There isn’t any research to own cardio destruction off CFCs when you look at the groundwater

There isn’t any research to own cardio destruction off CFCs when you look at the groundwater

Microbial destruction

Short losses from CFC-eleven and you can CFC-twelve were perceived into the aerobic microcosm experiments that have autoclaved sediment and peat (Lovley and you will Woodward, 1992; Bauer and you can Yavitt, 1996), however, it uptake may have been on account of sorption (Bauer and you will Yavitt, 1996). Having said that, CFC-11, CFC-a dozen and you can CFC-113 could all be degraded significantly less than anaerobic criteria.

An array of redox requirements, out-of cardiovascular so you can anaerobic sulphate reducing and methanogenic swayed your local groundwater program

Recent interest in finding natural and synthetic biocatalytic systems that destroy chlorofluorocarbons has contributed research that significantly improves our understanding of microbial processes that degrade CFCs (Sonier et al., 199cuatro; Oremland et al., 1996; Bauer and Yavitt, 1996; Deipser and Stegmann, 1997; Sylvestre et al., 1997). CFCs are electron acceptors, as is nitrate, iron(III), sulphate and CO2 in groundwater. CFCs are degraded primarily by dechlorination reactions that produce hydrochlorofluorocarbons (HCFCs). For example, Sonier et al. (1994) demonstrated that reductive dechlorination of CFC-11 was nearly stoichiometric in the production of fluorodichloromethane (HCFC-21) under sulphate-reducing conditions. In a sulphate-reducing contaminant plume associated with an organic waste disposal site near Ottawa, Ontario, Canada, Lesage et al. (1990) found two dechlorination products seventhday adventist singles (1,2-Dichloro-1,2,2-trifluoroethane (CFC-123a), and chlorotrifluoroethene (CFC-113)), and one defluorination product (1,1,2-trichloro-1,2-difluoroethane (CFC-122a)) of CFC-113.

Deipser and Stegmann (1997) investigated the microbial degradation of CFCs in simulated landfill conditions. Under ‘acidphase’ conditions (pH 5.5, 70-90 volume % CO2, 10-30 volume % CH4), created by addition of compost, CFC-11 was degraded to HCFC-21 at an average rate of 0.3 mg/m 3 procedure vol./ hour , but CFC-12 and CFC-113 were hardly degraded. Under ‘methanephase’ conditions (pH 7, 40% CO2, 60% CH4), CFC-11 was again degraded to HCFC-21 with an average rate (11 mg/m 3 situation vol./ hour ) nearly 37-fold that observed under ‘acidphase’ conditions. CFC-12 and CFC-113 also decomposed under ‘methanephase’ conditions, both at an average rate of 0.7 mg/m 3 point vol./ hour . Therefore, under methanogenic conditions, Deipser and Stegmann (1997) found CFC-11 degradation to be nearly 16-fold that of CFC-12 and CFC-113. The degradation product of CFC-12, HCFC-22, was apparently stable under the methanic conditions. For analytical reasons, Deipser and Stegmann (1997) were not able to identify the degradation product(s) of CFC-113.

Several studies have shown this new disappearance out-of CFCs in the absolute environment or perhaps in research tests with absolute information (Lovley and you will Woodward, 1992; Denovan and you can Strand, 1992; Semprini ainsi que al., 1990, 1992; Katz et al., 1995; Get ready mais aussi al., 1995; Bullister and you may Lee, 1995; Oster mais aussi al., 1996; Shapiro ainsi que al., 1997, 1998; Plummer et al., 1998a,b). The outcome off job observations are often for the agreement into laboratory observations. Less than aerobic requirements, of a lot groundwater studies have exhibited arrangement from inside the visible ages considering CFC-eleven, CFC-twelve and you may CFC-113 (Dunkle ainsi que al., 1993; Katz ainsi que al., 1995; Szabo mais aussi al., 1996; Plummer ainsi que al., 1998b), which is subsequent proof of insufficient degradation of CFCs significantly less than cardio conditions.

CFC degradation is often not recognized when you look at the groundwater up until redox requirements arrived at sulphate avoidance. Using biostimulation which have acetate, Semprini mais aussi al. (1990) noticed use off CFC-eleven and you can CFC-113 into the an anaerobic confined aquifer you to first started shortly after denitrification is complete. Katz ainsi que al. (1995) found CFC-eleven apparent decades that have been six-12 ages older than men and women based on CFC-12 during the groundwater undergoing sulphate avoidance and you will methanogenesis.

Plummer mais aussi al. (1998a, b) mapped concentrations from CFC-eleven, CFC-12 and you will CFC-113 during the groundwater on the Upper Floridan aquifer in southern area Georgia, United states of america more than a great 650 km dos urban area influenced by seepage from DOC-steeped river-water. CFC-11 and CFC-twelve visible ages was basically into the contract in cardiovascular infiltration h2o, also around the constraints regarding detection of the two substances. CFC-11 and you may CFC-113 was in fact nearly absent during anaerobic parts of the new aquifer that was basically influenced by seepage of Doc-steeped river water, whenever you are CFC-twelve continuing throughout. The new apparent CFC-several and you may step 3 H/ step three He age the fresh new lake small fraction regarding the mixtures with old groundwater concurred inside 5 years otherwise ideal for the seven of nine co-dated liquids samples.



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