USDA-NRCS Geochemistry Research and Future Directions M.A. Wilson, R. Burt, S.W. Waltman, and M.D. Mays

OBJECTIVES Pedon characterization data at USDA- NRCS Soil Survey Laboratory(SSL) Current and future trace element work in NRCS Soil mapping/representative pedon approach to trace element distribution in soils Discuss:

USDA-NRCS Soil Survey Laboratory Located in the National Soil Survey Center, Lincoln, NE Performs a wide variety of soil analyses for research, characterization, classification, and interpretations Analyses performed on each soil horizon in a pedon

Soil Observation and Measurement USDA NRCS manages the National Soil Survey Laboratory Characterization Database 1940’s through the present Contains about 30,000 soil sampling sites, or pedons Many have morphological (profile descriptions) About 1,000 pedons from other countries About 75 percent are geo-referenced

These pedons are regarded as representing the properties and behavior of the series/mapping unit.

STATUS - NRCS TRACE ELEMENT PROGRAM 513 pedons (Benchmark, anthropogenic, other important soils) 2105 samples (major horizons, satellite samples) 50 states, Puerto Rico, Virgin Islands, Guam Morphological description, characterization data, georeference location Two digestions/sample: Major, Trace

GEOCHEMISTRY PROJECTS Agricultural Waste - KS, CO, UT, NE, VA, OH Mining - Emissions (MT) Surface Mine (KS) Urban - MD, NY, CT, ME, NJ, CA Munitions Disposal - NV Native - OR, WY, NV

Reported Elements HF+HNO 3 +HCl (EPA Method 3052): Si, Al, Fe, Mn, Ca, Mg, Na, P, K, Zr, Ti HNO 3 +HCl (EPA Method 3051A): Cu, Zn, Cd, Pb, Ni, Cr, Co, Hg, Mn, P, Fe, Ba, Be, Sr, Sb, Ag, As, Se, (Mo, V, Sn, Tl, W)

DIGESTION FOR TRACE ELEMENTS 500 mg soil (<200 mesh) 9 ml HNO ml HCl Microwave digestion (175  C for 4.5 min) Cold Vapor AA - Hg Flow-through hydride AA - As, Se ICP-AES- Other elements

Pedon Locations for Trace Element Data

SAMPLING/ANALYSIS OF MAJOR PEDOGENIC HORIZONS Evaluate pedogenic redistribution (e.g., biocycling, mobility via organo-metallic complexes, solubilization) Evidence of anthropogenic accumulation in surficial horizons Maximize data utility

SPECIATION IN SELECTED SMELTER-CONTAMINATED SOILS IN ANACONDA AND DEER LODGE VALLEY, MONTANA, USA Fractionation by Selective Dissolution

Proposed Web Access for Trace Element Data

Benchmark pedon samples Available (red)

MINIMUM FIELD DATA SET (based on current approach) Choose representative site Identify soil type Georeference location Sample (minimum) 3 major horizons; possibly satellites Site and Morphological documentation

MINIMUM LABORATORY DATA SET Major and Trace elements pH Particle Size Analysis Total C Selective dissolution (e.g., citr. dith, acid ox.) Cation exchange capacity Bulk density

Soil Survey and Use of Representative Pedons (RP) Important factors Mapping scale Mapping/classification (stratification) criteria Purity and uniformity of mapping units Property transitions (boundary) between units Effective classification is more important than choosing representative pedons for improving prediction (Leenhardt et al., 1994)

Fine, mixed, semiactive, thermic Typic Paleaquults Fine, mixed, semiactive, thermic Plinthic Paleaquults

McBratney et al., 2000

CONCLUSIONS SSL performs geochemical analysis on a pedon/horizon basis for background and anthropogenic accumulations. Use of Representative Pedons (RP) is a likely approach for documenting soil geochemistry across landscapes.

CONCLUSIONS RP’s will assures best incorporation of data into existing NRCS soil survey data structure. Merging a scheme of soil/landscape models with geostatistics may be viable.