There’s absolutely no research to possess aerobic degradation out of CFCs when you look at the groundwater

Microbial degradation

Quick loss off CFC-eleven and you may CFC-several was indeed observed when you look at the cardiovascular microcosm tests having autoclaved sediment and you may peat (Lovley and you can Woodward, 1992; Bauer and Yavitt, 1996), but which consumption may have been due to sorption (Bauer and you will Yavitt, 1996). However, CFC-11, CFC-a dozen and you can CFC-113 could all be degraded lower than anaerobic criteria.

A wide range of redox conditions, of cardiovascular to help you anaerobic sulphate reducing and you will methanogenic influenced your regional 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., 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), created by addition of compost, CFC-11 was degraded to HCFC-21 at an average rate of 0.3 mg/m 3 _{situation 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 _{thing 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 _{procedure 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.

Multiple studies have showed the latest disappearance regarding CFCs from inside the pure surroundings or in lab tests having natural product (Lovley and Woodward, 1992; Denovan and String, 1992; Semprini et al., https://datingmentor.org/ashley-madison-review/ 1990, 1992; Katz ainsi que al., 1995; Create ainsi que al., 1995; Bullister and you can Lee, 1995; Oster et al., 1996; Shapiro mais aussi al., 1997, 1998; Plummer mais aussi al., 1998a,b). The outcome off occupation observations are usually in contract to the laboratory observations. Significantly less than cardiovascular requirements, many groundwater research has showed contract in visible age centered on CFC-11, CFC-twelve and you may CFC-113 (Dunkle ainsi que al., 1993; Katz et al., 1995; Szabo ainsi que al., 1996; Plummer ainsi que al., 1998b), which is next proof of diminished degradation out-of CFCs significantly less than cardiovascular conditions.

CFC degradation can often be perhaps not observed into the groundwater until redox requirements started to sulphate protection. Playing with biostimulation that have acetate, Semprini mais aussi al. (1990) observed use of CFC-eleven and you may CFC-113 from inside the a keen anaerobic restricted aquifer one to first started shortly after denitrification was over. Katz mais aussi al. (1995) receive CFC-eleven visible ages which were 6-a dozen years more than those centered on CFC-12 when you look at the groundwater undergoing sulphate avoidance and methanogenesis.

Plummer et al. (1998a, b) mapped levels of CFC-eleven, CFC-several and you can CFC-113 for the groundwater on Higher Floridan aquifer in the southern area Georgia, United states of america over an effective 650 kilometres 2 area impacted by seepage from DOC-steeped river-water. CFC-11 and CFC-a dozen obvious ages were inside the arrangement inside aerobic infiltration h2o, also around the restrictions regarding recognition of the two substances. CFC-eleven and you may CFC-113 have been nearly absent throughout the anaerobic components of the aquifer that was basically affected by seepage of Doctor-rich river-water, if you’re CFC-12 continued through the. The new obvious CFC-several and you will step 3 H/ step three He period of the latest river small fraction about blends that have old groundwater assented contained in this five years otherwise greatest from inside the 7 regarding 9 co-old h2o trials.