Characteristics of NO2 Pollution in the City of Gothenburg,South-West Sweden-Relation to NO_x and O3 Levels,Photochemistry and Monitoring Location

摘要

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_ emissions from vehicle exhaust.Situations with high NO_x pollution and minimum [NO2]/[NO_x] were always associated with [03] 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 mu g m~(-3))was exceeded,while the hourly standard(200 mu g m~(-3),not to be exceeded more than 18 times per year by 2010)was not exceeded at any of the sites.