Size Distributed Aerosol Chemistry at Cape Grim during ACE-1

J Cainey, G Ayers (CSIRO Division of Atmospheric Research, PMB No.1, Aspendale, Victoria 3195, Australia; tel +61 3 9239 4564; email: and M Hooper (Centre for Environmental Science, Monash University, Churchill, Victoria 3842, Australia)

During ACE-1 aerosol chemistry at Cape Grim, Tasmania, was determined using a micro-orifice uniform deposition impactor (MOUDI), with 12 stages covering 0.056 to 18 um diameter, with ion chromatographic analyses. The inverted results provide significant insights into the relative importance of sea salt, sulfur and other compounds in the role of condensation nuclei formation. Sea salt components were found to dominate the super-micron size range, with non-sea-salt sulfate and ammonium predominating in the sub-micron size fractions. Gas phase species such as methanesulfonic acid showed a strong relationship with the surface area distribution. The same MOUDI impactor and system has also been used to monitor the aerosol chemistry continuously over a period of 30 months, allowing an assessment of the seasonal variation in the size distributed chemistry, at Cape Grim. The results of this work indicate that sea salt becomes more significant in winter, while the generation of non-sea-salt sulfate and other species relating to the oxidation of dimethylsulfide predominate in the summer. The chemistry of the MOUDI samples obtained during ACE-1, in the austral spring/summer of 1995, show distributions that are intermediate between those of spring and summer. Consistent with the timing of the ACE-1 experiment.