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