An Investigation of Ammonia and Inorganic Particulate Matter in California

during the CalNex Campaign

AGU Fall Meeting5 December 2012

Luke D. Schiferl, Colette L. Heald, John B. Nowak, John S. Holloway,

J. Andy Neuman, Roya Bahreini, Ann M. Middlebrook, Christine Wiedinmyer, and Stuart A. McKeen

Funding:

NH3SOX NOX

Emissions

Gas-Particle Partitioning

NH3

H2SO4

HNO3

NH4+

SO42-

NO3-

Deposition

Dry Wet

Transport

NH3

California: High Nitrogen Environment

PM2.5 Human Population Increase from 2010

by 2020 2040

20 %10 %

60 %15 %

[State of California, 2012]

01 – 6,2976,298 – 12,41912,420 – 23,95523,956 – 39,79239,793 – 87,028

[California Energy Commission, 2008]

[EPA, 2011]

LA

SFUrban + Rural N Sources

CalNex Field StudyMay-June 2010

NOAA WP-3D aircraft18 flights

Species Measurement Technique Resolution

NH3chemical ionization mass

spectrometry

1 sSO2 pulsed UV fluorescence

HNO3chemical ionization mass

spectrometry

NH4+

aerosol mass spectrometry 10 sSO4

2-

NO3-

Used in this analysis

GEOS-Chem chemical transport model used to interpret observations

• Driven by assimilated meteorology• 0.5° x 0.667° horizontal resolution

over North America

• NEI-2005 anthropogenic emissions

SOX

Altitude[km]

NH3 NOX

[Mg N/mo]

May

[Mg S/mo] [Mg N/mo]

Comparing CalNex Observations with GEOS-Chem Simulation

City Valley

ValleyN ≈ 800

CityN ≈ 1600

CalNex ObsModel

CalNex ObsModel

Median Concentrations Shown

NH3SOx NOx

Emissions

Gas-Particle Partitioning

NH3

H2SO4

HNO3

NH4+

SO42-

NO3-

Deposition

Dry Wet

Transport

NH3

Simulating Gas-Particle Partitioning

ISORROPIA IINHx

SO42-

TNO3

Na+

Cl-

TRH

NH3

NH4+

HNO3

NO3-

GEOS-Chem

H2SO4 + NH3

HNO3 + NH3

2 NH4+

SO42-

NH4 +

NO3-

If remaining NH3…First…

f(T, RH, ions)

GEOS-Chem T and RH v. CalNex ObservationsValleyCity

Fountoukis and Nenes [2007]

CalNex ObsModel

CalNex ObsModel

+/- 1 °C

Simulation is Insensitive to Temperature Uncertainty

ValleyCityCalNex Obs

ModelISORROPIA

+/- 1 °C

CalNex ObsModel

ISORROPIA +/- 1 °C

Uncertainty in RH Produces Small Differences in Ammonium Nitrate

City Valley

+/- 10 % RH

CalNex ObsModel

ISORROPIA +/- 10 % RH

CalNex ObsModel

ISORROPIA +/- 10 % RH

Simulated N Deposition in GEOS-Chem

Nitrogen Deposition Dominated by Dry Removal Processes during CalNex

Wet Deposition Dry Deposition

May

June

California

Wet Dry

NH3

NH4+

HNO3

NO3-

Total Deposition11.7 [Gg N/mo]

Virtually no summertime wet deposition confirmed by NADP measurements

NHX

May/June Mean

[Mg N/mo]

GEOS-Chem v. CASTNET Simulated Dry Deposition Velocity Evaluating Dry Deposition

CASTNET: May-June 2007-2009

0.5x SO2 Dry Deposition Velocity v. CalNex Observations

City

ValleyCity

CalNex ObsModel

Modified Model Dep

CASTNET Sites

*NH3 deposition not measured by CASTNET

Scaling Up EmissionsAll NEI-2005

Sources Livestock

5x Livestock - EverywhereEast LA Livestock to 12 Gg yr-1

3x - North Valley10x - South Valley

NH3

SO2

Modified Anthropogenic Emissions

Nowak et al. [2012]

[Mg N/mo]May

[Mg S/mo]May

Increasing Emissions Reduces Model Bias in California

City Valley

CalNex ObsModel

Modified Model Emissions

CalNex ObsModel

Modified Model Emissions

Improved Simulation of Near-Surface Concentrations

Standard ModifiedCalNex Obs

Median, lowest 1 km

Standard ModifiedCalNex Obs

ValleyCity

Model Model

Implications in California

Surface Concentration Column Concentration

June

Dec

embe

r

Jun Dec

Mean, lowest 1 km

City Valley

Jun Dec

Export of Excess Ammonia

Ammonia and Seasonality of PM

NH3

Conclusions

Further exploration with NH3 satellite retrievals where observations limited

Investigate impacts of simulating NH3 bi-directional flux

Emissions of ammonia and sulfur dioxide are underestimatedin California for May/June.

Simulated June PM concentrations higher in LA than in the Valley; NH3 critical for this formation

Reverse situation in December: LA becomes NH3 limited and Valley PM increases

Excess NH3 from Valley is exported downwind in spring/summer and potential exists for additional PM formation should acid levels increase

Future WorkSummertime 2009

IASI Column Concentration