AAAR 37th Annual Conference October 14 - October 18, 2019 Oregon Convention Center Portland, Oregon, USA
Abstract View
Impacts of Adding Dispersant on Aerosolization of Fine and Ultrafine Particulate Matter after an Oil Spill
NIMA AFSHAR-MOHAJER, Lakshmana Dora, Andres Lam, Ana Rule, Joseph Katz, Kirsten Koehler, Johns Hopkins School of Public Health
Abstract Number: 150 Working Group: Health-Related Aerosols
Abstract Bubble bursting of oceanic whitecaps is a primary source of marine aerosol emission. After an oil spill, inhalation of the fine PM containing toxic petrochemical compounds, emitted due to bubble bursting, cause serious pulmonary diseases to cleanup workers and nearby inhalers. Spraying chemical dispersants to enhance distribution of the crude oil into the water was employed extensively during the Deepwater Horizon spill. However, our previous work has shown an increase in fine PM with use of chemical dispersants. Risk assessment of such exposure requires information about the chemical composition of the airborne PM. In this study, we determined the chemical constituents of the fine PM (PM2.5) and ultrafine PM (UFPs) emitted from seawater covered with a crude oil (MC252 surrogate) slick of 0.5 mm, before and after mixing with dispersant (Corexit 9500A, dispersant to oil ratio of 1:25 Vol./Vol.). Aerosol generation was facilitated through the bursting of air bubbles injected at controlled diameter of 0.6 mm into a vertical seawater column (L=0.3, W=0.3, and H=0.6 m), the bubbles rise to the oil-contaminated water surface and burst. The resulting aerosols were sampled onto 37-mm quartz filters using a Personal Environmental Monitor (PEM) for PM2.5 and a filter/cassette for total suspended particles with and without presence of dispersant. Using Pentane as solvent, PM were extracted from the filters, then analyzed for composition via a gas chromatography/mass spectrometry system. Primary tests confirmed demonstrated that dodecane and 1-(-2-butoxy-1-methylethoxy)-2-propanol (BMEP) are the best identifiers for crude oil and dispersant, respectively. The crude oil marker of dodecane exists in PM2.5 filters obtained from the experiments with seawater polluted by the mixture slick. As an indicator for increase in concentration of the finer PM, the dodecane content of the TSP filters reduced 19.2% (61.2 to 49.4 µg/mL) when dispersant was the sprayed, but the dodecane content of the PM2.5 increased 7.4% (33.4 to 35.6 µg/mL). Furthermore, a 12-stage low-pressure cascade impactor (LPCI) collected the particles with size bins to be with cut off diameters of 9.5, 6.2, 4.2, 2.9, 1.8, 0.95, 0.51, 0.38, 0.30, 0.20, 0.13, and 0.056 µm onto 81-mm filters. Both dodecane and BMEP were detected on the filters collected from multiple stages of the LPCI. Changes in dodecane contents at each stage compared to the case without dispersant, and anticipated health impacts will also be presented.