Pollution
Pollution is an undesirable change in the physical, chemical or biological characteristics on air, water and land that will harmfully affect human life and the lives of desirable species. Pollutants are materials or factors which cause adverse effect on the natural quality of any component of the environment. They are the waste products or by-products of the materials we make use or throw away. Pollution can be defined as "the introduction by humans, deliberately or inadvertently, of substances or energy (heat, radiation, noise) into the environment resulting in a deleterious effect".
Pollution and contamination are often used to mean the same. But pollution is different from contamination. Contamination is the presence of elevated concentrations of substances in the environment, food etc., which may not necessarily be harmful or a nuisance. Pollution involves contamination, but contaminations need not constitute pollution. Pollution can be 'primary', having effect immediately on release to the environment; or 'secondary', the product of interaction after release with moisture, other pollutants, sunlight, etc. Pollutants include solid, liquid or gaseous substances present in greater than natural abundance, produced due to human activity, which have a detrimental effect on our environment. The nature and concentration of a pollutant determine the severity of its detrimental effects on human health.
The various types of pollutions, namely, air, water, soil, marine, noise, thermal and nuclear pollution (along with their causes/sources, effects and control measures) are discussed below.
AIR POLLUTION
Air pollution is basically the presence of foreign substances in air in excessive concentration which adversely affects the well being of the individual or causes damages to property, Indian Standards Institute define air pollution as, "Air pollution is the presence in ambient atmosphere of substances, generally resulting from the activity of man, in high concentration, present for a sufficient time and under circumstances which affect the comfort, health or welfare of persons or the full use or enjoyment of property"
Causes of Air Pollution
The air may become polluted by natural causes such as volcanoes, which release ash, dust, sulphur and other gases, or by forest fires caused by lightning. However, unlike pollutants from human activity, naturally occurring pollutants tend to remain in the atmosphere for a short time and do not lead to permanent atmospheric change. Pollutants that are emitted directly from identifiable sources are produced both by natural events (eg, dust storms and volcanic eruptions) and human activities (emission from vehicles, industries, etc.). These are called primary pollutants. There are five primary pollutants that together contribute to about 90% of the global air pollution. These are carbon oxides (CO and CO,), nitrogen oxides, sulfur oxides, volatile organic compounds (hydrocarbons), and suspended particulate matter (SPM). The pollutants that are produced in the atmosphere when certain chemical reactions take place among the primary pollutants are called secondary pollutants; eg. sulfuric acid, nitric acid, carbonic acid, etc.
Effect of Air pollution on human health, Animals, plants and property
The impurities in the inhaled air can affect human health in a number of ways, depending upon the nature and concentration of the pollutants,of exposure, and age group of the receptor. Prolonged smoking or exposure to air pollutants causing to diseases such as lung cancer, asthma, chronic bronchitis and emphysema. Elderly people, infants, pregnant women and people with heart disease, asthma or other respiratory diseases are especially vulnerable to air pollution. Many volatile organic compounds and toxic particulates can cause mutations, reproductive problems or cancer. The repeated inhalation of ozone causes coughing, chest pain, breathlessness and irritation of the eye, nose and the throat.
The effect of air pollution on animals is more or less similar to that of human beings and the common effects include the following.
■ Accumulation of airborne contaminants on the vegetation and subsequent poisoning of animals when they consume the contaminated vegetation.
■ Reduction in yield from cattle.
■ Symptoms could include lack of appetite, rapid loss in weight,lameness, diarrhoea and subsequently death.
In case of plants, air pollution mainly affects the leaves and causes the following typical symptoms.
■Necrosis: Killing or Collapse of tissue.
■Chlorosis: Reduction in the chlorophyll.
■ Abcission: Dropping of leaves.
■Epinasty: Downward curvature of the leaf due to higher rate of growth on the upper surface.
Control measures for air pollution
Control technologies are only one part of the solution for reducing the effects of air pollution. Preventative such as changing raw materials, process conditions and procedures, and preventative maintenance should be considered prior to employing control or treatment technologies and shoul be a continual part of the overall air pollution control programme. The following are few specific examples of modification of process conditions and/or maintenance practices for air pollution control.
■ Controlling fugitive dust emissions by watering or using oil on roads.
■Increasing routine inspection of equipment and preventative maintenance. eg. replacing leaky valves and pipes.
■Applying zoning or planning ordinances to distribute or minimise the impact of air pollution sources in a community.
■ Material substitution. eg. changing the fuel. For instance, sulphur dioxide emissions may be controlled completely by changing to a low sulphur coal or to fuel oil.
If required emission reductions cannot be achieved by one or some combination of the above alternatives, control technology is necessary. One of the effective means of controlling air pollution is to have proper equipmen in place. This includes devices for removal of pollutants from the fuel gases through scrubbers, closed collection recovery systems (through which it is possible to collect the pollutants before they escape), the use of dry and wet collectors, filters, electrostatic precipitators, etc. Building higher smoke stacks facilitates the discharge of pollutants as far away from the ground as possible. Industries should be carefully located so as to minimise the effects of pollution after considering the topography and the wind directions.
Air Quality Management
At present, India does not have a well-established system of monitoring air pollution. When air quality monitoring began in India in the late 1960s, planners focused only on a few pollutants, viz. sulfur dioxide, nitrogen oxides and suspended particulate matter. Other pollutants such as carbon monoxide and lead were monitored only on a limited scale. The treat from other air toxins like benzene, ozone, and other small particulates is unknown as these are not monitored at all. A database on ambient air quality in Indian cities has been prepared by the monitoring networks of the National Environmental Engineering Research Institute (NEERI), Nagpur. The Central Pollution Control Board (CPCB) initiated its own National Ambient Air Quality Monitoring (NAAQM) programme in 1985. Data to the NAAQM is supplied by the respective State Pollution Control Boards, which is then transmitted to the CPCB. Experts feel that the present air quality monitoring network cannot capture the true profile of urban air pollution due to the lack of adequate monitoring stations.
The Ambient Air Quality Standards (These are permissible exposures of all living and non-living things for 24 hours per pay, 7 days per week) in India developed by the CPCB are given in Table-1.
Air quality management as a well-defined programme has yet to emer in India. We need a much stronger system of air-quality management with continuous monitoring of air if we are to have a better quality of air.
WATER POLLUTION
Water is the essential element that makes life on Earth possible. Withou water there would be no life. Although 71% of Earth's surface is covered by water, only a tiny fraction on this water is available to us as fresh water, About 97% of the total water available on Earth is found in the oceans and is too salty for drinking or irrigation. The remaining 3% is fresh water this, 2.997% is locked in ice caps or glaciers. Thus, only 0.003% of the Earth's total volume of water is easily available to us as soil moisture, ground water, water vapor and the water in lakes, streams, rivers and wetlands. This makes water a very precious resource.
Generally speaking, water pollution is a state of deviation from the condition, whereby its normal properties and function are affected. Water pollution can be defined as "the presence of some foreign substances or impurities in water in such quantity so as to constitute a health hazard lowering the water quality and making it unfit for use".
Causes of Water Pollution and its Effects
There are several classes of common water pollutants. They are:
1. Disease-causing agents
Bacteria, viruses, protozoa and parasitic worms that enter water from domestic sewage and untreated human and animal wastes. Large amounts of human waste in water increases the number of bacteria, which caus gastrointestinal diseases.
2.Oxygen-depleting wastes
These are organic wastes, which can be decomposed by oxygen consuming bacteria. Large populations of bacteria supported by these wastes up the oxygen present in the water in order to degrade the wastes quality. In the process, this degrades the water quality. If too much organic matter is added to the water, all the available oxygen is used up. This causes fish and other forms of oxygen-dependent aquatic life to die.
3. Water-soluble inorganic chemicals
These are acids, salt and compounds of toxic metals such as mercury and lead. levels of these chemicals can make the water unfit to drink, harm fish and other aquatic life, reduce crop yields, and accelerate the corrosion of equipment that is in contact with this water.
4. Inorganic plant nutrients
These are water-soluble nitrates and phosphates that cause the excessive growth of algae and other aquatic plants. This excessive growth due to added nutrients is called eutrophication. This may interfere with the use of the water by clogging up water-intake pipes, changing the taste and smell of the water and causing a buildup of organic matter. As the organic matter decays, the oxygen levels decrease and fish and other aquatic species die.
5. Organic Chemicals
These includes oil, gasoline, plastics, pesticides, cleaning solvents, detergents and many other chemicals. These are harmful to aquatic life and human health. They enter the water directly from industrial activity, either from improper handling of chemicals in industries and usually from the improper and illegal disposal of chemical wastes.
6. Sediment of Suspended Matter
These are insoluble particles of soil and other solids that become suspended in water. This occurs when the soil is eroded from the land and by disposal of sewage and industrial effluents in to water. High levels of soil particles suspended in water interfere with the penetration of sunlight. This reduces the photosynthetic activity of aquatic plants and algae, disrupting the ecological balance of the aquatic bodies. When the velocity of water in streams and rivers decreases, the suspended particles settle down at the bottom as sediments. The excessive sediments that settle down destroy the feeding and spawning grounds of fish, clogs and fills lakes, artificial reservoirs, stream channels and harbours.
7. Radioactive Substances
The main human activities which are responsible for radioactive pollution are use of radioactive materials in power plants and nuclear weapons; use of radioactive isotopes in medical, industrial and research applications; and mining and processing of ores to produce usable radioactive substances. The radioactive isotopes that are water soluble can be concentrated in various tissues and organs as they pass through food chains and food webs. The ionizing radiation emitted by such isotopes can cause birth defects, cancer and genetic damage.
8. Heat
Large quantity of water is heated when it is used in the cooling towers of thermal power plants. When this hot water is discharged into the nearby water bodies it causes an increase in its temperature: This increase in water temperature lowers dissolved oxygen content and changes the breeding cycis of various aquatic organisms.