Investigations of emissions and heterogeneous formation of HONO in a road traffic tunnel

• Published in: Atmospheric environment (1994) Vol. 35; no. 20; pp. 3385 - 3394
• Main Authors: Kurtenbach, R., Becker, K.H., Gomes, J.A.G., Kleffmann, J., Lörzer, J.C., Spittler, M., Wiesen, P., Ackermann, R., Geyer, A., Platt, U.
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 01.07.2001; Elsevier Science
• Subjects: Applied sciences; Atmospheric pollution; Emission indices; Emission ratios; Exact sciences and technology; Germany, Wuppertal; Heterogeneous reactions; Nitrous acid; Pollution; Pollution sources. Measurement results; Road traffic emissions; Road traffic tunnel; Transports; Europe; Germany; Heterogeneous reactions; Emission indices; Emission ratios; Road traffic tunnel; Nitrous acid; Road traffic emissions; Pollutant formation; Emission content; Motor vehicle; Diurnal variation; Pollutant emission; Time variation; Road tunnel; Air pollution; Road traffic; Mixing ratio; Formation mechanism; Heterogeneous reaction
• DOI: 10.1016/S1352-2310(01)00138-8
• ISSN: 1352-2310

Simultaneous measurements of nitrous acid (HONO) and nitrogen dioxide (NO 2) using a differential optical absorption spectroscopy system, nitrogen oxide (NO) by an in situ chemiluminescence analyser and carbon dioxide (CO 2) by a gas chromatographic technique were carried out in the Wuppertal Kiesbergtunnel. At high traffic density HONO concentrations of up to 45 ppbV were observed. However, at low traffic density unexpectedly high HONO concentrations of up to 10 ppbV were measured caused by heterogeneous HONO formation on the tunnel walls. In addition to the tunnel campaigns, emission measurements of HONO, NO 2, NO and CO 2 from different single vehicles (a truck, a diesel and a gasoline passenger car) were also performed. For the correction of the HONO emission data, the heterogeneous HONO formation on the tunnel walls was quantified by two different approaches (a) in different NO 2 emission experiments in the tunnel without traffic and (b) on tunnel wall residue in the laboratory. The HONO concentration corrected for heterogeneous formation on the tunnel walls, in relation to the CO 2 concentration can be used to estimate the amount of HONO, which is directly emitted from the vehicle fleet. From the measured data, emission ratios (e.g. HONO/NO x ) and emission indices (e.g. mg HONO kg −1 fuel) were calculated. The calculated emission index of 88±18 mg HONO kg −1 fuel allows an estimation of the HONO emission rates from traffic into the atmosphere. Furthermore, the heterogeneous formation of HONO from NO 2 on freshly emitted exhaust particles is discussed.