Cadmium and associated metals in soils and sediments of wetlands across the Northern Plains, USA

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. •Cd concentrations in wetland soils average 0.0034 ± 0.0015 μmol g−1.•Minnesota shallow lakes show wider range in Cd concentrations than prairie potholes.•Cd in prairie potholes varies between Level III Ecoregions.•Cd in wetlands is associated with Zn and P.•Cd in wetlands seems associated with geology, hydrology, and land use. A comprehensive study on the distribution of cadmium in diverse wetlands across a large region varying in landscape and land uses.