Crude oil is a non-renewable naturally occurring resource composed of a wide variety of chemicals, that results in a substance with multiple physicochemical properties and behaviors. Crude oil is mainly composed of hydrocarbons and other organic units with heteroatom substituents 1, 2. Over the last century, the industrial expansion and population growth have led to an increase in the use of different types of fossil fuels such as petroleum oil, as energy sources to improve the quality of social and commercial activities 3, 4. According to Al-Majed et. al., in order to maintain fossil fuels stocks worldwide, by 2005 around 5 million tons of petroleum were yearly transported overseas, thereby increasing the risk of accidental oil spills 5. Overall, all the life cycle stages of the oil industry (e.g. production, refining, storage, and distribution) represent somehow a potential source for water, soil and air pollution 6. Pipelines, storage tanks, refineries, drilling digs, wells, and platforms are considered the major causes of accidental oil releases into different environments 1. Even though new technologies and preventive regulations have been implemented to prevent ecological disasters from accidental oil spills, the complexity of oil mixtures in mobile aquatic environments is still a challenge to overcome 1.
Currently, due to the depletion of many terrestrial reservoirs, nearly 33% of the oil production is obtained from underwater reservoirs6. This has resulted in more than 7 million tons of oil release into the marine environment from over 104 spills between 1907 to 2014 7. Within the catastrophic marine oil spills occurred during the last decades, 2010 BP Deepwater Horizon constituted one of the largest marine oil spills releasing about 208.5 million gallons (686,000 tons) of crude oil into the Gulf of Mexico, causing the dead of 11 people and of more than 900 birds, 400 sea turtles and 47 mammals 5, 8. The largest oil spill in history is considered to be 1990 Gulf war in which 1 million tons of oil were discharge into the Persian Gulf, killing 20 thousand sea birds 9. According to Ivshina et. al, spill incidents are correlated with deeper waters, funding that every 30 meters depth added to an overage platform increases the oil spill incident probability by 8.5%10. Different policies and regulations related to oil spill prevention and response have been developed to ensure a safe and clean environment for everyone. In 1990, it was established the Oil Pollution Act (OPA) regulated by the EPA, to prevent and clean up oil spills in U.S. waters and in 1989, the International Maritime Organization (IMO) established an international convention on oil water preparedness, response, and cooperation 7.
Different technologies have been considered and evaluated as response techniques for the rapid remediation of accidental oil spills. The most common remediation mechanisms can be either physical (e.g., booms or skimmers), chemical (e.g., dispersants or in situ burning) and/or biological (e.g., biodegradation) 1. However, changes in the physicochemical properties of the oil once release into an aquatic environment, has been found to affect the effectiveness of some of the currently used technologies and make clean up much more difficult5. Once released, oil undergoes different processes known as “weathering” where lighter volatile components are evaporated into the air while polar components dissolve into the water, resulting in a heavier and apolar oil spill. Furthermore, small particles can sink to the bottom and oil in the surface can be biodegraded by native microorganisms 1, 6. When emulsification occurs, the resulting oil presents a higher viscosity thereby affecting negatively the effectiveness of skimming and dispersion remediation technologies 1. For this reason, the spill location, its environmental characteristics, and magnitude are often used to determine the most appropriate clean-up technology 6, 7. Due to the lack of appropriate and effective remediation mechanisms for large oil spills, new approaches such as chemical absorbents3, magnetic particles1, and photochemical processes11 have been evaluated as potential alternatives for oil remediation.
Finally, it is important to have clear the differences between marine and terrestrial oil spills because its remediation can be completely opposite. First, the fast weathering process from oil spill in water results in uncertain environmental fates and behaviors. Furthermore, marine spills remain in motion being more difficult to locate. In contrast, terrestrial oil spills present a slower downward flow and usually accumulate in depressions. For these reasons, it is more accurate to predict and thereby to find appropriate remediation responses. However, oil in soil spills fate can also be greatly affected by oil viscosity and surface conditions 6. Therefore, the objective of this paper is to summarize the currently used technologies for rapid oil spill remediation and their disadvantages under different environmental conditions. Furthermore, it will be provided information about new and potential alternatives for sustainable prevention and mitigation of offshore oil spills.