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Project Status: complete

Title: Dry acid deposition: monitoring technique for nitric acid and particulate nitrate-size distributions of acidic particles.

Principal Investigator / Author(s): John, Walter

Contract Number: A5-052-32

Topic Areas: Acid Deposition, Monitoring


Testing in an environmental chamber and in ambient air at Claremont during the Nitrogen Species Methods Comparison Study showed that nitric acid is denuded with high efficiency by the internal surfaces of the Dichotomous sampler. Loss of ammonium nitrate by volatilization was prevented by using a Nylon filter following the usual Teflon membrane filter. The Dichotomous sampler was used at Claremont for 12 hr sampling of the major inorganic ions. Nitric acid concentrations were obtained from the AIHL cyclone-Dichotomous sampler combination, using the difference method. Good agreement was obtained with samplers employing conventional denuders.

Particle size distributions were obtained for the major inorganic ions, using the Berner nine stage cascade impactor. A denuder preceding the impactor removed nitric acid, and fluorocarbon grease on the Tedlar substrates prevented particle bounce. Volatile nitrate loss was shown to be less than ten percent. Fine mode nitrate was associated with ammonium while coarse mode nitrate was associated with both ammonium and sodium. Detailed evidence was obtained for the production of coarse nitrate and hydrochloric acid by the reaction of nitric acid with sea salt. Sulfate was primarily in two submicron modes; hydrogen ion was associated with the smaller mode. Deposition velocities for nitrate and sulfate were measured with Tedlar surfaces and by washing the leaves and needles of potted plants.


For questions regarding this research project, including available data and progress status, contact: Research Division staff at (916) 445-0753

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