Analysis of Dispersibility of Oil Frozen into Ice With and Without Dispersant

The work described in this report is an exploratory work carried out in the framework of the Project 2B “Unique Arctic Communities and Oil Spill response Consequences, Oil Biodegradation & Persistence”.

In 2015 the Arctic Oil Spill Response Technology – Joint Industry Programme (IP) executed a unique, long-term mesocosm experiment to improve the scientific knowledge of the fate and biodegradation of oil and oil spill response residues in ice, as well as the environmental effects to ice associated ecology. Eight mesocosms were installed in the sea ice of the Van Mijenfjorden in Svea, Svalbard, Norway in January 2015 and remained in place until July 2015. Oil was introduced into two mesocosms and allowed to freeze in without any treatment (natural attenuation). In two other mesocosms oil pre-mixed with dispersant was introduced and was allowed to freeze in. Ice cores were collected from all mesocosms at periods of 1, 2, and 3 months (labeled as T1, T2 and T3). These ice cores were subsequently melted in the CEDRE laboratory to simulate spring ice melt and the release of oil into open water. Effectiveness of dispersion was tested with fresh reference oil, oil melted from ice untreated with dispersant prior to encapsulation, untreated oil treated with dispersants after the melt and oil pre-mixed with dispersant prior to being frozen into ice.

The main findings of these tests are:

  • Fresh dispersant applied to oil melted from the ice cores after 3 months of being frozen in achieved good efficiency.
  • Dispersant mixed with the oil prior to being frozen in was still efficient even after 3 months trapped in at the upper surface of the ice sheet, although with reduced efficiency compared to fresh samples.