Weathering atmospheric gases

Surface waters in pristine condition are affected by the dissolved and particulate loads that come from soil weathering and erosion processes, atmospheric gas dissolution, and dry deposition. Human activ-... 

Almost everyone has a concept of pressure from weather reports of tlie pressure of the atmosphere around us. In this context, high pressure is a sign of good weather while very low pressures occur at the eyes of cyclones and hurricanes. In elementary discussions of mechanics, hydrostatics of fluids and the gas laws, most scientists leam to compute pressures in static systems as force per unit area, often treated as a scalar quantity. They also leam that unbalanced pressures cause fluids to flow. Winds are the flow of the atmosphere from regions of high to low... 

Due to the extremely small pilot flow, the pilot on gas/vapor valves normally discharge to atmosphere through a weather and bug-proof fitting. Pilots for liquid service valves have their discharge piped to the main valve outlet. 

A device commonly used to measure atmospheric pressure is the mercury barometer (Figure 5.1), first constructed by Evangelista Torricelli in the seventeenth century. This consists of a closed gas tube filled with mercury inverted over a pool of mercury. The pressure exerted by the mercury column exactly equals that of the atmosphere. Hence the height of the column is a measure of the atmospheric pressure. At or near sea level, it typically varies from 740 to 760 mm, depending on weather conditions. 

Self-Test 4.9B A weather balloon is filled with helium gas at 20.°C and 1.00 atm. The volume of the balloon is 250. L. When the balloon rises to a layer of air where the temperature is — 30.°C, it has expanded to 800. L. What is the pressure of the atmosphere at that point ... 

The As (arsenic) concentration of seawater is controlled by input of rivers, sedimentation on the seafloor, weathering of the seafloor, exchange between atmosphere and seawater, volcanic gas input, and hydrothermal input. Previous studies on the geochemical cycle of As have not taken into account the hydrothermal flux of As. Therefore, hydrothermal flux of As from back-arc, island arc and midoceanic ridges to ocean is considered below. 

Carbon dioxide plays a key role in climate, in biological processes, in weathering reactions, and in marine chemistry. I shall next describe how the partial pressure of this gas in the atmosphere may be calculated. Because there is a rapid exchange of carbon dioxide between ocean and atmosphere, we must consider the fate of dissolved carbon. 

Helium To provide an inert atmosphere for welding As a coolant in nuclear reactors With 20% oxygen, as a breathing gas for deep-sea divers To inflate the tyres of large aircraft To fill airships and weather balloons (Figure 11.12) In the helium-neon laser In low-temperature research, because of its low boiling point... 

Elemental Sulfur. In 1942, Chatterjee (44) reported the presence of elemental sulfur in weathered Indian coal but not in fresh samples. He suggested that, during weathering, pyrite is first oxidized to ferrous and ferric sulfates, and that then ferric sulfate oxidizes pyrite to elemental sulfur. The presence of elemental sulfur in U.S. coals was confirmed recently by Richard et al. (45) and White and Lee (46). Duran et al. (47) used extraction and gas chromatographic analysis to determine elemental sulfur in a suite of U.S. coals. They found that elemental sulfur (0.03-0.17%) is present in coal that has been exposed to the atmosphere, but is absent in pristine samples that have been processed and sealed under a nitrogen atmosphere. These data support Chatteijee s discovery that elemental sulfur in coal is a weathering product. 

Figure 11.11 shows a meteorologist preparing to release a weather balloon partially filled with helium gas. As the balloon rises, atmospheric pressure decreases. The volume of the balloon increases. 

You may have heard a common joke about Canadian weather If you don t like it, wait an hour and it will change. While this is an exaggeration, atmospheric pressure and temperature rarely remain constant for any extended period of time. Since the volume of gases changes when pressure and temperature change, standards have been designed to allow a comparison of different gas volumes. 

Usually, leaks of liquefied gases are much less serious if such gases are stored refrigerated at low temperatures and pressures than if they are stored at ambient temperatures under pressure. A leak of a volatile liquid held at atmospheric temperature and pressure results in only a relatively slow evaporation of the liquid. Escape of a refrigerated liquefied gas at atmospheric pressure gives some initial flashoff, and then it evaporates at a rate that is relatively slow but faster than the first case, depending on weather conditions. 

Considering that water possesses a certain free space because of its molecular arrangement (Fig. 1.5), and assuming that this free space is negligibly affected by temperature, Equation 1.8 demonstrates that under a constant atmospheric pressure (P), as temperature increases, the expansion potential of the gas causes its apparent solubility to decrease. This explains large fish kills in shallow waters during extremely hot weather, a condition that suppresses the solubility of atmospheric air. 

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