In the troposphere

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... 

Air pollution (qv) problems are characteri2ed by their scale and the types of pollutants involved. Pollutants are classified as being either primary, that is emitted direcdy, or secondary, ie, formed in the atmosphere through chemical or physical processes. Examples of primary pollutants are carbon monoxide [630-08-0] (qv), CO, lead [7439-92-1] (qv), Pb, chlorofluorocarbons, and many toxic compounds. Notable secondary pollutants include o2one [10028-15-6] (qv), O, which is formed in the troposphere by reactions of nitrogen oxides (NO ) and reactive organic gases (ROG), and sulfuric and nitric acids. 

The chemical transformations occurring in the atmosphere are best characterized as oxidation processes. Reactions involving compounds of carbon (C), nitrogen (N), and sulfur (S) are of most interest. The chemical processes in the troposphere involve oxidation of hydrocarbons, NO, and SO2 to... 

If the earth did not rotate or if it rotated much more slowly than it does, a meridional (along meridians) circulation would take place in the troposphere (Fig. 17-24). Air would rise over the tropics, move poleward, sink over the poles forming a subsidence inversion, and then stream equa-... 

About 51 percent of solar energy incident at the top of the atmosphere reaches Earth s surface. Energetic solar ultraviolet radiation affects the chemistry of the atmosphere, especially the stratosphere where, through a series of photochemical reactions, it is responsible for the creation of ozone (O,). Ozone in the stratosphere absorbs most of the short-wave solar ultraviolet (UV) radiation, and some long-wave infrared radiation. Water vapor and carbon dioxide in the troposphere also absorb infrared radiation. 

Water vapor is the most abundant of the greenhouse gases and is the dominant contributor to the natural greenhouse effect. About 99 percent of all the moisture in the atmosphere is found in the troposphere, which extends about 1(1 to 16 kilometers above sea level. Only about one-tliird of the precipi-... 

Given that the partial pressure of carbon dioxide in the troposphere is 0.26 Torr and that the temperature is 25°C, calculate the volume of air needed to produce 10.0 g of glucose. 

Upward diffusion of water vapor through the cold temperatures of the tropopause is very inefficient in fact, the upper limit of cloud formation often occurs at the tropopause. Thus the stratosphere is so dry as to prevent rain formation, and particles and gases have very much longer residence times there than in the troposphere. Stratospheric removal requires diffusion back through the tropopause, which then may be followed by precipitation scavenging. 

In a sense, the difficulty in measuring [HO ] or [H02 ] in the troposphere is best demonstrated by the number and complexity of the different measurement... 

Direct Measurement of HO, in the Troposphere. Techniques to measure tropospheric concentrations of HO have been reviewed (O Brien Hard, submitted to Advances in Chemistry, 1991) so only a summary will be given here. The most extensively researched technique for [HO ] measurement in the troposphere is based on laser-induced fluorescence (LIF) of HO. This approach has been developed in many configurations directing the laser into the free atmosphere and collecting fluorescence back scatter (LIDAR) (105,106,107) LIF of air sampled at atmospheric pressure... 

When NMHC are significant in concentration, differences in their oxidation mechanisms such as how the NMHC chemistry was parameterized, details of R02-/R02 recombination (95), and heterogenous chemistry also contribute to differences in computed [HO ]. Recently, the sensitivity of [HO ] to non-methane hydrocarbon oxidation was studied in the context of the remote marine boundary-layer (156). It was concluded that differences in radical-radical recombination mechanisms (R02 /R02 ) can cause significant differences in computed [HO ] in regions of low NO and NMHC levels. The effect of cloud chemistry in the troposphere has also recently been studied (151,180). The rapid aqueous-phase breakdown of formaldehyde in the presence of clouds reduces the source of HOj due to RIO. In addition, the dissolution in clouds of a NO reservoir (N2O5) at night reduces the formation of HO and CH2O due to R6-RIO and R13. Predictions for HO and HO2 concentrations with cloud chemistry considered compared to predictions without cloud chemistry are 10-40% lower for HO and 10-45% lower for HO2. 

In summary, biomass burning is a major source of many trace gasses, especially the emissions of CO2, CH4, NMHC, NO,, HCN, CH3 CN, and CH3 Cl (73). In the tropics, these emissions lead to local increases in the production of O3. Biomass burning may also be responsible for as much as one-third of the total ozone produced in the troposphere (74). However, CH3 Cl from biomass burning is a significant source for active Cl in the stratosphere and plays a significant role in stratospheric ozone depletion (73). 

Fig. 4-2 Inverse relationship between relative standard deviation of atmospheric concentration and turnover time for important trace chemicals in the troposphere. (Modified from Junge (1974) with permission from the Swedish Geophysical Society.)...

The resultant O3 layer is critically important to life on Earth as a shield against LTV radiation. It also is responsible for the thermal structure of the upper atmosphere and controls the lifetime of materials in the stratosphere. Many substances that are short-lived in the troposphere (e.g. aerosol particles) have lifetimes of a year or more in the stratosphere due to the near-zero removal by precipitation and the presence of the permanent thermal inversion and lack of vertical mixing that it causes. 

The turnover time of water vapor in the atmosphere obviously is a function of latitude and altitude. In the equatorial regions, its turnover time in the atmosphere is a few days, while water in the stratosphere has a turnover time of one year or more. Table 7-1 Qunge, 1963) provides an estimate of the average residence time for water vapor for various latitude ranges in the troposphere. Given this simple picture of vertical structure, motion, transport, and diffusion, we can proceed to examine the behavior of... 

Release of N2O to atmosphere by variety of sources no significant sinks of N2O in the troposphere have been discovered stratospheric loss estimated by model calculations. 

Figure 7-14 shows one calculation of the expected temperature change profiles for 2030 as a function of altitude. Here, another key feature of the infrared interactions is evident. In the troposphere, the temperature increase is expected to be... 

Fig. 11-24 Carbon-14 in the troposphere and the ocean surface water 1962-1981. values for ocean surface water during this period range from 0-15% with no trend over time. (Modified with permission from R. Nydal and K. Lovseth (1983). Tracing bomb in the atmosphere. /. Geophys. Res. 88, 3621-3642, American Geophysical Union.)...

In the troposphere, nitrogen oxides react to also produce HNO3. The oxidants are free radicals produced photochemically, such as HO2, RO2, and OH. The HNO3 produced in this manner is an important contributor to "acid rain."... 

The lifetime of gaseous NO in the troposphere is on the order of 1-30 days (Sdder-lund and Svensson, 1976 Carrels, 1982 Crutzen, 1988). 

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