Science

Topics: Ozone depletion, Ozone, Air pollution Pages: 20 (6491 words) Published: October 6, 2013
Science Folio
Chapter 5
B6D5E1
Title: Importance of maintaining the cleanliness of air

Introduction
The atmosphere of Earth is a layer of gases surrounding the planet Earth that is retained by Earth's gravity. The atmosphere protects life on earth by absorbing ultraviolet solar radiation, warming the surface through heat retention (greenhouse effect), and reducing temperature extremes between day and night. One of the most important factors drawing international attention which is a dangerous threat to the ecosystem is air pollution. The atmosphere, which makes up the largest fraction of the biosphere, is a dynamic system that continuously absorbs a wide range of solids, liquids and gases from both natural and manmade sources. These substances travel through air, disperse and react with one another and with other substances both physically and chemically. Most of these constituents, eventually find their depository such as the ocean, or to a receptor such as man. Various amounts of contaminants continuously enter the atmosphere through both natural and manmade processes present on the earth. That portion of these substances which interacts with the environment to cause toxicity, disease, aesthetic distress, physiological effects or environmental decay, has been labeled by man as a pollutant. Air pollution is the contamination of the atmosphere by any toxic or radioactive gases and particulate matter as a result of human activity. There are 5 major air pollutants such as carbon monoxide (CO), sulphur oxides (SO, SO2, SO3), particulates, hydrocarbons, and photochemical oxidants.

The composition of air
The average percentage of its components by volume
Nitrogen
78%
Oxygen
21%
Inert gases & Others
0.97%
Carbon dioxide
0.03%

Air Pollution

Air pollution is the introduction into the atmosphere of chemicals, particulates, or biological materials that cause discomfort, disease, or death to humans, damage other living organisms such as food crops, or damage the natural environment or built environment. The atmosphere is a complex dynamic natural gaseous system that is essential to support life on planet Earth. Stratospheric ozone depletion due to air pollution has long been recognized as a threat to human health as well as to the Earth's ecosystems.

Pollutants
A substance in the air that can be adverse to humans and the environment is known as an air pollutant. Pollutants can be in the form of solid particles, liquid droplets, or gases. In addition, they may be natural or man-made. Pollutants can be classified as primary or secondary. Usually, primary pollutants are directly produced from a process, such as ash from a volcanic eruption, the carbon monoxide gas from a motor vehicle exhaust or sulfur dioxide released from factories. Secondary pollutants are not emitted directly. Rather, they form in the air when primary pollutants react or interact. An important example of a secondary pollutant is ground level ozone — one of the many secondary pollutants that make up photochemical smog. Some pollutants may be both primary and secondary: that is, they are both emitted directly and formed from other primary pollutants.

What causes air pollution?

Air pollution can result from both human and natural actions. Natural events that pollute the air include forest fires, volcanic eruptions, wind erosion, pollen dispersal, evaporation of organic compounds and natural radioactivity. Pollution from natural occurrences is not very often.

Human activities that result in air pollution include:

1. Emissions from industries and manufacturing activities
Have you seen a manufacturing company before? You will notice that there are long tubes (called chimneys) erected high into the air, with lots of smoke and fumes coming out of it. Waste incinerators, manufacturing industries and power plants emit high levels of carbon monoxide, organic compounds, and chemicals into the air....
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