CFC-11 and you may CFC-113 had been entirely degraded inside eight hundred days and you can CFC-twelve displayed very little destruction more almost a lot of weeks

Profile 5 Density out-of CFC-eleven, CFC-twelve and you may CFC-113 inside the close ampoules out-of Withlacoochee River-water of south-eastern Georgia exhibiting degradation out of CFC-eleven and you may CFC-113 and obvious balance of CFC-12 (off Plummer et al., 1998b).

CFCs were not degraded within the ampoules of the river water kept below white at room temperature. Development of algae try present in these types of ampoules hence probably suffered cardio conditions (Plummer ainsi que al., 1998b).

Create mais aussi al. (1995) presented almost done destruction from CFC-11 and you can balances regarding CFC-a dozen inside the an excellent sulphate-reducing mud aquifer near Sturgeon Drops, Ontario, Canada. Around the fresh groundwater years centered on CFC-twelve decided well towards observed depth of your mid-sixties step 3 H bomb top. Significantly less than marine, sulphate-cutting requirements for the a great Norwegian fjord, Shapiro mais aussi al. (1997) discover rapid degradation out of CFC-11, and, inside the concerns of your own dimensions, CFC-twelve degradation could not was basically more than 1/600 regarding CFC-eleven. The 50 % of-lifestyle for CFC-11 degradation during the sulphate-reducing, organic steeped seawater was 0.1 ± 0.02 years and you will more smaller than you to discover because of the Create mais aussi al. (1995) from 0.9 to just ages.

Oster (1996) stated degradation off CFC-11 and you will CFC-12 in different (more than likely methanogenic, but essentially unspecified) anoxic environments, having rate out of CFC-11 degradation up to 10-bend that CFC-12

The presence of sulphate (and nitrate) in anaerobic environments slows the rates of dehalogenation reactions (Mohn and Tiedje, 1992; Sylvestre et al., 1997) by competing with highly halogenated aliphatic compounds as terminal electron acceptors. Inhibition of dehalogenation by sulphate may explain the persistence of CFC-12 in sulphate-reducing environments (as in Cook et al., 1995, Shapiro et al., 1997, and Plummer et al., 1998a,b) where dissolved sulphate is still present, and more rapid degradation of CFC-12 in methanogenic environments (Deipser and Stegmann, 1997; Oster et al., 1996) where sulphate concentrations are usually very low. Parks et al. (1995) reported complete removal of CFC-11 and CFC-12 under methanogenic conditions in the Memphis (sand) aquifer, south-west Tennessee (1.3 mg L -1 CH4, 7.3 mg L -1 SO4 2- , 5.3 mg L -1 Fe 2+ ). The measured tritium activity of 13.8 TU indicated post-bomb water that would otherwise contain easily measurable concentrations of CFCs. Shapiro et al. (1998) also found significant degradation of CFC-11 and CFC-12 under methanogenic conditions in a buried-valley aquifer near Dayton, Ohio. Fluvial and glacial drift deposits often contain particulate organic carbon and are low in sulphate. Such environments are usually methanogenic, and degradation of CFCs appears to be rapid.

Inside the pure surroundings the latest electron donor can be some kind of reduced carbon dioxide instance mixed organic carbon, lignite, or some other particular particulate natural carbon provided on the deposit otherwise water line. These days it is impossible to compare natural costs out-of degradation from one ecosystem otherwise laboratory reactor to a different on account of variability in lots of items in addition to abundance and range out-of mini-organisms, supply of substrate, all-natural composition, and you will presence out of it is possible to inhibitors.


Like microbial degradation, sorption is another process that can remove CFCs from groundwater, leaving the impression of apparently older age and lower groundwater velocities. Cook et al. (1995) observed uptake of CFC-113 relative to CFC-12 and 3 H at the Sturgeon Falls site, Ontario, Canada. The vertical profiles of CFC-12 and tritium could be modelled with a recharge rate of approximately 130 mm yr -1 and were apparently not affected by sorption or degradation. The agreement in transport of CFC-12 and 3 H was so strong that, if sorption of CFC-12 were occurring, the solid-liquid partition coefficient, Kd, must be less than 0.03 (retardation factor 3 H at Sturgeon Falls. Most of the uptake of CFC-113 occurred in the aerobic upper 4 m of the water column, suggesting sorption of CFC-113, rather than microbial degradation (Cook et al., 1995). The CFC-113 profile indicates a Kd value of 0.09-0.14 (retardation factor 1.4-1.7) for CFC-113 in the sand aquifer, which contained, on average, 0.03% organic carbon.