Monday, May 15, 2017

Scientists Hunt for Acid Rain and Methane in Wetlands


Depending on how you look at it, something good can always come out of something bad. That's actually the case in a new study on greenhouse gases by NASA scientists and others. The researchers discovered that acid rain inhibits a swampland bacteria from producing methane, a greenhouse gas. 

Animation above: This movie from the U.S. Environmental Protection Agency highlights the science of acid rain, and its effects. Click arrow on bottom right to move to next image. Credit: U.S. EPA

Methane, a gas that contributes to warming our planet, is produced by natural processes and human activities. Increased amounts of methane and other greenhouse gases in our atmosphere are warming the Earth beyond its average temperature. 

Carbon, heat and moisture are known to influence methane production by members of the Archaea, single-celled creatures. Under normal conditions, these microbes consume organic carbon in the soil for energy and release methane as a byproduct. Wetlands provide an ideal environment for these microbes. When acid rain drops sulfate onto wetlands, another type of bacteria, ones that reduce sulfate are able to outcompete the Archea, limiting the total production of methane. 

Wetlands may produce as much as 320 million tons of methane annually but only about half of that, or 160 million tons, is ultimately released to the atmosphere. The other 160 million tons never makes it to the atmosphere because it is destroyed via oxidation as it moves from wet soils below the water table through dry soil to the surface. Despite substantial oxidation, natural wetlands remain the single largest source of methane emission accounting for about one third of the global annual total methane.

Image of a seasonal wetland in Spring
Image to right: Inland wetlands are most common on floodplains along rivers and streams. Scientists have discovered that acid rain actually inhibits a bacteria found in swamplands from producing methane, a greenhouse gas. Inland wetlands include marshes and wet meadows dominated by herbaceous plants, swamps dominated by shrubs, and wooded swamps dominated by trees. Credit: U.S. EPA Region 1/Leo Kenney

"It's a complicated process because multiple factors at microscopic to global scales interact in these processes," said Elaine Matthews, a scientist at NASA's Goddard Institute for Space Studies (GISS), New York. Matthews is co-author of the study on acid rain and methane in wetlands. "The maximum emission of methane from wetlands occurs when conditions are warm and wet, while the biggest reduction in methane emissions is achieved when the location of wetlands, sulfates contained in acid rain, high temperatures and substantial precipitation all come together, to reduce optimal methane emissions from wetlands." These factors vary over time and space. 

According to Matthews, by 1960 these counteracting processes probably reduced methane emission from wetlands to pre-industrial levels. However, methane emission is predicted to rise in response to 21st century climate change faster than sulfate suppression increases, meaning that wetland emissions of methane will begin to rise above those occurring before industrial sulfate pollution began.

In order to determine how the acid rain interacts with methane in wetlands, lead author of the study, Dr. Vincent Gauci of Open University, United Kingdom and his colleagues took to the field. In the U.S., Britain and Sweden they attempted to determine if low levels of sulfate, like those in acid rain, affected methane emissions in wetlands. They applied several quantities of sulfate, similar to the amounts found in acid rain, to the wetlands they were studying. The results, acquired over several years, showed that these low doses of sulfate suppressed methane emissions between 30-40 percent. 

Image of a Riparian wetland
Image to left: Coastal wetlands in the United States, as their name suggests, are found along the Atlantic, Pacific, Alaskan, and Gulf coasts. They are closely linked to our nation's estuaries, where sea water mixes with fresh water to form an environment of varying salinities. The salt water and the fluctuating water levels (due to tidal action) combine to create a rather difficult environment for most plants. Credit: U.S. EPA Region 8/Paul McIver

Matthews and climate experts expect methane emissions to increase over the 21st century in response to climate change. They also predict that sulfate levels in rainfall will increase, especially in Asia. The authors have attempted to predict how this ecological balancing act will turn out for the 21st century. 

"When we used all the field data with the NASA computer models and applied it to a global scale, it shows that the effect of acid rain from 1960 to 2030 actually reduces methane emissions to below pre-industrial levels," said Gauci. The effect more than compensates for the increase in methane emission that would be expected as wetlands become warmer. In this way, acid rain acts like a temporary lid on the largest methane source. 

Gauci is cautious about the image presented by acid rain. "We wouldn't want to give the impression that acid rain is a good thing - it has long been known that acid rain damages natural ecosystems such as forests, grasslands, rivers and lakes. But our findings suggest that small amounts of pollution may also have a positive effect in suppressing this important greenhouse gas. Moreover, they point to how complex the Earth system is," he noted.

Graphic image of a wetland food web
Image to right: Wetlands are among the most productive ecosystems in the world, comparable to rain forests and coral reefs. An immense variety of species of microbes, plants, insects, amphibians, reptiles, birds, fish, and mammals can be part of a wetland ecosystem. Physical and chemical features such as climate, landscape shape (topology), geology, and the movement and abundance of water help to determine the plants and animals that inhabit each wetland. The complex, dynamic relationships among the organisms inhabiting the wetland environment are referred to as food webs. Credit: U.S. EPA/ Mark Sharp

Most attention has been given to the negative aspects of pollution but if scientists want to understand all of Earth's complexities and make better predictions of future climate we need to understand interactions among a suite of processes that are not always well understood. "That's not to say that acid rain is a good thing. Rather this study illuminates really well how we have to work to understand relationships among microscopic-to-global processes, at the same time that we attempt to represent them in relatively simple ways," Matthews said. 

While sulfate deposition results almost exclusively from human activities, it may serve to delay impacts from the increase of at least one greenhouse gas, methane, in the short term. The study recently appeared in the Proceedings of the National Academy of Sciences.

NASA's Science Directorate works to improve the lives of all humans through the exploration and study of Earth's system, the solar system and the Universe. 

Sunday, March 26, 2017

Acid Rain : The Causes, History, and Effects of Acid Rain

What Is Acid Rain?

Acid rain is made up of water droplets that are unusually acidic because of atmospheric pollution, most notably the excessive amounts of sulfur and nitrogen released by cars and industrial processes. Acid rain is also called acid deposition because this term includes other forms of acidic precipitation such as snow.

Acidic deposition occurs in two ways: wet and dry. Wet deposition is any form of precipitation that removes acids from the atmosphere and deposits them on the Earth’s surface.

Dry deposition polluting particles and gases stick to the ground via dust and smoke in the absence of precipitation. This form of deposition is dangerous, however, because precipitation can eventually wash pollutants into streams, lakes, and rivers.

Acidity itself is determined based on the pH level of the water droplets. PH is the scale measuring the amount of acid in the water and liquid. The pH scale ranges from 0 to 14 with a lower pH being more acidic while a high pH is alkaline; seven is neutral. Normal rain water is slightly acidic and has a pH range of 5.3-6.0. Acid deposition is anything below that range. It is also important to note that the pH scale is logarithmic and each whole number on the scale represents a 10-fold change.

Today, acid deposition is present in the northeastern United States, southeastern Canada, and much of Europe including portions of Sweden, Norway, and Germany.

In addition, parts of South Asia, South Africa, Sri Lanka, and Southern India are all in danger of being impacted by acid deposition in the future.

Causes and History of Acid Rain

Acid deposition can be causes by natural sources like volcanoes, but it is mainly caused by the release of sulfur dioxide and nitrogen oxide during fossil fuel combustion.

When these gases are discharged into the atmosphere, they react with the water, oxygen, and other gases already present there to form sulfuric acid, ammonium nitrate, and nitric acid. These acids then disperse over large areas because of wind patterns and fall back to the ground as acid rain or other forms of precipitation.

The gases most responsible for acid deposition are a byproduct of electric power generation and the burning of coal. As such, man-made acid deposition began becoming a significant issue during the Industrial Revolution and was first discovered by a Scottish chemist, Robert Angus Smith, in 1852. In that year, he discovered the relationship between acid rain and atmospheric pollution in Manchester, England.

Although it was discovered in the 1800s, acid deposition did not gain significant public attention until the 1960s, and the term acid rain was coined in 1972. Public attention further increased in the 1970s when the New York Times published reports about problems occurring in the Hubbard Brook Experimental Forest in New Hampshire.

Effects of Acid Rain

After studying the Hubbard Brook Forest and other areas, researchers have found several important impacts of acid deposition on both natural and man-made environments.

Aquatic settings are the most clearly impacted by acid deposition though because acidic precipitation falls directly into them. Both dry and wet deposition also runs off of forests, fields, and roads and flows into lakes, rivers, and streams.

As this acidic liquid flows into larger bodies of water, it is diluted, but over time, acids can accrue and lower the overall pH of the body of water. Acid deposition also causes clay soils to release aluminum and magnesium further lowering the pH in some areas. If the pH of a lake drops below 4.8, its plants and animals risk death. It is estimated that around 50,000 lakes in the United States and Canada have a pH below normal (about 5.3 for water). Several hundred of these have a pH too low to support any aquatic life.

Aside from aquatic bodies, acid deposition can significantly impact forests.

As acid rain falls on trees, it can make them lose their leaves, damage their bark, and stunt their growth. By damaging these parts of the tree, it makes them vulnerable to disease, extreme weather, and insects. Acid falling on a forest’s soil is also harmful because it disrupts soil nutrients, kills microorganisms in the soil, and can sometimes cause a calcium deficiency. Trees at high altitudes are also susceptible to problems induced by acidic cloud cover as the moisture in the clouds blankets them.

Damage to forests by acid rain is seen all over the world, but the most advanced cases are in Eastern Europe. It’s estimated that in Germany and Poland, half of the forests are damaged, while 30% in Switzerland have been affected.

Finally, acid deposition also has an impact on architecture and art because of its ability to corrode certain materials. As acid lands on buildings (especially those constructed with limestone) it reacts with minerals in the stones sometimes causing them to disintegrate and wash away. Acid deposition can also cause concrete to deteriorate, and it can corrode modern buildings, cars, railroad tracks, airplanes, steel bridges, and pipes above and below ground.

What's Being Done?

Because of these problems and the adverse effects air pollution has on human health, a number of steps are being taken to reduce sulfur and nitrogen emissions. Most notably, many governments are now requiring energy producers to clean smoke stacks by using scrubbers which trap pollutants before they are released into the atmosphere and catalytic converters in cars to reduce their emissions. Additionally, alternative energy sources are gaining more prominence today, and funding is being given to the restoration of ecosystems damaged by acid rain worldwide.

Wednesday, March 22, 2017

Acid Rain: Scourge of the Past or Trend of the Present?

Acid rain. It was a problem that largely affected U.S. eastern states. It began in the 1950s when Midwest coal plants spewed sulfur dioxide and nitrogen oxides into the air, turning clouds--and rainfall--acidic.

As acid rain fell, it affected everything it touched, leaching calcium from soils and robbing plants of important nutrients. New England's sugar maples were among the trees left high and dry.
Acid rain also poisoned lakes in places like New York's Adirondack Mountains, turning them into a witches' brew of low pH waters that killed fish and brought numbers of fish-eating birds like loons to the brink.

Then in 1970, the U.S. Congress imposed acid emission regulations through the Clean Air Act, strengthened two decades later in 1990. By the 2000s, sulfate and nitrate in precipitation had decreased by some 40 percent.

Has acid rain now blown over? Or is there a new dark cloud on the horizon?

In findings recently published in the journal Water Resources Research, Charles Driscoll of Syracuse University and the National Science Foundation's (NSF) Hubbard Brook Long Term Ecological Research (LTER) site in New Hampshire reports that the reign of acid rain is far from over.

It's simply "shape-shifted" into a different form.

Hubbard Brook is one of 26 NSF LTER sites across the nation and around the world in ecosystems from deserts to coral reefs to coastal estuaries.

Co-authors of the paper are Afshin Pourmokhtarian of Syracuse University, John Campbell of the U.S. Forest Service in Durham, N.H., and Katharine Hayhoe of Texas Tech University. Pourmokhtarian is the lead author.

Acid rain was first identified in North America at Hubbard Brook in the mid-1960s, and later shown to result from long-range transport of sulfur dioxide and nitrogen oxides from power plants.
Hubbard Brook research influenced national and international acid rain policies, including the 1990 Clean Air Act amendments.

Researchers at Hubbard Brook have continued to study the effects of acid rain on forest growth and on soil and stream chemistry.

Long-term biogeochemical measurements, for example, have documented a decline in calcium levels in soils and plants over the past 40 years. Calcium is leaching from soils that nourish trees such as maples. The loss is primarily related to the effects of acid rain (and acid snow).

Now, Hubbard Brook LTER scientists have discovered that a combination of today's higher atmospheric carbon dioxide (CO2) level and its atmospheric fallout is altering the hydrology and water quality of forested watersheds--in much the same way as acid rain.

"It's taken years for New England forests, lakes and streams to recover from the acidification caused by atmospheric pollution," says Saran Twombly, NSF program director for long-term ecological research.

"It appears that these forests and streams are under threat again. Climate change will likely return them to an acidified state. The implications for these environments, and for humans depending on them, are severe."

Climate projections indicate that over the 21st century, average air temperature will increase at the Hubbard Brook site by 1.7 to 6.5 degrees Celsius, with increases in annual precipitation ranging from 4 to 32 centimeters above the average from 1970-2000.

Hubbard Brook scientists turned to a biogeochemical model known as PnET-BGC to look at the effects of changes in temperature, precipitation, solar radiation and atmospheric CO2 on major elements such as nitrogen in forests.

The model is used to evaluate the effects of climate change, atmospheric deposition and land disturbance on soil and surface waters in northern forest ecosystems.

It was created by linking the forest-soil-water model PnET-CN with a biogeochemical sub-model, enabling the incorporation of major elements like calcium, nitrogen, potassium and others.

The results show that under a scenario of future climate change, snowfall at Hubbard Brook will begin later in winter, snowmelt will happen earlier in spring, and soil and stream waters will become acidified, altering the quality of water draining from forested watersheds.

"The combination of all these factors makes it difficult to assess the effects of climate change on forest ecosystems," says Driscoll.

"The issue is especially challenging in small mountain watersheds because they're strongly influenced by local weather patterns."

The Hubbard Brook LTER site has short, cool summers and long, cold winters. Its forests are made up of northern hardwood trees like sugar maples, American beeches and yellow birches. Conifers--mostly balsam firs and red spruces--are more abundant at higher elevations.

The model was run for Watershed 6 at Hubbard Brook. "This area has one of the longest continuous records of meteorology, hydrology and biogeochemistry research in the U.S.," says Pourmokhtarian.
The watershed was logged extensively from 1910 to 1917; it survived a hurricane in 1938 and an ice storm in 1998.

It may have more to weather in the decades ahead.

The model showed that in forest watersheds, the legacy of an accumulation of nitrogen, a result of acid rain, could have long-term effects on soil and on surface waters like streams.

Changes in climate may also alter the composition of forests, says Driscoll. "That might be very pronounced in places like Hubbard Brook. They're in a transition forest zone between northern hardwoods and coniferous red spruces and balsam firs."

The model is sensitive to climate that is changing now--and climate changes expected to occur in the future. 

In scenarios that result in water stress, such as decreases in summer soil moisture due to shifts in hydrology, the end result is further acidification of soil and water.

Gardens: The Surprising Benefits of Acid Rain

Showing the ecological devastation that sulphuric acid raining down from the sky had on forests and waterways across the world. Yet the decline over the past 30 years in the emissions of toxic sulphur dioxide in air pollution that once caused this phenomenon has had an enduring impact on British soils, with far-reaching effects on agriculture and even our gardens — and not always a positive one.

Sulphur is a key plant nutrient vital to healthy growth, but UK soils are naturally deficient in this essential mineral. Back in the 1980s this was of little concern to growers as these levels were continually topped up by “atmospheric deposition”, ie acid rain.

Fast forward to 2016 and this is increasingly worthy of attention. One small survey conducted over 2014 and 2015, for example, found that only 13% of the crops sampled showed sulphur levels in the “normal” range, with the rest registering as low or slightly low. This is a concern as inadequate sulphur levels have been shown to slash farm yields of some (but admittedly not all) crops by as much as 50%. Surprising as it may seem, even acid rain clouds can have a silver lining.

As many plants also use sulphur pulled up from the soil to generate defence compounds to help ward off pests and diseases, this deficiency can also result in weak, vulnerable crops that require higher pesticide applications. These defence compounds also happen to be the exact same chemicals that give vegetables, like onions, garlic, broccoli and sprouts, their characteristic flavour and associated health benefits. Heard about the antioxidants in broccoli and garlic? It’s the sulphur chemicals, derived from the soil, that are doing the work.

While this effect is likely to be greater in agricultural soils, where crops are constantly taking sulphur from the soil only to be harvested and removed from the site, this can be an issue even in garden soils. Take lawns for example: years of continual mowing and disposal of the grass clippings essentially mimics that of agriculture – acting like a pump on a conveyor belt to suck up the sulphur.

If you suspect your soil is sulphur-deficient, there is a simple solution that offers all of the benefits without the damaging acidity: Epsom salts. This naturally occurring mineral combines both sulphur and another essential plant nutrient, magnesium, in a double whammy and can be bought for minimal cost at any garden centre. Simply sprinkle over the ground according to package directions for higher yields of tastier and more nutritious crops.

Acid Deposition : Acid Rain, Mist and Fog

Acid deposition is a general name for a number of phenomena, namely acid rain, acid fog and acid mist. This means it can imply both wet and dry (gaseous) precipitation. Acid deposition is a rather well known environmental problem, for example acid fog killed several thousand people in London in 1952.

Acid deposition is concerned with long-range rather than local effects. Pollutants are mixed in the atmosphere and therefore usually cannot be attributed to any local source. Pollutants are generally more dispersed and of lower concentrations than local ground level pollutants.

Acid deposition typically has a pH below 4, but this may be as low as 1.5 under seriously acidic conditions. It primarily consists of two types of compounds, namely sulphuric acid (H2SO4) and nitric acid (HNO3).

Sulphuric acid is formed by conversion of sulphur dioxide emitted from power stations, melting processes, home fires, car exhausts and other sources. It contributes about 70% to the overall acidity of deposition.

Reaction mechanism: SO3 + H2O -> H2SO4

Nitric acid is formed from nitrogen oxide (NOx) emissions from fossil fuel combustion. It contributes about 30% to the overall acidity of deposition.

Reaction mechanism: NO2 + OH- -> HNO3

Acid rain has various environmental and health effects, for example:
- Chocking plant leave pores (forest loss)
- Corroding stone and brick walls of buildings and monuments
- Corroding paper and rubber objects
- Altering soil chemistry (soil acidification, loss of plant nutrients)
- Altering the chemical balance of lakes and streams
- Disrupting fish gill operation (fish deaths)
- Deteriorating human breathing disorder (asthma, bronchitis, lung oedema)

When people die of acid deposition it is usually caused by access mucous production in the bronchi, leading to chocking from a lack of oxygen, or a heart attack.

Acid deposition in various countries

Acid deposition is a transboundary environmental problem. This basically means that emissions in one country may affect forests and structures in a neighbouring country. Therefore, international agreements were made, such as the Sulphur emissions Reduction Protocol (1979) and the Convention on Long-Range Transboundary Air Pollution (1983).

Some examples of countries that experience(d) acid deposition, either from their own sources or from transboundary air pollution:
- Britain: smog episodes around London, particularly in 1952
- Germany: acid mists in central Germany and the Black Forest area, acid cold smog from Poland and former Czechoslovakia in 1985
- Greece: intense industrialization in the Athens area causes deterioration of ancient monuments such as the Parthenon by acid deposition
- Italy: damage to Venice structures from acid deposition
- Scandinavia: 15% of acid rain caused by Great-Britain
- Scotland: episodes of black acid snow in the Cairngorm mountains in 1984
- The Netherlands: corrosion of bells of the Utrecht Dom tower since 1951
- United States: acid rains disrupts forest ecosystems and pollutes surface waters, industrial fossil fuel combustion processes are adapted to prevent sulphur dioxide emissions.

Tuesday, March 7, 2017

Positive and Negative Impact of Acid Rain on Humans and the Environment.

Why acid rain is harmful to humans and the environment.
1) Acid rain can contribute to respiratory diseases and exacerbate existing medical conditions. For example, the nitrogen oxide in acid rain leads to the creation of ground-level ozone, which in turn can contribute to respiratory diseases such as pneumonia and bronchitis.
2) Acid rain can increase levels of aluminum in the soil, which prevents trees from taking up adequate water. What is even more troubling is that the higher levels of aluminum can eventually end up in streams and rivers. This in turn can prove fatal to aquatic as well as forest wild-life.
3) Acid rain has contributed to lower pH levels in streams and rivers across the United States, especially in the Northeast region. Most bodies of water have pH levels of about 6.5. Lower pH levels mean that the water is more acidic rather than alkaline. The Environmental Protection Agency recommends that pH levels of water be between 6.5 to 8.5 for drinking purposes. Bodies of water with lower pH levels may have higher iron and sulfur deposits, which in turn can prove harmful to the health of wildlife and humans. Sensitive species of wildlife may experience higher than normal mortality rates if the pH levels of water move away from the optimum range.
The advantages of acid rain.
It has recently come to the attention of the science community that acid rain may have a positive impact on humans and the environment.
As a rule, carbon dioxide and methane contribute significantly to what is considered global warming. However, the sulfur dioxide in acid rain suppresses some portion of methane production in the atmosphere. Methane results from bacteria breaking down organic compounds, and the sulfur in acid rain appears to suppress up to 30 or 40% of methane production in wetlands areas. For example, tests by NASA's Goddard Space Flight Center show that the sulfur in acid rain will continue to suppress methane production until at least 2030.
Other studies have shown that a rise in temperature, along with greater concentrations of nitrogen in the atmosphere, can contribute to higher growth in forests. For example, the nitrogen in acid rain allows the trees to store more carbon. This process is called carbon sequestration and is quite beneficial: higher carbon reserves allow a tree to produce the optimum level of sugars and carbohydrates necessary for growth. The National Institute for Climatic Change Research's Midwestern Regional Center has performed studies concluding that acid rain can contribute to forest growth.

Effects of Acid Rain on the Environment

The effects of acid rain

Acid rain can be carried great distances in the atmosphere, not just between countries but also from continent to continent. The acid can also take the form of snow, mists and dry dusts. The dry dust can cause respiratory illnesses in animals and humans such as asthma.  The rain sometimes falls many miles from the source of pollution but wherever it falls it can have a serious effect on soil, trees, buildings and water. 

In the 1970s the effects of acid rain were at their worst.  Forests all over the world were dying and in Scandinavia the fish were dying; lakes looked crystal clear but contained no living creatures or plant life. Many of Britain's freshwater fish were threatened;  their eggs were damaged and deformed fish were hatched. This in turn affected fish-eating birds and animals.  Animals belong to a food chain and often if one link in a food chain is taken away it can have devastating effects.


It is thought that acid rain causes trees to grow slower or even to die but scientists have found that the same amount of acid rain seems to have more effect in some areas than it does in others.

As acid rain falls on a forest it trickles through the leaves of the trees and runs down into the soil below. Some of it finds its way into streams and then into rivers and lakes. Some types of soil can help to neutralise the acid - they have what is called a "buffering capacity". Other soils are already slightly acidic so these are particularly susceptible to the effects of acid rain.

Acid rain can effect trees in several different ways, it may:
dissolve and wash away the nutrients and minerals in the soilwhich help the trees to grow such as potassium, calcium and magnesium
cause the release of harmful substances such as aluminium into the soil and waterways which further affects wildlife.
wear away the waxy protective coating of leaves, damaging themand preventing them from being able to photosynthesise properly.
A combination of these effects weakens the trees which means that they can be easily attacked by diseases and insects or injured by bad weather. It is not just trees that are affected by acid rain, other plants may also suffer.

Lakes and rivers

It is in aquatic habitats that the effects of acid rain are most obvious. Acid rain runs off the land and ends up in streams, lakes and marshes - the rain also falls directly on these areas.
As the acidity of a lake increases, the water becomes clearer and the numbers of fish and other water animals decline. Some species of plant and animal are better able to survive in acidic water than others. Freshwater shrimps, snails, mussels are the most quickly affected by acidification followed by fish such as minnows, salmon and roach. The roe and fry (eggs and young) of the fish are the worst affected as the acidity of the water can prevent eggs from hatching properly, can cause deformity in young fish which also struggle to take in oxygen.

The acidity of the water does not just affect species directly, it also causes toxic substances such as aluminium to be released into the water from the soil, harming fish and other aquatic animals.

Lakes, rivers and marshes each have their own fragile ecosystem with many different species of plants and animals all depending on each other to survive. If a species of fish disappears, the animals which feed on it will gradually disappear too. If the extinct fish used to feed on a particular species of large insect, that insect population will start to grow, which in turn will affect the smaller insects or plankton on which the larger insect feeds.


Every type of material will become eroded sooner or later by the effects of the climate. Water, wind, ice and snow all help in the erosion process but unfortunately, acid rain can help to make this natural process even quicker. Statues, buildings, vehicles, pipes and cables can all suffer. The worst affected are things made from limestone or sandstone as these types of rock are particularly susceptible and can be affected by air pollution in gaseous form as well as by acid rain.

Reduce emissions:

Burning fossil fuels is still one of the cheapest ways to produce electricity so people are now researching new ways to burn fuel which don't produce so much pollution.
Governments need to spend more money on pollution control even if it does mean an increase in the price of electricity.
Sulphur can also be 'washed' out of smoke by spraying a mixture of water and powdered limestone into the smokestack.
Cars are now fitted with catalytic converters which remove three dangerous chemicals from exhaust gases.

Find alternative sources of energy:

Governments need to invest in researching different ways to produce energy.
Two other sources that are currently used are hydroelectric and nuclear power. These are 'clean' as far as acid rain goes but what other impact do they have on our environment?
Other sources could be solar energy or windmills but how reliable would these be in places where it is not very windy or sunny?
All energy sources have different benefits and costs and all theses have to be weighed up before any government decides which of them it is going to use.

Conserving resources:

Greater subsidies of public transport by the government to encourage people to use public transport rather than always travelling by car.
Every individual can make an effort to save energy by switching off lights when they are not being used and using energy-saving appliances - when less electricity is being used, pollution from power plants decreases.
Walking, cycling and sharing cars all reduce the pollution from vehicles.