Atmospheric Lifetimes of Long-Lived Halogenated Species

Abstract

These repair systems distinguish template DNA from newly synthesized DNA by the new DNA's unmethylated state. Thus, these systems can resolve DNA mismatches in favor of the unmutated allele. Other mismatch repair systems are not methyldirected and are presumabiy error prone (45).

CO2 and SF6 as stratospheric age tracers: Consistency and the effect of mesospheric SF6‐loss

“…The transport of H2-rich mesospheric air into the stratosphere is likely to occur in winter at high latitudes during the diabatic This has an important implication for mean age determinations since SF6 is decomposed by UV absorption ()• < 125 nm) and electron reactions [Ravishankara et al, 1993;Morris et al, 1995] that become relevant only in the mesosphere. If a significant amount of SF6-depleted air were transported downward into the stratosphere, the mean age determined in stratospheric air samples could be significantly biased towards higher SF6-age values.…”

Dating young groundwater with sulfur hexafluoride: Natural and anthropogenic sources of sulfur hexafluoride

“…SF 6 is released to the atmosphere predominantly in the middle latitudes of the Northern Hemisphere and is subsequently incorporated into the hydrosphere. The SF 6 atmospheric mixing ratio has rapidly increased because of (1) the long lifetime in the atmosphere, with estimates of 1935 [Patra et al, 1997] to 3200 [Ravishankara et al, 1993] years, (2) the low solubility of the tracer in water [Ashton et al, 1968; Cosgrove and Walkey, 1981; Mroczek, 1997], (3) the apparent high stability in soils [Maiss and Brenninkmeijer, 1998], and (4) the lack of other significant natural sinks [Maiss and Brenninkmeijet, 1998]. The SF 6 atmospheric mixing ratio increased from 0.6 parts per trillion volume (pptv) in 1976 [Maiss and Brenninkmeijer, 1998] to more than 4 pptv in 1999.…”

The Role of Atmospheric Gases in Global Warming

“…The GWP of these two molecules is very high, SF 6 being slightly higher because its atmospheric lifetime, ca. 3200 a [8], is about four times greater than that of SF 5 CF 3 . However, the contribution of these two molecules to the overall greenhouse effect is still very small because their atmospheric concentrations, despite rising rapidly at the rate of ca.…”

“…The averaging process thus needs input from a 2− or 3−dimensional model of the atmosphere in order to supply values for n i . This is essentially a meterological, and not a chemical Many such studies have been made for SF 6 [8,12,13], and differences in the kinetic model (k i ) and the atmospheric distributions (n i ) from different climate or transport models account for the variety of atmospheric lifetimes that have been reported. The importance of both these factors has also been explored by Hall and Waugh [14].…”

“…One may therefore ask where the quoted lifetimes for SF 6 , CF 4 and SF 5 CF 3 of 3200, 50000 and 800 a, respectively, come from [8,11]. The lifetimes of such long-lived greenhouse gas can only be obtained from globally-averaged loss frequencies.…”