An oil spill is the release of a liquid petroleum hydrocarbon into the environment due to human activity and is a form of pollution. Oil spills stem from accidents involving tankers, barges, pipelines, refineries, and storage facilities, often while the oil is being transported to its users.
For instance, the April 2010 Gulf of Mexico oil spill involved crude oil that was released from the explosion of the off-shore drilling rig.
During an oil spill cleanup, workers may encounter many types of crude oil, including fresh and weathered, which contain carcinogenic volatile aromatic compounds like benzene, toluene and naphthalene.
The first thing we need to discuss is the various types of oil that might require cleanup. Spill responders group oil into four basic types, which you can see here, along with a general summary of how each type can affect shorelines.
Type 1: Very Light Oils (Jet Fuels, Gasoline)
Type 2: Light Oils (Diesel, No. 2 Fuel Oil, Light Crudes)
Type 3: Medium Oils (Most Crude Oils)
Type 4: Heavy Oils (Heavy Crude Oils, No. 6 Fuel Oil, Bunker C)
Health hazards generally associated with crude oils: Inhalation of the toxic volatile hydrocarbon components, such as benzene, and dermatitis from repeated or prolonged skin contact can cause dermatitis or skin cancer.
Be cautious during cleanup operations. If you are unsure, ask your supervisor before proceeding!
Weathered crude or "mousse" is crude petroleum that has lost an appreciable quantity of its more volatile components and has mixed with sea water and organic matter. This is caused by evaporation and other natural causes during the spill landing on the shore and during oily waste handling, storage and treatment or disposal.
The various types of oil differ in how they weather (chemically or physically change when exposed to the elements). Most crude oil blends will emulsify quickly when spilled, creating a stable mousse that presents a more persistent cleanup and removal challenge.
Even in high winds, usually over 70% of a Fuel Oil No. 6 spill will persist as floating or beached oil for a week or longer. On the other hand, over 90% of the diesel in a small spill in the marine environment is either evaporated or naturally dispersed into the water column in time frames of a couple of hours to a couple of days.
Weathering is a series of chemical and physical changes that cause spilled oil to break down and become heavier than water. Winds, waves, and currents may result in natural dispersion, breaking a slick into droplets which are then distributed throughout the water. These droplets may also result in the creation of a secondary slick or thin film on the surface of the water.
Adsorption (sedimentation) is the process by which one substance is attracted to and adheres to the surface of another substance without actually penetrating its internal structure.
Biodegradation is the degradation of substances resulting from their use as food energy sources by certain micro-organisms including bacteria, fungi, and yeasts.
Dispersion is the distribution of spilled oil into the upper layers of the water column by natural wave action or application of chemical dispersants.
Dissolution is the act or process of dissolving one substance in another.
Emulsification is the process whereby one liquid is dispersed into another liquid in the form of small droplets.
Evaporation occurs when the lighter substances within the oil mixture become vapors and leave the surface of the water. This process leaves behind the heavier components of the oil, which may undergo further weathering or may sink to the ocean floor.
Oxidation occurs when oil contacts the water and oxygen combines with the oil to produce water-soluble compounds. This process affects oil slicks mostly around their edges. Photo Oxidation is a sunlight-promoted chemical reaction of oxygen in the air and oil.
Health risks associated with working while exposed to weathered crude oil include the following:
NOTE: Even if air sampling shows no detectable levels or very low levels of volatile organic compounds (VOCs), there still may be health effects present.
Tarballs, the little, dark-colored pieces of oil that can sometimes stick to your feet when you go to the beach, are actually remnants of oil spills. When crude oil (or a heavier refined product) floats on the ocean surface, its physical characteristics change.
During the first few hours of a spill, the oil spreads into a thin slick. Winds and waves tear the slick into smaller patches that are scattered over a much wider area. Various physical, chemical, and biological processes change the appearance of the oil. These processes are generally called "weathering." Weathering processes eventually create a tarball that is hard and crusty on the outside and soft and gooey on the inside, not unlike a toasted marshmallow.
Tarballs are very persistent in the marine environment and can travel hundreds of miles. There is no magic trick to making tarballs disappear. Once tarballs hit the beaches, they may be picked up by hand or by beach-cleaning machinery. If the impact is severe, the top layer of sand containing the tarballs may be removed and replaced with clean sand.
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