Acid Rain

The concept and characteristics of possible negative effects of acid rain on humans and the environment. Determination of the main natural sources of acid rain. The functioning and the organization of the Environmental Protection Agency, its purpose.

Рубрика Экология и охрана природы
Вид реферат
Язык английский
Дата добавления 27.05.2017
Размер файла 396,9 K

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АННОТАЦИЯ

Кислотные дожди (реферат). 2017 - 10 стр.

Работа посвящена проблеме кислотных дождей. В нем рассматриваются причины кислотных дождей, их состав и последствия для окружающей среды.

Библиография - 2 назв., рис. - 2.

Acid Rain (essay). 2017 - 10 pp.

The work is devoted to the problem of acid rains. It examines the causes of acid rains, their composition and consequences on the environment.

Bibliography - 2 sources, fig. - 2.

INTRODUCTION

Acid RainAcid rain is a great problem in our world. It causes fish and plants to die in our waters. It causes harm to our own race as well because we eat these fish, drink this water and, eat these plants.

About 20 years ago scientists first believed that acid rain was due to entirely air pollution. They were partially right. Since the beginning of the Industrial Revolution in England, pollution had been affecting all the trees, soil and rivers in Europe and North America. The use of fossil fuels, such as coal and oil, are largely to be blamed for almost half of the emissions of sulfur dioxide in the world. However, there is another cause. The other cause is naturally occurring sulfur dioxide. Natural sources which release this gas are volcanoes, sea spray, rotting vegetation and plankton. acid rain man

The EPA {Environmental Protection Agency} has an acid rain program. This program is working to significantly reduce utilities' emissions of sulfur dioxide and nitrogen oxides, the pollutants responsible for acid deposition.

So, what is acid rain? And what effect they have?

CONTENTS

  • SUMMARY
  • INTRODUCTION
  • What is Acid Rain?
  • Forms of Acid Deposition
  • The Effects of Acid Rain on Ecosystems
  • What can be done?
  • REFERENCES

What is Acid Rain?

Acid rain, or acid deposition, is a broad term that includes any form of precipitation with acidic components, such as sulfuric or nitric acid that fall to the ground from the atmosphere in wet or dry forms. This can include rain, snow, fog, hail or even dust that is acidic [figure 1].

What Causes Acid Rain?Acid rain results when sulfur dioxide (SO2) and nitrogen oxides (NOX) are emitted into the atmosphere and transported by wind and air currents. The SO2 and NOX react with water, oxygen and other chemicals to form sulfuric and nitric acids. These then mix with water and other materials before falling to the ground.

While a small portion of the SO2 and NOX that cause acid rain is from natural sources such as volcanoes, most of it comes from the burning of fossil fuels. The major sources of SO2 and NOX in the atmosphere are :

· Burning of fossil fuels to generate electricity. Two thirds of SO2 and one fourth of NOX in the atmosphere come from electric power generators.

· Vehicles and heavy equipment.

· Manufacturing, oil refineries and other industries.

Winds can blow SO2 and NOX over long distances and across borders making acid rain a problem for everyone and not just those who live close to these sources.

Figure 1 - Acid rain pathway

Forms of Acid Deposition

Wet deposition is what we most commonly think of as acid rain. The sulfuric and nitric acids formed in the atmosphere fall to the ground mixed with rain, snow, fog, or hail.

Dry Deposition

Acidic particles and gases can also deposit from the atmosphere in the absence of moisture as dry deposition. The acidic particles and gases may deposit to surfaces (water bodies, vegetation, buildings) quickly or may react during atmospheric transport to form larger particles that can be harmful to human health. When the accumulated acids are washed off a surface by the next rain, this acidic water flows over and through the ground, and can harm plants and wildlife, such as insects and fish.

The amount of acidity in the atmosphere that deposits to earth through dry deposition depends on the amount of rainfall an area receives. For example, in desert areas the ratio of dry to wet deposition is higher than an area that receives several inches of rain each year.

Measuring Acid Rain

Acidity and alkalinity are measured using a pH scale for which 7.0 is neutral. The lower a substance's pH (less than 7), the more acidic it is; the higher a substance's pH (greater than 7), the more alkaline it is. Normal rain has a pH of about 5.6; it is slightly acidic because carbon dioxide (CO2) dissolves into it forming weak carbonic acid. Acid rain usually has a pH between 4.2 and 4.4.

Policymakers, research scientists, ecologists, and modelers rely on the National Atmospheric Deposition Program's (NADP) National Trends Network (NTN) for measurements of wet deposition. The NADP/NTN collects acid rain at more than 250 monitoring sites throughout the US, Canada, Alaska, Hawaii and the US Virgin Islands. Unlike wet deposition, dry deposition is difficult and expensive to measure. Dry deposition estimates for nitrogen and sulfur pollutants are provided by the Clean Air Status and Trends Network (CASTNET). Air concentrations are measured by CASTNET at more than 90 locations.

When acid deposition is washed into lakes and streams, it can cause some to turn acidic. The Long-Term Monitoring (LTM) Network measures and monitors surface water chemistry at over 280 sites to provide valuable information on aquatic ecosystem health and how water bodies respond to changes in acid-causing emissions and acid deposition.

The Effects of Acid Rain on Ecosystems

An ecosystem is a community of plants, animals and other organisms along with their environment including the air, water and soil. Everything in an ecosystem is connected. If something harms one part of an ecosystem - one species of plant or animal, the soil or the water - it can have an impact on everything else.

· Effects of Acid Rain on Fish and Wildlife

The ecological effects of acid rain are most clearly seen in aquatic environments, such as streams, lakes, and marshes where it can be harmful to fish and other wildlife. As it flows through the soil, acidic rain water can leach aluminum from soil clay particles and then flow into streams and lakes. The more acid that is introduced to the ecosystem, the more aluminum is released.

Figure 2 - Acid rain pathway

Some types of plants and animals are able to tolerate acidic waters and moderate amounts of aluminum. Others, however, are acid-sensitive and will be lost as the pH declines. Generally, the young of most species are more sensitive to environmental conditions than adults. At pH 5, most fish eggs cannot hatch. At lower pH levels, some adult fish die. Some acidic lakes have no fish. Even if a species of fish or animal can tolerate moderately acidic water, the animals or plants it eats might not. For example, frogs have a critical pH around 4, but the mayflies they eat are more sensitive and may not survive pH below 5.5 [figure 2].

· Effects of Acid Rain on Plants and Trees

Dead or dying trees are a common sight in areas effected by acid rain. Acid rain leaches aluminum from the soil. That aluminum may be harmful to plants as well as animals. Acid rain also removes minerals and nutrients from the soil that trees need to grow.

At high elevations, acidic fog and clouds might strip nutrients from trees' foliage, leaving them with brown or dead leaves and needles. The trees are then less able to absorb sunlight, which makes them weak and less able to withstand freezing temperatures.

· Buffering Capacity

Many forests, streams, and lakes that experience acid rain don't suffer effects because the soil in those areas can buffer the acid rain by neutralizing the acidity in the rainwater flowing through it. This capacity depends on the thickness and composition of the soil and the type of bedrock underneath it. In areas such as mountainous parts of the Northeast United States, the soil is thin and lacks the ability to adequately neutralize the acid in the rain water. As a result, these areas are particularly vulnerable and the acid and aluminum can accumulate in the soil, streams, or lakes.

· Episodic Acidification

Melting snow and heavy rain downpours can result in what is known as episodic acidification. Lakes that do not normally have a high level of acidity may temporarily experience effects of acid rain when the melting snow or downpour brings greater amounts of acidic deposition and the soil can't buffer it. This short duration of higher acidity (i.e., lower pH) can result in a short-term stress on the ecosystem where a variety of organisms or species may be injured or killed.

· Nitrogen Pollution

It's not just the acidity of acid rain that can cause problems. Acid rain also contains nitrogen, and this can have an impact on some ecosystems. For example, nitrogen pollution in our coastal waters is partially responsible for declining fish and shellfish populations in some areas. In addition to agriculture and wastewater, much of the nitrogen produced by human activity that reaches coastal waters comes from the atmosphere.

What can be done?

The only way to fight acid rain is by curbing the release of the pollutants that cause it. This means burning fewer fossil fuels. Many governments have tried to curb emissions by cleaning up industry smokestacks and promoting alternative fuel sources. These efforts have met with mixed results. But even if acid rain could be stopped today, it would still take many years for its harmful effects to disappear.

Individuals can also help prevent acid rain by conserving energy. The less electricity people use in their homes, the fewer chemicals power plants will emit. Vehicles are also major fossil fuel users, so drivers can reduce emissions by using public transportation, carpooling, biking, or simply walking wherever possible.

REFERENCES

1. Acid Rain. [Electronic resource]/ - Mode of access: http:// https://www.epa.gov/acidrain/what-acid-rain/ - Date of access: 20.05.2017.

2. Acid Rain. [Electronic resource]/ - Mode of access: http://www.nationalgeographic.com/environment/global-warming/acid-rain/ - Date of access: 20.05.2017.

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