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Measurement of aerosol size distributions for nitrate and major ionic species

1988; Elsevier BV; Volume: 22; Issue: 8 Linguagem: Inglês

10.1016/0004-6981(88)90392-7

1878-2442

Stephen Wall, Walter John, J.L. Ondo,

Atmospheric Ozone and Climate

Nitrate particle size distributions were determined at the Nitrogen Species Methods Comparison Study at Claremont, CA during September 1985 with the Berner nine stage cascade impactor. Particle bounce was minimized by an inert fluorocarbon grease substrate. Interference from nitric acid was eliminated with a vertical acid gas denuder designed to prevent large particle loss. Samples were taken with and without the grease or denuder to test the techniques. Volatile nitrate loss was less than 10%, based on comparisons with fine nitrate from parallel filter samplers. Aerosol size distributions for the major ionic species were determined under varying atmospheric conditions and good ion balances achieved. Nitrate was bimodal during both day and night-time periods. Fine mode nitrate was associated with ammonium while coarse mode nitrate was associated with both ammonium and sodium. Extensive evidence including size distributions, temporal associations and species balances is given for the reaction of nitric acid and sea salt to produce hydrochloric acid and coarse mode nitrate. Sulfate was primarily in two submicrometer modes. Strong acid was associated with the smaller sulfate mode.