Characterization of Aerosol in the North Pacific Marine Boundary Layer using a High Resolution Time of Flight Aerosol Mass Spectrometer

The magnitude of particle formation from the oxidation of gaseous precursors (e.g. VOCs) in the marine atmosphere is still uncertain. As aerosols play important roles in influencing global climate and the chemistry of the remote atmosphere, it is important to study the composition of aerosols in oceanic regions. In order to increase understanding of the formation of particulate matter and the characteristics of aerosol over the ocean, field measurements were conducted from July 14th – 30th, 2012 from Incheon, Korea to Nome, Alaska, using a High Resolution Time of Flight Aerosol Mass Spectrometer (HR-ToF-AMS) on-board the Korean icebreaker R/V ARAON, as a part of the SHIPPO (Ship-borne Pole-to-Pole Observations) project. The cruise sailed from the Yellow Sea to the western portions of the North Pacific and Bering Sea through the East Sea (Sea of Japan). The HR-ToF-AMS deployed on the ship provided insight into particle size distributions and non-refractory fine particle composition, including concentrations of nitrate, sulfate, ammonium, chloride, and organic carbon, with a 5-minute time resolution. To screen out periods of contamination from the ship's exhaust, a variety of filtering criteria based on the AMS and other additional datasets (e.g. wind direction and gaseous CO concentrations) were applied. Many periods during the study were dominated by sulfate aerosol. The highest concentrations of sulfate and organic compounds were observed along the ship tracks in the Yellow Sea and in the vicinity of the Tsugaru Strait, Japan, being associated with continental outflow of anthropogenic sources from China, Korea, and Japan. The presentation will provide an overview of the composition of particulate matter measured in the remote and mostly pristine marine boundary layer and examine secondary aerosol formation over the ocean and the marine boundary layer with a focus on gaseous precursors and their influence on particle formation.