HR: 11:50h
AN: B32B-07    [Abstracts]
TI: Controls on Microbial Transport in Subsurface Sediments
AU: * Szecsody, J E
EM: jim.szecsody@pnl.gov
AF: Pacific Northwest National Laboratory, PO Box 999, Richland, WA 99354 United States
AB: Laboratory-scale measurements of microbial transport indicate that most microbes attach to subsurface sediments. Given this attachment, it is unclear how microbes are transported significant distances in deep aquifers. It was hypothesized that attachment/detachment mechanisms are dynamic responses to nutrient availability, so that transport is dependent upon the presence/absence of electron donors and acceptors. For one microbial isolate of the Shewanella strain CN-32 there was high attachment in the presence of both electron donor and acceptor, and very little attachment if no donor or acceptor were present. In addition, CN-32 exhibited chemotatic movement through electron donor/acceptor gradients. A series of batch, 1-D homogeneous, 1-D heterogeneous, and 2-D heterogeneous experiments were conducted to quantify CN-32 Monod parameters and to assess the relative importance of simple attachment/detachment steps, dynamic growth/detachment steps, and chemotaxis. Three models included dual Monod kinetics for a single electron donor (lactate), two electron acceptors (dissolved oxygen and nitrate), and either: a) constant microbial attachment (adsorption), b) attachment linked to the presence of electron donor/acceptor, or c) chemotaxis. Simulations of batch experiments using quantified Monod parameters could not predict 1-D experimental results without accounting for microbial attachment. With constant input of electron donor/acceptors, microbial attachment could be well approximated assuming constant microbial adsorption. However, advection of input pulses of electron donor/acceptors resulted in much further downgradient migration, which could be simulated assuming an empirical growth/detachment reaction. The 2-D experimental system with microbes that received input pulses of electron donor/acceptors (idealized representation of an aquifer) showed that that both chemotaxis and the dynamic growth/detachment mechanisms were needed to approximate microbial movement over time in the system. The results indicate that microbial transport is a complicated process with several chemical components.
DE: 1030 Geochemical cycles (0330)
DE: 1065 Major and trace element geochemistry
DE: 1094 Instruments and techniques
DE: 3947 Surfaces and interfaces
SC: Biogeosciences [B]
MN: Fall Meeting 2005