Chesapeake Bay Atmospheric Deposition
Estimates
Modeling Subcommittee Quarterly ReviewApril 3, 2007
Lewis Linker and Gary ShenkCBP Modeling Team
Nitrogen Load Indicator
Watershed model indicator of source sector for nitrogen loads to the Bay
Atmospheric Deposition to the Chesapeake Bay Watershed
395.8 388.4
312.2
0
50
100
150
200
250
300
350
400
450
1985/ 1990 (Phase 4regression)
2005 (P5 originalcalibration regression
projected to 2005)
2005 (P5 PSU 84-05deposition regression)
(million lbs.
TN
/year)
Response in Loads to the Chesapeake Bay from Changes in Atmospheric Deposition
189.9 188.9179.2
0
50
100
150
200
250
300
350
400
450
1985/ 1990 (Phase 4regression)
2005 (P5 originalcalibration regression
projected to 2005)
2005 (P5 PSU 84-05deposition regression)
(million lbs.
TN
/year)
Annual Concentrations in Atmospheric Deposition
y = 2E-06x + 0.1795
R2 = 7E-07
y = -0.0053x + 10.971
R2 = 0.5641
y = -0.0053x + 10.791
R2 = 0.7061
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
1980 1985 1990 1995 2000 2005 2010
Year
mg
/l
NH3
NO3
DIN
Linear (NH3)
Linear (DIN)
Linear (NO3)
Before and After Implementation of Title IV of the Clean Air Act Amendments of 1990
Mean Annual Wet Deposition of Nitrate
Before: 1983-1994 After: 1995-2004
Nitrate ion wet deposition, 2004
Frequency of Occurrence of Nitrate Concentrations at AirMON Stations in the Chesapeake Watershed
NO3- ≥ 100 microequivalents/liter
NO3- ≥ 10 & < 100 microequivalents/liter
NO3- < 10 microequivalents/liter
Nitrogen Oxides Emissions from Sources Affected by Title IV of the Clean Air Act Amendments
Nitrogen Oxides Emissions from All Point and Area Sources in the United States
Counties:
Land Segments
A11001, District of Columbia
A24047, Worcester County, PA
A42015, Bradford County, PA
B42027, Centre County, PA
B51165, Rockingham County, VA
Bradford County, PA
y = -0.0025x + 5.2162
R2 = 0.7219
y = -0.0023x + 4.6334
R2 = 0.7977
y = -0.0003x + 0.5828
R2 = 0.1609
0
0.05
0.1
0.15
0.2
0.25
1980 1985 1990 1995 2000 2005 2010
An
nu
al C
on
cen
trat
ion
(m
g/l)
usgs nh4 FWC
usgs no3 fwc
usgs din fwc
Linear (usgs din fwc)
Linear (usgs no3 fwc)
Linear (usgs nh4 FWC)
Centre County PA
y = -0.0021x + 4.2597
R2 = 0.4682
y = -0.0018x + 3.7794
R2 = 0.6413
y = -0.0002x + 0.4803
R2 = 0.0476
0
0.02
0.04
0.06
0.08
0.1
0.12
0.14
0.16
0.18
0.2
1980 1985 1990 1995 2000 2005 2010
An
nu
al C
on
cen
trat
ion
(m
g/l)
usgs nh4 FWC
usgs no3 fwc
usgs din fwc
Linear (usgs din fwc)
Linear (usgs no3 fwc)
Linear (usgs nh4 FWC)
Washington, DC
y = -0.0019x + 3.9617
R2 = 0.4723
y = -0.0015x + 3.0884
R2 = 0.7248 y = -0.0004x + 0.8733
R2 = 0.0773
0
0.02
0.04
0.06
0.08
0.1
0.12
0.14
0.16
0.18
1980 1985 1990 1995 2000 2005 2010
An
nu
al C
on
cen
trat
ion
(m
g/l)
usgs nh4 FWC
usgs no3 fwc
usgs din fwc
Linear (usgs din fwc)
Linear (usgs no3 fwc)
Linear (usgs nh4 FWC)
Worcester County, MD
y = -0.0008x + 1.5958
R2 = 0.2359
y = -0.0009x + 1.889
R2 = 0.5688
y = 0.0002x - 0.2932
R2 = 0.0545
0
0.02
0.04
0.06
0.08
0.1
0.12
0.14
1980 1985 1990 1995 2000 2005 2010
An
nu
al C
on
cen
trat
ion
(m
g/l)
usgs nh4 FWC
usgs no3 fwc
usgs din fwc
Linear (usgs din fwc)
Linear (usgs no3 fwc)
Linear (usgs nh4 FWC)
Western Rockingham County, VA
y = -0.0021x + 4.2155
R2 = 0.5492
y = -0.0019x + 3.8014
R2 = 0.6739
y = -0.0002x + 0.4141
R2 = 0.0667
0
0.02
0.04
0.06
0.08
0.1
0.12
0.14
0.16
0.18
1980 1985 1990 1995 2000 2005 2010
An
nu
al C
on
cen
trat
ion
(m
g/l)
usgs nh4 FWC
usgs no3 fwc
usgs din fwc
Linear (usgs din fwc)
Linear (usgs no3 fwc)
Linear (usgs nh4 FWC)
Annual Concentrations in Atmospheric Deposition
y = 2E-06x + 0.1795
R2 = 7E-07
y = -0.0053x + 10.971
R2 = 0.5641
y = -0.0053x + 10.791
R2 = 0.7061
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
1980 1985 1990 1995 2000 2005 2010
Year
mg
/l
NH3
NO3
DIN
Linear (NH3)
Linear (DIN)
Linear (NO3)
Annual Concentrations in Atdep
y = 2E-06x + 0.1795
R2 = 7E-07
y = -0.0053x + 10.971
R2 = 0.5641
y = -0.0053x + 10.791
R2 = 0.7061
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
1980 1985 1990 1995 2000 2005 2010
Year
mg
/l
NH3
NO3
DIN
Linear (NH3)
Linear (DIN)
Linear (NO3)
The Airshed Model - CMAQ
Combining a regression model of wetfall deposition...
…with CMAQ estimates of dry deposition for the base…
…and using the power of the CMAQ model for scenarios.
The CMAQ Model allows us to estimate atmospheric deposition loads to the coastal ocean. Other assessments (Howarth,1998) are that atmospheric deposition loads are approximately roughly equivalent to watershed loads in the Northeast U.S. Considering the Northeast to include all watersheds from Maine to Virginia draining to the Atlantic, Howarth estimates that the watershed inputs of nitrogen to the Northeast coastal waters to be 0.27 teragrams (1012 grams). Inputs from direct atmospheric deposition to coastal waters are 0.21 teragrams, and inputs from deep ocean upwelling are 1.54 teragrams.
Coastal Ocean Boundary Condition
It’s recommended that the ocean boundary condition for nitrogen used in the WQSTM be reduced 7% when running simulations of the 2030 conditions of air controls and tributary strategies. As a point of interest, the loads under pristine conditions for the Northeast coastal waters are estimated to be 0.03, 0.01, and 1.57 teragrams for the watershed, direct deposition, and deep upwelling loads respectively.
Coastal Ocean Boundary Condition