Quick loss out of CFC-11 and you will CFC-twelve was basically seen inside the cardio microcosm experiments having autoclaved sediment and you can peat (Lovley and Woodward, 1992; Bauer and you can Yavitt, 1996), however, it uptake might have been because of sorption (Bauer and you will Yavitt, 1996). Alternatively, CFC-11, CFC-several and you can CFC-113 can all be degraded significantly less than anaerobic requirements.
Numerous redox criteria, regarding cardio to help you anaerobic sulphate reducing and you can methanogenic swayed your regional groundwater system
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., 1994; 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 (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) African local dating, created by addition of compost, CFC-11 was degraded to HCFC-21 at an average rate of 0.3 mg/m 3 matter 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 issue 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 thing 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 showed the fresh disappearance regarding CFCs when you look at the natural environments or even in laboratory tests with natural materials (Lovley and you can Woodward, 1992; Denovan and you can Strand, 1992; Semprini mais aussi al., 1990, 1992; Katz mais aussi al., 1995; Create et al., 1995; Bullister and you can Lee, 1995; Oster mais aussi al., 1996; Shapiro et al., 1997, 1998; Plummer ainsi que al., 1998a,b). The outcome regarding industry findings are generally for the arrangement with the research findings. Less than aerobic conditions, of numerous groundwater research has showed contract within the visible age centered on CFC-eleven, CFC-twelve and you will CFC-113 (Dunkle mais aussi al., 1993; Katz et al., 1995; Szabo et al., 1996; Plummer mais aussi al., 1998b), which is next proof of lack of destruction away from CFCs less than cardiovascular standards.
CFC degradation might be maybe not perceived within the groundwater up to redox standards come to sulphate prevention. Having fun with biostimulation which have acetate, Semprini mais aussi al. (1990) seen consumption out of CFC-eleven and you will CFC-113 inside the an enthusiastic anaerobic confined aquifer you to definitely first started immediately following denitrification try done. Katz mais aussi al. (1995) located CFC-11 apparent many years which were 6-several years more than those according to CFC-several for the groundwater undergoing sulphate avoidance and you can methanogenesis.
Plummer mais aussi al. (1998a, b) mapped levels regarding CFC-11, CFC-12 and you may CFC-113 inside the groundwater throughout the Top Floridan aquifer in the southern Georgia, United states more than a great 650 km 2 urban area impacted by seepage of DOC-rich river water. CFC-11 and CFC-a dozen noticeable decades was in fact into the agreement inside aerobic infiltration liquids, also near the limits out of recognition of the two substances. CFC-eleven and you will CFC-113 were almost absent throughout anaerobic components of new aquifer one to were affected by seepage out-of Doc-steeped river water, when you are CFC-12 continuous throughout. The brand new apparent CFC-several and you will step three H/ 3 He age the fresh river small fraction on the combinations which have dated groundwater decided within 5 years otherwise finest inside the eight off 9 co-old drinking water examples.