HR: 0800h
AN: H51D-1189    [Abstracts]
TI: Correlation Between in-situ Redox Reaction Rates and Microbial Biomass Distribution in Porous Media Influenced by Different Transport Regimes
AU: * Thullner, M
EM: m.thullner@geo.uu.nl
AF: Department of Earth Sciences - Geochemistry, Utrecht University, P.O. Box 80021, Utrecht, 3508 TA Netherlands
AU: Pallud, C
EM: c.pallud@geo.uu.nl
AF: Department of Earth Sciences - Geochemistry, Utrecht University, P.O. Box 80021, Utrecht, 3508 TA Netherlands
AU: Van Cappellen, P
EM: pvc@geo.uu.nl
AF: Department of Earth Sciences - Geochemistry, Utrecht University, P.O. Box 80021, Utrecht, 3508 TA Netherlands
AU: Regnier, P
EM: p.regnier@geo.uu.nl
AF: Department of Earth Sciences - Geochemistry, Utrecht University, P.O. Box 80021, Utrecht, 3508 TA Netherlands
AB: Microbially mediated redox transformations of organic carbon play an important role for the fate of reactive species in porous media. The terminal electron acceptors (TEAs) involved in such reactions depend on the amount and degradability of the organic carbon species and lead to a succession of redox reactions where the TEAs are used-up in a temporal or, in case transport is considered, spatial sequence of decreasing energy yields. A direct characterization of redox stratified systems is challenged by our ability to measure reaction rates in-situ. One novel approach consists in quantifying and characterizing microorganisms in aquifers and sediments and to use such results to predict in-situ redox reaction rates. However, the existence of a spatial correlation between microbial abundance and associated in-situ redox reaction rates should be questioned. Here, we investigate this correlation for porous media having different transport regimes. In the environment, these regimes vary between systems such as aquifers, where advective transport in the water phase is the dominant transport mechanism, and aquatic sediments, where close to the sediment water interface the mixing activity of benthic macrofauna contributes significantly to transport. Results from estuarine sediments show that for such systems, the spatial distributions of redox reaction rates and the associated microorganisms are not correlated. This observation is supported by reactive transport simulations, which show that the ratio of the time scale of the mixing processes to the time scale of microbial growth is controlling the spatial correlation between redox reaction rates and the distribution of microorganisms. For sediments highly affected by mixing, the correlation is missing or weak, while in advection controlled systems such as aquifers, a good correlation between redox rates and microbial biomass distribution can be expected.
DE: 3210 Modeling
DE: 1832 Groundwater transport
DE: 1030 Geochemical cycles (0330)
DE: 0400 Biogeosciences
SC: Hydrology [H]
MN: 2004 AGU Fall Meeting