Acquisition of regional air quality model validation data for nitrate, sulfate, ammonium ion and their precursors

Abstract

An intensive field study was conducted throughout California's South Coast Air Basin to acquire air quality model validation data for use with aerosol nitrate formation models. Aerosol nitrate, sulfate, ammonium, other major ionic aerosol species, nitric acid gas and ammonia were measured concurrently at ten sites for forty-eight consecutive hours during the period August [30][31] 1982. Ozone, NO and NO were measured at all locations, and PAN was measured at Pasadena an~ Riverside, completing a nitrogen balance on the air masses studied.The product of the meas~red nitric acid and ammon~a concentrations ranged from less than 1 ppbv to greater than 300 ppbv during the experiment, providing a wide range of conditions over which comparisons can be drawn between chemical equilibrium calculations and experimental results. The ionic material in the aerosol phase was chemically more complex than is assumed by present theoretical models for the equilibrium between NH 3 , HNOa and the aerosol phase, and included . .f. f N + ++ ++ + d Cl-. dd . . NH+ s1gn1 1cant amounts o a , a , Mg , K an 1n a 1t1on to 4 , so4 and NO)· Results of the experiment showed that aerosol nitrate levels in excess of 20 ~g m-3 accumulated in near-coastal locations in the morning of August 31, followed by subsequent transport across the air basin. Trajectory analysis showed that the afternoon aerosol nitrate peak observed inland at Rubidoux near Riverside was associated with the same air mass that contained the high morning nitrate levels near the coast, indicating that description of both transport and atmospheric chemical reactions is important in understanding regional nitrate dynamics. + Mechanical Engineering Department and Environmental Quality Laboratory * Environmental Engineering Science Department and EnvironmentalQuality Laboratory IntroductionAmmonia and nitric acid vapor react to form ammonium nitrate aerosol. This is important because ammonium nitrate containing aerosols account for a significant fraction of local and regional visibility problems, particularly in Los Angeles and Denver (White and Roberts, 1977;Cass, 1979;Groblicki et al., 1981 Environmental Protection Agency (1973, 1978 et seq.). PAN was measured by electron capture gas chromatography, and NO and N0 2 were measured by chemiluminescence by researchers at the University of California at Riverside (UCR). PAN also was measured by the same principle at Caltech in Pasadena.The aerosol, nitric acid and ammonia sampling apparatus for this experiment is shown schematically in Figure 2. Aerosol nitrate and nitric acid concentrations were measured both by dual filter methods and by the denuder difference method. Gaseous ammonia was measured by a dual filter method using oxalic acid impregnated filters as a sink for NH 3 • Filter holders were of open-faced design so that any large particle nitrates would be collected. The sampling apparatus was surrounded by a bug screen and shaded by a sun shield to prevent nitrate volatilization through over-heating. Nine of the ten sa...

Real-Time Measurement of Correlated Size and Composition Profiles of Individual Atmospheric Aerosol Particles

“…Based on the total nitrate-containing size distribution in this figure (black distribution), there appear to be two distinct nitrate modes, an observation that is consistent with previous reports (20,58,(60)(61)(62)(63)(64)(65). Most likely, this association occurs when nitric acid and ammonia, typically present in high abundance in the Riverside area, react with fine organic particles (55)(56)(57)(58)(59). In the smallest size range, nitrate is associated with particles containing primarily organic components.…”

Water-soluble organic aerosol in the Los Angeles Basin and outflow regions: Airborne and ground measurements during the 2010 CalNex field campaign

“…Two widely studied areas in the United States with regard to atmospheric aerosol properties and composition include the Los Angeles Basin [ Hidy et al , 1974; Grosjean and Friedlander , 1975; Husar et al , 1976, 1977; Blumenthal et al , 1978; Russell et al , 1983; McElroy and Smith , 1986; Russell and Cass , 1984, 1986; Kawamura and Kaplan , 1987; Wall et al , 1988; Pandis et al , 1992a, 1992b; Zhang et al , 1993; Chow et al , 1994; Hildemann et al , 1994a, 1994b, 1996; Eldering and Cass , 1996; Kleeman et al , 1999; Collins et al , 2000; Hughes et al , 2000; Neuman et al , 2003; Sardar et al , 2005; Vutukuru et al , 2006; Docherty et al , 2008; Hersey et al , 2011] and the San Joaquin Valley of California [ Magliano et al , 1999; Schauer and Cass , 2000; Chow et al , 1992, 1993, 1996, 2006; Neuman et al , 2003; Sorooshian et al , 2008a]. While these studies have provided significant knowledge of regional aerosol characteristics, there remain important uncertainties with regard to organic aerosol composition and properties.…”

An assessment of the ability of three‐dimensional air quality models with current thermodynamic equilibrium models to predict aerosol NO3−

“…Atmospheric fine particles are predominately composed of sulfate, nitrate, ammonium, sodium, chloride, water, organic species and trace metals [ Russell and Cass , 1984; Malm et al , 1994; Environmental Protection Agency ( EPA ), 1996, 1998; Yu et al , 2003]. Fine particles refer to the particles with diameters less than 2.5 μm (PM 2.5 ).…”