Concentrations of Six Trace Metals in Some Major Minnesota Soil Series
1982
Pierce, F. J. | Dowdy, R. H. | Grigal, D. F.
Concentrations of Cd, Cr, Cu, Ni, Pb, and Zn were determined in 16 soil series in Minnesota to establish baseline levels of these trace metals. These soils are representative of those formed on seven major parent materials in the state and comprise a broad range of soil properties. Extracts with 0.1M K₄P₂O₇·3H₂O, 1.0NW HNO₃, and a concentrated HCl-HNO₃-HF acid mixture were used to characterize the soils for organically bound, “biodiagenetically” available, and total metal content, respectively. Total metal contents were in the lower portion of ranges reported in the literature and represented levels naturally present in uncontaminated soils. Total Cd, Cr, Cu, Ni, Pb, and Zn averaged (± SD) 0.31 (±0.21), 43 (±28), 26 (±9), 21 (±14), <25, and 54 (±18) µg/g, respectively. The average extraction efficiency of HNO₃ for total metals was highest for Cd (52 ± 19%) and the lowest for Cr (14 ± 7%). The predominate trend in both available and total metal content showed highest concentrations of Cd, Pb, and Zn in the surface soil and highest concentrations of Cr, Cu, and Ni in subsoil and parent materials. Cadmium was often higher in soils containing free carbonates. Concentrations of organically bound metals in soil were very low, and, with the exception of Cu, were usually negligible below the surface layer. Differences in metal content among soils were believed due to differences in the parent materials. Variations within soil series were low, with genetic horizons showing narrow ranges in HNO₃-extractable metals.
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