Lichens also absorb sulphur dioxide dissolved in water. Lichens are widely used as environmental indicators or bio-indicators. If air is very badly polluted with sulphur dioxide there may be no lichens present, just green algae may be found. If the air is clean, shrubby, hairy and leafy lichens become abundant. Answer : (b)

Gaseous criteria pollutants, as well as volatile organic compounds (VOCs) and other gaseous air toxics, are controlled by means of three basic techniques: absorption, adsorption, and incineration (or combustion). Answer : (a)

Flocs are masses of bacteria associated with fungal filaments to form mesh like structures and helps in sewage treatment. Flocs consume major part of organic matter in primary effluent and reduces BOD which in turn reduces the polluting potential. Answer : (b)

Carbon dioxide contributes 60% to global warming. Freons or CFC contributes 14% to global warming Answer : (c)

DDT is nondegradable pollutant and persist in environment in active form for 22-25 years. Ingestion of excess fluoride, most commonly in drinking-water, can cause fluorosis which affects the teeth and bones Excess of arsenic in drinking water causes black foot disease Itai-itai disease is caused by cadmium poisoning. Methyl mercury in water causes minamata disease. Answer : (a)

Photochemical smog is a brownish-gray haze caused by the action of solar ultraviolet radiation on atmosphere polluted with hydrocarbons and oxides of nitrogen. It contains anthropogenic air pollutants, mainly ozone, nitric acid, and organic compounds, which are trapped near the ground by temperature inversion. Some sulphates and nitrates can also be formed in photochemical smog due to oxidation of sulphur containing components (SO2, H2S) and NOx (N2O5, NO2) but it does not contain carbon di-oxide (CO2). Answer : (d)

CO has 200 times more afinity to haemoglobin than oxygen. When CO combines with haemoglobin it forms stable complex called carboxyhaemoglobin which reduces oxygen carrying capacity of haemoglobin and is deadly and toxic than other above pollutant. Answer : (b)

The purpose of melanin is to absorb and protect the skin from the sun's harmful UV rays Answer : (d)

Answer : (d)

The presence of E. coli in water is a strong indication of recent sewage or animal waste contamination. Answer : (c)

Acid rain is caused by a chemical reaction that begins when compounds like sulphur dioxide and nitrogen oxides are released into the air. These substances can rise very high into the atmosphere, where they mix and react with water, oxygen, and other chemicals to form more acidic pollutants, known as acid rain. Answer : (b)

Carbon dioxide, methane, CFCs and nitrous oxide are greenhouse gases. hydrogen is not greenhouse gas. Answer : (d)

Answer : (c)

Carbon monoxide combines with haemoglobin to form stable complex called carboxyhaemoglobin which reduces the oxygen carrying capacity of hamoglobin and causes major respiratory problems. Answer : (a)

Photochemical smog is a brownish-gray haze caused by the action of solar ultraviolet radiation on atmosphere polluted with hydrocarbons and oxides of nitrogen. It contains anthropogenic air pollutants, mainly ozone, nitric acid, and organic compounds, which are trapped near the ground by temperature inversion. Answer : (b)

Pesticides persists in environment for long time and has adverse effect on soil and water. Some of the pesticides also biomagnify affecting biosphere as well. Answer : (b)

CFCs were used in aresol and were used as coolants in refrigerator and air conditioners. The leading source of anthropogenic methane emissions is animal agriculture, followed by fugitive emissions from gas, oil, coal and other industry, solid waste, wastewater and rice production Volatile Organic Compounds (VOCs) react with nitrogen oxides in the presence of sunlight to form ground level ozone. Ozone is secondary pollutant since it is formed from primary pollutant from car exhaust. Denitrification is the microbial process of reducing nitrate and nitrite to gaseous forms of nitrogen, principally nitrous oxide (N2O) and nitrogen (N2). Combustion of fossil fuels yields carbon dioxide, water and energy Answer : (a)

Carbon dioxide (CO2) is greenhouse gas and contributes to 60% to global warming. Answer : (a)

Dichlorodiphenyltrichloroethane, commonly known as DDT, is a colorless, tasteless, and almost odorless crystalline chemical compound, an organochlorine. DDT persist in environment and remains in its active form for 22-25 yeras and hence can be considered as non-biogedrable pollutant. Answer : (a)

Eutrophication, distrophication or hypertrophication, is when a body of water becomes overly enriched with minerals and nutrients which induce excessive growth of algae. This process may result in oxygen depletion of the water body. Answer : (b)

A greenhouse gas is a gas that absorbs and emits radiant energy within the thermal infrared range. Greenhouse gases cause the greenhouse effect on planets. The primary greenhouse gases in Earth's atmosphere are water vapor, carbon dioxide, methane, nitrous oxide, and ozone. Answer : (b)

BOD is a measure of the amount of oxygen required to remove waste organic matter from water in the process of decomposition by aerobic bacteria (those bacteria that live only in an environment containing oxygen). BOD is used, often in wastewater-treatment plants, as an index of the degree of organic pollution in water. Since sewage has organic matter, BOD will be more than that of water. Answer : (a)

They overstimulate the growth of algae, causing unsightly scum and unpleasant odours, and robbing the water of dissolved oxygen vital to other aquatic life. At the same time, other pollutants flowing into a lake may poison whole populations of fish, whose decomposing remains further deplete the water’s dissolved oxygen content. Answer : (c)

Bhopal gas tragedy occurred (23 Dec. 1984) when MIC (Methyl Isocyanate) reacted with water in a tank, an exothermic chemical reaction started and produced a lot of heat. As a result, the safety valve of tank burst because of increase in pressure and gave rise to a heavy gas which rapidly killed the people around. Answer : (d)

If drinking water contains unsafe levels of contaminants, it can cause health effects, such as gastrointestinal illnesses, nervous system or reproductive effects, and chronic diseases such as cancer. Answer : (b)

Photochemical smog is a brownish-gray haze caused by the action of solar ultraviolet radiation on atmosphere polluted with hydrocarbons and oxides of nitrogen. It contains anthropogenic air pollutants, mainly ozone, nitric acid, and organic compounds, which are trapped near the ground by temperature inversion Answer : (a)

Methyl isocyanate is an intermediate chemical in the production of carbamate pesticides (such as carbaryl, carbofuran, methomyl, and aldicarb). Answer : (a)

Foul smell in the water of tanks , ponds etc is due to Anaerobiosis. The lack of fresh air and Oxygen inside water tanks and ponds results in anaerobic processes there. The products (alcohols/lactic acids/gases) of anaerobiotic fermentation cause the foul smell. Answer : (a)

Carbon dioxide is a greenhouse gas. It absorbs the long wavelength infrared radiations. The chemical bond between carbon and oxygen absorb infrared light very well and traps the heat from escaping, so they are considered to be opaque to the infra-red rays as these cannot pass across the carbon dioxide. Carbon dioxide molecules vibrate on receiving energy from the photon and allows molecules to capture the infrared photons (radiation). Answer : (a)

Answer : (c)