Pollution Questions in English

(A) Nitrogen oxides $(NO_x)$ are primary pollutants emitted from automobiles and power plants.
These oxides react with volatile organic compounds $(VOCs)$ and sunlight to form photochemical smog.
Photochemical smog is a mixture of pollutants that are formed when nitrogen oxides and volatile organic compounds react to sunlight,creating a brown haze in the atmosphere.

(B) The Central Pollution Control Board $(CPCB)$ has established guidelines for the discharge of industrial and municipal wastewater into natural surface water bodies.
According to these standards,the $BOD$ (Biochemical Oxygen Demand) level of the wastewater must be less than $30 \ ppm$ before it is discharged into natural water bodies to prevent excessive pollution and eutrophication.

(D) Electrostatic precipitators $(ESP)$ are highly efficient devices used in industrial exhaust systems to remove particulate matter from the air.
In coal-fired power plants,they are specifically used to remove $SPM$ (Suspended Particulate Matter) from the exhaust gases before they are released into the atmosphere.
$ESP$ can remove over $99\%$ of the particulate matter present in the exhaust.
Therefore,the correct option is $D$.

(B) When domestic sewage is discharged into a river,it contains organic matter that serves as food for microorganisms like bacteria.
These microorganisms multiply rapidly by decomposing the organic matter.
This process requires a significant amount of oxygen,leading to a sharp decline in the dissolved oxygen $(DO)$ levels in the water.
This phenomenon is known as Biochemical Oxygen Demand $(BOD)$ increase,which can lead to the death of aquatic organisms like fish.

(A) In major Indian metropolitan cities like Delhi,the primary atmospheric pollutants are Suspended Particulate Matter $(SPM)$.
These particles are extremely small and can remain suspended in the air for long periods.
They are primarily generated from vehicular emissions,industrial activities,and construction dust.
$SPM$ is considered a major health hazard as it can penetrate deep into the respiratory system,causing severe respiratory issues.

(A) Lead is a toxic heavy metal that can accumulate in the human body.
According to medical and environmental health standards,a blood lead level of $30 \mu g / 100 ml$ is considered a significant warning sign of lead poisoning or excessive exposure.
Levels above this threshold can cause neurological damage,developmental issues in children,and various systemic health problems.

(C) $BOD$ stands for Biochemical Oxygen Demand. It is a measure of the amount of dissolved oxygen required by aerobic microorganisms to decompose the organic matter present in a given volume of water at a specific temperature. Therefore,it is used as a quantitative measure of organic pollutants in water bodies.

(C) The phenomenon of increase in the concentration of a non-biodegradable pollutant (like $DDT$) at successive trophic levels is known as biomagnification.
Since $DDT$ is not metabolized or excreted,it accumulates in the fatty tissues of organisms.
As we move up the food chain,the concentration of $DDT$ increases because the higher trophic level organisms consume a large number of organisms from the lower trophic levels.
Therefore,the top consumers (such as fish-eating birds) exhibit the highest concentration of $DDT$ in their bodies.

(B) Minamata disease is a neurological syndrome caused by severe mercury poisoning. It was first discovered in Minamata city,Japan,in $1956$. The disease was caused by the release of methylmercury in the industrial wastewater from the Chisso Corporation's chemical factory,which bioaccumulated in shellfish and fish in Minamata Bay and the Shiranui Sea. When local residents consumed these contaminated fish and shellfish,they suffered from mercury poisoning,leading to the Minamata disease. Therefore,the correct option is $B$.

(C) Excessive irrigation without proper drainage of water leads to waterlogging in the soil.
Waterlogging draws salt to the surface of the soil.
As the water evaporates,the salt is left behind,which gradually accumulates as a crust on the land or starts collecting around the roots of the plants.
This increased concentration of salts in the soil is known as salinity,which is highly detrimental to crop growth.

(A) Biological Oxygen Demand $(BOD)$ refers to the amount of dissolved oxygen that would be consumed if all the organic matter in one liter of water were oxidized by bacteria.
When sewage (which is rich in organic matter) is mixed with river water,the population of aerobic decomposer bacteria increases significantly.
These bacteria consume large amounts of dissolved oxygen to break down the organic waste,leading to a sharp increase in the $BOD$ of the water.
Therefore,the correct statement is that $BOD$ increases when sewage is mixed with river water.

(C) 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 industrial disaster was caused by the accidental release of a highly toxic gas known as Methyl Isocyanate $(MIC)$.
Exposure to this gas resulted in thousands of immediate deaths and long-term health complications for the survivors.

(B) An algal bloom is a rapid increase or accumulation in the population of algae in freshwater or marine water systems.
It is primarily caused by the process of eutrophication,which involves the excessive enrichment of water bodies with nutrients like nitrogen and phosphorus.
These nutrients promote the excessive growth of planktonic algae,leading to the formation of algal blooms.
Therefore,algal blooms are characteristic of eutrophic lakes,which are nutrient-rich water bodies.

(A) Biomagnification refers to the increase in concentration of non-biodegradable toxic substances at successive trophic levels in a food chain.
$DDT$ (Dichlorodiphenyltrichloroethane) is a persistent organic pollutant that is not easily broken down by organisms.
As it moves up the food chain from producers to consumers,its concentration increases significantly,leading to harmful effects on higher trophic levels,such as birds of prey.
$SO_2$,$CO$,and $PAN$ are gaseous pollutants that do not undergo biomagnification.

(C) $B.O.D.$ stands for Biological Oxygen Demand.
It is a measure of the amount of dissolved oxygen required by aerobic microorganisms to decompose the organic matter present in a given volume of water.
Since it involves both the amount of organic matter (substrate) and the activity of microorganisms (decomposers),it is associated with both.

(B) $B.O.D$ stands for Biochemical Oxygen Demand. It refers to the amount of dissolved oxygen that would be consumed if all the organic matter in one liter of water were oxidized by bacteria. It is a measure of the organic pollution in a water body. Therefore,it represents the amount of $O_2$ required by microorganisms for the decomposition of organic matter.

(A) Acid rain is primarily caused by the emission of sulfur dioxide $(SO_2)$ and nitrogen oxides ($NO_x$,including $NO_2$) into the atmosphere. These gases react with water vapor,oxygen,and other chemicals in the atmosphere to form sulfuric acid $(H_2SO_4)$ and nitric acid $(HNO_3)$. These acids then fall to the ground with rain,snow,or fog,causing environmental damage. Industrial cities are major sources of these pollutants due to the combustion of fossil fuels in power plants and factories.

(B) The natural aging of a lake is a slow process that takes thousands of years. However,pollutants from man's activities like effluents from the industries and homes can radically accelerate this aging process. This phenomenon is known as $Eutrophication$ or $Cultural$ $Eutrophication$.

(C) The $BOD$ (Biochemical Oxygen Demand) is a measure of the amount of dissolved oxygen required by aerobic microorganisms to decompose the organic matter present in a given volume of water.
In the Ganga river,the primary source of organic pollution is the discharge of untreated sewage,which consists largely of human waste.
As this organic matter enters the river,microorganisms consume oxygen to break it down,leading to a significant increase in $BOD$ levels.
Therefore,human waste is the main contributor to the high $BOD$ in the Ganga river.

(A) Atmospheric pollution is caused by the release of harmful substances into the atmosphere.
$SO_2$ (Sulfur dioxide) is a major pollutant causing acid rain.
$CO_2$ (Carbon dioxide) is a greenhouse gas contributing to global warming.
$CO$ (Carbon monoxide) is a toxic gas produced by incomplete combustion.
$H_2$ (Hydrogen) is a clean fuel that produces only water $(H_2O)$ upon combustion,thus it does not cause atmospheric pollution.

(C) An $Electrostatic \text{ } Precipitator$ $(ESP)$ is a device used to remove particulate matter, such as dust and smoke, from industrial exhaust gases.
It works by charging the dust particles electrically and then collecting them on oppositely charged collecting plates.
$Scrubbers$ are used to remove gases like $SO_2$ from industrial exhaust.
$Catalytic \text{ } converters$ are used in automobiles to reduce the emission of poisonous gases like $CO$ and $NO_x$.

(D) Pollution refers to the introduction of harmful materials into the environment.
$A$. Thermal power stations release fly ash,$SO_2$,and $NO_x$ into the atmosphere.
$B$. Automobiles emit carbon monoxide,hydrocarbons,and nitrogen oxides.
$C$. Nuclear power stations generate radioactive waste,which is a significant form of pollution.
$D$. Hydroelectric power projects are considered a renewable and relatively clean source of energy. While they may cause ecological disruption (e.g.,habitat loss),they do not release chemical pollutants or greenhouse gases into the atmosphere during operation,making them the correct exception among the given choices.

(B) Non-ionizing radiation refers to electromagnetic radiation that does not have enough energy to remove electrons from atoms or molecules.
$U.V.$ (Ultraviolet) rays are a classic example of non-ionizing radiation.
Although they are non-ionizing,$U.V.$ rays have enough energy to cause chemical changes in biological molecules.
Specifically,$U.V.$ radiation,particularly $U.V.-B$,is absorbed by $DNA$,which causes the formation of pyrimidine dimers (such as thymine dimers).
This damage disrupts the structure of $DNA$ and can lead to mutations or cell death.
In contrast,$X$-rays,Gamma rays,and Beta rays are all forms of ionizing radiation.

(C) Lead $(Pb)$ is a heavy metal that was historically used as an additive in gasoline (petrol) to prevent engine knocking. When fuel is burned,lead is released into the atmosphere as particulate matter,which is highly toxic to humans,particularly affecting the nervous system and causing developmental issues in children. Therefore,it is considered one of the most hazardous metal pollutants associated with automobiles.

(D) Catalytic converters are installed in automobiles to reduce the emission of poisonous gases.
These converters utilize expensive metals such as Platinum $(Pt)$,Palladium $(Pd)$,and Rhodium $(Rh)$ as catalysts.
As exhaust gases pass through these converters,Platinum and Palladium oxidize unburnt hydrocarbons into carbon dioxide $(CO_2)$ and water $(H_2O)$,while Rhodium reduces nitrogen oxides $(NO_x)$ into nitrogen gas $(N_2)$.
Therefore,the correct option is $D$.

(B) Domestic sewage primarily consists of three types of impurities:
$1$. Suspended solids: These include sand,silt,and clay.
$2$. Colloidal materials: These include fecal matter,bacteria,cloth,and paper fibers.
$3$. Dissolved materials: These include nutrients such as nitrates,ammonia,and phosphates,along with other dissolved salts.
Therefore,the colloidal materials present in domestic sewage are fecal matter,bacteria,cloth,and paper fibers.

(B) Photochemical smog is a type of air pollution that occurs in warm,dry,and sunny climates. It is formed by the interaction of sunlight with nitrogen oxides and volatile organic compounds (VOCs) in the atmosphere. This phenomenon was first identified and studied in Los Angeles in the $1940s$ due to its specific geographical and climatic conditions,which trap pollutants.

(B) The intensity of sound is measured in decibels $(dB)$.
Normal conversation typically occurs at an intensity level ranging from $30$ to $60 \text{ dB}$.
- $10-20 \text{ dB}$ represents very quiet sounds like whispering.
- $70-90 \text{ dB}$ represents loud sounds like traffic or a vacuum cleaner.
- $120-150 \text{ dB}$ represents extremely loud sounds that can cause hearing damage,such as jet engines or rock concerts.

(A) Cotton pollen grains, specifically from the plant $Parthenium$ $hysterophorus$ (also known as Carrot grass), are a significant source of air pollution and are known to cause respiratory allergies. In the context of Indian cities, $Parthenium$ pollen is widely recognized as a major pollutant in $Delhi$.

(A) 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. As the lake's fertility increases,plant and animal life burgeons,and organic remains are deposited on the lake bottom. This process leads to high productivity in aquatic ecosystems.

(C) $DDT$ (Dichlorodiphenyltrichloroethane) is a persistent organic pollutant. When sprayed on crops,it does not remain confined to the plants. It can be carried by wind to contaminate the air,washed by rain into water bodies,and it accumulates in the soil,leading to long-term environmental pollution across all three media: air,water,and soil.

(A) Sulfur dioxide $(SO_2)$ is a major air pollutant that significantly affects plant health.
When $SO_2$ enters the plant leaves through the stomata,it reacts with water to form sulfurous acid.
This acid causes the degradation of chlorophyll molecules,a process known as chlorosis or the destruction of chlorophyll.
This leads to a reduction in the photosynthetic capacity of the plant,eventually causing leaf necrosis and stunted growth.

(B) Acid rain is primarily caused by the emission of sulfur dioxide $(SO_2)$ and nitrogen oxides ($NO_x$,including $NO_2$).
When these gases are released into the atmosphere,they react with water vapor,oxygen,and other chemicals to form sulfuric acid $(H_2SO_4)$ and nitric acid $(HNO_3)$.
These acids then fall to the ground with precipitation,leading to environmental damage such as the acidification of lakes and streams,damage to trees,and the erosion of buildings and monuments.

(A) $Agent \ Orange$ is a powerful herbicide and defoliant that was used by the $U.S.$ military during the $Vietnam \ War$. It contains a toxic contaminant known as $TCDD$ $(2,3,7,8-Tetrachlorodibenzo-p-dioxin)$,which is a type of $Dioxin$. This chemical was responsible for severe health issues and environmental damage.

(B) $DDT$ (Dichlorodiphenyltrichloroethane) was the first modern synthetic insecticide developed in the $1940s$. It became the most widely used insecticide globally due to its effectiveness in controlling agricultural pests and disease-carrying insects like mosquitoes. However,due to its persistence in the environment and bioaccumulation,its use has been banned or restricted in many countries.

(A) The Bhopal gas tragedy,which occurred on the night of December $2-3, 1984$,was caused by the accidental leakage of Methyl Isocyanate $(MIC)$ gas from the Union Carbide India Limited $(UCIL)$ pesticide plant in Bhopal,Madhya Pradesh. This incident is considered one of the world's worst industrial disasters.

(C) $D.D.T$ stands for Dichlorodiphenyltrichloroethane. It is a synthetic chemical compound that belongs to the class of organochlorines. It was widely used as an insecticide due to its effectiveness in controlling pests,but it is now largely banned in many countries due to its persistence in the environment and bioaccumulation in the food chain.

(C) Radiations are classified into two types: ionizing and non-ionizing.
$X$-rays and Gamma rays are high-energy ionizing radiations that can damage $DNA$ and cause mutations.
$UV$ (Ultraviolet) rays are generally considered non-ionizing in the context of biological damage compared to $X$-rays and Gamma rays,although they can still cause $DNA$ damage (like thymine dimers) at high intensities.
Therefore,among the given options,$UV$ rays are categorized as non-ionizing radiation.

(A) $BOD$ stands for Biochemical Oxygen Demand.
It is defined as the amount of oxygen that would be consumed if all the organic matter in one liter of water were oxidized by bacteria.
Microorganisms in sewage treatment use this oxygen to break down organic waste.
Therefore,a higher $BOD$ indicates a higher level of pollution in the water body.

(A) $BOD$ stands for Biochemical Oxygen Demand. It represents the amount of dissolved oxygen that would be consumed if all the organic matter in one liter of water were oxidized by bacteria. Sewage-polluted water contains a high amount of organic matter (biodegradable waste). As the amount of organic matter increases,the number of microorganisms (bacteria) required to decompose it also increases,leading to higher oxygen consumption. Therefore,sewage-polluted water has a significantly higher $BOD$ compared to normal,clean water.

(B) $BOD$ stands for Biochemical Oxygen Demand. It refers to the amount of dissolved oxygen that would be consumed if all the organic matter in one liter of water were oxidized by bacteria. It is a measure of the organic matter present in water,where higher $BOD$ indicates higher pollution levels.

(A) $BOD$ stands for $Biochemical Oxygen Demand$.
It refers to the amount of oxygen that would be consumed if all the organic matter in $1$ liter of water were oxidized by bacteria.
Therefore,$BOD$ is an indirect measure of the amount of biodegradable organic matter present in a water sample.
Higher $BOD$ indicates higher pollution levels due to organic waste.

(A) The $BOD$ (Biochemical Oxygen Demand) refers to the amount of the oxygen that would be consumed if all the organic matter in one liter of water were oxidized by bacteria. It is a measure of the organic matter present in the water. The greater the $BOD$ of waste water,the more is its polluting potential. Therefore,$BOD$ is used as a measure of the amount of organic matter in water.

(D) $BOD$ stands for Biochemical Oxygen Demand. It refers to the amount of oxygen that would be consumed if all the organic matter in one liter of water were oxidized by bacteria. Therefore,a higher $BOD$ indicates a higher concentration of organic pollutants in the water,which leads to increased microbial activity and higher levels of pollution.

(A) $BOD$ refers to the amount of oxygen that would be consumed if all the organic matter in one liter of water were oxidized by bacteria.
As bacteria break down and consume the organic matter present in the water,the total amount of organic matter decreases.
Since $BOD$ is directly proportional to the amount of organic matter,the consumption of organic matter leads to a decrease in the $BOD$ value of the water body.

(A) $BOD$ stands for Biochemical Oxygen Demand. It refers to the amount of dissolved oxygen that would be consumed if all the organic matter in one liter of water were oxidized by bacteria.
Greater $BOD$ indicates that there is a higher amount of biodegradable organic matter present in the water,which requires more oxygen for decomposition.
Therefore,a higher $BOD$ value is a direct indicator of high water pollution levels.

(D) Chemically synthesized pesticides are toxic substances used to control pests.
When applied to crops,they can contaminate the soil,leach into groundwater or run off into surface water bodies,and can also be dispersed into the air through spray drift or volatilization.
Therefore,they contribute to the pollution of soil,water,and air.

(B) Aerosols are fine solid or liquid particles suspended in the atmosphere. They act as environmental pollutants that negatively impact agricultural productivity by reducing sunlight reaching crops and altering precipitation patterns. Therefore,the statement that they cause increased agricultural productivity is incorrect.

(C) $(BOD)$ is a measure of the amount of dissolved oxygen required by aerobic microorganisms to break down the organic matter present in a given volume of water.
It is an effective indicator for biodegradable organic pollutants.
Domestic sewage,dairy industry effluents,and sugar industry effluents contain high amounts of biodegradable organic matter.
However,effluents from the petroleum industry contain non-biodegradable hydrocarbons and toxic chemicals that cannot be easily broken down by aerobic decomposers.
Therefore,$(BOD)$ is not a reliable index for measuring pollution in water bodies receiving effluents from the petroleum industry.

(D) : High amount of organic waste in a lake will trigger and activate decomposer microbes,which will decompose the organic waste.
Biochemical Oxygen Demand $(BOD)$ of this lake will shoot up,and decomposers will utilize most of the dissolved oxygen present in the lake.
Consequently,the level of dissolved oxygen will decrease to an alarming extent.
Aquatic animals like fish,which totally depend on the oxygen dissolved in water,will ultimately die due to suffocation.