Atmospheric Gas-Aerosol Equilibrium II. Analysis of Common Approximations and Activity Coefficient Calculation Methods

Kim, Yong Pyo; Seinfeld, John H.; Saxena, Pradeep

doi:10.1080/02786829308959629

Cited by 191 publications

(95 citation statements)

References 20 publications

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“…24 As shown in Figure 1, the line of zero excess NH 3 delineates the transition between NH 3 and HNO 3 limitation under all conditions, but the transition is not very sharp for a temperature of 303 K and an RH less than 80%. Even at temperatures from 293 to 303 K, the contours are less strictly vertical and horizontal than they are at 283 K and an RH of 80% or less.…”

Section: Simulation Of Equilibrium Aerosol Compositionmentioning

confidence: 87%

See 1 more Smart Citation

The Use of Ambient Measurements To Identify which Precursor Species Limit Aerosol Nitrate Formation

Blanchard¹,

Roth²,

Tanenbaum³

et al. 2000

Journal of the Air & Waste Management Association

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A thermodynamic equilibrium model was used to investigate the response of aerosol NO 3 to changes in concentrations of HNO 3 , NH 3 , and H 2 SO 4 . Over a range of temperatures and relative humidities (RHs), two parameters provided sufficient information for indicating the qualitative response of aerosol NO 3 . The first was the excess of aerosol NH 4 + plus gas-phase NH 3 over the sum of HNO 3 , particulate NO 3 , and particulate SO 4 2-concentrations. The second was the ratio of particulate to total NO 3 concentrations. Computation of these quantities from ambient measurements provides a means to rapidly analyze large numbers of samples and identify cases in which inorganic aerosol NO 3 formation is limited by the availability of NH 3 . Example calculations are presented using data from three field studies. The predictions of the indicator variables and the equilibrium model are compared.

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Section: Simulation Of Equilibrium Aerosol Compositionmentioning

confidence: 87%

“…The thermodynamically preferred forms of SO 4 2-are aqueous or solid Na 2 SO 4 and (NH 4 ) 2 SO 4 , and a key determinant of the equilibrium state is the molar ratio of total NH 4 + and Na + to SO 4 2-. 24 Systems in which [NH 3 …”

Section: Simulation Of Equilibrium Aerosol Compositionmentioning

confidence: 99%

The Use of Ambient Measurements To Identify which Precursor Species Limit Aerosol Nitrate Formation

Blanchard¹,

Roth²,

Tanenbaum³

et al. 2000

Journal of the Air & Waste Management Association

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“…For inorganic aerosols, the ISORROPIA equilibrium module 321 is used by CMAQ and CAMx models. The CIT model includes the SCAPE2 models 322 and WRF-Chem uses the MADE equilibrium module. 323 Secondary organic aerosol models also differ for the CIT 311 and CAMx 324 models, while CMAQ and WRF-Chem models use the formulation of Schell et al 325 A Master Chemical Mechanism (MCM) is being constructed using a large set of kinetics and product data for the elementary reaction steps of the VOC oxidation process.…”

Section: Air Quality Simulation Modelsmentioning

confidence: 99%

Megacities and Atmospheric Pollution

Molina

2004

Journal of the Air & Waste Management Association

656

371

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About half of the world's population now lives in urban areas because of the opportunity for a better quality of life. Many of these urban centers are expanding rapidly, leading to the growth of megacities, which are defined as metropolitan areas with populations exceeding 10 million inhabitants. These concentrations of people and activity are exerting increasing stress on the natural environment, with impacts at urban, regional and global levels. In recent decades, air pollution has become one of the most important problems of megacities. Initially, the main air pollutants of concern were sulfur compounds, which were generated mostly by burning coal. Today, photochemical smog-induced primarily from traffic, but also from industrial activities, power generation, and solvents-has become the main source of concern for air quality, while sulfur is still a major problem in many cities of the developing world. Air pollution has serious impacts on public health, causes urban and regional haze, and has the potential to contribute significantly to climate change. Yet, with appropriate planning, megacities can efficiently address their air quality problems through measures such as application of new emission control technologies and development of mass transit systems.This review is focused on nine urban centers, chosen as case studies to assess air quality from distinct perspectives: from cities in the industrialized nations to cities in the developing world. While each city-its problems, resources, and outlook-is unique, the need for a holistic approach to the complex environmental problems is the same. There is no single strategy in reducing air pollution in megacities; a mix of policy measures will be needed to improve air quality. Experience shows that strong political will coupled with public dialog is essential to effectively implement the regulations required to address air quality problems.

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“…[69] STEM-2K3 employs the SAPRC-99 [Carter, 2000] gaseous mechanism, aerosol thermodynamics module SCAPE II (Simulating Composition of Atmospheric Particles at Equilibrium) [Kim et al, 1993a[Kim et al, , 1993bKim and Seinfeld, 1995] and NCAR Tropospheric Ultraviolet-Visible (TUV) radiation model [Madronich and Flocke, 1999]. In this experiment, the STEM-2K3 model included aerosols in four size bins (in diameter): 0.1-0.3 mm, 0.3-1.0 mm, 1.0-2.5 mm, and 2.5-10 mm [Tang et al, 2004].…”

Section: A4 University Of Iowa Stem-2k3 Modelmentioning

confidence: 99%

An evaluation of real‐time air quality forecasts and their urban emissions over eastern Texas during the summer of 2006 Second Texas Air Quality Study field study

et al. 2009

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[1] Forecasts of ozone (O 3 ) and particulate matter (diameter less than 2.5 mm, PM 2.5 ) from seven air quality forecast models (AQFMs) are statistically evaluated against observations collected during August and September of 2006 (49 days) through the Aerometric Information Retrieval Now (AIRNow) network throughout eastern Texas and adjoining states. Ensemble O 3 and PM 2.5 forecasts created by combining the seven separate forecasts with equal weighting, and simple bias-corrected forecasts, are also evaluated in terms of standard statistical measures, threshold statistics, and variance analysis. For O 3 the models and ensemble generally show statistical skill relative to persistence for the entire region, but fail to predict high-O 3 events in the Houston region. For PM 2.5 , none of the models, or ensemble, shows statistical skill, and all but one model have significant low bias. Comprehensive comparisons with the full suite of chemical and aerosol measurements collected aboard the NOAA WP-3 aircraft during the summer 2006 Second Texas Air Quality Study and the Gulf of Mexico Atmospheric Composition and Climate Study (TexAQS II/GoMACCS) field study are performed to help diagnose sources of model bias at the surface. Aircraft flights specifically designed for sampling of Houston and Dallas urban plumes are used to determine model and observed upwind or background biases, and downwind excess concentrations that are used to infer relative emission rates. Relative emissions from the U.S. Environmental Protection Agency 1999 National Emission Inventory (NEI-99) version 3 emissions inventory (used in two of the model forecasts) are evaluated on the basis of comparisons between observed and model concentration difference ratios. Model comparisons demonstrate that concentration difference ratios yield a reasonably accurate measure (within 25%) of relative input emissions. Boundary layer height and wind data are combined with the observed up-wind and downwind concentration differences to estimate absolute emissions. When the NEI-99 inventory is modified to include observed NO y emissions from continuous monitors and expected NO x decreases from mobile sources between 1999 and 2006, good agreement is found with those derived from the observations for both Houston and Dallas. However, the emission inventories consistently overpredict the ratio of CO to NO y . The ratios of ethylene and aromatics to NO y are reasonably consistent with observations over Dallas, but are significantly underpredicted for Houston.

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Atmospheric Gas-Aerosol Equilibrium II. Analysis of Common Approximations and Activity Coefficient Calculation Methods

Cited by 191 publications

References 20 publications

The Use of Ambient Measurements To Identify which Precursor Species Limit Aerosol Nitrate Formation

The Use of Ambient Measurements To Identify which Precursor Species Limit Aerosol Nitrate Formation

Megacities and Atmospheric Pollution

An evaluation of real‐time air quality forecasts and their urban emissions over eastern Texas during the summer of 2006 Second Texas Air Quality Study field study

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