Size distributions and chemical properties of aerosol at Ny Ålesund, Svalbard

Abstract

Physical and chemical parameters of the arctic aerosol were investigated at Ny Ålesund, Svalbard, in March and April 1989 in connection with the third Arctic Gas and Aerosol Project (AGASP III). The number size distribution of the particles was measured over the range of 0.02-1.0 μm. Filter samples were analysed for elemental composition and two integral chemical properties, hygroscopic growth and volatility, were measured. Along with the latter measurements, the distribution of these properties at specific particle sizes, i.e. the degree of internal mixing, was determined.

Both clean, marine conditions and “arctic haze” episodes were included in the series of measurements. The number size distribution indicated that the aerosol was well aged based on its narrowness and the relative low concentration of nuclei mode particles. It had a number mode at 0.22 μm diameter and geometric standard deviation of 1.4. Generally the particles exhibited uniform hygroscopic growth properties, i.e. they were largely internally mixed. The growth factor was 1.45 at 90% relative humidity. Approximately 40% of the overall particulate mass was volatile at a temperature of 50°C. The volatile fraction varied form particle to particle, i.e. the particles were externally mixed with respect to volatility.