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DISSOLVED ORGANIC MATTER AND DISSOLVED ORGANIC MATTER AND NITROGEN REDOX CHEMISTRY IN AQUATIC NITROGEN REDOX CHEMISTRY IN AQUATIC
ALPINE ECOSYSTEMSALPINE ECOSYSTEMS
Matt Miller Matt Miller
Ph.D. StudentPh.D. StudentAdvisor: Diane McKnightAdvisor: Diane McKnight
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Biogeochemical Hot Spots and Hot MomentsBiogeochemical Hot Spots and Hot Moments
Hot Spot:Hot Spot: An area exhibiting high An area exhibiting high rates of biogeochemical transformation rates of biogeochemical transformation in comparison to the surrounding in comparison to the surrounding environmentenvironment
Hot Moment:Hot Moment: Short periods Short periods of time during which reactions of time during which reactions rates are higher than those rates are higher than those during the rest of the seasonduring the rest of the season
0
10000
20000
30000
40000
50000
60000
70000
5/23 6/12 7/2 7/22 8/11 8/31 9/20 10/10 10/30
Date
Dis
char
ge (m
3 /day
)
Potential Hot Moment
McClain et al. (2003)
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O
Me
MeO
MeO
Me
H
O
n
O
Me
MeO
MeO
Me
H
O
n
O
Me
MeO
MeO
Me
H
O
n
O
l ignin
MeO
O
l ignin
OH
OMeOH O
l ignin
MeO
O
l ignin
OH
OMeOH
HO
OO
Me
Slide by: Rose Cory
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Fe3+
Fe2+
NO3-
NO2- + DOM
DOM-N
Humics act as electron shuttle
Ferrous Wheel Hypothesis
CO2
Acetate
Oxidized DOM
DOM reducing microorganism
Reduced DOM
e-
DOM: Electron TransferDOM: Electron Transfer
Slide by: Chris Jaros
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Green Lakes ValleyGreen Lakes Valley
ALBION TOWNSITE
LAKE ALBION
GL4
GL5
NAVAJO STREAM
NIWOT RIDGE
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Question 1:Question 1: Is the stream in the upper reaches of the Is the stream in the upper reaches of the catchment acting as a hotspot for C as well as N?catchment acting as a hotspot for C as well as N?
Question 2:Question 2: Do lakes in headwater ecosystems act as Do lakes in headwater ecosystems act as hotspots? If so, is the importance of lake processing a hotspots? If so, is the importance of lake processing a
function of seasonal changes in hydrology and/or biology?function of seasonal changes in hydrology and/or biology?
Research QuestionsResearch Questions
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*Tracer Injection w/ LiBr*Tracer Injection w/ LiBr
*Modeled with OTIS*Modeled with OTIS
*Sampled for:*Sampled for:-DOC-DOC
-N species-N species-Li and Br-Li and Br
Stream as Biogeochemical Hot SpotStream as Biogeochemical Hot Spot
Miller et al. (2006)
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Main Channel:
Storage Zone:
Advection
Dispersion
Lateral inflow
Transient storage
Transient storage
Decay
Decay
Modeling Hyporheic Exchange: OTISModeling Hyporheic Exchange: OTIS
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Solute Transport Modeling ResultsSolute Transport Modeling Results
Miller et al. (2006)
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Stream Decay (λ) Storage Zone Decay (λs)
NO3- -1.0 x 10-3 1.0 x 10-4
NH4+ 1.2 x 10-3 -7.9 x 10-5
DOC 1.6 x 10-2 -1.3 x 10-4
Redox Index 6.5 x 10-3 -8.4 x 10-5
λC
λsC
Reactive Transport ResultsReactive Transport Results
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Hydrologic Controls on DOMHydrologic Controls on DOM
Hood et al. (2003)
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Alpine: Green Lake 4 (GL4)Alpine: Green Lake 4 (GL4)
Subalpine: Lake Albion (ALB)Subalpine: Lake Albion (ALB)
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GL4 (Alpine) ALB (Subalpine)
Response to Hydrologic
Change
Response to Biological
Change
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Humic Redox Results
0.27
0.32
0.37
0.42
0.47
0.52
3-May 22-Jun 11-Aug 30-Sep
RI
Wetland = 0.51
Stream = 0.39 Rain Event Peak
Chl a
0.27
0.32
0.37
0.42
0.47
0.52
3-May 22-Jun 11-Aug 30-Sep
RI
Rain Event
Peak Chl a
Wetland = 0.51
Stream = 0.39
GL4 (Alpine) ALB (Subalpine)
Response to Biological
Change
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Lake ModelingLake Modeling
There is clearly a large signal due to both hydrologic and There is clearly a large signal due to both hydrologic and biologic changes in the system.biologic changes in the system.
Modeling Approach: Mass Balance for a Lake with a Well Modeling Approach: Mass Balance for a Lake with a Well Mixed Epilimnion (both GL4 and ALB)Mixed Epilimnion (both GL4 and ALB)
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Proposed Mass Balance CalculationsProposed Mass Balance Calculations
Conservative Transport:Conservative Transport:
Reactive Transport (1Reactive Transport (1stst order rxn. at steady-state): order rxn. at steady-state):
Variables to be modeled: DOC, NOVariables to be modeled: DOC, NO33--, NH, NH44
++, FI, PARAFAC, FI, PARAFAC
11stst Order Rxn.? Order Rxn.?k(?): DOC, chlorophyll a, temperature, pH, etc?k(?): DOC, chlorophyll a, temperature, pH, etc?