title: Connection of sulfuric acid to atmospheric nucleation in boreal forest.
abstract: Gas to particle conversion in the boundary layer occurs worldwide. Sulfuric acid is considered to be one of the key components in these new particle formation events. In this study we explore the connection between measured sulfuric acid and observed formation rate of both charged 2 nm as well as neutral clusters in a boreal forest environment A very short time delay of the order of ten minutes between these two parameters was detected. On average the event days were clearly associated with higher sulfuric acid concentrations and lower condensation sink (CS) values than the nonevent days. Although there was not a clear sharp boundary between the nucleation and no-nucleation days in sulfuric acid-CS plane, at our measurement site a typical threshold concentration of 3.10(5) molecules cm(-3) of sulfuric acid was needed to initiate the new particle formation. Two proposed nucleation mechanisms were tested. Our results are somewhat more in favor of activation type nucleation than of kinetic type nucleation, even though our data set is too limited to omit either of these two mechanisms. In line with earlier studies, the atmospheric nucleation seems to start from sizes very close to 2 nm.
authors: Department of Physics, University of Helsinki, P.O. Box 64, 00014 Helsinki, Finland.
authors: T
authors: T
authors: Nieminen
authors: H E
authors: HE
authors: Manninen
authors: S L
authors: SL
authors: Sihto
authors: T
authors: T
authors: Yli-Juuti
authors: R L
authors: RL
authors: Mauldin
authors: T
authors: T
authors: Petäjä
authors: I
authors: I
authors: Riipinen
authors: V M
authors: VM
authors: Kerminen
authors: M
authors: M
authors: Kulmala
mesh_terms: D000393:Air Pollutants / Q000032:analysis; D000397:Air Pollution / Q000032:analysis; D001272:Atmosphere; D004784:Environmental Monitoring / Q000379:methods*; D004785:Environmental Pollutants; D005387:Finland; D007477:Ions; D007700:Kinetics; D010316:Particle Size; D013464:Sulfuric Acids / Q000032:analysis* / Q000737:chemistry; D014197:Trees
chemical_list: D000393:Air Pollutants; D004785:Environmental Pollutants; D007477:Ions; D013464:Sulfuric Acids; C033158:sulfuric acid