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The analysis of samples of big sagebrush from 190 sites in 8 western physiographic provinces resulted in measurable concentrations of 30 elements. Except for Sb, U, and V, whose concentrations were generally below the analytical detection limits, the expected (baseline) concentration range of each element was defmed. The variability in the concentration of Ba, Ca, Li, Pb, Se, Sr, and Zn among the 8 provinces was found to be nonsignificant and therefore a mean and deviation (for all provinces combined) for these elements was used to define their baseline. For concentrations of 20 of the elements (including the environmentally important metals As, Cd, Cr, Co, Cu, Hg, and MO), significant variability was found among provhrce populations so that baseline values are reported for each province or group of provinces. Physiographic provinces were incorporated in the study design as a convenient natural unit in presenting the element baselines and we anticipate that these data may be useful in assessing biogeochemical changes brought about by the activities of energy development, mineral processing, and other anthropogenic disturbances. The major goal of this study is to establish baselines for the elemental composition of big sagebrush (Arremisiu rridenrata Nutt.) throughout the western U.S.A. Big sagebrush is one of the most widely distributed and easily recognized shrubs of this vast region and of southern British Columbia, Canada. The importance of this species as a component in natural ecosystems and in regions dominated by livestock production was the subject of a recent symposium (Utah State Univ., 1979). At the beginning of this study, baseline elemental composition data were seen as being useful primarily in assessing the consequences of energy development in the western U.S.A. Such activities include the surface-mining of coal and the attendant geochemical and biogeochemical changes following land reclamation (e.g., Munshower and Neuman 1980) as well as point-source contamination from coal-fired power plants and mineral processing facilities (e.g., Connor et al. 1976, Severson and Gough 1976). Elemental composition data, however, may be equally useful in evaluating contamination from natural events (e.g., the Mount St. Helens eruption) or assessing the value of sagebrush as a browse plant for livestock or for wildlife (e.g., Alvarez-Corder0 and McKell 1979, Welch and McArthur 1979). In addition, big sagebrush has had limited use as a sampling medium for geochemical exploration (Warren et al. 1949, Cannon 1952, Anderson and Kurtz 1956, and Erdman and Harrach 1981) and the data in the present report should be useful in helping to identify anomalous samples from potentially mineralized areas. The use of big sagebrush as a biogeochemical exploration medium is attractive not only because of its wide distribution but also because it grows in vast regions where alluvial and colluvial surfaces (as in the Basin and Range province) Authors are botanists, U.S. Geological Survey, Box 25046, Denver Federal Center, Denver, Co...

As part of the special interest series, Public Issues in Earth Science, published by the U.S. Geological Survey (USGS), this Circular describes the importance of the earth sciences in the investigation of environmental problems. The report focuses on geochemistry-the study of the amounts, distribution, and cycling of chemical elements in the Earth and atmosphere-and how this science helps to evaluate critical issues that relate to our fragile environment. The mission of the USGS is to provide geologic, topographic, and hydrologic information that contributes to the wise management of the Nation's natural resources and promotes the health, safety, and well-being of our people. Part of this task includes characterizing the Nation's geochemical environment and understanding the dynamic processes responsible for change in that environment. One of our greatest assets at the USGS is our long tradition of excellence in unbiased earthscience research. Part of that legacy is our commitment to supply the geochemical information necessary to confront urgent environmental challenges. Geochemistry provides information on the distribution of chemical elements to help us define and understand environmental problems. This information then allows us to provide answers for their resolution and possible remediation. This Circular presents an overview of geochemistry and its application to various case studies that illustrate the use of geochemistry in examining environmental problems. Some new and exciting areas of environmental geochemistry are discussed, involving r(.)ck/water, soil / water, and plant/ soil investigations. These investigations focus on many of our natural resources including minerals, soil, water, air, and vegetation and examine environmental concerns-such as acid precipitation, mine drainage, and sources of contamination-from a "systems" or "holistic" approach. As the primary Federal earth-science agency, the USGS leads in the collection, interpretation, and dissemination of earth-science information. This report helps to define one area in which the USGS is an active participant-the application of geochemistry to environmental concerns.

The modes of occurrence of extractable elements from 21 A and C horizon samples of uncultivated soils were examined using R‐mode factor analysis. The extractants (DTPA, EDTA, HCl, hydroquinone, magnesium nitrate, and ammonium oxalate) cover a wide range of chemical attack. Four major elements (Ca, K, Mg, and Na) and eight trace elements (Cd, Co, Cu, Fe, Mn, Ni, Pb, and Zn) were determined in each extractant solution. A variety of chemical, mineralogical, and physical variables were also determined on each sample. Four varimax factors (clay, organic, Fe and Mn oxides, and soluble‐Na) accounted for 74.2% of the total variance of the 90 variables for the A horizon. Seven varimax factors (Fe and Mn oxides, clay, CEC, soluble‐Na, organic, Fe and Mn, and plagioclase) accounted for 77.2% of the total variance of the 79 variables for the C horizon. A and C horizon extractable trace elements are most generally related to Fe and Mn oxides, as indicated by loadings on the Fe and Mn oxide factor for both the A and C horizons. Each extractant generally operates on different modes of occurrence of an element in soil. For example, substantial differences occur between the HCl‐, oxalate‐, and hydroquinone‐extractable trace elements. However, the modes of occurrence for trace elements removed by DTPA and EDTA were very similar, suggesting strong relationships between elements dissolved by these two extractants. The modes of occurrence for each individual major element are similar with each of the six extractants. A horizon Ca and Mg, and C horizon K and Mg are strongly related to a clay factor. C horizon Ca and A horizon K are strongly related to the CEC and organic factors, respectively. Both A and C horizon extractable Na are very strongly related to the soluble‐Na factor. These results suggest that extractable major elements are water‐soluble and are associated with the constituents that are responsible for that factor. Consequently, strong relationships should occur for any individual major element dissolved by any pair of extractants.

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