Research Contracts

New Search

Project at a Glance

Project Status: complete

Title: Dry acid deposition on materials and vegetation: concentrations in ambient air.

Principal Investigator / Author(s): John, Walter

Contractor: Air and Industrial Hygiene Laboratory, California Department of Health Services

Contract Number: A1-160-32

Research Program Area: Atmospheric Processes

Topic Areas: Acid Deposition, Ambient Air Quality Stds


Ambient concentrations of acidic pollutants were measured in West Los Angeles (LA) and at Tanbark Flats. Alternative sampling methods for nitric acid, nitrate particle; and other species were compared. Combined with data for Martinez, San Jose and the Kern River Canyon, the concentrations have systematic ratios. From these the approximate order of deposition fluxes is (decreasing): NOx' SO2' HN03 and H+. The highest nitric acid and particulate strong acid were at Tanbark Flats, a vulnerable area downwind of Los Angeles.

Preliminary aerosol size distributions from a low pressure impactor show NH4 and SO4 with similar submicron size distributions but H+ somewhat smaller. 51% of the nitrate at West LA was greater than 2.5 µm. The nitrate deposition velocity from washing leaves of japonicum was 0.22 cm/s at West LA and about half that on ovalifolium and a surrogate surface.

Evidence indicated that most of the sulfate on external leaf surfaces was due to SO2' with a deposition velocity of 0.27 cm/s. Deposition velocities of SO2 or SO4 were less than 0.1 cm/s at Tanbark Flats. Exploratory measurements were made with a thin iron film detector for H2SO4droplets and a surrogate Nuclepore "leaf" for SO2'.


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

Stay involved, sign up with CARB's Research Email Distribution List