Smog and Acid Rain

Particularly for large metropolitan cities, smog and poor air quality is a pressing environmental problem. Smog primarily consists of carbon monoxide, nitrogen oxides, volatile organic compounds chemically interacting with heat from sunlight forming ground level ozone. Smog is that familiar haze most commonly found surrounding large cities, particularly in the summer time. Smog and ground level ozone contribute to all kinds of respiratory problems ranging from temporary discomfort, asthma, to long-lasting, permanent lung damage. The pollutants in smog come from vehicle emissions, smokestack emissions, paints, and solvents - most of which started out as crude oil.

Much of the eastern United States is affected by another environmental problem known as acid rain. Acid rain can damage crops, forests, wildlife populations, and cause respiratory and other illnesses in humans. When sulfur dioxide and nitrogen oxides react with water vapor and other chemicals in the presence of sunlight, various acidic compounds form in the air and come to the earth as acid rain. The pollutants of acid rain are derived from coal fired power plants. Natural gas emits virtually no sulfur dioxide and up to 80 percent less nitrogen oxides than the combustion of coal. So the increased use of natural gas would provide for fewer acid rain causing emissions.

The source of energy to use for reducing pollution and maintaining a clean and healthy environment is natural gas. Natural gas is also domestically abundant making it a secure source of energy. The environmental benefits of using natural gas over other sources of energy, particularly other fossil fuels are numerous.

Since the use of natural gas emits only low levels of nitrogen oxides and virtually no particulate matter, it can be used to help combat smog formation in those areas where ground level air quality is poor. Electric utilities, motor vehicles, and industrial plants make up the main sources of nitrogen oxides. To combat smog production, especially in urban centers where it is needed the most, increased natural gas use in the electric generation sector, a shift to cleaner natural gas vehicles, and increased industrial natural gas use could all serve to improving the air quality. Summertime, when natural gas demand is at its lowest and smog problems are the greatest, would be a good time for industrial plants and electric generators to use natural gas to fuel their operations instead of using the more polluting fossil fuels. This would effectively reduce smog emissions resulting in clearer, healthier air around the urban centers.

A study conducted in 1995 by the Coalition for Gas-Based Environmental Solutions found that in the Northeast, smog and ozone-causing emissions could be reduced by 50 to 70 percent through the seasonal switching to natural gas.

Particulate emissions such as soot, ash, metals, and other airborne particles also cause the degradation of air quality in the United States. Natural gas emits virtually no particulates into the atmosphere. Emissions of particulates from natural gas combustion are 90 percent lower than from the combustion of oil, and 99 percent lower than burning coal. Increased natural gas use in place of other dirtier hydrocarbons can help to reduce particulate emissions in the United States.

Ocean acidification - Acid rains affecting oceans

Ocean acidification is decrease in the pH in our oceans caused when chemical substances like carbon dioxide (CO2), sulfur, or nitrogen mix with seawater. Ocean pH pH has dropped by slightly less than 0.1 units since industrial revolution and it is estimated that it will drop by a further 0.3 - 0.5 units by 2100, mainly because of carbon dioxide.

Ocean acidification has extremely negative results on some marine creatures like sea urchins, corals, and certain types of plankton as it decreases their ability to harness calcium carbonate which they need to harden their outer shells (exoskeletons). Importance of these creatures is highly important in marine food chain since they provide essential food and habitat to other species and they really represent the base of ocean ecosystems. Researcher Gretchen Hofmann recently said: "It's possible by 2050 they may not be able to make a shell anymore. If we lose these organisms, the impact on the food chain will be catastrophic.

Ocean acidification isn't making oceans significantly more acidic on global scale, but it significantly hurts coastal and shallow area and organisms that live in these areas. There are many factors contributing to acid rains such as farming, livestock husbandry and combustion of different fossil fuels. The most affected areas are usually downwind of coal power plants, on the eastern edges of North America, Europe, and south and east of Asia.

So not only our land hurts because of acid rains, but also our oceans and many marine organisms struggle to cope with increased acidity. And if current rates continue, by the end of this century acidity will be five times bigger than today, and this would really mean catastrophe.

Acid rain - Formation and impact

Acid rain is mostly caused by human emissions of different sulfur and nitrogen compounds which once in atmosphere produce acids. Main reason for acid rains is air pollution as a result of fossil fuels burning. Power plants (especially coal based), factories, cars, they all produce polluting gases and some of them when in atmosphere react with water in clouds to create sulphuric and nitric acids which are very harmful to our environment once they fall on Earth in the form of acid rain.

Acid rain can also take the form of snow, mists and dry dusts, although most common form is rain. The rain isn't always falling just on the polluted area as it can fall many miles away from the source of pollution. Wherever it falls, it has very harmful effect on soil, trees and water.

Acid rain impact can vary, from minimal to severe which depends on the region of the country and on the acidity of the rain as sometimes same amount of acid rains can have different effect in some areas than in others.

Forests exposed to acid rain lose valuable nutrients, trees grow more slowly and sometimes even stops to grow, leaves is damaged as their waxy protective coating wears away because of different acids. These harmful effects combined make trees more vulnerable to different diseases, weather and insects.

Acid rains are most obvious in waters, where they're increasing acidity of water which has tremendous negative impact on water ecosystems, often causing decline of fish and other water population and affecting variety of life in water ecosystems. Most visible effect in these water ecosystems is gradual disappearing of many fish species since their environment becomes intolerable and they're on the lookout for new habitats. Measure of the acidity in certain water ecosystem affected by acid rain is pH value. Here are the effects of an acidified ecosystem on certain pH value.

As water pH approaches	Effects
6.0	crustaceans, insects, and some plankton species begin to disappear.
5.0	major changes in the makeup of the plankton community occur. less desirable species of mosses and plankton may begin to invade. the progressive loss of some fish populations is likely, with the more highly valued species being generally the least tolerant of acidity.
Less than 5.0	the water is largely devoid of fish. the bottom is covered with undecayed material. the nearshore areas may be dominated by mosses. terrestrial animals, dependent on aquatic ecosystems, are affected. Waterfowl, for example, depend on aquatic organisms for nourishment and nutrients. As these food sources are reduced or eliminated, the quality of habitat declines and the reproductive success of birds is affected.

What can be done to stop acid rains? Probably the best answer lies in the alternative energy sources as to avoid harmful burning of fossil fuels but renewable energy sector is still negligible compared to dominant fossil fuels, not only at this moment, but also in years to come.

There's also important to mention that damage done by acid rains can be restored in lake and rivers which can have powdered limestone added to them to neutralize the water - this method is called "liming", but unfortunately isn't used very often because it's very expensive since it needs to be done continuously many times, until the acid rain stops, otherwise its affects are only temporary.

Rich countries Sweden and Norway successfully used this method to restore their lakes and streams. But this solution isn't really a possibility in countries with major acid rain problems (i.e. China) since they have no funds available for this expensive method causing many of their lakes and rivers to stay acidified for many more years and even growing in acidity levels since because of dominant fossil fuels use and its burning these rains continue to fall making this problem more severe with every new acid rain.

Acid Rain - Its Effects and What You Can Do to Help:

Acid rain is relatively unseen and hard to detect, but it is a widespread serious problem that probably affects the area where you live today. Acid rain is defined as rain that has a higher acidic content than normal due to unnatural (human produced) processes. The severity of the problem in your area depends on factors ranging from how close you are to conventional coal-fired power plants, how much rainfall there is total, and upper and lower atmosphere wind currents.

If only the effects of acid rain were as innocuous as the definition! In North America, for example, the problem has progressed so that rainwater can have anywhere from 1000% to 7000% too much acid content. Standing water, where some evaporation has occured, or water that has been absorbed and filtered by the soil can have an even larger acid content. Rainwater that is too acidic can cause many types of problem, such as:

- Acid rain can defoliate trees (making them lose their leaves or needles). This can eventually lead to the tree dying if there is no intervention. Trees can also suffer from stunted growth, and become weakened so that they are vulnerable to weather, disease, and insects.

- When lakes are seriously damaged by acid rain fish die off, birds die from eating "toxic" fish, and humans cannot swim in them

- Buildings and other structures can be corroded by acid rain. In addition, other objects can be affected such as bridges, underground pipes, and artwork on historical buildings.

- Currently, both the railway and airline industries have to be diligent to repair the corrosive damage done by acid rain.

- Humans can become seriously ill and can even die from the effects of acid rain because it can cause respiratory problems, particularly in those who are already vulnerable such as people with asthma.

Acid rain is caused by smoke and gases that are given off by factories and cars. Simply put, the pollutants in the exhaust go into the atmosphere, and become acid that comes back down mixed with rain. A great deal of acid rain is produced when coal is burned to produce electricity. There are ways to clean the coal, called clean coal technology, but these methods are expensive and would probably require government subsidies or new technological breakthroughs to be viable.

Anyone can help reduce the problem of acid rain. You can write to your government official to promote clean coal technology, you can invest in companies that are developing new fossil fuel-free cars, such as fuel cell and electric cars. But most importantly, you can reduce your own consumption of electricity that is produced from coal, drive your gas-fueled car less often, and reduce your own acid rain footprint to make a real difference.

The Devastating Effects Of Acid Rain

Acid rain is an environmental problem that affects areas all around the world. It is the result of sulfur and oxide mixing with moisture for the sky. The pollutants get into the air by fossil fuels, vehicle emissions, and factory exhaust. Acid rain is considered to be one of the largest environmental problems facing the world today.

Acid rain the areas of Europe and North America have seen a dramatic increase in the past decade. Some areas contain anywhere from 10 to 70% more acid than normal. The higher the acid level, the more damage is done to living and non living objects. The environment as a whole suffers. Humans, forests, trees, lakes, animals, and plants all suffer from the effects of acid rain.

Trees are a natural resource. They provide wood, protect against the elements, and provide shelter to wildlife. As trees are destroyed by acid rain, the things that depend on the trees for survival are also affected. It is a downward spiral that continues out of control. Lakes that are damaged by acid rain cause the water and fish to become contaminated. When the fish die, the main source of food for the birds is destroyed. If the area is extremely full of acid rain, the fish eggs may die before even hatching, reducing the amount of food available as well.

Studies are continually being conducted on the effects of acid rain on humans. It can destroy our land and contaminate our food. The main concern is toxic metals. These metals can find their way into drinking water, crops, or animals that we eat. Consuming these items can lead to nerve damage and brain damage. Some researchers think that acid rain can be linked to Alzheimer’s as well.

Respiratory problems in humans resulting from acid rain are common in many areas of the world with high levels of acid. The symptoms include a dry cough, asthma, headaches, and irritations in the eyes, nose, and throat. Taking all this into consideration, the United States and Canada signed the Air Quality Agreement in 1991. The purpose of the agreement is to reduce the effects of acid rain.

Acid Rain & Caustic Residues

When pollutants and emissions drift into the atmosphere and combine with rain or snow they form acids. These diluted acids settle on a vehicle’s surface and when the water evaporates and dries on the surface the remaining mineral-laden polluted rain becomes more concentrated and causes damage to the surface creating slight depressions or craters on the clear coat and sometimes into the color coat. When you have water spots that just won't come off, these imperfections are commonly referred to as acid rain etching.



This category also includes mineral deposits, cement, salt, calcium, and lime deposits. We recommend immediate removal to increase the probability of a full surface restoration. If left untreated, acid rain will cause permanent surface damage.

Similar damage can also be caused by bird droppings and insect residue. If the residue is extremely acidic in composition, it will etch a crater into paint and plastic.

Why is Acid Rain Harmful?

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 Streams

Without 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 , 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.

What is acid rain?

Acid rain is rain that is polluted by acid in the atmosphere. It damages the environment. The acid can also be found in snow and fog. There are 2 main air pollutants that change into acid, sulphur dioxide (SO2) and nitrogen oxide (NOX). When they react with moisture in the atmosphere they become acids.

Where do the pollutants come from?

The sulphur and nitrogen pollutants come from burning fossil fuels, from coal-fired generators making electricity, from smelting furnaces in steel works, and from petrol driven motor vehicles.

What are the effects of acid rain?
Acid rain can harm forests and crops.It pollutes rivers, lakes and streams and damages the animals that live in them. Acid rain also damage to statues and buildings.

Acidic dust!
Acid in the atmosphere also falls to the earth as dust. Some scientific studies have found that acidic dust particles can cause an increase in attacks of asthma and bronchitis in humans

When the dust is washed away by rain the acid is added to the rain water which pours into streams and river and the oceans, polluting them and harming plants and animals that live there.

Acid rain can also ruin buildings and public statues and monuments. The acid eats into metal and stone.

What can be done?
People can help by turning off lights, computers and other appliances when they're not being used.

Buy energy efficient appliances which use less electricity.

Using alternative energy sources such as wind energy, geothermal energy, and solar energy will reduce the pollutants caused by electricity generation.

Cars powered with natural gas and battery-powered cars will produce less pollution.

What is raildust?

Raildust is the common name given to ferrous metal fallout contamination. Often raildust comes from trains and is caused by the train’s wheels on the rails, the electrical pick-up rubbing overhead cables and the effect of the braking mechanism causing tiny particles of metal to fly off into the air. However, this kind of fallout can be caused by any mechanical device that involves metal on metal, including your own car’s brakes. Exhaust fumes will contain some amount of metal, especially from ships and aircraft, foundries and factories.



So already, by pointing out where it comes from, we can see how to avoid it - if you park your car at the railway station, park as far away from the tracks as you can. Metal dust is heavy so it doesn’t float about and travel very far. Just 50 yrds can make a huge difference to the amount of fallout your car will collect in the station car park. Also beware of car parks in ports, airports and next to busy motorways.And of course, if you must use a grinder to sharpen the lawnmower blades, park your car down the street!

No matter what you do, you will get some level of ferrous metal contamination on your car, but why is this a problem? Ferrous metal will rust when it comes into contact with water and the oxidization process causes acids which destroy the binders in your paint. So as the particle rusts, it dissolves the paint underneath it and it then burys it’s self deeper into the paint until it has eaten all the way through to the bodywork, and once that happens, your bodywork begins to rust. It’s important to know how to spot fallout, if you have a light coloured car you will be able to see it as little brown specs, often you can see these against a black coloured car too. A better way to find fallout is to feel for it.if your car is clean, wet an area with clean water and run your fingers over it, if you can feel hard gritty lumps, chances are that that is raildust. (some people do this while having their hand inside a sandwich bag, the fallout will snag on the bad revealing the fallout - this is a good method if you haven’t very sensitive fingertips).

There are two methods of removal. The first is an acid bath… this sounds scary but really isn’t a problem if you are a professional valeter. You wash the car down in an acidic solution, much like a wheel cleaner, this will dissolve the metal particles, and then before the acid can damage the paintwork you wash it off with a soapy solution which will neutralize the acid.

The second method is to use aclay bar (a.k.a. detailing clay) to remove the raildust. Usually a claybar is a synthetic putty which is very sticky and will suck the particles out of the paintwork. A claybar deserves a full entry which can be found here, worth reading folks, because this is a method that you can do yourself!

What is fallout? Acid Rain affect the cars

Fallout is anything that falls on your car, contaminates it and can damage the paint or otherwise ruin the appearance.Usually when people talk about fallout, they mean industrial fallout, specifically rail dust. Rail dust is particles of metal, most commonly from railway lines (hense the name) but it can come from any industrial process. Contamination with metal particals is a subject which deserves it’s own entry which can be found here.



Other forms of industrial fallout can include just about anything that industry pumps out into the air including pollution and acid rain. Over the years I have seen lime scale contaminated water splashed on cars, cement dust, red oxide paint, Hammerite, creosote, ash, soot, etc, etc.



Fallout really could include just about anything. Several of the cars we have treated for fallout managed to get it by driving down the motorway where earlier a lorry had spilt it’s load… so when you think of all the different liquids and powders transported on British roads, the possibilities are endless.There are also natural forms of fallout such as tree sap, berries and buds, or even bird/bat/insect droppings.

Apart from raildust, the two most common forms of fallout are paint overspray, concrete splatter and tree sap.



Paint overspray is very common, if your car goes into a bodyshop for crash repair it is likely to pick up some overspray. The body shop will mask out the immediate area of the repair, but the air becomes thick with paint particles which are semi-dry. These will land on the upper surfaces of your car and stick. If you car has had a fairly serious repair and been in the bodyshop for several days, you can get overspray from every car they have painted during that time and sometimes its quite visible and looks like a layer of dust. Unlike dust it won’t just wash off but there are several methods of removal. The first of these is to polish the car’s paintwork and windows, this is okay if the fallout isn’t too severe but might be very hard work on heavy fallout. The next method is to use a clay bar which is a sticky bar of riverbed clay, or more usually a synthetic clay very similar to Blu-tac, only a lot more sticky. Clay bar, otherwise know as detailing clay, will help you to rub away the fallout which will stick to the bar. The third method is machine polishing or buffing… if the overspray has gone on very wet this is the only way to remove it.

Unlike paint overspray which just makes your car look slightly matt and dull, fallout from trees can be harmful to your paintwork and cause etching or staining. Usually this organic fallout is tree sap, which isn’t too harmful if you get it off fairly quickly but it can be a real problem to remove. Usually we use a TFR which stands for Traffic Film Remover - this is just a soap but it is strong enough to strip traffic film, grease, and even the wax from your car. This usually works really well, especially when you are running the TFR through a hot pressure washer, but there are times where we have needed to use Tar and Glue remover or other solvent based cleaner.

Certain trees will drop berries onto your car which can cause stains, it’s important to wash these off as soon as possible, never more so than if they land on your car having passed through a dicky-bird! In fact bird droppings are one of the most corrosive things to land on your car. Many car enthusiasts cary a packet of baby wipes or a bottle of quick detailer wax and a microfibre cloth in the car to be able to deal with the problem in short order. Some manufacturers are now producing bird lime neutralizers to deal with the problem.

How Does Acid Rain Affect The Environment ?

It is important for us to understand what exactly Acid rain is to understand the harmful damages it can because Acid rain is mainly caused due to pollution. Air pollution is caused when every type of fuel is burnt or used by various industries and vehicles. Fuel contains several chemicals which do not dissolve, but instead become a residual gas in the environment. The smoke that comes out when fuel is burnt contains these residues.

The air in the atmosphere cannot absorb this smoke. So, it remains suspended there.However, rainfall absorbs all the impurities from the air, and that is how it absorbs these chemicals that come out of air pollution also. The raindrops turn acidic due to it. These raindrops contain harmful and invisible gases.

Power stations, factories, industries, cars, vehicles, airplanes and ships are all responsible for causing air pollution. The acidity of acid rain can only be measured using the pH scale. The lower the pH balance is, the more acidic the rain is. Acid rain upsets the pH balance of the atmosphere. To live healthily, we need to breathe in air with a normal pH balance. A normal pH balance indicates that the air is fresh and also is pure. Something like 7 is ideal.

However, in today’s circumstances in a city it is difficult to find a normal pH balance between 5 and 6. In some cities the pollution is so severe that the pH balance of the air falls below 3 sometimes. The environment which is not pure and pristine cannot hold life.

Where Does Acid Rain Come From ?

Acid rain is nothing but the regular rain that has turned acidic. There are several causes for acid rain, and one of the main reasons among them is high levels of pollution. Several industries, vehicles and power generating plants are dependant on fossil fuels like coal and oil for their operations.Almost everyone depends on power, and vehicles to run people's everyday lives.

However, these things would require coal or oil to be burnt to function. When these fossil fuels are burnt, they emit sulfur dioxide and nitrous oxide into the air. These gases are hot in temperature, and they rise high. Raindrops absorb these chemicals when they condense and fall. When these gases that are absorbed by the raindrops react with carbon and sunlight, they turn into acids and the raindrop also turns acidic as a result. Acid rain is nothing but a simple chemical reaction that converts water into acid.

However, when the pollution is high and when it rains, this chemical reaction takes place in large scale. This leads to massive acid rain scenario. When acid rain falls at large, it can cause severe damage to plants, humans and also sea life. There are several forms of acid rain like acid fog, acid mist, and acid snow. All these can prove to be very dangerous for humans, plants and animals. The acidic gases and particles present in the atmosphere are called dry depositions. These can be present even on top of leaves and plants and when they get washed by rain, the rain can become acidic.

How Does Acid Rain Affect Humans ?

Acid rain has different effects on human beings, and also there are several kinds of it. In some parts of the world, where people have colder climates, they have to deal with acid rain, acid snow and even acid fog. It is a lot more miserable than acid rain. There are other kinds like acid gas and acid dust. So whichever particle found in the atmosphere when exposed to the polluted environment, it becomes acidic in nature.In today’s world most of the streams and lakes are acidic to a certain extent.

Acid rain affects human beings, plants and animals with the same magnitude. It causes damage to the environment and health in multiple levels. When human skin comes in contact with this type of rain, it may develop infections or get other skin diseases due to unwanted chemical reactions. Also, when people breathe in the air after an acid rain, they may develop lungs related problems and also breathing difficulty.

Children are the most vulnerable to acid rain. They develop lung and breathing related problems more easily than adults. Also, children who have conditions like asthma or bronchitis are more susceptible to the harmful effects of acid rain. The harmful side effects of acid rain is not only seen when we are in direct contact with it, but also in indirect contact. For example, fruits and vegetables that come in contact with this type of rain can also harm our body in the same way as being directly exposed to acid rain.

Pollutants

Pollutants are ingredients causing pollution. They may be gases, liquids, solids of different chemical composition or may be high pitched sounds. The pollutants are not deliberately manufactured. But they are the by products of manufacturing processes. At different stage of manufacturing, these pollutants may be generated. As they are not useful to manufacture any useful product of commercial value, they are sent out of the industries.

The pollutants from industries are of different types and carry varying importance. The type of pollutant generated out of manufacturing process depends upon the nature of materials used during manufacturing process as wall as technology adopted to process them.

Gaseous Pollutants

During the process of manufacture, most industries produce pollutants. Most common gaseous pollutants released by industries are:

Carbon monoxide

Highly dangerous gas with a high potentiality of causing cancer and respiratory ailments. Generally, it is evolved, when a fuel is burnt under limited supply of oxygen.

Carbon dioxide

It is also a pollutant, when generated in large quantity - because it can reduce the oxygen concentration in the air. It is a gas produced when fuel is burnt in adequate oxygen.

Normally, the atmospheric air will have 0.03% CO₂. When its concentration increases due to pollution, it reduces the percentage of oxygen in atmosphere.

Sulphur dioxide

Sulphur dioxide(SO₂) is one of the dangerous pollutant with a potentiality to form sulphuric acid, when mixed with water vapour. Water vapour commonly available in air can mix with SO₂ gas and produce sulphuric acid.

Such sulphuric acid is the cause of acid rain.

Dry and Wet Acid Deposition or Acid Rain

Hydrogen sulphide

Hydrogen Sulphide(H₂S) is one of the dangerous, pungent pollutant gas with many deleterious effects respiratory tract. It is released from many industries as a part of sulphonation process.

Hydrogen Cyanide (HCN)

When cyanide chemicals are used in manufacturing process, hydrogen cyanide is formed as a by product. It is a highly corrosive and poisonous gas leading to eye irritations, respiratory problems as well as other complications. In high doses, it can cause death.

Ammonia Gas

In many industries, ammonia gas (NH₃) is used as reducing agent. It is a corrosive gas with a high potentiality of causing throat irritations, burning of pharynx, oesophagus, etc. It can also cause digestive problems - when excess gas is inhaled.

Liquid Pollutants

Many liquid pollutants are evolved during the process of manufacturing pesticides, medicines and other chemicals. Liquid pollutants are also released during the process of refinement and processing. Some of them are dangerous and cause serious implications on drinking water quality.

The types of liquid pollutants can be

• acids - hydrochloric, acetic, fumaric, sulphuric, nitric, benzoic

• bases - hydroxides of sodium, calcium, magnesium

• carboxylic compounds

• nitrogenous wastes

Oil refineries

Crude oil contains sulphur. When sulphur is burned, it produces sulphur dioxide. If this gets into the atmosphere, it can cause what is called 'acid rain'.

Acid rain is a broad term to describe the effects of acidic compounds in the atmosphere - even though they don't necessarily fall as rain. Sulphur dioxide (SO^₂) and nitrogen oxides (NO_x - sometimes called 'nox') are released into the atmosphere when we burn fossil fuels (particularly coal). They return to earth on dry dust particles or dissolved in rain drops.

Acid rain is thought to be responsible for damaging large areas of forests and degrading the soil. It also damages materials including limestone and exposed metals.

Therefore, wherever possible, we want to remo

ve sulphur from fuels before we burn them. There are now strict controls in the UK on sulphur and 'nox' emissions from cars. These can be met, in part, thanks to the removal of sulphur from naphtha in the refinery.

Treat gas is used to remove the sulphur from fuel fractio ns (naphtha, light gas oil and kerosine). The treat gas is mainly hydrogen and is a by-product of other processes.
	The hydrogen reacts with the sulphur compounds in the hot hydrocarbons. The reaction produces hydrogen sulphide (which may be familiar to you because of its 'rotten eggs' smell). The hydrogen sulphide is removed and taken to the sulphur processing plant. Here, it is oxidised to make liquid sulphur. this is solidified and sold to the chemical industry.

Effects of Acid Rain

We generally consider acid rain to affect areas which are downwind of pollution generating sites. The northeastern United States, for instance, suffers from acid precipitation generated both locally and by coal fired plants in the mid-western states. As a result, ecosystem damage is localized. However, acid precipitation can be caused by some natural events (volcanic eruptions, erosion and oxidation of organic-rich sedimentary rocks) and some catastrophic events (bolide impact) which increase the amounts of CO₂, NO_x and SO₂ in the atmosphere. As a result, it is important to understand the effects of acid rain on animals inorder to evaluate both possible causes for past extinction events, as well as the potential for modern ecosystem damage.

Acid Formation in the Atmosphere

First, let us review some basic chemistry as it applies to acid precipitation.

Carbonic acid forms naturally in the atmosphere due to the reaction of water (H2O) and carbon dioxide (CO2),

H₂O + CO₂ -> H₂CO₃

_{while the burning of coal and other organics adds sulfur dioxide (SO2) and Nitrous oxides (NOx) to the atmosphere where they react to form sulfuric acid and nitric acid,}

2SO₂ + H₂O + O₂ -> 2H₂SO₄

4NO₂ + 2H₂O + O₂ -> 4HNO₃

_{All of these acids will be buffered by reacting with rocks, minerals, etc. on the earth's surface. The most important (and fastest) buffering comes from the reaction with (weathering of) calcite in the form of limestone, dolomite or marble.}

H₂CO₃ + CaCO₃ -> 2HCO₃^- + Ca⁺²

When this reaction occurs, the acid is neutralized and the calcite dissolved. While the reaction with calcite is very fast (the standard test for calcite in introductory geology labs is to put very dilute acid on a sample to see if it bubbles (reacts)), the reaction with other rocks is very slow, so most of the acid is not affected. This is why ponds in the Adirondacks became acidified (non-calcite rock in those areas), while Lake Champlain (abundant calcitic bedrock) did not.

The degree of acidification is the pH of the water, which is defined as the negative logarithm of the concentration of hydrogen ion (H⁺), or

pH = -log [H⁺].

(This to a certain degree comes from the old definition of an acid as a proton donor. A hydrogen ion is little more than a proton, so think of it as the amount of free protons floating around).

A pH of 7 is considered neutral, while a pH less than 7 is considered acidic. For example, wine has a pH of about 3.5 and your stomach digestive fluids have a pH of about 1.9.

We should also be aware that increased acidity does not have to be constant, but instead can be episodic. High surface water discharge events (storms, snowmelts) can increase the pH of streams and ponds to dangerous levels for short times.

Effects of Acidity on Plants and Animals

As a first example of the effects of acid rain, we can examine a case which is not obvious - effects on non-aquatic, tree nesting birds. This study was carried out in the Netherlands. It was observed that the proportion of birds laying defective eggs rose from roughly 10% in 1983-84 to 40% by 1987-88. The defective eggs had thin and highly porous egg shells, which resulted in eggs failing to hatch because of shell breakage and desiccation. As a result, there was also a high proportion of empty nests and clutch desertion. It was also observed that these effects were limited to areas of acid rain.

Since the birds did not appear to be directly affected by the acidity, the food chain was examined (these birds are positioned at the upper part of the local food chain). The difference between areas of normal soil pH (buffered by high calcium content due to limestone and marble outcrops and bedrock) and those with acidic soil appeared to be the presence of snails. The snails depend on the soil as their calcium source as they secrete their shells. With much of the CaCO₃ leached out of the soil by the acid precipitation, the snails could not survive in the area. The birds did not, at first, appear to be affected, because they continued to eat spiders and insects which, while supplying a sufficiently nutritious diet for the birds, where a poor source of calcium.

To test the hypothesis that the lack of calcium was the cause of the bird's laying defective eggs, ecologists "salted" the area with chicken egg shell fragments. The birds began to eat the chicken egg shells, and those that did laid normal eggs.

In this case, acid precipitation had affects that passed on up the food chain.

AFFECTS ON AQUATIC SYSTEMS

Mollusks - snails and clams.

- these invertebrates are highly sensitive to acidification because of their shells which are either calcite or aragonite (both forms a CaCO₃) which they must take from the water.

- in Norway, no snails are found in lakes with a pH of less than 5.

- of 20 species of fingernail clams, only 6 were found in lakes with pH of less than 5.

Arthropods

- crustaceans are not found in water with a pH less than 5.

- crayfish are also uncommon in water where the pH is less than 5. This is an important consideration because crayfish are an important food source for many species of fish.

- many insects also become rare in waters with a pH less than 5.

Amphibians

- as you may know, many species of amphibians are declining. To what extent acid rain is contributing to this decline is not exactly known. However, one problem is that in places like northeastern North America amphibians breed in temporary pools which are fed by acidified spring meltwater. In general, eggs and juveniles are more sensitive to the affects of acidity.

Zooplankton in lakes

- changes in diversity among zooplankton have been noted in studies carried out in lakes in Ontario, Canada. These studies found that in lakes where the pH was greater than 5 the zooplankton communities exhibited diversities of 9 - 16 species with 3 - 4 being dominant. In lakes where the pH was less than 5, diversity had dropped to 1 - 7 species, with only 1 or 2 dominants.

Periphytic algae

- many acidified lakes exhibit a large increase in the abundance of periphytic algae (those that coat rocks, plants and other submerged objects). This increase has been attributed to the loss of heterotrophic activity in the lake (i.e., the loss of both microbial and invertebrate herbivores in the lake).

Fish

- as a result of acidification, fish communities have suffered significant changes in community composition attributed to high mortality, reproductive failure, reduced growth rate, skeletal deformities, and increased uptake of heavy metals.

Mortality

- effects on embryos and juveniles:

- Atlantic salmon fry have been observed to die when water with pH <>

- in fish embryos, death appears to be due to corrosion of epidermal cells by the acid. Acidity also interferes with respiration and osmoregulation. In all fish at a pH of 4 to 5 the normal ion and acid/base balance is disturbed. Na+ uptake is inhibited in low pH waters with low salinity. Small fish are especially affected in this way because due to their greater ratio of body and gill surface area to overall body weight, the detrimental ion flux proceeds faster.

- in all fish low pH water causes extensive gill damage. Gill laminae erode, gill filaments swell, and edemas develop between the outer gill lamellar cells and the remaining tissue.

- at pH <3>

Reproductive Failure

Reproductive failure has been suggested as the main reason for fish extinction due to acidity. In Ontario, Canada it was observed that in acidified lakes female fish did not release ova during mating season. When examined, the fish were found to have abnormally low serum calcium levels which appears to have disrupted their normal reproductive physiology.

Growth

Growth may increase or decrease depending on resistance of a species to acidity. For resistant species, growth can increase due to the loss of competing non-resistant species. On the other hand, growth can decrease due to increase in metabolic rate caused by sublethal acid stress. In this case the organism's rate of oxygen consumption goes up because the excess CO₂ in the water increases the blood CO₂ level which decreases the oxygen carrying capacity of the hemoglobin.

Skeletal Deformity

This occurs in some fish as a response to the lowered blood pH caused by increase in CO₂ described above. Bones decalcify in response to a buildup of H₂CO₃ in the blood as the body attempts to maintain its normal serum osmotic concentration (i.e., the body attempts to return to a normal blood pH level).

How is acid rain measured?

Acid rain is measured through pH tests that determine the concentration of hydrogen ions in a liter of fluid. The pH (potential for hydrogen) scale is used to measure acidity or alkalinity. It runs from 0 to 14. Water has a neutral pH of 7. (The greater the concentration of hydrogen ions and the lower the pH number, the more acidic a substance is; the lower the concentration of hydrogen ions and the higher the pH number, the more alkaline—or basic—a substance is.) So a pH greater than 7 indicates an alkaline substance while a pH less than 7 indicates an acidic substance.

It is important to note that a change of only one unit in pH equals a tenfold change in the concentration of hydrogen ions. For example, a solution of pH 3 is 10 times more acidic than a solution of pH 4.

Normal rain and snow measure about pH 5.60. In environmental science, the definition of acid precipitation refers to a pH less than 5.65.

Acid rain can erode structures such as buildings, even if they are made out of stone. (Reproduced by permission of JLM Visuals.)

Measured values of acid rain vary according to geographical area. Eastern Europe and parts of Scandinavia have rain with pH 4.3 to 4.5; rain in the rest of Europe ranges from pH 4.5 to 5.1; rain in the eastern United States and Canada ranges from pH 4.2 to 4.6, and the Mississippi Valley has a range of pH 4.6 to 4.8. The worst North American area, analyzed at pH 4.2, is centered around Lake Erie and Lake Ontario.

When pH levels are drastically upset in soil and water, entire lakes and forests are endangered. Evergreen trees in high elevations are especially vulnerable. Although the acid rain itself does not kill the trees, it makes them more susceptible to disease. Also, high acid levels in soil causes leaching (loss) of other valuable minerals such as calcium, magnesium, and potassium.

Small marine organisms cannot survive in acidic lakes and rivers, and their depletion (reduced numbers) affects the larger fish who usually feed on them, and, ultimately, the entire marine-life food chain. Snow from acid rain is also damaging; snowmelt has been known to cause massive, instant death for many kinds of fish. Some lakes in Scandinavia and New York's Adirondack Mountains are completely devoid of fish life. Acid rain also eats away at buildings and metal structures. From the Acropolis in Greece to Renaissance buildings in Italy, ancient structures are showing signs of corrosion from acid rain. In some industrialized parts of Poland, trains cannot exceed 40 miles (65 kilometers) per hour because the iron railway tracks have been weakened from acidic air pollution.

Impacts of Acid Rain on Soils

Soil is the basis of wealth upon which all land-based life depends.
The damage that occurs to ecosystems from acidic deposition is dependent on the buffering ability of that ecosystem. This buffering ability is dependent on a number of factors, the two major ones being soil chemistry and the inherent ecosystem sensitivity to acidification. Indirect damage to ecosystems is largely caused by changes in the soil chemistry. Increasing soil acidity can affect micro-organisms which break down organic matter into nutrient form for plants to take up. Increasing soil acidity also allows aluminium (a common constituent of soil minerals) to come into solution. In its free organic form, aluminium is toxic to plant roots and can lock up phosphate, thereby reducing the concentrations of this important plant nutrient.

What Effect Does the Soil and Underlying Bedrock Have on Acid Rain?
Soils containing calcium and limestone are more able to neutralise sulphuric and nitric acid depositions than a thin layer of sand or gravel with a granite base.
If the soil is rich in limestone or if the underlying bedrock is either composed of limestone or marble, then the acid rain may be neutralised. This is because limestone and marble are more alkaline (basic) and produce a higher pH when dissolved in water. The higher pH of these materials dissolved in water offsets or buffers the acidity of the rainwater producing a more neutral pH.

Acid Sensitive Areas
In regions where the soil is not rich in limestone or if the bedrock is not composed of limestone or marble, then no neutralising effect takes place, and the acid rainwater accumulates in the bodies of water in the area. This applies to much of the north-eastern United States where the bedrock is typically composed of granite. Granite has no neutralising effect on acid rainwater. Therefore over time more and more acid precipitation accumulates in lakes and ponds.

The water bodies most susceptible to change due to acid precipitation are those whose catchments have shallow soil cover and poorly weathering bedrock, for example granite and quartzite. These soil types are characterised by the absence of carbonates that could neutralise acidity. The run-off water from such areas is less buffered than from areas such as limestone catchments, with an adequate level of carbonate. Such catchments and waters are termed acid-sensitive (poorly buffered), and can suffer serious ecological damage due to artificially acidified precipitation from air masses downwind of major emissions.

Notable high-risk areas in Canada and the United States are the Canadian Shield, the Adirondack Mountains, the Laurentians, the Appalachians, and the Green Mountains of Vermont. These areas are vulnerable because of their high elevations, small watersheds, and naturally acidic soils. Different types of bedrock contain variable amounts of alkaline chemicals. Regions with bedrock containing less alkali have a lower capacity for reducing acidity, and thus are more sensitive to acid deposition.

Effects of soil on vegetation
When acid rain falls, it can affect forests as well as lakes and rivers. To grow, trees need healthy soil to develop in. Acid rain is absorbed into the soil making it virtually impossible for these trees to survive. As a result of this, trees are more susceptible to viruses, fungi and insect pests.
Long-term changes in the chemistry of some sensitive soils may have already occurred as a result of acid rain. As acid rain moves through the soils, it can strip away vital plant nutrients through chemical reactions, thus posing a potential threat to future forest productivity.

Poisonous metals such as aluminium, cadmium and mercury, are leached from soils through reacting with acids. This happens because these metals are bound to the soil under normal conditions, but the added dissolving action of hydrogen ions causes rocks and small-bound soil particles to break down.
Plant life in areas where acid rain is common may grow more slowly or die as a result of soil acidification. In the Green Mountains of Vermont and the White Mountains of New Hampshire in the United States 50% of the red spruce have died in the past 25 years. There has also been noted a reduced amount of growth in existing trees as measured by the size of growth rings of the trees in these areas.

These effects occur because acid rain leaches many of the existing soil nutrients from the soil. The number of micro-organisms present in the soil also decreases as the soil becomes more acidic. This further depletes the amount of nutrients available to plant life because the micro-organisms play an important role in releasing nutrients from decaying organic material. In addition, the roots of plants trying to survive in acidic soil may be damaged directly by the acids present. Finally, if the plant life does not die from these effects, then it may be weakened enough so that it will be more susceptible to disease or other harsh environmental influences like cold winters or high winds.

Critical Loads
Environmental response to pollutants depends on many factors. Some regions cope with acidification better than others, having larger 'critical loads'. Critical load refers to the greatest assault that an ecological system can withstand before showing measurable degradation.

Scientists determine critical load by examining rock and soil type, land use and rainfall. If soil is fertile with a pH greater than 4.5, and rainfall is relatively low, the critical load will be high. The terrain can withstand moderately large additions of acidity without undue suffering. Conversely, in low pH soils, acidification mobilises toxic aluminium ions. If coniferous forests predominate, or if land is devoted to rough grazing, the result is a low critical load. Even minor acid deposition is undesirable.

There are very few long-term UK monitoring studies of soil acidification and none of soil biota. Chemical data are available from a few specific sites, from a small number of regional studies and from three national studies. From the limited information available, the National Expert Group on Transboundary Pollution has concluded that there is evidence that acid deposition has resulted in widespread acidification of acid sensitive soils in the UK. Further critical loads modelling research suggests that soil recovery from acidification may take many years or even decades.

Acid Rain – Is It A By-Product of Global Warming?

Acid rain: two words that are not very pretty. Instead of the romantic rain that most of us would like to imagine, acid rain brings to mind frightening images of a future wrought with pollution and other problems. But what is acid rain and what is it caused by? And is acid rain really a by-product of global warming? The short answer is both yes and no. Acid rain has causes that are rooted both in nature and in the human activity that is causing the effects of global warming to become more pronounced.

In scientific terms, acid rain refers to any kind of precipitation, including mist, snow, fog, and of course, rain, that is more acidic than normal. Most rain is naturally a bit acidic, but acid rain contains an above average level of acid in it. Generally speaking, acid rain is caused by emissions of sulfur dioxide and nitrogen oxides that react with hydroxyl radicals and water vapor that exist in many industrial environments. When this combination exists, the acid rain may come down as either dry acid deposition or, when it is mixed with water, it is known as acid rain.

What is most acid rain composed of? Acid rain as it falls in the eastern part of North America and parts of Europe is composed mostly of sulfuric acid and nitric acid. How do these things make up acid rain? Acid rain generally occurs when the burning of fuels produces sulfur dioxide and nitrogen oxides. These different oxides get into our atmosphere because of both natural environmental activity as well as human activity. When these oxides reach the troposphere, they become oxidized by the hydroxyl radicals in the atmosphere that then break down the oxides into sulfuric and nitric acids. These acids will usually break down readily into water that is then brought down in the form of precipitation, or acid rain.

So is acid rain a by-product of global warming? It is not so simple. Many natural sources are also a part of acid rain. Many tons of sulfur is released into the earth's atmosphere each year from natural sources, including volcano eruptions, microbial processes, and sea sprays. Nitrogen oxides are also released into the earth's atmosphere in a natural manner, including from burning, lightning, the burning of biomass, and many microbial processes.

However, in a sense, acid rain is indeed a type of by-product of global warming because human activity often is responsible for some kinds of acid rain. It is estimated that human beings release up to 100 to 130 million tons of sulfur dioxide into the atmosphere. Human beings are also estimated to be responsible for roughly 60 to 70 million tons of the nitrogen oxides that are released into the earth's atmosphere each year. Most acid rain occurs in highly industrialized areas where these oxides are released into the earth's atmosphere on a regular basis. However, human activity has caused more oxides to be released into the earth's atmosphere in certain concentrated areas. Thus, human activity is definitely a strong factor in the occurrence of acid rain, especially in highly concentrated areas.

The effects of acid rain are becoming recognized as a growing problem, especially around highly industrial areas. Areas that have been highly industrialized for more than 100 years are considerably more susceptible to experiencing acid rain. However, all parts of the world are susceptible to some kind of acid rain. Acid rain is especially having an effect on many fragile ecosystems, including many of the earth's aquatic ecosystems. Acid rain can also have a devastating effect on forests.

Normally while rain travels through the air, it dissolves floating chemicals and washes down particles that are suspended in air. At the start of its journey raindrops are neutral (pH = 7). In clean air, rain picks up materials that occur naturally such as dust, pollen, some CO₂ and other chemicals produced by lightening or volcanic activities. These substances make rain slightly acidic (pH = 6), which is not dangerous. However, when rain falls through polluted air, it comes across chemicals such as gaseous oxides of sulphur (SO_x), oxides of nitrogen (NO_x), mists of acids such as hydrochloric and phosphoric acid, released from automobile exhausts industrial plants, electric power plants etc.

These substances dissolve in falling rain making it more acidic than normal with pH range between 5.6 -3.5. In some case, it's pH gets lowered to the extent of 2. This leads to acid rain. The term acid rain is used here to describe all types of precipitation, namely, rain, snow, fog and dew more acidic than normal.

Chemistry of acid rain

In the natural processes of volcanic eruptions, forest fires and bacterial decomposition of organic oxides of sulphur and nitrogen, production and reductions of gases naturally tend to an equilibrium. Power plants, smelting plants, industrial plants, burning of coal and automobile exhausts, release additional sulphur dioxide, nitrogen oxides and acidic soot, causing pollution. Sulphur dioxide and nitrogen dioxide interact with water vapours in presence of sunlight to form sulphuric acid and nitric acid mist.

The formed sulphuric acid and nitric acid remain as vapour at high temperatures. These begin to condense as the temperature falls and mix with rain or snow, on the way down to the Earth and make rain sufficiently acidic.

Harmful effects of acid rain

SO_x, NO_x mixed with water as acid rain causes plant, animal and material damage. Some of the significant ill effects of acid rain are:

Damage to animals

Acid rain chemically strips waterways of necessary nutrients and lowers the pH to levels where plants and animals cannot live. Most of the aquatic animals cannot survive when the pH is less than 4. Some species of fish, such as salmon, die even when the pH is less than 5.5. Certain species of algae and zooplankton are eliminated at pH less than 6. A reduction in the zooplankton and bottom fauna ultimately affects the food availability for the fish population. The problem is most severe downwind of industrial areas where fishing and tourism are major sources of income such as in Norway and Sweden.

Damage to plants

Acidic water is dangerous to plants. Sulphuric and nitric acid rain washes nutrients out of the soil, damages the bark and leaves of trees and harms the fine root hairs of many plants which are needed to absorb water. Leaf pigments are decolorized because acid affects green pigment (chlorophyll) of plants. Agricultural productivity is also decreased. Several non-woody plants, such as barley, cotton and fruit trees like apple, pear, etc., are severely affected by acid rain. Since the acid concentration increases near the base of clouds by density, high altitude trees and vegetation may be exposed to pH levels as low as 3. Unique areas such as the Black Forest in Germany and sugar maples in Vermont (USA) are particularly threatened.

Material damage

Metallic surfaces exposed to acid rain are easily corroded. Textile fabrics, paper and leather products lose their material strength or disintegrate by acid rain.

Building materials such as limestone, marble, dolomite, mortar and slate are weakened on reaction with acid rains because of the formation of soluble compounds.

Thus, acid rain is dangerous for historical monuments.

Acid Rain & Heart Disease

Acid rain is the deposition of acidic components in rain, snow, fog, dew or dry particles that come from sulfur dioxide and nitrogen oxides. These dangerous chemical pollutants can have a severe impact on human health, including pulmonary disorders and heart disease. Much research is being done to combat acid rain for the sake of the environment, aquatic life and human health.

Process of Acid Rain

The process of depositing air pollutants on the Earth's surface is known as atmospheric deposition. These pollutants are derived from natural sources, such as forest fires and volcanoes, or from anthropogenic (man-made) sources, such as electric power plants and automobiles. Atmospheric deposition is both wet and dry. Wet deposition is precipitation (for example, rain and snow), and dry deposition is the settling, impaction, or adsorption of particles in dry weather. If wet deposition is acidic, it is known as acid rain.

Measuring Acid Rain

Because acid rain looks, feels and tastes like clean water, pH measurements are taken to determine its acidity. According to the U.S. Environmental Protection Agency, pure water has a pH of 7.0, and normal rain has a pH of about 5.6. Water is considered acid if the pH is less than 7.0 and alkaline if the pH is greater than 7.0. The lower the pH, the greater is the acidity of the water.

Causes of Acid Rain

Air pollution is the principal cause of acid rain. The burning of fossil fuels, such as coal and oil, from electric power generators forms sulfur dioxide. Automobile fumes cause nitrogen oxides to form. These gases are released into the atmosphere and travel with the wind for hundreds of miles from the originating city to the countryside, harming not only Earth's forests and lakes, but also the health of humanity.

Link Between Acid Rain and Heart Disease

When you breathe the air pollutants (sulfur dioxide and nitrogen oxides) that cause acid rain, symptoms including coughing, shortness of breath, chest tightness, and chest pain can occur. The formulated particles can penetrate deep into the lungs and aggravate heart disease. The high levels of sulfur dioxide and nitrogen oxides associated with acid rain are particularly harmful to senior citizens and people with existing heart disease. As a result of these airborne particles, hospital admissions for heart disease are on the rise as well as higher morbidity rates from this ailment.

Acid Rain Phenomenon

Introduction:

Acid rain is a very dangerous weather phenomenon that can harm an area to a great extent. Usually raindrops carry some amount of acid in it. When the amount of acid goes beyond the normal range, then the rainfall is called acid rain. Acid rain is a result of extreme pollution in certain places on the earth. Acid rain can destroy many things of nature such as various living objects as well as non-living objects. However, acid rain sometimes remains unrecognized and the particular place suffers from this dangerous natural outburst for years.

• The Reason behind Acid Rain:

Acid rain is a result of pollution that includes acidic gases emerged from the factories and vehicles of a place. The level of sulfur dioxide and nitrogen oxide increases in the atmosphere, thus increasing the acidic level in the raindrops.

Acids rain makes the entire atmosphere poisoned in a certain place. It raises the acidic level of the soil. Thus the water bodies like lakes, ponds, streams, etc. are affected. The chemical balance of these water bodies gets disturbed and water becomes poisonous for living beings. Places like Europe, North America, Canada, etc. are mostly affected by the acid rain.

From the above discussion it is clear that the level of sulfur dioxide and nitrogen oxide must be decreased in the atmosphere to stop the menacing effects of acid rain. For this people have to be careful while using their vehicles. Fossil fuels should not be used in cars. In factories also some pollution control equipments must be used to reduce the emission of poisonous gases.