Quirks & Quarks

What happens to oil spills after dispersant is used?

Chemical oil dispersants help speed up the natural biodegradation of oil

Chemical oil dispersants help speed up the natural biodegradation of oil

Indian Coast Guard cadets sprinkle Oil Spill Dispersant (OSD) onto a thick oily tide on the waters of the Bay of Bengal. (ARUN SANKAR/AFP/Getty Images)

This week's question comes from Stewart Vriesinga from Teeswater, Ont. He asks:

What happens to oil spills after they are dispersed? Does dispersion render oil spills biodegradable and innocuous, or does it just disperse the oil throughout the entire ocean thereby reducing the oil to permissible levels?

Ken Lee, the National Senior Science Advisor for oil spill research, preparedness and response for Fisheries and Oceans Canada, says that chemical oil dispersants work the same way your dish detergent works.

The dispersants break the oil down into small droplets which are diluted to a non-toxic concentration in the water. Those droplets are then small enough for natural ocean bacteria to biodegrade the oil.

Lee says we don't even need to use chemical dispersants to break up the oil under some circumstances. The dispersants just speed up the process. Big storm events with crashing waves can break up the oil and dilute it in the water.

Once it's broken up into smaller droplets by dispersants or storms, the oil is then biodegraded at a faster rate because there is more surface area for the bacteria to attack.


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