Dispersant Effectiveness on Oil Spills: Impact of Environmental Factors

Abstract: When a dispersant is applied to an oil slick, its effectiveness in dispersing the spilled oil depends on various factors such as oil properties, wave mixing energy, temperature of both oil and water, and salinity of the water. Estuaries represent water with varying salinities. In this study three salinity values in the range of 10-34 ppt (parts per thousand) were investigated, representing potential salinity concentrations found in typical estuaries. Three oils were chosen to represent light refined oil, light crude oil and medium crude oil. Each oil was tested at three weathering levels to represent maximum, medium and zero weathering. Two dispersants were chosen for evaluation. A modified trypsinizing flask termed the 'Baffled Flask' was used for conducting the experimental runs. A full factorial experiment was conducted for each oil to investigate the effect of salinity on three environmental factors: temperature (4 levels), oil weathering (3 levels) and mixing energy (150,200 and 250 rpm). Each experiment was replicated four times in order to evaluate the accuracy of the test. Statistical analyses of the experimental data were performed separately for each of the three oils three times (with or without dispersant). A linear regression model representing the main factors (salinity, temperature, oil weathering and flask speed) and second order interactions among the factors were accurately fit to the experimental data. Salinity was found to play an important role in determining the significance of temperature and mixing energy on dispersant effectiveness for almost all the oil dispersant combinations