land-use controls on the export and retention of
TRANSCRIPT
Land-use controls on
the export and
processing of
atmospheric NO3
Joel Bostic, Keith Eshleman, David Nelson
University of Maryland Center for Environmental Science, Appalachian Lab
CBP Forestry Workgroup 2/6/19
Background
Chesapeake Bay Program
Kemp et al. 2005VIMS
Background
Eshleman et al. 2013
Tom Hamilton
Unprocessed Atmospheric NO3
Processing vs. Retention
16O17O18O
99.76% 0.04% 0.20%
NO3
N
N
Atm. NO3
Terr. NO3N
N
Not processed, Not retained
N
N
Atm. NO3
Terr. NO3N
N
NProcessed, Not retained
Research Objectives
• Quantify the proportion of
atmospheric NO3 in streams
• Investigate the effect of land use on
processing efficiency of atmospheric
NO3
Study Watersheds
Watershed Land Use
BIGR
TERR
DPRN
TOW
BLAC
GEO
WIL
CAC
MON
GUN
GWN
ANT2
ANT
CON
Stream Sampling
Gunpowder Falls (GUN) Gwynns Falls (GWN)
Ant. Creek Upstream (ANT) Ant. Creek Down. (ANT2) Monocacy River (MON) Catoctin Creek (CAC)
Town Creek (TOW) Terrapin Run (TERR) Deep Run (DPRN) Conococheague C. (CON)
Big Run (BIGR) Black Lick (BLAC) Georges Creek (GEO) Wills Creek (WIL)
2016 2017 2016 2017
2016 2017 2016 2017
0255075
100125
0
50
100
150
0
10
20
05
10152025
0
1
2
3
0
50
100
0.0
0.5
1.0
0.0
0.5
1.0
1.5
1020304050
05
10152025
0.0
0.1
0.2
0.3
0
20
40
0
5
10
15
10
20
30
Date
Me
an
Da
ily D
isch
arg
e (
m3 s
-1)
Grab Samples
RESULTS
Total NO3 Concentrations
Total NO3 Loads
0
3
6
9
12
BIGR BLAC GEO WIL TOW TERR DPRN CON ANT ANT2 MON CAC GUN GWN
Watershed
To
tal N
O−
3 N
Lo
ad
(kg
ha
-1 y
r-1 )
Atmospheric NO3 in Stream
Samples (%)
Atmospheric NO3
Concentrations
Seasonal Atm. NO3
Atmospheric NO3 Loads
0.00
0.05
0.10
0.15
0.20
0.25
BIGR BLAC GEO WIL TOW TERR DPRN CON ANT ANT2 MON CAC GUN GWN
Watershed
Atm
osp
he
ric N
O3−
N L
oa
ds (
kg
ha
-1 y
r-1)
Atmospheric NO3 Loads and
Land Use
p < 0.001, r2 = 0.63
0.00
0.05
0.10
0.15
0.20
0.25
20 40 60 80 100
Forest Land Use (%)
Atm
osp
heri
c N
O−
3 N
Loa
d (
kg h
a-1 y
r-1 )
p < 0.05, r2 = 0.350.05
0.10
0.15
0.20
0.25
0 20 40 60
Agriculture Land Use (%)
Atm
osp
heri
c N
O−
3 N
Loa
d (
kg h
a-1 y
r-1 )
Processing Efficiency and
Land-Use
Conclusions
• Small (0-20%, mean = 3-4 %) percentage of NO3 was unprocessed atmospheric NO3 across forested and agricultural watersheds – but highest percentage in most developed watershed
• Forests: most “efficient” at processing deposited NO3
• Agricultural/Developed watersheds: less “efficient” at processing deposited NO3 – 2 potential controls:– 1: Hydrologic: Altered flowpaths in developed land-use
watersheds reduce processing by rapidly routing water to streams
– 2: N Saturation: Additional N inputs in agricultural land-use watersheds reduce processing by overwhelming ecosystem N capacity
N
N
Atm. NO3
Terr. NO3
NN
N
N
N
N
NN N N
NNN
N
N
Atm. NO3
Terr. NO3
NN
N
N
N
N
NN N N
NNN
N
N
Atm. NO3
Terr. NO3
N N
NN N
NNN
N
NN
N N
N
N
N
N
N
NN
N
N
NNN
NN N
N
N
Atm. NO3
Terr. NO3
N N
NN N
NNN
N
NN
N N
N
N
N
N
N
NN
N
N
NNN
NN N
N
N
Atm. NO3
Terr. NO3
N
N
N
N N
N
NN
N
N
N
NN
N
N
Atm. NO3
Terr. NO3
N
N
N
N N
N
NN
N
NN
N
N
Next Steps
1984 CB Land Cover
(USGS)
Next Steps
GWN
GUN
CAC
MON
ANT2
ANT
CON
DPRN
TERR
TOW
WIL
GEO
BLAC
BIGR
1984 1992 2001 2006 2011
Year
Wa
ters
he
d
0.10.20.30.4
NO3−NAtm.(kg N ha-1
yr-1
)
Next Steps
GWN
GUN
CAC
MON
ANT2
ANT
CON
DPRN
TERR
TOW
WIL
GEO
BLAC
BIGR
1984 1992 2001 2006 2011
Year
Wa
ters
he
d
01234
Historical
Current NO3−NAtm.
Next Steps
Acknowledgments-Field Sampling: Maryland DNR
-Lab Assistance: Robin Paulman, Jim
Garlitz, Katie Kline, Andrew Schauer
-Funding: Maryland Sea Grant, National
Science Foundation
Isotopes and Atmospheric
NO3
d17O (‰)
d18O (‰)
Isotopes and Atmospheric
NO3d17O (‰)
d18O (‰)
Terrestrial/Biologic
al NO3
Isotopes and Atmospheric
NO3d17O (‰)
d18O (‰)
Atmospheric NO3
Terrestrial/Biologic
al NO3
Isotopes and Atmospheric
NO3d17O (‰)
d18O (‰)
Atmospheric NO3
Terrestrial/Biologic
al NO3
D17O = d17O – 0.52 x d18O
Fraction of total NO3 that is
atmospheric NO3
Isotopes and Atmospheric
NO3Atmospheric
Deposition NO3
D17O ≅ 25 ‰
Terrestrial/Biological
NO3
D17O = 0 ‰
NO3-Atm.
=D17O- NO
3-Sample
D17O- NO3-Deposition
´NO3
Fraction Atm. NO3=
D17O-NO3-Sample
D17O-NO3-Deposition
• Concentration of atmospheric
NO3 in stream sample:
