HR: 0800h
AN: H21E-1060    [Abstracts]
TI: Characterization of Geochemical Factors Controlling PCE Sorption to Carbonaceous Matter by Lithofacies
AU: * Taylor, K M
EM: kmtaylor@mail.wsu.edu
AF: Washington State University, 1228 Webster Hall, Pullman, WA 99164-2812 United States
AU: Allen-King, R M
EM: richelle@geology.buffalo.edu
AF: SUNY at Buffalo, 876 Natural Sciences Complex, Buffalo, NY 14260 United States
AU: Gaylord, D R
EM: gaylordd@wsu.edu
AF: Washington State University, 1228 Webster Hall, Pullman, WA 99164-2812 United States
AB: Understanding the heterogeneous distribution of aquifer geochemical properties that affect contaminant transport, such as sorption, is essential to accurate contaminant transport prediction and maximizing remediation efficiency. Previous work by our group identified a correlation between the sorption coefficient (Kd) measured for a probe contaminant, perchloroethylene or PCE, and lithofacies, mapped based on sediment characteristics, for aquifer material from Canadian Forces Base Borden. The Kd distributions for the 11 mapped lithofacies were determined from a total of approximately 350 samples. The distribution of variance was the primary difference between the Kd distributions by lithofacies. We hypothesize that carbonaceous matter (CM) associated with granule-size and larger carbonate lithic fragments concentrated within particular lithofacies is primarily responsible for greater and more nonlinear sorption observed in certain lithofacies. Our idea is tested by obtaining the fraction organic carbon (foc), carbonate contents, and the PCE Kd at two concentrations ($\sim$ 7 ug/L and $\sim$ 1600 ug/L) for high-sorbing and low-sorbing subsamples of four of the lithofacies, and 2 to 4 mm carbonate granule material ($\sim$ 70% CaCO3-C) sieved from bulk Borden aquifer material. With this data, we test the influence that this carbonate-associated CM has on sorption. The Kd and Koc (= Kd/foc) values are greatest for the carbonate granule material, followed by the two lithofacies that contain greater organic carbon and carbonate contents, and are characterized by a larger mean grain size and poorer sorting than the other lithofacies. For all lithofacies measured, the low concentration Kd is greater than the high concentration Kd, demonstrating that all samples exhibit nonlinear sorption. Thin section analysis was used to qualitatively determine the proportion of sparry versus micritic carbonate granules within the sediment. Our results suggest that in addition to CM external to carbonate lithic fragments, the CM associated with the carbonate material affects sorption nonlinearity, contributing significantly to total sorption.
DE: 1829 Groundwater hydrology
DE: 1832 Groundwater transport
SC: Hydrology [H]
MN: 2004 AGU Fall Meeting