Laboratory investigations on particle formation and early growth

 Intensive research is carried out at TROPOS regarding the formation and the early growth of aerosol particles for close to atmospheric conditions. The experiments are focused on the system H2SO4/H2O. Time scales considered are in the range of up to 100 sec. The aims of the research are:

  • basic understanding of the steps involved in the process of particle formation,
  • important parameters influencing the rate of particle formation in the system H2SO4/H2O (T, RH, amines/ammonia, organic oxidation products),
  • new formation pathways for H2SO4 other than via OH + SO2 (importance of stabilized Criegee Intermediates),
  • qualitative findings for the role of amines/ammonia and (highly oxidized) organic compounds for the early growth of particles.

As a results of this work essential contributions have been achieved in the understanding of the process of H2SO4/H2O particle formation (Berndt et al., Science, 2005; Sipilä et al., 2010; Petäjä et al., 2011), the importance of amines/ammonia for the rate of particle formation (Berndt et al., 2010) and the role of the reaction of stabilized Criegee Intermediates with SO2 (Mauldin et al., 2012).

The following figure shows an example of formed particles from the ozonolysis of a series of olefins in the presence of SO2 (variation of SO2 and consequently of H2SO4 for constant concentrations of O3 and the olefins). The amount of reacted olefin is given in brackets beside the inital clefin concentrations.