Acid rain is rain that has been made acidic by certain pollutants in the air. Acid rain is a type of acid deposition,
which can appear in many forms. Wet deposition is rain, sleet, snow, or
fog that has become more acidic than normal. Dry deposition is another
form of acid deposition, and this is when gases and dust particles
become acidic. Both wet and dry deposition can be carried by the wind,
sometimes for very long distances. Acid deposition in wet and dry forms
falls on buildings, cars, and trees and can make lakes acidic. Acid
deposition in dry form can be inhaled by people and can cause health
problems in some people.
What is acidity?
Acidic
and basic are two ways that we describe chemical compounds. Acidity is
measured using a pH scale. A pH scale runs from zero (the most acidic)
to 14 (the most basic or alkaline). A substance that is neither basic or acidic is called "neutral", and this has a pH of 7.
Sources of Acid RainAcid rain is caused by a chemical reaction that begins when compounds
like sulfur dioxide and nitrogen oxides are released into the air.
These substances can rise very high into the atmosphere, where they mix
and react with water, oxygen, and other chemicals to form more acidic pollutants,
known as acid rain. Sulfur dioxide and nitrogen oxides dissolve very
easily in water and can be carried very far by the wind. As a result,
the two compounds can travel long distances where they become part of
the rain, sleet, snow, and fog that we experience on certain days.
Human
activities are the main cause of acid rain. Over the past few decades,
humans have released so many different chemicals into the air that they
have changed the mix of gases in the atmosphere. Power plants release
the majority of sulfur dioxide and much of the nitrogen oxides when
they burn fossil fuels, such as coal, to produce electricity. In addition, the exhaust from cars, trucks, and buses releases nitrogen oxides and sulfur dioxide into the air. These pollutants cause acid rain.
Acid Rain is Caused by Reactions in the Environment
Nature depends on balance, and although some rain is naturally acidic, with a pH level of around 5.0, human activities have made it worse. Normal precipitation—such as rain, sleet, or snow—reacts with alkaline chemicals, or non-acidic materials, that can be found in air, soils, bedrock, lakes, and streams. These reactions usually neutralize
natural acids. However, if precipitation becomes too acidic, these
materials may not be able to neutralize all of the acids. Over time,
these neutralizing materials can be washed away by acid rain. Damage to
crops, trees, lakes, rivers, and animals can result. |
Acid Rain Can Cause Health Problems in People
Air
pollution like sulfur dioxide and nitrogen oxides can cause respiratory
diseases, or can make these diseases worse. Respiratory diseases like asthma or chronic bronchitis
make it hard for people to breathe. The pollution that causes acid rain
can also create tiny particles. When these particles get into people’s
lungs, they can cause health problems, or can make existing health
problems worse. Also, nitrogen oxides cause ground-level ozone. This ground-level ozone causes respiratory problems, like pneumonia and bronchitis,
and can even cause permanent lung damage. The health effects that
people have to worry about are not caused by the acid rain, but are
caused when people breathe in these tiny particles or ozone. Swimming
in an acidic lake or walking in an acidic puddle is no more harmful to
people than swimming or walking in clean water.
Acid Rain Harms Forests
Acid
rain can be extremely harmful to forests. Acid rain that seeps into the
ground can dissolve nutrients, such as magnesium and calcium, that
trees need to be healthy. Acid rain also causes aluminum
to be released into the soil, which makes it difficult for trees to
take up water. Trees that are located in mountainous regions at higher
elevations, such as spruce or fir trees, are at greater risk because
they are exposed to acidic clouds and fog, which contain greater
amounts of acid than rain or snow. The acidic clouds and fog strip
important nutrients from their leaves and needles. This loss of
nutrients makes it easier for infections, insects, and cold weather to
damage trees and forests.
Acid Rain Damages Lakes and StreamsWithout
pollution or acid rain, most lakes and streams would have a pH level
near 6.5. Acid rain, however, has caused many lakes and streams in the
northeast United States and certain other places to have much lower pH
levels. In addition, aluminum that is released into the soil eventually
ends up in lakes and streams. Unfortunately, this increase in acidity
and aluminum levels can be deadly to aquatic wildlife, including phytoplankton,
mayflies, rainbow trout, small mouth bass, frogs, spotted salamanders,
crayfish, and other creatures that are part of the food web.
This
problem can become much worse during heavy downpours of rain or when
the snow begins to melt in the spring. These types of events are known
as episodic acidification.
Acid Rain Damages Buildings and Objects
Acid
rain can also have a damaging effect on many objects, including
buildings, statues, monuments, and cars. The chemicals found in acid
rain can cause paint to peel and stone statues to begin to appear old
and worn down, which reduces their value and beauty. |
Now that you know why acid rain is a problem, you might be wondering what’s being done to control it. Regulations and new technologies are helping reduce acid rain.
EPA’s Acid Rain Program
Power
plants generate the electricity we use every day. Unfortunately, power
plants also produce large amounts of nitrogen oxides and sulfur
dioxide—the pollutants that cause acid rain—when they burn fossil
fuels, especially coal, to produce energy. Congress passed a law called
the Clean Air Act Amendments of 1990, and this law said that EPA should start the Acid Rain Program. The program limits, or puts a cap on, the amount of sulfur dioxide that power plants can release into the air and issues allowances
to the power plants to cover their sulfur dioxide emissions. It also
reduces the amount of nitrogen oxides that power plants can release.
Reducing Pollution
Scientists
have found different ways to reduce the amount of sulfur dioxide
released from coal-burning power plants. One option is to use coal that
contains less sulfur. Another option is to “wash” the coal to remove
some of the sulfur. The power plant can also install equipment called
scrubbers, which remove the sulfur dioxide from gases leaving the
smokestack. Because nitrogen oxides are created in the process of
burning coal and other fossil fuels, some power plants are changing the
way they burn coal.
Other Sources of Energy
A
great way to reduce acid rain is to produce energy without using fossil
fuels. Instead, people can use renewable energy sources, such as solar
and wind power. Renewable energy sources help reduce acid rain because
they produce much less pollution. These energy sources can be used to
power machinery and produce electricity.
Cleaner Cars
Cars
and trucks are major sources of the pollutants that cause acid rain.
While one car alone does not produce much pollution, all the cars on
the road added together create lots of pollution. Therefore, car
manufacturers are required to reduce the amount of nitrogen oxides and
other pollutants released by new cars. One type of technology used in
cars is called a catalytic converter. This piece of equipment has been
used for over 20 years to reduce the amount of nitrogen oxides released
by cars. Some new cars can also use cleaner fuels, such as natural gas.
Cars that produce less pollution and are better for the environment are
often labeled as low emissions vehicles.
Government
agencies and scientists are not the only ones that can take action to
stop acid rain. You can become part of the solution, too!
Understand the Problem
The
first step you can take to help control acid rain is to understand the
problem and its solutions. Now that you have learned about this
environmental issue, you can tell others about it. By telling your
classmates, parents, and teachers about what you learned on this site,
you can help educate them about the problem of acid rain. You CAN make
a difference!
Conserve Energy
Since energy
production creates large amounts of the pollutants that cause acid
rain, one important step you can take is to conserve energy. You can do
this in a number of ways:
- Turn off lights, computers, televisions, video games, and other electrical equipment when you're not using them.
- Encourage
your parents to buy equipment that uses less electricity, including
lights, air conditioners, heaters, refrigerators, and washing machines.
Such equipment might have the Energy Star label.
- Try to limit the use of air conditioning.
- Ask your parents to adjust the thermostat (the device used to control the temperature in your home) when you go on vacation.
Minimize the Miles
Driving
cars and trucks also produces large amounts of nitrogen oxides, which
cause acid rain. To help cut down on air pollution from cars, you can
carpool or take public transportation, such as buses and trains. Also,
ask your parents to walk or bike with you to a nearby store or friend’s
house instead of driving.
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