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The petroleum industry is of great importance to the economic development in contemporary society. However, in the process of oilfield development and exploitation, the landing crude oil, oil-bearing sewage may cause different degrees of environment pollution, thus threatening human health. In the production process of oil field, the landing oil and oily sewage pose a serious threat to the surrounding environment. The best way to solve this problem is to reduce the pollution source. However, in the development and construction of oil and gas field, it is impossible to completely avoid the generation of landing oil and oily sewage (Gharib et al. 2018). Therefore, it is of great significance to study the migration and transformation of petroleum pollutants in soil. In recent years, with the exploitation and utilization of offshore oil resources, offshore oil spill accidents occur frequently in the production and transportation of petroleum processing products (Yu et al. 2018). Every year, about 3.2 million tons of oil in the world pollutes the ocean due to oil leakage. The oil film covers the surface of the sea water to block the air sea exchange, affecting the growth and reproduction of aquatic organisms, and destroying the balance of the entire marine ecosystem (Barringer 2019).
Petroleum is a complex mixture formed by the continuous evolution of ancient organisms, mainly composed of hydrocarbons composed of carbon and hydrogen, followed by non-hydrocarbon compounds containing oxygen, sulfur, nitrogen and other heteroatoms. The components of petroleum include saturated hydrocarbon, aromatic hydrocarbon, asphaltene compound and resin (Feldman et al. 2018). Heating distillation can decompose crude oil into fractions with different boiling points, including LPG, gasoline, kerosene, diesel oil and lubricating oil. Liquefied petroleum gas (LPG) is a kind of petroleum gas fuel which is mainly composed of alkanes. The main component of gasoline is liquid petroleum fraction with boiling point lower than 200°C, so it is volatile under normal temperature and pressure. In order to improve octane number of gasoline, a small amount of tetraethyl lead is often added (Hao et al. 2019). The petroleum fraction below 250°C accounts for 95% of kerosene, which is slightly volatile. Diesel oil is mainly used as the fuel of compression ignition internal combustion engines. The ignition temperature of diesel oil is above 50°C, and the petroleum fraction with boiling point below 350°C accounts for 90%. Under normal temperature and pressure, diesel oil has stable properties and low volatility (Gharib et al. 2018). The lubricating oil has a high ignition point, which can retain its properties for a long time when heated, and it is not easy to be volatilized or precipitated. Therefore, in addition to the low-carbon liquefied petroleum gas, other oil products are mainly liquid under room temperature and atmospheric pressure. From gasoline with low boiling point to lubricating oil with high boiling point, the ignition point, viscosity, density and chemical stability gradually increase (Yu et al. 2018). Polycyclic aromatic hydrocarbons (PAHs) and other toxic substances in petroleum only account for about 0.1% in crude oil, but they have strong carcinogenesis, teratogenesis and mutagenicity, and they will accumulate in the food chain step by step, which will pose a huge threat to human health. Absorption to PAHs can cause cataract, kidney problems, and hepatitis in the longer term. Contact with skin with the PAH propylene glycol on a regular basis can cause irritation and swelling. Large doses of naphthalene inhaled or swallowed can induce red cell disintegration. In the influence of uv radiation, they are often more poisonous. PAHs are hazardous to marine life including birds at relatively high doses. Marine oil spills are gradually becoming a major pollution to the marine environment, destroying the living environment of human beings and seriously threatening people's health (Yang et al. 2018).