Rain formation

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. 

Agriculture, energy plants, road transport, and industry are the most important sources of pollutants of the atmosphere. Agriculture, for example, charges air with acidifying gases that may lead to acid rain formation with a dramatic impact on lakes, rivers, and marine life. 

A few comments Sulfur dioxide (S02) is a gas produced by volcanoes and from many industrial processes. It is sometimes used as a preservative in alcoholic drinks, or dried apricots and other fruits. Generally, the combustion of fossil fuels containing sulfur compounds such as coal and petroleum results in sulfur dioxide being emitted into the atmosphere. Beyond its irritating effect on the lungs, sulfur dioxide is also a threat to the environment, since it is well known to contribute to acid-rain formation. 

C1 activities measured near Richland resulted from some other cause than a low rainfall rate, such as a higher rain formation altitude. 

Hydrogen peroxide is an interesting molecule from both structural and chemical point of view. It is chemically the smallest molecule showing internal rotation. It is an important constituent of troposphere and stratosphere, the recombination ofthe two HO2 radicals being the main cause otTLC formation in atmosphere. It is related to acid rain formation by the oxidation of SO2 by H2O2 either in gas phase or in a water droplet [1-4]. Techniques for the detection of H2O2 can be... 

Although S0X emissions are most often identified as the principal precursors to acid rain, N0X emissions also play an important role in acid rain formation (1). Before methods for limiting N0X emissions from solid fuel combustors can be fully developed, a more detailed understanding of the reaction chemistry of fuel bound ntirogen oxidation must be obtained. 

Fig. 3. General scheme to explain rain formation in Amazon from two sources of vapour the Atlantic Ocean and the forest. The region was divided into 3° longitude strips. The above scheme indicates the city of Manaus (Dall Olio et al., 1979 and Salati et d., 1979).

The inverse relation be een particle size and I/Cl provided a tracer by which the role of the sea-salf particles in the rain-forming process can be studied. Comparison of the I/Cl ratios in the sea-salt particles in marine air to those in raindrops from clouds formed in this air indicated that only the small end of the sea-salt particle spectrum plays any role in the rain formation 110). 

Mineral dissolution kinetics influence such phenomena as development of soil fertility, amelioration of the effects of acid rain, formation of karst, acid mine drainage, transport and sequestration of contaminants, sequestration of carbon dioxide at depth in the earth, ore deposition, and metamorphism. On a global basis, mineral weathering kinetics are also involved in the long-term sink for CO2 in the atmosphere ... 

Acid rain consists of acids formed by the reaction of acid anhydrides and water. List four acid anhydrides commonly involved in acid rain formation and the sources of each. 

FIGURE 17.21 Mean precipitation pH in the United States in 1994. Most SO2 comes from the midwestern states. Prevailing winds carry the acid droplets formed over the Northeast. Nitrogen oxides also contribute to the acid rain formation. 

Accordingly, in this chapter, we consider acid rain monitoring patterns and relative chemistry of acid rain formation in the Asian region. 

Characterize the chemistry of acid rain formation accounting for both sulfur and nitrogen compounds. 

Present a quantitative explanation of why nitric and sulfuric acids have more effects on acid rain formation than carbonic acid. 

Wang W. and Wang T., 1996. On acid rain formation in China. Atmospheric Environment, 30 4091 093. 

Form of Q for o Forward and Reverse Reaction The form of the reaction quotient depends on the direction in which the balanced equation is written. Consider, for example, the oxidation of sulfur dioxide to sulfur trioxide. This reaction is a key step in acid rain formation and sulfuric acid production. The balanced equation is... 

Calculations for larger drops are complicated by phenomena such as shape deformation, wake oscillations, and eddy shedding, making theoretical estimates of E difficult. The overall process of rain formation is further complicated by the fact that drops on collision trajectories may not coalesce but bounce off each other. The principal barrier to coalescence is the cushion of air between the two drops that must be drained before they can come into contact. An empirical coalescence efficiency Ec suggested by Whelpdale and List (1971) to address droplet bounce-off is... 

The role of ice in rain formation was first addressed by Bergeron in 1933, based on the calculations of Wegener. Using thermodynamics, Wegener showed in 1911 that at temperatures below 0°C supercooled water drops and ice crystals cannot exist in... 

The terms W n m correspond to the rates of transport of species i from medium n to medium m. For this simplified case with only four media involved, we need to consider a total of 11 transformation pathways (Figure 20.1). Of these we have already discussed the transformations inside the cloud (rain formation, aerosol-cloud interactions, gas-cloud interactions, and aerosol-gas interactions). Interactions between rain and gaseous compounds will be discussed next to complete the picture. 

The chemical mechanism of acid rain formation in the atmosphere [5] is as follows ... 

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