Fallout Cesium‐137 in Cultivated and Noncultivated North Central United States Watersheds

Abstract

Abstract The cesium ( 137 Cs) concentrations were measured in the soils and sediments of 14 watersheds, 7 cultivated and 7 noncultivated, in the North Central United States. The 137 Cs concentration in watershed soils ranged from 56 to 149 nCi/m 2 , with cultivated watersheds averaging 75 nCi/m 2 and noncultivated watersheds averaging 104 nCi/m 2 . The 137 Cs concentration in the reservoir sediments ranged from 74 to 1,280 nCi/m 2 , with a mean of 676 nCi/m 2 for the cultivated watersheds and 365 nCi/m 2 for the noncultivated watersheds. The 137 Cs concentrations per unit area in sediments were 0.8 to 18.7 times greater than those found in the contributing watershed soils. This indicated that some 137 Cs is moving within the watersheds and that the reservoirs are acting as “traps” or “sinks.” The factors accounting for the variation in 137 Cs concentration in the soils and sediments of the watersheds are (i) the erosion potential of the watershed, (ii) the sites for adsorption of 137 Cs, and (iii) the input of radioactivity into the watershed.