Gases in the atmosphere

When a liquid or solid substance is emitted to the air as particulate matter, its properties and effects may be changed. As a substance is broken up into smaller and smaller particles, more of its surface area is exposed to the air. Under these circumstances, the substance, whatever its chemical composition, tends to combine physically or chemically with other particles or gases in the atmosphere. The resulting combinations are frequently unpredictable. Very small aerosol particles (from 0.001 to 0.1 Im) can act as condensation nuclei to facilitate the condensation of water vapor, thus promoting the formation of fog and ground mist. Particles less than 2 or 3 [Lm in size (about half by weight of the particles suspended in urban air) can penetrate the mucous membrane and attract and convey harmful chemicals such as sulfur dioxide. In order to address the special concerns related to the effects of very fine, iuhalable particulates, EPA replaced its ambient air standards for total suspended particulates (TSP) with standards for particlute matter less than 10 [Lm in size (PM, ). 

Forests can act as sources of some of the trace gases in the atmosphere, such as hydrocarbons, hydrogen sulfide, NO, and NH3. Forests have been identified as emitters of terpene hydrocarbons. In 1960, Went (10) estimated that hydrocarbon releases to the atmosphere were on the order of 108 tons per year. Later work by Rasmussen (11) suggested that the release of terpenes from forest systems is 2 x 10 tons of reactive materials per year on a global basis. This is several times the anthropogenic input. Yet, it is important to remember that forest emissions are much more widely dispersed and less concentrated than anthropogenic emissions. Table 8-2 shows terpene emissions from different types of forest systems in the United States. 

Fryer, L. S. and G. D. Kaiser, 1979, DENZ - A Computer Program for the Calculation of the Dispersion of Dense Toxic or Explosive Gases in the Atmosphere, UKAEA, Report SRD RI52. 

Reactions between gases in the atmosphere are not ar equilibrium, but for a thorough understanding of them we need to study both the rates at which they take place and their behavior under equilibrium conditions. 

Hamrud, M. (1983). Residence time and spatial variability for gases in the atmosphere. Tellus 35B, 295-303. 

The equilibrium concentration in seawater is described by Henry s Law, which relates the partial pressure of the gas to its concentration (see Chapter 5 and Waser, 1966). Using the appropriate values of Henry s Law constant, Kh, and the partial pressures of gases in the atmosphere, the equilibrium concentrations of several gases are given in Table 10-11 for 0°C and 24°C. 

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

It is scenario 3 that is most consistent with the data depicted in Fig. 1-2. Given that the physical climate system is strongly influenced by gases in the atmosphere that absorb and emit infrared radiation (e.g., H2O, CO2, CH4, etc.), and since the amounts of these species in the air depend to some extent (for some, a great extent) on the functioning of the biosphere, it is logical to view the climate of the Earth as a coupled physical, chemical, and biological entity. 

Most of the non-gaseous impurities in ice were once atmospheric aerosols. Atmospheric aerosols raining onto an ice sheet are of two types primary aerosols, which are incorporated directly into the atmosphere as aerosols (these include continental dust and sea spray), and secondary aerosols which form in the atmosphere from gases. In addition to aerosol-derived impurities, some soluble gases in the atmosphere (HNO3 HCl, H2O2, and NH3) adsorb directly onto ice, and so are measured in a core... 

It is fortunate, however, that there are small amounts of other gases in the atmosphere, notably carbon dioxide and water vapour. Both these gases absorb strongly in the infrared region of the reflected radiation, keeping the heat... 

The increasing level of C02 emission is considered one of the major environmental challenges that our planet is facing today. The concentration of greenhouse gases in the atmosphere reached a new record in 2013, with C02 at 396 ppm which represents 142% of the concentration of the pre-industrial era [1], Findings of a recent global atmosphere watch reported in a... 

Table 6.3. Partial pressures of some gases in the atmosphere (Hem, 1985)...

We assume that the gases in the atmosphere obey the ideal gas law, PV = nRT. Then the... 

Tropospheric chemistry is strongly dependent on the concentration of the hydroxyl radical (OH), which reacts very quickly with most trace gases in the atmosphere. Owing to its short boundary layer lifetime ( 1 s), atmospheric concentrations of OH are highly variable and respond rapidly to changes in concentrations of sources and sinks. Photolysis of ozone, followed by reaction of the resulting excited state oxygen atom with water vapour, is the primary source of the OH radical in the clean troposphere ... 

The extraction of soil with water at pH 7 would seem to be a good way to study the soil inorganic chemistry. The most common solvent that soils are in contact with is water in the form of rain. However, rain is not neutral but acidic. Rainwater pH ranges from 3.8 to 5.6, depending on the air in which it forms. Acid rain that contains H2S04 and HN03 created by the reaction of gases in the atmosphere with water can have a pH as low as 2.0 [2],... 

But, two global climate models show that even if the concentrations of greenhouse gases in the atmosphere had been stabilized by the year 2000, we were already committed to further global warming. 

The composition of the subsurface gas phase may change as a result of gas dissolution into the liquid phase. The solubility of gases in water depends on the type of gas, temperature, salt concentration, and the partial pressure of the gases in the atmosphere. The most soluble gases are those that become ionized in water (CO, NHj, H S), while and are much less soluble (Table 1.2). 

The subsurface generally is an open system. The presence of CO and other gases in the atmosphere affects the partial pressure of gas constiments in the subsurface. For example, carbonate mineral dissolution in a system open to atmospheric COj does not achieve equilibrium. However, higher local subsurface CO concentrations can originate from biological activity and other oxidation processes. 

Fourier Transform Infrared Analysis of Trace Gases in the Atmosphere... 

The most common gases in the atmosphere are nitrogen and oxygen. 

Hexachlorobutadiene is released to the environment in air, water, and soil, mainly as a result of its disposal following industrial use. Most of the hexachlorobutadiene wastes are destroyed by burning some are released to the air in this process. It is not known what happens to hexachlorobutadiene after it enters the air. Based on the information we have on similar compounds, it may be broken down by sunlight and react with gases in the atmosphere. It is not known what chemicals are formed by these reactions or if the compounds formed are harmful. Based on the properties of similar compounds, one-half of the hexachlorobutadiene in the air is expected to be broken down to other chemicals within 60 days. 

---