Atmosphere losses

American Petroleum Institute (API), Bulletin 2521. Use of Pressure-Vacuum Vent Valves for Atmospheric Loss. API Washington, D.C., 1993. 

The rate constants for the reaction of l,2-dibromo-3-chloropropane with ozone and OH radicals in the atmosphere at 296 K are <5.4 x 10 ° and 4.4 x lO cm /molecule-sec (Tuazon et al., 1986). The smaller rate constant for the reaction with ozone indicates that the reaction with ozone is not an important atmospheric loss of l,2-dibromo-3-chloropropane. The calculated photolytic half-life and tropospheric lifetime for the reaction with OH radicals in the atmosphere are 36 and 55 d, respectively. The compound l-bromo-3-chloropropan-2-one was tentatively identified as a product of the reaction of l,2-dibromo-3-chloropropane with OH radicals. 

While the F02 reactions with NO and NOz are moderately fast, with room temperature rate constants of the order of 10 12 and 10 13 cm3 molecule-1 s-1, respectively (Sehested et al., 1994 Li et al., 1995b), the concentrations of NO and NOz are sufficiently small that they do not represent major atmospheric loss processes for F02. It is interesting, however, that the F02 + NO reaction proceeds by transfer of the F atom to form FNO (which photolyzes) rather than by transfer of an oxygen atom, which is more common for... 

Since repeated measurements show no significant temporal change of M,- with time, we evaluate Eq. 21-6 for steady-state (dC, Idt = 0). Furthermore, since Cia / Kia/Vl < 1.4 x 10 8mol m 3, we neglect the last term on the right-hand side of Eq. 21-6. Solving for the atmospheric loss term yields ... 

In addition to photolysis (Chapter 15) and chemical reactions (see the next section), wet and dry deposition also can remove gas- and particle-phase chemical compounds from the troposphere (Eisenreich et al., 1981 Bidleman, 1988). Thus to completely characterize the atmospheric loss processes and overall lifetime of a chemical, we must understand its atmospheric lifetime due to dry and/or wet deposition. Wet deposition refers to the removal of the chemical (or particle-associated chemical) from the atmosphere by precipitation of rain, fog, or snow to earth s surface). Dry deposition refers to the removal of the chemical or particle-assodated chemical from the atmosphere to the Earth s surface by diffusion and / or sedimentation. 

Thirdly, for some species (most notably CO2) there are removal processes in which the species equilibrates with large reservoirs. Atmospheric CO2 equilibrates with CO2 dissolved in the upper layers of the oceans and with the terrestrial biota within approximately 4 years [17]. However, the majority of the CO2 in these reservoirs is returned to the atmosphere within a few years. It is only the relatively small fraction of CO2 that is transferred to the deep ocean that can be considered to be permanently lost from the atmosphere. Loss of CO2 from the atmosphere cannot be represented by a simple exponential decay but is instead is a complex function [18,19]. As a guide the atmospheric lifetime of CO2 is approximately 50-200 years [17]. 

The primary tropospheric oxidants are OH, O3, and NO3, with "OH and O3 reactions with hydrocarbons dominating primarily during daytime hours, and NO3 reactions dominating at night. Rate constants for the reactions of many different aromatic compounds with each of the aforementioned oxidants have been determined through laboratory experiments [16]. The rate constant data as well as atmospheric lifetimes for the reactions of toluene, m-xylene, p-xylene, m-ethyl-toluene, and 1,2,4-trimethylbenzene appear in Table 14.1. Only these particular aromatic compoimds will be discussed in this review paper, since much of the computational chemistry efforts have focused on these compounds. When considering typical atmospheric concentrations of the major atmospheric oxidants, OH, O3, and NO3 of 1.5 x 10, 7 x 10, and 4.8 x 10, molecules cm , respectively [17], combined with the rate constants, it is clear that the major atmospheric loss process for these selected aromatic compounds is reaction with the hydroxyl... 

Measurements of atmospheric water vapor on Mars have found D/H values —5 times that of the Earth and have been fractionated due to Jeans escape of hydrogen to space (Owen et al., 1988), and 2-5 times the terrestrial value in SNC meteorites (Watson et al., 1994). Morphological data (Carr, 1986) and modeling of hydrogen atmospheric losses (Donahue, 1995) suggest that originally there may have been the equivalent of up to 500 m of water, or —7 X 10 g H2O. The total mass of Mars is 0.11 times that of the Earth, and so both planets originally may have had similar bulk water concentrations. 

Jakosky B. M., Pepin R. O., Johnson R. E., and Fox J. L. (1994) Mars atmospheric loss and isotopic fractionation by solar-wind-induced sputtering and photochemical escape. Icarus 111, 271-288. 

Quinone exists in the atmosphere in the gas phase. The dominant atmospheric loss process for quinone is expected to be by reaction with the hydroxyl (OH) radical (reaction with ozone is expected to be slow because of the >C(0) substituent groups). The estimated half-life and lifetime of quinone in the atmosphere due to reaction with the OH radical are 3 and 4 h, respectively. Bolton JL, Trush MA, Penning TM, Dryhurst G, and Monks TJ (2000) Role of quinones in toxicology. Chemical Research in Toxicology 13 135-160. Monks TJ and Jones DC (2002) The metabolism and toxicity of quinones, quinoimines, quinone methides, and quinone-thioethers. Current Drug Metabolism 3 425 38. O Brien PJ (1991) Molecular mechanisms of quinone cytotoxicity. Chemico-Biological Interactions 80 1-14. 

The subsequent atmospheric fate of these aromatic aldehydes is controlled by reaction with OH and NO3 radicals and photolysis by sunlight. Kinetic studies of the gas-phase reactions of the tolualdehydes and dimethlybenzaldehydes have been recently performed (Thiault et al, 2002 and Clifford, 2004) and preliminary studies of the photolysis of the tolualdehydes have also been reported (Volkamer et al., 2000 and Thiault et al., 2001). In this work the photolysis of the 3 tolualdehydes and 6 dimethylbenzaldehydes (DMBAs) were investigated during July 2003. The measured photolysis rate coefficients have been used to calculate tropospheric lifetimes and provide an assessment of the relative importance of photolysis as an atmospheric loss process for the compounds. 

Lifetimes (in homs) of die aromatic aldehydes with respect to die various atmospheric loss processes. 

However, Genda and Abe (2005) and Kramers (2003) have shown that the Earth was likely to have had a very early liquid water ocean. Consequently, atmospheric loss probably took place in the presence of a liquid water ocean, leading to enhanced volatile loss. 

Genda, H. and Abe, Y., 2005. Enhanced atmospheric loss on protoplanets at the giant impact phase in the presence of oceans. Nature, 433, 842—4. 

Under tropospheric conditions, the alkanes react with OH radicals during daylight hours and with the N03 radical during nighttime hours, with the latter process being of minor (< 10%) importance as an atmospheric loss process. 

Phenol, the cresols, and the dimethylphenols are formed from the atmospheric degradation of benzene, toluene, and the xylenes, respectively, and data are available concerning the atmospheric reactions of these compounds. The potential atmospheric loss processes of phenolic compounds are reaction with N03, OH radicals, and 03, together with wet and dry deposition (these compounds are readily incorporated into rain- and cloud-water and fog). The OH radical reactions proceed by OH radical addition to the aromatic ring and by H-atom abstraction from the substituent -OH and -CH3 groups (Atkinson, 1989) ... 

This class of organic emissions is exemplified by acetone and its higher homologues. As for the aldehydes, photolysis and reaction with the OH radical are the major atmospheric loss processes (Atkinson, 1989). The limited experimental data available indicate that, with the exception of acetone, photolysis is probably of minor importance. Reaction with the OH radical is then the major tropospheric loss process. For example, for... 

Dust-driven winds are thought to be the major cause for the complete loss of an AGB star s H- and He-rich atmosphere. Loss of the stellar envelope to the CSE limits the duration of the AGB stage to 10 to 10 years. The last material leaves an AGB star in a fast superwind that shocks and ionizes the older, chemically processed CSE ejecta, which then appears as a so-called planetary nebula that surrounds a white dwarf - the remnant C-O-rich stellar core (57). 

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