Aquatic Sciences Meeting, Albuquerque 2001

SS08 Processes at the Benthic Interface (Environmental Connections)

Date: Monday, February 12, 2001, Time: 4:45:00 PM

Location: Ruidoso/Pecos

Edgington, D, N, Great Lakes Water Institute, NIVERSITY OF WISCONSIN, MILWAUKEE WI, USA, dnedge@uwm.edu

Robbins, J, A, Great Lakes Resrearch Laboratory, NOAA, AnnArbor MI, USA, robbins@glerl.noaa.gov

Heyvaert, A, , Lake Tahoe Research Group, University of California, Davis CA, USA, aheyvaert@ucdavis.edu

Olaniyi, H, D, Dept. of Physics, Obafemi Awolowo University, Ile Ife, Nigeria,

IS PB-210 DATING EASY? BUILDING A SELF-CONSISTENT INTERPRETATION OF RADIONUCLIDE PROFILES IN LAKE TAHOE

Pb-210, Pu-239, Th-228, Ra-226, and K-40 were measured in a sediment core collected in 1998. The Pb-210 results may be compared with earlier profiles measured in 1982 and 1991. Cs-137 was measured in 1991 and 1998. Trace elements, e.g., Mn, Fe, and Pb, and organic carbon were also measured. The sediment record in Tahoe exhibits classical redox subsurface peaks of manganese, with iron below, from 2.5 to 4 cm., indicating little mixing by organisms. Excess Pb-210 profiles are not a simple exponential, but may reflect a higher sedimentation rate (x2) later than 1975 that is consistent with a decrease in organic carbon content concomitant with the disturbance of low organic carbon soils by construction activity. A comparison of Cs-137 and Pb-210 profiles may be explained by mixing to 5-6 cm. But penetration and sub-surface maximum of Pu-239 is consistent with Pb-210 sedimentation rates. Th-228 shows mixing down to 2-3 cm, consistent with the redox boundary. Development of a self-consistent model for these profiles needs to include differences in the geochemical interations of Cs-137 and Pu-239 with the sediments.

This Session Listing

Aquatic Sciences Meeting, Albuquerque 2001

Quicklinks