Temporally delineated sources of major chemical species in high Arctic snow

• Published in: Atmospheric Chemistry and Physics
• Main Authors: K. M. Macdonald, S. Sharma, D. Toom, A. Chivulescu, A. Platt, M. Elsasser, L. Huang, R. Leaitch, N. Chellman, J. R. McConnell, H. Bozem, D. Kunkel, Y. D. Lei, C.-H. Jeong, J. P. D. Abbatt, G. J. Evans
• Format: Article in Journal/Newspaper
• Language: English
• Published: Copernicus Publications 2018
• Subjects: Physics; QC1-999; Chemistry; QD1-999; Arctic; Nunavut; black carbon
• Online Access: https://doi.org/10.5194/acp-18-3485-2018; https://doaj.org/article/088afceacb0542b3818aa950d44d13c7

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 NO 3 − , with a likely Eurasian source and mid-winter peak. The isolation of NO 3 − on a separate factor may reflect its complex atmospheric processing, though the associated source region suggests possibly ...