Research Projects

Project at a Glance

Project Status: complete

Title: Assessment of dry acid deposition in California. Final report.

Principal Investigator / Author(s): John, Walter

Contractor: California Department of Health Services

Contract Number: A1-053-32


Research Program Area: Atmospheric Processes

Topic Areas: Acid Deposition


Abstract:

The ambient concentration deposition velocity method was selected for the development of monitoring techniques for dry acid deposition. Filter sampling trains containing cyclones, gaseous denuders and multiple filters, some chemically impregnated, were used to sample particulate strong acid, sulfate, ammonium, nitrate, nitric acid and ammonia. Hydrogen peroxide bubblers sampled sulfur dioxide. Oxides of nitrogen and meteorological variables were monitored in a mobile laboratory. Chemical analyses included acid titration, ion chromatography and ion-selective electrode.

Sampling was conducted in Martinez (high ammonia), San Jose (high oxides of nitrogen) and the Kern River canyon (high sulfur dioxide). At all three sites, concentrations of acidic species decreased in the order, oxides of nitrogen, sulfur dioxide, nitric acid and particulate strong acid. Especially in Kern Canyon, near-zero nighttime levels of nitric acid and sulfur dioxide indicate more efficient deposition mechanisms than for fine particles. Ion balances were obtained, showing that all major acidic and basic particulate species were sampled and that the samplers performed quantitatively. Some of the present techniques could be applied to monitoring but the full array is impractical. Calculation of reliable deposition fluxes from the ambient concentrations will require improvement in the knowledge of deposition velocities.


 

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