ARS | Publication request: OCCURRENCE OF TRACE-ELEMENT-RICH SOILS NEAR THE PEMBINA ESCARPMENT, CAVALIER COUNTY, NORTH DAKOTA

Submitted to: North Dakota Academy of Science Proceedings
Publication Type: Proceedings
Publication Acceptance Date: November 1, 1999
Publication Date: N/A

Technical Abstract: Many trace metals (Cd, Cr, Cu, Ni, Mo, V, etc.) are found in relatively high concentrations in marine shales, such as those which underlie all of eastern North Dakota & have been incorporated into glacial drift to varying degrees. From an agricultural perspective, the rationale for trace metal studies of soils is often to assess the need for micronutrient fertilizers, ,but food quality is important also. In a recent study of prairie soil A horizons, Garrett reported that the mean total Cd concentration of 1273 soils from the prairie provinces of Canada and adjoining areas in the U.S. was 0.28 ppm, and he suggested an environmental baseline of 0.3 ppm. Analyses of trace elements in 167 samples of agricultural soils from our detailed survey of northwestern North Dakota have shown similar concentrations of Cd, with a mean, median, and range of 0.34 ppm, 0.32 ppm, and 0.20 to 0.72 ppm. These concentrations are within the normal range for Cd in soils. In Cavalier County, certain locations show anomalously high concentrations of several trace elements. The A horizon concentrations of several elements, including Cd, in these soils are 10 to 20 times higher than the concentrations typical of other soils of the region. In these soils, which formed in clay-rich till or colluvium derived from shale, several samples exceeded 5 ppm Cd in the surface and remained high in the subsoils. The presumed source of these trace metals is the Pierre Shale, which is exposed at the surface in the Pembina Escarpment where not covered by a veneer of till. High cadmium in the soil contributed significantly to high extractable Cd. Neither soluble nor total organic matter had much effect on extractable cadmium, so the levels could be predicted from a relatively simple model based on only pH and total cadmium in the soil.