1.(a)An undesirable change in the physical, chemical or biological characteristics of the air making itharmful for the living organisms (including man) is termed air pollution.In simple words, addition of unwanted and harmful substances in the air or increase in thequantities of constants of air beyond the normal level that affects the living organisms is called airpollution. Agents or substances that pollute the air are called air pollutants
(b)Air is needed for breathing by humans, other land animals and many aquatic organisms. Itspollution can, thus, affect human health as well as human wealth (domestic animals, crop plans,cultural assets etc.) some common harmful effects of air pollution are :-
1) Respiratory Problems:- Various pollutants of air such as sulphur dioxide (SO2) and oxidesof nitrogen (NOx) are acidic harmful gases. When inhaled alongwith air, these affect the respiratory passage leading to breathing difficulties. These may cause bronchitis, asthma and lung cancer.Similarly, inhalation of polluted air containing dust, cement dust, asbestos dust, pollens etc. maycause sneezing and allergy. Continuous inhalation of these pollutants can cause asthma andtuberculosis (T.B).
2) Carbon monoxide poisoning:- Another toxic air pollutant is carbon monoxide (CO). It isemitted from motor vehicles as one of the exhaust gases, and also from cigarette smoke. It affects thecentral nervous system. If it is present in large quantities in the air, then the polluted air can lead to‘carbon monoxide poisoning’.
3) Acid rain:- It literally means that the rain water contains excessive amounts of acids. Acidrain increases the acidity of the soil, there by affecting land plants and animals. It also increasesacidity of the water in water bodies thereby affecting aquatic life. Acid rain also corrodes metals,painted surfaces, and slate, stone and marble. Our heritage monuments, buildings and statues arethreatened by the corrosive action of acid rain.
4) Depletion of ozone Layer:- Ozone layer or ozonosphere lies about 18-29 km above in theatmosphere . It has high concentration of ozone and is commonly called the ozone shield. This layerabsorbs UV radiations and hence protects the life on the earth from harmful effects of UV radiations.Ozone layer is being depleted by air pollutants. The causes of depletion of ozone shield and theeffects of ozone depletion are discussed later in this chapter.
5) Global Warming (Green House Effect):- This global warming phenomenon occurs due togreen house effect. Man is adding large amounts of ‘green house gases’, particularly carbon dioxide,methane and oxides of nitrogen to the atmosphere by burning of fossil fuels in homes, industries,transport vehicles; burning associated with agricultural practices as well as by deforestation. Thesegreen house gases trap the infra-red radiations reflected by the earth .this heats up the atmosphere.
2. Greenhouse effect is the progressive warming up of the earth’s surface due to the blanketing effect of man-made carbon dioxide in the atmosphere. The greenhouse gases increase the temperature of the earth's surface and lower atmosphere.
Name of the green house gases are Carbon dioxide, nitrous oxide, methane and CFC’S.
3.The movement of minerals occurs by the operation for different chemical cycles that keep on passing the materials from organisms to the environment and vice versa. Such a cyclic process, occurring in nature is called biogeochemical cycle.
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5.An undesirable change in the physical, biological or chemical qualities of water (due to addition for foreign organic, inorganic, biological or radioactive substances) that adversely affects the aquatic life, and makes water less fit or unfit for use, is called water pollution.
SOURCES OF WATER POLLUTION:-
1) Sewage and other wastes: Sewage is the waste water from homes, animal houses or food producing plants. Sewage includes human excreta, paper, cloth pieces, soap and detergents etc. wastes of rural areas, towns and cites are dumped into ponds, lakes, rivers etc. due to large amounts of dumped waste, water loses its self purifying ability and thus becomes unfit for human consumption. Decomposition of sewage etc. is an aerobic process. It needs more oxygen in water.
2) Industrial effluents: Effluents from breweries, tanneries , dying textiles, paper and pulp mills, sugar mills etc., contain a variety of inorganic and organic and organic pollutants such as oils, greases, plastics , plasticizers, DDT, acids, alkalies, dyes etc., are flown into rivers. These cause water pollution.
3) Agricultural discharges: These include chemicals of fertilizers and pesticides. Fertilizers and pesticides are seed to increase crop yield and to protect crop from pests.
4) Industrial wastes: Heat and radioactive substances are the pollutants of thermal and nuclear plants. Nuclear power plants are located close to water bodies. Their waster water affects the aquaticlife causing death.