Characteristics of NO2 Pollution in the City of Gothenburg, South-West Sweden—Relation to NO x and O3 Levels, Photochemistry and Monitoring Location
- 98 Downloads
Concentrations of NO2, NO, and O3 from a rooftop monitoring station in Gothenburg, Sweden (2002–2006) were analysed to characterise NO2 pollution. [NO2] was shown to correlate strongly and non-linearly with [NO x ] (NO x = NO + NO2), in line with observations in other cities. The [NO2] to [NO x ] fraction fell initially with increasing [NO x ]. At [NO x ] levels >200 ppb, the decline in [NO2]/[NO x ] with increasing [NO x ] levelled out and [NO2]/[NO x ] converged towards approximately 0.15–0.16, independent of [NO x ]. Data from a traffic route site showed the same pattern. This value of [NO2]/[NO x ] at high [NO x ] can be interpreted as the NO2 fraction of the NO x emissions from vehicle exhaust. Situations with high NO x pollution and minimum [NO2]/[NO x ] were always associated with [O3] close to zero. Plotting [Ox] (Ox = NO2 + O3) vs. [NO x ] provided a strong linear correlation for situations dominated by local pollution ([NO]/[NO2]>1). The slope of the regression, a measure of the primary NO2 fraction in NO x emissions, was 0.13 during the day and 0.14 during the night. With stronger winds, the rooftop monitoring station became more similar, in terms of NO2 pollution, to a city street site and a traffic route site, although [NO2] was almost always higher at the street/traffic route locations. The EU standard for the annual average of [NO2] (40 μg m−3) was exceeded, while the hourly standard (200 μg m−3, not to be exceeded more than 18 times per year by 2010) was not exceeded at any of the sites.
KeywordsGothenburg Nitrogen dioxide Nitrogen monoxide Oxidant Ozone Photochemistry Primary NO2 fraction Urban air pollution
- Brimblecombe, P. (1996). Air composition and chemistry (2nd ed.). Cambridge: Cambridge University Press.Google Scholar
- European Environment Agency. (2007). Air Pollution in Europe 1990–2004. EEA Report 2/2007. ISSN 1725-9177.Google Scholar
- Leighton, P. A. (1961). Photochemistry of air pollution. New York: Academic.Google Scholar