Indirect Composition Measurements of Nucleation Mode Particles in Arctic Late Winter

Abstract:

There have been few measurements of atmospheric particle composition during the winter-spring transition in the Arctic, particularly of nucleation mode particles. With climate change rapidly accelerating in polar regions, understanding the processes leading to nanoparticle formation and growth in this region will improve our predictions of climate change impacts. We report indirect measurements of nanoparticle composition made during the Ocean – Atmosphere – Sea Ice – Snowpack (OASIS) Campaign in Utqiagvik (Barrow), Alaska March 7-14, 2008. Particle size distributions measured using a Scanning Mobility Particle Sizer (SMPS) indicated two separate nanoparticle growth events occurred in this period. Particles in these events grew from 8 nm to ~40 nm. Air mass back trajectories performed by HYSPLIT, in addition to wind direction measurements made using sonic anemometers, suggest no local Utqiagvik influence on these events. Indirect composition measurements were made using both hygroscopicity and volatility tandem differential mobility analyzers (HTDMA and VTDMA). High hygroscopic growth factors (1.5-2.0) were measured for the growing particles. These data, combined with chemical ionization mass spectrometry (CIMS) measurements of gas-phase sulfate compounds, suggest sulfate was a major component of these growing particles. Our observations are the first, to our knowledge, to report composition for nucleation mode particles in Utqiagvik.