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Environmental Toxicology : Biological and Health Effects of Pollutants - Chapter 8

Chương này xem xét bốn trong số các chất ô nhiễm không khí lớn khí sulfur dioxide (SO2), nitrogen dioxide (NO2), ozon (O3), và carbon monoxide (CO). các tầm quan trọng của những chất gây ô nhiễm không khí khí được nhấn mạnh bởi thực tế là là bốn trong số sáu "Tiêu chuẩn chất ô nhiễm không khí" quy định của Hoa Kỳ Cơ quan Bảo vệ Môi trường (EPA). Chất gây ô nhiễm không khí hai tiêu chí khác là những hợp chất hữu cơ dễ bay hơi (VOC) và chì (Pb). VOC được thảo luận trong Chương 11, trong khi Pb được bao. | Chapter 8 Air Pollution - Inorganic Gases 8.1 INTRODUCTION This chapter considers four of the major gaseous air pollutants sulfur dioxide SO2 nitrogen dioxide NO2 ozone O3 and carbon monoxide CO . The importance of these gaseous air pollutants is emphasized by the fact that they are four of the six Criteria Air Pollutants regulated by the U.S. Environmental Protection Agency EPA . The other two criteria air pollutants are volatile organic compounds VOCs and lead Pb . VOCs are discussed in Chapter 11 while Pb is included in Chapter 12. 8.2 SULFUR DIOXIDE SO2 and sulfur trioxide SO3 are the two sulfur oxides SOx that are important air pollutants. This chapter focuses on SO2 because it is far more important than SO3 as an air pollutant. In fact based on the quantities emitted into the atmosphere SO2 is considered the most dangerous of all gaseous pollutants. 8.2.1 Sources of SO2 Atmospheric SO2 arises from both natural and anthropogenic sources. Sulfur compounds are emitted naturally through volcanic action sea salt over the oceans and decomposition of organic matter mostly as hydrogen sulfide H2S . Most anthropogenic emissions of sulfur S to the atmosphere about 95 are in the form of SO2. The main human activities that cause SO2 emission include combustion of coal and petroleum products petroleum refining and nonferrous smelting. In the U.S. about 95 of the total emission is from industry and stationary sources. The S content of coal ranges from 0.3 to 7 and it is present in both organic and inorganic forms whereas in oil the content ranges from 0.2 to 1.7 and the S is in organic form. The most important S-containing compound in coal is iron disulfide or pyrite FeS2 . When heated to high temperatures pyrite is oxidized through the reactions shown below FeS2 3O2 FeSO4 SO2 8.1 4FeS2 11O2 2Fe2O3 8SO2 8.2 2005 by CRC Press LLC In the smelting process sulfide ores of copper Cu Pb and zinc Zn are oxidized roasted forming metallic oxides. For example zinc sulfide ZnS is .