AAAR 32nd Annual Conference
September 30 - October 4, 2013
Oregon Convention Center
Portland, Oregon, USA
Abstract View
Effect of Pressures and Temperatures on Ion-induced Nucleation Rate Measurement in SO2/H2O/N2 Gas Mixture by Soft X-ray Ionization
TAKASHI OGI, Asep Suhendi, Kikuo Okuyama, Muhammad Miftahul Munir, Ferry Iskandar, Hiroshima University
Abstract Number: 633 Working Group: Aerosols, Clouds, and Climate
Abstract The importance of the role of ions in the production of aerosols in the atmosphere has been discussed for a long time, but the precise mechanism is still not known and more research is required to understand and quantify the effect. Recently, the observation of nucleation and subsequent growth in the real atmosphere has been done in a wide variety of altitude locations corresponding to different pressures, temperatures, and atmospheric conditions. However, recent basic experiments in exploring the role of ion-induced nucleation (IIN) in the production of aerosols have been only conducted under standard temperature and pressure or only in some specific conditions; this is insufficient for understanding the role of IIN in the realistic atmospheric conditions that have variations in pressure and temperature. This study reports the systematic investigation of IIN rate measurement in a SO2/H2O/N2 gas mixture, employing soft X-ray at different pressure and temperature levels. Experiments were conducted using a modified continuous flow gas-generation system, employing a soft X-ray ionizer and a particle counter with an improved integrated online temperature, pressure, and a relative humidity (RH) control system. Nucleation rates were measured as a function of SO2 concentration at different levels of RH, pressure (600–970hPa) and temperature (5–25ºC). The results showed that the nucleation rate dependence on SO2 concentration followed a power law, and the slope varied slightly in a range from 1 to 1.26 at different RH levels (15–60%). A positive pressure effect was generally found and a power law was followed with varied scaling for different SO2 concentrations. The trend of an increase in nucleation rate with temper-ature was consistent with observations in homogenous nucleation experiments, and with the behavior predicted by classical binary nucleation theory. These experimental results will be useful to explain the contribution of IIN in differ-ent locations and atmospheric conditions.