Pollution Questions in English

(C) $SO_2$ causes bleaching of leaf pigment (chlorophyll),leading to chlorosis and necrosis of vegetation. It destroys membrane activity and converts chlorophyll $a$ into phaeophytin $a$.

(B) Sulfur dioxide $(SO_2)$ is a major air pollutant that causes significant damage to plant cells.
When $SO_2$ enters the plant cell,it reacts with water to form sulfurous acid,which increases the acidity of the cell environment.
This pollutant primarily affects the membrane system of the cell,leading to the degradation of chlorophyll and the disruption of the semi-permeable nature of the cell membranes,which eventually causes cell death.

(C) The correct answer is $Pb$ (Lead).
Lead is released into the atmosphere through the combustion of petrol,as tetraethyl lead is used as an antiknock agent in fuel.
This pollutant is highly toxic and leads to plumbism or lead poisoning.
Lead poisoning significantly affects the nervous system,liver,and kidneys in adults,and it is known to cause severe brain damage and cognitive impairment in children.

(C) The photochemical reaction occurs when sunlight (specifically $UV$ radiation) interacts with primary pollutants like hydrocarbons and nitrogen oxides $(NO_x)$ emitted from automobile exhausts.
These reactions lead to the formation of secondary pollutants,most notably ozone $(O_3)$ and Peroxyacetyl nitrate $(PAN)$,along with aldehydes and other organic substances.
This process is the primary cause of photochemical smog.

(B) Eutrophication is the natural aging of a lake by nutrient enrichment of its water.
In a young lake,the water is cold and clear,supporting little life.
With time,streams draining into the lake introduce nutrients such as nitrogen and phosphorus,which encourage the growth of aquatic organisms.
Human activities,such as the discharge of sewage and detergents,significantly accelerate this aging process,a phenomenon known as cultural or accelerated eutrophication.
These pollutants lead to excessive growth of algae,which depletes dissolved oxygen and harms aquatic life.

(D) Brewery and sugar factory wastes are rich in organic matter. When these wastes are discharged into water bodies,the microorganisms present in the water start decomposing this organic matter. This process requires a large amount of dissolved oxygen. Consequently,the $BOD$ (Biochemical Oxygen Demand) and $COD$ (Chemical Oxygen Demand) of the water body increase significantly,leading to the depletion of oxygen for aquatic life.

(D) $EIA$ stands for $\text{Environmental Impact Assessment}$.
It is a systematic process used to evaluate the environmental consequences of a proposed project or development before it is implemented.
This assessment helps in identifying potential environmental impacts and suggests measures to mitigate them.

(B) Non-ionising radiation refers to electromagnetic radiation that does not have enough energy to remove electrons from atoms or molecules.
$UV$ (Ultraviolet) rays are a form of non-ionising radiation.
Although they are non-ionising,$UV$ rays have sufficient energy to cause chemical changes in biological molecules.
Specifically,$UV$ rays,particularly $UV-B$,are absorbed by $DNA$ and cause the formation of pyrimidine dimers (such as thymine dimers),which lead to mutations and damage to the genetic material.

(D) weightless pollutant is a form of pollution that does not consist of physical matter with mass.
Heat (thermal pollution),sound (noise pollution),and radioactive emissions (in the form of energy waves) are considered weightless pollutants because they do not add physical mass to the environment,unlike particulate matter or chemical pollutants.

(C) $3, 4-$ benzopyrene is a polycyclic aromatic hydrocarbon found in cigarette smoke and automobile exhaust.
It is a well-known carcinogen that causes lung cancer by damaging $DNA$ in the cells of the respiratory tract.

(B) The most important long-lived radioactive substance released in a nuclear explosion is $Sr^{90}$.
It accumulates in the bone marrow and causes cancer,specifically leukaemia (blood cancer).

(C) Sound is measured in decibels $(dB)$.
According to environmental standards, any sound intensity exceeding $80 \text{ dB}$ is considered noise pollution as it can cause physical and psychological distress to humans.
Among the given options, $100 \text{ dB}$ is the only value that significantly exceeds the $80 \text{ dB}$ threshold, thus acting as a pollutant.

(B) The Bhopal Gas Tragedy, which occurred in $1984$ in Bhopal, Madhya Pradesh, is considered the world's worst industrial disaster.
It involved the accidental release of approximately $40$ tonnes of methyl isocyanate $(MIC)$ gas from the Union Carbide India Limited $(UCIL)$ pesticide plant.
This disaster resulted in thousands of immediate deaths and long-term health complications for the local population, making it the most significant air pollution-related disaster in recent history.

(D) Environmental pollution is caused by several anthropogenic activities.
$1$. Population explosion leads to increased consumption of resources and higher waste generation.
$2$. Urbanization results in the destruction of natural habitats,increased traffic,and higher waste accumulation.
$3$. Industrialization releases harmful chemicals,heavy metals,and greenhouse gases into the atmosphere,water bodies,and soil.
Therefore,all the mentioned factors contribute significantly to environmental pollution.

(B) The correct answer is $B$.
$CO_2$ is a naturally occurring gas in the atmosphere and is essential for the process of photosynthesis in plants.
It is not considered a pollutant in normal concentrations as it is non-toxic to humans and animals.
In contrast,$CO$,$SO_2$,and hydrocarbons are harmful substances that degrade air quality and are classified as atmospheric pollutants.

(B) Smog is a combination of smoke and fog. It is a common pollutant in urban areas,especially during winter months when the temperature is low. Low temperatures facilitate the condensation of water vapor around particulate matter,leading to the formation of thick fog,which traps pollutants like smoke and $SO_2$ near the ground,resulting in smog.

(C) Photochemical smog is formed by the action of sunlight on nitrogen oxides $(NO_x)$ and volatile organic compounds $(VOCs)$ present in the atmosphere.
This reaction leads to the formation of secondary pollutants,including ozone $(O_3)$,formaldehyde,and peroxyacetyl nitrate $(PAN)$.
Therefore,$O_3$ is a primary photochemical reaction product.

(A) The index of pollution in a water body is primarily determined by the $BOD$ (Biochemical Oxygen Demand) and the presence of specific bioindicator organisms.
$BOD$ measures the amount of dissolved oxygen required by aerobic microorganisms to decompose organic matter in water; higher $BOD$ indicates higher pollution.
$Daphnia$ (water fleas) are sensitive to water quality and are widely used as bioindicators to assess the level of pollution in aquatic ecosystems.
Therefore,$BOD$ and $Daphnia$ serve as reliable indicators of pollution.

(D) The correct answer is $D$.
$1$. Agro-industry contributes to pollution through the runoff of chemical fertilizers,pesticides,and organic waste into water bodies and soil.
$2$. Mining activities lead to the release of heavy metals,acidic drainage,and soil erosion,significantly contaminating both water and soil.
$3$. Thermal power stations release fly ash,thermal discharge,and various pollutants that contaminate water sources and surrounding soil.
Therefore,all the mentioned options are significant sources of water and soil pollution.

(A) $DDT$ (Dichlorodiphenyltrichloroethane) is a non-biodegradable pollutant.
These substances are persistent in the environment because they cannot be broken down naturally or by the metabolic activities of microorganisms.
Due to their chemical stability,they accumulate in the food chain and are not recycled back into the atmosphere or soil in a harmless form.

(A) Plants are significantly more sensitive to $SO_2$ than animals and humans.
When plants are exposed to high concentrations of $SO_2$,it leads to the destruction of the chlorophyll pigment.
This occurs primarily due to the conversion of chlorophyll $a$ into phaeophytin $a$,which disrupts the photosynthetic process.

(A) The index of pollution in a water body is determined by the presence or absence of bioindicator species.
$Daphnia$ (water fleas) are highly sensitive to changes in water quality,particularly to pollutants like heavy metals and pesticides.
When a lake becomes polluted,these sensitive organisms disappear,making them excellent biological indicators of water pollution.
Therefore,$Daphnia$ serves as an index of pollution.

(A) Lichens are highly sensitive to atmospheric sulfur dioxide $(SO_2)$ pollution.
They lack a waxy cuticle and absorb nutrients and water directly from the atmosphere,making them excellent bioindicators.
Specifically,species like $Usnea$ and $Parmelia$ are widely recognized as indicators of air quality,as they disappear from areas with high levels of $SO_2$.

(D) $BOD$ stands for Biochemical Oxygen Demand. It refers to the amount of dissolved oxygen that is required by aerobic microorganisms in a body of water to break down the organic material present in a given water sample at a specific temperature over a specific time period. Higher $BOD$ values indicate higher levels of water pollution.

(A) Thermal pollution occurs when the temperature of water bodies is artificially increased.
This is primarily caused by the discharge of heated wastewater from power plants (such as thermal or nuclear power plants) that use water for cooling purposes.
This rise in temperature decreases the concentration of dissolved oxygen and has an adverse effect on aquatic organisms.

(D) The biological treatment of water pollution,particularly in sewage treatment plants,primarily involves the use of microorganisms such as bacteria and fungi.
These microorganisms break down organic matter present in the wastewater through aerobic and anaerobic processes.
Since the options provided do not explicitly list bacteria (the primary agents),and phytoplankton or lichens are not used for the treatment of sewage,the most appropriate choice among the given options is $D$ (None of the above),as the primary biological agents are bacteria.

(A) Pollution,particularly air pollution,significantly impacts the respiratory system.
Bronchitis is an inflammation of the lining of the bronchial tubes,which carry air to and from the lungs.
Exposure to pollutants such as particulate matter $(PM_{2.5})$,sulfur dioxide $(SO_2)$,and nitrogen oxides $(NO_x)$ can cause or severely aggravate chronic bronchitis.
Rheumatism is related to joints,Scurvy is a vitamin $C$ deficiency,and Haemophilia is a genetic disorder; none of these are caused by environmental pollution.

(C) The excessive discharge of fertilizers (containing nitrates and phosphates) into water bodies leads to a process known as $Eutrophication$.
These nutrients stimulate the rapid growth of algae,known as an algal bloom.
This excessive algal growth depletes the dissolved oxygen in the water,which eventually leads to the death of aquatic organisms and the degradation of the water ecosystem.

(C) Chemicals released into the atmosphere with force in the form of mist or vapours are called aerosols. Jet aeroplanes release aerosols which contain $CFCs$ (chlorofluorocarbons) into the upper atmosphere,which can deplete the ozone layer.

(A) The primary precursors of acid rain are $SO_2$ (sulphur dioxide) and $NO_2$ (nitrogen dioxide) present in the atmosphere.
These gases react with atmospheric water $(H_2O)$ to form $H_2SO_4$ (sulphuric acid) and $HNO_3$ (nitric acid).
These acids precipitate along with rain,resulting in what is known as acid rain.

(B) Domestic waste refers to the garbage generated from households. This waste consists mainly of organic materials such as vegetable peels,food scraps,paper,and garden waste. Since these materials can be broken down by microorganisms into simpler substances,they are classified as biodegradable pollutants.

(A) The foul smell in stagnant water bodies like tanks and ponds is primarily caused by the decomposition of organic matter by anaerobic microorganisms. This process is known as $Anaerobiosis$. Under anaerobic conditions,bacteria break down organic waste,releasing gases such as hydrogen sulfide $(H_2S)$,methane $(CH_4)$,and ammonia $(NH_3)$,which produce a characteristic unpleasant odor.

(B) Eutrophication is the process where water bodies become enriched with nutrients,typically $N$ and $P$,leading to excessive growth of algae (algal bloom).
These algal blooms cover the surface of the water,preventing sunlight from reaching submerged plants.
As the algae die,decomposers like bacteria consume the organic matter,using up a large amount of the $O_2$ dissolved in the water for respiration.
This leads to a significant decrease in the levels of dissolved oxygen,which negatively impacts aquatic life such as fish and other organisms.

(B) The Taj Mahal is primarily threatened by $SO_2$ (sulphur dioxide) emissions from nearby industries and refineries. $SO_2$ reacts with atmospheric water vapour to form sulphuric acid $(H_2SO_4)$,which leads to acid rain. This acid rain reacts with the calcium carbonate $(CaCO_3)$ present in the white marble of the Taj Mahal,causing it to corrode and turn yellow,a process often referred to as 'marble cancer'.

(C) The correct answer is $C$.
Excessive concentration of $Fluorine$ in drinking water leads to a condition known as fluorosis.
The primary symptoms of dental fluorosis include the mottling of teeth,which appears as yellowish or brownish streaks or spots on the enamel.
In severe cases,it can also lead to skeletal fluorosis,causing abnormal bone structure and increased susceptibility to fractures.
This is a classic example of an endemic disease caused by environmental chemical contamination.

(C) Biodegradable pollutants are substances that can be broken down by microorganisms into simpler,harmless substances.
Sewage contains organic matter that is easily decomposed by bacteria and other microorganisms in the environment.
Plastic and asbestos are non-biodegradable pollutants as they persist in the environment for a very long time and cannot be broken down by biological processes.

(B) heat island is an urban area that is significantly warmer than its surrounding rural areas due to human activities.
Air pollution contributes to this phenomenon as greenhouse gases and particulate matter trap heat within the urban atmosphere.
Additionally,the replacement of natural vegetation and open land with concrete,asphalt,and buildings (which absorb and re-radiate solar heat) leads to increased surface temperatures.
Urbanization and the release of heat-trapping gases are primary drivers of this effect.
Therefore,the correct answer is option $B$.

(B) The correct answer is $B$.
$1$. The Bhopal gas tragedy occurred on $3^{rd}$ December $1984$ due to the leakage of Methyl Isocyanate $(MIC)$ gas,which caused severe air pollution and the death of approximately $2500$ people.
$2$. The Chernobyl nuclear disaster occurred on April $26, 1986$,due to an explosion at the Chernobyl nuclear power station in Ukraine,which released a massive amount of radioactive material into the atmosphere.

(A) Acid rain is primarily caused by the emission of sulphur dioxide $(SO_2)$ and nitrogen oxides $(NO_x)$.
When $SO_2$ is released into the atmosphere,it reacts with atmospheric moisture $(H_2O)$ and oxygen to form sulphuric acid $(H_2SO_4)$.
This acid then falls to the Earth's surface as acid rain,which can damage ecosystems,buildings,and soil quality.

(B) Leaf curling is a characteristic symptom of damage caused by ozone $(O_3)$ exposure in plants.
Ozone is a secondary pollutant that acts as a strong oxidizing agent.
It enters the plant through the stomata and causes cellular damage,leading to symptoms such as chlorosis,necrosis,and leaf curling or rolling.

(B) Automobile exhaust contains various pollutants,among which lead is considered one of the most hazardous heavy metal pollutants.
Historically,lead was added to gasoline as an anti-knock agent,which was then released into the atmosphere through vehicle exhaust.
Lead exposure is particularly dangerous as it can cause severe neurological damage,especially in children,and affects various organ systems in the human body.

(A) Photochemical smog is formed due to the photochemical oxidation of hydrocarbons and nitrogen oxides in the presence of sunlight.
$NO_2$ absorbs $UV$ light and decomposes into nitric oxide $(NO)$ and atomic oxygen $(O)$.
Atomic oxygen $(O)$ reacts rapidly with molecular oxygen $(O_2)$ to form ozone $(O_3)$.
Therefore,ozone is a characteristic component of photochemical smog.

(C) $Carbon$ $monoxide$ $(CO)$ is a major air pollutant. It has a significantly higher affinity for haemoglobin than oxygen. When inhaled,it binds with haemoglobin to form carboxyhaemoglobin,which is much more stable than oxyhaemoglobin. This process reduces the oxygen-carrying capacity of the blood,leading to hypoxia and eventually asphyxiation.

(C) Noise pollution is defined as any unwanted or harmful sound that can cause damage to human health or the environment.
According to the World Health Organization $(WHO)$ and environmental standards,sound levels exceeding $80 \text{ dB}$ are considered to be harmful and contribute to noise pollution.
Exposure to sound levels above $80 \text{ dB}$ for prolonged periods can lead to hearing impairment,stress,and other physiological issues.
Therefore,noise pollution is generally recognized when noise levels exceed $80 \text{ dB}$.

(B) $PAN$ is a secondary pollutant.
Pollutants that are formed by the chemical interaction of primary pollutants with atmospheric gases and moisture, often catalyzed by sunlight, are called secondary pollutants.
Since $PAN$ is produced in the atmosphere through the reaction of nitrogen oxides and volatile organic compounds in the presence of sunlight, it is classified as a secondary pollutant.

(C) The correct answer is $(C)$.
Peroxyacetyl nitrate $(PAN)$ is a secondary pollutant formed by the photochemical reaction of nitrogen oxides and hydrocarbons.
It is known to inhibit the Hill reaction,which is the light-dependent reaction of photosynthesis.
Specifically,$PAN$ interferes with the photolysis of water,thereby disrupting the electron transport chain and reducing the efficiency of photosynthesis in plants.

(D) The Bhopal gas tragedy occurred on the night of $2-3$ December $1984$ at the Union Carbide India Limited $(UCIL)$ pesticide plant in Bhopal,Madhya Pradesh,India.
This disaster was caused by the accidental leakage of a highly toxic gas known as Methyl Isocyanate $(MIC)$,with the chemical formula $CH_3NCO$.
It is considered one of the world's worst industrial disasters,resulting in thousands of immediate deaths and long-term health complications for the local population.

(C) is the correct answer. Silicosis is an occupational respiratory disease caused by the inhalation of dust containing free silica or silicon dioxide. It is commonly observed in workers engaged in mining,pottery,ceramic industries,sandblasting,and construction industries.