Fossil fuel combustion acid rain

Selection of pollution control methods is generally based on the need to control ambient air quaUty in order to achieve compliance with standards for critetia pollutants, or, in the case of nonregulated contaminants, to protect human health and vegetation. There are three elements to a pollution problem a source, a receptor affected by the pollutants, and the transport of pollutants from source to receptor. Modification or elimination of any one of these elements can change the nature of a pollution problem. For instance, tall stacks which disperse effluent modify the transport of pollutants and can thus reduce nearby SO2 deposition from sulfur-containing fossil fuel combustion. Although better dispersion aloft can solve a local problem, if done from numerous sources it can unfortunately cause a regional one, such as the acid rain now evident in the northeastern United States and Canada (see Atmospheric models). References 3—15 discuss atmospheric dilution as a control measure. The better approach, however, is to control emissions at the source. 

Acidic precipitation is a growing environmental problem. Acid rain, snow or fog is formed when oxides of sulfur and nitrogen from fossil fuel combustion are oxidized in the atmosphere by ultra-violet light and ozone to give sulfuric and nitric acids. These acids then mix with atmospheric water to form acidic precipitation. Since the normal pH of atmospheric water is 5.6-5.7, precipitation having a pH below 5.6 is termed acid rain (J, ). 

This is a term used to describe all precipitation (rain, snow or fog) which is made acidic by acids stronger than aqueous CO2. The gases SO2 and NO2, mainly emitted from fossil fuel combustion, are major contributors towards acid rain since these gases are oxidized to acids by the oxygen in the atmosphere ... 

Sources of sulfur dioxide (SO2) include fossil fuel combustion and smelting of nonferrous ores. It has been implicated in various respiratory ailments in humans and is known to play a major role in the formation of acid rain through its conversion to sulfuric acid in the atmosphere. There are a number of... 

A by-product of fossil fuel combustion, SO2 is a major pollutant, and the above two reactions, which take place in cloud droplets, play a key role in the processes leading to acid rain. 

Acid Rain An Environmental Problem Related to Fossil Fuel Combustion ... 

Add Rain Acid rain is the result of sulfur oxides and nitrogen oxides emitted by fossil fuel combustion. These oxides react with water to form sulfuric acid and nitric acid, which then fall as acid rain. 

A third problem associated with fossil fuel combustion is acid rain. The nitrogen oxides and sulfur oxides emitted into air make rain acidic. This acidic rain falls into lakes and streams and makes them acidic as well (see Section 14.11). Some species of aquatic life cannot tolerate the increased acidity and die. Acid rain also affects forests and building materials. Again, good legislation— specificaUy the Clean Air Amendments of 1990— have addressed add rain, and sulfur oxide emissions have been decreasing in the United States over the past 20 years. We can expect to see the positive effects of these reductions in lakes and streams in the coming years. 

The following graph shows the concentration of an atmospheric pollutant, sulfur dioxide, for the period 1990-2006. Sulfur dioxide, a product of fossil fuel combustion, is a main precursor to acid rain. In recent years, because of mandatory reductions legislated by the 9-... 

A component of acid rain, sulfuric acid, forms by the combination of water with sulfur oxide pollutants that are released into the atmosphere as a byproduct of fossil fuel combustion ... 

Historically, sulfur compounds in the troposphere have been the cause of concern from the viewpoint of air pollution since the industrial revolution sulfur dioxide directly emitted from fossil fuel combustion and sulfuric acid aerosols formed by its oxidation in the atmosphere have been studied as the most important air pollutants, and the acid rain caused by their uptake into clouds and fog followed by hquid... 

The other major problems associated with fossil fuel use stem from the products of combustion. The chemical equations shown for fossil fuel combustion all produce cartxM dioxide and water. However, these equations represent the reactions under ideal conditions and do not account for impurities in the fuel, side reactions, and incomplete combustion. When these are taken into account, we can identify three major awiron-mental problems associated with the emissitxis of fossil fuel combustion air pollution, acid rain, and global climate change. We discussed acid rain in Chjpter 3 (see Chemistry in the Environment Acid Rain in Section 3.6). Here we will address air pollution and global climate change, which we first touched on in Section 4.1. 

Earlier in this section, we learned that lightning forms NO in the atmosphere. In Sections 3.6 and 15.12 we saw that NO and NO2, formed as by-products of fossil fuel combustion, are among the important precursors of acid rain. 

The energy industry claimed for a remarkably long time that acid rain in the eastern U.S. is caused by "natural factors," rather than fossil fuel combustion. They succeeded in this deception largely because the public rarely asked for numbers. Three numbers would have sufficed to settle the issue How much... 

Fig. 9. Genesis of acid tain (13). From the oxidation of C, S, and N during the combustion of fossil fuels, there is a buildup in the atmosphere (gas phase, aerosol particles, raindrops, snowflakes, and fog) of CO2 and the oxides of S and N, which leads to acid—base interaction. The importance of absorption of gases into the various phases of gas, aerosol, and atmospheric water depends on a number of factors. The genesis of acid rain is shown on the upper right as an acid—base titration. The data given are representative of the environment in the vicinity of Zurich, Switzedand.

Excess fertilizer and combustion processes also can increase nitrous oxide (NnO) and nitrogen oxides (NOx) in the atmosphere. Nitrous oxide is a powerful greenhouse gas, and nitrogen oxides lead to smog and acid rain. The production of fertilizers requires a great deal of energy. The use of fossil fuels to supply the thermal requirements for fertilizer production further increases emission of nitrogen compounds to the atmosphere. 

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