Exchange time atmosphere

Craig, H. (1957b). The natural distribution of radiocarbon and the exchange time of carbon dioxide between atmosphere and sea. Tellus 9,1-17. 

Organic matter in soils is the largest carbon reservoir in rapid exchange with atmospheric C02, and thus it is important as a potential source and sink of greenhouse gases over time scales of human concern (Fischlin and Gyalistras, 1997). SOM... 

Chemicals become well mixed throughout large portions of the troposphere in a matter of weeks. Exchange of atmospheric chemicals across the equator, however, is relatively slow compared with the mixing time within either hemisphere alone. Thus, for some purposes, the troposphere may be thought of as containing two boxes, the Northern and Southern Hemispheres. Within each box, chemicals mix in a few weeks to mix between them, however, requires 1 to 2 years. 

Table 1-9. Values for the Exchange Times between Different Atmospheric Reservoirs Reported by Various Authors... 

Fig. 11-4. Exchange of C02 between atmosphere and ocean in a two-box ocean model. Reservoir contents are shown in units of Pg C ( = 1012 kg C), exchange coefficients in yr l, and residence times in years. For comparison, the exchange of atmospheric carbon with the biosphere is shown in parallel. For simplicity the biosphere is represented by the two reservoirs of short-lived photosynthetic active components and the long-lived structural material. A more detailed breakdown of the biospheric reservoir is shown in Fig. 11-6.

Craig, R. A. (1950). The observations and photochemistry of atmospheric ozone and their meteorological significance. Meterorol. Monographs 1/2 Amer. Meteorol. Soc., Boston. Craig, H. (1957). The natural distribution of radiocarbon and the exchange time of carbon dioxide between atmosphere and sea. Tellus 9, 1-17. 

Fluctuations that have been measured in the 5 G values of sedimentary organic matter over the Earth s history (e g. Schidlowski 1988) can thus be interpreted in terms of the productivity in the water coltrrrm and the availability of DIG in a particular geological time period. In a study of sediments from the central equatorial Pacific Ocean spanning the last 255,000 years it has been demonstrated that the carbon isotopic composition of fossil organic matter depends on the exchange between atmospheric and oceanic GO. Ghanges with time can then be used to estimate past atmospheric carbon dioxide concentratiorrs (Jasper et al. 1994). 

The calcium oxides and hydroxides are primarily produced during the calcination of limestone (calciinn carbonate) to form hme (qq.v.), CaO, and its subsequent slaking with water to produce calcium hydroxide (Ca(OH)2), slaked time. Calciiun oxide is a very unstable compound and will readily combine with water to form calcium hydroxide. The reaction by which time cements form, tiie exchange of atmospheric carbon dioxide for the hydrous component of slaked lime, is a slow process, and unconverted Ca(OH)2 can linger for decades or even centuries. 

This is the exchanger where heat flows from the room return or mixed air to cold refrigerant or to chilled water. It is an arrangement of finned tubes normally of aluminum fins on copper tubes, but copper fins can be specified for corrosive atmosphere. Performance characteristics are controlled by fin and tube spacing. If the room rh is high, dehumidification may be brought into use by operating the coil or one of a number of parallel coils at a low temperature. If the room s sensible heat load is low reheat must be allowed to operate at the same time. 

Fig. 4-17 Rough estimates of characteristic time for exchange of air and water respectively, between Afferent parts of the atmosphere and oceans.

Example Obtain a relationship for the residence time of gases in the atmosphere with respect to gas exchange ... 

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