitude and longitude.
A temporary DBF file was generated, and read by a DOS FORTRAN
program, ECLEAN, written by the author (unpublished). This
program searched for consecutive records that had identical or
nearly identical geographic coordinates (within 0.0005 degrees,
or ~50 m, of each other). These were assumed to be the same
sample, as round-off errors sometimes affected the 4th decimal
place. ECLEAN then combined these records, element by element,
into a single new record. In the few cases where data for the
same element was present in two or more records, the highest
value was arbitrarily chosen. This process also had the effect
of consolidating samples actually collected as duplicates at a
single location into single records. ECLEAN also eliminated
records with no chemical data (and there were many of these).
The program then created a new DBF file with the consolidated
data.
Secondary data processing
At the beginning of this processing stage, the 308 original
quadrangle DBF files have been reduced to 308 new DBF files
containing only the geographic and chemical-element fields of
the sediment and soil data, without any duplicate or blank
records. Major systematic problems, as discussed above, have
been corrected. The following processing steps were used to
find and correct additional problems in the datasets, to search
for regional inconsistencies in the data, and to establish the
usefulness of data reported as upper limits ( for example <10
ppm).
2.1 Data surveying
The reduced DBF files were surveyed with a DOS FORTRAN program,
also written by the author, called GRIDPLOT. This program
reads in multiple DBF files, and produces a simple, color,
gridded map of the data for one element on the computer screen.
Systematic errors that were not found during primary data
processing could be seen visually, as discontinuities in the
colored map. In some cases, these could be traced to
systematic errors in the quadrangle DBF files, especially
errors in the position of decimal points. These were corrected
by repeating the primary processing for the affected
quadrangle. Other discontinuities are caused by analytical
errors, and were handled through the data leveling procedure
described next.
2.2 Data leveling
In some areas, generally in the western U.S., one or more
quadrangles, or parts of quadrangles, would appear to be
discontinuous with adjacent quadrangles for a given element,
when viewed with GRIDPLOT. In many such instances, a good case
can be made that there is a systematic analytical error (that is,
an accuracy problem, probably due to different analytical
methods or interlaboratory calibration problems) across the
discontinuity. The best argument for the occurrence of this
type of error is that regional chemical trends are seen on both
sides of the discontinuity, and the application of a simple
correction factor can make the data appear continuous. In
these cases, a correction factor is supplied to GRIDPLOT for
the affected areas, and the factor is adjusted until the
gridded map appears smooth and continuous. In other cases,
either no correction factor can correct the discontinuity, or
regional trends are absent in certain quadrangles and the data
appear to be random. Such data were discarded and not used to
produce these images.
2.3 Data below detection limits
A negative concentration of an element in the quadrangle DBF
files indicates that the value is an upper limit (for example
-10 means <10). These values present a special problem in
creating map coverages of geochemical data. The philosophy
adopted here is simple: steps were taken to ensure that all
such upper limits fall within the lowest interval in the final
map legend, and thus are known to be correctly categorized.
First, two histograms were prepared for each element, one
showing the concentration range of unqualified data, the other
showing only upper limits. For most elements, the vast majority
of the data fell in the first histogram, and markers were
inserted into this plot showing the values of every 5th
percentile (for reference). The second histogram was displayed
below the first and compared visually. The strategy was to
select a cutoff value below which upper limits are to be
retained, such that they do not affect the accuracy of the map.
Above this cutoff value, upper limits are deleted from the final
dataset. The graphical result of deletions of this type are
small holes in the map where grid cells could not be assigned
real values.
2.4 Data extraction
Once the data were leveled, upper limit cutoffs were
established, and areas of bad data were identified, the
GRIDPLOT program was run again to extract values for a single
element from all 308 processed quadrangle DBF files. For the
special case of uranium, GRIDPLOT was programmed to make
choices about which data field to use for the final value.
Uranium is typically stored in one of five fields in the
original quadrangle DBF files: one labeled as CONU, the others
as CONCN01, CONCN02, CONCN05, and CONUDN. The CONC05 field was
given priority over the CONU field if both were filled, and
data in the CONCN01 and CONCN02 fields were used in the absence
of data in the first two fields. The CONUDN field (U by
delayed neutron) was only coded in few percent of the samples (
in only 9 quadrangles), but these data were not used here. The
output from this data processing step is a series of elemental
DBF files of useable NURE data.
Major errors corrected
Several major errors in the NURE HSSR data were identified and
corrected during the above data-processing steps. These errors
are present in the original DBF files and composite database of
Hoffman and Buttleman (1994; 1996). The errors will be
corrected in the a new database (Smith, 1998), but as of this
time only a small part of the United States is covered by this.
3.1 Miscoded samples
The data survey conducted for each quadrangle DBF file in step
1.1 uncovered a block of stream-sediment samples miscoded as
stream water in seven quadrangles in the northeastern U.S.
(Boston, Glen Falls, Lake Champlain, Lewiston, Newark, Scranton,
and Williamsport). These records were altered to give them the
correct coding prior to any data processing.
3.2 Data in incorrect units
In about 30,000 samples collected and analyzed by Oak Ridge
Gaseous Diffusion Plant (ORGDP) and tabulated in the quadrangle
DBF files, major elements (Al, Ca, Fe, K, Mg, and Na) plus As
and Se were all tabulated incorrectly, in units other than ppb.
Over 70 quadrangles contain data affected by this problem.
These records can be identified from the lack of coding in the
SAMPTYP field, and a value of 4 coded in the SAMPMDC field.
These problems were corrected as a group.
About 15,000 records found in several dozen quadrangles in the
western U.S. (samples analyzed but not collected by ORGDP) also
contain major element data in ppm instead of ppb, although
trace elements are all coded correctly. Most of these are
coded as soils (SAMPTYP=59), talus (SAMPTYP=62), or uncoded
in this field (SAMPTYP=blank), and all have a value of M coded
in the LTYPC field, which stands for sediment. These were
also corrected by special handling.
Data products
Themes with names of the form Grid: Cu are elemental
concentration maps, produced from a gridded version of the
point data. These bitmap files (TIFF) are based on grids made
with the MINC program of Webring (1981), which employs a
minimum curvature interpolation of the point data to create a
smooth surface. The grid-cells used were 2 km on each side.
Person who carried out this activity:
Are there legal restrictions on access or use of the data?Access_Constraints: None
Use_Constraints:The U.S. Geological Survey makes no warranties related to the accuracy of the data and users are required to determine the suitability of use for any particular purpose.
The U.S. Geological Survey (USGS) provides this vector data as is. The USGS makes no guarantee or warranty concerning the accuracy of information contained in the raster data. The USGS further makes no warranties, either expressed or implied as to any other matter whatsoever, including, without limitation, the condition of the product, or its fitness for any particular purpose. The burden for determining fitness for use lies entirely with the user. Although this data has been processed successfully on computers at the USGS, no warranty, expressed or implied, is made by the USGS regarding the use of this data on any other system, nor does the fact of distribution constitute or imply any such warranty.
| Data format: | Map images showing element concentration in format TIFF (version 6.0) Size: 8.5 |
|---|---|
| Network links: |
https://mrdata.usgs.gov/nure-hssr/nure.zip |