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Indirect measurements of the composition of ultrafine particles in the Arctic late-winter
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  • Deanna Myers,
  • Michael J. Lawler,
  • Roy Mauldin,
  • Steven Sjostedt,
  • Manvendra K Dubey,
  • Jonathan P.D. Abbatt,
  • James Smith
Deanna Myers
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Michael J. Lawler
University of California, Irvine
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Roy Mauldin
University of Colorado Boulder
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Steven Sjostedt
Morgan Community College
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Manvendra K Dubey
Los Alamos National Laboratory (DOE)
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Jonathan P.D. Abbatt
University of Toronto
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James Smith
University of California, Irvine

Corresponding Author:jimsmith@uci.edu

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We present indirect measurements of size-resolved ultrafine particle composition conducted during the Ocean–Atmosphere–Sea Ice–Snowpack (OASIS) Campaign in Utqiagvik, Alaska, during March 2009. This study focuses on measurements of size-resolved particle hygroscopicity and volatility measured over two periods of the campaign. During a period that represents background conditions in this location, particle hygroscopic growth factors (HGF) at 90% relative humidity ranged from 1.45-1.51, which combined with volatility measurements suggest a mixture of ~30% ammoniated sulfates and ~70% oxidized organics. Two separate regional ultrafine particle growth events were also observed during this campaign. Event 1 coincided with elevated levels of H2SO4 and solar radiation. These particles were highly hygroscopic (HGF=2.1 for 35 nm particles), but were almost fully volatilized at 160 °C. The air masses associated with both events originated over the Arctic Ocean. Event 1 was influenced by the upper marine boundary layer, while Event 2 spent more time closer to the surface and over open ocean leads, suggesting marine influence in growth processes. Event 2 particles were slightly less hygroscopic (HGF=1.94 for 35nm and 1.67 for 15nm particles), and similarly volatile. We hypothesize that particles formed during both events contained 60-70% hygroscopic salts by volume, with the balance for Event 1 being sulfates and oxidized organics for Event 2. These observations suggest that primary sea spray may be an important initiator of ultrafine particle formation events in the Arctic late-winter, but a variety of processes may be responsible for condensational growth.
27 Nov 2021Published in Journal of Geophysical Research: Atmospheres volume 126 issue 22. 10.1029/2021JD035428