Nitrous acid (HONO) is an important tropospheric air pollutant. Photolysis of HONO produces hydroxyl radicals that promote ozone formation. HONO may also adversely affect human health. Sources of HONO include both direct emission from combustion processes and secondary atmospheric formation from nitrogen oxides (NOx). In this study, HONO and NOx emissions from on-road vehicles were measured at the heavily used Caldecott Tunnel during summer 1995. The mean and median model years of vehicles observed during this study were 1989.3 and 1990, respectively. Nitrous acid was collected on sodium carbonate-coated glass anular denuders; NOx concentrations were measured using chemiluminescent analyzers. The HONO/NOx ratio in vehicle exhaust measured at the Caldecott Tunnel was higher than that reported previously for well-maintained catalyst-equipped vehicles, but was lower than that for older vehicles with limited emission controls. Nighttime ambient HONO/NOx ratios are typically much larger than the HONO/NOx ratio measured at the Caldecott Tunnel, which suggests that ambient HONO concentrations are governed mainly by secondary formation.

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  • Corporate Authors:

    American Chemical Society

    1155 16th Street, NW
    Washington, DC  United States  20036
  • Authors:
    • Kirchstetter, T W
    • HARLEY, R A
  • Publication Date: 1996-9


  • English

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Filing Info

  • Accession Number: 00729330
  • Record Type: Publication
  • Source Agency: Transport Research Laboratory
  • Files: ITRD
  • Created Date: Dec 12 1996 12:00AM