HR: 08:00h
AN: H41H-01    [Abstracts]
TI: The Role of EPS in Microhydrology and Transport Processes Affecting Microbial Activity in Unsaturated Porous Media
AU: * Or, D
EM: dani.or@epfl.ch
AF: School of Architecture, Civil, and Environmental Engineering, Ecole Polytechnique Federale de Lausanne (EPFL), Bƒtiment GR-2, Lausanne, CH-1015 Switzerland
AU: * Or, D
EM: dani.or@epfl.ch
AF: University of Connecticut, Department of Civil and Environmental Engineering University of Connecticut 261 Glenbrook Road, Unit 2037 , Storrs, CT 06269-2037
AU: Phutane, S
EM: spr04007@engr.uconn.edu
AF: University of Connecticut, Department of Civil and Environmental Engineering University of Connecticut 261 Glenbrook Road, Unit 2037 , Storrs, CT 06269-2037
AB: Extra-cellular Polymeric Substances (EPS) refers to biopolymers excreted and surrounding soil bacterial cells (and other biota) forming the scaffolding for colonies and serving a wide array of transport, nutrient entrapment, and mechanical functions. In essence, EPS is a porous matrix through which aqueous, gaseous and nutrient fluxes flow to supply the embedded bacterial cells. The large water holding capacity and retarded water loss rates of EPS dampens rapid fluctuations in hydration status of host porous medium which sustain higher diffusion fluxes than in surrounding porous medium, and shelters microbial cells from effect of rapid desiccation or rewetting. The morphology of EPS changes from an open well-hydrated bioweb to dense and highly cross-linked structure under dry conditions. Such morphological changes are accompanied by enhanced mechanical strength and retardation of water loss that provide additional time for physiological adaptation to desiccation. Additional capacitance results from the disparity in dynamic hydrological properties between EPS and soil that promotes water entrapment in EPS during rapid drainage. EPS may also trap dissolved nutrients that may be unevenly distributed and irregularly supplied in unsaturated environments, thereby increasing nutrient availability in the microhabitat and offsetting decreased supply by diffusion during drying. The remarkable transport and mechanical properties of EPS makes it an important stabilizing agent for soil aggregation and even minute amounts of EPS may significantly alter macroscopic hydrological properties of host porous medium.
DE: 0463 Microbe/mineral interactions
DE: 1813 Eco-hydrology
DE: 1866 Soil moisture
SC: Hydrology [H]
MN: Fall Meeting 2005