Rosemary Caroll,
Desert Research Institute, Reno, NV
abstract
Mameet
Waria, University of Nebraska - Lincoln, Lincoln, NE
abstract
Na
Wei, University of Illinois - Urbana Champaign, Urbana, IL
abstract
Rosemary
Carroll:
Evaluating
the Impacts of Uncertainty in Geomorphic Channel Changes
on Predicting Mercury Transport and Fate it the Carson
River System,
Nevada
John J. Warwick, Ph.D., Environmental Engineering,
Executive Director, Desert Research Institute, Division of
Hydrologic Sciences, 2215 Raggio Parkway, Reno, NV 89512,
Tel: 775-673-7379, Email: John.Warwick@dri.edu
Rosemary Carroll, M.S., Hydrology, Research Scientist,
Desert Research Institute, Division of Hydrologic
Sciences, 2215 Raggio Parkway, Reno, NV 89512
The
Carson River is one of the most mercury contaminated
fluvial systems in
North America
. Most of its mercury is affiliated with channel bank
material and floodplain deposits, with the movement of
mercury through this system being highly dependent on bank
erosion and sediment transport processes. Mercury
transport is simulated using three computer models: RIVMOD,
WASP5, and MERC4. Model improvements include the addition
of a bank package that accounts for flow history. The
rates at which river stages are rising or falling will, in
turn, impart time-dependant and vertically variable MeHg
concentrations within the channel banks along the Carson
River. Also, Lahontan Reservoir’s geomorphic
characteristics have been refined along with the explicit
tracking of a temporally and spatially varying colloidal
fraction. The augmented and refined modeling approach
results in more accurate and realistic simulation of
mercury transport and fate. An extensive uncertainty
analysis, involving characterizing the co-variance of two
calibration parameters used to define bank erosion and
overbank deposition, will define the degree of expected
variation in model predictions relative to limitations
posed by available field data.
Manweet
Waria:
Field-Scale
Cleanup of a Pesticide-Contaminated Soil with a
Combined Chemical-Biological Approach
Manmeet Waria, School of Natural Resources, 255 Keim
Hall, University of Nebraska-Lincoln, Nebraska-68583,
Tel: 402-560-8854, Fax: 402-472-7904, Email: mwaria1@bigred.unl.edu
Tunlawit Satapanajaru,
Kasetsart
University
,
Bangkok
,
Thailand
10900, Tel: 662-942-8036
Steve D Comfort, School of Natural Resources, 255 Keim
Hall, University of Nebraska-Lincoln, Nebraska-68583,
Tel: 402-472-1502, Fax: 402-472-7904
A
former agrichemical dealership in
North Platte
,
NE
was suspected of having contaminated soil from
multiple work-related spills. Dealership property was
grid sampled and found to contain high concentrations
of atrazine (>300 mg/kg) and cyanazine (>500
mg/kg). The top 60-cm of soil was removed, placed in
windrows, and thoroughly mixed with a mechanical
high-speed mixer. Mixing homogenized the contaminated
soil and lowered pesticide concentrations via
dilution. Laboratory investigations were then
initiated to determine optimum treatments for
pesticide destruction. Using zerovalent iron (Fe0) as
a chemical reductant along with ferrous sulfate (FeSO4·7H2O),
we observed greater than 70% destruction of both
pesticides within 14 d. We also evaluated emulsified
soybean oil (EOS® concentrate 598B42) as a carbon
source to stimulate biodegradation and found it was
also effective in degrading atrazine and cyanazine
(~75%). Combining soybean oil with the chemical
amendments resulted in higher destruction efficiencies
(80-85 %) and reduced the percentage of FeSO4 needed.
Field treatments were applied (2.5 % Fe0 + 1% FeSO4·7H20
and Oil) to ~360 yd3 of contaminated soil, water was
added (0.30 kg water kg-1 soil) and soil windrows were
covered with clear plastic to reduce loss of soil
moisture. Temporal sampling through 60 days showed
destruction of 75 to 80% for both atrazine and
cyanazine. These results provide evidence that both
chemical and biological approaches can be used for
on-site, field-scale treatment of
pesticide-contaminated soil. Investigation of
pesticide degradation products are ongoing and will
also be presented.
Na
Wei:
Anaerobic
MTBE and TBA Biodegradation under Different Terminal
Electron Accepting Processes
Na Wei, University of Illinois - Urbana Champaign,
Dept of Civil and Environmental Engineering, NCEL 205 N.
Mathews, Urbana, IL, 61801, Tel: 217-333-8121, Email: nawei2@uiuc.edu
Kevin T. Finneran, Assistant Professor,
University of Illinois - Urbana Champaign, Dept of Civil
and Environmental Engineering, NCEL 205 N. Mathews,
Urbana, IL, 61801, Tel: 217-333-1514, Fax: 217-333-6967,
Email: finneran@uiuc.edu
The
fuel oxygenate methyl tert-butyl ether (MTBE) is a
prevalent groundwater contaminant, and its key degradation
intermediate tert-butyl alcohol (TBA) often accumulates in
subsurface environments. Although studies have reported
potential for aerobic microbial degradation of MTBE and
TBA, in situ conditions within proximity of source areas
are typically anaerobic, and moreover, oxygen introduced
artificially can be consumed quickly by chemical oxidation
of Fe (II) and sulfides. Source area bioremediation
strategies must encompass anaerobic conditions from
nitrate reduction, Fe (III) reduction, sulfate reduction
to methanogenesis, as these processes shift from higher to
lower redox processes. This research has investigated the
mechanisms and kinetics of MTBE and TBA biodegradation
under shifting anaerobic conditions.
Microcosm
experiments were initiated using petroleum contaminated
sediment, river sediment, and anaerobic digester sludge.
Radiolabeled (14C) and non-radiolabeled MTBE and TBA were
amended to different incubations to quantify MTBE/TBA
biodegradation. Different electron acceptor amendments and
electron shuttling amendments were added to identify the
MTBE degradation (and potential TBA accumulation) dynamics
as conditions shift from one dominant process to another.
To date the microcosms are in acclimation stage with up to
5% recovery of [U
-14C
]-MTBE or [U
-14C
]-TBA as 14CO2. Data
suggest that fumarate and electron shuttles increase the
extent of MTBE biodegradation; however, TBA degradation is
slower than corresponding MTBE incubations.
Sulfate increases the rate of MTBE and TBA
biodegradation, but is very dependent on the starting
material. Liquid enrichments with petroleum contaminated
sediment degraded MTBE and TBA in less than one month
under nitrate reducing, Fe (III) reducing, sulfate
reducing and fumerate reducing conditions. These liquid
enrichments may provide a model, anaerobic microbial
culture for investigating basic cellular processes related
to anaerobic MTBE and TBA biodegradation – currently, no
such anaerobic culture has been reported.
These data suggest that anaerobic MTBE/TBA
biodegradation is influenced by shifting electron
accepting processes, and the effects of these geochemical
factors on MTBE/TBA degradation continue to be
investigated.
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