DETAILED INVESTIGATIONS OF SOIL GEOCHEMISTRY TO EVALUATE RADIOISOTOPE DISTRIBUTION IN PRAIRIE SOILS

Cesium-137 is becoming popular for measuring soil erosion; however, chemistry and soil properties can affect its distribution. Better knowledge of factors affecting the distribution of Cesium and other elements in soils is required to improve the accuracy of these soil erosion models. During 2000/2001, we initiated a study, using systematic sampling and detailed analytical techniques, to investigate soil parameters that may control the primary distribution of Cs-137, and other radioisotopes, in soils. .

Our hypothesis is that geologic variables in the soil and geomorphic positioning can produce predictable and systematic controls on isotope distribution. Our goals are to: 1) define spatial and vertical controls on the isotopic concentration (210Pb, 137Cs) in soil columns; 2) statistically identify variables controlling mobility and adsorption of these isotopes; 3) identify and evaluate other potential erosion “markers,” and 4) investigate new methods for sampling to define erosion index values for military training lands. We are integrating field and laboratory studies to examine the effects of soil processes and conditions, as well as landscape position, on the primary distribution of these markers in the soil profile. Field sampling highlights the diversity in landform type, soil characteristics, underlying geology, and surficial sediment type and composition. Samples are being collected from the Konza Prairie, an undisturbed tall-grass prairie reserve, and Fort Riley, which hosts extensive mechanized training. These two study sites allow us to look at differences between two geographically similar settings with drastically different historical use patterns. Detailed laboratory analyses will define patterns within major, minor, and trace elements, particle size, magnetic susceptibility, and organic content. The study will also look at sampling practices and evaluate new procedures for quantifying erosion and evaluating the development of new soil erosion indicators for military land managers. Our presentation will describe the conceptual design of the study, its goals, preliminary results, and plans for future work.