Robyn Nicole Conmy

Tracking Oil Dispersion in the Gulf of Mexico by Fluorescence Intensity (FI) and the Fluorescence Intensity Ratio (FIR)

Abstract Ultraviolet fluorescence (UVF) spectroscopy has been utilized to generate excitation-emission matrices (EEM) of thirteen reference oils (with viscosities ranging from 4 to 14,470 cP) and MC 252 source oil from the 2010 spill in the Gulf of Mexico. All of the oils were dispersed in seawater shaken in baffled flasks. The reference oils were dispersed at relatively high concentrations (650–836 ppm) by physical mixing or by using the chemical dispersant Corexit 9500 in combination with mixing. The matrices were reduced down to fluorescence intensity ratios (FIRs) obtained from two emission peaks at 340 and 445nm (with excitation fixed at 280nm), and the ratios compared to dispersed oil concentration. When oil concentrations were expressed as dispersion efficiencies, low FIRs (of less than 3 – 4) were associated with high dispersion efficiencies (greater than 40%) while FIRs greater than 3 – 4 were characteristic of oils dispersed with efficiencies of 20% or less. When the same dispersion techniques w...