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Volume 18, issue 5 | Copyright

Special issue: NETCARE (Network on Aerosols and Climate: Addressing Key Uncertainties...

Atmos. Chem. Phys., 18, 3485-3503, 2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Research article 09 Mar 2018

Research article | 09 Mar 2018

Temporally delineated sources of major chemical species in high Arctic snow

Katrina M. Macdonald1, Sangeeta Sharma2, Desiree Toom2, Alina Chivulescu2, Andrew Platt2, Mike Elsasser2, Lin Huang2, Richard Leaitch2, Nathan Chellman3, Joseph R. McConnell3, Heiko Bozem4, Daniel Kunkel4, Ying Duan Lei1, Cheol-Heon Jeong1, Jonathan P. D. Abbatt5, and Greg J. Evans1 Katrina M. Macdonald et al.
  • 1Department of Chemical Engineering and Applied Chemistry, University of Toronto, Toronto, M5S 3E5, Canada
  • 2Climate Research Division, Environment and Climate Change Canada, Toronto, M3H 5T4, Canada
  • 3Desert Research Institute, Reno, 89512, USA
  • 4Institute for Atmospheric Physics, Johannes Gutenberg University Mainz, Becher Weg 21, 55128 Mainz, Germany
  • 5Department of Chemistry, University of Toronto, Toronto, M5S 3H6, Canada

Abstract. Long-range transport of aerosol from lower latitudes to the high Arctic may be a significant contributor to climate forcing in the Arctic. To identify the sources of key contaminants entering the Canadian High Arctic an intensive campaign of snow sampling was completed at Alert, Nunavut, from September 2014 to June 2015. Fresh snow samples collected every few days were analyzed for black carbon, major ions, and metals, and this rich data set provided an opportunity for a temporally refined source apportionment of snow composition via positive matrix factorization (PMF) in conjunction with FLEXPART (FLEXible PARTicle dispersion model) potential emission sensitivity analysis. Seven source factors were identified: sea salt, crustal metals, black carbon, carboxylic acids, nitrate, non-crustal metals, and sulfate. The sea salt and crustal factors showed good agreement with expected composition and primarily northern sources. High loadings of V and Se onto Factor 2, crustal metals, was consistent with expected elemental ratios, implying these metals were not primarily anthropogenic in origin. Factor 3, black carbon, was an acidic factor dominated by black carbon but with some sulfate contribution over the winter-haze season. The lack of K+ associated with this factor, a Eurasian source, and limited known forest fire events coincident with this factor's peak suggested a predominantly anthropogenic combustion source. Factor 4, carboxylic acids, was dominated by formate and acetate with a moderate correlation to available sunlight and an oceanic and North American source. A robust identification of this factor was not possible; however, atmospheric photochemical reactions, ocean microlayer reaction, and biomass burning were explored as potential contributors. Factor 5, nitrate, was an acidic factor dominated by NO3, with a likely Eurasian source and mid-winter peak. The isolation of NO3 on a separate factor may reflect its complex atmospheric processing, though the associated source region suggests possibly anthropogenic precursors. Factor 6, non-crustal metals, showed heightened loadings of Sb, Pb, and As, and correlation with other metals traditionally associated with industrial activities. Similar to Factor 3 and 5, this factor appeared to be largely Eurasian in origin. Factor 7, sulfate, was dominated by SO42− and MS with a fall peak and high acidity. Coincident volcanic activity and northern source regions may suggest a processed SO2 source of this factor.

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Short summary
The sources of key contaminants in Arctic snow may be an important factor in understanding the rapid climate changes observed in the Arctic. Fresh snow samples collected frequently through the winter season were analyzed for major constituents. Temporally refined source apportionment via positive matrix factorization in conjunction with FLEXPART suggested potential source characteristics and locations. The identity of these sources and their relative contribution to key analytes is discussed.
The sources of key contaminants in Arctic snow may be an important factor in understanding the...