Answer : (c)

BOD or Biochemical Oxygen Demand is the amount of oxygen required to decompose organic matter present in one litre of polluted water. More the value of BOD,more will be the amount of organic matter in the water. Hence, a high BOD value means heavily polluted water. Water with BOD value of 1-2 ppm is considered clean. In freshwater, BOD value should not exceed 5 ppm as the dissolved oxygen will be used up in the decomposition of organic matter and will not be available for the survival of aquatic organisms which will lead to their death. Answer : (a)

Acid rain is caused by a chemical reaction that begins when compounds like sulfur 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 : (a)

Minamata disease (M. d.) is methylmercury (MeHg) poisoning that occurred in humans who ingested fish and shellfish contaminated by MeHg discharged in waste water from a chemical plant Answer : (a)

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 . BOD is used, often in wastewater-treatment plants, as an index of the degree of organic pollution in water. High BOD means more polluted. Answer : (a)

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 . BOD is used, often in wastewater-treatment plants, as an index of the degree of organic pollution in water. High BOD if water is contaminated with sewage. Answer : (b)

Carbon monoxide has approximately 200 times greater affinity for haemoglobin than oxygen Answer : (d)

Some examples of Ecosan toilets can be seen in Gujarat, Karnataka, Maharashtra, Andhra Pradesh, Kerala, Orissa, Bihar and Ladakh, Sri Lanka Answer : (b)

Environmental pollution affects biotic components and abiotic components like lithosphere, atmosphere and hydrosphere. Answer : (d)

Normal, clean rain has a pH value of between 5.0 and 5.5, which is slightly acidic. However, when rain combines with sulfur dioxide or nitrogen oxides—produced from power plants and automobiles—the rain becomes much more acidic. Typical acid rain has a pH value of 4.0. Answer : (d)

Fly ash is produced by coal-fired electric and steam generating plants. Except fly ash, all other options are products of exhaust of motor vehicles Answer : (b)

According to Central Pollution Control Board (CPCB), particulate size 2.5 micrometers or less in diameter (PM 2.5) are responsible for causing the greatest harm to human health. Answer : (c)

Clouds and gases reflect about one-fourth of the incoming solar radiation, and absorb some of it but almost half of incoming solar radiation falls on Earth’s surface heating it, while a small proportion is reflected back. Greenhouse gases absorb long wave (infrared) radiation from earth and emit it again towards the earth. Answer : (d)

statistical report that says road dust causes 38% of air pollution, 20% due to smoke that comes out of the vehicle. 12% of air gets polluted due to domestic fuel burning and the industrial point sources have the remaining 11% of share in polluting the air. Answer : (d)

Assertion is correct is true as exposure to any sound above 85 decibels has the potential to cause hearing damage, especially with frequent or prolonged exposure. Reason is false because the sounds associated with jet planes measure between 120 and 140 decibels not 160 decibels. Answer : (c)

Unlike drugs or chemicals, noise pollution leaves no residue in the body. Numerous studies have linked noise pollution to increased anxiety, depression, high blood pressure, heart disease, and stroke Plants does not abosrb noise of low frequnecy but can reduce. A properly designed buffer of trees and shrubs can reduce noise by about five to ten decibels. Loss of hearing or difficulty in hearing is common symptoms of prolonged exposure to noise pollution. Answer : (c)

BOD refers to biochemical as well as biological oxygen demand but bioCHEMICAL is the most appropriate one Explanation on term BOD provided by Zubaida Answer : (d)

The Montreal Protocol is an international treaty designed to protect the ozone layer by phasing out the production of numerous substances that are responsible for ozone depletion. It was agreed on 16th September 1987, and entered into force on 1st January 1989. Answer : (c)

Photochemical oxidants are the secondary pollutants that are formed when the primary pollutants like hydrocarbons, oxides of sulphur, oxides of nitrogen react with sunlight. The major products of this reaction include tropospheric ozone, peroxyacetyl nitrate and aldehydes. They also contribute to the formation of the photochemical smog. The reaction of solar radiation with primary airborne pollutants like nitrogen oxides and volatile organic compounds forms photochemical smog. Ultraviolet light can split nitrogen dioxide into nitric oxide Answer : (b)

DDT, is a colorless, tasteless, and almost odorless crystalline chemical compound, an organochlorine compound which is not metabolised and excreted. It remains in fat storage tissue of organism and passes from one trophic level to another i.e it shows biomagnification. Statement X is correct. Ozone depletion is caused to chloroflurocarbons (CFCs) also known as freons not due to UV radiations. Statement Y is not correct. Answer : (c)

raditional rice cultivation is the second biggest agricultural source of GHG after livestock. Traditional rice production globally accounts for about 1.5% of greenhouse gas emissions, equivalent to all aviation emissions. Its source is methane, created by organic matter decomposing underwater in flooded paddies Answer : (b)

Over the last 150 years, carbon dioxide (CO2) concentrations have risen from 280 to nearly 380 parts per million (ppm). Answer : (c)

Minamata disease is a methylmercury poisoning with neurological symptoms and caused by the daily consump- tion of large quantities of fish and shellfish that were heavily contaminated with the toxic chemical generated in chemical factories and then discharged into the sea. Itai-itai disease was caused by cadmium poisoning Answer : (b)

Ozone gas is continuously formed by the action of UV rays on molecular oxygen, and also degraded into molecular oxygen in the stratosphere. Answer : (a)

Although ozone depletion is occurring widely in the stratosphere, the depletion is particularly marked over the Antarctic region. This has resulted in formation of a large area of thinned ozone layer, commonly called as the ozone hole Answer : (b)

electrostatic precipitator has electrode wires that are maintained at several thousand volts, which produce a corona that releases electrons. These electrons attach to dust particles giving them a net negative charge. The collecting plates are grounded and attract the charged dust particles. The velocity of air between the plates must be low enough to allow the dust to fall. Using scrubbers can clean air to reduce air pollution. Air pollution can be reduced by reducing air pollutant not by reusing waste. Answer : (b)

Biochemical oxygen demand (BOD) is the amount of dissolved oxygen needed (i.e. demanded) by aerobic biological organisms to break down organic material present in a given water sample at certain temperature over a specific time period. It is connected to microbes and organic matter. Answer : (c)

The general population may be exposed through consumption of residues of pesticides in food and, possibly, drinking water. The residue of pesticides are found because they are persist in environment and their degradation takes a long time. Answer : (a)

The Bhopal disaster, also referred to as the Bhopal gas tragedy, was a gas leak incident on the night of 2–3 December 1984 at the Union Carbide India Limited (UCIL) pesticide plant in Bhopal, Madhya Pradesh, India. It is considered among the world's worst industrial disasters. Over 500,000 people were exposed to methyl isocyanate (MIC) gas Answer : (a)

Carbon dioxide contributes 60% to global warming Methane contributes 20% to global warming CFC contibutes 14% to global warming N2O contibutes 6% to global warming. Answer : (d)