Benzo pyrene, chlorination

Aerobic, Anaerobic, and Combined Systems. The vast majority of in situ bioremediations ate conducted under aerobic conditions because most organics can be degraded aerobically and more rapidly than under anaerobic conditions. Some synthetic chemicals are highly resistant to aerobic biodegradation, such as highly oxidized, chlorinated hydrocarbons and polynuclear aromatic hydrocarbons (PAHs). Examples of such compounds are tetrachloroethylene, TCE, benzo(a)pyrene [50-32-8] PCBs, and pesticides. 

When benzo[a]pyrene adsorbed from the vapor phase onto coal fly ash, silica, and alumina was exposed to nitrogen dioxide, no reaction occurred. However, in the presence of nitric acid, nitrated compounds were produced (Yokley et al, 1985). Chlorination of benzo [a] pyrene in polluted humus poor lake water gave ll,12-dichlorobenzo[a]pyrene and 1,11,12-, 3,11,12- or 3,6,11-... 

Polycyclic aromatic hydrocarbons (PAH), which are ubiquitous in the environment, including surface waters, undergo facile chlorination by hypochlorite when dissolved in humus-poor water to give a suite of chlorinated PAH (1660). It is therefore conceivable that this chlorination can occur under natural conditions, but this is yet to be determined. Another new possible source of natural chlorinated PAH is the reported in vitro reaction of benzo [a pyrene diol epoxide, the ultimate carcinogen of benzo aIpyrene with chloride ion to give chlorohydrin DDD, which has been isolated and identified as an intermediate en route to a benzol a pyrene-DN A adduct (1661). However, DDD is not considered to be a natural compound at this time. 

PAHs in water can be chemically oxidized by chlorination and ozonation. A high efficiency of PAH degradation from chlorination has been reported by Harrison et al. (1976a, 1976b) for both laboratory and waste-water treatment plant conditions. Pyrene was the most rapidly degraded PAH. Benz[a]anthracene, benzo[a]pyrene, and perylene were also highly degraded. 

In water, ozonation is generally slower and less efficient than chlorination in degrading PAHs (Neff 1979). Reaction pathways for ozonation of some PAHs include benz[a]anthracene to 7,12-quinone benzo[a]pyrene to 3,6-, 1,6-, and 4.5-diones and fluorene to fluorenone (NAS 1972). 

For the chlorinated benzenes, a very similar distribution within the sediment core is observed as for some PAHs, e.g. benzo[a]pyrene. An elevated large-scale industrial activity related to these compounds can be deduced for the time between 1947 and 1955. We attribute the decrease in contamination towards the top layers to a reduction of emissions as a result of more efficient sewage treatment plants (Fig. 1A,B) as well as a modified array of products. The concentration profile of HCB (Fig. 6C) and all lower chlorinated benzenes (Tab. 2) suggests the dominance of industrial sources responsible for the contamination as contrasted to agricultural emission derived from pesticide usage. It should be noted that the contamination level of 1,4-dichlorobenzene was elevated in the time period between 1975 and 1980, comparable with concentration levels determined in Rhine river sediments 1982/83. The extensive use of 1,4-dichlorobenzene as an odorous ingredient of toilet cleaners contributed additionally to the contamination via sewage effluents (LWA, 1987/1989). 

To prevent oxidation, either ascorbic acid or sodium thiosulfate is often added to samples to remove free chlorine that could otherwise form trichloro-methane. Polyaromatic hydrocarbons (PAHs), in particular benzo[a]-pyrene, are unstable in chlorinated water and sodium thiosulfate is added to preserve the analytes from degradation by chlorine. To ensure stability of the PAH analytes, the water sample is also acidified, again showing that often a single preservative is not always effective for some analytes. 

HC 1 <1 ppm or <0.1 mg/m or A1/A2 carcinogens or sensitizers Acrylamide, arsine, benzene, benzo[a]pyrene, bis(chloromethyl) ether, bromine, carbon disulfide, chlorine, diborane, fluorine,lithium hydride, methyhsocyanate, nitrogen dioxide, picric acid, toluene diisocyanate, 2,4,6-trinitrotoluene (TNT), tri-ocresylphosphate, vinyl chloride... 

Akcha F, Izuel C, Venier P, Budzinski H, Burgeot T, Narbonne JF (2000) Enzymatic biomarker measurement and study of DNA adduct formation in benzo[a]pyrene-contaminated mussels, Mytilus galloprovincialis. Aquat Toxicol 49 269-287 Amin OA, Comoglio LI, Sericano JL (2011) Polynuclear aromatic and chlorinated hydrocarbons in mussels from the coastal zone of Ushuaia, Tierra Del Fuego, Argentina. Environ Toxicol Chem 30 521-529... 

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