Heterogeneous Uptake of Alkylamines with Dicarboxylic Organic Acids for the Study of Secondary Organic Aerosol (SOA) Formation

Atmospheric aerosols can impact visibility, human health, and climate. In recent studies, it has been concluded that organic acids, in the presence of alkylamines, play a role in the nucleation and growth of atmospheric nanoparticles. However, the mechanisms relating to the nucleation and growth processes are not well understood. We have studied heterogeneous reactions of gas phase alkylamines onto solid dicarboxylic organic acids. The heterogeneous uptake coefficients were measured at several atmospherically relevant temperatures and relative humidities using a low-pressure fast flow reactor coupled to an ion drift chemical ionization mass spectrometer (ID-CIMS). The uptake is time dependent with initial uptake coefficients of the order of 10^-3 decreasing to a steady state value of 10^-4. The implications of our results to atmospheric nanoparticle growth will be discussed.