Acid rain formation

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. 

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. 

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... 

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

At high concentrations (>50ppbv ppbv = parts per billion by volume), O3 in the atmospheric boundary layer becomes a toxic pollutant that also has important radiative transfer properties. The production of nitric acid from NO influences atmospheric pH, and contributes to acid rain formation. In addition, the oxidation of NO to the nitrate (NO3) radical at night influences the oxidizing capacity of the lower troposphere. Determination of the magnitude and location of NO sources is critical to modeling boundary layer and free tropospheric chemistry. 

The sulfur presents in both inorganic and organic forms in coal. The inorganic sulfur occurs as sulfide minerals (pyritic sulfur, FeSj) and/or a range of sulfate compounds (sulfate sulfur). Pyritic and organically bound sulfur constitute the majority of sulfur content, and sulfates are at very low concentrations in coal. Approximately 95% of sulfur content is converted to sulfur dioxide (SO2) during the combustion process and a small amount of sulfur trioxide (SO3) is also formed. Sulfur dioxide is a major contributor to acid rain formation and harmful to the plants and soil (lEA, 2003 Breeze, 2005 Miller, 2005 Suarez-Ruiz and Ward, 2008 Franco and Diaz, 2009 Graus and Worrell, 2009). 

The balance between SO2 and SO3 is important in ARis understanding acid rain formation in the troposphere. From the following information at 25 °C... 

More than a dozen oxides of sulfur are known, but some of them are rather unimportant cyclic monoxides formed by treating a puckered ring of 5 to 10 sulfur atoms with a per-oxy acid, and others are unstable acyclic species. Two of the acyclic oxides, however, are extremely important sulfur dioxide (SO2) and sulfur trioxide (SO3). In the decade of the 1980s, when acid rain became a household word, these two compounds and their roles in acid rain formation became as familiar to the educated laity as carbon monoxide and carbon dioxide. 

Knowledge of the chemical reactions and reaction mechanisms involved in acid rain formation allows chemists to understand and to reduce the environmental impact of human activities from burning fossil fuels, especially coal. 

Free-radical chain reactions also occur during the chlorination of methane (Chapter 10) and of the methyl group of methylbenzene. Ozone depletion by chlorofluorocarbons (CFCs), acid rain formation and formation of photochemical smog (Chapter 25 on the accompanying website) also involve free-radical reactions. (Free-radical reactions are also operating in unpolluted atmospheres and play an important role in all chemical reactions that occur in the gas phase.) The combustion of hydrocarbons, such as petrol, also proceeds via a free-radical mechanism, which has important consequences for the smooth running and performance of combustion engines. Chain reactions may also have ions as intermediates, as opposed to free radicals. 

Usually the process involves the reaction of two gases on the surface of a solid catalyst, which is often in the form of a powder. Such reactions are not only important in many industrial processes, but are also involved in acid rain formation and ozone depletion. 

In the case of sulphur oxide SO it is immediately further oxidized to SO2 in the flame. It seems that a reduction of SO2 can only be obtained by using low-sulphur fuels. SO2 and NO2 are further oxidized to H2SO4 and HNO3 the atmosphere with subsequent acid rain formation. 

Explain how the formation of photochemical smog may contribute to acid rain formation. What is the chemistry involved ... 

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