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Size-resolved atmospheric particulate polysaccharides in the high summer Arctic
Stockholm University, Faculty of Science, Department of Meteorology .
Stockholm University, Faculty of Science, Department of Meteorology .
Stockholm University, Faculty of Science, Department of Meteorology . Stockholm University, Faculty of Science, Department of Analytical Chemistry.
Stockholm University, Faculty of Science, Department of Analytical Chemistry.
2013 (English)In: Atmospheric Chemistry And Physics, ISSN 1680-7316, E-ISSN 1680-7324, Vol. 13, no 24, p. 12573-12588Article in journal (Refereed) Published
Abstract [en]

Size-resolved aerosol samples for subsequent quantitative determination of polymer sugars (polysaccharides) after hydrolysis to their subunit monomers (monosaccharides) were collected in surface air over the central Arctic Ocean during the biologically most active summer period. The analysis was carried out by novel use of liquid chromatography coupled with highly selective and sensitive tandem mass spectrometry. Polysaccharides were detected in particle sizes ranging from 0.035 to 10 mu m in diameter with distinct features of heteropolysaccharides, enriched in xylose, glucose + mannose as well as a substantial fraction of deoxysugars. Polysaccharides, containing deoxysugar monomers, showed a bimodal size structure with about 70% of their mass found in the Aitken mode over the pack ice area. Pentose (xylose) and hexose (glucose + mannose) had a weaker bimodal character and were largely found with super-micrometer sizes and in addition with a minor sub-micrometer fraction. The concentration of total hydrolysable neutral sugars (THNS) in the samples collected varied over two orders of magnitude (1 to 160 pmol m(-3)) in the supermicrometer size fraction and to a somewhat lesser extent in sub-micrometer particles (4 to 140 pmol m(-3)). Lowest THNS concentrations were observed in air masses that had spent more than five days over the pack ice. Within the pack ice area, about 53% of the mass of hydrolyzed polysaccharides was detected in sub-micrometer particles. The relative abundance of sub-micrometer hydrolyzed polysaccharides could be related to the length of time that the air mass spent over pack ice, with the highest fraction (> 90 %) observed for > 7 days of advection. The aerosol samples collected onboard ship showed similar monosaccharide composition, compared to particles generated experimentally in situ at the expedition's open lead site. This supports the existence of a primary particle source of polysaccharide containing polymer gels from open leads by bubble bursting at the air-sea interface. We speculate that the occurrence of atmospheric surface-active polymer gels with their hydrophilic and hydrophobic segments, promoting cloud droplet activation, could play a potential role as cloud condensation nuclei in the pristine high Arctic.

Place, publisher, year, edition, pages
2013. Vol. 13, no 24, p. 12573-12588
National Category
Meteorology and Atmospheric Sciences
Research subject
Analytical Chemistry
Identifiers
URN: urn:nbn:se:su:diva-100884DOI: 10.5194/acp-13-12573-2013ISI: 000329930000023OAI: oai:DiVA.org:su-100884DiVA, id: diva2:697259
Note

AuthorCount:4;

Available from: 2014-02-17 Created: 2014-02-17 Last updated: 2018-04-27Bibliographically approved
In thesis
1. Analytical methods for biomolecules involved in atmospheric aerosol formation in the Arctic
Open this publication in new window or tab >>Analytical methods for biomolecules involved in atmospheric aerosol formation in the Arctic
2018 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

In the Arctic, increasing ice-free conditions and nutrients freed from the melting ice must strongly influence the marine life. Aerosol emissions from microbiological marine processes may affect the low clouds and fogs over the summer Arctic, which in turn have effects on the melting of sea ice. The radiative properties of the high Arctic low clouds are strongly dependent on the number concentration of airborne water-soluble particles, known as cloud condensation nuclei (CCN). If the effects of CCN on cloud optical properties is to be fully understood it is important to be able to specify the source and concentrations of the Arctic aerosol particles.

Previous studies in the Arctic have indicated that organic material formed in the uppermost ocean surface is transferred to the atmosphere and plays a potentially very important role in the aerosol-fog/cloud cycle. However, many aspects of this process remain unverified and chemical characterisation of targeted groups of biomolecules is still notably fragmentary or non-existing. Investigation of biomolecules, particularly amino acids, peptides and proteins together with mono- and polysac­charides and fatty acids in the airborne aerosol, and their relative contributions to fog/cloud water, requires development of an array of “cutting edge” analytical techniques and methods.

In this thesis, electrospray ionization mass spectrometry was used for all applications and target biomolecules. The measurements in the Arctic turned out to be challenging due to the highly complex, salty matrices, combined with very low concentration and high diversity of the target biomolecules, and each step of the analytical chain needed careful consideration. To increase the detectability of the very low levels of polysaccharides and proteins in aerosols, these compounds were hydrolyzed to their subunits, monosaccharides and amino acids. Monosaccharides were separated using hydrophilic interaction chromatography, which was beneficial for their detection in electrospray ionization mass spectrometry. Amino acids were derivatized, yielding improvement in reversed-phase chromatographic separation, ionization efficiency as well as selectivity. For fatty acids in a sea surface sample, a novel fast screening method was developed, utilizing travelling-wave ion mobility separation as an orthogonal technique connected to mass spectrometry. In addition, a method for the detection of wood burning as an anthropogenic source of aerosols was developed, utilizing anhydrous monosaccharides as markers. This method can be used in the upcoming expeditions for source apportionment studies.

The results from the analyses of the aerosol and fog water samples, collected over the summer pack ice north of 80 °N, show that both total polysaccharides and total proteinaceous compounds (sum of proteins, peptides and amino acids) occurred at the pmol m-3 to nmol m-3 level. Interestingly, the levels were found higher between different years, suggested to be coupled to less ice coverage and thus to a higher biological activity in the ocean surface. The highest concentrations of polysaccharides, as an indication of marine polymer gels, were found during the summer over the pack ice area. In addition, a pilot source apportionment study was carried out combining the measurement of different molecular tracers, used as source markers. This study indicates the seasonality and abundance of marine polymer gels as an important feature of the Arctic Ocean connected to the melting and freezing of sea ice. It should be further studied how the abundance of these gels, which have a high potential for cloud droplet activation, affect the melting and freezing of the perennial sea ice.

Given the successful development of analytical methods for targeted groups of biomolecules, this thesis has supported the importance of biomolecules as CCN and for cloud formation in the Arctic. Less ice coverage may further increase the number of biomolecular CCN which could change the radiative balance, by the formation of more low-level clouds. Overall, more studies are required to further unravel the complex relationship of biogenic sources, atmospheric chemistry and meteorology to assess the impact of climate change on the Arctic.

Place, publisher, year, edition, pages
Stockholm: Department of Environmental Science and Analytical Chemistry, Stockholm University, 2018. p. 76
National Category
Analytical Chemistry Environmental Sciences Meteorology and Atmospheric Sciences
Research subject
Analytical Chemistry
Identifiers
urn:nbn:se:su:diva-155254 (URN)978-91-7797-238-9 (ISBN)978-91-7797-239-6 (ISBN)
Public defence
2018-06-05, Magnélisalen, Kemiska övningslaboratoriet, Svante Arrhenius väg 16 B, Stockholm, 10:00 (English)
Opponent
Supervisors
Note

At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 2: Manuscript. Paper 3: Manuscript. Paper 5: Manuscript.

Available from: 2018-05-07 Created: 2018-04-23 Last updated: 2018-09-10Bibliographically approved

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