Figure 2
![Figure 2](http://media.springernature.com/full/springer-static/image/art%3A10.1186%2F1476-069X-9-73/MediaObjects/12940_2010_Article_372_Fig2_HTML.jpg)
Measured NO 2 concentrations during three sampling campaigns, superimposed on smoothed surface created by kriging. (Cutpoints are quantiles for October 2007 session. The areas within the airport fence line and approximately 200 m away from measured points were masked.)