Atmosphere composition of the terrestrial

Table 5 Composition of the terrestrial atmosphere, Henry constants and calculated concentrations for equilibrium in water at 25°C, partial pressures of the atmosphere and ionic strength of 0 (after Alloway and Ayres 1996, Sigg and Stumm 1994, Umweltbundesamt 1988/89).

Table 1 provides the composition of the terrestrial atmosphere, which is the standard for all noble-gas analyses, and indicates the general relative abundances of the isotopes. The masses of the rare-gas planetary reservoirs are given in Table 2. 

The interior and atmospheric composition of the Jovian planets and Titan differ from our terrestrial planets in particular, Jovian planets and Titan contain complex organic solids named tholins [152]. Sagan et al. [153] diermochemically... 

Marti 2001), also make the analyses prone to atmospheric contamination. Nevertheless, the indigenous component can be separated by a stepwise gas extraction protocol in suitable samples, and three studies all find the isotopic composition of indigenous lunar nitrogen to be enriched in the heavy isotope by 13-17%o relative to the composition of the terrestrial atmosphere (Kerridge et al. 1991a Murty and Goswami 1992 Mathew and Marti 2001). Mathew and Marti (2001) note the approximate consistency of this composition with values reported for the terrestrial mantle but caution that fractionation effects during the formation of the moon are difficult to assess. 

The standard for noble gas measurements, and the reference for discussions of data, is the composition of the terrestrial atmosphere. The abundances of the noble gases are in Table 1, along with those of other major and minor gases that are more abundant than Xe. With the exception of Ar, which is dominated by radiogenic " °Ar, the noble gases are present as trace constituents. Isotopic compositions are provided in Table 2. Since air is the reference standard for laboratory analyses, measurements of other media are typically normalized to these values. 

NH3 and to a lesser extent mono-, di-, and trimethylamines are the only significant gaseous bases in the atmosphere, and there has been considerable interest in whether the oceans are a source or sink of these gases. Early attempt to assess the air-sea flux from concentration measurements are probably suspect because of the ease with which sample contamination can occur during laboratory processing and analysis. It should be noted here that due to its high solubihty (low value of Henry s law constant), the air-water transfer of NH3 (and the methylamines for the same reason) is under gas phase control (see Section 6.03.2.1.1). The first reliable measurements were probably from the North and South Pacific and indicated that the flux of NH3 from sea to air is of a size similar to that for emission of DMS (Quinn et al., 1990, 1988). Indeed, the authors showed that this similarity was mirrored in the molar ratio of (non-sea-salt) sulfate to ammonium (1.3 0.7) in atmospheric aerosol particles collected on the cruise, indicating that for clean marine air remote from terrestrial sources, the emission of DMS and NH3 from the sea appears to control the composition of the aerosol. 

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