Hygroscopic And Volatile Properties of Marine Aerosol Observed at Cape Grim During P2P Campaign

Simultaneous measurement of particle hygroscopic and volatile properties was performed using a VH-TDMA on both Aitken and accumulation mode particles. In addition deliquescence measurements at different thermodenuder temperatures were also performed. The measurements were part of the P2P campaign which took place in February 2006 at Cape Grim monitoring station in Tasmania, Australia. During baseline conditions, there was often a volatilisation step occurring below 125°C in the volatility scans, where up to 25% of the volume is lost. Analysis of the changes in growth as this occurred indicates that different substances are responsible for this volatilisation on different days - ammonium nitrate, sulphuric acid, or a volatile non-hygroscopic organic. The major volatilisation in all cases occurred in the temperature range ~140-200oC, which is taken to indicate the presence of ammonium sulphate or ammonium bisulphate. A degree of growth suppression is generally evident prior to this volatilisation, indicating that a non-hygroscopic material with a similar volatility to ammonium sulphate/bisulphate may be present which cannot be distinguished in the volatility scans. Organic matter was typically present at around 20-40% for these particles. When Aitken and accumulation mode particles were measured on the same day, it was found that the organic content of the smaller particles tended to be higher than the larger particles by roughly 20 percentage points.