Experiments Mimicking Breathing of Dolphins near Oil Slick

The dynamics of respiratory flow rate and associated aerosols created during breathing events by trained bottlenose dolphins were measured in the National Aquarium in Baltimore. To characterize the exposure and risk posed to marine mammals during oil spills, we constructed and calibrated a laboratory setup mimicking the flow and aerosol generated by the dolphins, where one can introduce crude oils and oil-dispersant mixtures. The exhalation is reproduced by venting compressed air from a pressurized tank representing the lungs through a fast-actuating valve, two aerosol generators, and a pool of seawater on top of the valve representing water accumulated in the dimple above the blowhole. The inhalation is reproduced by opening a second valve leading to another tank, maintained under partial vacuum, shortly after the first valve is closed. The timing and durations of both valves as well as the flow rates and aerosol concentration and size distributions are matched with those of the dolphins. For tests involving oil, slicks of marine diesel fuel and MC20 crude oil in different states (fresh, weathered and emulsified), with thicknesses of 2, 10, and 100 μm, are added to the pool above the exhalation valve. Dispersants at relevant concentrations are premixed with the oil to determine their effects. 2D PIV is used for measuring the velocity distributions, and high-speed holography for the time evolution of aerosols above the exhalation and inhalation valves. The total amounts of water and oil inhaled are also measured.