By Loretta B Manele
The wind will blow the water currents and that will affect the movement of oil during an oil spill.
Dayne Maxwell, of Pacific Planning Consulting expressed this at the “Strengthening Marine Pollution Incident Resilience in the Pacific Islands” workshop that was conducted last month by SPREP (Secretariat of the Pacific Regional Environment Programme) at the Heritage Park Hotel.
He said there are two processes that take over when the wind blows the water currents affecting movement of the oil.
Maxwell stated that one of the processes is “oxidation” which is the effects of the sun breaking down oil and making it motionless or “inert”.
He went on to talk about “sedimentation” which he said is not a really good process because it will actually move oil down to the sediment.
“Sedimentation is when, if there’s sediment in the water column, for example, in marine areas where there’s fresh water coming out with rivers and streams that are flooding and causing a lot of sediment to be in the water, oil may attach to the sediment and that will change its buoyancy and will sink to the bottom”
Maxwell mentioned that this will affect any organisms or marine life that are living in the sediment.
On the other hand, in a negative aspect, he said there is also the uptake of violet.
“So, fishes, anything that’s swimming through the water column. Any oil dispersed in the water column, those molecules are available and just by the process of fish and water going through the gills or being swallowed, that will be taken up”
Maxwell said one of the other processes is related to the oil on the surface of the sea.
He referred to this as “persistent oil” particularly heavier fuel oils that may be spilled by larger vessels.
Maxwell pointed out that it is not crude oil that is coming through as crude oil is produced by drilling, gas and offshore oil installations.
He said there is no crude oil coming through only heavy fuel oil or intermediate fuel oils if they’re spilled in rough conditions which is then called a “water and oil emulsion”.
“That’s when oil and water mix together and they’ll create a more voluminous oily substance which, again, floats”
Moreover, Maxwell said you can use the modelling available to predict where oil is likely to move once it’s spilled.
“However, you can also do these calculations on your head or on a map or a chart or something”
Maxwell explained that the piece of information that you need are the wind speed and direction and also the current or the water movement.
He said a very simple calculation is that you just create a couple of vectors where one vector is the current speed and one vector is the wind speed.
“We take 100% of the current. If there’s an oil spilled in a channel and there’s one knot of current, you use a vector representing one knot of current. Then you look at the wind speed, but you take only 3% of the wind speed.
Then you draw another vector on top of the current. If we had, say, 15 knots of wind speed, we take 3% of 15, which is just under half a knot. We’d have a vector showing one knot of current and then whatever the wind speed is and wind direction, do half a knot.
Then you just draw an N and that will be where the oil is going. Typically, if you don’t have information on currents and you want to do a very rough calculation, where’s the wind blowing, that’s where the oil is going to go. 90% of the time you’ll be right”
Maxwell said the wind speed will determine how quickly the oil going to get there.
