Carbon dioxide in earth’s atmosphere

FIGURE 4-43 Increase in the mixing ratio of carbon dioxide in Earth s atmosphere as measured since March 1958 at the Mauna Loa Observatory (data from Keeling and Whorf, 1998). 

The concentration of carbon dioxide in Earth s atmosphere is regulated through a complex interplay of human, biological, and geological mechanisms. In a space vehicle, these mechanisms aren t available. If not controlled, carbon dioxide from the respiration of astronauts could become toxic to them. So how is air quality maintained within a space vehicle ... 

The significance of this particular solubility is spectacularly demonstrated by comparing the earth with its sister planet, Venus. The atmospheric pressure at the surface of Venus is nearly a hundred times greater than at the surface of the earth, and the Cytherean atmosphere itself is more than 96 percent carbon dioxide. The earth s atmosphere would be similar if the oceans had not dissolved the carbon dioxide and precipitated the excess in the form of limestone. One can scarcely begin to imagine the tons of Indiana limestone resting on our shoulders if the earth, like Venus, had no oceans. 

High temperatures trapped a great deal of carbon dioxide in Venus s atmosphere the carbon dioxide, in turn, trapped heat in the atmosphere. As is well known, carbon dioxide is an important greenhouse gas, capable of trapping infrared radiation (heat) released from a planet s surface. The primary difference in atmospheric temperatures between Venus and Earth is the very large amount of heat trapped in Venus s atmosphere by the large concentrations of carbon dioxide. Earth s atmosphere, by contrast, contains relatively small amounts of heat trapped by its correspondingly small concentrations of carbon dioxide. 

The greenhouse effect in Earth s atmosphere. Visible light from the sun is absorbed by the ground, which then emits infrared radiation. Carbon dioxide, water vapor, and other greenhouse gases in the atmosphere absorb and reemit heat that would otherwise be radiated from Earth into space. 

As shown in Fig. 4-42, carbon dioxide (C02) absorbs the second largest amount of long-wave infrared radiation in the atmosphere (about 32% Mann and Lazier, 1996). Over Earth s history, the predominant natural source of CO2 in the atmosphere has been volcanic eruptions, and the vast majority of that C02 is now stored in ocean sediments and rocks derived from those sediments (Mann and Lazier, 1996). If Earth did not have oceans, the concentration of C02 in Earth s atmosphere would be far higher than it is currently. 

Carbon dioxide is a minor component in Earth s atmosphere and an important component in the carbon cycle. Because CO2 is always in the atmosphere, when it rains, CO2 dissolves in rainwater, forming carbonic acid, H2CO3. The result is that rain is always slightly acidic. If rain is always acidic, why is increased acidity in rain such an environmental concern ... 

The Urey reaction is significant on Earth because it is thought to be one way in which carbon dioxide is removed from the atmosphere thus, it may influence climate change. It may be that a similar reaction takes place on Venus, likewise controlling the concentration of carbon dioxide in the Venusian atmosphere. As yet, however, there are no data to suggest that carbonates exist in abundance on the planet s surface. 

In fact, it was not until 1947 that any gas was identified in the Martian atmosphere by spectroscopic means. In that year, the Dutch astronomer Gerard Peter Kuiper (1905-73) found that the concentration of carbon dioxide in the planet s atmosphere was about twice as great as that in the Earth s atmosphere. Even then, however, astronomers did not realize the importance of carbon dioxide in the Martian atmosphere, assuming that other gases might be present in greater abundance. 

Although carbon dioxide is only a trace gas in Earth s atmosphere, with a concentration of about 0.033 percent by volume (see Table 17.1), it plays a critical role in controlling our climate. The so-called effect describes the trapping of heat... 

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. 

The role of carbon dioxide in the Earth s radiation budget merits this interest in atmospheric CO2. There are, however, other changes of importance. The atmospheric methane concentration is increasing, probably as a result of increasing cattle populations, rice production, and biomass burning (Crutzen, 1983). Increasing methane concentrations are important because of the role it plays in stratospheric and... 

C04-0002. Although gasoline is a complex mixture of molecules, the chemical reaction that takes place in an automobile engine can be represented by combustion of one of its components, octane (Cg Hig). Such burning of fossil fuels releases millions of tons of carbon dioxide into the Earth s atmosphere each year. Write a balanced equation for the combustion of octane. 

In our world, most chemical processes occur in contact with the Earth s atmosphere at a virtually constant pressure. For example, plants convert carbon dioxide and water into complex molecules animals digest food water heaters and stoves bum fiiel and mnning water dissolves minerals from the soil. All these processes involve energy changes at constant pressure. Nearly all aqueous-solution chemistry also occurs at constant pressure. Thus, the heat flow measured using constant-pressure calorimetry, gp, closely approximates heat flows in many real-world processes. As we saw in the previous section, we cannot equate this heat flow to A because work may be involved. We can, however, identify a new thermod mamic function that we can use without having to calculate work. Before doing this, we need to describe one type of work involved in constant-pressure processes. 

Nonpolar gases are only slightly soluble in water. For example, water in contact with the Earth s atmosphere contains O2 at a concentration of only about 2.5 x 10 M and CO2 at about 1 x 10 M. Nevertheless, these small concentrations are essential for aquatic life. Fish and other aquatic animals use their gills to extract O2 dissolved in water, and unless that oxygen is replenished, these species die. Submerged green plants carry out photosynthesis using dissolved carbon dioxide, which also must be replenished for these plants to survive. 

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