THE CAUSES OF ACID RAIN

Acid rain in the eastern U.S. is caused almost entirely by manmade emissions of sulfur and nitrogen oxides from the burning of fossil fuels. This conclusion is based on two lines of evidence an understanding of the chemical reactions that sulfur and nitrogen oxides undergo in the atmosphere and a quantitative tally, or budget, of how much sulfur and nitrogen is emitted from various sources and how much returns to earth. 

These reactions take place spontaneously, and are driven by the fact that the end-products, sulfate and nitrate, are chemically very stable. (The world s oceans, for example, are filled with sulfate and nitrate of ancient origin.) From the chemist s viewpoint, acidity is a byproduct oi the complete oxidation of sulfur and nitrogen. 

Just as water can find its way downhill by many different pathways, so there are many chemical pathways by which SO2 and NOx are converted to acid in the atmosphere. The major pathways do not involve oxygen directly, but instead involve more powerful oxidizing agents, including hydroxyl radical, hydrogen peroxide, and ozone, which are ubiquitous in the atmosphere. 

For both SO2 and NOx, a major reaction pathway is with hydroxyl radical (OH), a highly reactive molecule. xhe reaction between SO2 and (OH) produces the unstable bisulfite radical 

NO2 reacts with (OH) to form acid nitrate directly  

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Sulfur trioxide gas, one of the causes of acid rain, is produced in the upper atmosphere when oxygen reacts with sulfur dioxide gas in the reaction shown below ... 

As we have seen, all fossil fuels contain sulfur, and sulfur dioxide is also produced when they are burnt, alongside the usual products of hydrocarbon combustion. This is one of the causes of acid rain pollution ... 

Similar to smog, acid rain is caused by chemical reactions of pollutants like sulfur dioxide and nitrogen oxides with oxygen and water in the air. The acidic pollutants formed in these reactions are the cause of acid rain. In addition to environmental pollution due to human activi- Trees and other plants are seen here, damaged or. . 1 1 killed by acid rain. Acid rain results when water in... 

The chemistry you will learn in this chapter explains such things as the cause of acid rain and why it destroys monuments and plants, why exercise increases the rate of breathing, how Fosamax prevents bones from being nibbled away, and why blood has to be buffered and how that buffering is accomplished. Acids and bases play an important role in organic chemistry. What you learn about them in this chapter will reappear in almost every other chapter in the book in one form or another. The importance of organic acids and bases will become particularly clear when you learn how and why organic compounds react. 

Understanding the causes of acid rain and working on prevention and remediation requires an understanding of the properties of acids and bases. 

Municipal incinerators are often targeted as a primary cause of acid rain. In fact, power plants burning fossil fuels, which produce sulfur dioxide and nitrogen oxide, are actually the leading cause of acid rain, along with automotive exhaust (176,177). In Europe and Japan, studies show that only about 0.02% of all acid rain can be traced to incineration of PVC (178). 

Sulfur Dioxide. Sulfur dioxide and nitrogen oxides, which are produced in modern society when coal, gas, and oil are burned in cars, power plants, and factories, react with water vapor in the air to form acids that negatively affect organic materials and even metals and stone when dissolved in airborne rainwater, the oxides of sulfur and nitrogen are the main cause of the formation of acid rain (see below). 

Sulfur dioxide is a colorless, poisonous corrosive gas. It causes coughing and nose, throat and lung irritation, even in small quantities. A primary consequence of releasing S02 into the air is the production of acid rain ... 

Present theories of the origin of acid rain indicate that we can limit acid rain by reducing sulfur dioxide emissions and moving to low-sulfur fuels but, only about 20% of the world s petroleum reserves are low in sulfur. Switching U.S. midwestern power plants to low-sulfur coal could cause economic problems since much of the coal from the Midwest and Appalachia has a high sulfur content. Most of the electric power generated in the Midwest uses high-sulfur coal and it would cost tens of billions of dollars to scrub the sulfur out of coal. 

Making a Model Acid precipitation often falls to Earth hundreds of kilometers away from where the pollutant gases enter the atmosphere because the gases diffuse through the air and are carried by the wind. In this lab, you will model the formation of acid rain to observe how the damage caused by acid varies with the distance from the source of pollution. You also will observe another factor that affects the amount of damage caused by acid rain. 

People who suffer from other pulmonary diseases that interrupt the flow of oxygen are especially sensitive to the irritating effects of SO2 and its particulate derivatives. This gas and several other gaseous air pollutants, to be mentioned in a moment, can cause other, delayed toxic effects in the respiratory system. Note also that these same chemicals are the principal causes of acid rain. 

Nitrogen oxides (NO ) are formed during the combustion at high temperature of fossil fuels and of biomasses and are blamed for the production of acid rain, the formation of ozone in the troposphere and of secondary particulate matter and for causing a reduction in breathing functionality and damage to the cardio-circulatory system in humans. 

The principal cause of acid rain is the combustion of fossil fuels that produce sulfur and nitrogen emissions. The primary sources are electrical power plants, automobiles, and smelters. Power plants produce most of the sulfur emissions and automobiles most of the nitrogen emissions. Other sources of acid rain include nitrogen fertilizers, jet aircraft, and industrial emissions. Just as in our discussion of ozone, numerous reactions are involved in the formation of acid rain. The process can be understood by considering the transformation of sulfur and nitrogen oxides into their respective acidic forms sulfuric acid and nitric acid. Sulfur, present up to a few percent in fuels such as coal, is converted to sulfur dioxide when the fuel is burned. The sulfur dioxide reacts with water to produce sulfurous acid, H,SO ,, that is then oxidized to sulfuric... 

Description Sulfur dioxide (S02) is a gas resulting from the combustion of coal, mainly in power plants, and certain types of liquid fuels that contain sulfur. In addition, it is produced during the manufacture of paper and smelting of metals. It may cause respiratory problems and permanent damage to the lungs when inhaled at high levels. It plays a major role in the production of acid rain (EPA site). Carbon disulfide (CS2) has many industrial... 

Scientists have discovered that air pollution from the burning of fossil fuels is the major cause of acid rain. Acidic deposition, or acid ram, as it is commonly known, occurs when emissions of sulfur dioxide (SO ) and oxides of nitrogen (NOx) react in the atmosphere with water, oxygen, and oxidants to form various acidic compounds. This mixture forms a mild solution of sulfuric acid and nitric acid. Sunlight increases the rate of most of these reactions. 

With few exceptions, air pollutants ultimately fall by gravity to the surface of die earth. On land, pollution of the soil and freshwater lakes and rivers and ultimately the groundwater occurs, Fallout on the seas and oceans also occurs, but unless radioactive, the effects are less easy to discern except on die long term. It is indeed difficult to separate air and water pollution. The relationship is explored in the article on Wastes and Pollution. The winds contribute both to the spread and, in some instances, to the contribution of air pollutants. Frequently, as in the case of acid rain, the precipitation of water (an excellent solvent) in the fonn of rain, snow, sleet, ice pellets, etc. causes entrainment of pollutants (gases, mists, particles, etc.). Thus the soils, rocks, lakes, and rivers are subject to the corrosive and biodestructive processes brought about by the presence of alien substances. Acid rain is described later in this article. 

The primary cause of acid rain is industrial and automotive pollution. Each year in industrialized countries, large power plants and smelters that burn sulfur-containing fossil fuels pour millions of tons of sulfur dioxide (S02) gas into the atmosphere, where some is oxidized by air to produce sulfur trioxide (S03). Sulfur oxides then dis-l solve in rain to form dilute sulfurous acid and sulfuric acid ... 

Sulfur dioxide in the effluent gases from coal-burning electric power plants is one of the principal causes of acid rain. One method for reducing S02 emissions involves partial reduction of S02 to H2S, followed by catalytic conversion of the H2S and the remaining S02 to elemental sulfur ... 

Sulfur dioxide is slowly oxidized in the atmosphere to S03, which dissolves in rainwater to give sulfuric acid. The burning of sulfur-containing fuels is thus a major cause of acid rain (Section 9.9). In the laboratory, S02 is conveniently prepared by treating sodium sulfite with dilute acid ... 

In some parts of the world, there is more acid in the rain than normal. This type of rain is called acid rain. Scientists believe that one cause of acid rain is sulfur dioxide. Sulfur dioxide is a type of air pollution produced by burning fuels that contain sulfur atoms. When... 

High sulfur content in coal hinders the use of coal resources because sulfur dioxide emissions from utility and industrial boilers are a cause of acid rain. Thus, research into the nature of sulfur in coal is important for improving coal utilization. Geochemical studies of sulfur in coal provide information about the abundance, distribution, and speciation of sulfur in coal. Many of these properties are determined by geological environments and processes of coal formation. 

Rain with a pH less than 5.6 is known as acid rain. Acid rain is caused by burning fossil fuels (especially coal) and by fertilizers used in intensive agriculture. These activities emit sulfur and nitrogen in gas compounds that are converted to sulfur oxides and nitrogen oxides. These in turn create sulfuric acid and nitric acid in rain. Acid rain may also be created from gases emitted by volcanoes and other natural sources. Acid rain harms fish and trees and triggers the release of metal ions from minerals into water that can harm people. The problem of acid rain in the United States has been addressed in recent decades by the use of scrubbers in coal burning power plants and catalytic converters in vehicles. 

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