CFC-eleven and you can CFC-113 had been completely degraded within this cuatro00 weeks and you can CFC-twelve demonstrated hardly any destruction more almost a lot of weeks

Figure 5 Concentrations out of CFC-eleven, CFC-several and you may CFC-113 inside close ampoules away from Withlacoochee River water out-of southern-east Georgia exhibiting degradation away from CFC-11 and you may CFC-113 and visible balance from CFC-several (regarding Plummer ainsi que al., 1998b).

CFCs were not degraded when you look at the ampoules of your own river water stored lower than light in the room-temperature. Growth of algae is actually noticed in this type of ampoules and this most likely sustained cardio criteria (Plummer et al., 1998b).

Get ready ainsi que al. (1995) presented nearly over degradation from CFC-11 and you will balances of CFC-12 inside the a sulphate-reducing mud aquifer near Sturgeon Drops, Ontario, Canada. There the new groundwater many years based on CFC-twelve concurred really to the observed depth of the mid-sixties 3 H bomb level. Around marine, sulphate-reducing criteria inside a Norwegian fjord, Shapiro mais aussi al. (1997) located rapid destruction from CFC-11, and you can, in the uncertainties of the specifications, CFC-a dozen degradation could not had been more step one/600 that of CFC-eleven. The fresh new 1 / 2 of-life to own CFC-eleven degradation when you look at the sulphate-reducing, normal steeped seawater try 0.1 ± 0.02 decades and you will most smaller compared to you to receive because of the Make ainsi que al. (1995) off 0.9 to a single.seven decades.

Oster (1996) said destruction away from CFC-11 and you can CFC-12 in various (more than likely methanogenic, but essentially unspecified) anoxic surroundings, which have rate off CFC-eleven destruction everything 10-flex compared to 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.

For the natural environments brand new electron donor is frequently some form of faster carbon such as for example demolished normal carbon dioxide, lignite, or some other sorts of particulate natural carbon dioxide provided regarding the deposit or drinking water line. It is now impossible evaluate natural rates from destruction from 1 ecosystem otherwise laboratory reactor to another due to variability in several facts also variety and you will range off micro-bacteria, method of getting substrate, all-natural composition, and visibility away from you are able to inhibitors.

Sorption

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.