Read this essay to learn about acid rain. After reading this essay you will learn about: 1. Meaning of Acid Rain 2. Occurrence of Acid Rain 3. Chemical Reaction 4. Formation 5. Role of Winds in Acid Rain 6. Adverse Effects 7. Acid Rain and the Present Environment 8. Control.
Essay Contents:
- Essay on the Meaning of Acid Rain
- Essay on the Occurrence of Acid Rain
- Essay on the Chemical Reaction of Acid Rain
- Essay on the Formation of Acid Rain
- Essay on Role of Winds in Acid Rain
- Essay on the Adverse Effects of Acid Rain
- Essay on Acid Rain and the Present Environment
- Essay on the Control of Acid Rain
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Essay # 1. Meaning of Acid Rain:
The term “acid rain” was first used by Robert Angus in 1872. “Literally it means the presence of excessive acids in rain waters.” Acid rain is in-fact cocktail of mainly H2SO4 and HNO3, where the ratio of these two may vary depending upon the relative quantities of oxides of sulphur and nitrogen emitted.
H2SO4 is the major contributor (60-70%) to acid precipitation, HNO3 ranks second (30-40%) and HCl third. Acid rain is in fact a natural phenomenon occurring during any thunderstorm accompanied by heavy lightening or by volcanic eruptions.
However, it is the pollution of the air with nitrogen and sulphur containing gases, emitted by the industry, power station, planes and automobiles that produce acid rain which has alarmed many people because of the increasing potential hazard for environmental degradation including soil and water.
Essay # 2. Occurrence of Acid Rain:
Acidification of environment is a man-made phenomenon. There is now no doubt that most acids come from human activities from cars, homes, factories, and power stations etc. there has always been some acid in rain, coming from volcanoes, swamps and plankton in the oceans, but scientists know that it has increased very sharply over the past 200 years.
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The acidity is mainly associated with the transport and subsequent deposition of oxides of sulphur, nitrogen and their oxidative are produced by combustion of fossil fuels, smelters, power plants, automobile exhausts and domestic fires etc.
The accumulation of these oxides was first reported to be responsible for increasing an acidity in Swedish lakes and Rivers. The acid rain problem has drastically increased due to industrialization. Burning of fossil fuels for power generations contributes to 60-70% of total SO2 emitted globally. Emission of NOx from anthrogenic sources ranges between 20- 90 million tonnes annually over the globe.
The super stack and the mammoth smelters at Sudbury (Ontario) release about 2500 tonnes of SO2 into the air daily. It is the largest stack in the world and serves as a symbol of acid rain problems in North America. Incredibly, this one stack gives of 1% of the total SO2 released worldwide.
Many super stacks constructed recently facilitate long transport of gases and particulate, thus contributing to the wide-spread acid deposition problem facing the United States and Canada today. Highly industrialized areas of the UK, Central Europe, Finland, Norway, Austria, and Switzerland were the net importers of sulphur compounds which contribute much for increasing acidity.
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Essay # 3. Chemical Reaction of Acid Rain:
Chemical Reactions Involved in the Acid Rain:
(i) Oxides of nitrogen like NO reacts with O2 and H2O produces nitrous and nitric acid as follows:
2NO + O2→ 2NO2 + H2O → HNO3 + HNO2
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(ii) Oxides of sulphur also produce H2SO4 as follows:
2SO2 + O2→ 2SO3 + 2H2O → 2H2SO4
Essay # 4. Formation of Acid Rain:
Actually acid rain is the one phase of acid deposition which can either be wet or dry acid rain, snow, dew, fog, frost and mist represent the wet form of deposition, while dust particles containing sulphates and nitrates, settled on earth, is called dry deposition. However, the wet acid rain is much more common.
Every source of energy that we use-be it coal, fuel wood or petroleum products, has sulphur and nitrogen. These two elements, when burnt in atmospheric oxygen, are converted into their respective oxides (SO2 and NOx) which are highly soluble in water. By anthropogenic and by natural sources, oxides of sulphur and nitrogen enter the atmosphere.
S + O2 → SO2 2SO, + O2 → 2SO3
In case of nitrogen, following reactions are involved.
NO + O3 → NO3 + O2 NO2 + O2 → N O3 + O2
NO3 + NO2 → N2O5
Under the humid conditions of air, N2O5 invariably reacts with water vapours to form droplets of HNO3.
N2O5 + N2→ 2HNO3
Some HNO2 is also formed.
N2 O3 + H2O→ 2HNO2
HNO3 and HNO2 then return to the earth’s surface. However, HNO3 can be removed as a particulate or as particulate nitrates after reaction with bases such as NH3 SO3 in humid atmosphere forms droplets of H2SO4
SO2 + 1/2 O2 + H2O→H2SO4
HNO3 and H2SO4 thus formed combine with HCL (emitted from natural and man-made sources) to generate precipitation which is commonly referred to as acid rain.
Acid Rain-An Important Source of Nitrogen:
A recent study conducted by ocean scientists from Florida State University, USA provides evidence of the greater role of atmospheric nitrogen, rather than of ground sources, in controlling the nitrogen levels of rivers.
It was believed that ground sources such as fertilizer runoff from farmland and municipal waste streams contributed to the variation of nitrogen levels in rivers, But scientists from Florida analysed the data from two sources the acid rain measurements of National Atmospheric Deposition Programme and the River Chemistry Studies of US Geological Survey to conclude that the atmospheric deposition of nitrogen plays a major role in quality of water and acid rain is the most important sources of nitrogen.
Essay # 5. Role of Winds in Acid Rain:
The oxides of sulphur and nitrogen are swept up into the atmosphere and can travel thousands of kilometres. The longer they stay in the air, the more likely they are to be oxidised into acids.
For example, a given molecule of SO2 may remain in the atmosphere up-to 40 hours, while a sulphate particle may remain for three weeks. They have enough long life period and so these molecules may be wind transported several kilometres from their point of release.
It has been reported that a molecule of SO2 originated in Ohio might be transported to New York. These are also wind-blown from USA to Canada or vice-versa. Recently it is estimated that 87% of the sulphate in New York and New Jersey and 92% of it. New England has been carried in by long distant transport from the middle west.
Essay # 6. Adverse Effects of Acid Rain:
Acid rain problem is one of the evil in India and is fast spreading in the developing world. The most worrying aspect is that the area affected by acid deposition has been increasing day by day. Its association with our energy consuming world leaves little prospect of alleviation, even with stricter emission controls.
Some of the effects of acid rain are mentioned below:
I. Effect of Acid Rain on Aquatic Biota:
i. Acid rain creates complex problems and their impacts are far reaching. A significant reduction in fish population accompanied by decrease in the variety of species in food chain have been observed. There are 15,000 fishless lakes in Sweden and about 100 such lakes in the Adirondack region of USA, because of increased acidity of the lake. The fishless lakes are now “fish grave yards” and several rivers as twig are acidic.
ii. About 237 lakes in the Adirondack have a pH below 5, creating highly acidic level, lethal for fishes. This acidic water can also leach aluminium form the soil. So the run-off can carry dissolved aluminium to lakes, rivers and streams. It is highly toxic to aquatic animals and cause death of fish by clogging its gills and deprives it of oxygen. Beside this, aluminium can also bind with organic particles, which are also toxic for fishes.
iii. Adirondack ponds, having high acidity levels, were among the first to lose fish population. Juvenile fish, small and large mouth bass and wall eye are extremely sensitive and unable to reproduce at pH levels 5.4 to 5.7.
iv. Northern pike and chain pickerel are quite tolerant to low pH level. Some non- sport species and succumb can survive in this water.
v. Different species react differently to acidified lakes. Adult fish can survive in more acidic water having high concentration of aluminium than fry fish. Brook trout is most acid tolerant while rainbow trout the least. So a few critically affected lakes still have population of mature fish.
vi. Many bacteria and blue green algae are killed due to the acidification, disrupting the whole ecological balance. Acid rain killed fishes in lakes and destroyed trees in a wide swathe across Europe.
II. Effect of Acid Rain on Terrestrial Ecosystem:
i. In 1958, the pH of the rain at Europe was 5.0 and in 1962 the pH of rain at Netherlands was 4.5. This acid rain has damaged leaves of plants and trees and had retarded the growth of Swedish Forests.
ii. In West Germany, about 10% of the forests died and nearly 18 million acres of forests are severely affected by acid rains. Forests in Switzerland, Netherlands and Czechoslovakia have also been damaged by such rains. Actually nutrients like calcium, potassium, iron, and magnesium have been leached away from soil by acids. These nutrients are most essential for the plant growth.
iii. Acid rain has already been an acute problem in North America and Europe, where in has destroyed crops and forests, reducing agricultural productivity. In Canada also, the plants and trees are being destroyed by acid rain pollutants emitted by industries in Northern USA.
iv. Recently the effect of acid precipitation on terrestrial vegetation indicates reduced rate of photosynthesis and growth and increased sensitivity to drought and disease.
v. Acid rain has severely retarded the growth of crops such as pea, beans, radish, potato, spinach, broccoli and carrots etc.
vi. The activity of symbiotic nitrogen fixing bacteria present in the nodules of leguminous family. Is inhibited, thereby destroying the fertility of the soil.
vii. Root systems are damaged by the uptake of aluminium released from the soil. Nitrates may be leached from the soil by acid run off waters.
viii. Acid deposition weakens the trees like pine, spruce, ashes, and rich which can be easily-attacked by pathogens and drought.
ix. Air pollution in England now descends upon Sweden as acid rain. Acidification of soil changes its biology and chemistry. Plant can easily absorb cadmium from the acidified soil. High levels of cadmium in plants are injurious for animals and human beings.
x. D. Bernhard Ulrich of the University of Goettingen in FRG first sounded an alarm when his test of German soils showed high acid inputs in seventies form the atmosphere. He predicted that acids leached nutrients from levels and soils. Trees pulled heavy metal ions, like cadmium, chromium, and aluminium into their systems. These ions are immobile in many soils, but acidic water mobilises them and causes tree damage.
xi. Acidic rain in Japan has damaged 5000 sq. kms of cedar trees in Kanto plain which lies in the North of Tokyo. This area is affected by high acid deposition brought about by air pollutants.
III. Effect of Acid Rain on Lake Ecosystem:
i. Acid rain causes a number of complications in ponds, rivers and lakes where it accumulates as “acid snow”. In summer rapid snow melt gives a jolt of acid water to lakes. This “acid jolt” is most damaging to young fish, algae, insects and to the food chain. Lakes become dead.
ii. Acid lakes have low levels of phytoplankton, snails, clams, oysters etc. having their shells of calcium carbonate, are among the first animals to perish in acidic lakes.
iii. Black fish, mosquitoes, deer fish and other aquatic worms occur abundantly where fishes are eliminated. So they appear to thrive in acid conditions. Dragon fly larvae and water boatmen also flourish in acidified lakes.
iv. The activity of the bacteria and other microscopic animals is reduced in acidic water. So the dead material and other accumulated substances lying on the bottom of lakes are not rapidly decomposed. Thus essential nutrients as nitrogen and phosphorus stay locked up in plant and animal remains. Biomass production is reduced and fish population declines.
v. Aquatic plants such as broad-leafed pond weeds do not grow in acid water. This could affect the feeding and breeding habits of aquatic species.
IV. Effect of Acid Rain on Buildings:
i. Acid rain causes extensive damage to building and structural materials of marble, limestone, slate and mortar etc. limestone is attacked rapidly.
CaCO3 + H2SO4 → CaSO4+ H2O + CO2
The attack on marble is termed as “Stone leprosy”.
ii. In Greece and Italy, invaluable stone statues have been partially dissolved by acid rain. The Taj Mahal in Agra is also suffering at present due to SO2 and H2SO4 acid fumes or air pollutants released from Mathura refinery.
iii. Acid rain also corrodes houses, monuments, statues, bridges, fences and railings that cost the world 1450 million dollars a year. British Parliament Building also suffered damage due to H2SO4 rains.
iv. Due to acidity, levels of heavy metals as Al, Mn, Pb, Cd, Cr, and Cu in water increases beyond the safe limit which indirectly affects the buildings.
v. Acid rains are great threat to British environment. Much of the falling snow in Britain is now highly acidic. If it does not melt, it may turn into a “Pollution time bomb”.
vi. At St. Paul’s Cathedral, precious stonework is being eaten away at the rate of an inch every hundred year. Ornamental stone work on a church in Bristol is corroded by acid in the air.
vii. H2S tarnishes silver and blackens leaded house paints. Ozone produces cracks in rubber. Traces of radioactive elements present in radioactive rain severely damage the buildings.
V. Effect of Acid Rain on Human Beings:
Acidic rain has been found to be very dangerous to the living organisms as it can destroy life. Acidification can play havoc with human nervous system, respiratory system and digestive system by making the person an easy prey to neurological diseases. This happens because these acids produce highly toxic compounds which contaminate the portable water and enter man’s body.
Acidic rains containing air pollutants contribute to a variety of safety hazards, associated with reduced visibility due to smog etc. these contaminants can be nuisance in several aspects and causes adverse health effects.
VI. Diseases Spread by Acid Rain Water:
Microbes in rain water have great influence on terrestrial phase of eco-system. They cause several plant infections or the infections in the respiratory tract of animals. Dissemination of wheat rust due to rains from the Himalayas to the northern plains and from Nilgiris and Pulni hills from south to central India is well-known.
Recent studies on the epidemiology of brown and black rust have shown that quit often spores from southern sources are directly transported to Central India, which are deposited mainly by rains. It has been recognised that such a spread occurs to a distance of more than 600 km, some times without infecting the fields.
Micro-organisms present in rain water also play some role in spread of animal disease especially the foot and mouth disease of cattle and sheep.
Essay # 7. Acid Rain and the Present Environment:
Though acidity of rain water is yet to be adequately monitored, developing countries like India have to cope with this problem of acid pollution. Several industrial areas with pH value of rain water below or close to the critical value have been recorded in Delhi, Mumbai, Pune, Nagpur and Kolkata.
In India, Acidity has been mainly due to SO2 from coal fired power plants and petroleum refinery, emitting about 85 tonnes annually. According to a study made be “BARC Air Monitoring Section”, the average pH value of acid rain at Delhi is 6.21.
Kolkata 5.80, Chennai 5.85, Hyderabad 5.73 and Mumbai 4.80. The situation may even worsen in future due to increased installation of thermal power plant by NTPC, several industries discharging sulphur oxides and consequent increase in coal consumption.
Recently it has been estimated that the total emission of SO2 in India from fossil-fuel burning has increased from 1.38 million tonnes in 1966 to 3.20 million tonnes in 1979. It is nearly 21 % increase as compared to the increase of 8.4 in USA during the same period.
Essay # 8. Control of Acid Rain:
There is an urgent need for proper regular monitoring to provide timely warnings about acidification of our environment. Short-term control of acid deposition problem can be achieved by using lime. New York has been liming the lakes and ponds since 1959.
Recently, the United States limed Adirondack lakes to prevent the eradication of brook trout. In July 1986, Adirondack Park Agency’ has published a report stating that only a few lakes have characteristics which make liming possible and economically feasible.
The cost of liming a lake is nearly 40 dollars per acre with volunteer assistance and vehicular access. If planes or helicopters are used, liming cost rises to above 200 dollars per acre.
According to citizens guide, it is mentioned that “There is no question that Adirondack lakes, liming is not a solution of problems brought to Adirondack fisheries by acid rain; nor limiting a substitute remedy for the pressing need to reduce air-brone pollutants. However, even more important is the question of what effects liming have on all the biological elements of lakes and ponds.”
Ecologist Voker Hohen of the State University New York, Albany has recommended to apply lime to entire water, sheds including trees and forests, rather than to Adirondacks lakes. Dr. Gene Linkens to Cornell University argues that along with advanced research, we also need tough ‘legislation’ which can possibly reduce the extent of acid-forming pollutants being released into the atmosphere.
A ‘bill’ has been introduced recently in USA that would enhance to diminish the acid deposition problem. It would require 10 million tonnes reduction in SO2 emissions in 31 eastern states during next decade.
The Adirondack Park Agency and the New York States have supported the adoption by Congress of “Federal Clean Air act.” In India, where 4 to 8 x 107 tonnes of SO2 dissolve in the oceans annually, efforts are made to monitor the levels of sulphur and nitrogen oxide emissions as an important constituent of air pollutant and adopt the ‘Clean Air Act.’