Air Pollution

AIR POLLUTION

Definition
Air pollution may be defined as the presence in the air (outdoor atmosphere) of one or more contaminants or combinations thereof in such quantities and of such durations as may be or tend to be injurious to human, animal or plant life, or property, or which unreasonably interferes with the comfortable enjoyment of life or property or conduct of business.
Air pollution only occurs outdoors.The atmosphere is composed of 78% of nitrogen, 21% of oxygen, 1% carbondioxide, remainder consist of water vapor, trace amount of several other gases such as hydrogen, neon etc.

Air Pollutant
It is a substance or effect dwelling temporarily or permanently in the air , which adversely alters the environment by interfering with the health, the comfort, or the food chain, or by interfering with the property values of people.
A pollutant can be solid , liquid or gas .
It may originate from a natural or human source (or both).
However, it is widely accepted that even a small change can have a significant adverse effect on the climate, ecosystem and species on the planet.
It may originate from both natural and human sources .
Natural sources include dust, forest fires, volcanic eruptions etc.
Human sources include emissions from vehicles, industries etc.

Types of Pollutants

Primary pollutants : are those which are emitted directly into the troposphere from both natural and human activities. There are five primary pollutants – carbon oxides, nitrogen oxides, sulfur oxides, suspended and particulate matter.

Secondary pollutants : when some of the primary pollutants may react with one another or with the basic components of air to form new pollutants eg: sulfuric acid, nitric acid, carbonic acid etc.

Pollutant -Sources -Effects
Carbon Monoxide (CO) -Cigarette smoking, motor vehicle exhaust-Reduces oxygen carrying capacity of blood ,triggers heart attack, causes collapse, coma etc.

Nitrogen Dioxide -Burning of fossil fuel, power & industrial plants. -Lung irritation, aggravates asthma, bronchitis etc.

Sulfur Dioxide -Coal burning in power plants & industrial processes-Breathing problems, bronchitis, reduces visibility etc.

Ozone -Chemical reaction with VOCs by cars & industries.-Heart disease, eyes, nose & throat irritation, cough etc.
Suspended Particulate Matter - Burning coal in power & industrial plants, diesel in vehicles, agriculture, construction. -Nose & throat irritation, lung damage, cancer, shortens life, asthma.

Lead - Metal refineries, storage batteries, lead manufacture. -Accumulates in the body, brain & other nervous system damage, mental retardation.

Effect on Vegetation
Chronic exposure of leaves to air pollution can break down the waxy coating that helps prevent excessive water loss and leads to damage from diseases, drought, reduces nutrient uptake and cause the leaves to turn yellow, brown or drop off altogether.

Green House Effect

Atmospheric scientists first used the term 'greenhouse effect' in the early 1800s. At that time, it was used to describe the naturally occurring functions of trace gases in the atmosphere and did not have any negative connotations. It was not until the mid-1950s that the term greenhouse effect was coupled with concern over climate change. And in recent decades, we often hear about the greenhouse effect in somewhat negative terms. The negative concerns are related to the possible impacts of an enhanced greenhouse effect. It is important to remember that without the greenhouse effect, life on earth as would not be possible.

Greenhouse Effect is the build up of greenhouse gases like carbon dioxide in the atmosphere. These gases act like a blanket and trap heat, thereby leading to global warming. While the earth's temperature is dependent upon the greenhouse-like action of the atmosphere, the amount of heating and cooling are strongly influenced by several factors. The sun heats the Earth; solar radiation passes through the atmosphere, and is absorbed at the Earth’s surface. This heat is emitted from the surface as infra-red radiation. This infra-red radiation cannot escape the atmosphere easily. Instead, some is trapped by a number of gases, hence we have Greenhouse Effect.

Green House Gases

Two greenhouse gases with the largest concentrations are water vapour controlled by the hydrological cycle and carbon dioxide controlled by the carbon cycle. Methane , nitrous oxide , and a few other gases are greenhouse gases
Carbon dioxide is one of the greenhouse gases. Carbon dioxide is produced when the fuel is burnt. Plants convert the carbon dioxide back to oxygen but the release of carbon dioxide from human activities is higher than the world’s plants can process. The situation is made worse since many of the earth’s forests are being removed, and plants life is being damaged by acid rain. Thus the amount of carbon dioxide in the air is continuing to increase. This build up acts like a blanket and traps heat close to the surface of the earth. The planet is losing less heat and as a result we are beginning to experience Global Warming.

GLOBAL WARMING
Since the beginning of the industrial revolution around 1750 ther has been a sharp rise in :
•The use of fossil fuels which releases large amounts of the greenhouse gases into the troposphere,
•Deforestation and clearing and burning of grasslands to raise crops, which release carbon dioxide and nitrous oxide into the atmosphere,
•Use of inorganic fertilizers which release nitrous oxide into the troposphere.
The increased inputs of carbon dioxide and other greenhouse gases from human activities will :
•Enhance the earth’s natural greenhouse effect,
•Raise the average global temperature of the atmosphere near the earth’s surface.
This enhanced greenhouse effect is called Global Warming

EFFECTS OF GLOBAL WARMING

Warming driven changes: The planet had been heating at the rate of 4 degrees Celsius per century in the last twenty years :
•Warming is causing the breakup of Antarctic ice shelves.
•High above the oceans, most of the earth’s glaciers are retreating – Peruvian Andes & Greenland ice sheet.
•The Arctic sea has thinned by 40 percent in the last two decades.
•Altered the timings of the seasons because of the buildup of atmospheric carbon dioxide.
Sea level: A 20 cm rise by 2030 is expected to result from glacial melting and from the thermal expansion of the oceans as water temperature rises, increasing the risk of flooding.

Water resources : Global rainfall patterns will change. This will have serious global implications , droughts & floods will become more common, water quality will suffer owing to an increase in algal blooms.

Terrestrial ecosystems : Many plants & animal species will have problems adapting , which may result in risk from extinction, whereas more tolerant varieties will thrive.

Human health : There is likely to be an increase in the spread of certain diseases – malaria, heat induced deaths are likely to increase, urban air pollution is likely to get worse.

Economic consequences : Rise in disaster relief costs to governments & escalating losses to the world’s property.