Shankar IAS Test: Environmental Issues - UPSC MCQ

Water pollution occurs when harmful substances contaminate a stream, river, lake, ocean or other body of water, degrading water quality. 

• Common ways of water pollution:
  • Waste disposal directly into water streams,
  • Urban and agricultural runoff,
  • From air via acid rain,
  • Discharge of animal waste etc.
• Water pollution can cause a series of diseases like:
  •  Typhoid, Amoebiasis, Ascariasis, Diarrhea, Encephalitis etc.
• Diarrhoea is caused mostly due to consumption of polluted water and is characterized by loose, watery stools or a frequent need to have a bowel movement.
  • Common bacteria that cause diarrhoea include Escherichia coli (E. coli), Salmonella, and Shigella.
  • Parasites that cause diarrhoea include Cryptosporidium enteritis, Entamoeba histolytica etc.
  • Hence, Option 3 is correct.

Noise pollution is measured in Decibel.

• The decibel (dB) is a logarithmic unit used to measure sound level.
• It is also widely used in electronics, signals and communication.
• In ordinary usage, specification of the intensity of a sound implies a comparison of the intensity of the sound with that of a sound just perceptible to the human ear.
• In simple terms, the dB is the ratio between two power levels expressed in logarithmic terms with relation to some reference level.
• For example, if given two known power levels, P2 and P1, the relative value of P2 with respect to P1 in dB is given by:
  • dB = 10 log ₁₀ (P₂/P₁)
• Noise levels below 35–40 dB are usually necessary for a good night’s sleep.
• A busy office may be about 60 dB while the noise level on a footpath beside a busy road might be approximately 75 dB.
• A departing jumbo jet may result in 120 dB being recorded along the runway.
• Ohm is the SI unit of electrical resistance, transmitting a current of one ampere when subjected to a potential difference of one volt.
• Joule, unit of work or energy in the International System of Units (SI); it is equal to the work done by a force of one newton acting through one metre.
• Ampere is a unit of electric current equal to a flow of one coulomb per second.

The correct answer is option 1 i.e. Oxygen

• A Greenhouse gas (GHG) is a gas that absorbs and emits radiant energy within the thermal infrared range.
• Carbon dioxide, methane, and water vapour are the most important greenhouse gases and oxygen is not a GHG. Hence option 1 is correct.
• Some other gases such as surface-level ozone, nitrous oxides, and fluorinated gases also trap infrared radiation.
• Kyoto Protocol
  • Kyoto Protocol is an international agreement that aimed to reduce Carbon dioxide emissions and the presence of Greenhouse Gases (GHG) in the atmosphere.
  • It was adopted in Kyoto, Japan on 11^th December 1997. and became international law on 16 February 2005.

Concept:

Ozone Layer: 

• Ozone (O3) is a molecule formed by three atoms of oxygen. Ozone is a deadly poison.
• Ozone is found in the stratosphere layer of the atmosphere.
• However, at the higher levels of the atmosphere, ozone performs an essential function. It shields the surface of the earth from ultraviolet (UV) radiation from the Sun.
• This radiation is highly damaging to organisms, for example, it is known to cause skin cancer in human beings or can split the DNA.
• It is a pale blue gas with a distinctively pungent smell.
• Ozone is an excellent oxidizing agent as it breaks down into oxygen gas and nascent oxygen. { O3 → O2 + [O] }
• It is an allotrope of oxygen that is much less stable than the diatomic allotrope O2, breaking down in the lower atmosphere to O2 or di-oxygen

Its depletion:

• The amount of ozone in the atmosphere began to drop sharply in the 1980s.
• This decrease has been linked to synthetic chemicals like chlorofluorocarbons (CFCs) which are used as refrigerants and in fire extinguishers.
• The government bans those products which contain CFCs.

• Ozone is thermodynamically unstable and decomposes to molecular oxygen. Thus, a dynamic equilibrium exists between the production and decomposition of ozone molecules

Explanation:​.

• In recent years, there have been reports of the depletion of this protective ozone layer because of the presence of certain chemicals in the stratosphere.
• The main reason for ozone layer depletion is believed to be the release of chlorofluorocarbon compounds (CFCs), also known as Freons.
• These compounds are non-reactive, non-flammable, non-toxic organic molecules and therefore used in refrigerators, air conditioners, in the production of plastic foam and by the electronic industry for cleaning computer parts etc.
• Once CFCs are released in the atmosphere, they mix with the normal atmospheric gases and eventually reach the stratosphere. Hence option 3 is correct.
• In the 1980s, for the first time, atmospheric scientists working in Antarctica reported about the depletion of the ozone layer commonly known as the ozone hole over the South Pole.

Ozone Hole

• It refers to a region in the stratosphere where the concentration of ozone becomes extremely low in certain months.
• Ozone (chemically, a molecule of three oxygen atoms) is found mainly in the upper atmosphere, an area called the stratosphere, between 10 and 50 km from the earth’s surface.
• Ozone absorbs the harmful UltraViolet (UV) radiations from the sun eliminating a big threat to life forms on earth.
• UV rays can cause skin cancer and other diseases and deformities in plants and animals.
• The ozone holes most commonly refer to the depletion over Antarctica, forming each year in September, October, and November, due to a set of special meteorological and chemical conditions that arise at the South Pole, and can reach sizes of around 20 to 25 million sq km.
• Hence, we can say that Ozone holes are more pronounced at the​ poles. Hence, Option 4 is correct.
• Chlorofluorocarbons, Hydrochlorofluorocarbons, Carbon tetrachloride, Methyl chloroform, Methyl chloroform, Halons, Methyl bromide.
• Another pollutant we have added to the upper atmosphere that affects ozone is nitrogen oxides from airplane exhaust. So, above and beyond, the seasonal variations in ozone are more pronounced at the poles.

• Oxygen demanding wastes are organic compounds, such as sewage and agricultural runoff, which decompose through microbial action in water.
• The process of microbial decomposition requires oxygen, and as a result, these wastes decrease the oxygen level in the water.
• If the oxygen level drops below a certain level, aquatic organisms can die due to suffocation, which leads to a condition called hypoxia.
• This can also cause a decrease in biodiversity and ecological productivity in water bodies.
• Therefore, it is important to reduce the discharge of oxygen-demanding wastes into water bodies to maintain the ecological balance.

Ecological balance

•  A number of the world's ecosystems have undergone significant degradation leading to a negative impact on biodiversity and livelihood.
• One such ecosystem that has depleted over the years is the mined habitats.
• Since the mineral-rich areas are also rich in forest resources. However continuous mining activities tend to change the ecological equilibrium.
• Restoration of the ecological equilibrium of the mined areas can be achieved by understanding the ecology, plant succession, and soil types of the place and revegetation of the spoils. Hence, option 1 is correct.
• Ecological equilibrium refers to a state of equilibrium between all living and non-living organisms in the environment.
• Mining sites are constantly subjected to mining activities, and as a result, the natural balance of the area is disrupted.
• The development of a plant cover in such an area will aid in the recovery or  of the soil.
• The land is not intended for farming.
• There is no grazing in this location. 
• It is possible to avoid soil erosion, but this does not guarantee that the soil will be totally restored. 
• For the time being, vegetation cover and regular revegetation work will rebalance the ecology of the mined region. 

Carbon dioxide (CO₂) makes up the vast majority of greenhouse gas emissions from the sector, but smaller amounts of methane (CH₄) and nitrous oxide (N₂O) are also emitted. These gases are released during the combustion of fossil fuels, such as coal, oil, and natural gas, to produce electricity.

• A glacier is not a water pollutant but it is a source of fresh water.
• The main water pollutants include bacteria, viruses, parasites, fertilizers, pesticides, pharmaceutical products, nitrates, phosphates, plastics, faecal waste, and even radioactive substances.
• These substances do not always change the colour of the water, meaning that they are often invisible pollutants.
• While some metals are essential for human health at trace concentrations due to their role as coenzymes (eg, Fe and Cu), others are toxic at any concentration level (eg, Pb and Cd) Chromium (Cr VI), cadmium (Cd), lead (Pb), and arsenic (As) have been recognized as water, pollutants.
• Metals can cause severe toxicity in humans, depending on the concentration, the exposure pathway, and the duration of exposure.

The Central Pollution Control Board (CPCB) has proposed a new set of fines between Rs 1,000 and Rs 1 lakh for those who violate norms restricting noise pollution under the Noise Pollution (Regulation and Control) Rules, 2000.

Unremitting loud construction activity, loudspeakers at functions and processions, honking at odd hours — all contributors to noise pollution and violations under the law — can, thus, burn holes in the pockets of those who violate the norms.

The permissible noise level in India:

The CPCB has laid down the permissible noise levels in India for different areas. Noise pollution rules have defined the acceptable level of noise in different zones for both daytime and night time.

1. In industrial areas, the permissible limit is 75 dB for daytime and 70 dB at night.
2. In commercial areas, it is 65 dB and 55 dB, while in residential areas it is 55 dB and 45 dB during daytime and night respectively.

Therefore, day time noise standard prescribed for residential areas in India is 55 dB.

Smog is Fog and smoke.

• Smog is a type of intense air pollution that reduces visibility.
• The term "Smog" was coined in the early 20th century and is derived from the words smoke and fog.
• Smog is a mixture of smoke (composed of minute particles of carbon, ash, and oil, etc. from coal combustion) and fog in suspended droplet form.
• It is the most common kind of air pollution that occurs in cities throughout the world.

Important Points

• There are 2 types of smog: Classical and Photochemical smog.
  • Classical smog (London smog) occurs in a cool and humid climate. It is reducing in nature.
  • Photochemical smog (Los Angeles smog) occurs in a sunny and dry climate. It is oxidizing in nature.
• Smog falls under the category of particulate pollutants since it is composed of very minute particles.
• Long-term exposure to smog can be harmful to human health.

• Seawater is impure water, so adding salt increases the boiling point of water this is because salt is a non-volatile solute which is responsible for boiling point elevation.
• The boiling point of a liquid is the temperature at which the vapour pressure of the liquid and the surrounding pressure is equal.
• The original boiling point of water is 100°C. After the addition of 58 grams of salt, the boiling point increases by one half of the degree Celsius

Non-point sources of water pollution are those that are diffuse and do not originate from a specific location or point source.

• Non-point sources of water pollution are typically caused by activities such as agricultural runoff, stormwater runoff, and atmospheric deposition.
• Episodic sources refer to those that occur irregularly or intermittently, such as spills or accidents.
• These can also contribute to non-point source pollution.
• Non-point sources of pollution can be difficult to monitor and control because they come from a variety of sources and are spread out over a large area, making it challenging to identify and address the specific sources of contamination.

Therefore, the correct options are B, C, and E.

Denial of the forest has the sense of full forest cleansing or land deforestation, and it is also known as forest destruction.

• Forest degradation has resulted in land being utilised for urbanisation, mining, and agricultural farming operations. 
• Deforestation has a number of environmental consequences, the most significant of which is the loss of wildlife habitat. 
• Cutting trees and clearing land for human use increases greenhouse gas emissions and leads to the extinction of many species of flora and wildlife, disrupting and unbalancing the ecosystem. 

Thus it is clear that forest destruction is the meaning of denial of the forest.

The correct answer is option 2, the eggs did not hatch.

DDT (dichlorodiphenyltrichloroethane) is a pesticide that was widely used in the mid-twentieth century. Although it was effective in controlling pests, it had significant unintended consequences for wildlife, particularly birds.

DDT is a persistent organic pollutant that accumulates in the food chain, which means that as it moves up the food chain, its concentration increases. Birds that feed on insects and other small organisms that have been exposed to DDT may accumulate high levels of the pesticide in their bodies.

When birds with high levels of DDT in their bodies lay eggs, the pesticide interferes with the normal development of the eggs. Specifically, it can cause the eggshells to become thin and brittle, making them more susceptible to breaking during incubation. As a result, the eggs may not hatch, leading to a decline in the bird population.

Therefore, option 2 is the correct answer: the decline in bird populations in areas under the influence of DDT is due to the fact that the eggs do not hatch.