Laboratory Study on Dispersant Effectiveness in Alaskan Seawater

Abstract

The objective of this project was to test dispersant effectiveness in the laboratory under conditions relevant to Prince William Sound (PWS), Alaska. Two laboratory testing methods were used to compare a range of test conditions and dispersant to oil ratios (DORs) using PWS seawater at 8°C, Alaska North Slope (ANS) crude oil, and Corexit 9500. Three DORs were tested, 1:10, 1:20, and 1:50. It was found that in most cases, the dispersant effectiveness was directly proportional to the DOR. For each DOR, dispersant effectiveness was measured at four contact times (time between dispersant application to a spill and start of mixing) and five weathering times (time between oil spill and dispersant application). Corexit 9500 dispersed ANS crude oil at 8°C in PWS seawater to differing degrees, depending on the test conditions. The results indicated that, in general, the greatest dispersion occurred when the weathering time was minimized and a short contact time was provided.