ROMANS Nitrogen Source Sensitivity Analysis

Mike Barna1

Marco Rodriguez2

Kristi Gebhart1

Bill Malm1

Bret Schichtel1

Jenny Hand2

1 ARD-NPS, Fort Collins, CO2 CIRA, Fort Collins, CO

WRAP Workshop on Regional Emissions & Air Quality ModelingDenver, CO29-30 July 2008

National Park ServiceU.S. Department of the Interior Cooperative Institute

for Research in the Atmosphere

2

• N deposition increasing in the Rocky Mountains

• Alpine ecosystems are susceptible to extra N– N acts as a fertilizer →

ecosystem change– changes may be hard to

reverse– most deposition occurs as

wet dep (~2/3)

• critical load: 1.5 kg/ha/yr

Nitrogen deposition at RMNP

3

• Complex (small scale) diurnal and seasonal mountain circulation patterns.

• Vertical de-coupling due to inversions and stagnation in valleys.

• Orographic precipitation & isolated convective storms

• Lack of observations in remote mountainous areas.

• We still want accurate modeled winds, moisture, temperature, precip for CAMx, trajectories.

Rocky Mountains = magnificent views, fragile ecosystem, complex met

4

• Two field campaigns conducted during spring (April) and summer (July – Aug) of 2006

• Measure concentration and wet dep of important N and S species: NH4, NO3, NH3, NOx, SO4

ROMANS: Rocky Mountain Atmospheric Nitrogen & Sulfur Study

5

Where is the nitrogen coming from?

National Park ServiceU.S. Department of the Interior

Cooperative Institute for Research in the Atmosphere

• local v. regional v. distant?

• oxidized or reduced?

6

Modeling & data analysis ROMANS

• Back trajectories

• Airmass conditional probability

• Dry deposition of ‘missing’ nitrogen

• Tracer simulations -> EOF analysis (Bill Malm)

• ‘Lagrangian process analysis’

• Base case simulation

• Source apportionment of N and S with PSAT

• ‘Hybrid modeling’ (Bret Schichtel)

….at the end, need to reconcile results from these different analyses

7

Domain 136 Km

165 x 129

Domain 212 Km

103 x 115

Domain 34 Km

163 x 118

35 layers – 34 from WRAP, plus a 10-m layer

Applying CAMx in ROMANS

• 36/12/4 km domains

• Met from obs-nudged MM5

• Emissions based on updated 2002 WRAP inventory

8

Distribution of NH3, NO3NH3:•Rapidly dry deposits•Emissions very uncertain•Strong spatial gradients

NO3:•Longer lifetime•Particle or gas phase

9

NH4+

NO3

SO4=

NH3

HNO3

SO2

Beaver Meadows (RMNP) Grant, Nebraska

April 2006 ROMANS base case

10

Rocky Mountain National Park Beginning Apr. 23, 2006 hr 11 (jd 113)Started During Next 1 Hrs, 5 Day Length

‘Lagrangian process analysis’

NH3 Non-transport processes

-8.00

-6.00

-4.00

-2.00

0.00

2.00

4.00

6.00

8.00

10.00

HR0 HR24 HR48 HR72 HR96 HR120

(pp

b)

NH3-Emissions

NH3-Wet deposition

NH3-dry deposition

NH3-inorganic aerosol chemistry

NH3-gas phase chemistry

PNH4 Non-transport processes

-0.20

-0.15

-0.10

-0.05

0.00

0.05

0.10

0.15

0.20

0.25

0.30

0.35

HR0 HR24 HR48 HR72 HR96 HR120

(ug

/m3)

Emissions

Wet deposition

dry deposition

inorganic aerosol chemistry

gas phase chemistry

What processes influence the concentration within an airmass during its trajectory to RMNP?

•Wet and dry deposition•Emissions•Gas and aerosol chemistry

NH3

NH4+

11

– Sulfur species

• SO2i Primary SO2 emissions

• PS4i Particulate sulfate ion from primary emissions plus secondarily formed sulfate

– Nitrogen species

• RGNi Reactive gaseous nitrogen including primary NOx (NO + NO2) emissions plus nitrate radical (NO3), nitrous acid (HONO) and dinitrogen pentoxide (N2O5).

• TPNi Gaseous peroxyl acetyl nitrate (PAN) plus peroxy nitric acid (PNA)

• NTRi Organic nitrates (RNO3)

• HN3i Gaseous nitric acid (HNO3)

• PN3i Particulate nitrate ion from primary emissions plus secondarily formed nitrate

– Ammonia/ammonium

• NH3i Gaseous ammonia (NH3)

• PN4i Particulate ammonium (NH4)

CAMx PSAT source apportionment

12

CAMx tracer simulations

• ~100 source regions

• Tracers for NH3, NOx, SO2

• Conserved, dry dep, wet dep, total dep

• Use with EOF’s

13

‘Missing nitrogen’ at RMNP

• N dry deposition at RMNP based on CASTNet

• Only three N species are typically ‘measured’ for dry deposition: NH4+, NO3- and HNO3

• What happens when we consider the dry deposition of total N at RMNP?

• Oxidized N (the NOy budget):

• NOx, HNO3, NO3-, PAN + other organic nitrates, HONO, nitrate radical + N2O5

• Reduced N:

• NH3, NH4+

• Simulate this ‘missing N’ with CAMx

14

Annual average modeled nitrogen concentration from CAMx for 2002

CASTNet species:

example ‘missing N’ species:

15

What happens to emitted NOx & NH3

• NH3: rapid deposition, NH3 NH4+, no gas-phase oxidation

• NOx: complicated photochemistry, HNO3 NO3-, some species rapidly deposit (HNO3, NO.)

NH3 NOx

16

CAMx total N vs CASTNet N at RMNP

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0.050

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0.350

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Feb

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Dec

2002

ug

-N/m

3pred total red N [ug/m3] ob total red N [ug/m3]

0.000

0.050

0.100

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0.250

Jan

Feb

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2002

kg

-N/h

a

pred total ox N DDep [kg/ha] ob total ox N DDep [kg/ha]

0.000

0.500

1.000

1.500

2.000

2.500

Jan

Feb

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2002

ug

-N/m

3

pred total ox N [ug/m3] ob total ox N [ug/m3]

0.000

0.010

0.020

0.030

0.040

0.050

0.060

0.070

0.080

0.090

Jan

Feb

Mar

Apr

May

Jun

Jul

Aug

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Oct

Nov

Dec

2002

kg

-N/h

a

pred total red N DDep [kg/ha] ob total red N DDep [kg/ha]

Total Reduced N (NH3 + NH4+): Total Oxidized N (NOy):

Conc:

DryDep:

17

Modeled dry deposition at RMNP

0.00

0.05

0.10

0.15

0.20

0.25

0.30

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

2002

Nit

rog

en

Dry

De

po

sit

ion

[k

g/h

a]

N-PNO3

N-PNH4

N-NOx

N-PAN

N-NxOy

N-Org N

N-NH3

N-HONO

N-HNO3

18

Modeled dry deposition at RMNP

N-NOx4%

N-PAN3%

N-NxOy10%

N-Org N2%

N-NH328%

N-HONO0%

N-PNO30%

N-HNO353%

N-PNH40%

19

CASTNet v. CAMx dry dep velocities

CASTNet[cm/s]

CAMx[cm/s] Reference Values

HNO3 1.8 6.2 7.51 (conifer forest)3-62

1-53

NH3 N/A 7.5 0.6-3 (low vegetation)4

2-20 (high vegetation)4

NO2 N/A 0.11 0.13

0.1-0.55

OrgN N/A 0.18

NxOy N/A 5.6

PAN N/A 0.08

PM 0.20 0.03 <0.53

0.1 – 0.52

0.01 – 0.26 (grassland)0.1–16 (forest)

1P

ryor et al., 20042

Duyzer et al., 1992

3F

inlayson-Pitts and P

itts, 1999

4A

sman, 2004

5S

einfeld and Pandis, 2006

6P

ryor et al., 2008

20

Yearly CAMx and CASTNet estimates of dry deposited N at RMNP for 2002

0.0

0.5

1.0

1.5

2.0

2.5

[HNO3,NO3,NH4] [HNO3,NO3,NH4] [Total N]

CASTNet CAMX CAMX

N D

ry D

epo

siti

on

[kg

/ha/

yr]

N-PNO3

N-PNH4

N-NOx

N-PAN

N-NxOy

N-Org N

N-NH3

N-HONO

N-HNO3

21

Summary

• Nitrogen deposition is increasing at RMNP –> ROMANS

• Numerous approaches applied to N source apportionment at RMNP

• Receptor models

• Deterministic models

• EOF analysis

• Hybrid approach

• No single technique will provide the entire answer – need to reconcile

22

Summary (cont’d)

• Can’t get enough simulated N to RMNP

• Nitric acid estimates not bad

• PM N (NH4 and NO3) underestimated

• Not capturing the late spring upslope event, although tracer transport ok

• Use ‘lagrangian process analysis’ to investigate this – chemistry, deposition or emissions?

23

Summary (cont’d)

• Accounting for ‘missing’ nitrogen can almost double the estimated dry deposition at RMNP for 2002 (1.2 vs 2.2 kg/ha/yr).

Species N-flux [kg/ha yr] contribution

HNO3 1.16 53%

NH3 0.60 28%

NxOy 0.22 10%

PAN + Org N 0.11 5%

Other N species 0.12 6%

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25

CAMx bias relative to CASTNet:HNO3

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2002

ug

-N/m

3

pred N-HNO3 [ug/m3] ob N-HNO3 [ug/m3]

0.000

0.020

0.040

0.060

0.080

0.100

0.120

0.140

0.160

0.180

Jan

Feb

Mar

Apr

May

Jun

Jul

Aug

Sep

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Nov

Dec

2002

kg

-N/h

a

pred N-HNO3 DDep [kg/ha] ob N-HNO3 DDep [kg/ha]

26

0.000

0.050

0.100

0.150

0.200

0.250

0.300

0.350

Jan

Feb

Mar

Apr

May

Jun

Jul

Aug

Sep

Oct

Nov

Dec

2002

ug

-N/m

3

pred N-PNH4 [ug/m3] ob N-PNH4 [ug/m3]

0.000

0.005

0.010

0.015

0.020

0.025

Jan

Feb

Mar

Apr

May

Jun

Jul

Aug

Sep

Oct

Nov

Dec

2002

kg

-N/h

a

pred N-PNH4 DDep [kg/ha] ob N-PNH4 DDep [kg/ha]

CAMx bias relative to CASTNet:NH4+

27

0.000

0.050

0.100

0.150

0.200

0.250

Jan

Feb

Mar

Apr

May

Jun

Jul

Aug

Sep

Oct

Nov

Dec

2002

ug

-N/m

3

pred N-PNO3 [ug/m3] ob N-PNO3 [ug/m3]

0.000

0.002

0.004

0.006

0.008

0.010

0.012

Jan

Feb

Mar

Apr

May

Jun

Jul

Aug

Sep

Oct

Nov

Dec

2002

kg

-N/h

a

pred N-PNO3 DDep [kg/ha] ob N-PNO3 DDep [kg/ha]

CAMx bias relative to CASTNet:NO3+