Acid Rain
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There are many forms of acid rain that are seen around the world. In parts of the world where there is wet weather, there is acid rain, acid snow, and acid fog. In parts of the world where there is dry weather, there is acid gas and acid dust. All of 
the lakes and streams in the world are normally slightly acidic. Heavy rainstorms or melting snow can cause the acidity in lakes and in streams to increase.
What effect does acid rain have on sea life?
Acid rain is very harmful to the environment. Acid rain damages everything over a period of time because it makes the living things in the environment die. Acid rain affects the life in the water as well as the life on land. It is almost worse in water than on land because the fish that are in the water need the water to breathe. When the water gets polluted, then the fish get sick and end up dying.
All rainwater contains some level of acidity. Acidity is measured by pH, which stands for potential of hydrogen. The pH scale measures the amount of acid in a substance. PH is measured on a scale from 0-14, with 7 being neutral. The lower the number is on the pH scale, the more acidic that substance is. Normal rainwater has a pH of 5.6. When the pH level of rainwater goes below 5.6, it is considered acid rain.
All of the sea life will die when the water that they swim in gets to be too acidic. For example, all fish will die when the water goes below a pH of 4.5. Most of the frogs and insects that live around the water will also die when the water reaches a pH of 4.5. With a pH of 5.5, all of the bottom-dwelling bacterial decomposers, animals that eat the remains of the food that other animals don’t want, will begin to die. When these decomposers die, they leave the un-decomposed food on the bottom of the water. This pollutes the water by making the water dirty for all of the fish to swim in. All fresh water shrimp die when there gets to be a pH of 6.0. Aquatic plants will grow the best when the water is a pH between 7.0 and 9.2. If acid rain gets to be more of a problem, then all of the sea life will eventually be gone.
Some of the lakes that were once acidic are recovering, but many more are not recovering. Of the 202 lakes that were chosen to be studied in the early 1980s; only 33% of them have become less acidic.
What effect does acid rain have on the forests of the world?
Trees are also harmed by acid rain. In Germany, the forests are believed to be dying because acid rain is harming them. Scientists say that acid rain damages the waxy outer coating that protects
the leaves. When this happens, it allows the acid to seep into the tree. Instead of water changing from a liquid to a gas inside the leaves, gas is taking the place of the water. This prevents the plant from taking in carbon dioxide to perform photosynthesis, and the plant will eventually die.
Acid rain, acid fog, and acid vapor also damage forests by
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| This is a picture of acid rain falling into a lake. |
damaging the surface of the leaves and needles. This makes it harder for the trees to withstand the cold and will cause the tree to die. Acid rain also harms the soil that the trees are growing in by taking most of the valuable nutrients away from the soil. Acid rain also leaves a lot of aluminum in the soil, which can be harmful to the trees that grow there.
The atmosphere deposits a lot of toxic metals into the forests because acid rain contains metal. Some of these metals are lead, zinc, copper, chromium, and aluminum. When there is acid rain, the rain releases these metals. This is believed to stunt the growth of many trees and plants. This also stunts the growth of mosses, algae, nitrogen-fixing bacteria, and fungi that are needed to help the forest grow. Forests need these because they eat the harmful things that will kill the trees, such as bad bacteria. Acid rain hurts trees because they cannot grow any more.
What effect does acid rain have on the air, us, and our health?
Acid rain affects us in many different ways. One major way is our health. Breathing and lung problems in children and adults who have asthma and in children have been linked to acid air pollution. Everything that we eat, drink, and breathe has at one time come in contact with acid deposits. This could threaten our health by making us become sick. The following health problems occur each year in the U.S. and Canada due to acid rain:
 | 550 premature deaths |
| 1,520 emergency room visits |
| 210,070 asthma symptom days |
As you see, if acid rain became a little less of a problem, then there would be many health problems that could be avoided.
What can acid rain do to non-living things?
Acid rain can also damage non-living things, such as buildings
and statues. It can decay building materials and paints. Worst
of all, it can damage non-replaceable buildings, statues, and sculptures that are part of our nation’s memories that we want to last for a very long time.
What is acid rain caused by?
Acid rain is mainly caused by these substances that are being released into the air:
| Carbon dioxide: Carbon dioxide is released by burning coal, oil, and natural gas. If you inhale carbon dioxide, then since it is toxic, it can cause you to have to breathe more than usual, unconsciousness, and other serious health problems. |
| Carbon monoxide: Carbon monoxide is released by burning gasoline, oil, and wood. When carbon monoxide enters your body, it goes into the bloodstream. When this happens, it will slow down the delivery of oxygen to the rest of the body, causing dizziness, headaches, and fatigue. |
| Chlorofluorocarbons (CFCs): CFCs are the chemicals that are used in industry, refrigeration, air conditioning systems, and consumer products. Whenever CFCs are released into the air, they reduce the stratospheric ozone layer. The stratospheric ozone layer protects Earth’s surface from the harmful rays of the sun. |
| Hazardous air pollutants (HAPS): HAPS are released into the air by sources such as chemical plants, dry cleaners, printing plants, and motor vehicles (cars, trucks, buses, and planes). HAPS can cause serious health problems like cancer, birth defects, nervous system problems, and deaths that are all due to people accidentally letting them go into the air. |
| Lead: Lead is released by house and car paint as well as the manufacturing of lead batteries, fishing lures, certain parts of bullets, some ceramic ware, water pipes, and fixtures. In young children, lead can cause nervous system damage and learning problems. |
| Nitrogen oxides: Nitrogen Oxides are released into the air by burning fuels such as gasoline and coal. When nitrogen oxides combine with VOCs, they can cause breathing difficulty in people who have asthma, coughs in children, and general illness in your respiratory system. |
| Ozone: Ozone is released by motor vehicles, industries, burning coal, gasoline, and other fossil fuels, and in the chemicals that are in hairspray and paints. When ozone is close to the ground (ground level ozone) it can cause chest pain, irritated respiratory tract, or persistent cough, can make you unable to take deep breaths, and can make you more likely to get lung infections. |
| Particulate matter (PM): PM, little particles of pollution, is released by cars, trucks, and buses that are burning diesel fuel, fertilizers, pesticides, road construction, steel making, mining, and turning on fire places and wood stoves. When PMs mix with air particles and get breathed in by something, they get stuck in the lung tissue. There they can cause increased respiratory disease and lung damage. |
| Sulfur dioxides: Sulfur dioxides are released by burning coal, paper production, and melting metal. Sulfur dioxide can harm vegetation, harm metals, and cause lung problems, which include breathing problems and permanent lung damage. |
| Volatile organic compounds (VOCs): VOCs are released into the air by burning gasoline, wood, coal, or natural gas, solvents, paints, glues, and other products that are used at work or at home. |
There are a lot of similarities in all of these pollutants. Most of the pollutants are from automobiles. Automobiles release harmful
smoke into the air, which causes acid rain. Coal, oil, and gasoline are also some of the most common causes of all of the pollutants. If people reduce the amount of these things that they release into the air, then there will be less pollutants. Some of the most common health problems are breathing problems, nervous system problems, and lung problems.
Air Pollutant % that mobile sources contribute to acid rain % that other sources contribute to acid rain Volatile organic compound 37% 63% Nitrogen oxide 49% 51% Carbon monoxide 81% 19% Particulate matter 27% 73%
The table above shows that the biggest air pollutant that mobile sources contribute to acid rain is carbon monoxide. Of all of the carbon monoxide releases that contribute to acid rain, 81% of them come from mobile sources. The biggest other source is particulate matter, little particles of pollution that are released into the air by cars, trucks, and buses that are burning diesel fuel, fertilizers, pesticides, road construction, steel making, mining, and turning on fire places and wood stoves. 73% of the non-mobile sources that contribute to acid rain are caused by the release of particulate matter. The table above shows how much mobile and other sources of pollution can make acid rain more of a problem. Seeing that carbon monoxide and particulate matter are the leading sources of pollution, by cutting down on these, acid rain will not be as much of a problem.
What can you do?
There are many ways that people can stop pollution. One major way is to reduce the amount of trips that you take in your car. Another way that a lot of our pollution is caused is by creating electrical energy. When electricity is created, fuels are usually burned, and this causes the pollution, which causes acid rain. The generation of electric power produces more pollution than any other industry in the United States. Burning coal and other fossil fuels causes most of our pollution. This is why in some places around the world, acid rain is monitored very closely. In 1998, data shows that by using electricity, the pollution that comes with it was responsible for 67% of the sulfur dioxide emissions that caused acid rain that year. Every time that you turn on the lights, that causes the pollution that causes acid rain. Even doing little things that you may think don’t cause pollution sometimes really do. Some things that you can do to make acid rain less of a problem are:
In Your Home
| Only run the dishwasher with a full load |
| Only run the washing machine with a full load |
| Turn off the lights in empty rooms or when you will be away from home |
| Turn off the hot water tank when you will be gone for a long period of time |
| Turn down the heat at night and when you will not be home for the night |
| Don’t use your air conditioner as much |
| Install fluorescent light bulbs instead of incandescent light bulbs |
| Try to reduce, reuse, and recycle as often as you can |
| Try not to burn a fire as often as you usually do |
In the yard
| Keep the pool cover on the pool whenever you are not using it |
Transportation
| When you are going to work, you could walk, ride your bike, or take a bus | |
| Car-pool to a place with someone else | |
| For alternate fuels, try ethanol, propane, or natural gas | |
| Take the train or a bus for long trips | |
| Limit the amount of long trips you take in your car | |
| Make sure that your vehicle’s air conditioning system isn’t leaking | |
| Try not to overflow the gas tank | |
| Make sure that you are traveling at high speeds only when you need to
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Acid rain hurts many things. Some things that are being hurt by acid rain are trees, animals, and most of all, sea life. People can help stop acid rain by not polluting the air. When the chemicals in the air turn into a gas and evaporate, they mix with the water vapor, and cause acid rain. Even kids can help prevent this pollution by using less electricity and using transportation that is friendly to the environment.
The Greenhouse Effect
This section provides an overview of the earth's atmospheric "greenhouse effect" by briefly exploring the atmospheres of nearby planets and discussing our atmosphere's greenhouse gases. The general concepts found in this section include the following:
This section includes two classroom activities. |
Introduction
The Goldilocks Principle can be summed up neatly as "Venus is too hot, Mars is too cold, and Earth is just right." The fact that Earth has an average surface temperature comfortably between the boiling point and freezing point of water, and thus is suitable for our sort of life, cannot be explained by simply suggesting that our planet orbits at just the right distance from the sun to absorb just the right amount of solar radiation. Our moderate temperatures are also the result of having just the right kind of atmosphere. A Venus-type atmosphere would produce hellish, Venus-like conditions on our planet; a Mars atmosphere would leave us shivering in a Martian-type deep freeze.
Instead, parts of our atmosphere act as an insulating blanket of just the right thickness, trapping sufficient solar energy to keep the global average temperature in a pleasant range. The Martian blanket is too thin, and the Venusian blanket is way too thick! The 'blanket' here is a collection of atmospheric gases called 'greenhouse gases' based on the idea that the gases also 'trap' heat like the glass walls of a greenhouse do.
These gases, mainly water vapor (
), carbon dioxide (
), methane (
), and nitrous oxide (
), all act as effective global insulators. To understand why, it's important to understand a few basic facts about solar radiation and the structure of atmospheric gases.
Solar Radiation
The sun radiates vast quantities of energy into space, across a wide spectrum of wavelengths.
Most of the radiant energy from the sun is concentrated in the visible and near-visible parts of the spectrum. The narrow band of visible light, between 400 and 700 nm, represents 43% of the total radiant energy emitted. Wavelengths shorter than the visible account for 7 to 8% of the total, but are extremely important because of their high energy per photon. The shorter the wavelength of light, the more energy it contains. Thus, ultraviolet light is very energetic (capable of breaking apart stable biological molecules and causing sunburn and skin cancers). The remaining 49 - 50% of the radiant energy is spread over the wavelengths longer than those of visible light. These lie in the near infrared range from 700 to 1000 nm; the thermal infrared, between 5 and 20 microns; and the far infrared regions. Various components of earth's atmosphere absorb ultraviolet and infrared solar radiation before it penetrates to the surface, but the atmosphere is quite transparent to visible light.
Absorbed by land, oceans, and vegetation at the surface, the visible light is transformed into heat and re-radiates in the form of invisible infrared radiation. If that was all there was to the story, then during the day earth would heat up, but at night, all the accumulated energy would radiate back into space and the planet's surface temperature would fall far below zero very rapidly. The reason this doesn't happen is that earth's atmosphere contains molecules that absorb the heat and re-radiate the heat in all directions. This reduces the heat radiated out to space. Called 'greenhouse gases' because they serve to hold heat in like the glass walls of a greenhouse, these molecules are responsible for the fact that the earth enjoys temperatures suitable for our active and complex biosphere.
Greenhouse Gases
Carbon dioxide () is one of the greenhouse gases. It consists of one carbon atom with an oxygen atom bonded to each side. When its atoms are bonded tightly together, the carbon dioxide molecule can absorb infrared radiation and the molecule starts to vibrate. Eventually, the vibrating molecule will emit the radiation again, and it will likely be absorbed by yet another greenhouse gas molecule. This absorption-emission-absorption cycle serves to keep the heat near the surface, effectively insulating the surface from the cold of space.
Carbon dioxide, water vapor (), methane (), nitorus oxide (), and a few other gases are greenhouse gases. They all are molecules composed of more than two component atoms, bound loosely enough together to be able to vibrate with the absorption of heat. The major components of the atmosphere (
and 
) are two-atom molecules too tightly bound together to vibrate and thus they do not absorb heat and contribute to the greenhouse effect.
Greenhouse Effect
Atmospheric scientists first used the term 'greenhouse effect' in the early 1800s. At that time, it was used to describe the naturally occurring functions of trace gases in the atmosphere and did not have any negative connotations. It was not until the mid-1950s that the term greenhouse effect was coupled with concern over climate change. And in recent decades, we often hear about the greenhouse effect in somewhat negative terms. The negative concerns are related to the possible impacts of an enhanced greenhouse effect. This is covered in more detail in the Global Climate Change section of this Web site. It is important to remember that without the greenhouse effect, life on earth as we know it would not be possible.
While the earth's temperature is dependent upon the greenhouse-like action of the atmosphere, the amount of heating and cooling are strongly influenced by several factors just as greenhouses are affected by various factors.
In the atmospheric greenhouse effect, the type of surface that sunlight first encounters is the most important factor. Forests, grasslands, ocean surfaces, ice caps, deserts, and cities all absorb, reflect, and radiate radiation differently. Sunlight falling on a white glacier surface strongly reflects back into space, resulting in minimal heating of the surface and lower atmosphere. Sunlight falling on a dark desert soil is strongly absorbed, on the other hand, and contributes to significant heating of the surface and lower atmosphere. Cloud cover also affects greenhouse warming by both reducing the amount of solar radiation reaching the earth's surface and by reducing the amount of radiation energy emitted into space.
Scientists use the term albedo to define the percentage of solar energy reflected back by a surface. Understanding local, regional, and global albedo effects is critical to predicting global climate change.
Concluding Thoughts
The ability of certain trace gases to be relatively transparent to incoming visible light from the sun, yet opaque to the energy radiated from the earth is one of the best understood processes in the atmospheric sciences. This phenomenon, the greenhouse effect, is what makes the earth habitable for life. For students to truly understand the nature and importance of the greenhouse effect, they should understand the answers to these questions:
- What is a greenhouse and how does it work?
- How is the earth's atmosphere similar to a greenhouse?
- What factors influence the function of a greenhouse?
- What is albedo and how is it related to understanding global climate change?
- What are the limitations in comparing the earth's atmosphere to a greenhouse?
