Ozone Layer Depletion

Ozone layer depletion refers to the decline in amount of ozone in Earth's stratosphere (commonly known as Ozone layer) and a large springtime decrease in stratospheric Ozone around the Antarctic region.

Stratospheric ozone is highly beneficial as it protects the living organisms on the Earth's surface from harmful UV radiations of the sun. Ozone is continuously formed and removed in the stratosphere and thus there is an apparent equilibrium in the ozone layer with the concentration of ozone remaining constant.

However satellite data indicated a large hole in the ozone layer over Antarctica. The main process which was responsible was found to be catalytic destruction of ozone by atomic halogens. The main source of these atomic halogens are Chlorofluorocarbons (CFC), Hydrochlorofluorocarbons (HCFC) and Chlorofluorobromine. These gases are used as refrigerants, solvents, propellants and foam-blowing agents. They are very stable and are inert in lower atmospheric regions but get destroyed when exposed to UV rays resulting in release of atomic halogens. This destruction of ozone layer by atomic halogen takes place through the following processes as outlined below.

CF₂Cl₂ + UV Radiations → CF₂Cl + Cl

This free chlorine atom then acts as a catalyst for the following reactions.

Cl + O₃ → ClO + O₂
ClO + O → Cl + O₂
O₃ + O → 2O₂

The chlorine is thus free to repeat after this two-step cycle. On an average, a single chlorine atom is able to react with 100,000 ozone molecules before it is removed from the catalytic cycle. This fact plus the amount of chlorine released into the atmosphere yearly by chlorofluorocarbons (CFCs) and hydrochlorofluorocarbons (HCFCs) demonstrate how dangerous CFCs and HCFCs are to the environment.

Global Warming

Global warming is the increase of Earth's average surface temperature due to the effect of greenhouse gases like carbon dioxide which is produced due to burning of fossil fuels or from deforestation. These greenhouse gases trap the heat radiated from the Earth's surface and thus increase the temperature. This phenomenon is known as greenhouse effect.

Greenhouse gases such as water vapor, carbon dioxide, methane, nitrous oxide, ozone and chlorofluorocarbons (CFC) absorb most part of radiations from Earth's surface. The atmosphere is, thus, heated and then some energy is radiated back to Earth while some of it goes to space. If there were no greenhouse gases, all the energy would have been radiated to the space and the our planet would have been very cold. Hence greenhouse gases are essential for maintaining the Earth's temperature at the present conditions. However increase in concentration of greenhouse gases beyond acceptable limit will increase absorption of radiations and increase the Earth's surface temperature.

Effects of Global Warming

- Melting of ice caps and glaciers
- Rising sea levels

- Changes in rainfall patterns
- Widespread decrease of flora and fauna
- Spread of diseases like malaria, dengue etc.
- Loss of plankton due to warming seas

Sources of Pollution

An air pollutant is a substance in the air that can have adverse effects on human beings and other living things. The substance may be solid particles, liquid droplets or gases. It can be of natural origin or man-made.

The air pollutants are classified into two main types:

1. Primary Pollutants

2. Secondary Pollutants

1. Primary Pollutants

These substances are emitted directly into the atmosphere. Carbon oxides, sulfur oxides and nitrogen oxides emitted by automobiles are examples of primary pollutants.

2. Secondary Pollutants

These substances are not emitted directly into the atmosphere, but are formed by various physical processes in the atmosphere. Ground level ozone and peroxyacetyl nitrate (PAN) are examples of secondary pollutants.

Air Pollution: Introduction

Air pollution is the introduction of harmful substances at an undesirable concentration into the Earth's atmosphere which make the air unsafe for living.

Air is precious and is essential for sustaining life on the planet. It provides oxygen required for respiration, carbon dioxide for photosynthesis, and nitrogen for synthesis of amino acids and proteins. The ozone layer in stratosphere absorbs harmful UV rays, thus protecting the living organisms from harmful effects of these radiations.

Any change in composition and quality of air caused by introduction of harmful substances can affect life on Earth severely. The main sources of air pollution are automobile emissions, burning of fossil fuels and industrial processes. Naturally occurring processes like volcanoes, dust storms, forest and grassland fires also cause air pollution.

Environmental Management

Environmental degradation and pollution are among the worst effects of human development and population growth. The over-exploitation of natural resources and pollution of the environment is severely affecting all living beings including humans. Therefore, at present, the need to protect the environment and conserve resources for future generations is being felt more than ever. A well planned strategy of environmental management can help deal with this difficult task.

Definition

Environmental management is the management of interactions between human society and the environment and also the study of the resultant impact on natural environment.

Objectives of Environmental Management

- Restrict and regulate over-exploitation of natural resources
- Prevent environmental degradation
- Maintain quality of environment
- Maintain ecological balance
- Implement strict rules and regulations

Environmental Pollution

Environmental Pollution is defined as an undesirable change in physical, chemical and biological characteristics of air, water and soil due to anthropogenic activities which may harmfully affect the survival or development of living organisms.

Pollutants

Any biotic or abiotic factor or any physical agent which when present in excess makes any portion of the environment undesirable for survival is termed as pollutant.

Effects of pollution

Pollution has numerous negative effects on the environment and subsequently on living organisms. Extinction of sensitive organisms, spreading of unknown diseases and shortening of lifespan of living organisms including human beings are some of the effects of pollution.

Renewable Resources

A renewable resource is a resource which can be used repeatedly since they are replaced from time to time through natural processes. Such resources can be classified into two types:

1. Conventional renewable resources
2. Non-conventional renewable resources

1. Conventional renewable resources

Water

Water is a renewable resource and has a life cycle which should be properly maintained. However, its mismanagement and overuse may create shortage of water.

Forest

Forests are an important part of our planet. They help to regulate climatic conditions, provide timber, medicinal plants, fruits, and house a variety of plants and animals. Due to large scale deforestation, we are losing vast areas of forests rapidly. To compensate the loss, afforestation should be done to ensure that the forest cover remains the same.

Wildlife

Animals are a renewable resource since they have a life cycle and reproduce. However indiscriminate use and loss of habitat is threatening the wildlife of Earth. Proper management and public awareness is therefore necessary to maintain wildlife as a renewable resource.

2. Non-conventional renewable resources

Solar energy

It is the prime source of energy for the biological world. Solar radiations are abundant in many countries which can be tapped and converted to electrical energy using photocell.

Wind energy

Wind blows at a high speed in many locations of the world. The wind energy can be converted to electrical energy using suitable technology such as wind turbines.

Tidal energy

Waves and tides at sea can be converted to electrical energy using a natural or artificial waterfall which rotates a turbine in order to produce electricity.

Atomic energy

Radioactive elements are utilized to harness energy in atomic reactors. The enormous heat produced is used to generate steam which is used to run turbines in order to produce electricity.

Geothermal energy

Steam from hot springs is used to generate steam which is utilized to run turbines in order to produce electricity.

Types of Resources

Resources are of two types:

1. Renewable or inexhaustible resources
2. Non-renewable or exhaustible resources

1. Renewable or inexhaustible resources

A renewable resource is a resource which can be used repeatedly since they are replaced from time to time through natural processes. Some renewable resources like plants and animals are naturally replaceable but they might become extinct if used at a faster rate than the rate at which they are replaced. However some resources like sunlight, wind energy, atomic energy etc. are abundantly available and are hardly affected by human activities.

2. Non-renewable or exhaustible resources

A non-renewable resource is a resource which neither have a life cycle nor can be recycled. These resources cannot be regenerated, once used, and are hence exhaustible as their deposits are limited. They take millions of years to be regenerated and therefore cannot be renewed in our lifetime or even a nation's lifetime. When used indiscriminately, these resources can be exhausted. Examples are fossil fuels like coal, petroleum etc,

Resources and Resistances

Everything in the environment surrounding us can be classified into three categories namely resources, resistances and neutral stuff.

Resources

A resource is a means, which may or may not be a material, that has specific functions and can be utilized to fulfill the needs and wants of individual and the society. Resources may be natural such as air, water and land or human resources such as population or cultural resources such as knowledge.

Resistances

A material or energy which tends to prevent the formation and development of a resource is known as resistance. Resistances may be natural such as cyclones, flood and drought or human resistance such as population growth or cultural resistance such as superstitions,

Neutral Stuff

Those materials which are neither resources nor resistances are called neutral stuff. These things themselves have no utility but they do not pose any resistance in the formation of other resources.

The Four Spheres of Earth

The four spheres of Earth are:

1. Atmosphere
2. Lithosphere
3. Hydrosphere
4. Biosphere

1. Atmosphere

Atmosphere is the thick, gaseous cover of air surrounding the planet Earth. It protects and sustains life on the planet by absorbing harmful cosmic and ultraviolet solar radiations, maintaining heat balance and providing oxygen and carbon dioxide gases which are essential for respiration and photosynthesis respectively.

2. Lithosphere

Lithosphere is the hard and rigid outer part of the Earth consisting of the crust and uppermost mantle. The topmost part of the solid earth, consisting of weathered rocks, minerals and organic matter, is known as soil.

3. Hydrosphere

Hydrosphere is the collective mass of water found both on the surface and beneath the surface of Earth. It includes water in all forms including oceans, rivers, lakes, pond, stream, glaciers, polar ice caps and groundwater.

4. Biosphere

Biosphere is the part of Earth where living organisms exist and interact with each other as well as with non living things. Biosphere consists of plants, animals and microorganisms. It penetrates into all the other spheres of Earth namely atmosphere, lithosphere and hydrosphere.

Classification of Environment

Environment is classified into two types:

1. Natural environment
2. Man-made environment

1. Natural environment

Natural environment is composed of all biotic and abiotic components of environment which are not man-made. This environment encompasses the interaction of all living beings, climate, weather, and natural resources that affect human survival and activity.

2. Man-made environment

Man-made environment is composed of buildings, transportation, dams, stadiums and all other things which have been developed by human beings for their benefit and use.

What is Environment?

Definition: Environment is defined as the sum total of physical, chemical, and biological factors which surround and affect an organism or an ecological community.

The word environment has been derived from the French word environ which means 'to surround'.

Animate and inanimate objects together constitute the natural environment. However, living things do not simply exist in their environment. They constantly interact with it. Organisms change and adapt themselves in response to conditions in their environment. The environment is dynamic and it varies with time as well as geographic location. In the environment there are interactions between plants, animals, soil, water, temperature, light, and all other living and non-living things. Living organisms like plants and animals including human beings draw nourishment from the environment as they grow, develop, reproduce, and ultimately perish in the environment.