Atmospheric ammonia and particulate inorganic nitrogen over the United States

Heald, Colette L.; Collett, Jeffrey L.; Lee, Taesam; Benedict, K. B.; Schwandner, F. M.; Li, Yulun; Clarisse, Lieven; Hurtmans, Daniel; Damme, Martin Van; Clerbaux, Cathy; Coheur, Pierre‐François; Philip, Sajeev; Martin, Randall V.; Pye, Havala O. T.

doi:10.5194/acp-12-10295-2012

Cited by 253 publications

(308 citation statements)

References 76 publications

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“…Over-prediction of nitrate and ammonium aerosol in the eastern and midwestern states in this study is consistent with results found by Zhang et al (2012) and Heald et al (2012). Nitrate aerosol is formed in thermodynamic equilibrium with gas-phase ammonia and nitric acid.…”

Section: Nitrate Over-prediction In the Midwest/eastsupporting

confidence: 80%

“…We note especially the study of Heald et al (2012), completed at essentially the same time as the present work, which addresses a number of the same issues and reports results generally consistent with those presented here.…”

supporting

confidence: 76%

“…Heald et al (2012) found that GEOS-Chem simulation of nitrate aerosol over the midwestestern and eastern states is nitric acid-limited and that the positive nitrate bias is likely linked with an overestimate of nitric acid concentrations: when they reduced nitric acid concentrations to 75 % of their simulated values in GEOS-Chem, this reduction corrected the bias in simulated nitrate and ammonium aerosol over the Midwest and East. In addition to the uncertainties in N 2 O 5 hydrolysis, Heald et al (2012) investigated other possible causes for an overestimate of nitric acid concentrations, including: uncertainties in daytime formation of HNO 3 arising from uncertainties in emissions of NO x , concentrations of OH, or the rate of NO 2 oxidation by OH, and uncertainties in the dry deposition removal rates of nitric acid. They found that none of these uncertainties could fully account for the reduction in HNO 3 required to correct the nitrate bias.…”

Section: Nitrate Over-prediction In the Midwest/eastmentioning

confidence: 99%

“…This bias causes GEOS-5 driven GEOS-Chem simulations to predict an artificially large build up of aerosols at night and corresponding high biases in predicted daily and monthly average concentrations. To correct this issue, we have modified the model to define a minimum mechanical mixing depth, calculated based on the local friction velocity (Lin and McElroy, 2010;Koracin and Berkowicz, 1988;Heald et al, 2012); any GEOS-5 mixed layer depths below this value are set to the minimum mechanical mixing depth. This modification yields nighttime mixed layer depths that are more consistent with observations (Liu and Liang, 2010), and more realistic diurnal variations in predicted aerosol concentrations.…”

Section: Geos-chem Modelmentioning

confidence: 99%

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Simulation of nitrate, sulfate, and ammonium aerosols over the United States

et al. 2012

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Abstract. Atmospheric concentrations of inorganic gases and aerosols (nitrate, sulfate, and ammonium) are simulated for 2009 over the United States using the chemical transport model GEOS-Chem. Predicted aerosol concentrations are compared with surface-level measurement data from the Interagency Monitoring of Protected Visual Environments (IMPROVE), the Clean Air Status and Trends Network (CASTNET), and the California Air Resources Board (CARB). Sulfate predictions nationwide are in reasonably good agreement with observations, while nitrate and ammonium are over-predicted in the East and Midwest, but underpredicted in California, where observed concentrations are the highest in the country. Over-prediction of nitrate in the East and Midwest is consistent with results of recent studies, which suggest that nighttime nitric acid formation by heterogeneous hydrolysis of N 2 O 5 is over-predicted based on current values of the N 2 O 5 uptake coefficient, γ , onto aerosols. After reducing the value of γ by a factor of 10, predicted nitrate levels in the US Midwest and East still remain higher than those measured, and over-prediction of nitrate in this region remains unexplained. Comparison of model predictions with satellite measurements of ammonia from the Tropospheric Emissions Spectrometer (TES) indicates that ammonia emissions in GEOS-Chem are underestimated in California and that the nationwide seasonality applied to ammonia emissions in GEOS-Chem does not represent California very well, particularly underestimating winter emissions. An ammonia sensitivity study indicates that GEOS-Chem simulation of nitrate is ammonia-limited in southern California and much of the state, suggesting that an underestimate of ammonia emissions is likely the main cause for the underprediction of nitrate aerosol in many areas of California. An approximate doubling of ammonia emissions is needed to reproduce observed nitrate concentrations in southern California and in other ammonia sensitive areas of California. However, even a tenfold increase in ammonia emissions yields predicted nitrate concentrations that are still biased low in the central valley of California. The under-prediction of nitrate aerosol in the central valley of California may arise in part from an under-prediction of both ammonia and nitric acid in this region. Since nitrate aerosols are particularly sensitive to mixed layer depths, owing to the gas-particle equilibrium, the nitrate under-prediction could also arise in part from a potential regional overestimate of GEOS-5 mixed layer depths in the central valley due to unresolved topography in this region.

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Section: Nitrate Over-prediction In the Midwest/eastsupporting

confidence: 80%

supporting

confidence: 76%

Section: Nitrate Over-prediction In the Midwest/eastmentioning

confidence: 99%

Section: Geos-chem Modelmentioning

confidence: 99%

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Simulation of nitrate, sulfate, and ammonium aerosols over the United States

et al. 2012

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“…comparisons between measured emissions and concentrations with model inventories found significant discrepancies (Heald et al, 2012;Nowak et al, 2012;Walker et al, 2012).…”

Section: J Miller Et Al: Open-path Qcl-based Ammonia Sensormentioning

confidence: 99%

Open-path, quantum cascade-laser-based sensor for high-resolution atmospheric ammonia measurements

et al. 2014

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Abstract. We demonstrate a compact, open-path, quantum cascade-laser-based atmospheric ammonia sensor operating at 9.06 µm for high-sensitivity, high temporal resolution, ground-based measurements. Atmospheric ammonia (NH 3 ) is a gas-phase precursor to fine particulate matter, with implications for air quality and climate change. Currently, NH 3 sensing challenges have led to a lack of widespread in situ measurements. Our open-path sensor configuration minimizes sampling artifacts associated with NH 3 surface adsorption onto inlet tubing and reduced pressure sampling cells, as well as condensed-phase partitioning ambiguities. Multi-harmonic wavelength modulation spectroscopy allows for selective and sensitive detection of atmospheric pressurebroadened absorption features. An in-line ethylene reference cell provides real-time calibration (±20 % accuracy) and normalization for instrument drift under rapidly changing field conditions. The sensor has a sensitivity and noise-equivalent limit (1σ ) of 0.15 ppbv NH 3 at 10 Hz, a mass of ∼ 5 kg and consumes ∼ 50 W of electrical power. The total uncertainty in NH 3 measurements is 0.20 ppbv NH 3 ± 10 %, based on a spectroscopic calibration method. Field performance of this open-path NH 3 sensor is demonstrated, with 10 Hz time resolution and a large dynamic response for in situ NH 3 measurements. This sensor provides the capabilities for improved in situ gas-phase NH 3 sensing relevant for emission source characterization and flux measurements.

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An investigation of ammonia and inorganic particulate matter in California during the CalNex campaign

Schiferl

Heald

Nowak

et al. 2014

J. Geophys. Res. Atmos.

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Airborne observations from the California Research at the Nexus of Air Quality and ClimateChange (CalNex) campaign in May and June 2010 are used to investigate the role of ammonia (NH 3 ) in fine particulate matter (PM 2.5 ) formation and surface air quality in California and test the key processes relevant to inorganic aerosol formation in the GEOS-Chem model. Concentrations of ammonia throughout California, sulfur dioxide (SO 2 ) in the Central Valley, and ammonium nitrate in the Los Angeles (LA) area are underestimated several-fold in the model. We find that model concentrations are relatively insensitive to uncertainties in gas-particle partitioning and deposition processes in the region. Conversely, increases to anthropogenic livestock ammonia emissions (by a factor of 5) and anthropogenic sulfur dioxide emissions in the Central Valley (by a factor of 3-10) and a reduction of anthropogenic NO x emissions (by 30%) substantially reduce the bias in the simulation of gases (SO 2 , NH 3 , HNO 3 ) throughout California and PM 2.5 near LA, although the exact magnitudes of emissions in the region remain uncertain. Using these modified emissions, we investigate year-round PM 2.5 air quality in California. The model reproduces the wintertime maximum in surface ammonium nitrate concentrations in the Central Valley (regional mean concentrations are three times higher in December than in June), associated with lower planetary boundary layer heights and colder temperatures, and the wintertime minimum in the LA region (regional mean concentrations are two times higher in June than December) associated with ammonia limitation. Year round, we attribute at least 50% of the inorganic PM 2.5 mass simulated throughout California to anthropogenic ammonia emissions.

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Atmospheric ammonia and particulate inorganic nitrogen over the United States

Cited by 253 publications

References 76 publications

Simulation of nitrate, sulfate, and ammonium aerosols over the United States

Simulation of nitrate, sulfate, and ammonium aerosols over the United States

Open-path, quantum cascade-laser-based sensor for high-resolution atmospheric ammonia measurements

An investigation of ammonia and inorganic particulate matter in California during the CalNex campaign

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