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How Oil Spreads

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The speed at which oil spreads over water largely depends upon the viscosity (thickness) of the oil, which in turn depends on the oil composition and the ambient (surrounding) temperature.  Low viscosity (thinner) oils spread more quickly than those with a high viscosity (thicker).  At a colder temperature, oil will tend to be more viscous than at a warmer temperature.  Spreading is rarely uniform, and large variations in the thickness of floating oil are typical.  The spreading of oil on the surface of the water near Gogama was controlled with containment booms.  Containment booms remained in place on the Makami River until the end of October 2015, after a thorough assessment of shoreline and river conditions showed that there were no measurable accumulations of oil on the surface of the water or shorelines.

The type of oil that spilled near Gogama is lighter than water, so it primarily stays on the surface of the water. It is not possible for this oil to sink and accumulate on the floor of the River or Lake, unless droplets of oil get dispersed by wave action and adhere to fine-grained particles suspended below the water surface, which then sink to the bottom of the River or Lake. CN collected over 150 sediment samples to determine whether impacts exist in the sediment within Minisinakwa Lake and the Makami River. Learn more about the sediment sampling and remediation work.

Sheen and Emulsion

Sheen is an extremely thin film of oil which float on top of water. According to the Bonn Agreement Oil Appearance Code, which is a widely used standard based on published scientific literature, laboratory and outdoor experiments and field trials, the thickness of sheen is less than 5 micron (µm). In comparison, the thickness of a human hair ranges from 17 µm to 180 µm. As sheen spreads on a water surface, the colour changes from rainbow (thickness of 0.3 - 5.0 µm) to silver or grey (thickness of 0.04 - 0.3 µm). There is a relatively small volume of oil associated with sheen, since the oil is spread in such a thin layer. For example, just over one cup of oil can cover the area of a football field with silver sheen. 

Oil emulsion is a mixture of oil and water droplets which forms due to turbulence in the water column (e.g. river current, wave action). Throughout the 2015 site work, CN contained and monitored the non-recoverable sheen and emulsion, as it broke down into harmless components by natural processes, such as exposure to sunlight and wave action.