The Displacement of PCBs in Environment ——The PCBs pollution status of Guangzhou City ES0710182009 Wang Jiao

What are PCBs PCBs are a class of chlorinated aromatics, formed with benzene as raw materials and metal as catalyst at high temperature, its molecular formula being (C10H10) Cln. There are a total of 209 congeners according to the number and different positions of chlorine atoms to be replaced. PCBs are often used in heat exchange agent, lubricants, transformers and capacitors, and widely used in power industry, plastics processing industry, chemicals and printing fields. PCBs are the first to be included in the POPs, and a member of the Dirty Dozen.

The Characteristics of PCBs Persistence: with a strong resistance to the biological metabolism, photodegradation and chemical decomposition; Long-term residue: hydrophobic lipophilic, accumulated in fat, reaching the toxic concentrations through amplification in the food chain; Semi-volatile: long-distance displacement and deposition in the atmosphere;

PCBs hazards Induce lesions and cancer: Japan and Taiwan encountered with the outbreak of rice bran oil events in 1968 and 1979 respectively; Affect the breeding of mammals and birds; Cause water and air pollution;

Rice Bran Oil Event PCBs Rice bran oil 米糠油事件:Rice Bran Oil Event

The Displacement of PCBs 0.6% reacts with HO then disappear Rainwater, (wet) deposition Exhaust gas Effluent Volatilization Stockpile Rainwater, (wet) deposition Deposition Volatilization（weak） Biodegradation Reversible adsorption

The Content of PCBs Atmosphere: 307.2 ~ 2720.8pg/m3; mid-level Water sediments (Pearl River): 485ng/g; Water: 2.3ng/l; Soil: 6 ~ 151g/kg; Tibet: 0.625 ~ 3.501g/kg

In 1977 all countries successively suspended its production, and by 1980, world’s total production amount of PCBs was one million tons; The production of PCBs in China started in 1965, and ended in the 1980s, the estimated total output being nearly 10.4 tons over the years; The total amount of PCBs currently existing in the world's oceans, soil and atmosphere appears to be 25 to 30 tons.

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