Application of Ultraviolet Fluorescence Spectroscopy to Monitor Oil–Mineral Aggregate Formation

At an excitation wavelength of 320 nm, the ultraviolet fluorescence (UVF) spectra emitted by reference oils dispersed in seawater with mineral fines yielded two important results: (1) Resuspended negatively-buoyant oil–mineral aggregates (OMAs) exhibited maximum fluorescence at an emission wavelength of 450 nm and, (2) the hydrocarbons dispersed and/or dissolved in the seawater that remained after the aggregates had settled out exhibited maximum fluorescence at 355 nm. Data from UVF analysis (450 nm emission) and microscopical observations of seven reference oils suggest that higher-viscosity oils are less likely to form aggregates with mineral fines. This decline in OMA formation with increased oil viscosity could be predicted from a decrease in the ratio of emission at 450–355 nm. The data suggest that direct UVF spectroscopy of dispersed/dissolved oil and OMAs in seawater can be used to predict and verify the extent of OMA formation.