A new study conducted by the University of Miami (UM) Rosenstiel School of Marine and Atmospheric Science has shed new light on oil dissipates in the oceans after spills. It also talks about the effects chemical dispersants have on the marine environment. The study demonstrated that under realistic environmental conditions, oil drifting in oceans after a spill could photo-oxidise into persistent compounds within hours to days. This may take place sooner than the long periods of time, as thought previously by the scientists during the 2010 Deepwater Horizon oil spill.
The new research is the first model result to support the new example of photo-oxidation that emerged from laboratory work. Usually, after an oil spill, the droplets weather down and degrade due to continuous exposure to sunlight and oxygen – this weathering process is known as photo-oxidation. This further results in the degradation of crude oil into other carbon-based by-products over time.
One such example of the by-product is tar, which is used for laying asphalt roads. It is a product of this same degradation process. However, tar generated from such a process can remain in coastal areas for decades after a spill.
The researchers from the UM Rosenstiel School first presented their findings in a report published in the journal Frontiers in Marine Science, titled ‘A Coupled Lagrangian-Earth System Model for Predicting Oil Photooxidation.’ The team, in order to understand how sunlight degrades oil, developed the first oil-spill model algorithm that can track the dose of solar radiation in oil droplets as they rise from deep-sea and up to the ocean surface.
The research team found that the weathering oil droplets due to solar exposure occurred within hours to days. Furthermore, roughly 75 per cent of the photo-oxidation during the Deepwater Horizon oil spill happened in the same areas where chemical dispersants were sprayed aerially. Photo-oxidized oil is known to reduce the effectiveness of aerial dispersants due to the presence of hydrocarbon products.
According to Claire Paris, UM Rosenstiel School faculty and senior author of the study, it is crucial to understand the ‘timing’ and ‘location’ of this weathering process. “It helps in directing efforts and resources on fresh oil while avoiding stressing the environment with chemical dispersants on oil that cannot be dispersed,” Paris added.