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Cadmium, present locally in naturally high concentrations in the Northern Plains of the United States, is of concern because of its toxicity, carcinogenic properties, and potential for trophic transfer. Reports of natural concentrations in soils are dominated by dryland soils with agricultural land uses, but much less is known about cadmium in wetlands. Four wetland categories – prairie potholes, shallow lakes, riparian wetlands, and river sediments – were sampled comprising more than 300 wetlands across four states, the majority in North Dakota. Cd, Zn, P, and other elements were analyzed by ICP-MS, in addition to pH and organic matter (as loss-on-ignition). The overall cadmium content was similar to the general concentrations in the area’s soils, but distinct patterns occurred within categories. Cd in wetland soils is associated with underlying geology and hydrology, but also strongly with concentrations of P and Zn, suggesting a link with agricultural land use surrounding the wetlands.

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The carcinogenic potential of erionite has sparked concern about human exposure in areas where it is present in regional bedrock. The Arikaree Formation in western North Dakota contains altered tuffaceous units with authigenic zeolites. We sampled stratigraphic profiles in the Killdeer Mountains, Dunn County, North Dakota, to determine the distribution and chemical composition of zeolites. Powder X-ray diffraction, SEM/EDS and electron microprobe analyses were carried out on sample concentrates. Only samples stratigraphically in or below the distinctive burrowed marker unit were found to contain zeolites. Erionite and offretite were the most common zeolites identified, with offretite being more abundant based on frequency of measured Mg/(Ca+Na) ratios. Intermediate chemical compositions could be natural or due to intimate intergrowths of the two minerals. A better understanding is needed of the potential toxicity across the range of erionite and offretite compositions.