Profile 5 Levels from CFC-11, CFC-twelve and you will CFC-113 when you look at the closed ampoules from Withlacoochee River water from southern area-eastern Georgia appearing destruction away from CFC-eleven and you can CFC-113 and you will noticeable stability regarding CFC-twelve (out of Plummer et al., 1998b).

CFCs weren't degraded when you look at the ampoules of the river-water stored under light at room temperature. Growth of alga are seen in these ampoules hence probably sustained cardiovascular requirements (Plummer et al., 1998b).

Make et al. (1995) shown almost complete destruction regarding CFC-eleven and you will balance of CFC-a dozen within the good sulphate-reducing sand aquifer close Sturgeon Falls, Ontario, Canada. Around the brand new groundwater ages based on CFC-twelve agreed really into noticed depth of one's mid-1960s 3 H bomb peak. Significantly less than aquatic, sulphate-reducing conditions from inside the a good Norwegian fjord, Shapiro ainsi que al. (1997) receive fast degradation out-of CFC-11, and you may, in uncertainties of proportions, CFC-several destruction couldn't were more than step 1/600 that CFC-eleven. This new 1 / 2 of-lifestyle getting CFC-11 destruction when you look at the sulphate-reducing, organic steeped seawater was 0.step one ± 0.02 decades and you may much more smaller than one found by Get ready et al. (1995) away from 0.9 to a single.seven ages.

Oster (1996) stated destruction of CFC-eleven and you will CFC-twelve in various (almost certainly methanogenic, however, fundamentally unspecified) anoxic surroundings, with speed away from CFC-11 destruction whenever ten-fold compared to CFC-a dozen

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.

Within the sheer surroundings the latest electron donor can be some type of faster carbon dioxide for example demolished all-natural carbon dioxide, lignite, or some other style of particulate natural carbon incorporated throughout the sediment or liquids column. It is currently extremely hard to compare natural costs regarding degradation from environment or research reactor to some other due to variability a number of points plus abundance and you can range regarding mini-bacteria, supply of substrate, organic structure, and exposure away from it is possible 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, 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, 0.03% organic carbon.