Modeling the diurnal variation of nitrate during the Pittsburgh Air Quality Study

Satoshi Takahama, Ann E. Wittig, Dimitris V. Vayenas, Cliff I. Davidson, Spyros N. Pandis

Research output: Contribution to journalArticle

58 Scopus citations

Abstract

A thermodynamic model, the Gibbs Free-Energy Minimization model (GFEMN), was used to simulate the partitioning of PM2.5 nitrate aerosol and nitric acid using highly time-resolved inorganic measurements collected at the Pittsburgh Air Quality Study during July 2001 and January 2002. Model results were evaluated using independent, high time resolution measurements of aerosol nitrate. The mean observed concentration in July was 0.6 μg/m3 and 2.1 μg/m 3 in January. Model predictions were in agreement with the observations within 0.5 μg/m3 on average, with measurement uncertainties often accounting for these discrepancies. The simulations were run assuming particles were liquid in July for all relative humidities (RHs) and solid below 60% RH in January. For both seasons the assumed physical state did not influence considerably the overall agreement with observations. The assumption of particle mixing state did appear to influence model error; however, assuming that particles were externally mixed during low RH periods in July improved agreement significantly. The exceptional sensitivity of predicted aerosol nitrate to ammonia in western Pennsylvania suggests that reductions in PM2.5 may be assisted by reductions in ammonia emissions.

Original languageEnglish (US)
Pages (from-to)D16S06 1-10
JournalJournal of Geophysical Research D: Atmospheres
Volume109
Issue number16
DOIs
StatePublished - Aug 27 2004

Keywords

  • Aerosol
  • Nitrate
  • Pittsburgh Air Quality Study

ASJC Scopus subject areas

  • Geophysics
  • Forestry
  • Oceanography
  • Aquatic Science
  • Ecology
  • Water Science and Technology
  • Soil Science
  • Geochemistry and Petrology
  • Earth-Surface Processes
  • Atmospheric Science
  • Earth and Planetary Sciences (miscellaneous)
  • Space and Planetary Science
  • Palaeontology

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