Hygroscopicity and chemical composition of Antarctic sub-micrometre aerosol particles and observations of new particle formation

Abstract

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 wasCorrespondence to: E. Asmi (eija.asmi@fmi.fi) 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.

Seasonal variations and vertical features of aerosol particles in the Antarctic troposphere

“…The estimated time for particle growth was comparable with the growth rate in new particle formation (0.1-3 nm h −1 ) for the Antarctic coast (Koponen et al, 2003;Kulmala et al, 2004;Virkkula et al, 2007). When organic vapours contribute significantly to particle growth, as suggested by Meskhidze and Nenes (2006) and Asmi et al (2010), the time for particle growth can be shorter relative to results in Fig. 7.…”

“…Previous aerosol measurements taken during the summer at the Antarctic coast showed that the important condensable vapours are H 2 SO 4 and methanesulfonic acid (MSA) derived from oceanic bioactivity (Eisele and Tanner, 1993;Jefferson et al, 1998a, b;Eisele et al, 2008). Furthermore, recent works have shown that organic vapours can act as condensable vapours even in Antarctic troposphere (Meskhidze and Nenes, 2006;Asmi et al, 2010). In the present study, however, only H 2 SO 4 and MSA are considered as "condensable vapours" because of a lack of knowledge (e.g., concentrations and compounds) about organic vapours in the Antarctic troposphere.…”

Unexpectedly high ultrafine aerosol concentrations above East Antarctic sea ice

“…In contrast, coastal measurements obtained between 1991 to 2009 at Neumayer Station (Weller et al, 2011, a coastal location) showed that daily average CN 3 concentrations exhibited a seasonal cycle with a July minimum (at around 100 cm −3 ), an October peak of 350 cm −3 followed by an annual maximum in March of around 800 cm −3 . Measurements at Aboa (Asmi et al, 2010;Koponen et al, 2003, coastal) showed January monthly averages that ranged between 370 and 640 cm −3 , depending on the year. At South Pole (Park et al, 2004, continental), number concentrations in December ranged from 100 to 300 cm −3 .…”

“…Numerous studies have previously observed enhanced aerosol number concentrations in the AFT (e.g. Ito et al, 1986;Osada et al, 2006;Hara et al, 2011b), and even more have suggested it as the dominant source region of Antarctic aerosol (Ito, 1989(Ito, , 1993(Ito, , 1995Virkkula et al, 2009;Asmi et al, 2010;Järvinen et al, 2013;Koponen et al, 2003). We speculate that the absence of signs of growth in the data presented in this study could be a result of condensational growth halting, possibly due to exhaustion of the precursor source, prior to reaching the measurement location.…”

New particle formation and ultrafine charged aerosol climatology at a high altitude site in the Alps (Jungfraujoch, 3580 m a.s.l., Switzerland)

“…New particle formation events have been observed in various environments (see Kulmala et al, 2004, for a review) from polluted area (Hämeri et al, 1996;Harrison et al, 2000;Woo et al, 2001;Stanier et al, 2004;Dunn et al, 2004) to clean or rural sites (Weber et al, 1997;Mäkelä et al, 1997;O'Dowd et al, 1998;Suni et al, 2008), polar areas (Weber et al, 2003;Asmi et al, 2010) and high altitude sites (Weber et al, 1995;Venzac et al, 2007;Shaw, 2007;Nishita et al, 2008;Rodriguez et al, 2009). It has been recently proposed that nucleation was promoted at high altitude .…”