HR: 0830h
AN: H51C-09 [Abstracts]
TI: Fine-Scale Temporal Resolution of Sediment Source by Be-7
AU: * Stubblefield, A P
EM: aps12@case.edu
AF: Dept of Geological Sciences Case Western Reserve University, Rm 110 A.W. Smith Bldg
10900 Euclid Ave.
, Cleveland, OH 44106 United States
AU: Whiting, P J
EM: pjw5@case.edu
AF: Dept of Geological Sciences Case Western Reserve University, Rm 110 A.W. Smith Bldg
10900 Euclid Ave.
, Cleveland, OH 44106 United States
AU: Fondran, C L
EM: lorimor@darwin.epbi.cwru.edu
AF: Dept of Geological Sciences Case Western Reserve University, Rm 110 A.W. Smith Bldg
10900 Euclid Ave.
, Cleveland, OH 44106 United States
AU: Matisoff, G
EM: gxm4@case.edu
AF: Dept of Geological Sciences Case Western Reserve University, Rm 110 A.W. Smith Bldg
10900 Euclid Ave.
, Cleveland, OH 44106 United States
AB:
Understanding of erosional processes occurring at fine scales (cm) and over short time periods (min) in agricultural settings is essential for efforts to minimize landscape scarring, conserve surface nutrients, and reduce off-site impacts. Cosmogenic and fallout radionuclides have been successfully used in a variety of settings to determine sediment source and sediment
transport processes. In this study we used the short-lived radionuclide Be-7 (t1/2= 53 d) to investigate erosional
processes occurring during runoff from a 4 m by 9 m erosion plot. The plot was established in a 9.8% slope no-till corn
field at the USDA ARS Deep Loess Research Station in Treynor, Iowa. Before and after the rainfall, fine resolution soil
profiles were collected to determine the distribution of radionuclides and soil nutrients with depth. Be-7 was concentrated
near the soil surface. Prior to the rainfall event, rare earth tagged soil particles were applied in three discrete strips,
0.5 m wide, along the contour. Forty runoff samples were collected during the course of a 5.7 cm thunderstorm event. Runoff
efficiency was 25% and sediment yield was 0.234 kg m-2. Be-7 activities in runoff varied with hydrologic conditions and rainfall intensity, ranging from 0.06-0.6 Bq gm-1. Dominant erosional processes observed were rain splash erosion,
overland flow and rill transport. Be-7 rich sediment was delivered at times corresponding corresponded to peaks in rainfall
intensity, onset of overland flow, and development of hydrologic connectivity. Sediment had lower Be-7 activity during peak
sediment delivery, probably due to dilution by large volumes of Be-7 poor sediment derived from deeper rill erosion. Soil
tagged with the rare earth elements Ho, Tb, and Eu showed downslope movement in interrill areas, supporting conclusion of
rain splash and sheetflow erosive mechanisms.
DE: 1065 Trace elements (3670)
DE: 1815 Erosion and sedimentation
DE: 1860 Runoff and streamflow
DE: 1871 Surface water quality
DE: 1894 Instruments and techniques
SC: Hydrology [H]
MN: 2005 Joint Assembly