Figure 4.

Atmospheric dust, PAHs, NO₂ and 1-NP concentrations in Beijing in March 2010. (a) Size-fractionated particle-bound 1-NP. (b) Gaseous NO₂ and size-fractionated particle-bound PAHs. (c) Aeolian dust. Variation in concentration of 1-NP relative to that of benzo[k]fluoranthene (BkF) (1-NP/BkF) is also shown in (c). Variation in concentration of 1-NP relative to that of a fairly unreactive and non-volatile PAH, BkF (1-NP/BkF) is also shown in (c). Arrows indicate a heavy dust period [130]. Arrows indicate a heavy dust period. 1-NP, 1-nitropyrene; BkF, benzo[k]fluoranthene; NO_2, nitrogen dioxide; PAH, polycyclic aromatic hydrocarbons