Tuesday, 8 November 2005 - 2:00 PM
166-3

Evaluation of Sediment Transport Mechanics Using Lanthanide Tracers and Radiometric Fingerprinting.

Paul Miller1, K.G. Karthikeyan1, Joseph Grande1, Phil Gaebler1, Seth McClure1, Peter Whiting2, Andrew Stubblefield2, and Gerald Matisoff2. (1) University of Wisconsin, 460 Henry Mall, Biological Systems Engineering Department, Madison, WI 53706, (2) Case Western Reserve University, 10900 Euclid Avenue, Geological Sciences, Cleveland, OH 44106

A fully integrated hill-slope scale hydrologic monitoring project has been initiated to evaluate sediment transport mechanisms by combining a network of surface runoff sensors monitoring the temporal and spatial occurrence of runoff with radiometric (Be-7, Pb-210, Cs-137) fingerprinting and lanthanide (rare earth element (REE) oxides) tracer analysis. These methods have been combined on a hill-slope with a Plano silt loam soil texture (Arlington, WI) under two tillage orientations planted on the contour and planted downslope. The runoff sensors contain an IC chip design comprised of a voltage regulator and a hex Schmitt trigger. The sensor operates in a current loop calibrated to be 4 mA when no water is present and 20 mA when water bridges a section of the circuit mounted on precision laser-cut steel mounts located in critical areas in the field. The current loop is calibrated with two potentiometers built into each individual sensor circuit board. The voltage drop across that resistor is measured using a Campbell CR 21X data logger controlling an AM416 multiplexer. Characterization of areas of soil erosion will occur by application and monitoring of REE oxide-tagged soils and measurement of changes in Be-7 inventory. An optimal hillslope length (36 ft from edge-of-field) will be divided into three segments within which different types of soil-REE (Gd, Nd, Pr) oxide mixtures will be placed. While the migration of labeled soils will be used to quantify sediment transport rates and distances and delineate source areas, radiometric fingerprinting will help elucidate underlying erosion mechanisms. Monitoring the redistribution of REE-tagged soils will quantify the source regions of suspended sediment and characteristic transport distances. Radiometric fingerprints using concurrent measurements of multiple environmental isotopes will be used to determine relative areal extents of the hillslope subjected to interrill vs. rill erosion.

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