Final Report: Research Consortium on Ozone and Fine Particle Formation in California and in the Northeastern United States: Carnegie Mellon Report

EPA Grant Number: R826371C005
Subproject: this is subproject number 005 , established and managed by the Center Director under grant R826371
(EPA does not fund or establish subprojects; EPA awards and manages the overall grant for this center).

Center: Research Consortium on Ozone and Fine Particle Formation in California and in the Northeastern United States
Center Director: Seinfeld, John
Title: Research Consortium on Ozone and Fine Particle Formation in California and in the Northeastern United States: Carnegie Mellon Report
Investigators: Pandis, Spyros N.
Institution: Carnegie Mellon University
EPA Project Officer: Shapiro, Paul
Project Period: April 15, 1998 through April 14, 2003
RFA: Special Opportunity in Tropospheric Ozone (1997) RFA Text |  Recipients Lists
Research Category: Air Quality and Air Toxics , Air

Objective:

The objective of this research project was directed toward improving the microphysical treatment of aerosols in atmospheric models.

Summary/Accomplishments (Outputs/Outcomes):

Inorganic Aerosol Modeling. Four inorganic aerosol thermodynamics models were evaluated for use in atmospheric particulate matter (PM) models. Three of them (ISORROPIA, SCAPE2, and SEQUILIB) are computationally efficient, while the fourth (GFEMN) is used as a benchmark. The predictions of the models were intercompared for the full composition/temperature/relative humidity space and also against measurements from Southern California. ISORROPIA was determined to combine accuracy with computational speed and is the recommended model of choice for use in large-scale air quality models (Ansari and Pandis, 1999).

At RH below 70 percent atmospheric aerosols may exist as either solid particles or as highly concentrated aqueous solutions. For a range of atmospheric conditions, both states are thermodynamically possible. The importance of the existence of metastable equilibrium states on the partitioning of nitrate between the gas and aerosol phases was investigated (Ansari and Pandis, 2000a). The potential existence of metastable aerosols in Southern California, where pollutant levels are high, appears to have a small effect on total nitrate partitioning. However, for areas characterized by moderate-to-low pollutant levels, such as the Northeastern United States, a significant effect is predicted.

A novel approach to the modeling of the mass transfer of semivolatile species was developed (Capaldo, et al., 2000). The hybrid method utilizes equilibrium assumptions for the fine aerosol mode (particles with diameter less than 1 µm), and the dynamic approach for the coarse aerosol mode. The hybrid method maintains most of the predictive ability of the dynamic approach and is 50 times more computationally efficient.

The partitioning of nitrate and ammonium between the gas and particulate phases was studied combining the models developed in this project and measurements taken in Mexico City during the 1997 IMADA-AVER field campaign (Moya, et al., 2001). Atmospheric equilibrium models predict daily average PM2.5 nitrate concentrations within 20 percent of the IMADA-AVER measurements. Six-hour average PM2.5 nitrate concentrations are predicted within 30-50 percent on average, except for the afternoon sampling periods (12:00-18:00). Investigating the possible sources of these discrepancies, it appears that a dynamic rather than an equilibrium approach is more suitable in reproducing aerosol behavior during these afternoon periods in Mexico City.

A size-resolved equilibrium model, SELIQUID, was developed and used to simulate the size-composition distribution of semivolatile inorganic aerosol in an urban environment (Moya, et al., 2002). Predictions of SELIQUID were compared against size-resolved composition measurements at different locations during the Southern California Air Quality Study. Based on the modeling results, the size distribution of submicrometer nitrate and ammonium can be determined by thermodynamic equilibrium only when the RH exceeds 60 percent. On the other hand, the equilibrium assumption, in some cases at least, introduces errors in the calculation of the coarse nitrate and ammonium that increase with particle size.

The Trajectory-Grid approach of Chock and Winkler was modified and implemented in the Hybrid and Dynamic module (Gaydos, et al., 2003). The modules were incorporated into PMCAMx (a 3D chemical transport module) and evaluated against measurements collected in Southern California during 1987 and 1995. The improved modules were approximately 10 times more computationally efficient than their older versions. The model predictions agreed with measured concentrations of the major aerosol components within 30 percent.

Organic-Inorganic Aerosol Modeling. An integrated modeling approach was developed combining available secondary organic aerosols (SOA) and inorganic aerosol models to predict overall aerosol behavior (Ansari and Pandis, 2000b). The effect of SOA on water absorption and nitrate partitioning between the gas and aerosol phases was determined. On average, it appears that SOA accounts for approximately 7 percent of total aerosol water and increases aerosol nitrate concentrations by approximately 10 percent. At high relative humidity (>85 percent) and low SOA mass fractions (<20 percent of total PM2.5), the role of SOA in nitrate partitioning and its contribution to total aerosol water is negligible. At low relative humidity (~50 percent) and high SOA mass fraction concentrations (~30 percent of total PM2.5), SOA is predicted to account for approximately 20 percent of total aerosol water and a 50 percent increase in aerosol nitrate concentrations.

A series of modeling approaches for the description of the dynamic behavior of SOA and its interactions with the inorganic components was investigated (Koo, et al., 2003). The models employ a lumped species approach based on available smog chamber studies and the UNIFAC group contribution method. The SOA size distribution predicted by the traditional bulk equilibrium approach is biased towards smaller sizes compared with that of a fully dynamic model. An improved weighting scheme for the bulk equilibrium approach is proposed in this work and is shown to minimize this discrepancy.

Aqueous Phase Chemistry Modeling. Given that bulk aqueous-phase chemistry models are less computationally intensive than corresponding size-resolved models, a model equipped to combine the accuracy of the size-resolved code with the efficiency of the bulk method has been developed. Bulk and two-section size-resolved approaches are combined into a single variable size-resolution model (VSRM) to combine both accuracy and computational speed (Fahey and Pandis, 2001). Depending on initial system conditions, bulk or size-resolved calculations are executed based on a set of semi-empirical rules. For the conditions examined, on average, the VSRM sulfate predictions are within 3 percent of a six-section size-resolved model, but the VSRM is 15 times faster.


Journal Articles on this Report : 11 Displayed | Download in RIS Format

Other subproject views: All 12 publications 11 publications in selected types All 11 journal articles
Other center views: All 49 publications 46 publications in selected types All 46 journal articles
Type Citation Sub Project Document Sources
Journal Article Ansari AS, Pandis SN. An analysis of four models predicting the partitioning of semivolatile inorganic aerosol components. Aerosol Science and Technology 1999;31(2-3):129-153. R826371 (Final)
R826371C005 (Final)
R824793 (Final)
  • Full-text: Taylor&Francis-Full Text PDF
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  • Abstract: Taylor&Francis-Abstract
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  • Journal Article Ansari AS, Pandis SN. Water absorption by secondary organic aerosol and its effect on inorganic aerosol behavior. Environmental Science & Technology 2000;34(1):71-77. R826371 (Final)
    R826371C005 (Final)
  • Full-text: ResearchGate-Abstract & Full Text
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  • Abstract: ACS-Abstract
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  • Other: ACS-Full Text PDF
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  • Journal Article Ansari AS, Pandis SN. The effect of metastable equilibrium states on the partitioning of nitrate between the gas and aerosol phases. Atmospheric Environment 2000;34(1):157-168. R826371C005 (Final)
    R824793 (Final)
  • Full-text: ScienceDirect-Full Text HTML
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  • Abstract: ScienceDirect-Abstract
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  • Other: ScienceDIrect-Full Text PDF
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  • Journal Article Capaldo KP, Pilinis C, Pandis SN. A computationally efficient hybrid approach for dynamic gas/aerosol transfer in air quality models. Atmospheric Environment 2000;34(21):3617-3627. R826371 (Final)
    R826371C005 (Final)
  • Full-text: ScienceDirect-Full Text HTML
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  • Abstract: ScienceDirect-Abstract
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  • Other: ScienceDirect-Full Text PDF
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  • Journal Article Fahey KM, Pandis SN. Optimizing model performance:variable size resolution in cloud chemistry modeling. Atmospheric Environment 2001;35(26):4471-4478. R826371 (Final)
    R826371C005 (Final)
  • Full-text: ScienceDirect-Full Text HTML
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  • Abstract: ScienceDirect-Abstract
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  • Other: ScienceDirect-Full Text PDF
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  • Journal Article Fahey KM, Pandis SN. Size-resolved aqueous-phase atmospheric chemistry in a three-dimensional chemical transport model. Journal of Geophysical Research: Atmospheres 2003;108(D22):4690, doi:10.1029/2003JD003564. R826371C005 (Final)
  • Abstract: Wiley-Abstract
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  • Journal Article Gaydos TM, Koo B, Pandis SN, Chock DP. Development and application of an efficient moving sectional approach for the solution of the atmospheric aerosol condensation/evaporation equations. Atmospheric Environment 2003;37(23):3303-3316. R826371 (Final)
    R826371C005 (Final)
  • Full-text: ScienceDirect-Full Text HTML
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  • Abstract: ScienceDirect-Abstract
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  • Other: ScienceDirect-Full Text PDF
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  • Journal Article Koo B, Gaydos TM, Pandis SN. Evaluation of the equilibrium, dynamic, and hybrid aerosol modeling approaches. Aerosol Science and Technology 2003;37(1):53-64. R826371 (Final)
    R826371C005 (Final)
    R831709 (2007)
    R831709C003 (2004)
  • Full-text: Taylor&Francis-Full Text PDF
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  • Abstract: Taylor&Francis-Abstract
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  • Journal Article Koo B, Ansari AS, Pandis SN. Integrated approaches to modeling the organic and inorganic atmospheric aerosol components. Atmospheric Environment 2003;37(34):4757-4768. R826371 (Final)
    R826371C005 (Final)
  • Full-text: ScienceDirect-Full Text PDF
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  • Abstract: ScienceDirect-Abstract
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  • Other: ResearchGate-Full Text HTML & PDF
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  • Journal Article Moya M, Ansari AS, Pandis SN. Partitioning of nitrate and ammonium between the gas and particulate phases during the1997 IMADA-AVER study in Mexico City. Atmospheric Environment 2001;35(10):1791-1804. R826371 (Final)
    R826371C005 (Final)
  • Full-text: ScienceDirect-Full Text PDF
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  • Abstract: ScienceDirect-Abstract and Full Text HTML
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  • Other: ResearchGate - Abstract & Full Text HTML
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  • Journal Article Moya M, Pandis SN, Jacobson MZ. Is the size distribution of urban aerosols determined by thermodynamic equilibrium? An approach to Southern California. Atmospheric Environment 2002;36(14):2349-2365. R826371 (Final)
    R826371C005 (Final)
  • Full-text: ScienceDirect-Full Text PDF
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  • Abstract: ScienceDirect-Abstract and Full Text HTML
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  • Other: ReserachGate - Full Text HTML & PDF
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  • Supplemental Keywords:

    aerosols, atmospheric models, inorganic aerosol modeling, Southern California, CA, secondary organic aerosols., RFA, Scientific Discipline, Air, Ecosystem Protection/Environmental Exposure & Risk, particulate matter, Environmental Chemistry, Monitoring/Modeling, Analytical Chemistry, tropospheric ozone, Atmospheric Sciences, aerosol formation, atmospheric particulate matter, atmospheric dispersion models, secondary aerosol formation, aqueous phase modeling, fine particles, secondary organic aerosols, airborne particulate matter, fine particulates, ozone, air sampling, air pollution models, air quality model, chemical composition, atmospheric aerosol particles, aersol particles, California, three dimensional model, atmospheric chemistry, ambient aerosol particles, fine particle formation, aerosol analyzers, air quality

    Progress and Final Reports:

    Original Abstract
  • 1998
  • 1999
  • 2000
  • 2001

  • Main Center Abstract and Reports:

    R826371    Research Consortium on Ozone and Fine Particle Formation in California and in the Northeastern United States

    Subprojects under this Center: (EPA does not fund or establish subprojects; EPA awards and manages the overall grant for this center).
    R826371C001 Research Consortium on Ozone and Fine Particle Formation in California and in the Northeastern United States: Cal Tech, UC-Riverside, UC-San Diego, UC-Davis Report
    R826371C002 Research Consortium on Ozone and Fine Particle Formation in California and in the Northeastern United States: Cal Tech, Carnegie Mellon, Georgia Institute, NJIT, Oregon Institute, UC-Irvine, UC-Riverside Report
    R826371C003 Research Consortium on Ozone and Fine Particle Formation in California and in the Northeastern United States: Cal Tech Report
    R826371C004 Research Consortium on Ozone and Fine Particle Formation in California and in the Northeastern United States: California - Irvine Report
    R826371C005 Research Consortium on Ozone and Fine Particle Formation in California and in the Northeastern United States: Carnegie Mellon Report
    R826371C006 Research Consortium on Ozone and Fine Particle Formation in California and in the Northeastern United States: Carnegie Mellon Report
    R826371C007 Research Consortium on Ozone and Fine Particle Formation in California and in the Northeastern United States: UC-Riverside
    R826371C008 Research Consortium on Ozone and Fine Particle Formation in California and in the Northeastern United States: Oregon Health and Science Report
    R826371C009 Research Consortium on Ozone and Fine Particle Formation in California and in the Northeastern United States: NJIT Report