AAAR 35th Annual Conference October 17 - October 21, 2016 Oregon Convention Center Portland, Oregon, USA
Abstract View
Characterization of Marine Aerosol by the Novel Event Trigger (ET) Single Particle Mode of an Aerodyne Aerosol Mass Spectrometer during the NAAMES Campaign
Abstract Number: 368 Working Group: Instrumentation and Methods
Abstract The influence of ocean ecosystems on the physical properties and chemical composition of marine aerosol was investigated during the North Atlantic Aerosols and Marine Ecosystems Study (NAAMES). Measurements of marine aerosol were taken over two separate 26-day research cruises (winter and spring) on the R/V Atlantis. The ship embarked from Woods Hole Massachusetts and measured ambient particles while following an approximately triangular transect with turning points at 57 N, 40 W and 40 N, 40 W. Primary marine aerosol was modeled using a bubble-bursting/collection technique (Sea Sweep). The ambient and generated marine aerosol was characterized by a suite of instruments, including a high resolution – time of flight – aerosol mass spectrometer (HR-ToF-AMS, Aerodyne Inc.) upgraded with an event trigger (ET) single particle operating mode. The ET mode was set to have three regions of interest (ROI), including m/z 43, m/z 55-79, and m/z 48-150 with optimized event trigger levels. A k-means algorithm was used to cluster the single particles into different composition classes. Four composition classes were determined for the ambient marine aerosol and include a hydrocarbon-like organic aerosol (HOA) class, an oxygenated organic aerosol (OOA) class, and two sulfate classes. The two sulfate classes account for more than 50% of the total ambient marine aerosol and are from organosulfate and sulfuric acid compounds likely formed from dimethyl sulfide (DMS) and methanesulfonic acid (MSA) precursors from the ocean plankton ecosystem. The HOA and OOA classes are more abundant in continental aerosol, likely due to anthropogenic emissions from North America. Four composition classes were determined for the Sea Sweep aerosol and include two HOA classes, a combined OOA and sulfate class, and a sea salt class. Sea salt particles are typically refractory and are not easily detected by the HR-ToF-AMS. Therefore, the sea salt class contributes only 8% of the total non-refractory aerosol.