Carbon dioxide cycle history

Figure 2a. Carbon dioxide concentrations in the atmosphere have varied over the glacial cycles of the earth s history, with high vjues at of around 300 during the interglacial period approximately 130,000 years ago...

Hazards attendant on use of ethylene oxide in steriliser chambers arise from difficulties in its subsequent removal by evacuation procedures, owing to its ready absorption or adsorption by the treated material. Even after 2 evacuation cycles the oxide may still be present. Safety is ensured by using the oxide diluted with up to 90% of Freon or carbon dioxide. If high concentrations of oxide are used, an inert gas purge between cycles is essential [7]. The main factors in safe handling and use on laboratory or small pilot plant scales have been identified [8]. Safe operation of ethoxylation processes on industrial scale is discussed, with case histories [15],... 

Studies of the modem global biogeochemical cycle of carbon form one basis for understanding the geologic history of atmospheric CO2. In turn, these investigations of the history of carbon dioxide in the atmosphere provide knowledge that can be used to interpret the future of atmospheric CO2 levels and... 

In recent years innumerable publications have dealt with the natural carbon cycle and its alteration by human activities. Some summary works of interest in this chapter are Atmospheric Carbon Dioxide and the Global Carbon Cycle (ed. Trabalka, 1985), The Carbon Cycle and Atmospheric CO2 Natural Variations, Archean to Present (eds. Sundquist and Broecker, 1985), Chemical Cycles in the Evolution of the Earth (eds. Gregor, Garrels, Mackenzie, and Maynard, 1988), History of the Earth s Atmosphere (Budyko, Ronov, and Yanshin, 1985), and The Chemical Evolution of the Atmosphere and Oceans (Holland, 1984). The interested reader is referred to these volumes for further discussion of material presented here. 

To return now to the carbon dioxide question, early in Earth s history, degassing would have been vigorous but so would have been the return of carbon to the interior, and it is likely that the mantle cycle would have dominated (Sleep and Zahnle, 2001). Moreover, frequent meteorite impacts would have created vast quantities of basalt ejecta that would also have reacted with carbon dioxide to precipitate carbonate. Sleep and Zahnle (2001) concluded that so much carbon dioxide would have been held in the mantle that the greenhouse warming would have been small the Earth was probably heavily glaciated— the Hadean was probably a Norse ice-hell. Possibly early Hadean Earth risked loss of atmospheric carbon dioxide to the interior more than dehydration by hydrogen loss to space, though this would depend on how much methane was in the air. 

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