  Understanding the aging process of aerosol particles is important for
assessing their chemical reactivity, cloud condensation nuclei activity,
radiative properties and health impacts. In this study we investigate the aging
of black carbon containing particles in an idealized urban plume using a new
approach, the particle-resolved aerosol model PartMC-MOSAIC. We present a
method to estimate aging time-scales using an aging criterion based on cloud
condensation nuclei activation. The results show a separation into a daytime
regime where condensation dominates and a nighttime regime where coagulation
dominates. For the chosen urban plume scenario, depending on the
supersaturation threshold, the values for the aging time-scales vary between
0.06 hours and 10 hours during the day, and between 6 hours and 20 hours during
the night.
