Contour 5 Density regarding CFC-eleven, CFC-12 and CFC-113 inside the shut ampoules off Withlacoochee River-water away from south-east Georgia demonstrating destruction out-of CFC-11 and you can CFC-113 and you will visible balances regarding CFC-a dozen (off Plummer mais aussi al., 1998b).

CFCs just weren’t degraded in the ampoules of your own river-water stored under light in the room-temperature. Growth of algae are present in these types of ampoules and therefore probably suffered aerobic criteria (Plummer ainsi que al., 1998b).

Plan et al. (1995) demonstrated nearly over degradation away from CFC-eleven and you can balances out of CFC-a dozen inside the a beneficial sulphate-reducing mud aquifer close Sturgeon Drops, Ontario, Canada. There the fresh groundwater decades predicated on CFC-twelve decided well on the noticed depth of your own middle-1960s 3 H bomb height. Not as much as marine, sulphate-reducing requirements inside a good Norwegian fjord, Shapiro et al. (1997) found rapid degradation regarding CFC-eleven, and you can, inside uncertainties of your own proportions, CFC-twelve degradation cannot was in fact more than step 1/600 compared to CFC-eleven. The brand new 50 % of-life having CFC-eleven degradation for the sulphate-cutting, natural rich seawater try 0.step 1 ± 0.02 decades and you can more smaller compared to you to definitely discovered of the Get ready ainsi que al. (1995) out of 0.nine to just one.eight years.

Oster (1996) said degradation from CFC-eleven and you can CFC-12 in various (most likely methanogenic, however, essentially unspecified) anoxic surroundings, which have price out-of CFC-eleven degradation as much as 10-flex 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.

During the pure environments the fresh new electron donor is oftentimes some form of quicker carbon such as demolished natural carbon dioxide, lignite, or another version of particulate organic carbon dioxide included regarding the deposit otherwise h2o line. These days it is difficult to compare pure pricing of destruction from one ecosystem otherwise lab reactor to some other because of variability a number of points including wealth and you will range regarding micro-bacteria, supply of substrate, normal constitution, and you can exposure away from you can 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, K_d, 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 K_d value of 0.09-0.14 (retardation factor 1.4-1.7) for CFC-113 in the sand aquifer, which contained, on average, 0 aisle Internecie.03% organic carbon.