There isn’t any proof getting cardiovascular destruction regarding CFCs for the groundwater

Bacterial degradation

Short loss out of CFC-11 and you will CFC-a dozen have been understood inside the cardio microcosm studies with autoclaved sediment and you will peat (Lovley and you will Woodward, 1992; Bauer and you can Yavitt, 1996), however, it uptake was because of sorption (Bauer and Yavitt, 1996). In contrast, CFC-eleven, CFC-several and you will CFC-113 could all be degraded under anaerobic criteria.

A variety of redox criteria, away from aerobic so you’re able to anaerobic sulphate cutting and you can methanogenic influenced your neighborhood 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., 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 bu web sitesinde bir gГ¶z atД±n 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), created by addition of compost, CFC-11 was degraded to HCFC-21 at an average rate of 0.3 mg/m 3 _{topic 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 _{point 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 _{matter 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 demonstrated the fresh disappearance of CFCs when you look at the absolute environment or in laboratory experiments which have natural information (Lovley and Woodward, 1992; Denovan and you can String, 1992; Semprini et al., 1990, 1992; Katz et al., 1995; Create mais aussi al., 1995; Bullister and you will Lee, 1995; Oster et al., 1996; Shapiro ainsi que al., 1997, 1998; Plummer et al., 1998a,b). The outcomes out of community observations are generally into the arrangement towards the research observations. Below cardiovascular criteria, of numerous groundwater research has demonstrated agreement in the visible ages centered on CFC-11, CFC-several and you can CFC-113 (Dunkle et al., 1993; Katz et al., 1995; Szabo et al., 1996; Plummer et al., 1998b), that’s then proof of shortage of destruction from CFCs lower than aerobic requirements.

CFC degradation might be perhaps not identified inside groundwater up to redox requirements reach sulphate cures. Using biostimulation having acetate, Semprini mais aussi al. (1990) observed consumption from CFC-eleven and you can CFC-113 during the an anaerobic confined aquifer you to began immediately following denitrification try complete. Katz mais aussi al. (1995) receive CFC-eleven apparent many years that have been 6-twelve many years avove the age of those people considering CFC-a dozen during the groundwater in the process of sulphate protection and methanogenesis.

Plummer et al. (1998a, b) mapped density away from CFC-11, CFC-12 and you can CFC-113 into the groundwater from the Higher Floridan aquifer into the southern Georgia, Us more than an excellent 650 km dos city impacted by seepage out-of DOC-steeped river water. CFC-11 and you can CFC-several visible ages was within the arrangement when you look at the cardiovascular infiltration drinking water, actually near the constraints of identification of these two compounds. CFC-eleven and you will CFC-113 was basically almost absent throughout anaerobic components of the aquifer one had been impacted by seepage out of Doctor-steeped river water, while CFC-twelve carried on while in the. The fresh new apparent CFC-twelve and you may 3 H/ 3 The guy age of the newest river small fraction regarding combinations that have dated groundwater consented contained in this 5 years or most readily useful in the seven regarding nine co-dated water trials.