Application of the VH-TDMA Technique to Coastal Ambient Aerosols

A newly developed VH-TDMA has been used for the first time to measure the volatile fractions and post volatilization hygroscopic growth factors of ambient aerosols in the coastal marine and urban environments. The results are compared with comparable data for laboratory generated aerosols of known composition. Measurements conducted on coastal Aitken mode particles showed volatilization behavior similar to laboratory generated aerosols composed of methane sulfonic acid and ammonium sulfate. Measurements conducted on 60 nm particles during nucleation events contained a greater fraction of material with similar volatility to ammonium sulfate than was found at other times. These particles were hygroscopic but less so than pure ammonium sulfate. Measurements conducted in the Brisbane central business district during sea breeze conditions show similar behavior to the coastal aerosol, but with additional low volatility species. This aerosol may originate from urban sources or from marine particles acquiring additional secondary aerosol species during transport. I. Introduction Measurement of thermal volatilization temperatures can reveal the presence of lower volatility species within aerosol particles (Clarke, 1993; Orsini et al., 1996; Sakurai et al., 2003; Schmid et al., 2002). By measuring the hygroscopic behavior of the aerosol after volatilization the solubility of these low volatility residues can also be examined. A volatilization and humidification tandem differential mobility analyzer VH-TDMA system was recently developed for this purpose and the design of this system as well as it’s performance with respect to a variety of laboratory generated aerosols representing species thought to exist in coastal marine ambient aerosols has been previously described (Johnson et al., 2004). The current work demonstrates the application of this system in examining ambient aerosols including those found in coastal marine and urban environments