Troposphere masses

Viggiano A A 1993 In-situ mass spectrometry and ion chemistry in the stratosphere and troposphere Mass Spectron. Rev. 12 115-37... 

The observational data provide a coarse estimate of the tropospheric mass content of nitrogen present as NH3 and NH4, if we adopt a procedure similar to that used in Section 7.6.1. for aerosols. We must assume that the concentrations found in Europe and the United States can be extrapolated... 

It can be assumed that these masses divide equally between the NH and SH. With the average molecular weight of air, = 28.9 g moPthe tropospheric mass of a substance of molecular weight M that has a tropospheric mixing ratio of is... 

Arnold F and Henschen G 1978 First mass analysis of stratospheric negative ions Nature 257 521-2 Eisele F L 1989 Natural and anthropogenic negative ions in the troposphere J. Geophys. Res. 94 2183-96 Oka T 1997 Water on the sun—molecules everywhere Science 277 328-9... 

The atmosphere is the entire mass of air that surrounds the earth. While it extends upward for about 500 miles, the section of primary interest is the portion that rests on the earth s surface and extends upward for about 7 i miles. This layer is called the troposphere. 

Aerosol surface area is likely to be variable even within a remote marine air mass. Previous MBL aerosol studies describe changes in aerosol concentration and composition due to entrainment from the free troposphere (Bates et al., 1998, 2001 Covert et al., 1998). Raes et al. (1997) found an observable link between vertical transport patterns and aerosol variability in the MBL specifically in the Aitken mode (<0.2/u.m). Hence entrainment of aerosol from the free troposphere appears to occur frequently, even in remote MBL air masses. In addition, aerosols have the capacity to travel great distances in the free troposphere, before being entrained into the MBL. 

Mass Independent Isotope Fractionation in the Laboratory, the Stratosphere, and the Troposphere... 

Dievart, P., Allou, L., Louis, F., and Le Calve, S. Tropospheric multiphase chenristry of 2,5- and 2,6-dimethylphenols determination of the mass acconrmodation coefficients and the Herrry s law constants, Phys. Chem. Chem. Phys., 8(14) 1714-1723, 2006. 

Another oxygen isotope fractionation effect is documented in CO2 samples collected between 26 and 35 km altitude, which show a mass - independent enrichment in both 0 and 0 of up to about 15%c above tropospheric values (Thiemens et al. 1995). The enrichment of stratospheric CO2 relative to tropospheric CO2 should make it possible to study mixing processes across the tropopause. 

To date, there are no direct tropospheric measurements of N2Os at the levels predicted to be in natural or polluted air masses. However, concentrations of n2o5 as high as 10-15 ppb have been calculated for the Los Angeles area using simultaneous measurements of ambient N03 and N02 and the equilibrium constant for reaction (24) (e.g., see Atkinson et al., 1986). 

Rockmann, T C. A. M. Brenninkmeijer, P. Neeb, and P. J. Crutzen, Ozonolysis of Nonmethane Hydrocarbons as a Source of the Observed Mass Independent Oxygen Isotope Enrichment in Tropospheric CO, J. Geophys. Res., 103, 1463-1470 (1998). 

Table 8.5 shows the mass accommodation coefficients for S02, as well as for some other gases of tropospheric interest, on liquid water. It is seen that the uptake of most gases into liquid water is quite efficient. Interactions of gas molecules at the air-liquid interface may have additional implications other than the rate at which it is transferred into the aqueous... 

TABLE 8.5 Some Mass Accommodation Coefficients (a) for Gases of Tropospheric Interest on a Liquid Water Surface"... 

As discussed in detail in Sections C.3.d and C.3.e, the fastest atmospheric reactions of S02 are believed to be with H202 and perhaps with Os at higher pH values. Under extreme conditions of large fog droplets (—10 yu,m) and very high oxidant concentrations, the chemical reaction times may approach those of diffusion, particularly in the aqueous phase. In this case, mass transport may become limiting. However, it is believed that under most conditions typical of the troposphere, this will not be the case and the chemical reaction rate will be rate determining in the S(IV) aqueous-phase oxidation. 

Table 9.11 shows the aerodynamic mass median diameter (MMD) for some typical inorganics that are common components of tropospheric particles. Also shown are the calculated crystal enrichment factors, EFcrusl. These are a measure of the enrichment of the element in the airborne particles compared to that expected for the earth s crust, using aluminum as the reference element. Thus EF,.rust for a particular element X is defined as... 

TABLE 9.11 Aerodynamic Mass Median Diameters of Tropospheric Particles Containing Various Elements Observed in a Number of Studies and Enrichment Factors 1... 

Most studies of the chemical composition of particles in the troposphere to date have used analysis of bulk samples, which are usually collected in the boundary layer close to the earth s surface. As discussed in Chapter 6. J.3, there is a great deal of interest in the chemistry of the upper troposphere. Much less is known about the chemical composition in this region, particularly of particles. However, it appears that organics are also important constituents of particles in this region as well. For example, Novakov et al. (1997) in studies of particles both onshore and offshore of the eastern United States found that the mass fraction of the particles due to carbon compounds increased as a function of altitude. In the boundary layer, the fraction was typically 10-40%, increasing to 50-90%atan altitude of 2-3 km. 

Mass spectrometry has the potential for being a very powerful analytical technique for atmospheric measurements, and indeed, it has been used for a number of decades in upper atmosphere measurements of ions and neutrals. Viggiano (1993) has reviewed ion chemistry and the application of mass spectrometry to tropospheric and stratospheric measurements through 1993. The first mass spectrometric measurements were made in the upper atmosphere from 64 to 112 km in 1963 (Narcisi and Bailey, 1965), followed by stratospheric measurements in 1977 (Arnold et al., 1977) and, finally, tropospheric measurements in 1983 (Eisele, 1983 Heit-mann and Arnold, 1983). They have also been extended... 

Table 11.4 summarizes measurements of various species in the stratosphere and troposphere by mass spectrometry through the early 1990s (Viggiano, 1993, and references therein). The altitude at which they were measured and the concentration ranges are shown, as well as whether they were detected using positive or negative ions (see later discussion). 

In short, mass spectrometry is a powerful analytical tool that has been used successfully for a number of years at high altitudes and is now seeing increasing use in the troposphere, including at the earth s surface. A number of different approaches have been developed, including systems that are designed to measure species such as OH, NO, and HNO. They are described in more detail in the sections on measurement techniques for the individual species. 

In short, the concentration of N03 in the troposphere can vary from very small, low-ppt concentrations to several hundred ppt, depending on the particular air mass. As discussed in Chapters 7 and 10, at typical tropospheric levels, it is believed to play a major role in nighttime chemistry, in some cases rivaling daytime OH for the net oxidation of certain organics, particularly alkenes (e.g., see Aliwell and Jones, 1998) as well as certain gaseous PAH. 

FIGURE 11.55 Altitude profiles for H02 + R02 in the free troposphere over southern Germany determined by conversion to OH and measuring OH by the mass spectrometric derivatization technique (adapted from Reiner el at., 1998). 

Eisele, F. L Direct Tropospheric Ion Sampling and Mass Identification, Int. J. Mass Spectrom.. Ion Processes, 54, f f9—f26 (f983). 

Huey, L. G and E. R. Lovejoy, Reactions of SiFs with Atmospheric Trace Gases Ion Chemistry for Chemical Ionization Detection of HNO, in the Troposphere, Ini. J. Mass Spectrom. Ion Processes, 155, 133-140 (1996). 

Water vapor concentrations have also been used to show that stratospheric air in the midlatitudes cannot all have originated via the tropical pump, i.e., path I in Fig. 12.3. For example, Dessler et al. (1995b) have shown that water vapor concentrations in the lowermost stratosphere at 37.4°N, 122.1°W are higher than expected for an air mass that has passed through the cold tropical tropopause. Their data are consistent with path II, although as they point out, these measurements do not exclude path III, which represents convective transport from the troposphere to the stratosphere at mid and high latitudes. Lelieveld et al. (1997) report aircraft measurements of CO, 03, and HNO-, over western Europe that suggest that tropospheric air can be mixed into the lower stratosphere. 

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