Measurement of nitrous acid in motor vehicle exhaust
- Univ. of California, Berkeley, CA (United States)
- Lawrence Berkeley National Lab., CA (United States)
Nitrous acid (HONO) is an important tropospheric air pollutant. In this study, HONO and NO{sub x} emissions from on-road vehicles were measured at the Caldecott Tunnel during summer 1995. The Caldecott Tunnel is located on a heavily used highway in the San Francisco Bay area. 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 annular denuders; NO{sub x} concentrations were measured using chemiluminescent analyzers. Average HONO concentrations in the tunnel exhaust and background air were 6.9{+-}1.4 and 0.7{+-}0.3 ppb, respectively. The average HONO/NO{sub x} ratio in motor vehicle exhaust was (2.9{+-}0.5)x10{sup -3}. The HONO/NO{sub x} 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/NO{sub x} ratios are typically much larger than the HONO/NO{sub x} ratio measured at the Caldecott Tunnel, which suggests that ambient HONO concentrations are governed mainly by secondary formation. 40 refs., 2 figs., 2 tabs.
- OSTI ID:
- 414974
- Journal Information:
- Environmental Science and Technology, Journal Name: Environmental Science and Technology Journal Issue: 9 Vol. 30; ISSN 0013-936X; ISSN ESTHAG
- Country of Publication:
- United States
- Language:
- English
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