Polycyclic aromatic hydrocarbon (PAHs) are hydrocarbons containing two or more benzene rings in the molecule. They are a typical type of persistent organic pollutants. They are usually found in petrochemical products, rubber, plastic, lubricating oil, rust - proof oil, Compounds and other substances, is one of the important carcinogens in the environment. After the 21st century more than 16 kinds of carcinogenic polycyclic aromatic hydrocarbon were banned.
The source of polycyclic aromatic hydrocarbon
PAHs present in the environment are mainly natural and artificial sources.
1, natural source
(1) biosynthetic products of certain bacteria, algae and plants;
(2) wildfires and volcanic eruptions from forests and grasslands;
(3) PAHs emanating from fossil fuels, lignin, and sediments are the products of biodegradation and re-synthesis in the long-term geological age.
2, human origin
(1) Waste incineration and flue gas (including automobile exhaust) from incomplete combustion of chemical fuels;
(2) Factories (especially coking, refinery, gas plants).
(3) PAHs in water are mainly derived from industrial waste water, atmospheric drop, runoff on the surface of the asphalt road and the leaching flow of contaminated soil. Compared with groundwater and lake water, the river is more susceptible to pollution, which is mostly adsorbed on the suspended particles, only a small amount of dissolved state.
(4) indoor PAHs are derived from heating, cooking and smoking, etc., caused by incomplete combustion of hydrocarbons. In particular, there have been reports of more than 300 PAHs detected from cigarettes.
Physical and Chemical Properties of Polycyclic Aromatic Hydrocarbon
PAHs is a class of two or more than two benzene ring connected from the hydrocarbons, including naphthalene, anthracene, phenanthrene, pyrene and other 150 kinds can be divided into aromatic fused ring and aromatic non-fused ring.
PAHs water solubility is poor, fat-soluble strong, can be accumulated in the body. Can be dissolved in acetone, benzene, dichloromethane and other organic solvents.
Distribution of Polycyclic Aromatic Hydrocarbon
It was found that the content of low-cyclic PAHs in the gas phase was relatively high, while the high-ring PAHs were mainly adsorbed in the form of respirable particulate matter. The PAHs of the five rings and above are mainly adsorbed on the particles, and the PAHs of the two to four rings are distributed in the gas phase and the solid phase.
Human beings in the industrial and agricultural production, transportation and daily life in the extensive use of coal, oil, gasoline, wood and other fuels, can produce polycyclic aromatic hydrocarbon pollution. The amount of benzo [α] pyrene discharged per kilogram of fuel is about 67 to 137 mg of coal, 61 to 125 mg of wood, 40 to 68 mg of crude oil and 12 to 50.4 mg of gasoline. Therefore, the human environment such as the atmosphere, soil and water are different degrees containing benzo [α] pyrene and other polycyclic aromatic hydrocarbon. Polycyclic aromatic hydrocarbon in the atmosphere of pollution for its direct access to food - fall on vegetables, fruits, grains and open storage of food surface to create the conditions. Edible plants can also be aggregated from soils and irrigation water contaminated with PAHs. Polycyclic aromatic hydrocarbon (PAHs) contaminated water can be transferred to the human body through seaweed, crustaceans, molluscs and fish. May gather in the human body.