Ambient sulfate aerosols are composed of sulfuric acid, ammonium sulfate, or other sulfate salt mixtures, and the term "total sulfate" includes these substances of diverse chemical and physical properties. Measurements of total sulfate are often made, but without measurements of the associated cations they are inadequate to assess the contribution of aerosols to acid rain, damage to surfaces, heterogeneous oxidation of SO(,2), and human health effects. In this study the chemical properties of sulfate aerosols were investigated in the northeastern U.S. by measurements of acidity, ionic composition, and particle morphology over a range of conditions. / Aerosols were collected from an aircraft during three field programs: spring and fall 1979 and summer 1980. Strong and weak aerosol acidity was determined by extraction of filters and Gran titrations, and for 30 samples the weak acidity comprised x (+OR-) s = 26 (+OR-) 12% of the total acidity. The strong acid and ammonium concentrations were found to balance the sulfate with the ratio of equivalents ({H('+)} + {NH(,4)('+)})/{SO(,4)('=)} = 1.03 (+OR-) 0.14 for 36 samples. The strong acidity averaged 25 (+OR-) 18% of the total sulfate. A phase diagram was used to show that the aerosols were often liquid at ambient humidity, and for 24 liquid samples the calculated pH was 0.11 (+OR-) 0.59. / Inspecting particles by electron microscopy showed that under most conditions accumulation mode aerosols collected in the boundary layer were composed of sulfate particles which were internally mixed, indicating that individual particle composition could be inferred from bulk measurements. Evidence for oxidation of SO(,2) to H(,2)SO(,4) in cloud droplets was obtained in samples collected near clouds, representing a potentially major pathway for SO(,2) oxidation in the lower troposphere. / Elemental size distributions determined by cascade impactors and x-ray analysis showed distinct seasonal differences. While sulfate concentrations averaged 16.7 (+OR-) 9.9 (mu)g/m('3) in summer and 6.68 (+OR-) 3.27 in fall, chlorine concentrations were much higher in fall suggesting loss of HCl from the more acidic summertime aerosols. The sulfur size distributions showed that summer particles contained twice the mass per particle as those during fall, indicating a possible enhancement of sulfate in aerosol droplets by a liquid-phase SO(,2) oxidation mechanism. / Source: Dissertation Abstracts International, Volume: 43-01, Section: B, page: 0081. / Thesis (Ph.D.)--The Florida State University, 1982.
| Identifer | oai:union.ndltd.org:fsu.edu/oai:fsu.digital.flvc.org:fsu_74727 |
| Contributors | FEREK, RONALD JOHN., Florida State University |
| Source Sets | Florida State University |
| Detected Language | English |
| Type | Text |
| Format | 164 p. |
| Rights | On campus use only. |
| Relation | Dissertation Abstracts International |
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