Biogenic Secondary Organic Aerosol Formation Michael Boy ASP / ACD / NCAR

What is the main process concerning SOA formation ? Nucleation ! Condensational growth ! We suggest that the growth of clusters to a detectable sice is restricted by the availability of condensable vapour. Observations of atmospheric particle formation and growth from a continental and a coastal site support this hypothesis, including that a growth process including ternary nucleation is likely to be responsible for the formation of CCN. Kulmala et al., Nature 2000

M. Kulmala et at., Aerosol Science 35 (2004), p Where do we observe SOA formation ?

How many SOA formation events per year ?

Seasonal trend of SOA formation events ? M. Kulmala et at., Aerosol Science 35 (2004), p Rural area in Finland Rural area in Germany Urban area in USA

Is SOA formation a local effect ? (Stratmann et al., ACP 2003, Vol. 3)

(Stratmann et al., ACP 2003) Vertical distribution of new formed particles

How fast do the new formed particles grow ? Kulmala et at., Aerosol Science 2004, Vol. 35 Polar regions: 0.1 nm h -1 Coastal areas: 200 nm h -1

How many particles are produced per time ? Urban areas: up to 100 # cm -3 s -1 Coastal zones: up to # cm -3 s -1 Industrial plumes: up to # cm -3 s -1

________________________________________________________________________________________ University of Helsinki 3 nm Free troposphere Mixed layer 1 nm Formation of TSCs Binary nucleation: H2SO4 + H2O Ternary nucleation: H2SO4 + NH3 + H2O Ion induced nucleation Nucleation of organics

________________________________________________________________________________________ University of Helsinki 3 nm Free troposphere Mixed layer Production of condensable vapours Ozone 1 nm Formation of TSCs Production of condensable vapours Sulphuric acid Monotepenes reaction products Sesquiterpenes reaction products ????

________________________________________________________________________________________ University of Helsinki 3 nm Free troposphere Condensation Coagulation Deposition Mixed layer Production of condensable vapours Ozone Condensation & Coagulation 1 nm Formation of TSCs

Weber et al., JGR (1997) 102 Fiedler et al., ACPD (2005) Sulfuric acid and nucleation mode particles ?

Date Growth rateGR(H 2 SO 4 ) DMPSH 2 SO 4 / GR(DMPS) [nm h -1 ] [%] ,00,066, ,50,1510, ,60,249, ,50,156, ,60,318, ,60,174, ,50,236, ,40,4016, ,80,287, ,80,168, ,90,3913,5 Average2,70,28,9

Intermedia step for global models Influence on CCN UHMA (University of Helsinki Multicomponent Aerosol code) Chemistry subroutine (67 species) BLMARC (1-dimensionsal model) Emission scheme for different biospheres Extended organic chemistry scheme Condensation of organics Information on the secrets of SOA formation Ion induced nucleation

1-D-Model trajectory Thanks !!!