The media has been reporting that operations to clean up the oil in the Gulf of Mexico now include the use of dispersants. Dispersants are sprayed onto marine oil spills in an attempt to break the oil slick into smaller droplets more rapidly than just wave action alone. These smaller droplets are removed from the surface of the water and sink them into the water column where they biodegrade more rapidly. Dispersants can prevent oil slicks from reaching coastal wetlands where they destroy ecosystems and kill nesting birds. Dispersants do not work well on oil that has been exposed to the air for a longer period of time because of chemical changes to the oil due to evaporation and emulsification (mixing with water). As oil ages, dispersants tend to flow off the surface of the oil rather than absorbing it, making dispersal of the oil less likely to occur.
Dispersants do not get rid of the oil, the same amount of oil is still present in the water, however, it is dispersed within the column and cannot be seen (mainly by the media and general public). It's rather like sweeping dirt under the carpet. The shorelines look pristine and birds are protected at the cost of further damage to the turtles, fish and other inhabitants of the marine ecosystem. Basically, the use of dispersants is sacrificing the deeper marine ecosystem to preserve the ecosystem that humans see everyday, the coastal marshes and beaches.
I thought I'd take a look at one of the dispersants BP is using. Corexit is manufactured by the Nalco Company headquartered in Naperville Illinois. As of May 5th, the New York Times reported that 160,000 gallons of Corexit had been aerially sprayed on the oil spill and that BP had pumped an additional 6000 gallons directly onto the leaking underwater structure. Corexit contains 2-Butoxyethanol, organic sulfonic acid salt and propylene glycol. 2-Butoxyethanol is the active ingredient in Windex and acts as a degreaser (thus my title "The Gulf of Mexico - Now Squeaky Clean"). Nalco did release this document showing partial chemical composition of their product, however, other ingredients of Corexit are deemed by Nalco to be proprietary (secret). In other words, the public will never know exactly what chemicals are being dumped into the Gulf.
Here's a screen cap from the Nalco website summarizing the technology behind Corexit:
Here's a screen cap from their press release about the chemical composition of Corexit and what hazards it poses:
Repeated exposure to 2-Butoxyethanol can cause hemolysis (damage to red blood cells), kidney and/or liver damage. Excessive exposure may cause central nervous system effects, nausea, vomiting, anesthetic or narcotic effects. Animal studies have shown that exposure can result in fertility reduction, embryo death and birth defects. While 2-butoxyethanol has been removed from the U.S. EPA's list of hazardous air pollutants, it is still on California's list of hazardous substances.
Organic sulfonic acid salt or sulfonates are often used in the detergent industry. Their advantage is that they do not form a scum when added to hard water compared to other chemicals. They are considered to be a strong acid and are quite soluble in water.
Propylene glycol is a very common chemical used in food items, medicines, moisturizers and as a coolant. It is quite biodegradeable.
One problem with Corexit is that its effectiveness in dispersing oil is widely variable depending on the chemical composition and amount of weathering of the oil (how long it has been exposed to the atmosphere), the water conditions including salinity and water temperature and degree of water agitation. In some cases, scientific analysis shows that its effectiveness can be as high as 93% and as low as 19% in agitated water. With fresh crude and a water temperature of 22 degrees Celcius, Corexit products dispersed oil between 16% and 35%.
Since the degree of effectiveness is not known until the dispersant is applied, the use of Corexit in the Gulf of Mexico is tantamount to a huge science experiment. I realize that something has to be done to remediate the ongoing damage to the Gulf ecosystem, I'm just not certain that dumping more chemicals is the solution.
Effectiveness of Dispersants on Oil Spills for Coastal Habitats