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United States Department of Agriculture

Agricultural Research Service

Research Project: QUANTIFYING LANDSCAPE FACTORS INFLUENCING SOIL PRODUCTIVITY AND THE ENVIRONMENT Title: Sediment source determination using fallout Cesium-137 in arid rangelands.

Authors
item Ritchie, Jerry
item Rhoden, Fred - USDA SED. LAB OXFORD, MS
item Nearing, Mark - ARS SW WTRSHD. RES. CNTR.

Submitted to: International Atomic Energy Agency Proceedings on Radioisotopes
Publication Type: Abstract Only
Publication Acceptance Date: September 20, 2007
Publication Date: N/A

Technical Abstract: Sediment source identification in arid rangelands is necessary to understanding rangeland conditions and developing management practices to improve rangeland health and reduce sediment load to streams. The purpose of this research was to use Cesium-137 to identify sources of sediments in an arid rangeland watershed. Soil samples from subwatersheds on the Walnut Gulch Experimental Watershed (WGEW) near Tombstone, Arizona were sampled in either a grid pattern or along transects associated with soils and geomorphology. Suspended sediments samples were also collected at stream measuring sites for the subwatersheds. At each sampling point, latitude, longitude, slope gradient, slope aspect, and hillslope position were recorded. Soil samples collected from the surface 5.0 cm were characterized for a range of basic physical, chemical, and mineralogical properties as well as Cesium-137 and K-40. Suspended sediment samples collected at flume sites along the Walnut Gulch Experimental Watershed were also analyzed. Generally, the suspended sediments were enriched in silt, clay, organic C, and K-40. The suspended sediments were enriched in Cs-137 in some but not all of the subwatersheds. Analyses of the data indicated that three of the subwatersheds were contributing most of the suspended sediments that was measured at the mouth of the Walnut Gulch Experimental Watershed.

Last Modified: 12/22/2014
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