Particle nucleation in a forested environment

Atmospheric nucleation is now recognized to be an important source of ambient particles. In this study, ground-based measurements using a tower were used to observe new particle formation in the Morgan Monroe State Forest (MMSF) in Southwestern Indiana in May 2008. Nucleation was observed at MMSF on a number of days through examination of the particle size distributions. Most of these events were nucleation and growth events that are typical of regional nucleation phenomena. The particle size and sulfuric acid concentration data were used to investigate the mechanism for the observed nucleation events. Four of the ten observed nucleation events were clearly the result of activation of pre-existing clusters. The others seem likely to be the result of classical ternary nucleation.