Project at a Glance
Project Status: complete
Title: Southern California air quality study-fall study
Principal Investigator / Author(s): Appel, Bruce R
Contractor: Air and Industrial Hygiene Laboratory, California Department of Health Services
Contract Number: A732-089
Research Program Area: Atmospheric Processes
A field study was performed as part of the Air Resources Board-sponsored Southern California Air Quality Study (SCAQS). Sampling was done at Long Beach Community College for six, 24-hr periods from within the interval November 11 to December 12, 1987. Sampling focussed on the measurement of nitrogen oxides and ammonia. Nitrous and nitric acid, as well as hydcrochloric acid, were sampled with carbonate-glycerol-coated annular denuders. Nitrogen dioxide was measured with a chemiluminescent NOx analyzer which sampled half the time through carbonate-glycerol coated open tubes intended to remove the interferents, HONO and HNO3. Ammonia was sampled with citric acid-glycerine-coated annular denuders, and analyzed on site to minimize error. The sampler design ensured that NH3 loss ahead of the collection surface was minimized. Other pollutants measured, to assist in data analysis, included NO and O3, relative humidity and temperature.
Nitrogen dioxide measured with the denuded chemiluminescent analyzer averaged about 13% lower than without the denuder. Nitrogen dioxide, itself, was shown to have nearly quantitative transmission efficiency through the denuder. The concentration of the interferent removed by the denuder showed positive correlation with the sum of HONO and HNO3. Nitrous acid concentrations exhibited diurnal maxima between midnight and 0600 hours, with 6-hr mean concentrations up to 14 ppb. However, unexpectedly high daytime HONO concentrations of 3 or 4 ppb were oftern observed, suggesting that artifactual HONO (e.g. that possibly formed within the inlet ) may contribute to the measured values. Nitric acid showed diurnal maxima during the 1000 - 1400 hours sampling period, with levels up to 16Ķg/m3 (6 ppb). The concentration of HCl also exhibited a consistent diurnal maximum between 1000 and - 1400 hours, with concentrations up to 15ppb. Thus, HCl may be a relatively important source of acidification, by wet and dry deposition, near the western edge of the South Coast Air Basin.
Ammonia concentrations exhibited maxima during night or morning hours, with four or six hour average concentrations up to 15ppb. Comparison of the ammonia results with those from the SCAQS sampler suggests a substantial degree of NH3 loss within the latter sampler.
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