spatial and temporal variations in nutrient concentration and speciation in silver bow creek
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Spatial and temporal variations in nutrient concentration and speciation in Silver Bow Creek. Chris Gammons, John Babcock, Bev Plumb, Steve Parker Montana Tech, Butte, MT. Monitoring databases for nutrients in surface waters often look like this. Why so messy?. Outline of talk. - PowerPoint PPT PresentationTRANSCRIPT
Chris Gammons, John Babcock, Bev Plumb, Steve Parker Montana Tech, Butte, MT
Spatial and temporal variations in nutrient concentration and speciation in Silver Bow Creek
Monitoring databases for nutrients in surface waters often look like this
Why so messy?
Outline of talk
Site description Synoptic variations Seasonal variations Diel variations Lateral (bank to bank) variations Implications for monitoring
SBC-6
Warm Springs Ponds
Pit Lake
City of
Butte
5 km
46 N116 W
46 N106 W
Butte
Missoula
Clark Fork River
detail
north
Ger
man
SBC-3SBC-1
Lower SBC
0 1 2 km
12323250
Ÿ
I-15/90
Ÿ
12323240
SBC-3SBC-1
zone of hypoxia
SBC-2
WWTPLAO
MPTPUSGS gaging stationroad
SBC-1Above WWTP
SBC-6
Warm Springs Ponds
Pit Lake
City of
Butte
5 km
46 N116 W
46 N106 W
Butte
Missoula
Clark Fork River
detail
north
Ger
man
SBC-3SBC-1
Lower SBC
0 1 2 km
12323250
Ÿ
I-15/90
Ÿ
12323240
SBC-3SBC-1
zone of hypoxia
SBC-2
WWTPLAO
MPTPUSGS gaging stationroad
WWTP discharge
SBC-6
Warm Springs Ponds
Pit Lake
City of
Butte
5 km
46 N116 W
46 N106 W
Butte
Missoula
Clark Fork River
detail
north
Ger
man
SBC-3SBC-1
Lower SBC
0 1 2 km
12323250
Ÿ
I-15/90
Ÿ
12323240
SBC-3SBC-1
zone of hypoxia
SBC-2
WWTPLAO
MPTPUSGS gaging stationroad
SBC-33 km below WWTP
SBC-6
Warm Springs Ponds
Pit Lake
City of
Butte
5 km
46 N116 W
46 N106 W
Butte
Missoula
Clark Fork River
detail
north
Ger
man
SBC-3SBC-1
Lower SBC
0 1 2 km
12323250
Ÿ
I-15/90
Ÿ
12323240
SBC-3SBC-1
zone of hypoxia
SBC-2
WWTPLAO
MPTPUSGS gaging stationroad
Warm Springs Ponds
0.01
0.1
1
10
0 1 2 3 4 5 6
km below mixing zone
pp
m a
s N
nitrate
ammonia
nitrite
Synoptic changes in nutrient concentrationSBC-3 below WWTP, August, 2006
Nitrite (NO2-) forms
as intermediate during oxidation of
NH4+ to NO3
-
Nitrosomonas
NitrificationAmmonium oxidation
Step 1: NH4+ + 1.5O2 → NO2
- + 2H+ + H2Oammonium nitrite
Step 2: NO2- + ½ O2 → NO3
-
nitrite nitrate
High nitrite usually means ammonium is being oxidized
0.01
0.1
1
10
0 2 4 6 8
C. July 22, 20080.01
0.1
1
10
0 2 4 6 8
B. June 28, 20070.01
0.1
1
10
0 2 4 6 8
conc
entra
tion,
mg/
L as N
A. Aug. 08, 2006
Distance below WWTP, km
NO3-
NO3-
NO3-
NO2-
NO2-
NO2-
NH4+
NH4+
NH4+
DINDINDIN
Decrease in NH4+ due to nitrification
Increase in NO3- due to nitrification
Decrease in DIN due to assimilation
Synoptic changes (different years)
mg
/L a
s N
0.0
0.5
1.0
1.5
mg
/L a
s N
0
1
2
3
4
5
A. NO3- + NO2
-
B. NH4+ + NH3
mg
/L a
s N
0
1
2
3
4
5
Outlet to WSPOU
C. DIN
01/98 01/99 01/00 01/01 01/02 01/03 01/04 01/05
mg
/L a
s P
0.0
0.2
0.4
0.6
0.8
Inlet to WSPOU
D. total dissolved PO43-
Nitrate + Nitrite
Ammonium
DINDissolved Inorganic N
Seasonal changes in nutrient concentrations SBC at Warm Springs Ponds
■ WSPOU INLET ○ WSPOU OUTLET
mg
/L a
s N
0.0
0.5
1.0
1.5
mg
/L a
s N
0
1
2
3
4
5
A. NO3- + NO2
-
B. NH4+ + NH3
mg
/L a
s N
0
1
2
3
4
5
Outlet to WSPOU
C. DIN
01/98 01/99 01/00 01/01 01/02 01/03 01/04 01/05
mg
/L a
s P
0.0
0.2
0.4
0.6
0.8
Inlet to WSPOU
D. total dissolved PO43-
Winter months
Diel changes SBC-3 below the Butte WWTP
12:00 16:00 20:00 00:00 04:00 08:00 12:00
mg
/L N
O3
-N o
r N
H4
-N
0.0
0.5
1.0
1.5
2.0
2.5
3.0
mg
/L N
O2
-N o
r P
O4
-P
0.0
0.2
0.4
0.6
0.8
Nitrate-NNitrite-NAmmonium-NPhosphate-P
7/23/2008 7/24/2008
Nutrient isotopes: synoptic
-10
-5
0
5
10
15
20
25
30
35
-1 0 1 2 3 4 5 6 7 8
δ15N
or
δ18O
distance below WWTP, km
δ15N-NH4
δ15N-NO3
δ18O-NO3
WWTP
SBC upstream
Nutrient isotopes: diel
0
5
10
15
20
25
30
12:00 18:00 0:00 6:00 12:00 18:00
δ15N
NO3-
7/24/087/23/08
NH4+
Δ = 14.1 ‰
Δ = 20 ‰
NH4-oxidizing bacteria preferentially metabolize 14N Isotopic separation is less during day (faster rates) Isotopic trends inconsistent with denitrification
1000 ft Silver Bow Creek
Silver Bow Creek WWTP discharge
USGS gaging station
How far below the confluence of SBC and WWTP before combined flow is mixed, bank-to-bank?
Lateral variations in water chemistry
300
350
400
450
500
550
600
0 2 4 6 8 10 12 14 16 18 20 22 24
SC, m
S/cm
Feet from north bank
100
340
1840
2440
Feet below confluence
Bank-to-bank profiles in specific conductance (SC)
200
300
400
500
600
700
800
0 1000 2000 3000
SC, m
S/cm
Feet below confluence of SBC and WWTP
North bank
South bank
Mixed
1000 ft
2400 feet
Silver Bow Creek
Silver Bow Creek
WWTP discharge
USGS gaging station
How far below the confluence of SBC and WWTP before combined flow is mixed, bank-to-bank?
Implications for nitrate monitoring The sample you collect is representative only of
a given spot in a given stream reach on a given day and at a certain time of day For streams like Silver Bow Creek, consider taking 24-h
integrated samples, or sample at same time of day for long-term trend analysis
For highly polluted waters, be sure to sample for all nutrients (e.g., ammonium, nitrite)
Stable isotope signatures of nitrate are also affected by synoptic and diel variations
Be careful that you are not sampling water from a stream or river that is not completely mixed
USGS 104b Montana Water Center Students
Bev Plumb John Babcock Stacey Wilcox Erika Sholey Brian Kuhn
Acknowledgements
References Plumb, B. (2009) Geochemistry of nutrients in Silver Bow
Creek, MT. M.S. Thesis, MT Tech. Gammons, C.H., Babcock, J., Parker, S.R., Poulson,
S.R. (2011) Diel cycling and stable isotopes of dissolved oxygen, dissolved inorganic carbon, and nitrogenous species in a stream receiving treated municipal sewage. Chemical Geology, 283, 44-55.
Questions??