HR: 15:00h
AN: B23C-06    [Abstracts]
TI: Structure, Transport, Transformation: A framework for analysis of denitrification and other microbially mediated processes in aquatic systems
AU: * Packman, A I
EM: a-packman@northwestern.edu
AF: Northwestern University, Dept. of Civil and Environmental Engineering 2145 Sheridan Rd., Evanston, IL 60201 United States
AU: Arnon, S
EM: s-arnon@northwestern.edu
AF: Northwestern University, Dept. of Civil and Environmental Engineering 2145 Sheridan Rd., Evanston, IL 60201 United States
AU: Gray, K A
EM: k-gray@northwestern.edu
AF: Northwestern University, Dept. of Civil and Environmental Engineering 2145 Sheridan Rd., Evanston, IL 60201 United States
AB: Surface water systems are inherently heterogeneous and dynamic. Denitrification is one of many transformation processes that is strongly influenced by physical-chemical-biological coupling and system structure, and will be considered here as an important example of a general class of biogeochemical processes involving transport across redox gradients. Ongoing concern about the deleterious effects of nitrate export to coastal waters emphasizes the need for improved estimates of long-term average rates of denitrification within watersheds. The physical-chemical-biological structure of aquatic and sedimentary systems controls the distribution of regions with appropriate conditions for denitrification, as well as potential local denitrification rates. Hydrodynamic transport processes deliver nitrate from the water column to regions where denitrification can occur within hyporheic, periphytic, or epiphytic biofilms. Net nitrogen transformation thus depends on the interplay of hydrodynamic transport, microbial processes, and the distribution of local chemical conditions within the water column, pore water, and sediments. While the physical-chemical structure of the system, such as pore water transport patterns and redox gradients, place an important control on instantaneous biological transformation rates, this structure is coupled with biological processes over longer time scales. Here we provide an overview of the important aspects of system structure and physical transport that mediate microbial processes within sediments. New experimental results will be presented that illustrate both the link between sediment structure and transport in pore waters, and the coupling of physical transport processes with the redox environment and nitrate removal. A theoretical framework will also be presented for explicit averaging of biogeochemical transformation rates from the local scale to the watershed scale with consideration of the dynamic nature of surface water systems.
DE: 0404 Anoxic and hypoxic environments (4802, 4834)
DE: 0408 Benthic processes (4804)
DE: 0414 Biogeochemical cycles, processes, and modeling (0412, 0793, 1615, 4805, 4912)
DE: 0469 Nitrogen cycling
SC: Biogeosciences [B]
MN: Fall Meeting 2005