Trace gases reactive

Ganzeveld L, Lelieveld J (1995) Dry deposition parameterization in a chemistry general-circulation model and its influence on the distribution of reactive trace gases. J Geophys Res 100(D10) 20,999-21,012... 

In Situ Measurements of Stratospheric Reactive Trace Gases... 

Measurements either from the ground or from satellites have been a major contribution to this effort, and satellite instruments such as LIMS (Limb Infrared Monitor of the Stratosphere) on the Nimbus 7 satellite (I) in 1979 and ATMOS (Atmospheric Trace Molecular Spectroscopy instrument), a Fourier transform infrared spectrometer aboard Spacelab 3 (2) in 1987, have produced valuable data sets that still challenge our models. But these remote techniques are not always adequate for resolving photochemistry on the small scale, particularly in the lower stratosphere. In some cases, the altitude resolution provided by remote techniques has been insufficient to provide unambiguous concentrations of trace gas species at specific altitudes. Insufficient altitude resolution is a handicap particularly for those trace species with large gradients in either altitude or latitude. Often only the most abundant species can be measured. Many of the reactive trace gases, the key species in most chemical transformations, have small abundances that are difficult to detect accurately from remote platforms. 

Figure 4. Calculated altitude distributions of the volume mixing ratios of several trace gases (12). The reactive trace gases that directly affect ozone are given by dark lines. Conditions are for the equinox at 30°N.

Balloon-Borne Measurements. To illustrate the versatility possible with balloon-borne platforms, the in situ techniques that have recently made important contributions to our understanding of stratospheric reactive trace gases are highlighted. Each technique is based on a fundamentally different physical principle, providing measurements with unique and characteristic spatial and temporal scales. But first the advantages and disadvantages offered (and suffered) in balloon-borne experimentation are reviewed. Some unique facets of balloon behavior that are relevant to a specific experiment are discussed with that experiment. 

Aircraft measurements of CIO and BrO are discussed in some detail in the next section. Because the aircraft and balloon-borne techniques are essentially the same, further discussion about these two reactive trace gases is deferred to this later section. A discussion of some of the challenges of measuring atomic trace gases in the stratosphere follows. 

Of all the trace gases, particularly the reactive trace gases, some of the most difficult to measure are the trace free radicals. At present, NO, CIO, and BrO have been measured from the NASA ER-2 high-altitude aircraft. The challenges of measuring NO (44, 79) from the ER-2 are similar to those of measuring from balloons, as discussed earlier in this chapter and in Chapter 9. Those discussions are not repeated here, but some examples of NO measurements are given. Instead, the measurement of CIO and BrO from the aircraft platform is discussed. 

Careful reviews by Raes (1985) and Raes et al. (1985) leave unanswered the question of the role of humidity, and of acid or organic vapours, in modifying the diffusivity of decay product ions. By comparison with the mobility in normal air of decay product and ordinary atmospheric small ions, the diffusivity of decay product small ions is probably 2 to 3 x 10-6 m2 s-1. For neutral atoms, or possibly oxide molecules, most measurements give D in the range 5 to 8 x 10-6 m2 s-1, except where radiolytic reaction products or reactive trace gases are present in sufficient concentration to form intermediate ions. 

COSMO-ART Aerosols and Reactive Trace Gases Within the COSMO Model... 

Most of the interaction responsible for artifacts can be prevented by replacing the traditional sampling system, consisting in the filtration and in the selective collection of reactive trace gases with the combination of diffusion separation and filtration this aim is reached by making use of denuders. The air under investigation is drawn through a denuder. 

Methane is oxidized primarily in the troposphere by reactions involving the hydroxyl radical (OH). Methane is the most abundant hydrocarbon species in the atmosphere, and its oxidation affects atmospheric levels of other important reactive species, including formaldehyde (CH2O), carbon monoxide (CO), and ozone (O3) (Wuebbles and Hayhoe, 2002). The chemistry of these reactions is well known, and the rate of atmospheric CH4 oxidation can be calculated from the temperature and concentrations of the reactants, primarily CH4 and OH (Prinn et al., 1987). Tropospheric OH concentrations are difficult to measure directly, but they are reasonably well constrained by observations of other reactive trace gases (Thompson, 1992 Martinerie et al., 1995 Prinn et al., 1995 Prinn et al., 2001). Thus, rates of tropospheric CH4 oxidation can be estimated from knowledge of atmospheric CH4 concentrations. And because tropospheric oxidation is the primary process by which CH4 is removed from the atmosphere, the estimated rate of CH4 oxidation provides a basis for approximating the total rate of supply of CH4 to the atmosphere from aU sources at steady state (see Section 8.09.2.2) (Cicerone and Oremland, 1988). 

Although the non-variant gases can hardly be said to be unimportant, the attention of atmospheric chemists usually focuses on the reactive trace gases. In the same way, much interest in the chemistry of seawater revolves around its trace components and not water itself or sodium chloride (NaCl), its main dissolved salt (see Chapter 6). 

D.J. Erickson, R.G. Zepp, E. Atlas (2000). Ozone depletion and the air-sea exchange of greenhouse and chemically reactive trace gases. Chemosphere-Global Change Set, 2,137-149. 

Claiborn, C. S., and V.P. Aneja. Transport and fate of reactive trace gases in red Spruce needles, part 1 Uptake of gaseous hydrogen peroxide as measured in controlled chamber flux experiments. Environmental Science and Technology 27, 2585-2592, 1993. 

Sea aerosols initially have an ionic composition of sea water but quickly loose water to attain equilibrium with water vapour in the surrounding air, simultaneously cumulating reactive trace gases and undergoing chemical reactions (Pszenny et al., 1998). Also cloud droplets may imdergo dehydration, depending on air humidity. The concentration of nitrate may reach very high values, a mole per (hir and over, when droplets evaporate almost to dryness. 

Georgii HW, Gravenhorst G. 1977. The ocean as source or sink of reactive trace-gases. Pure Appl Geophys 115 503-511. 

Table II gives the chemical composition of Venus atmosphere, which is dominantly CO2 with 3.5% of N2 and smaller amounts of SO2, H2O, CO, and many reactive trace gases. The probable major sources and sinks for each gas are given in Table II. The gas abundances are taken primarily from (II), with new values for H2SO4 (12) and NO (13). Chemistry in Venus lower atmosphere is driven by high temperatures (740 K) and pressures (95 bars) generated by the...

Jacobi HW, Bales RC, Hemrath RE, Peterson MC, Dibb JE, Swanson AL, Albert MR (2004) Reactive trace gases measured in the interstitial air of surface snow at summit, Greenland. Atmos Environ 38 1687... 

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