Profile 5 Levels away from CFC-eleven, CFC-a dozen and CFC-113 inside sealed ampoules from Withlacoochee River-water off south-east Georgia demonstrating destruction away from CFC-11 and you will CFC-113 and obvious stability away from CFC-12 (from Plummer ainsi que al., 1998b).
CFCs weren’t degraded for the ampoules of your river water held around white at the room temperature. Growth of algae are present in these ampoules and that most likely sustained cardio criteria (Plummer mais aussi al., 1998b).
Create mais aussi al. (1995) shown almost done destruction out-of CFC-11 and you will stability out of CFC-12 in the a sulphate-reducing sand aquifer close Sturgeon Falls, Ontario, Canada. Indeed there this new groundwater decades based on CFC-twelve agreed better into seen breadth of middle-sixties 3 H bomb height. Around marine, sulphate-reducing criteria inside a great Norwegian fjord, Shapiro et al. (1997) located quick destruction out-of CFC-eleven, and, in concerns of the proportions, CFC-a dozen destruction couldn’t have been more step one/600 regarding CFC-eleven. The newest half-lifetime having CFC-eleven destruction in sulphate-cutting, natural steeped seawater is actually 0.1 ± 0.02 years and a lot more smaller than one discover by Create ainsi que al. (1995) of 0.nine to at least one.7 years.
Oster (1996) stated destruction off CFC-11 and CFC-twelve in different (more than likely methanogenic, however, generally unspecified) anoxic environments, that have rate regarding CFC-eleven degradation approximately ten-fold that CFC-twelve
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 natural environments this new electron donor can often be some sort of shorter carbon dioxide such as for instance mixed organic carbon, lignite, or some other kind of particulate organic carbon dioxide incorporated from the deposit otherwise water line. These days it is impossible examine natural rates away from destruction from just one environment or lab reactor to a different on account of variability in several situations as hookup near me Adelaide well as wealth and diversity of micro-organisms, supply of substrate, all-natural composition, and you may exposure of 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.