Dispersion effectiveness of petroleum oils in low and hypersaline waters.

Chemical dispersant formulations typically provide maximum oil dispersion in waters between 30 and 40 ppt (parts per thousand) salt content, which encompasses typical 35 ppt ocean salinity. Ocean salinity can vary locally, from very low values due to freshwater river inflows or ice melt, to extremely high values during freeze up periods or within natural brine pools. In this study, the influence of salinity (0.2-125 ppt) on dispersion effectiveness (DE) was evaluated for three oils and four dispersants using the baffled flask test (BFT) and oil droplet size distribution (DSD) measures. Tank-scale dispersions support the laboratory-scale results of DSD. Light and medium crude oils were effectively dispersed over a wide salinity range using the BFT. However, dispersions exhibiting similar DE values possessed a wide range in DSD metrics, suggesting that the latter offers useful information for spill planning and understanding the transport and fate of spilled oil.