Acid rain sulfur oxides contribution

This is deadly to most forms of aquatic life. Water downstream from a mine may be contaminated by acid mine drainage, the result of microbial oxidation of discarded waste material at the mine site. Acid mine water principally contains sulfuric acid produced by the oxidation of iron pyrites (FeS2). Industrial wastes and acid rain may also contribute to the acidity of natural waters. 

The contaminants may be deposited on the surfaces of the materials in the form of anhydrous or hydrated species. Some pollutants, like CO2, SO, NO, and HCl, are typical of urban and industrial areas, give rise to acid rains, and might contribute to the cathodic processes, while others, such as chlorides, are typical but not exclusive of marine and coastal areas and give rise to hygroscopic salts that increase the duration of wetting of surfaces, increase the conductivity of solutions, and make less protective the corrosion products. Some others, such as the sulfides, which can result from microbiological activity, alter the composition of the corrosion products, their protective capability, and the nobility of the metal often they are semiconductors, depolarize the cathodic process of hydrogen evolution, and may be oxidized to sulfuric acid by bacteria. Ammonia alters the composition of corrosion products and the solubility of metal ions it has particularly drastic effects on copper alloys and their corrosion forms. In the transport of these contaminants toward the surfaces, an important role is exerted by the wind and by the orientation of the surfaces, which can promote or hinder the washout by the rains. 

Acid deposition occurs when sulfur dioxide and nitrogen oxide emissions are transformed in the atmosphere and return to the earth in rain, fog or snow. Approximately 20 million tons of SOj are emitted annually in the United States, mostly from the burning of fossil fuels by electric utilities. Acid rain damages lakes, harms forests and buildings, contributes to reduced visibility, and is suspected of damaging health. 

Burning fossil fuels can release air pollutants such as carbon dioxide, sulfur oxides, nitrogen oxides, ozone, and particulate matter. Sulfur and nitrogen oxides contribute to acid rain ozone is a component of urban smog, and particulate matter affects respiratory health. In fact, several studies have documented a disturbing correlation between suspended particulate levels and human mortality. It is estimated that air pollution may help cause 500,000 premature deaths and millions of new respiratory illnesses each year. 

Similarly, SO2 and SO3 (SOJ compounds are produced in combustion by the oxidation of sulfur compounds within the fuel source. SO , emitted into the atmosphere can be incorporated into aerosol particles and wet-deposited as corrosive sulfuric acid. Both NO , and SO , emissions contribute to acid rain content from wet deposition, due to their participation in the formation of nitric and sulfuric acid, respectively. 

Acid rain arises from the oxidation of S02 and N02 in the troposphere to form sulfuric and nitric acids, as well as other species, which are subsequently deposited at the earth s surface, either in precipitation (wet deposition) or in dry form (dry deposition). The contribution of organic acids has also been recognized recently (see Chapter 8). These oxidation and deposition processes can occur over relatively short distances from the primary pollutant sources or at distances of a fOOO km or more. Thus both short-range and long-range transport must be considered. 

DMS is photochemically oxidized in the atmosphere to methanesulfonic and sulfuric acids. These strong acids contribute, along with nitric and organic acids, to the natural acidity of precipitation. Recent problems with acid rain have aroused interest in the anthropogenic and natural sources of volatile sulfur compounds (2). 

Renewable energy processes do not generate sulfur dioxide, but coal-burning power plants do therefore, sulfur oxides (just as C02) are present in the atmosphere, contributing to acid rain and other hazards. The predominant form of sulfur oxide in the atmosphere is sulfur dioxide (S02) itself. Some sulfur trioxide (S03) is also formed in combustion processes, but it rapidly hydrolyzes to sulfuric acid, which is considered to be a particulate matter. In the United States, the ultimate air quality goals (secondary standards) for sulfur dioxide are 60 pg/m3 (0.02 ppm) annual arithmetic average and 260 pg/m3 (0.1 ppm) maximum 24 h concentration, which are not to be exceeded more than once a year. 

Indirect Sources Air, water, and soil can become polluted from a variety of indirect sources. Motor vehicles and factory smokestacks release gases that can indirectly cause many different types of pollution. The acidic gases that are produced (sulfur dioxide and nitrogen oxides) dissolve and contribute to the formation of acid rain. The concentrations of ions in ground water are affected by how acidic the water is. 

NOx emissions can be curtailed by equipping vehicles with modem catalytic converter technology. However, sulfur oxides in the exhaust reduce the efficiency of NOx conversion. Sulfur oxides also impede diesel particulate traps. Both SOx and NOx contribute to acid rain, causing other adverse environmental consequences. 

Considerable attention has been given to nitrogen oxides (and sulfur oxides) in the atmosphere because of their contributions to acid rain. Several studies suggest that different isotopic techniques can be used to differentiate among different types of atmospherically derived nitrate and ammonium. For example, Heaton (1990) found that derived from vehicle exhaust... 

Sulfates are discharged into water from mines and smelters, and from kraft pulp and paper mills, textile mills, and tanneries. Atmospheric sulfur dioxide, formed by the combustion of fossil fuels and by metallurgical roasting processes, may contribute to the sulfate content of surface waters. Sulfur trioxide, produced by the photolytic or catalytic oxidation of sulfur dioxide, combines with water vapor to form dilute sulfuric acid, which falls as acid rain . The environmental fate and transport of sulfate are inextricably linked to the physical and chemical processes active in the earth s sulfur cycle. 

Initially, fuel sulfur was regulated to reduce emissions of the oxides of sulfur, which contribute to acid rain, ozone, and smog. The recent and stricter round of sulfur specifications, however, are an effort to reduce automobile emissions of the oxides of nitrogen (NO c) and particulate matter (PM). For example, the 15 ppmw diesel sulfur limit follows from the USEPA s parallel program of rule making that seeks to reduce automobile NO and PM emissions by 95% and 90%, respectively, by 2007. Automobile manufacturers are demanding ultra-low-sulfur fuels because only then would their advanced, sulfur-sensitive after-treatment technologies achieve such drastic reductions in NO and PM emissions. 

Unpolluted rain is not harmful. However, many industrial and power plants burn coal and oU. The smoke produced may contain large quantities of sulfur oxides, suspended particles, and nitrogen oxides. Automobiles also contribute to the problem by emitting similar oxides. These chemicals react with water in the air to form acids, such as sulfuric acid. These acids reach the surface of Earth in fog, rain, snow, and dew. Acid rain can have a disastrous effect when it reaches bodies of water and waterways. But if a lake has a high limestone content, it is able to somewhat neutralize the acid. 

Unfortunately, sulfur is a contaminant of fossil fuels. The combustion of fossil fuels releases noxious oxides of sulfur—sulfur dioxide (SO ) and sulfur trioxide (SO3)—into the atmosphere, contributing to respiratory problems, air pollution, and acid rain. Billions of dollars are... 

Similarly, the chemistry of the nitrogen species in coal is also of some importance. Nitrogen oxides (Morrison, 1980) also contribute to the formation and occurrence of acid rain, in a similar manner to the production of acids from the sulfur oxides, yielding nitrous and nitric acids ... 

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