1Which of the following best defines environmental pollution?
Definition, types and causes of environmental pollution
Easy
A.The conservation of natural resources
B.The addition of harmful substances into the environment
C.The planting of trees in urban areas
D.The natural cycling of nutrients in ecosystems
Correct Answer: The addition of harmful substances into the environment
Explanation:
Environmental pollution is the introduction of contaminants or harmful substances into the natural environment, causing adverse changes.
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2A substance that causes pollution is known as a:
Definition, types and causes of environmental pollution
Easy
A.Catalyst
B.Nutrient
C.Solvent
D.Pollutant
Correct Answer: Pollutant
Explanation:
A pollutant is any substance introduced into the environment that has undesirable or harmful effects.
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3Which gas is the main pollutant released by vehicles due to incomplete combustion of fuel?
Air pollution: effects and controls
Easy
A.Helium
B.Nitrogen
C.Oxygen
D.Carbon monoxide
Correct Answer: Carbon monoxide
Explanation:
Incomplete combustion of fuel in vehicles produces carbon monoxide (), a toxic air pollutant.
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4Which device is commonly used to control particulate matter in industrial chimneys?
Air pollution: effects and controls
Easy
A.Air conditioner
B.Water sprinkler
C.Ceiling fan
D.Electrostatic precipitator
Correct Answer: Electrostatic precipitator
Explanation:
Electrostatic precipitators remove fine particulate matter from industrial exhaust gases using electric charge.
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5Which of the following is a common cause of water pollution?
Water pollution: effects and controls
Easy
A.Rainwater harvesting
B.Discharge of untreated sewage into rivers
C.Planting aquatic plants
D.Building check dams
Correct Answer: Discharge of untreated sewage into rivers
Explanation:
Releasing untreated sewage into water bodies adds harmful microbes and organic matter, causing water pollution.
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6The enrichment of water bodies with excess nutrients leading to algal blooms is called:
Water pollution: effects and controls
Easy
A.Sedimentation
B.Distillation
C.Eutrophication
D.Filtration
Correct Answer: Eutrophication
Explanation:
Eutrophication is the excessive growth of algae due to nutrient enrichment, depleting oxygen in water.
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7Which of the following is a major cause of soil pollution?
Soil pollution: effects and controls
Easy
A.Organic composting
B.Mulching with dry leaves
C.Crop rotation
D.Excessive use of chemical fertilizers and pesticides
Correct Answer: Excessive use of chemical fertilizers and pesticides
Explanation:
Overuse of chemical fertilizers and pesticides contaminates the soil and reduces its fertility over time.
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8Which practice helps control soil pollution?
Soil pollution: effects and controls
Easy
A.Using biofertilizers and organic manure
B.Spraying more pesticides
C.Dumping industrial waste on land
D.Overusing plastic sheets
Correct Answer: Using biofertilizers and organic manure
Explanation:
Biofertilizers and organic manure reduce chemical load on soil, helping control soil pollution.
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9Noise pollution is measured in which unit?
Noise pollution: effects and controls
Easy
A.Newton
B.Kelvin
C.Decibel
D.Pascal
Correct Answer: Decibel
Explanation:
The intensity of sound and noise pollution is measured in decibels ().
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10Which of the following is a harmful effect of noise pollution on humans?
Noise pollution: effects and controls
Easy
A.Better digestion
B.Hearing loss
C.Improved eyesight
D.Stronger bones
Correct Answer: Hearing loss
Explanation:
Prolonged exposure to loud noise can damage hearing and lead to permanent hearing loss.
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11Which of the following is a natural source of radiation pollution?
Radiation pollution: effects and controls
Easy
A.Cosmic rays from the sun
B.Vehicle exhaust
C.Sewage water
D.Plastic bags
Correct Answer: Cosmic rays from the sun
Explanation:
Cosmic rays and radioactive elements in the earth are natural sources of radiation.
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12Exposure to high levels of radiation can cause which of the following?
Radiation pollution: effects and controls
Easy
A.Better vision
B.Cancer
C.Faster hair growth
D.Increased immunity
Correct Answer: Cancer
Explanation:
High doses of radiation damage cells and DNA, increasing the risk of cancer.
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13Which of the following is considered an emerging pollutant?
Emerging pollutants
Easy
A.Carbon dioxide
B.Rainwater
C.Pharmaceutical residues in water
D.Sand
Correct Answer: Pharmaceutical residues in water
Explanation:
Emerging pollutants include pharmaceuticals, personal care products, and microplastics that are newly recognized as harmful.
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14Bursting of fireworks mainly contributes to which type of pollution besides air pollution?
Fireworks and their ill-effects
Easy
A.Soil pollution
B.Water pollution
C.Thermal pollution
D.Noise pollution
Correct Answer: Noise pollution
Explanation:
Fireworks produce loud sounds and smoke, causing both noise and air pollution.
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15Which gas is the main contributor to global warming?
Global warming
Easy
A.Argon
B.Oxygen
C.Nitrogen
D.Carbon dioxide
Correct Answer: Carbon dioxide
Explanation:
Carbon dioxide () is the primary greenhouse gas responsible for global warming.
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16Which of the following is a likely consequence of climate change?
Climate change
Easy
A.Reduction in extreme weather events
B.Rising sea levels
C.Increase in ozone layer thickness
D.Cooling of all oceans
Correct Answer: Rising sea levels
Explanation:
Climate change causes melting of glaciers and thermal expansion of water, leading to rising sea levels.
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17Which group of chemicals is mainly responsible for ozone layer depletion?
Ozone layer depletion
Easy
A.Chlorofluorocarbons (CFCs)
B.Nitrates
C.Carbohydrates
D.Proteins
Correct Answer: Chlorofluorocarbons (CFCs)
Explanation:
CFCs release chlorine atoms in the stratosphere that break down ozone () molecules.
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18Acid rain is mainly caused by the emission of which gases?
Acid rain
Easy
A.Sulphur dioxide and nitrogen oxides
B.Methane and hydrogen
C.Oxygen and nitrogen
D.Helium and neon
Correct Answer: Sulphur dioxide and nitrogen oxides
Explanation:
and react with water vapour in the atmosphere to form acids that fall as acid rain.
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19Which of the following is an example of biodegradable waste?
Solid waste management
Easy
A.Vegetable peels
B.Plastic bottles
C.Aluminium cans
D.Glass pieces
Correct Answer: Vegetable peels
Explanation:
Vegetable peels are organic and can be broken down naturally by microorganisms, making them biodegradable.
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20The '3 R' principle of waste management stands for:
Control measures of urban and industrial waste
Easy
A.Remove, Repair, Restore
B.Read, Recall, Review
C.Reduce, Reuse, Recycle
D.Reject, Reserve, Return
Correct Answer: Reduce, Reuse, Recycle
Explanation:
The 3 R principle — Reduce, Reuse, Recycle — helps minimize waste generation and manage it efficiently.
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21A factory releases pollutants that are not harmful themselves but react with sunlight to form toxic compounds like smog. These original pollutants are best classified as:
Definition, types and causes of environmental pollution
Medium
A.Secondary pollutants
B.Primary pollutants
C.Tertiary pollutants
D.Biodegradable pollutants
Correct Answer: Primary pollutants
Explanation:
Primary pollutants are emitted directly from a source. When they react in the atmosphere to form new harmful substances (like smog), those products are secondary pollutants. Since the original emissions are released directly, they are primary pollutants.
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22A device used in industries removes particulate matter from exhaust gases by charging the particles and collecting them on oppositely charged plates. This device is a(n):
Air pollution: effects and controls
Medium
A.Cyclone separator
B.Wet scrubber
C.Electrostatic precipitator
D.Fabric bag filter
Correct Answer: Electrostatic precipitator
Explanation:
An electrostatic precipitator charges particles as gas passes through and attracts them onto collector plates of opposite charge, achieving high removal efficiency for fine particulates.
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23Carbon monoxide (CO) is dangerous to humans mainly because it:
Air pollution: effects and controls
Medium
A.Binds to hemoglobin more strongly than oxygen
B.Dissolves in blood to form carbonic acid
C.Reacts with skin to cause burns
D.Directly damages lung tissue on contact
Correct Answer: Binds to hemoglobin more strongly than oxygen
Explanation:
CO has about 200–250 times greater affinity for hemoglobin than oxygen, forming carboxyhemoglobin. This reduces the blood's oxygen-carrying capacity, causing suffocation of tissues.
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24A lake shows heavy algal growth, low dissolved oxygen, and fish deaths after receiving fertilizer runoff. This process is called:
Water pollution: effects and controls
Medium
A.Biomagnification
B.Eutrophication
C.Bioremediation
D.Acidification
Correct Answer: Eutrophication
Explanation:
Nutrient enrichment (nitrogen and phosphorus) from runoff triggers algal blooms. When algae die and decompose, oxygen is depleted, killing aquatic life. This nutrient-driven degradation is eutrophication.
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25A high Biochemical Oxygen Demand (BOD) value in a water sample indicates:
Water pollution: effects and controls
Medium
A.High concentration of dissolved oxygen
B.Safe and clean drinking water
C.Low bacterial activity present
D.High level of organic pollution
Correct Answer: High level of organic pollution
Explanation:
BOD measures the oxygen microbes need to decompose organic matter. A high BOD means more organic pollutants are present, so more oxygen is consumed, indicating heavily polluted water.
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26Repeated use of chemical pesticides on farmland often leads to a long-term problem because these chemicals:
Soil pollution: effects and controls
Medium
A.Rapidly evaporate into the air
B.Convert into harmless nutrients
C.Persist and accumulate in the soil
D.Immediately dissolve and wash away
Correct Answer: Persist and accumulate in the soil
Explanation:
Many pesticides are persistent and non-biodegradable, so they build up in soil over time, harming soil microorganisms and entering food chains through crops.
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27The intensity of sound is measured on a logarithmic scale. An increase from 60 dB to 90 dB represents an increase in intensity by a factor of:
Noise pollution: effects and controls
Medium
A.30
B.500
C.1000
D.100
Correct Answer: 1000
Explanation:
The decibel scale is logarithmic: every 10 dB increase means a 10-fold increase in intensity. A 30 dB rise equals times the intensity.
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28Planting dense rows of trees and shrubs along a highway helps control noise pollution primarily by:
Noise pollution: effects and controls
Medium
A.Increasing the speed of sound
B.Amplifying low-frequency noise
C.Absorbing and deflecting sound waves
D.Converting noise into heat energy
Correct Answer: Absorbing and deflecting sound waves
Explanation:
Green belts act as natural sound barriers. Leaves and branches absorb, scatter, and deflect sound waves, reducing the noise that reaches nearby areas.
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29Which of the following is a natural source of background radiation exposure?
Radiation pollution: effects and controls
Medium
A.Radon gas from soil and rocks
B.Television and mobile screens
C.Nuclear power plant leaks
D.X-ray machines in hospitals
Correct Answer: Radon gas from soil and rocks
Explanation:
Radon is a naturally occurring radioactive gas released from uranium-bearing rocks and soil. It is a major natural contributor to background radiation, unlike the man-made sources listed.
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30Microplastics are considered emerging pollutants of concern mainly because they:
Emerging pollutants
Medium
A.Decompose quickly in seawater
B.Neutralize other water pollutants
C.Enter food chains and are hard to remove
D.Dissolve completely in water
Correct Answer: Enter food chains and are hard to remove
Explanation:
Microplastics are tiny, persistent particles that are ingested by aquatic organisms and move up the food chain. Their small size makes them extremely difficult to filter or remove from the environment.
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31The colorful sparks and smoke from fireworks release harmful heavy metals into the air. The green color in fireworks is typically produced by compounds of:
Fireworks and their ill-effects
Medium
A.Barium
B.Sodium
C.Copper
D.Strontium
Correct Answer: Barium
Explanation:
Barium compounds produce green colors in fireworks. Barium is toxic and, along with other metals released, contributes to air pollution and respiratory problems after celebrations.
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32Which gas contributes the largest share to human-induced global warming despite others being more potent per molecule?
Global warming
Medium
A.Methane ()
B.Chlorofluorocarbons (CFCs)
C.Nitrous oxide ()
D.Carbon dioxide ()
Correct Answer: Carbon dioxide ()
Explanation:
Although methane and CFCs trap more heat per molecule, is emitted in far larger quantities from fossil fuel burning, making it the largest overall contributor to global warming.
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33Melting of polar ice caps accelerates warming through a feedback loop because ice normally:
Climate change
Medium
A.Absorbs and stores heat energy
B.Reflects sunlight back to space
C.Blocks ocean currents completely
D.Releases greenhouse gases
Correct Answer: Reflects sunlight back to space
Explanation:
Ice has high albedo, reflecting solar radiation. As it melts, darker water and land absorb more heat, causing further warming and more melting — a positive feedback loop.
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34Chlorofluorocarbons (CFCs) deplete the ozone layer because in the stratosphere they release:
Ozone layer depletion
Medium
A.Fluorine gas that reflects ozone
B.Chlorine atoms that destroy ozone
C.Oxygen atoms that form ozone
D.Carbon atoms that absorb ozone
Correct Answer: Chlorine atoms that destroy ozone
Explanation:
UV radiation breaks CFCs to release free chlorine atoms. Each chlorine atom catalytically destroys thousands of ozone molecules (), thinning the protective ozone layer.
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35The international agreement specifically aimed at phasing out ozone-depleting substances is the:
Ozone layer depletion
Medium
A.Montreal Protocol
B.Paris Agreement
C.Basel Convention
D.Kyoto Protocol
Correct Answer: Montreal Protocol
Explanation:
The Montreal Protocol (1987) targets substances like CFCs that deplete the ozone layer. The Kyoto Protocol and Paris Agreement address greenhouse gases, and Basel deals with hazardous waste.
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36Acid rain is primarily caused by the atmospheric conversion of which two gases into acids?
Acid rain
Medium
A. and
B. and
C. and
D. and
Correct Answer: and
Explanation:
Sulfur dioxide and nitrogen oxides from fossil fuel combustion react with water vapor to form sulfuric and nitric acids, which fall as acid rain.
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37Acid rain harms agriculture most directly by:
Impacts on human communities and agriculture
Medium
A.Adding nitrogen fertilizer to crops
B.Increasing soil fertility rapidly
C.Raising the soil pH sharply
D.Leaching nutrients from the soil
Correct Answer: Leaching nutrients from the soil
Explanation:
Acid rain washes away essential nutrients like calcium and magnesium from soil and releases toxic aluminum, damaging plant roots and reducing crop yields.
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38The 1984 Bhopal Gas Tragedy in India was caused by the leakage of which toxic gas?
Case studies on pollution
Medium
A.Chlorine gas
B.Carbon monoxide
C.Sulfur dioxide
D.Methyl isocyanate (MIC)
Correct Answer: Methyl isocyanate (MIC)
Explanation:
The Bhopal disaster resulted from the accidental release of methyl isocyanate (MIC) from a pesticide plant, causing thousands of deaths and long-term health effects.
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39Minamata disease, a famous pollution case study in Japan, was caused by consuming seafood contaminated with:
Case studies on pollution
Medium
A.Mercury
B.Arsenic
C.Lead
D.Cadmium
Correct Answer: Mercury
Explanation:
Minamata disease resulted from methylmercury discharged into Minamata Bay. It bioaccumulated in fish, and people who ate the fish suffered severe neurological damage. Cadmium caused a different disease (Itai-itai).
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40In the waste management hierarchy, which option is considered the most preferred approach?
Solid waste management
Medium
A.Recycle the materials
B.Incinerate the waste
C.Reduce (source reduction)
D.Landfill disposal
Correct Answer: Reduce (source reduction)
Explanation:
The waste hierarchy prioritizes Reduce > Reuse > Recycle > Recover > Dispose. Reducing waste at the source is most preferred because it prevents waste generation entirely.
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41An electrostatic precipitator (ESP) in a coal power plant achieves 98% collection efficiency for fly ash, but stack monitoring still shows high fine-particle () emissions relative to total mass captured. What is the most likely explanation?
Air pollution: effects and controls
Hard
A.Fine particles carry no electrical charge and are chemically inert to the field
B.ESPs are designed only to capture gaseous pollutants, not particulates
C.ESP collection efficiency drops sharply for the smallest particle sizes, which carry disproportionate number but low mass
D.The 98% figure refers only to the mass captured after the particles leave the stack
Correct Answer: ESP collection efficiency drops sharply for the smallest particle sizes, which carry disproportionate number but low mass
Explanation:
ESP efficiency follows a size-dependent curve with a minimum in the – range. Because efficiency is mass-based, a high overall figure can coexist with poor capture of fine particles that dominate particle count and pose the greatest health risk.
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42A lake receiving treated sewage shows a sudden fish kill during a hot, still summer night despite low daytime BOD readings. Which mechanism best explains the timing?
Water pollution: effects and controls
Hard
A.Cooler night temperatures increase oxygen solubility and cause gas-bubble disease
B.BOD is highest at night because bacterial decomposition halts during daylight
C.Nighttime respiration by algae and bacteria depletes dissolved oxygen without daytime photosynthetic replenishment
D.Increased daytime photosynthesis raises oxygen to toxic supersaturation levels overnight
Correct Answer: Nighttime respiration by algae and bacteria depletes dissolved oxygen without daytime photosynthetic replenishment
Explanation:
In eutrophic waters, algae produce oxygen by day but consume it by night through respiration. On warm, still nights oxygen solubility is low and there is no photosynthesis, so dissolved oxygen crashes, causing fish kills.
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43Rainwater with dissolved in equilibrium has a pH near . A sample measures pH . Approximately how many times more acidic (higher ) is this sample than normal rain?
Acid rain
Hard
A.About 14 times
B.About 140 times
C.About 25 times
D.About 1.4 times
Correct Answer: About 25 times
Explanation:
The pH difference is . The ratio is . So the sample is roughly 25 times more acidic than natural rainwater.
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44Why does the ozone hole form most severely over Antarctica in early spring rather than year-round or over the tropics?
Ozone layer depletion
Hard
A.Antarctic ozone is naturally thinner because of the continent's high altitude
B.The tropics receive too little UV radiation to break down ozone molecules
C.Chlorofluorocarbons are heavier than air and settle only over the poles
D.Polar stratospheric clouds form in the extreme winter cold and activate chlorine, which destroys ozone rapidly when spring sunlight returns
Correct Answer: Polar stratospheric clouds form in the extreme winter cold and activate chlorine, which destroys ozone rapidly when spring sunlight returns
Explanation:
The polar vortex creates extreme cold that forms polar stratospheric clouds. These convert reservoir chlorine into reactive forms. When sunlight returns in spring, catalytic cycles destroy ozone very rapidly, producing the hole.
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45Two gases are released in equal masses: methane and carbon dioxide. Over a 20-year horizon methane has a global warming potential (GWP) of about 84, but over 100 years it falls to about 28. What best explains this decline?
Global warming
Hard
A.Methane has a short atmospheric lifetime, so its warming effect concentrates in early years and diminishes over longer horizons
B.Methane is gradually converted into a more powerful greenhouse gas over time
C.Carbon dioxide is removed from the atmosphere faster than methane over a century
D.GWP values decrease because methane's radiative efficiency increases with time
Correct Answer: Methane has a short atmospheric lifetime, so its warming effect concentrates in early years and diminishes over longer horizons
Explanation:
Methane persists roughly a decade before oxidizing, while lingers for centuries. GWP integrates forcing over the chosen horizon, so methane's short life makes its relative impact larger at 20 years and smaller at 100 years.
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46In the integrated waste management hierarchy, why is 'source reduction' ranked above 'recycling' even though both reduce landfill volume?
Solid waste management
Hard
A.Source reduction is the only method that generates saleable recovered materials
B.Recycling produces more greenhouse gases than landfilling in all cases
C.Source reduction avoids the energy, material, and pollution costs of producing, collecting, and reprocessing waste entirely
D.Recycling cannot be applied to any post-consumer packaging material
Correct Answer: Source reduction avoids the energy, material, and pollution costs of producing, collecting, and reprocessing waste entirely
Explanation:
Recycling still requires collection, transport, and reprocessing, all of which consume energy and generate emissions. Source reduction prevents the material from being produced at all, eliminating the entire downstream burden, so it sits at the top of the hierarchy.
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47Two machines each produce individually. When operated together, what is the approximate combined sound level, and why isn't it ?
Noise pollution: effects and controls
Hard
A.About , because decibel values add arithmetically
B.About , because sound levels add as the square root of the sum
C.About , because decibels are logarithmic and doubling intensity adds only
D.About , because identical sources cannot increase the total level
Correct Answer: About , because decibels are logarithmic and doubling intensity adds only
Explanation:
The decibel scale is logarithmic. Two equal sources double the total intensity, and . So combined level is about , not the arithmetic sum.
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48A radioactive isotope used in a leaked source has a half-life of 30 years. Approximately what fraction of the original activity remains after 120 years?
Radiation pollution: effects and controls
Hard
A.
B.
C.
D.
Correct Answer:
Explanation:
The number of half-lives is . Remaining activity . This is characteristic of Cs-137, a key contaminant in nuclear accidents.
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49The Bhopal Gas Tragedy (1984) resulted from the release of methyl isocyanate (MIC). Which combination of failures most directly turned a storage problem into a mass-casualty disaster?
Case studies on pollution
Hard
A.Water entered an MIC tank triggering a runaway exothermic reaction while safety systems (scrubber, flare, refrigeration) were non-functional
B.A deliberate explosion ignited stored pesticides that were otherwise safely contained
C.An earthquake ruptured all storage tanks simultaneously overwhelming the flare tower
D.MIC leaked slowly over months and accumulated in groundwater before igniting
Correct Answer: Water entered an MIC tank triggering a runaway exothermic reaction while safety systems (scrubber, flare, refrigeration) were non-functional
Explanation:
Water contamination caused a violent exothermic reaction, generating heat and pressure. The vent gas scrubber, flare tower, and refrigeration unit were inoperative or undersized, so toxic MIC vapor escaped uncontrolled over the sleeping city.
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50A persistent organic pollutant with a bioconcentration factor (BCF) of 5,000 is present at in lake water. Assuming BCF applies directly, what is its expected concentration in fish tissue?
Water pollution: effects and controls
Hard
A.
B.
C.
D.
Correct Answer:
Explanation:
Tissue concentration BCF water concentration . This illustrates biomagnification of lipophilic, persistent pollutants up the food chain.
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51A temperature inversion over a city traps pollutants near the ground. Which vertical temperature profile defines an inversion and explains the trapping?
Air pollution: effects and controls
Hard
A.Temperature increases then decreases, pushing pollutants upward into the stratosphere
B.Temperature increases with altitude, so cooler dense air below cannot rise to disperse pollutants
C.Temperature stays constant with altitude, allowing free horizontal winds only
D.Temperature decreases sharply with altitude, causing rapid vertical mixing
Correct Answer: Temperature increases with altitude, so cooler dense air below cannot rise to disperse pollutants
Explanation:
Normally temperature falls with height. In an inversion a warm layer sits above cooler surface air. The dense cool air cannot rise through the warm cap, so pollutants accumulate near ground level, as in the London and Los Angeles smog episodes.
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52Phytoremediation is proposed to clean a lead-contaminated site. What is the key limitation that distinguishes lead cleanup from organic-contaminant phytoremediation?
Soil pollution: effects and controls
Hard
A.Plants cannot take up lead at all because it is insoluble in every soil condition
B.Lead is rapidly broken down by root enzymes into harmless mineral forms
C.Lead volatilizes from leaves, simply transferring the problem to the air
D.Lead is an element that plants can only accumulate, not degrade, so the harvested biomass becomes hazardous waste needing disposal
Correct Answer: Lead is an element that plants can only accumulate, not degrade, so the harvested biomass becomes hazardous waste needing disposal
Explanation:
Organic pollutants can be metabolized and degraded by plants and microbes. Metals like lead are elemental and cannot be destroyed; phytoextraction merely concentrates them in biomass, which must then be treated or disposed of as hazardous material.
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53Why are pharmaceuticals and personal care products (PPCPs) considered problematic 'emerging pollutants' even at nanogram-per-litre concentrations?
Emerging pollutants
Hard
A.They are only harmful at very high industrial-spill concentrations
B.Conventional treatment plants aren't designed to remove them, and continuous exposure can cause biological effects like endocrine disruption and antibiotic resistance
C.They rapidly break down into oxygen and water, depleting dissolved gases
D.They bind permanently to soil and never reach aquatic systems
Correct Answer: Conventional treatment plants aren't designed to remove them, and continuous exposure can cause biological effects like endocrine disruption and antibiotic resistance
Explanation:
PPCPs are biologically active by design and continuously introduced through excretion and disposal. Standard wastewater treatment doesn't target them, so chronic low-level exposure can disrupt endocrine systems and promote antibiotic-resistant organisms.
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54The colors in fireworks come from metal salts, some of which pose health and environmental hazards. Which pairing of colorant and its principal concern is correct?
Fireworks and their ill-effects
Hard
A.Copper salts produce red and are the primary source of radioactive fallout
B.Barium salts produce green and are toxic, causing respiratory and gastrointestinal effects
C.Strontium salts produce blue and release ozone-depleting halogens
D.Sodium salts produce green and are the main cause of acid rain from fireworks
Correct Answer: Barium salts produce green and are toxic, causing respiratory and gastrointestinal effects
Explanation:
Barium compounds give green colors and are toxic to humans. Strontium gives red, copper gives blue, and sodium gives yellow. Fireworks also release fine particulates and perchlorates, worsening short-term air and water quality.
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55Melting Arctic sea ice is often cited as a positive feedback loop accelerating warming. Which mechanism correctly describes this feedback?
Climate change
Hard
A.Loss of reflective ice exposes darker ocean that absorbs more solar radiation, causing further warming and more melting
B.Exposed ocean reflects more sunlight than ice, but the released freshwater traps heat
C.Sea-ice melt increases planetary albedo, which paradoxically raises temperatures
D.Melting ice releases stored oxygen that intensifies the greenhouse effect
Correct Answer: Loss of reflective ice exposes darker ocean that absorbs more solar radiation, causing further warming and more melting
Explanation:
This is the ice-albedo feedback. Bright ice reflects sunlight (high albedo); dark open water absorbs it (low albedo). As ice melts, more heat is absorbed, warming the region and melting still more ice, a self-reinforcing cycle.
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56A pollutant discharged into a river breaks down naturally within days into harmless products, while another persists for decades and accumulates in tissues. How are these classified?
Definition, types and causes of environmental pollution
Hard
A.The first is a point-source pollutant; the second is a non-point-source pollutant
B.Both are secondary pollutants differing only in concentration
C.The first is a primary pollutant; the second is a secondary pollutant
D.The first is biodegradable (non-persistent); the second is non-biodegradable (persistent)
Correct Answer: The first is biodegradable (non-persistent); the second is non-biodegradable (persistent)
Explanation:
Biodegradable pollutants decompose quickly through natural processes. Non-biodegradable (persistent) pollutants like DDT, heavy metals, and many plastics resist breakdown, accumulate, and biomagnify, making them far more hazardous long-term.
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57Photochemical smog and classical (London-type) smog differ fundamentally in chemistry. Which statement correctly contrasts them?
Air pollution: effects and controls
Hard
A.Photochemical smog is oxidizing and forms in warm sunlight from and hydrocarbons; London smog is reducing and forms in cold moist air from and smoke
B.Photochemical smog is reducing and forms at night; London smog is oxidizing and needs sunlight
C.Both require sunlight and are dominated by sulphur dioxide and soot
D.Photochemical smog forms from oxidation while London smog forms from ozone
Correct Answer: Photochemical smog is oxidizing and forms in warm sunlight from and hydrocarbons; London smog is reducing and forms in cold moist air from and smoke
Explanation:
Photochemical smog requires sunlight to convert and volatile hydrocarbons into ozone and PAN (oxidizing). Classical London smog forms in cold, humid, sunless conditions from coal-derived and particulates (reducing).
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58A firm evaluates incineration versus sanitary landfilling for municipal waste. Which trade-off is most accurate?
Control measures of urban and industrial waste
Hard
A.Landfilling reduces waste mass more than incineration and eliminates methane risk
B.Incineration produces no residues and no emissions; landfilling is the only method generating usable energy
C.Both methods produce identical environmental impacts, so cost is the only factor
D.Incineration drastically reduces waste volume and can recover energy but emits air pollutants and toxic ash; landfilling is cheaper but consumes land and generates methane and leachate
Correct Answer: Incineration drastically reduces waste volume and can recover energy but emits air pollutants and toxic ash; landfilling is cheaper but consumes land and generates methane and leachate
Explanation:
Incineration cuts volume by up to 90% and can generate power, but requires costly emission controls and produces hazardous fly ash. Landfills are cheaper and simpler but need land, and generate methane and leachate that demand long-term management.
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59Prolonged irrigation with poor drainage in arid regions often reduces crop yields over time. What is the primary mechanism?
B.Salinization: evaporation concentrates dissolved salts at the surface, raising soil salinity and osmotic stress on crops
C.Irrigation water cools the soil below the temperature needed for germination
D.Repeated irrigation leaches all nutrients so quickly that salts never accumulate
Correct Answer: Salinization: evaporation concentrates dissolved salts at the surface, raising soil salinity and osmotic stress on crops
Explanation:
In arid areas with poor drainage, water evaporates and leaves dissolved salts behind. Salts accumulate in the root zone, raising osmotic pressure so plants struggle to absorb water, degrading soil fertility and cutting yields.
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60During conventional sewage treatment, which sequence correctly matches the treatment stages to their principal functions?
C.Primary disinfects with chlorine; secondary removes grit; tertiary aerates the influent
D.Primary removes settleable solids physically; secondary uses microbes to degrade organic matter; tertiary removes nutrients and pathogens
Correct Answer: Primary removes settleable solids physically; secondary uses microbes to degrade organic matter; tertiary removes nutrients and pathogens
Explanation:
Primary treatment is physical (screening, sedimentation). Secondary treatment is biological, using microbes to break down dissolved and suspended organics, lowering BOD. Tertiary (advanced) treatment removes residual nutrients like nitrogen and phosphorus and disinfects.
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