AAAR 36th Annual Conference October 16 - October 20, 2017 Raleigh Convention Center Raleigh, North Carolina, USA
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Molecular Characteristics of Long-range Transported Organic Aerosol at the Pico Mountain Observatory (PMO)
SIMEON SCHUM, Bo Zhang, Katja Dzepina, Paulo Fialho, Claudio Mazzoleni, Lynn Mazzoleni, Michigan Technological University
Abstract Number: 353 Working Group: Remote and Regional Atmospheric Aerosols
Abstract The properties of remote free tropospheric aerosol are impacted by the continental outflow of pollutants, their chemical transformation, and removal mechanisms. To investigate this, we determined the molecular characteristics of long-range transported aerosol from North America collected at the Pico Mountain Observatory (PMO, 38.47°N, 28.40°W, 2225 m above sea level). PMO is located within the marine free troposphere on Pico Island in the Azores archipelago and is an ideal location to sample aged free tropospheric aerosols, as it is far from large orographic systems and is primarily above the marine boundary layer. Aerosol samples from pollution events in the summers of 2013, 2014, and 2015 were selected for ultrahigh resolution ESI-FT-ICR MS characterization of water-soluble organic carbon. Thousands of molecular formulas were identified in all the samples, ~60% contained only carbon, hydrogen, and oxygen, ~30% contained nitrogen, and ~10% contained sulfur. FLEXPART back trajectory analysis was performed for the three sample periods and indicated that two of the samples were primarily transported above the marine boundary layer, while the third was primarily transported within the marine boundary layer. Differences in the transport patterns are reflected in the molecular characteristics of the aerosol, with the two free troposphere transported samples having lower average O/C ratios (0.46 & 0.47) and OSc values (-0.411 & -0.348) compared to the boundary layer transported sample (O/C = 0.55 & OSc = -0.279). This difference in apparent oxidation for aerosol transported in the boundary layer versus in the free troposphere has not been previously described and is the focus of this presentation.