Chlorine photochemical release

The question of the fate of chlorofluorocarbons upon their release into the atmosphere IS of great interest at present because of the potential damage to the earth s protective ozone layer caused by the reaction of ozone with photochemically generated chlorine atoms... 

It is likely that there are as yet ill-defined aqueous-phase reactions in the airborne seawater droplets that release photochemically labile chlorine gases. For example, Oum et al. (1998a) have shown that Cl2 is formed when sea salt aerosols above their deliques-... 

Stratospheric Ozone depletion is largely due to chlorine and bromine radicals released from halogenated hydrocarbons. This paper describes properties, emission histories and budgets of relevant substances and outlines the pertinent photochemical processes, along with a comprehensive presentation of halocarbon measurements and global distributions. 

In conclusion, toxic chlorinated phenol intermediates formed during the chemical, photochemical and/or enzymatic degradation of chlorophenoxyalkanoic compounds would temporarily be detoxified when they are incorporated into the humic acid, since their bioavailability and movement into terrestrial and aquatic ecosystems would be greatly reduced. However, the knowledge of the potential toxicity problems which these bound-residues could give rise to in the environment is still very limited. Xenobiotic chemicals incorporated into humic polymers are not really removed from the ecosystem and they may maintain their identity and toxic properties for unknown time spans, eventually causing time-delayed pollution problems, if and when they will be released from humic substances. 

Emissions of phosgene most commonly arise as a result of its release during manufacture and use, its formation from the decomposition of chlorinated hydrocarbons, and its formation from the photochemical oxidation of air-borne chlorinated organic materials, particularly the C, and C chloroalkanes, and chloroethenes. The location and estimation of air emissions from sources of phosgene have been described by the US Environmental Protection Agency [2088b], Catastrophic emissions and accidental spills and leaks are discussed in Section 3.6. 

CHROMIUM CARBONYL (13007-92-6) CjCrOj Contact with strong oxidizers, heat above 400 F/204°C, or contact with chlorine and fuming nitric acid causes decomposition that may be violent possibly explosive. Sensitive to light undergoes photochemical decomposition. On small fires, use dry chemical powder (such as Purple-K-Powder), foam, or COj extinguishers. Thermal decomposition releases carbon monoxide, carbon dioxide, and carcinogenic chromium(VI) oxide. 

PROBABLE FATE photolysis-, direct photolysis is probably not important, if released to atmosphere, will degrade by reaction with photochemically produced hydroxyl radicals (estimated half-life 1.15 days) oxidation photooxidation in atmosphere can occur, photooxidation half-life in air 4.61-46.1 hrs hydrolysis slow hydrolysis of carbon-chlorine bond, may be important fate mechanism volatilization if released to water, volatilization is expected to be the principle removal process, but may be slow, volatilization half-lives for a model river (1 m deep) and a model environmental pond 13.9 hr, and 6.6 days respectively sorption adsorption on organic matter is possible biological processes no data on bioaccumulation or biodegradation... 

PROBABLE FATE photolysis, photooxidation to chlorinated biphenyls and benzophe-nones probable, indirect photolysis may be significant based on the behavior of the related compound DDT, direct photolysis half-life in water >150 yrs, photooxidation half-life in air 13.3-133 hrs oxidation, not an important process, vapor phase half-life in the atmosphere 1.71 days from reaction with photochemically produced hydroxyl radicals hydrolysis, not an important process, will not hydrolyze in soil volatilization expected to be an important process, evaporation half-life 1.82 days from a river 1 m deep, flowing at Im/sec with a wind velocity of 3 m/sec sorption is an important process, expected to adsorb to sediment if released to water biological processes biotransformation and bioaccumulation are important processes biodegradation expected to be slow... 

PROBABLE FATE photolysis photooxidation to chlorinated biphenyls and chlorinated benzophenones occurs, could be important in aquatic systems, atmospheric and aqueous photo-lytic half-life 6.1 days, photolytic half-life if released to ware 15-26 hrs oxidation photooxidation half-life in air 5.25-40.9 hrs, vapor phase half-life in the atmosphere 4.63 hrs from reaction with photochemical ly produced hydroxyl radicals hydroiysis not an important process ... 

PROBABLE FATE photolysis, based on data for 4-chlorophenol, intramolecular photolysis may be a very important fate, reaction with photochemically produced hydroxyl radicals has a half-life of 1.1 days, will degrade through photolysis if released to water oxidation can occur, but probably cannot compete with biodegradation hydrolysis not important volatilization not important sorption data inconclusive, but potential for adsorption by organics exists biological processes no data on bioaccumulation, biodegradation data not applicable to environment other reactions/interactions can be chlorinated further by chlorine present in HiO... 

This reaction and those of CIONO2 described in the following Sects. 6.5.4 and 6.5.5 are called chlorine activation since they convert metastable HCl and CIONO2 stored in polar night of the stratosphere to photochemically active CI2 and HOCl to be released into the gas phase. As shown in Fig. 4.38 in Sect. 4.4.3, HCl only has an absorption spectrum shorter than 200 nm, whereas HOCl has an absorption spectrum longer than 300 nm, as shown in Fig. 4.38 (Sect. 4.4.4), and can be photolyzed by the low altitude sunlight of early polar spring in the stratosphere. CI2... 

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