AAAR 37th Annual Conference October 14 - October 18, 2019 Oregon Convention Center Portland, Oregon, USA
Abstract View
Chemical Composition of Individual Particles at a High-Altitude Mountain Station
KUO-PIN TSENG, Tyler Capek, Noopur Sharma, Angela Marinoni, Douglas Orsini, Claudio Mazzoleni, Swarup China, Pacific Northwest National Laboratory
Abstract Number: 639 Working Group: Remote and Regional Atmospheric Aerosol
Abstract The physicochemical properties of atmospheric particles play a critical role in cloud formation and their effects on climate. However, boundary layer and free tropospheric particles are different, and we have especially limited understanding of the physicochemical properties of free tropospheric aerosol. In this study, aerosol samples were collected from a high-altitude mountain site at Mt. Cimone, Italy, in July 2017. The site is representative of Southern Europe – Mediterranean background, but can also be affected by the plume from the Polluted Po Valley. The morphology and elemental composition of individual particles were analyzed via computer-controlled scanning electron microscopy and energy-dispersive X-ray spectroscopy. We also utilized other X-ray microspectroscopy to investigate the chemical bonding of individual particles. The results from different samples indicate that the particles had similar size distributions but different elemental composition. Back-trajectories suggest that emissions from the Mediterranean Sea, remote wildfires, and dust events contributed to the long-range transported aerosol at the site. The sodium-rich particles, which likely originated from sea salts, constituted 29% of the collected aerosol in the morning, and dropped gradually to 8% in the afternoon. The back-trajectories and the elemental composition analysis suggest that the considerably low chloride in those particles is due to aging processes of sea salt transported from the Tyrrhenian Sea. Our analysis also show a large increase of carbonaceous particles, from 24% to 59%, at night. We observe the presence of tar balls in the night samples, as well. Unlike volatile organic particles, tar balls are stable under the electron beam. The increase of carbonaceous particles at night could be attributed to long range transport of biomass burning emissions. The morphological and chemical information on aerosol collected at high-altitude provides a better understanding of the atmospheric properties of free-tropospheric aerosol.