Hygroscopicity and chemical composition of Antarctic sub-micrometre aerosol particles and observations of new particle formation 1Finnish Meteorological Institute, Research and Development, P. O. Box 503, 00101 Helsinki, Finland
2Department of Physics, University of Helsinki, P. O. Box 64, 00014 Helsinki, Finland
Received: 08 December 2009 – Published in Atmos. Chem. Phys. Discuss.: 17 December 2009 Abstract. The Antarctic near-coastal sub-micrometre aerosol particle features in summer
were characterised based on measured data on aerosol hygroscopicity, size
distributions, volatility and chemical ion and organic carbon mass
concentrations. Hysplit model was used to calculate the history of the air
masses to predict the particle origin. Additional measurements of
meteorological parameters were utilised. The hygroscopic properties of
particles mostly resembled those of marine aerosols. The measurements took
place at 130 km from the Southern Ocean, which was the most significant
factor affecting the particle properties. This is explained by the lack of
additional sources on the continent of Antarctica. The Southern Ocean was
thus a likely source of the particles and nucleating and condensing vapours.
The particles were very hygroscopic (HGF 1.75 at 90 nm) and very volatile.
Most of the sub-100 nm particle volume volatilised below 100 °C.
Based on chemical data, particle hygroscopic and volatile properties were
explained by a large fraction of non-neutralised sulphuric acid together with
organic material. The hygroscopic growth factors assessed from chemical data
were similar to measured. Hygroscopicity was higher in dry continental air
masses compared with the moist marine air masses. This was explained by the
aging of the marine organic species and lower methanesulphonic acid volume
fraction together with the changes in the inorganic aerosol chemistry as the
aerosol had travelled long time over the continental Antarctica. Special
focus was directed in detailed examination of the observed new particle
formation events. Indications of the preference of negative over positive
ions in nucleation could be detected. However, in a detailed case study, the
neutral particles dominated the particle formation process. Freshly nucleated
particles had the smallest hygroscopic growth factors, which increased
subsequent to particle aging.
Revised: 22 April 2010 – Accepted: 03 May 2010 – Published: 06 May 2010
Citation: Asmi, E., Frey, A., Virkkula, A., Ehn, M., Manninen, H. E., Timonen, H., Tolonen-Kivimäki, O., Aurela, M., Hillamo, R., and Kulmala, M.: Hygroscopicity and chemical composition of Antarctic sub-micrometre aerosol particles and observations of new particle formation, Atmos. Chem. Phys., 10, 4253-4271, doi:10.5194/acp-10-4253-2010, 2010.