AAAR 37th Annual Conference October 14 - October 18, 2019 Oregon Convention Center Portland, Oregon, USA
Abstract View
Temperature Effects on Sulfuric Acid Aerosol Nucleation and Growth: Initial Results from the TANGENT Study
LEE TISZENKEL, Chris Stangl, Justin Krasnomowitz, Qi Ouyang, Michael J. Apsokardu, Murray Johnston, Shanhu Lee, University of Alabama Huntsville
Abstract Number: 507 Working Group: Aerosol Chemistry
Abstract New particle formation (NPF) accounts for much of the aerosol size distribution that is observed in the ambient atmosphere. The NPF process consists of two steps: nucleation and subsequent growth. At present, chemical and physical mechanisms that govern these two processes are not well understood. Here, we report initial results obtained from the TANGENT (Tandem Aerosol Nucleation and Growth Environment Tube) experiments. The TANGENT apparatus enables us to study these two processes independently with a suite of instrumentation that allows for monitoring of particle size distributions from 1 nm to 100 nm both in the temperature-controlled nucleation region as well as at the end of a separate growth region. The present study focuses on the effects of temperature on sulfuric acid nucleation and further growth. Our results show that lower temperatures enhance both the nucleation and growth rate. However, under temperatures below 268 K the effects of temperature on the nucleation rate become less significant and the nucleation rate becomes less dependent on RH, indicating that particle formation takes place via barrierless nucleation at lower temperatures. We also examined the growth of newly formed particles under differing temperature conditions for nucleation and further growth. Our results show that newly nucleated clusters formed at low temperatures can indeed survive evaporation and grow in a warmer environment in the presence of SO2 and ozone. These results also imply that some heterogeneous reactions involving nanoparticles affect nucleation and growth of newly formed particles.