AAAR 36th Annual Conference October 16 - October 20, 2017 Raleigh Convention Center Raleigh, North Carolina, USA
Abstract View
Aerosol Emission from Seawater Contaminated by Crude Oil and Crude Oil-Dispersant Slicks due to Bubble Bursting
NIMA AFSHAR-MOHAJER, Kaushik Sampath, Ana Rule, Joseph Katz, Kirsten Koehler, Johns Hopkins University
Abstract Number: 548 Working Group: Aerosol Physics
Abstract Bubble bursting observed in oceanic whitecaps is a well-known mechanism of marine aerosol generation from seawater surfaces. Although spills of crude oil occur frequently in the ocean, the emission of oily marine aerosols ejected to the atmosphere due to bubble bursting has not been detailed. The use of chemical dispersants as a treatment strategy for oil spills significantly reduces the oil-water interfacial tension, thereby altering the size distribution of the aerosolized particles. The purpose of this study is to characterize particles aerosolized from an oil slick due to the bubble bursting, with and without the use of chemical dispersants. A mechanical shear based nozzle is used to generate a controlled bubble cloud that is injected into a vertical seawater column (0.6 m diameter, 1.8 m high). The bubbles rise to the oil-contaminated water surface and eventually burst. The resulting concentration of aerosolized droplets is measured by an aerodynamic particle sizer (APS) covering 0.5-20 µm and a scanning mobility particle sizer (SMPS) covering 10-370 nm particles. Planar bubble fluorescence imaging is used to measure subsurface bubble size and velocity distributions. Measurements are performed at the same air injection rate for varying bubble diameters (0.18, 0.4 and 1.4 mm), slick thicknesses (0.1 and 0.5 mm) and interfacial tensions (crude oil, and crude oil premixed with the dispersant Corexit 9500A (Nalco) at dispersant to oil ratios of 1:100 and 1:25). Results show that there is a considerable increase in the number concentration of micron-sized droplets (particle mode size of 2-5 µm) for all cases after bubble bursting. The number concentration increases with a decrease in bubble diameter, and a decrease in slick thickness. These findings help provide evidence on aerosol size distributions and their emission rate needed for the evaluation of health concerns and risks associated with the inhalation of oil and dispersant particles.