Single Particle Characterization of Free Tropospheric Aerosols at the Pico Mountain Observatory over the North Atlantic

Wednesday, 17 December 2014: 9:30 AM
Claudio Mazzoleni1, Swarup China1, Barbara V Scarnato2, Ryan Moffet3, Rachel E OBrien4, Mary Kathleen Gilles5, Paulo JLCS Fialho6, Marian Ampadu1, Sumit Kumar1, Katja Dzepina1, Kendra Wright1, Noopur Sharma1, Bo Zhang1, Robert Chris Owen1,7, Judith A Perlinger1, Jacques Hueber8, Detlev Helmig8, Michael Dziobak1, Louisa J Kramer1 and Lynn R Mazzoleni1, (1)Michigan Technological University, Houghton, MI, United States, (2)Naval Postgraduate School, Monterey, CA, United States, (3)University of the Pacific, Stockton, CA, United States, (4)University of the Pacific, Department of Chemistry, Stockton, CA, United States, (5)Lawrence Berkeley National Lab, Berkeley, CA, United States, (6)University of the Azores, Azores, Portugal, (7)Environmental Protection Agency Research Triangle Park, Research Triangle Park, NC, United States, (8)University of Colorado at Boulder, Institute of Arctic and Alpine Research, Boulder, CO, United States
Free tropospheric aerosols are being studied at the Pico Mountain Observatory, located near the top of the Pico volcano in the Azores, Portugal (38.47°N, 28.40°W, 2225m asl). Typically above the marine boundary layer in the summer, this is an ideal site to study aerosol transported over long distances across the Atlantic Ocean. Aerosols reaching the Observatory often originate from North America and sometimes from Africa and Europe. Aerosols instrumentation deployed at the site include: a) an optical particle counter, b) a 7-wavelength aethalometer to measure black carbon equivalent mass concentration, c) a 3-wavelength nephelometer to measure total and backward light scattering, d) four high volume samplers for aerosol chemical characterization, and e) a sequential aerosol sampler and a 4-stage impactor to collect particles on different substrates for microscopy analysis. The origin and transport pathways of the air masses sampled at the site are determined using FLEXible PARTicle (FLEXPART) dispersion modeling retroplume analysis. Single particle morphology and mixing states were determined using electron microscopy, energy dispersive X-ray spectroscopy, and scanning transmission x-ray microscopy.

This study provides an overview of different types of aerosol collected at Pico Mountain Observatory. We investigated morphology and mixing of various types of particles, including dust, soot, salt and organic particles transported to the Observatory. Soot particles were often mixed/coated with other material and exhibited very compact shape. Dust particles were often mixed with sulfur containing species. We also observed dust particles that were mixed with coated soot particles. During some events, we observed soot and sulfate aerosol trapped within organic matter. The results of this study have implications on how aerosol particles and their internal mixing can be represented in numerical models for remote regions of the free troposphere.