Aerosolization of crude oil-dispersant slicks due to popping of bubbles*

Aerosolization of crude oil after spills due to the popping of bubbles on the ocean surface is one of the mechanisms by which the oil ejects into the atmosphere. Little is known about the effect of the oil physicochemical properties on the size distributions of these aerosols. In this study, bubble plumes with mode diameters of 86 µm (small), 178 µm (medium) and 595 µm (large) are injected into a seawater column covered by slicks of crude oil, Corexit 9500A dispersant, and premixed dispersant and crude oil at a ratio (DOR) of 1:25. Focusing on the sub-micron scales, in the presence of ambient air, the large bubbles cause an order of magnitude increase in the concentration of nano-aerosols for 500 µm thick slick of  DOR-1:25, and 50 µm slick of pure dispersant. The elevated concentration decays slowly (>20 min) after the bubble injection stops. To elucidate the latter phenomenon, additional tests show that although the increase in nano-droplet concentration persists, the decay is immediate in the presence of pure air. In ambient air, the increase is higher, and the decay is slower. Coating the tank walls with oil-absorbing pads accelerated the decay after bubble plume stops, suggesting the secondary production originating from the tank walls contributes to the slow decay