Tetrachloroethylene groundwater

Groundwater Industrial contamination of ground water reserves Reduction of total organic halogens (TOX) and adsorbable organic halogens (AOX) including chloroform, tetrachloroethylene, and trichloroethylene... 

Biotransformation was also strongly indicated as a factor in the degradation of trichloroethylene in a case of soil and groundwater pollution (Milde et al. 1988). The only ethylenes at the point source of pollution were tetrachloroethylene and trichloroethylene however, substantial amounts of known metabolites of these two compounds (dichloroethylene, vinyl chloride, and ethylene) were found at points far from the source. Data from laboratory studies by the same group supported the study authors contention that degradation was due... 

Hexachloroethane is also relatively resistant to degradation in the aquatic environment. No hydrolysis of hexachloroethane in water was observed after 11 days at 85 C at 3 pH levels (3, 7, and 11) (Ellington et al. 1987). However, hexachloroethane may be reduced in aquatic systems in the presence of sulfide and ferrous ions (Kriegman-King and Reinhard 1991). The transformation rate of hexachloroethane to tetrachloroethylene under simulated groundwater conditions at 50 C was evaluated without ferrous or sulfide ions, with minerals (biotite and vermiculite) providing ferrous ions, and with minerals and sulfide ions. Reported half-lives for hexachloroethane were 365 days for hexachloroethane alone, 57-190 days with minerals present, and 0.45-0.65 days in the presence of both minerals and sulfide. 

A half-life of about 40 days was reported for hexachloroethane in an unconfined sand aquifer (Criddle et al. 1986). Laboratory studies with wastewater microflora cultures and aquifer material provided evidence for microbial reduction of hexachloroethane to tetrachloroethylene under aerobic conditions in this aquifer system (Criddle et al. 1986). In anaerobic groundwater, hexachloroethane reduction to pentachloroethane and tetrachloroethylene was found to occur only when the water was not poisoned with mercury chloride (Roberts et al. 1994). Pentachloroethane reduction to tetrachloroethylene occurred at a similar rate in both poisoned and unpoisoned water. From these results, Roberts et al. (1994) suggested that the reduction of hexachloroethane to tetrachloroethylene occurred via pentachloroethane. The first step, the production of pentachloroethane, was microbially mediated, while the production of tetrachloroethylene from pentachloroethane was an abiotic process. 

Criddle CS, McCarty PL, Elliott MC, et al. 1986. Reduction of hexachloroethane to tetrachloroethylene in groundwater. Ada, OK U.S. Environmental Protection Agency, Office of Research and Development. PB86-201324. 

In batch kinetic tests, Yan and Schwartz (1999) investigated the oxidative treatment of chlorinated ethylenes in groundwater using potassium permanganate. 1,1-Dichloroethylene reacted more quickly than cis- and /ra/ 5-l, 2-dichloroethylene, trichloroethylene, and tetrachloroethylene. The reaction rate decreased with an increasing number of chlorine substituents. The pseudo-first-order rate constant and half-life for oxidative degradation (mineralization) of 1,1-dichloroethyene were 2.38 x 10 Vsec and 4.9 min, respectively. 

Groundwater contaminated with other halogenated solvents can also be treated in aboveground reactors. Aerobic reactors are useful for those compounds that can support growth. Sequential anaerobic and aerobic reactors are capable of mineralizing tetrachloroethylene. 

Rao, H.V., and D.R. Brown. 1993. A physiologically based pharmacokinetic assessment of tetrachloroethylene in groundwater for a bathing and showering determination. Risk Anal. 13(l) 37-49. 

Tetrachloroethylene is used as a solvent. It is highly volatile and, for this reason, has been found only in groundwaters. Its odor threshold in water is 300 pg L and it is classified by the EPA as a probable human carcinogen (Group B2). 

Ozone-based AOPs are being used increasingly to treat landfill leachates. " They are also used for ground-water treatment to destroy trichloroethylene (TCE), tetrachloroethylene, and pentachlorophenol. In addition, they are used for groundwater remediation at Superfund sites in the United States to destroy volatile organic compounds and benzidines. Another application of ozone-based AOPs involves their use at U.S. ammunition plants to destroy explosives. ... 

Dermal absorption of fluazifop-butyl through rat and human skin (Ramsey etal., 1994) Tetrachloroethylene In groundwater for a bathing and showering scenario (Rao and Brown, 1993)... 

Tetrachloroethylene is a volatile organic compound that is widely distributed in the environment. It is released to the environment via industrial emissions, and it is released from building and consumer products. Releases are primarily to the atmosphere, but the compound is also released to surface water and land in sewage sludges and in other liquid and solid waste, where its high vapor pressure and Hemy s law constant usually result in its rapid volatilization to the atmosphere. Tetrachloroethylene has relatively low solubility in water and has medium-to-high mobility in soil, thus its residence time in surface environments is not expected to be more than a few days. However, it persists in the atmosphere for several months and may also persist in groundwater for several months or more. Because of its pervasiveness and ability to persist under eertain eonditions, the potential for human exposure may be substantial. It should be noted that the amount of tetrachloroethylene measured by chemical analysis is not necessarily the amount that is bioavailable. 

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