Figure 5.

UV-Vis absorption spectra (A) and action spectra of singlet oxygen photogeneration (B) by 0.2 mg/mL of ambient particles: winter (blue circles), spring (green diamonds), summer (red squares), autumn (brown hexagons). Data points are connected with a B-spline for eye guidance. (C) The effect of sodium azide (red lines) on singlet oxygen phosphorescence signals induced by excitation with 360 nm light (black lines). The experiments were repeated 3 times yielding similar results and representative spectra are demonstrated.