Role of atmospheric ammonia in particulate matter formation in Houston during summertime

• Published in: Atmospheric environment (1994) 2013-10, Vol.77, p.893-900
• Main Authors: Gong, Longwen, Lewicki, Rafał, Griffin, Robert J., Tittel, Frank K., Lonsdale, Chantelle R., Stevens, Robin G., Pierce, Jeffrey R., Malloy, Quentin G.J., Travis, Severin A., Bobmanuel, Loliya M., Lefer, Barry L., Flynn, James H.
• Format: Article
• Language: English
• Subjects: Aerosol nucleation; Ammonia; Applied sciences; Atmospheric pollution; Exact sciences and technology; Gas-particle partitioning; Particulate matter; Pollutants physicochemistry study: properties, effects, reactions, transport and distribution; Pollution
• ISSN: 1352-2310; 1873-2844
• DOI: 10.1016/j.atmosenv.2013.04.079

Simultaneous high-time-resolution measurements of atmospheric NH3, HNO3, soluble gas-phase chloride, and aerosol species were made in Houston, TX, from August 5, 2010 to August 9, 2010. Gaseous NH3 was measured using a 10.4-μm external cavity quantum cascade laser-based sensor employing conventional photo-acoustic spectroscopy, while gaseous HNO3 and HCl were sampled using a mist chamber–ion chromatograph (IC) system. Particle chemical composition was determined using a particle-into-liquid-sampler–IC system. There was a large amount of variability in the gas phase mixing ratios of NH3 (3.0 ± 2.5 ppb), HNO3 (287.4 ± 291.6 ppt), and HCl (221.3 ± 260.7 ppt). Elevated NH3 levels occurred around mid-day when NH4+ (0.5 ± 1.0 μg m−3) and SO42− (4.5 ± 4.3 μg m−3) also increased considerably, indicating that NH3 likely influenced aerosol particle mass. By contrast, the formation of NH4NO3 and NH4Cl was not observed during the measurements. Point sources (e.g., power plant and chemical plant) might be potential contributors to the enhancements in NH3 at the measurement site under favorable meteorological conditions. Increased particle number concentrations were predicted by the SAM-TOMAS model downwind of a large coal-fired power plant when NH3 emissions (based on these measurements) were included, highlighting the potential importance of NH3 with respect to particle number concentration. Separate measurements also indicate the role of NH3 in new particle formation in Houston under low-sulfur conditions. •Simultaneous measurements of gaseous and aerosol species were conducted.•Atmospheric NH3 contributed to increases in measured particle mass and measured/modeled particle number concentrations.•NH4+ existed in the form of (NH4)2SO4 and NH4HSO4; NH4NO3 and NH4Cl formation was suppressed in summer.