Physicochemical properties and origin of organic groups detected in boreal forest using an aerosol mass spectrometer

Abstract

Abstract. An Aerodyne quadrupole aerosol mass spectrometer (Q-AMS) was deployed in Hyytiälä, a forested rural measurement site in southern Finland, during a 2-week measurement campaign in spring 2005. Q-AMS measures mass concentrations of non-refractory species including sulphate, nitrate, ammonium and organics from submicron particles. A positive matrix factorization method was used in identifying two oxygenated organic aerosol (OOA) groups from the measured total organic mass. The properties of these groups were estimated from their diurnal concentration cycles and correlations with additional data such as air mass history, particle number size distributions, hygroscopic and ethanol growth factors and particle volatility. It was found that the aged and highly oxidized background organic aerosol (OOA1 or LV-OOA) species have a wide range of hygroscopic growth factors and volatilization temperatures, but on the average OOA1 is the less volatile and more hygroscopic organic group. Hygroscopic properties and volatilities of the OOA1 species are correlated so that the less volatile species have higher hygroscopic growth factors. The other, less oxidized organic aerosol group (OOA2 or SV-OOA) is more volatile and non-hygroscopic. Trajectory analysis showed that OOA1 and the inorganic species are mainly long-range transported anthropogenic pollutions. OOA2 species and its precursor gases have short atmospheric life times, so they are from local sources. These results span the range of previous observations of oxygen content, volatility and hygroscopic growth factor, simultaneously coupling all three measurements for the first time.

The hygroscopicity parameter (κ) of ambient organic aerosol at a field site subject to biogenic and anthropogenic influences: relationship to degree of aerosol oxidation

“…Here we conduct a study of the hygroscopicity of the organic component at supersaturated conditions, focusing on the oxygenated component under the assumption that the unoxygenated component is non-hygroscopic. Similar results have been published for subsaturated conditions (McFiggans et al, 2005;Raatikainen et al, 2010) and more recently for laboratory and ambient measurements ), although laboratory experiments have shown that organic aerosol hygroscopicity under subsaturated conditions can be lower than under supersaturated conditions (Petters et al, 2009b;Prenni et al, 2007;Wex et al, 2009). This study builds on the results from previous closure studies conducted in our group at urban and rural sites (Broekhuizen et al, 2006;Chang et al, 2007).…”

Identification and quantification of particle growth channels during new particle formation

“…The presence of fresh SOA in these particles is not surprising since the fast particle growth rate leaves little time for oxidative aging. The high contribution of carbonaceous matter to aerosol growth is consistent with previous measurements of aerosol composition with AMS in Hyytiälä (Allan et al, 2006;Raatikainen et al, 2010). Figure 3b shows particle compositions scaled to total growth rate for each of these events.…”

Seasonal variation of CCN concentrations and aerosol activation properties in boreal forest

“…As shown by Raatikainen et al (2010), the organic aerosol in Hyytiälä in spring/summer can be thought of as a mix of two oxidized organic aerosol constituents. Jimenez et al (2009) converted the estimated growth factors of the two constituents to κ values of 0.2 and 0.0, respectively.…”