HR: 1340h
AN: B33C-1049    [Abstracts]
TI: Simultaneous field estimates of urea hydrolysis rates and ammonium retardation factors in a fractured rock aquifer
AU: * Smith, R W
EM: smithbob@uidaho.edu
AF: University of Idaho, 1776 Science Center Drive, Idaho Falls, ID 83402 United States
AU: Taylor, J L
EM: tayljl@if.uidaho.edu
AF: University of Idaho, 1776 Science Center Drive, Idaho Falls, ID 83402 United States
AU: Fujita, Y
EM: Yoshiko.Fujita@inl.gov
AF: Idaho National Laboratory, PO Box 1625, Idaho Falls, ID 83415 United States
AB: Knowledge of the rates of in situ biogeochemical processes is critical to the design and implementation of active and passive environmental remediation strategies. However, often rate determinations require the collection of samples in the field followed by laboratory studies that may occur days or weeks later. Artificial laboratory conditions as well as sample storage effects can lead to erroneous conclusions regarding kinetic processes in nature. We have been investigating in field and laboratory studies the microbial hydrolysis of urea as a method to facilitate calcium carbonate precipitation and co-precipitation of divalent metal and radionuclide contaminants (such as ⁹⁰Sr). In conjunction with a single well "push-pull" test conducted in a fractured basalt aquifer near the Idaho National Laboratory, in situ rates of urea hydrolysis were estimated by tracking the disappearance of urea and a conservative tracer and measuring the increase in ammonium concentration. The analysis of rates was complicated by cation exchange reactions of ammonium with the aquifer matrix. However, we were able to derive and parameterize a rate law that explicitly included a retardation factor. With this approach, we are able to characterize in situ ureolysis kinetics without resorting to laboratory studies.
DE: 0412 Biogeochemical kinetics and reaction modeling (0414, 0793, 1615, 4805, 4912)
DE: 0496 Water quality
SC: Biogeosciences [B]
MN: Fall Meeting 2005