Earth acid rain

Acid deposition refers to the transport of acid constituents from the atmosphere to the earth s surface. This process includes dry deposition of SO2, NO2, HNO3, and particulate sulfate matter and wet deposition ("acid rain") to surfaces. This process is widespread and alters distribution of plant and aquatic species, soil composition, pH of water, and nutrient content, depending on the circumstances. 

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. 

Again, the myriad influences of human activity are usually viewed as separate effects (global warming, acid rain, ozone loss, urban pollution, etc.) However, these individual symptoms clearly have major interdependencies that must be understood if humans are to learn how to coexist with a stable Earth system. 

Prinn, R. G. and Fegley, B. (1987). Bolide impacts, acid rain, and biospheric traumas at the Cretacious-Tertiary boundary. Earth Planet. Sci. Lett. 83,1-15. 

About half the manmade emissions of sulfur dioxide become sulfate aerosol. That implies that currently 35 Tg per year of sulfur in sulfur dioxide is converted chemically to sulfate. Because the molecular weight of sulfate is three times that of elemental sulfur, Q is about 105 Tg per year. Studies of sulfate in acid rain have shown that sulfates persist in the air for about five days, or 0.014 year. The area of the Earth is 5.1 x lO m. Substituting these values into the equation for B yields about 2.8 X 10 g/m for the burden. 

IV. ATMOSPHERIC ELECTROCHEMISTRY EFFECTS OF THE ELECTRICAL DOUBLE LAYER OF THE EARTH AND ACID RAINS... 

The clouds around Venus contain relatively large droplets of sulfuric acid, which occasionally rain down on the surface of the planet, or at least they try to, because the temperature is so high that the droplets evaporate before they actually reach the surface. (This almost rain is called virga, the term for any kind of precipitation that evaporates before it reaches the ground.) On Earth, however, the sulfuric acid does not evaporate but falls to the ground as acid rain, an environmental pollutant that can destroy buildings and harm plants and animals. 

Venus is not the only planet in the solar system that has sulfuric acid in its atmosphere. Earth has it, too. Unlike Venus, where the surface temperatures are too hot for acidic rain to reach the... 

At one point it was assumed that the earth, its oceans and rivers, and its atmosphere were so vast or self-cleansing that we could discharge anything into them without damage to our planet. We now know this is not true. Currently, we must deal with toxic waste dumps, with smog, with acid rain that kills forests, and with pollution of rivers and the ocean by chemical discharges. How did this happen ... 

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. 

In spite of the occurrence of natural events such as the eruption of Krakatoa, scientists are now well aware that human activities can have serious long-term effects on the Earth s atmosphere. The hrst such effect to be noticed historically was the increase in acid precipitation resulting from the combustion of fossil fuels. Acid precipitation is also known as acid rain or acid deposition. The second, discovered in the mid-20th century, was the depletion of stratospheric ozone. More recently, atmospheric scientists established a link between so-called greenhouse gases and global climate change. 

One reason that the term acid deposition is preferred to the term acid rain is that sulfuric and nitric acid formed by the processes described may return to Earth s surface in either a wet or a dry form. Wet deposition consists of acids dissolved in water, as occurs in acid rain or acid snow. Dry deposition occurs when acids or nonme-tallic oxides remain in gaseous form or adhere to solid particles, on which they are carried to the ground. About half of the components of acid deposition fall back to Earth in each of these two forms, wet and dry. 

Dissolving an eggshell in vinegar demonstrates a modern environmental problem. Calcium carbonate is present in Earth s crust as marble, limestone, and chalk. Many modern buildings, statues, and stone structures contain calcium. Acid rain is slowly dissolving these structures. 

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. 

Although the term acid rain has been used extensively in the popular literature to describe the formation and deposition of acids at the earth s surface, the terminology acid deposition is more commonly encountered in the scientific literature. The reason for this is that deposition of acids can occur either as dry deposition or as wet deposition. The former refers to the direct transport of acidic gases or small particles to the surface, followed by adsorption, without first being dissolved in an aqueous phase such as rain, clouds, or fog. Wet deposition, on the other hand, refers to the transport of acids to, and deposition on, surfaces (including soil, trees, grass, buildings, etc.) after the acids have been dissolved in an aqueous medium. It should be noted that the surface itself can be either wet or dry the terms wet and dry deposition refer to the mechanism of transport to the surface, not to the nature of the surface itself. 

Atmospheric aerosols usually means the solid and liquid particles in the earth s atmosphere, excluding the solid and liquid water particles in clouds, fog, and rain. Although very tenuous and highly variable, they act as condensation nuclei for cloud droplets, alter the optical properties of clouds, and possibly play a role in the formation of smog and acid rain. And an understanding of their optical properties is needed for many applications ... 

There is a vaiiety of problems associated with air pollution, starting from photochemical smog, ozone formation, and acid rain at a regional level, to the greenhouse effect and ozone-layer depletion at a global level. These problems have an adverse impact on both environment and public health (Table 1.1) the last two problems are a threat to life on Earth generally. 

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. 

It is interesting to note how interrelated the topics of water, air, and solids (soil) pollution are. Acid rain, for example, commences as an air pollutant and ends up as a soil and water pollutant. See also Pollution (Air). Thus, water pollution may be direct or indirect. Because they have a mass, air pollutants ultimately fall to Earth s surface and thus pollute the oceans, bodies of freshwater, and the land. 

Not surprisingly, it s the layer nearest the earth s surface—the troposphere—that is the most easily disturbed by human activities and has the greatest effect on the earth s surface conditions. Among those effects, air pollution, acid rain, and the greenhouse effect are particularly important. 

England 0-97 mgrm. per litre of rain in the oountry, and 5-14 mgrms. in the towns and in Scotland, 0-53 mgrm. in the country, and 3-81 mgrms. in the town. Table V shows that ammoniacal nitrogen is usually in excess of nitric nitrogen, but the converse is true of tropical countries. The ammonia is usually collected by the acids—nitric, hydrochloric, or sulphuric—in the atmosphere and. carried to earth in rain or snow. 

This U.S. Geological Survey site explores ways chemists use analytical chemistry to determine Earths age, understand how pollution and acid rain affect Earths plants and animals, and how the planets climate has changed over thousands of years. 

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