|Van Pelt, Robert - Scott|
Submitted to: Catena
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/24/2006
Publication Date: 8/1/2007
Citation: Van Pelt, R.S., Zobeck, T.M., Ritchie, J.C., Gill, T.E. 2007. Validating the use of 137cs measurements to estimate rates of soil redistribution by wind. Catena. 70(3):455-464.
Interpretive Summary: 137Cesium (137Cs)tagged soil particles have been used by numerous researchers to quantify rates of erosion and deposition of soils by water. Very few studies have utilized this technique to quantify rates of erosion of deposition of soils by wind. To date, no studies have compared the rates predicted by 137Cs based models to actual physical measurements of erosion and deposition by wind. The USDA-ARS Big Spring Field Station has a series of fields with well documented histories of wind erosion and deposition. We performed this study to determine whether or not 137Cs inventory based models could be used to accurately estimate the rate of erosion when compared to actual physically measured rates and what calibration factors would be necessary for the highly erodible soils of the Southern High Plains region of Texas.
Technical Abstract: Wind erosion has degraded over one-half billion hectares of land worldwide. 137Cs has been used as a tracer to study long-term water erosion and sedimentation trends and, to a lesser extent, to study wind erosion rates. These studies assume that the decline in 137Cs activity for a potentially eroded soil relative to that for an uneroded soil is proportional to soil loss. While this may be the case for relatively non-selective rill erosion caused by water, wind erosion is a selective process that tends to remove the finer portions of the soil that are the sites of 137Cs binding. Therefore, declines in 137Cs concentration may tend to overestimate soil loss due to wind erosion. We investigated the partitioning of 137Cs in wind eroded sediments and with soil surface samples sieved into contiguous ranges of particle sizes. We also compared the 137Cs activities and stratification of several adjacent soils with known wind erosion and deposition histories. We also tested and calibrated soil loss models that correlate 137Cs inventories with estimated soil loss rates using measured data of erosion and deposition from sites with documented histories. 137Cs activities and mean diameters of samples captured at different heights above the surface during an aeolian event indicated increasing 137Cs activity and decreasing particle size with increasing height above the surface and agreed well with the 137Cs activities and respective mean diameters of the sieved surface soil samples. Higher 137Cs activities and smaller mean particle diameter of post-1954 attic dust and tractor air cleaner dust suggests further enrichment of 137Cs concentration with decrease in particle size. Good agreement between model estimations and measured data indicated that 137Cs models developed to estimate water erosion and deposition were also applicable to wind erosion provided that the models contained a particle size correction parameter that accounts for selective soil loss of smaller particle sizes and deposition of larger or smaller particle sizes than the median particle size for the source soil.