Aquatic Sciences Meeting, Albuquerque 2001
| PC07 Spatial and Temporal Connections |
| Date: Wednesday, February 14, 2001 |
| Location: Southwest Hall |
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| Robbins, J, A, Great Lakes Environmental Research Laboratory, NOAA, Ann Arbor, USA, robbins@glerl.noaa.gov |
| Edgington, D, N, Great Lakes WATER Institute, University of Wisconsin, Milwaukee, USA, dnedge@uwm.edu |
| Eadie, B, J, Great Lakes Environmental Research Laboratory,NOAA, Ann Arbor, USA, eadie@glerl.noaa.gov |
| Morehead, N, R, Great Lakes Environmental Research Laboratory, NOAA, Ann Arbor, USA, morehead@glerl.noaa.gov |
| Rood, R, W, Cooperative Institute for Limnology and EWcosystems Research, University of Michigan, Ann Arbor, USA, |
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| INCORPORATING LOCAL AND NON-LOCAL TIME-AVERAGING EFFECTS INTO DIAGENETIC MODELS OF CS-137 PROFILES USED TO CREATE TIME-EVOLVING INVENTORY MAPS FOR LAKE MICHIGAN |
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| Distributions of Pb-210 in 134 box cores collected between 1992 and 1996 from recent sediments in Lake Michigan have been interpreted using a conventional model based on a constant rate of supply of Pb-210 plus steady-state diffusive near-surface mixing and rate of accumulation of sediments. The ratio of the latter two quantities yields a site-specific residence time of particles in the sediment surface mixed layer that characterizes time-averaging by local (in situ) mixing processes. Corresponding Cs-137 profiles show that the atmospheric flux of this fallout radionuclide was first-order time averaged by processes occurring on lake-wide (non-local) spatial scales prior to incorporation into sediments. Thus, because Cs-137 loading to the lake is time-dependent, profiles are the result of both non-local and local time-averaging processes. Inclusion of both in modeling profiles, allows the effects of mixing to be removed, thus revealing local deposition histories that can be used to illustrate how the pattern of Cs-137 accumulation in sediments has evolved throughout the lake during the past 50 years. The result is quite consistent with recent observations of cross-margin particle transport. |
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