Influence of mixing layer height on air pollutant concentrations in an urban street canyon

It is found that even in the immediate vicinity (kerbside) to a busy road the concentrations of air pollutants are strongly affected by MLH. It is a new result that high quantiles of concentrations decrease stronger with increasing MLH than low quantiles. The strongest correlations between concentrations and MLH are obtained for maximum concentrations with coefficients r from −0.84 to −0.95. In general, maximum concentrations of air pollutants in a street canyon provide stronger correlations with MLH than mean concentrations. NO2 is the pollutant whose concentration is affected least by MLH because it is mainly a secondary pollutant.