Chemical characterisation of marine aerosol at Amsterdam Island during the austral summer of 2006–2007

https://doi.org/10.1016/j.jaerosci.2009.08.003Get rights and content

Abstract

Atmospheric aerosols were collected in separate fine (<2.5 μm) and coarse (>2.5 μm) size fractions in the period December 2006–March 2007 at Amsterdam Island in the southern Indian Ocean. A major objective of the study was to assess biogenic impact on the marine aerosol. The samples were analysed for organic carbon, water-soluble organic carbon, major inorganic ionic species, and organic species, including methanesulphonate (MSA), dicarboxylic acids, and organosulphates. The concentrations of sea salt, non-sea-salt sulphate, and water-soluble and water-insoluble organic matter (WSOM and WIOM) were estimated. Sea salt dominated the composition of the aerosol and accounted for 83% and 91% of the sum of the mass of the four aerosol types in the fine and coarse size fractions, respectively. WSOM, which can serve as a proxy for biogenic secondary organic aerosol (SOA), accounted for only 2.8% of the sum of the mass of the four aerosol types in the fine size fraction. MSA was the dominating organic compound with a median concentration of 47 ng m−3. The organosulphates were characterised as sulphate esters of hydroxyl acids and a dihydroxylaldehyde, which may originate from the oxidation of algal/bacterial unsaturated fatty acid residues. No evidence was found for isoprene SOA.

Introduction

A chemical characterisation was carried out of marine aerosols that were collected at Amsterdam Island in the southern Indian Ocean during a period of high biogenic activity. The aim of the study was to examine whether the remote ocean is an important source of secondary organic aerosol (SOA) from biogenic origin that could serve as cloud condensation nuclei (CCN). It is well-known that oceanic areas of high primary productivity emit dimethylsulphide (DMS) (Kettle & Andreae, 2000), which is converted into submicrometer-sized sulphate and methanesulphonate aerosols within the atmosphere, and that these aerosols can affect cloud albedo and climate (Charlson, Lovelock, Andreae, & Warren, 1987). In addition, a comparison of satellite-derived cloud properties and radiation over and near phytoplankton blooms in the Southern Ocean (Meskhidze & Nenes, 2006) found a doubling of cloud droplet concentration over the blooms and a decrease of 15 W m−2 in short-wave radiation flux at the top of the atmosphere, suggesting that CCN production in bloom regions was greatly enhanced. This illustrates the importance of defining precisely the origin of marine CCN.

Several experimental studies have indicated the presence of significant concentrations of organic matter in marine aerosol (Cavalli et al., 2004; Facchini, Rinaldi et al., 2008; Kleefeld, Hoffer, Krivacsy, & Jennings, 2002; Middlebrook, Murphy, & Thompson, 1998; Novakov et al., 1997; O’Dowd et al., 2004). However, little is known about the chemical composition of the marine carbonaceous aerosol (Facchini, Decesari et al., 2008; Gogou, Apostolaki, & Stephanou, 1998; Kawamura & Gagosian, 1990). Primary aerosols are produced by sea spray involving a bubble bursting mechanism, while the mechanisms leading to secondary aerosols are only partially understood to date. With regard to primary components, it has been well documented by electron microscopic studies that marine aerosol particles have a complex composition and contain bacteria, virus-like particles, fragments of marine organisms, and amorphous gel-like material similar to exopolymer secretions of algae and bacteria (Leck & Bigg (2005a), Leck & Bigg (2005b)). Identified SOA components include methanesulphonate (MSA) (e.g., Ayers, Ivey, & Gillett, 1991; Saltzman, Savoie, Zika, & Prospero, 1983), dicarboxylic acids (Gogou et al., 1998; Wang, Kawamura, & Yamazaki, 2006), and dimethyl- and diethylalkylammonium salts (Facchini, Decesari et al., 2008). SOA from the photo-oxidation of isoprene produced by phytoplankton blooms has also been proposed as a potentially important marine SOA source (Meskhidze & Nenes, 2006).

Recent experimental studies on aerosol from forested areas have indicated substantial concentrations of organosulphates formed by sulphation of SOA components from the photo-oxidation of isoprene, monoterpenes and unsaturated fatty acids that contain hydroxyl or keto/aldehyde groups (Gómez-González et al., 2008; Iinuma et al., 2007; Surratt et al. (2007), Surratt et al. (2008)). These studies prompted us to evaluate whether isoprene SOA-related organosulphates, i.e., 2-methyltetrol sulphates, are present in fine marine aerosol from Amsterdam Island. Our rationale for considering the 2-methyltetrol sulphates was that the 2-methyltetrols are markers for the photo-oxidation of isoprene under low-NOx conditions (Surratt et al., 2006), such as found in a pristine marine environment, and that, if formed, they would be converted to sulphates given that fine marine aerosols contain a substantial amount of sulphate. Using liquid chromatography/mass spectrometry techniques based on negative ion electrospray ionisation [LC/(–)ESI-MS] for the sensitive detection of organosulphates, we also aimed at detecting and identifying additional polar marker compounds that are specific to the marine environment and thus to elucidate a larger fraction of the organic aerosol. It is noted in this respect that organic mass spectrometry speciation studies on marine aerosol have so far mainly been performed by resorting to gas chromatography/mass spectrometry with prior derivatisation (e.g., Gogou et al., 1998; Kawamura & Gagosian, 1990; Wang et al., 2006). With this methodology several polar and acid-sensitive analytes such as organosulphates escape detection.

Section snippets

Aerosol sampling and chemical analyses

The aerosol samples were collected at Amsterdam Island (37.48°S, 77.34°E), which is located in the southern Indian Ocean about half-way between the southern edge of Africa and the southern edge of Australia. An open-faced high-volume dichotomous sampler (HVDS) was used to collect samples in two size fractions, fine or PM2.5 [<2.5 μm aerodynamic diameter (AD)] and coarse (>2.5 μm AD) (Solomon, Moyers, & Fletcher, 1983). Double Pallflex quartz fibre filters of 102 mm diameter (pre-fired for 24 h at

Atmospheric concentrations

The idea of the double filters for each size fraction was to assess sampling artifacts for the carbonaceous and organic species (e.g., Turpin, Saxena, & Andrews, 2000). However, the back/front filter ratios were unusually large (means of typically around 0.8) for the sea salt ions, WSOC, MSA, and the dicarboxylic acids (for OC the mean back/front filter ratio was 0.4). It is likely that the aerosol contained a lot of water, that the filters became somewhat wet during the sampling, and that the

Conclusions

Our results indicate that organic aerosol for samples collected at Amsterdam Island during the austral summer of 2006–2007, a period of high biological activity, makes up less than 10% of the mass in both the fine and the coarse size fractions. Our percentage in the fine size fraction is much less than the 65% of OC (sum of WIOC+WSOC) found for submicrometer-sized aerosol during a high biological activity period at the Atlantic Ocean site of Mace Head (O’Dowd et al., 2004). On a mass basis, sea

Acknowledgements

This research was funded by the European Commission (OOMPH project), the Belgian Federal Science Policy Office (BIOSOL project), the Fund for Scientific Research—Flanders (FWO), and the French Polar Institute (AEROTRACE). The Waters UPLC-LCT Premier XT time-of-flight mass spectrometer used for accurate mass measurements was purchased in 2006 with a grant from the US National Science Foundation.

References (38)

  • F. Cavalli et al.

    Advances in identification of organic matter in marine aerosol

    Journal of Geophysical Research

    (2004)
  • R.J. Charlson et al.

    Oceanic phytoplankton, atmospheric sulfur, cloud albedo and climate

    Nature

    (1987)
  • Chi, X., & Maenhaut, W. (2008). Water-soluble organic carbon in PM2.5 at some urban and forested sites in Europe. In...
  • Draxler, R. R., & Rolph, G. D. (2003). HYSPLIT (HYbrid Single-Particle Lagrangian Integrated Trajectory) Model access...
  • U. Ezat et al.

    Size distribution of mineral aerosols at Amsterdam Island and dry deposition rates in the southern Indian Ocean

    Comptes Rendus de l’Academie des Sciences, Serie II

    (1995)
  • M.C. Facchini et al.

    Important source of marine secondary organic aerosol from biogenic amines

    Environmental Science and Technology

    (2008)
  • M.C. Facchini et al.

    Primary submicron marine aerosol dominated by insoluble organic colloids and aggregates

    Geophysical Research Letters

    (2008)
  • Y. Gómez-González et al.

    Characterization of organosulfates from the photooxidation of isoprene and unsaturated fatty acids in ambient aerosol using liquid chromatography/(–)electrospray ionization mass spectrometry

    Journal of Mass Spectrometry

    (2008)
  • M. Gondwe et al.

    Comparison of modeled versus measured MSA:nss SO42- ratios: A global analysis

    Global Biogeochemical Cycles

    (2004)
  • Cited by (91)

    • Detection of organosulfates and nitrooxy-organosulfates in Arctic and Antarctic atmospheric aerosols, using ultra-high resolution FT-ICR mass spectrometry

      2021, Science of the Total Environment
      Citation Excerpt :

      This subgroup of OSs with C>8, DBE<3 and 3<O<7 (for CHOS)/6<O<10 (for CHONS) were detected in several urban field studies (Jiang et al., 2016; Tao et al., 2014; Wang et al., 2017; Wang et al., 2016; Xie et al., 2020; Zhu et al., 2019) and also at several remote ocean locales (Claeys et al., 2010). Claeys et al. (2010) demonstrated that the presence of a homologous series of OSs with hydroxyl fatty acids (C9–C13) in the marine atmosphere is likely associated with marine phytoplankton. They proposed a plausible formation mechanism which entailed the oxidation of hydroxyl aldehydes released by cell membrane lipids, followed by esterification with biogenic sulfuric acid.

    View all citing articles on Scopus
    View full text