In the process of oil drilling, extraction, refining, transportation and use, some oil will be lost to the surrounding environment, and some losses are unavoidable during the operation (see Figure 1). The recovery rate of oil in the ore vein is 30% when mining oil, and the recovery rate can reach 40% to 50% when new technology is adopted. 0.01%~0.02% of oil is lost when exploring and producing oil using oil wells. The large volumes of brine pumped out with oil extraction are generally back-injected into oil wells, but sometimes also flow into surface waters, especially when offshore oil is being extracted. This can be a factor affecting the marine water environment. By refining petroleum, people can obtain various hydrocarbon compounds, fuels, asphalt and various petrochemical products. It is worth noting that about 10% of the total oil processed is consumed in various processing and refining processes.
With its huge capacity, the ocean absorbs pollutants from various natural sources and anthropogenic activities. Among the increasingly serious marine pollution in recent decades, the most striking is the oil pollution of the ocean. Much oil is transported by sea, and about 50 percent of that is used to ship fossil fuels, 30 percent of which is crude oil, 11 percent is petroleum products, and 9 percent is coal.
Marine oil pollution has brought a series of harmful effects to the marine ecology, which will cause a variety of environmental effects. The heavier, less mobile parts of the pollutant are difficult to remove and generally cause considerable environmental damage, especially when the coast is polluted. The pollution of the ocean by hydrocarbon compounds has greatly affected the aquatic organisms and seabirds in the nearby waters, and the beach tourism industry has suffered great losses.
The world’s oceans already have the distribution of obvious oil films, and the low-concentration soluble petroleum components of several micrograms per liter have spread to every corner of the ocean. The oil film on the surface of seawater can hinder the gas exchange between seawater and air, resulting in biological hypoxia in seawater. Due to the influence of the oil film, the photosynthesis of marine algae has been drastically reduced, resulting in a reduction in the oxygen production of the ocean, and at the same time affecting the growth and reproduction of other marine organisms, affecting the entire marine ecosystem.
Certain components in petroleum are also toxic to the digestive tract. Hydrocarbon compounds are also biodegradable organic substances, and the time required for degradation is longer or shorter, so they can be called nutritious substances. The first stage of biodegradation, which results in a reduction in nitrogen and phosphorous and dissolved oxygen concentrations within the water body, is followed by eutrophication of the waters and consequent mineralization of animals killed by oil pollution. Oil slicks contaminate the food chain with toxins, including carcinogens. The concentration of benzo carcinogens in fish, shrimp and sea cucumbers in polluted sea areas increased significantly.
In addition, pesticides such as chlorohydrocarbons or some components in petroleum that were originally dispersed in seawater and concentrated by oil slicks on the sea surface are similar to the normal chemical information of some marine organisms. This kind of false information due to oil pollution affects the foraging, mating, migration and other behaviors of many fish and shrimp. Tests have shown that several 10-9 concentrations of kerosene can cause lobsters to leave their natural feeding grounds and swim to oil-contaminated areas. This is an extremely harmful effect of marine oil pollution on marine life.
When the coast is polluted by these oil known as “Black Sea Tides”, the beach tourism industry suffers all kinds of losses. The once prosperous and picturesque blue coast suddenly became depressed and deserted. This scenario has repeatedly occurred in coastal cities in Spain, France and other countries in recent years.