Secondary aerosol sulfate

The cosmogenic radionuclides, particularly Be-7, are associated with slightly smaller aerosols than sulfate, both in winter and summer. The reasons for this difference may be either (1) faster growth rates of secondary aerosols in plumes... 

FIGURE 3-5 Hourly variatioiis of secondary aerosol organics, nitrates, sulfates, and ammonium as percent of total aerosol. Pasadena, Califixnia, July 25, 1973. Reprinted with permis from Grosjean and Friedlandn. ... 

Chemical radicals—such as hydroxyl, peroxyhydroxyl, and various alkyl and aryl species—have either been observed in laboratory studies or have been postulated as photochemical reaction intermediates. Atmospheric photochemical reactions also result in the formation of finely divided suspended particles (secondary aerosols), which create atmospheric haze. Their chemical content is enriched with sulfates (from sulfur dioxide), nitrates (from nitrogen dioxide, nitric oxide, and peroxyacylnitrates), ammonium (from ammonia), chloride (from sea salt), water, and oxygenated, sulfiirated, and nitrated organic compounds (from chemical combination of ozone and oxygen with hydrocarbon, sulfur oxide, and nitrogen oxide fragments). ... 

The source contributions of aerosol formed from gaseous emissions, such as sulfate, nitrate and certain organic species, cannot be quantified by chemical mass balance methods, Watson (9>) proposes a unique source type which will put an upper limit on the contributions of secondary aerosol sources, but it cannot attribute those contributions to specific emitters. 

Water is a major component of the accumulation mode aerosol in amounts that depend on the relative humidity. The uptake of water is driven by the strongly hygroscopic nature of the secondary aerosol components, especially the ainmoniuin sulfates and nitrate. The water content depends in a complex way on both the inorganic and organic components. The resulting aerosol phase solutions are likely to be highly concentrated compared with fog droplets, for example. 

Formation of combustion particles also involves nucleation and condensation of vapors, although the processes occur at elevated temperatures inside the combustion source and during cooling of the plume. Like secondary aerosols, combustion particles have a major semivolatile component composed of sulfates from sulfur dioxide oxidation and organic oxidation products, and of unburned fuel and oil as well. Furthermore, they contain a large non-volatile component consisting of soot, metals, and metal oxides. 

The sources and chemical compositions of the fine and coarse urban particles are different. Coarse particles are generated by mechanical processes and consist of soil dust, seasalt, fly ash, tire wear particles, and so on. Aitken and accumulation mode particles contain primary particles from combustion sources and secondary aerosol material (sulfate, nitrate, ammonium, secondary organics) formed by chemical reactions resulting in gas-to-particle conversion (see Chapters 10 and 14). 

CMB Application to Central California PM Chow et al. (1992) apportioned source contributions to aerosol concentrations in the San Joaquin Valley of California. The source profiles used for CMB application are shown in Table 26.1. The standard deviations oa.. of the profiles (three or more samples were taken) are also included. To account for secondary aerosol components in the CMB calculations, ammonium sulfate, ammonium nitrate, sodium nitrate, and organic carbon were expressed as secondary source profiles using the stoichiometry of each compound. The average elemental concentrations observed at one of the receptors—Fresno, California, in 1988-1989— are shown in Table 26.2. The ambient concentrations of some species (c.g., Ga, As, Y, Mo, Ag) included in the source profiles were below the detection limits. These species... 

Soil-derived partieles sueh as aluminosilicates, CaCOs, and Si02 are the seeond most abundant partiele type in indoor environment of subway stations. The relative abundanee of the sod-derived particles in subway stations are the lowest in the tunnel and the highest at the waiting room. Also secondary particles sueh as nitrates and sulfates are more abundantly encountered in the waiting room than in the platform area. The soil-derived and secondary aerosol particles are likely from the outdoor atmosphere. Therefore, the contents of those particles are higher for the samples eoUeeted at the loeations closer to the outdoor. 

Aerosols that are created in the atmosphere, by nucleation and growth from chemicals in the atmosphere, are termed seco / ry aerosols. An example of a secondary aerosol is the dispersed particulate matter that forms in the atmosphere due to free-radical polymerization of automobile exhaust gases [119]. Another example is the sulfates produced in the atmosphere from the SO2 gas released by industrial plants. These sulfate particles reflect sunlight and also serve as nuclei for cloud formation (see Section 9.7.1). 

Review of the literature provides ample evidence that aerosol formation is an important part of the atmospheric chemistry linked with photochemical-oxidant production. The important chemical constituents of concern include sulfate, nitrate, and secondary organic material. 

Results For the St. Louis data, the target transformation analysis results for the fine fraction without July Uth and 5th are given in table 6. The presence of a motor vehicle source, a sulfur source, a soil or flyash source, a titanium source, and a zinc source are indicated. The sulfur, titanium and zinc factors were determined from the simple initial test vectors for those elements. The concentration of sulfur was not related to any other elements and represents a secondary sulfate aerosol resulting from the conversion of primary sulfur oxide emissions. Titanium was found to be associated with sulfur, calcium, iron, and barium. Rheingrover ( jt) identified the source of titanium as a paint-pigment factory located to the south of station 112. The zinc factor, associated with the elements chlorine, potassium, iron and lead, is attributed to refuse incinerator emissions. This factor could also represent particles from zinc and/or lead smelters, though a high chlorine concentration is usually associated with particles from refuse incinerators ( ). The sulfur concentration in the refined sulfate factor is consistent with that of ammonium sulfate. The calculated lead concentration in the motor vehicle factor of ten percent and a lead to bromine ratio of about 0.28 are typical of values reported in the literature (25). The concentration of lead in... 

We have also looked for the presence of increased secondary organic aerosol by calculating the fine aerosol mass balance in both summer and winter during periods of high and low sulfate concentrations. Formation of secondary sulfate aerosol can cause elevated levels of sulfates and has been linked to periods of regional scale haziness in the eastern U.S. (17). 

Our rationale for this analysis procedure is that during periods of increased concentration of secondary sulfate aerosol there might also be an increase in secondary carbon aerosol. The frequency distribution for all samples is shown in Figure 7a. 

Secondary pollutants H2S04, sulfate aerosols, etc. 03, PAN, HNO, aldehydes, particulate nitrate and sulfate, etc. 

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