Oil Droplet Size Distribution and Optical Properties During Wave Tank Simulated Oil Spills

Fate and transport of spilled petroleum oils in aquatic environments is highly dependent upon oil droplet behavior which is a function of chemical composition, dispersibility (natural and chemically-enhanced) and droplet size distribution (DSD) of the oil. DSD is influenced by mixing energy, temperature, salinity, pressure, presence of dissolved and particulate materials, flow rate of release, and application of dispersants. To better understand DSD and droplet behavior under varying physical conditions, flask-scale experiments are often insufficient. Rather, wave tank simulations allow for scaling to field conditions. Presented here are experiment results from the Bedford Institute of Oceanography wave tank facility, where chemically-dispersed (Corexit 9500; DOR = 1:20) Louisiana Sweet crude, IFO-120 and ANS crude oil were exposed to mixing energies to achieve dispersant effectiveness observed in the field. Oil plumes were simulated, both surface and subsea releases with varying water temperature and flow rate. Fluorometers (Chelsea Technologies Group AQUATracka, Turner Designs Cyclops, WET Labs Inc ECO) and particle size analyzers (Sequoia LISST) were used to track the dispersed plumes in the tank and characterize oil droplets. Sensors were validated with known oil volumes (down to 300 ppb) and measured Total Petroleum Hydrocarbons (TPH) and Benzene-Toluene-Ethylbenzene-Xylene (BTEX) values. This work has large implications for tracking surface and deep sea oil plumes with fluorescence and particle size analyzers, improved weathering and biodegradation estimates, and understanding the fate and transport of spill oil.