Gas/particle partitioning behaviour of azaarenes in an urban atmosphere.

The gas/particle partitioning of azaarenes in the Liverpool urban atmosphere was measured from May 1995 to April 1996. This period included one of the hottest summers and coldest winters recorded in the UK. The changes of the relative proportions of particulate and vapour phases showed a strong seasonal variation in which over 80% of azaarene compounds are associated with the particles in the winter and over 60% of azaarene compounds exist as vapour phase during the summer. The results are fitted into a gas/particle partitioning equation. Calculated vapour pressures, vaporization and desorption enthalpies are also given. Azaarene partitioning behaviour is modelled at a variety of aerosol concentrations and over a temperature range which includes normal ambient temperatures. It is hypothesised that three ring azaarene species are more likely to undergo changes in the relative proportions of particle and vapour phase material than either two or four ring compounds.