Atmospheric Pollution

Atmospheric pollution refers to the introduction of harmful substances into the Earth’s air, causing adverse effects on living organisms and the environment. This contamination primarily arises from human activities, especially the burning of fossil fuels like coal, petrol, and diesel in industries, vehicles, and power plants. The major gaseous pollutants include carbon monoxide, sulfur dioxide, nitrogen oxides, and unburnt hydrocarbons. Additionally, particulate matter, such as soot, dust, and smoke, along with substances like chlorofluorocarbons (CFCs), contribute significantly to degrading air quality.

The consequences of this pollution are severe and multifaceted. On human health, it leads to respiratory problems like asthma, bronchitis, and lung damage, while also irritating the eyes and throat. Environmentally, sulfur and nitrogen oxides dissolve in rainwater to form acid rain, which damages buildings, monuments, forests, and aquatic life. Pollutants like CFCs deplete the protective ozone layer, increasing exposure to harmful ultraviolet rays. Furthermore, the excessive buildup of carbon dioxide and methane from activities like deforestation and agriculture traps heat in the atmosphere, leading to global warming and climate change with its associated risks like melting glaciers and extreme weather.

Controlling atmospheric pollution requires concerted efforts. Switching to cleaner fuels like CNG, using catalytic converters in vehicles, and installing electrostatic precipitators and scrubbers in industrial plants can significantly reduce emissions. On a broader scale, adopting renewable energy sources such as solar and wind power, expanding forest cover through afforestation, and enforcing strict environmental laws are crucial steps. Public awareness and individual actions, like conserving energy and using public transport, also play a vital role in ensuring cleaner air for a sustainable future.

Exercise 8 (A)

Question 1. 

1. Define the following term: Pollution 

2. Define the following term: Pollutant 

3. Define the following term: Air pollution

Ans:

1. Pollution:
   When harmful stuff gets into our surroundings, making it dirty or unsafe for people, animals, and plants.
2. Pollutant:
   Any harmful thing that causes pollution, like trash, chemicals, or smoke, which can mess up the environment.
3. Air pollution:
   Bad things in the air, such as smoke or fumes, that make it unhealthy to breathe and can harm the planet.

Question 2. 

Name any four gaseous pollutants.

Ans:

Here are four gaseous pollutants:

1. Carbon monoxide (CO)
2. Sulfur dioxide (SO2)
3. Nitrogen dioxide (NO2)
4. Methane (CH4)

Question 3. 

Name the compounds of sulphur that cause air pollution. Also, state the harmful effects of sulphur compounds.

Ans:

Sulphur compounds that contribute to air pollution primarily include sulphur dioxide (SO₂) and sulphur trioxide (SO₃). Hydrogen sulphide (H₂S) is also a pollutant in some cases.

Harmful effects of these compounds:

• Health Impacts: SO₂ and fine sulphate particles irritate the respiratory system, worsening conditions like asthma and bronchitis.
• Acid Rain: SO₂ and SO₃ react in the atmosphere to form sulphuric acid, leading to acid rain. This acidifies water bodies, harms aquatic life, and damages soils.
• Environmental Damage: Acid rain and direct exposure harm vegetation, forests, and crops, reducing growth and yield.
• Material Corrosion: Acid deposition corrodes buildings, monuments (especially limestone and marble), metals, and infrastructure.
• Smog Formation: Sulphate particles contribute to particulate matter (PM2.5), reducing visibility and forming haze, which poses additional health risks.

Question 4. 

1. State: natural sources of air pollution 

2. State: man-made sources of air pollution 

Ans:

1. Natural sources of air pollution:
   • Gases and particles from volcanic activity.
   • Dust carried by wind from dry areas.
   • Smoke from wildfires ignited naturally.
   • Decaying organic matter in marshes.
   • Airborne spores and pollen from vegetation.
2. Man-made sources of air pollution:
   • Combustion of coal, oil, and gas in industries.
   • Vehicle emissions from transportation.
   • Burning of crop residues in farming.
   • Dust and debris from construction activities.
   • Fumes from burning waste materials.

Question 5. 

1. How do the oxides of nitrogen enter the atmosphere? 

2. What are their harmful effects? 

Ans:

1. Entry of Nitrogen Oxides into the Atmosphere

Nitrogen oxides (NO and NO₂, together called NOx) primarily enter the atmosphere through high-temperature combustion processes. The most significant human-made source is the burning of fossil fuels in vehicle engines, power plants, and industrial furnaces. During combustion, the intense heat causes the nitrogen and oxygen naturally present in the air to react, forming nitric oxide (NO). Natural events like lightning strikes and volcanic eruptions also produce these gases by providing the necessary energy for the same reaction. Another important, though often overlooked, source is agricultural activity. The extensive use of nitrogen-based fertilizers in farming leads to microbial action in the soil, which releases nitrous oxide (N₂O), a potent greenhouse gas, into the air.

2. Harmful Effects of Nitrogen Oxides

The harmful effects of these oxides are wide-ranging. In terms of human health, nitrogen dioxide (NO₂) is a major contributor to respiratory problems. It irritates the airways, aggravates conditions like asthma and bronchitis, and reduces lung function. Furthermore, NOx gases react with other compounds in the atmosphere to form ground-level ozone (smog) and fine particulate matter, which are linked to chronic lung and heart diseases. Environmentally, nitrogen oxides are a key component in the formation of acid rain. They react with water, oxygen, and other chemicals to produce nitric acid, which falls as acid rain, damaging forests, aquatic ecosystems, and buildings. Additionally, nitrous oxide (N₂O) is a powerful greenhouse gas that contributes significantly to global warming and also depletes the protective ozone layer in the stratosphere. Excess nitrogen from the atmosphere can also deposit into water bodies, causing nutrient pollution and eutrophication, which leads to algal blooms and dead zones.

Question 6. 

State the origin and health impact of smog.

Ans:

Smog forms when pollutants released into the atmosphere undergo chemical reactions, often intensified by sunlight or stagnant air. The primary sources include vehicle exhaust, industrial emissions, and the burning of fossil fuels like coal and oil. These activities emit nitrogen oxides, volatile organic compounds, sulfur dioxide, and fine particulate matter. In sunlight, these substances interact to create photochemical smog, characterized by ground-level ozone. In cooler climates, industrial smog can arise from coal combustion, mixing smoke with fog. Urban areas with high traffic and industrial activity are particularly prone to smog, especially during temperature inversions that trap pollutants near the ground.

Health effects of smog are wide-ranging and significant. In the short term, inhaling smog irritates the respiratory system, leading to coughing, throat discomfort, and breathing difficulties. It aggravates conditions like asthma and bronchitis, often triggering attacks. Over time, repeated exposure can reduce lung function and contribute to chronic respiratory diseases. Smog also affects cardiovascular health, increasing risks of heart attacks and strokes due to inflammation and strain on the heart. Fine particles in smog penetrate deep into the lungs and bloodstream, potentially causing systemic inflammation. Vulnerable populations, including children, older adults, and individuals with pre-existing health issues, face heightened risks. Additionally, smog exposure has been linked to increased hospitalization rates and premature mortality. Prolonged contact may even impair immune response, raising susceptibility to infections. Overall, smog poses a serious public health challenge, underscoring the need for air quality management.

Question 7. 

What are the harmful effects of oxides of sulphur?

Ans:

The oxides of sulphur, primarily sulphur dioxide (SO₂) and sulphur trioxide (SO₃), pose significant dangers to health, the environment, and infrastructure. Their most direct impact is on human health, particularly the respiratory system. When inhaled, these gases can irritate the nose, throat, and airways, causing coughing, wheezing, and shortness of breath. They exacerbate conditions like asthma and bronchitis and can increase susceptibility to respiratory infections. Prolonged exposure to even low concentrations is harmful, especially for children, the elderly, and individuals with pre-existing health conditions.

Environmentally, the most devastating effect is the formation of acid rain. Sulphur oxides in the atmosphere react with water vapour and oxygen to form sulphuric acid, which falls to earth as acid rain. This acidification has catastrophic consequences for ecosystems. It acidifies lakes and rivers, making waters uninhabitable for fish and other aquatic life by leaching toxic aluminium from the soil. On land, it damages soil chemistry, depleting essential nutrients and harming forests, often visible through stunted tree growth and damaged leaves.

Beyond natural ecosystems, oxides of sulphur cause extensive damage to the built environment and the economy. Acid rain accelerates the corrosion of metals, limestone, and marble, leading to the deterioration of buildings, bridges, historical monuments, and statues. In agriculture, it damages crops, reduces yields, and affects soil fertility. Furthermore, SO₂ contributes to the formation of fine particulate matter (PM2.5) in the air, which reduces visibility and creates a persistent haze, impacting both safety and the quality of life in affected regions.

Question 8. 

State the main sources and effects of carbon monoxide.

Ans:

Sources of Carbon Monoxide:

Carbon monoxide primarily originates from processes where carbon-based fuels do not burn completely. Common sources include vehicle exhaust from cars, trucks, and other engines that run on gasoline or diesel. In residential settings, gas-powered appliances like furnaces, water heaters, stoves, and fireplaces can produce carbon monoxide if they are faulty or inadequately ventilated. Additional sources include industrial activities such as manufacturing and power generation, which involve combustion of fuels. Tobacco smoke from cigarettes also releases carbon monoxide, exposing smokers and those nearby. While natural events like wildfires and volcanic eruptions emit carbon monoxide, human activities remain the dominant contributors in everyday environments.

Effects of Carbon Monoxide:

On human health, carbon monoxide is hazardous because it binds to hemoglobin in red blood cells more readily than oxygen, forming carboxyhemoglobin. This reduces the blood’s oxygen-carrying capacity, leading to oxygen deprivation in tissues and organs. Initial symptoms include headache, dizziness, weakness, and nausea. Prolonged or high-level exposure can cause confusion, loss of consciousness, and fatal poisoning. Chronic exposure at lower levels may contribute to cardiovascular and neurological issues.

Environmentally, carbon monoxide plays a role in atmospheric chemistry. It reacts with other pollutants to form ground-level ozone, a key component of smog that can aggravate respiratory diseases and harm air quality. Additionally, carbon monoxide interacts with hydroxyl radicals in the atmosphere, which can indirectly increase the persistence of methane, a greenhouse gas, thereby influencing climate change patterns.

Question 9. 

Give the mechanism of the action of carbon monoxide.

Ans:

Carbon monoxide exerts its toxic effects primarily by disrupting the body’s ability to transport and utilize oxygen. Its mechanism of action operates at two critical levels: systemic oxygen transport and cellular respiration.

At the systemic level, carbon monoxide (CO) competes aggressively with oxygen (O₂) for binding sites on the hemoglobin molecule in red blood cells. Its affinity for hemoglobin is approximately 200 to 250 times greater than that of oxygen. When inhaled, CO rapidly binds to hemoglobin to form carboxyhemoglobin (COHb). This not only directly prevents oxygen from binding, reducing the blood’s oxygen-carrying capacity, but it also alters the molecular structure of the remaining hemoglobin. This change increases hemoglobin’s affinity for the oxygen molecules that do manage to bind, making it harder for oxygen to be released to the tissues that need it. This results in a situation of severe internal hypoxia, where even though oxygen may be present in the blood, it cannot be effectively delivered to organs like the brain and heart.

Beyond this blood-level effect, carbon monoxide directly interferes with cellular energy production. It binds to other iron-containing proteins, most significantly cytochrome c oxidase, which is a crucial enzyme in the mitochondrial electron transport chain. By inhibiting this final step of cellular respiration, CO blocks the cell’s ability to produce adenosine triphosphate (ATP), the primary energy currency. This causes a shift to inefficient anaerobic metabolism, leading to lactic acid buildup and cellular acidosis. The combined effect of systemic hypoxia and direct mitochondrial poisoning leads to cellular energy failure, organ dysfunction, and, if exposure is severe and prolonged, ultimately to death.

Question 10. 

How can we control carbon monoxide poisoning?

Ans:

Carbon monoxide poisoning represents a hidden yet grave danger due to the gas’s colorless and odorless nature, which can lead to lethal outcomes. Effectively managing this hazard hinges on a blend of proactive prevention, reliable detection, and prompt response. Here are practical steps to enhance safety.

Begin by identifying where carbon monoxide originates. It forms when fuels such as natural gas, propane, oil, wood, or charcoal fail to burn fully. Typical household sources include heaters, boilers, ovens, wood-burning stoves, vehicle exhausts, and portable generators. Recognizing these common emitters allows for better risk assessment in domestic or professional settings.

Prevention serves as the primary barrier against exposure. Arrange for certified technicians to install and routinely service all fuel-burning equipment. Schedule annual check-ups for heating units, flues, and exhaust ducts. Prioritize proper ventilation in spaces where fuels are utilized—keep air passages and vents unblocked. Steer clear of operating tools like generators, charcoal grills, or portable camp cookers indoors or in partially enclosed areas such as garages, even with openings. Similarly, refrain from running a vehicle’s engine inside a garage, irrespective of whether the door is up.

Equip your home with carbon monoxide detectors on each floor, focusing on locations close to bedrooms. These alarms are critical as they can warn of rising CO levels before health effects manifest. Choose models that adhere to certified safety standards, opting for long-life battery-powered devices or wired versions with backup batteries. Check alarms every month and swap out batteries when needed. Keep in mind that detectors have expiration dates; plan to replace them every five to seven years, or as directed by the product guidelines.

Learn to identify poisoning indicators. Warning signs like persistent headaches, lightheadedness, exhaustion, stomach upset, and disorientation may mirror common illnesses but usually lack fever. If these arise and carbon monoxide is suspected, seek fresh air without delay. Exit the premises and contact emergency services from outside. Always treat a sounding CO alarm as urgent—evacuate immediately and call for assistance from a safe spot. Prompt medical care is essential; treatments can range from supplemental oxygen to hyperbaric oxygen therapy for serious cases to aid recovery.

Share knowledge to broaden safety networks. Discuss carbon monoxide risks with relatives, acquaintances, and colleagues. Motivate others to adopt detectors and follow precautionary measures. Community-based actions, including awareness drives by local fire services, can further distribute educational resources and improve alarm availability.

Exercise 8 (B)

Question 1. 

Why does rainwater have a pH of less than 7?

Ans:

Rainwater is naturally slightly acidic, with a pH typically around 5.6, rather than a neutral pH of 7. This primary acidity occurs because rainwater reacts with carbon dioxide present in the Earth’s atmosphere. When carbon dioxide dissolves in the falling water droplets, it forms a weak acid known as carbonic acid. This is the same mild acid found in sparkling water. The reaction involves carbon dioxide and water molecules combining to create carbonic acid, which then partially separates into hydrogen ions and bicarbonate ions. It is the presence of these hydrogen ions that lowers the pH, giving even clean, unpolluted rainwater its characteristic slight acidity.

However, in many parts of the world, especially industrialized regions, rainwater can become far more acidic, a phenomenon known as acid rain. This heightened acidity, with pH values sometimes as low as 4, is caused by the emission of other, more potent gases into the atmosphere from human activities. The burning of fossil fuels like coal in power plants and gasoline in vehicles releases significant amounts of sulfur dioxide and nitrogen oxides. These gases undergo further chemical reactions in the atmosphere, forming strong acids—sulfuric acid and nitric acid—which then dissolve in rainwater. This results in precipitation that is significantly more corrosive than natural rainwater, posing serious risks to aquatic life, forests, and even building materials.

Question 2. 

pH of acid rain is sometimes as low as 2. Explain.

Ans:

Acid rain refers to rainfall that has become acidic due to the presence of certain pollutants in the atmosphere. The primary reason for its acidity is the release of sulfur dioxide (SO₂) and nitrogen oxides (NOₓ) from human activities, such as burning fossil fuels in power plants, factories, and vehicles. These gases undergo chemical reactions in the atmosphere to form strong acids.

When sulfur dioxide is emitted, it reacts with water vapor and oxygen to produce sulfuric acid (H₂SO₄). Similarly, nitrogen oxides form nitric acid (HNO₃). Normal rainwater is slightly acidic, with a pH around 5.6, due to carbon dioxide dissolving to form weak carbonic acid. However, when additional acids are present, the pH can drop significantly.

The pH scale measures acidity on a logarithmic scale from 0 to 14, where lower values indicate higher acidity. A decrease of one pH unit represents a tenfold increase in acidity. Therefore, acid rain with a pH of 2 is about 1,000 times more acidic than normal rainwater (pH 5.6) and 100,000 times more acidic than neutral water (pH 7).

Several factors can lead to acid rain reaching pH levels as low as 2. In areas with high industrial activity or dense traffic, concentrations of SO₂ and NOₓ can be exceptionally high. Meteorological conditions, such as low wind or temperature inversions, can trap pollutants close to the ground, allowing more acids to form. Additionally, the presence of other compounds like ammonia can sometimes enhance acid formation, though this is less common.

It’s important to note that pH 2 is at the extreme end of acid rain measurements, typically observed in heavily polluted regions or during specific events like volcanic eruptions, which also release sulfur gases. Such high acidity can harm ecosystems, corrode buildings, and affect human health, highlighting the impact of pollutant emissions.

Question 3. 

1. Explain the formation of acid rain due to: Oxides of sulphur

2. Explain the formation of acid rain due to: Oxides of nitrogen

Ans:

1. Formation of Acid Rain due to Oxides of Sulphur

The primary sulphur oxide responsible for acid rain is sulphur dioxide (SO₂). This gas is released into the atmosphere mainly from the burning of fossil fuels like coal and oil in power stations, factories, and during metal extraction from sulphide ores. Once in the air, sulphur dioxide undergoes a series of chemical reactions. It first combines with atmospheric oxygen to form sulphur trioxide (SO₃). Subsequently, both SO₂ and SO₃ dissolve in atmospheric water vapour, rain droplets, or mist. Here, they react with water to form sulphuric acid (H₂SO₄). This sulphuric acid, suspended in cloud moisture, eventually falls to the ground as acid rain, which is significantly more acidic than normal rainwater. This process is a direct consequence of industrial pollution and leads to the acidification of soils, lakes, and damage to buildings and vegetation.

2. Formation of Acid Rain due to Oxides of Nitrogen

The main nitrogen oxides involved are nitric oxide (NO) and nitrogen dioxide (NO₂), collectively called NOx. These gases form naturally during lightning strikes, but the major anthropogenic source is the high-temperature combustion in vehicle engines and thermal power plants. In these hot conditions, nitrogen and oxygen from the air, which normally do not react at room temperature, combine to form nitric oxide (NO). Upon release into the atmosphere, this nitric oxide further reacts with oxygen to produce nitrogen dioxide (NO₂), a brownish gas. Nitrogen dioxide then dissolves in atmospheric water to form a mixture of nitrous acid (HNO₂) and the stronger nitric acid (HNO₃). It is this nitric acid component in precipitation that contributes to the corrosive nature of acid rain. The increase in vehicles worldwide has made oxides of nitrogen a leading cause of acid rain, contributing to similar environmental damage as that caused by sulphuric acid.

Question 4. 

What are the causes of acid rain?

Ans:

Acid rain refers to the precipitation that contains elevated levels of acidic components, primarily sulfuric and nitric acids, which form in the atmosphere. The core causes revolve around the release of specific pollutants that undergo chemical transformations before settling on Earth.

The primary culprits are sulfur dioxide (SO₂) and nitrogen oxides (NOₓ), which are emitted into the air from both human activities and natural sources. Once released, these gases interact with water vapor, oxygen, and other atmospheric compounds to produce sulfuric acid and nitric acid. These acids then fall to the ground through rain, snow, fog, or as dry particles.

Human actions are the dominant source of these pollutants. The burning of fossil fuels—such as coal and oil—in power plants and industrial facilities is a major emitter of sulfur dioxide. Meanwhile, nitrogen oxides largely come from vehicle exhausts, especially from cars, trucks, and airplanes, due to high-temperature combustion processes. Additional industrial activities, like metal smelting and certain manufacturing operations, also contribute significant amounts of sulfur dioxide.

Natural events can release these gases as well. Volcanic eruptions discharge sulfur dioxide, while lightning strikes generate nitrogen oxides. Decomposition and wildfires may also produce small quantities. However, since the industrial era, human-generated emissions have vastly increased the concentration of these gases in the atmosphere, overshadowing natural contributions.

It’s worth noting that winds can carry these pollutants over long distances, meaning acid rain can affect regions far from the original emission sources. This transboundary nature complicates environmental management and underscores the widespread impact of human industrial and transportation activities.

Question 5. 

1. Give the impact of acid rain: On plants 

2. Give the impact of acid rain: On soil 

3. Give the impact of acid rain: On water bodies

Ans:

1. Impact of Acid Rain on Plants
Acid rain directly harms plants by eroding the protective waxy coating on leaves, similar to how steady erosion wears down rock surfaces. This damage exposes leaves to pathogens and environmental stressors, reducing their ability to perform photosynthesis effectively. Over time, foliage may develop blotches or yellowing, and growth can become stunted. Indirectly, acid rain alters soil chemistry by leaching away essential nutrients like calcium and magnesium, which plants rely on for healthy development. As a result, plants experience nutrient deficiencies, leading to weaker structures and increased susceptibility to diseases, pests, and harsh weather. In forests, this can manifest as thinning canopies and reduced regeneration of seedlings.

2. Impact of Acid Rain on Soil
Acid rain progressively increases soil acidity, which acts like a slow-acting poison for terrestrial ecosystems. This acidity mobilizes toxic metals, such as aluminum, that are naturally present but bound in soil particles. When released, aluminum can damage root systems and interfere with nutrient uptake. Additionally, key nutrients like potassium and phosphorus become less available to plants, effectively starving them even if they are physically present. The biological health of soil also declines, as acid-sensitive microorganisms—critical for decomposing organic matter and cycling nutrients—are harmed. This disruption can turn once-fertile ground into less productive land, with longer-term effects on agriculture and natural vegetation.

3. Impact of Acid Rain on Water Bodies
When acid rain flows into lakes, rivers, or streams, it can sharply lower the water’s pH, creating conditions akin to a corrosive environment for aquatic life. Many species, including fish, amphibians, and invertebrates, struggle to survive in acidic waters, leading to population declines and loss of biodiversity. A particularly damaging consequence is the leaching of aluminum from surrounding soils into the water, which is toxic to fish—it impairs gill function, reducing oxygen absorption and often causing suffocation. Over time, acidified water bodies may become “dead” zones, with simplified food webs dominated by acid-tolerant organisms like certain algae. This not only affects aquatic ecosystems but also impacts water quality for human use and recreational activities.

Question 6. 

How does a scrubber help in reducing the formation of acid rain?

Ans:

Scrubbers are pollution control devices installed primarily in industrial smokestacks, particularly at power plants that burn fossil fuels like coal. Their primary function is to remove acidic gases, most notably sulfur dioxide (SO₂), from the exhaust flue gases before they are released into the atmosphere. Since sulfur dioxide is a major contributor to the formation of sulfuric acid in acid rain, capturing it at the source directly prevents these harmful emissions from ever reaching the air and undergoing the chemical reactions that lead to acid precipitation.

The most common type is a wet scrubber, which works by spraying a fine mist of a water-based alkaline slurry—often using limestone or lime—upwards through the rising column of hot exhaust gas. The sulfur dioxide in the gas is highly soluble and reacts chemically with the alkaline slurry. This reaction neutralizes the acidic SO₂, effectively trapping it. Through this process, the gaseous pollutant is converted into a solid waste product, typically a wet sludge of calcium sulfite or calcium sulfate, which can then be collected and disposed of safely.

By intercepting and neutralizing sulfur dioxide emissions at their industrial origin, scrubbers act as a critical barrier. They significantly reduce the amount of this key acid rain precursor that is available to mix with atmospheric moisture and oxygen. Therefore, the widespread use of scrubber technology in heavy industry has been a major factor in mitigating the environmental damage caused by acid rain, helping to protect forests, aquatic ecosystems, and man-made structures from corrosive deposition.

Exercise 8 (C)

Question 1. 

What do you understand about the Green House effect?

Ans:

Earth’s atmosphere functions as a delicate, life-sustaining shield. Sunlight passes through this shield to warm the planet’s surface, which then radiates heat back toward space. Naturally occurring gases, including carbon dioxide and methane, absorb a portion of this outgoing heat, preventing it from escaping entirely. This essential mechanism, known as the greenhouse effect, maintains our planet at a stable and habitable temperature. Without this natural thermal blanket, Earth would be too cold for most life to exist.

The critical issue of our time stems from humanity drastically altering this balance. Through the large-scale combustion of coal, oil, and natural gas for energy, we are releasing ancient stores of carbon at an unprecedented rate. Simultaneously, industrial agriculture and waste management contribute significant amounts of other potent gases like methane. These activities effectively thicken the atmospheric shield, trapping substantially more heat than the planet’s natural systems are designed to manage.

This human-amplified trapping of heat is the direct driver of global warming. The consequence is a steady increase in Earth’s average temperature, which is disrupting long-standing climate patterns. This shift manifests in more extreme weather events, the rapid melting of polar ice and glaciers, and a concerning rise in global sea levels, fundamentally altering the environment upon which we depend.

Question 2. 

What are greenhouse gases? How are they responsible for global warming?

Ans:

What Are Greenhouse Gases?

Basically, they are certain types of gases in our atmosphere that act like the glass in that car. They are mostly transparent, so they let the sun’s heat energy (in the form of sunlight) pass right through to warm up the Earth’s surface. The problem is, they then trap a significant amount of that heat when it tries to radiate back out into space.

The most important ones are:

• Water Vapor (H₂O): The most common one, but its amount changes naturally with temperature.
• Carbon Dioxide (CO₂): This is the big one people talk about. It comes from burning stuff like coal, oil, and gas, and from cutting down forests.
• Methane (CH₄): Much more potent than CO₂ at trapping heat, but it doesn’t last as long in the air. It leaks from oil and gas wells, comes from livestock, and landfills.
• Nitrous Oxide (N₂O): Comes from fertilizers and certain industrial processes.
• Fluorinated Gases: Man-made chemicals used in refrigeration and other applications.

How They Cause Global Warming (The Thickening Blanket Analogy)

Imagine the Earth wrapped in a perfect, thin blanket. This blanket is our natural greenhouse effect—without it, Earth would be a frozen ball of ice, and life as we know it wouldn’t exist. The natural level of these gases has kept our planet at a stable, livable temperature for millennia.

The trouble begins when we humans add extra gases to the atmosphere, mainly by burning fossil fuels for energy, transportation, and industry. It’s like we’re piling on more and more blankets.

Here’s the step-by-step:

1. Sunlight In: Energy from the sun, mostly as visible light, passes freely through the atmosphere and warms the land and oceans.
2. Heat Out: The warmed Earth naturally releases this energy back upward as infrared radiation (what we feel as heat).
3. The Trap: The increased concentration of greenhouse gases (especially CO₂ and methane) absorbs and re-radiates much of this outgoing heat energy.
4. The Buildup: Instead of escaping into space, the heat is sent back toward the Earth’s surface, warming the planet even more.

This isn’t a theory about a future event; it’s a confirmed physical process. We’ve measured a massive spike in CO₂ levels since the industrial revolution, directly correlating with the rise in global average temperatures. The more greenhouse gases we pump out, the thicker the “blanket” gets, and the more heat gets trapped.

This extra energy doesn’t just make things a little warmer. It acts like a fever in the Earth’s climate system, disrupting long-stable patterns. It melts ice sheets and glaciers (raising sea levels), fuels more intense storms and droughts, shifts rainfall patterns, and acidifies the oceans. In short, by drastically altering the mix of gases in our air, we are fundamentally changing the energy balance of the entire planet.

Question 3. 

1. State the sources and effects of the following gas: Carbon dioxide 

2. State the sources and effects of the following gas: Methane 

3. State the sources and effects of the following gas: Water vapor

Ans:

Carbon Dioxide
Carbon dioxide originates from both natural and human-driven sources. Naturally, it is released during volcanic eruptions, the respiration processes of animals and plants, and the decomposition of organic materials. Human activities significantly amplify its presence, primarily through the combustion of fossil fuels like coal, oil, and natural gas for energy production, heating, and transportation. Additional human sources include deforestation, which reduces carbon absorption, and industrial activities such as cement manufacturing. The effects of carbon dioxide are profound on climate and ecosystems. As a greenhouse gas, it traps heat in the atmosphere, contributing to global warming. This warming leads to climate change impacts like rising sea levels from melting ice, more frequent extreme weather events, and shifts in agricultural zones. Furthermore, carbon dioxide dissolving in oceans causes acidification, damaging marine life, particularly coral reefs and shell-forming organisms.

Methane
Methane emissions arise from natural and anthropogenic sources. Natural sources include wetlands, where microbial activity produces methane, as well as emissions from termites and oceanic vents. Human activities are major contributors, notably agriculture through livestock digestion (enteric fermentation) and rice cultivation, which create anaerobic conditions that release methane. Other human sources involve waste management in landfills, the extraction and processing of fossil fuels like coal, oil, and natural gas, and leaks from infrastructure. Methane’s effects are significant due to its high potency as a greenhouse gas; it traps heat more effectively than carbon dioxide over short periods, accelerating global warming and climate change. Additionally, methane contributes to the formation of ground-level ozone, a pollutant that can cause respiratory issues in humans and harm vegetation. In concentrated areas, methane poses explosion risks, especially in mining or waste disposal sites.

Water Vapor
Water vapor primarily comes from natural processes, with evaporation from oceans, lakes, rivers, and soil being the dominant source. Plant transpiration also adds substantial water vapor to the atmosphere. Human activities have a minor direct influence, though activities like irrigation, power plant cooling, and combustion processes release small amounts. The effects of water vapor are integral to Earth’s climate dynamics. As the most abundant greenhouse gas, it plays a key role in the greenhouse effect by absorbing and re-emitting heat. Water vapor amplifies temperature changes through feedback loops; for instance, warming increases evaporation, leading to more water vapor that further traps heat, intensifying weather patterns such as heavy rainfall and storms. Conversely, water vapor forms clouds, which can reflect sunlight for a cooling effect or trap heat for warming, depending on cloud type and altitude. Overall, water vapor is a natural regulator of climate, but its interactions with human-induced greenhouse gases can exacerbate climate variability.

Question 4. 

State the ways of reducing the presence of greenhouse gases.

Ans:

A major approach involves shifting our energy and transportation systems away from fossil fuels. This means significantly increasing the use of renewable energy sources like solar, wind, and hydropower to generate electricity. For transportation, opting for electric vehicles, improving public transit, and promoting walking or cycling can drastically cut emissions from petrol and diesel. Furthermore, enhancing energy efficiency is a powerful tool—using LED lighting, energy-efficient appliances, and properly insulating buildings reduces overall energy demand and the need for fossil fuel power.

Another critical strategy focuses on protecting and restoring the natural systems that absorb carbon dioxide. Halting deforestation and actively engaging in reforestation and afforestation (planting new forests) are essential, as trees act as vital carbon sinks. In agriculture, practices like reducing food waste, adopting farming techniques that preserve soil health, and managing livestock manure to capture methane can lower emissions from this sector. On an industrial level, investing in carbon capture and storage (CCS) technologies can trap emissions at their source, such as from factories or power plants, before they enter the atmosphere.

Finally, addressing waste and making sustainable consumer choices play a vital role. Reducing the amount of waste sent to landfills, which produce methane, through better recycling, composting, and waste-to-energy programs is important. On a personal level, individuals can contribute by adopting a diet with less meat, especially red meat, choosing products with minimal packaging, and supporting companies with strong environmental policies. Collectively, these actions across energy, land use, industry, and daily life are necessary to lower greenhouse gas concentrations and mitigate climate change.

Question 5. 

State the effects of greenhouse gases on the atmosphere.

Ans:

Greenhouse gases, such as carbon dioxide, methane, and nitrous oxide, act like a thermal blanket wrapped around the Earth. Normally, this blanket is beneficial, as it traps just enough of the sun’s heat to keep our planet at a habitable temperature. However, human activities, primarily the burning of fossil fuels, deforestation, and industrial processes, have drastically thickened this blanket by increasing the concentration of these gases in the atmosphere. The most direct effect of this is global warming—a steady increase in the Earth’s average surface temperature.

This excess heat does not simply make summers hotter; it fundamentally disrupts global climate patterns. One major consequence is more extreme and unpredictable weather, including intense heatwaves, prolonged droughts, severe storms, and heavier rainfall leading to floods. Furthermore, the warming atmosphere causes the rapid melting of glaciers and polar ice caps, which contributes to rising sea levels. This threatens coastal communities and ecosystems with increased flooding and erosion. Another critical effect is the acidification of oceans, as excess carbon dioxide dissolves in seawater, harming marine life like corals and shellfish.

Beyond these immediate changes, the altered atmosphere disrupts delicate ecological balances. Shifting climate zones affect agriculture, leading to crop failures and food insecurity in vulnerable regions. Habitats for many plant and animal species change faster than they can adapt, increasing the risk of extinction. In essence, the thickening blanket of greenhouse gases pushes the entire planetary system out of equilibrium, with wide-ranging and often interconnected impacts on our weather, geography, and the natural systems that support all life.

Question 6. 

State the role of a greenhouse in growing plants.

Ans:

In plant growing, a greenhouse acts like a sheltered space that tweaks the natural environment to favor cultivation. By letting sunlight in while trapping heat, it keeps temperatures steady and warm, which is ideal for plants that might struggle outdoors in chillier weather. It also buffers against harsh conditions like strong winds, heavy rain, or frost, and helps keep pests and diseases at bay. Inside, growers can fine-tune humidity, watering, and feeding schedules, giving plants a consistent setting to grow stronger and longer. Essentially, it stretches the growing season and offers more control over how plants develop, regardless of what’s happening outside.

Question 7. 

Our atmosphere acts as a greenhouse. Explain.

Ans:

Imagine Earth surrounded by a protective layer, much like a blanket. This layer is our atmosphere, and it functions similarly to a greenhouse. You might have seen a greenhouse where sunlight enters through glass, warming the plants inside, but the heat is trapped, keeping the interior warm. Our atmosphere operates on a comparable principle.

Sunlight travels through space and reaches Earth as shortwave radiation. This energy passes through the atmosphere with ease, heating the planet’s surface—the land, oceans, and everything on them. Once warmed, the surface releases this energy back toward space as infrared radiation, which is essentially heat with a longer wavelength.

However, the atmosphere isn’t entirely open to letting this heat escape. It contains specific gases, known as greenhouse gases, such as carbon dioxide, methane, and water vapor. These gases have a unique property: they absorb infrared radiation. When they do, they become energized and re-radiate the heat in all directions, including back toward Earth’s surface. This process effectively traps heat, preventing it from vanishing into space, much like the glass panels of a greenhouse retain warmth.

Without this natural greenhouse effect, Earth would be frigid and inhospitable. The average global temperature would plummet to around -18°C (0°F), rather than the mild 15°C (59°F) that supports life. So, this atmospheric mechanism is crucial for maintaining a stable climate.

Yet, human activities have intensified this effect. Burning fossil fuels, cutting down forests, and industrial processes have increased the concentration of greenhouse gases. This adds to the atmosphere’s heat-trapping ability, leading to extra warming—often called global warming. It’s akin to thickening that cozy blanket until it becomes too warm.

Question 8. 

How can we reduce global warming?

Ans:

Global warming, driven by the buildup of greenhouse gases like carbon dioxide and methane in our atmosphere, presents a serious challenge. However, it is a problem with solutions that require action at every level, from international policy down to individual daily choices. A comprehensive response hinges on a fundamental shift in how we produce and consume energy. This means rapidly transitioning away from fossil fuels—coal, oil, and natural gas—and toward clean, renewable sources like solar, wind, and hydropower. Simultaneously, improving energy efficiency in everything from industrial manufacturing and power grids to our home appliances and vehicles can drastically reduce demand. On a larger scale, protecting and restoring forests, which act as crucial carbon sinks, and innovating in sustainable agriculture to reduce methane emissions are equally vital systemic changes.

Individual and community actions are powerful forces that drive broader change. One of the most significant personal choices is rethinking transportation: opting for walking, cycling, public transit, or electric vehicles directly cuts tailpipe emissions. At home, reducing energy consumption by using efficient lighting and appliances, improving insulation, and supporting green energy programs makes a difference. Modifying our diets to include more plant-based foods and reducing food waste lowers the carbon footprint associated with meat production and landfills. Furthermore, embracing a “reduce, reuse, recycle” mentality minimizes the energy-intensive cycle of manufacturing new products. Collectively, these choices signal market demand for sustainable practices and cultivate a culture of conservation.

Ultimately, lasting progress requires engaged citizenship and advocacy. Individual efforts must be amplified by supporting businesses and policies committed to a low-carbon future. This can involve voting for leaders who prioritize climate action, supporting companies with transparent sustainability goals, and participating in local community initiatives like tree-planting drives or conservation projects. Education is also key; by staying informed and discussing solutions with others, we build public will for the necessary large-scale investments and innovations. While the challenge is global, the path forward is built through a combination of smart technology, conscious consumption, and sustained political will, proving that a stable climate is achievable through deliberate and collective effort.

Exercise 8 (D)

Question 1. 

What is a pollutant?

Ans:

A pollutant is any substance or form of energy that, when introduced into the environment at a concentration higher than natural levels, causes undesirable or harmful effects. These effects can damage the health of humans, other living organisms, or the wider ecosystem, and can also cause deterioration of property or amenities. The key idea is that a substance becomes a pollutant not necessarily because of what it is, but because of where it is, how much of it is present, and its negative impact. For instance, even natural substances like plant nutrients can act as pollutants if they enter a river in excessive amounts, leading to algal blooms that suffocate aquatic life.

Pollutants can be physical, chemical, or biological agents. Common examples include toxic gases like carbon monoxide from vehicles, industrial chemicals like pesticides, heavy metals like lead, excessive nutrients like nitrates and phosphates, and even noise or heat. They originate from various sources, which are broadly classified as point sources (like a factory’s smokestack or a sewage pipe) and non-point sources (like agricultural runoff or urban stormwater). Importantly, a pollutant can be a foreign man-made compound, or it can be a naturally occurring substance, like dust or carbon dioxide, that is released in quantities or at rates that the environment cannot safely absorb or process.

The harm caused by a pollutant depends on several factors, including its chemical nature, concentration, persistence in the environment, and how readily it accumulates in living tissue. Some pollutants, like certain plastics, are physically disruptive, while others, like mercury, are poisonous and can move up the food chain. Ultimately, a pollutant disrupts the natural balance of an environment, making the air unfit to breathe, the water unsafe to drink, or the soil unable to support healthy growth. Its defining characteristic is the adverse change it forces upon a stable system.

Question 2. 

1. What is the effect of the following pollutants on living beings? Fluorides 

2. What is the effect of the following pollutants on living beings? Smoke particles 

3. What is the effect of the following pollutants on living beings? Lead 

4. What is the effect of the following pollutants on living beings? Mercury compounds 5. What is the effect of the following pollutants on living beings? Smog 

6. What is the effect of the following pollutants on living beings? Nitrogen oxide 

Ans:

1. Fluorides
Fluorides, often released from industrial processes like aluminum smelting and phosphate fertilizer production, have a dual nature. In controlled, minute quantities, they are beneficial for dental health. However, excessive intake, primarily through contaminated air, water, or food, leads to fluorosis. Dental fluorosis causes staining and pitting of tooth enamel. Chronic exposure results in skeletal fluorosis, a debilitating condition where fluoride accumulates in bones, making them excessively dense yet brittle, causing joint stiffness, pain, and increased fracture risk. In severe cases, it can lead to crippling deformities. Animals, particularly livestock grazing on contaminated vegetation, suffer similar bone and tooth damage, reduced weight, and lower milk production.

2. Smoke Particles
Smoke particles, a complex mixture of solids and liquids from combustion (e.g., wildfires, engines, coal burning), primarily affect the respiratory system. Fine and ultrafine particles can bypass the body’s natural defenses in the nose and throat, penetrating deep into the lungs’ alveoli. This causes inflammation, exacerbates asthma, and can lead to chronic bronchitis, reduced lung function, and increased susceptibility to respiratory infections. Long-term exposure is linked to lung cancer and cardiovascular problems, as the smallest particles can enter the bloodstream. For wildlife, smoke inhalation causes similar respiratory distress, while particulate deposits on soil and water can alter habitats and poison food sources.

3. Lead
Lead is a persistent and cumulative neurotoxic metal. Once absorbed, it mimics calcium and distributes to soft tissues and bones, where it can remain for decades. Its most devastating impact is on the developing nervous systems of children, causing irreversible reductions in IQ, attention deficits, learning disabilities, and behavioral problems like aggression. In adults, exposure elevates blood pressure, contributes to kidney damage, and may cause reproductive issues. Even low-level exposure is harmful. In ecosystems, lead poisoning (plumbism) is notorious in birds and scavengers, causing severe neurological damage, paralysis, and death. It also bioaccumulates in the food chain.

4. Mercury Compounds
The toxicity of mercury depends on its form. Methylmercury, the organic form created when mercury settles in water, is exceptionally dangerous due to bioaccumulation and biomagnification in aquatic food chains. Consumption of contaminated fish is the primary route for human exposure. Methylmercury is a potent neurotoxin that readily crosses the placenta and the blood-brain barrier. It impairs neurological development in fetuses and children, affecting cognitive function, memory, and motor skills. In adults, high exposure can lead to vision loss, speech impairment, and muscle weakness. Inorganic mercury salts can damage the kidneys and digestive tract. Wildlife, especially fish-eating birds and mammals, suffer from neurological disorders, reproductive failure, and death.

5. Smog
Smog, particularly ground-level ozone (photochemical smog) and particulate haze, acts as a powerful respiratory irritant. It inflames and damages lung tissues, triggering asthma attacks, coughing, and chest pain. Repeated exposure can permanently scar lung tissue, reduce function, and contribute to the development of chronic obstructive pulmonary disease (COPD). Smog also aggravates cardiovascular conditions, leading to increased hospitalizations. Ozone specifically interferes with plants’ ability to photosynthesize, stunting growth and reducing crop yields. It damages foliage, making trees more susceptible to disease and environmental stress, thereby impacting entire forest ecosystems.

6. Nitrogen Oxides
Nitrogen oxides (NOx), notably NO and NO2 from vehicle exhaust and power plants, are key players in forming smog and acid rain. Directly, nitrogen dioxide is a corrosive gas that inflames the lining of the lungs, reduces immunity to respiratory infections (like influenza), and worsens chronic lung diseases. Long-term exposure may contribute to asthma development in children. Environmentally, NOx contributes to acid deposition, which acidifies soils and freshwater bodies, harming fish and sensitive plant life. In the atmosphere, it acts as a nutrient pollutant, causing eutrophication in water bodies and disrupting the balance of nutrient-poor ecosystems like grasslands.

Question 3. 

What is air pollution? How does this pollution take place?

Ans:

Air pollution refers to the contamination of the Earth’s atmosphere by harmful substances, known as pollutants, which cause damage to living organisms and the natural environment. This occurs when the concentration of these unwanted gases, particles, or biological materials in the air reaches levels that are unsafe. These pollutants alter the air’s natural composition, leading to a range of problems from reduced visibility and unpleasant odors to serious health issues like respiratory diseases, and environmental damage such as acid rain and global warming.

This pollution takes place through a variety of human activities and natural processes. The primary human-made source is the burning of fossil fuels like coal, petroleum, and natural gas. This happens when we operate vehicles, generate electricity in power plants, and run industrial machinery, releasing massive amounts of carbon monoxide, sulfur dioxide, nitrogen oxides, and soot into the air. Industrial processes also discharge specific chemical vapors and dust directly from factories. Furthermore, agricultural practices contribute through the release of ammonia from fertilizers and methane from livestock, while the deliberate burning of waste and crop residues sends thick smoke into the atmosphere.

Volcanic eruptions can spew vast quantities of ash and toxic gases like sulfur dioxide high into the air. Wildfires, often sparked by lightning, produce dense smoke and particulate matter. Dust storms can carry fine soil particles over great distances. However, while these natural sources are significant, the overwhelming cause of the severe and persistent air pollution problems faced today is human activity. The constant and concentrated release of pollutants from our cities, industries, and farms overwhelms the atmosphere’s ability to disperse and cleanse itself, leading to the polluted conditions we experience.

Question 4. 

Name some particulate pollutants.

Ans:

Natural Sources: These include dust and soil particles lifted by wind, pollen and spores released by plants and fungi, sea salt aerosols from ocean spray, and ash or soot from natural wildfires. While these occur without human intervention, their concentrations can be dramatically increased by activities like deforestation or land clearing.

Human-Made (Anthropogenic) Sources: A significant portion of particulate pollution comes from human activity. This includes soot and black carbon from the incomplete burning of fossil fuels in vehicles, power plants, and industrial furnaces. Construction, mining, and road traffic generate large amounts of dust and concrete particles. Industrial processes also directly release metal dust (like lead or arsenic) and chemical fumes that condense into fine particles.

Secondary Particles: These are not emitted directly but form in the atmosphere through complex chemical reactions. Gaseous pollutants like sulfur dioxide and nitrogen oxides, released from burning coal and gasoline, can transform into sulfate and nitrate particles. Similarly, organic compounds from both industrial emissions and natural sources can react to form secondary organic aerosols, which make up a substantial portion of fine particulate matter in urban air.

Question 5. 

Why is cigarette-smoking harmful?

Ans:

Cigarette-smoking is harmful for a bunch of reasons, and it’s not just about the smoker—it affects others too. Let’s break it down in simple terms.

First off, when you light up a cigarette, you’re inhaling a cocktail of chemicals. We’re talking about thousands of substances, many of which are outright poisonous. The big ones include tar, which coats your lungs like soot in a chimney, and carbon monoxide, the same stuff that comes from car exhaust, which hijacks your blood’s ability to carry oxygen. Then there’s nicotine, which hooks you fast. It’s the addictive agent that keeps people coming back, even when they know it’s bad for them.

Health-wise, smoking is a major culprit behind some of the deadliest diseases. Lung cancer is the most well-known, but that’s just the tip of the iceberg. It also ravages your heart and blood vessels, upping the chances of heart attacks and strokes. Over time, it can lead to chronic bronchitis and emphysema, conditions that make breathing a daily struggle. Honestly, it’s hard to find an organ that smoking doesn’t touch—it can cause cancers in the mouth, throat, bladder, and more, and it weakens your immune system, making you prone to infections.

But here’s the kicker: secondhand smoke. If you’re around someone who smokes, you’re breathing in many of those same toxins. Kids exposed to it face higher risks of asthma, ear infections, and sudden infant death syndrome. Adults can develop heart disease or lung cancer from long-term exposure. So, it’s not just a personal choice; it impacts everyone nearby.

Beyond health, smoking hits your wallet hard. Cigarettes are expensive, and the costs add up over years. Plus, healthcare bills from smoking-related illnesses can be crushing. Socially, it can lead to stained teeth, bad breath, and a smell that clings to clothes and hair, which might affect relationships or job opportunities.

Question 6. 

What is smog? State its damaging effects.

Ans:

Smog is a type of intense air pollution that reduces visibility and has a hazy, often yellowish or brownish appearance. The term itself is a combination of the words “smoke” and “fog.” Historically, it referred to smoky fog caused by burning large amounts of coal. In modern times, it primarily describes a complex mixture of pollutants, including ground-level ozone, fine particulate matter, nitrogen oxides, volatile organic compounds, and sulfur dioxide. There are two main types: classical or industrial smog, linked to coal burning, and photochemical smog, which forms when sunlight triggers chemical reactions between vehicle and industrial emissions.

The damaging effects of smog are wide-ranging and severe. For human health, it is particularly harmful to the respiratory system, irritating the eyes, nose, and throat. It can aggravate asthma, cause chronic bronchitis, and reduce lung function. Prolonged exposure is linked to more serious conditions like heart disease, lung cancer, and increased mortality rates, especially among children, the elderly, and those with pre-existing health conditions.

Beyond health, smog has significant environmental and economic impacts. It harms vegetation by damaging plant tissues, reducing growth in forests and crops, which affects agricultural yields. The pollutants in smog also contribute to the corrosion and erosion of buildings, monuments, and historical structures. Furthermore, the thick haze drastically reduces visibility, leading to disruptions in transportation, increased accidents, and a general decline in the quality of life in affected urban areas.

Question 7. 

What do you understand by ppm?

Ans:

Parts per million (PPM) is a measurement unit for expressing minute amounts of one component within a much larger mixture. It defines a specific ratio: one part of a substance for every million parts of the total blend. This scale makes it possible to clearly communicate extremely low concentrations that would be cumbersome to describe using percentages.

To visualize it, imagine dividing a whole into one million identical segments. A concentration of 1 PPM means just one of those segments is made up of the substance in question. A practical example is dissolving 1 gram of a substance into 1,000 kilograms of water. Since 1,000 kilograms equals 1 million grams, this creates a 1 PPM solution.

This metric is indispensable across several fields due to its precision for trace levels.

Common Applications of PPM:

• Environmental and Chemical Analysis: It is fundamental for quantifying pollutants or natural minerals in air, water, and soil. Regulatory standards for safe drinking water or air quality are often defined in PPM. For instance, a water test might show 15 PPM of nitrates, or an air monitor might detect 9 PPM of carbon monoxide.
• Materials and Manufacturing: Specifications for high-purity materials frequently use PPM to denote maximum allowable impurities. A semiconductor-grade metal, for example, may require iron contamination below 10 PPM. Similarly, additives like dyes or stabilizers in plastics are often formulated at precise PPM levels.
• Agriculture and Horticulture: Fertilizer formulations and soil amendment guides often recommend nutrient concentrations in the range of PPM for precise plant feeding, particularly in hydroponic systems.
• Performance and Quality Management: In methodologies like Six Sigma, PPM is used as a metric for defect rates, standing for “defects per million opportunities,” to quantify process quality with high precision.

Beyond its scientific definition, PPM can also represent process-related terms such as “pages per minute” for printer speed or “pieces per minute” in production. The intended meaning is always derived from its context.

Question 8. 

Describe the major air pollutants. How does carbon monoxide pollute our environment?

Ans:

The air we breathe is contaminated by a variety of harmful substances, known as air pollutants, which arise from both natural events and human activities. Sulfur oxides (SOx), primarily from burning fossil fuels like coal, and nitrogen oxides (NOx), from vehicle engines and industrial furnaces, are gaseous pollutants that contribute to acid rain and respiratory problems. Another significant group is volatile organic compounds (VOCs), emitted from vehicles, industrial solvents, and even certain household products, which react in sunlight to form ground-level ozone—a key component of smog that damages vegetation and irritates living tissues. While not directly emitted, this ground-level ozone remains a severe secondary pollutant.

Carbon monoxide (CO) is a particularly dangerous pollutant because it is a colorless, odorless, and tasteless gas, making it impossible to detect without instruments. It is produced almost exclusively through the incomplete combustion of carbon-based fuels. The primary sources are the exhaust fumes from gasoline and diesel vehicles, emissions from industrial processes, and burning of wood or coal in poorly ventilated spaces. Unlike many pollutants that have complex chemical interactions in the atmosphere, CO’s primary threat is direct and lethal to living organisms.

The environmental pollution caused by carbon monoxide operates on two main levels. Firstly, and most critically, it poses a severe health hazard by binding with haemoglobin in red blood cells roughly 200 times more effectively than oxygen does. This forms carboxyhaemoglobin, which drastically reduces the blood’s oxygen-carrying capacity. This leads to oxygen deprivation in tissues and organs, causing symptoms from headaches and dizziness to unconsciousness and death at high concentrations. Secondly, on a broader environmental scale, CO contributes indirectly to the formation of ground-level ozone. It participates in complex atmospheric reactions with other pollutants like nitrogen oxides, which, under sunlight, catalyze the production of ozone in the lower atmosphere. Furthermore, while not a greenhouse gas like carbon dioxide, CO influences the climate by affecting the concentrations of methane and carbon dioxide in the air, as it reacts with atmospheric hydroxyl radicals that would otherwise help break down these potent warming gases. Thus, carbon monoxide pollutes by directly poisoning air-breathing life and by altering atmospheric chemistry in harmful ways.

Question 9. 

1. How do you propose to control: Carbon monoxide emission 

2. How do you propose to control: SOx emission

Ans:

Controlling Carbon Monoxide Emissions

Carbon monoxide mainly comes from burning fuels like gasoline, wood, or coal without enough oxygen. To keep these emissions in check, the focus is on making sure fuel burns completely. In vehicles, this involves tuning engines to keep the air-fuel mix balanced and using catalytic converters, which change carbon monoxide into less harmful carbon dioxide. For factories or power plants, maintaining equipment regularly to avoid leaks and ensuring efficient combustion through proper air supply helps. Switching to cleaner fuels, such as natural gas, or using electric systems where possible also cuts down carbon monoxide. In homes, making sure heaters and stoves are well-ventilated and serviced reduces risks. Overall, it’s about optimizing combustion and using technology to clean up exhaust.

Controlling SOx Emissions

Sulfur oxides, or SOx, are created when fuels containing sulfur, like coal or heavy oil, are burned. To control these, one approach is to prevent sulfur from being released in the first place by using low-sulfur fuels or alternatives like natural gas. In industries, flue gas desulfurization—often called scrubbers—is common; these systems use materials like limestone to trap sulfur from exhaust gases before they reach the air. Another method is to wash coal before use to remove some sulfur. In refineries, sulfur recovery units capture sulfur from oil processing. Additionally, promoting renewable energy sources like wind or solar reduces reliance on sulfur-containing fuels. Regular monitoring and strict emission standards help enforce these practices, keeping SOx levels down.

Question 10. 

Give the composition, causes, and effects of acid rain.

Ans:

Acid rain refers to the precipitation of acidic components, occurring in both wet and dry forms, that have a pH level significantly lower than normal rainwater. Its composition is primarily a mixture of sulfuric acid and nitric acid. These strong acids are formed in the atmosphere through complex chemical reactions when primary pollutants—namely sulfur dioxide and nitrogen oxides—are released from various sources. These compounds react with water vapor, oxygen, and other chemicals to produce acidic compounds, which then fall to the earth dissolved in rain, snow, fog, or as dry particles and gases.

The primary causes of acid rain are human activities that burn large quantities of fossil fuels. The major sources include power generation plants that use coal or oil, industrial factories and refineries, and motor vehicle exhaust. These processes emit vast amounts of sulfur dioxide and nitrogen oxides into the air. While natural phenomena like volcanic eruptions, forest fires, and bacterial decomposition can also release these gases, human industrial activity is overwhelmingly responsible for the problematic levels leading to acid rain. The pollutants can travel hundreds of miles in the wind before deposition, meaning the effects are often felt far from the original source.

The effects of acid rain are widespread and damaging to both natural ecosystems and human-made structures. In aquatic environments, it acidifies lakes and streams, making the water toxic to fish, amphibians, and aquatic insects by leaching aluminum from the soil into the water. On land, it damages forests by leaching essential nutrients like calcium and magnesium from the soil while releasing harmful aluminum, weakening trees and making them vulnerable to disease and extreme weather. It also directly harms foliage. For human infrastructure, acid rain accelerates the corrosion of buildings, monuments, bridges, and statues, especially those made of limestone and marble. Furthermore, the particulate pollution that causes acid rain can contribute to serious human respiratory illnesses such as asthma and bronchitis, impacting public health.

Question 11. 

Explain the effect of sulphur dioxide on the atmosphere.

Ans:

Sulphur dioxide, a gas recognized by its pungent smell, enters the air through natural events like volcanic eruptions and human actions such as burning coal or oil. Once released, it sets off a chain of reactions that alter atmospheric conditions in several ways.

One of the most noted effects is its contribution to acid rain. In the atmosphere, sulphur dioxide combines with oxygen and water vapor, gradually transforming into sulphuric acid. This acid later falls as rain or other precipitation, which can acidify lakes and streams, harm forests, and corrode buildings and monuments.

Beyond acid rain, sulphur dioxide plays a key role in forming fine particles known as sulphate aerosols. These tiny particles scatter sunlight, often reducing visibility and creating hazy conditions. While they can linger in the air and pose breathing difficulties for humans, they also influence climate patterns. By reflecting sunlight back into space, sulphate aerosols have a temporary cooling effect on the Earth’s surface, somewhat counteracting global warming. This was notably observed after large volcanic injections, like the 1991 Mount Pinatubo eruption, which led to a measurable drop in global temperatures.

Although not a major ozone-depleting gas, sulphur dioxide can indirectly affect the ozone layer. When volcanic plumes send it high into the stratosphere, the resulting sulphate particles may foster chemical reactions that subtly impact ozone concentrations, though this is less consistent than other effects.

Question 12. 

Explain the formation of ozone in the atmosphere.

Ans:

Ozone, a special molecule made of three oxygen atoms, forms naturally in a specific layer of our atmosphere called the stratosphere, roughly 10 to 50 kilometers above the Earth’s surface. This formation is a continuous cycle powered by the sun’s powerful ultraviolet (UV) radiation. The process begins when a high-energy UV ray strikes a normal oxygen molecule (O₂), splitting it apart into two separate, highly reactive oxygen atoms.

These free oxygen atoms do not remain alone for long. Each one quickly collides with another intact oxygen molecule (O₂) in the dense air. When they combine, they form a new, three-atom molecule known as ozone (O₃). This newly formed ozone molecule is crucial because it acts as a protective shield. It absorbs harmful medium-energy UV radiation from the sun. Interestingly, this very absorption breaks the ozone molecule apart again, recycling it back into an oxygen molecule and a free atom, which can then restart the formation cycle. This constant, dynamic process of creation and destruction results in a stable but fragile layer that filters out the sun’s most dangerous rays, making life on land possible.

Question 13. 

What is the function of ozone in the atmosphere?

Ans:

Ozone in the atmosphere acts like a natural barrier against the sun’s more intense rays. Most of it sits in a region called the stratosphere, where it forms what’s commonly known as the ozone layer. This layer soaks up a significant portion of the sun’s ultraviolet radiation, especially the kinds that are most damaging—UV-B and UV-C. Without this absorption, these rays would reach the ground in much higher doses, leading to increased risks like skin cancer and eye cataracts in people. They could also stunt plant growth and harm plankton in the oceans, which are foundational to marine food chains. So, in simple terms, ozone works as Earth’s built-in sunscreen, making the planet safer for living things. That’s why scientists pay close attention to threats like ozone depletion, which can weaken this critical layer.

Question 14. 

State the chemicals responsible for ozone layer destruction.

Ans:

The primary chemicals responsible for the destruction of the Earth’s ozone layer are man-made compounds known as ozone-depleting substances (ODS). The most notorious among these are chlorofluorocarbons (CFCs), which were historically used as refrigerants, propellants in aerosol sprays, and in foam-blowing agents. Other significant contributors include halons (used in fire extinguishers), carbon tetrachloride (a solvent), and methyl chloroform (an industrial cleaning agent). A naturally occurring but industrially amplified compound, methyl bromide, a pesticide, is also a potent ozone-depleter.

These chemicals are uniquely destructive due to their remarkable stability. They do not break down in the lower atmosphere and instead drift intact up to the stratosphere. There, intense ultraviolet (UV) radiation splits them apart, releasing highly reactive atoms of chlorine (Cl) and bromine (Br). It is these free chlorine and bromine atoms that directly attack ozone molecules (O₃). A single chlorine atom can catalyze the destruction of tens of thousands of ozone molecules before it is eventually deactivated, making the process extremely efficient and damaging.

While CFCs and halons are the most potent, the search for replacements led to the introduction of hydrochlorofluorocarbons (HCFCs). Although HCFCs have a significantly lower ozone-depletion potential because they contain hydrogen and break down more easily in the lower atmosphere, they still release some chlorine and therefore contribute to ozone loss. Consequently, they are classified as transitional substitutes and are also being phased out under global agreements like the Montreal Protocol.

Question 15. 

1. Name any two: Natural sources of atmospheric pollution.

2. Name any two: Gases that are responsible for the formation of acid rain. 

Ans:

1. Natural sources of atmospheric pollution include volcanic eruptions, which release ash, sulfur dioxide, and other particulates, and wildfires, which emit smoke, carbon monoxide, and fine particles.
2. Gases responsible for the formation of acid rain are sulfur dioxide (SO₂) and nitrogen oxides (NOₓ), which react with atmospheric water vapor to form sulfuric and nitric acids.

Question 16. 

Explain the term ‘global warming’. State two ways by which global warming can be reduced.

Ans:

Global warming describes the gradual increase in the Earth’s overall surface temperature, a trend that has become the defining challenge of our time. This change is rooted in the intensification of the natural greenhouse effect. Human industry, particularly our reliance on burning coal, oil, and gas for power and transport, releases vast amounts of gases like carbon dioxide into the air. Activities such as clearing forests for agriculture or development further worsen the problem, as fewer trees are left to absorb these emissions. The result is a thicker atmospheric blanket that traps more of the sun’s heat, destabilizing long-standing climate systems and leading to consequences like more extreme weather, melting ice caps, and rising sea levels.

To counter this crisis, a decisive move toward clean energy is one of the most powerful strategies available. Phasing out the use of fossil fuels by embracing renewable alternatives—such as harnessing energy from the sun, wind, and water—directly tackles the primary source of carbon emissions. This shift not only involves large-scale infrastructure projects but also personal choices, like opting for electric vehicles or solar-powered homes, collectively reducing the volume of heat-trapping gases we produce.

Equally important is a committed global effort to preserve and restore our planet’s forests. Trees play a critical role in the climate system by naturally capturing and storing carbon dioxide as they grow. Therefore, ending widespread deforestation and actively supporting initiatives to plant trees on degraded land or create new forest areas are vital actions. These measures strengthen the Earth’s inherent capacity to rebalance atmospheric carbon, offering a natural and effective buffer against the relentless pace of warming.

Question 17. 

State two effects of ozone depletion.

Ans:

The reduction in atmospheric ozone allows a higher intensity of ultraviolet radiation to reach the Earth’s surface. This leads to a heightened prevalence of skin malignancies and eye conditions, such as cataracts, in humans. Additionally, it disrupts biological processes in both land and marine environments, causing stunted growth in many plant species and impairing the development of young aquatic organisms.

Question 18. 

What is the cause of acid rain? Give any two impacts of acid rain.

Ans:

Acid rain happens when gases like sulfur dioxide and nitrogen oxides get released into the air. These mainly come from human activities such as burning fossil fuels in power plants, industrial operations, and vehicles. Once in the atmosphere, these gases react with water, oxygen, and other substances to form acidic compounds, which then fall back to earth in rain, snow, or fog.

Two significant impacts of acid rain are:

1. Harm to water bodies: It acidifies lakes and rivers, making the water too acidic for many aquatic organisms. This can kill fish, insects, and other life, disrupting entire aquatic ecosystems.
2. Damage to vegetation and soil: Acid rain strips essential nutrients from soil and releases toxic aluminum, weakening trees and plants. It also directly damages leaves and bark, leading to forest decline and reduced crop yields.

Question 19. 

Explain the methods of preventing acid rain.

Ans:

Preventing acid rain requires a multi-pronged strategy targeting its primary sources: the emissions of sulfur dioxide (SO₂) and nitrogen oxides (NOx) from human activities. The most effective approach is to reduce these pollutants at their origin before they enter the atmosphere. For large industrial plants and power stations, especially those burning coal, this involves installing engineering solutions like “scrubbers” in smokestacks. These scrubbers use a chemical reaction, often with a limestone slurry, to capture sulfur compounds before the exhaust is released. Similarly, adopting cleaner combustion technologies, such as fluidized bed combustion, and shifting industrial fuel sources from high-sulfur coal to natural gas or renewable energy dramatically cuts emissions at the source.

Addressing pollution from vehicles, a major contributor of nitrogen oxides, is another critical front. This can be achieved by mandating the use of catalytic converters in all automobiles, which convert harmful NOx into less damaging nitrogen gas. Governments can enforce stricter emission standards for engines and promote a transition to electric vehicles, which produce zero tailpipe emissions. On a societal level, reducing overall fossil fuel consumption by improving public transportation, encouraging carpooling, and enhancing energy efficiency in homes and industries also plays a vital role in lowering the total volume of pollutants produced.

Finally, prevention extends beyond technology to include policy and personal responsibility. International agreements and national regulations that set mandatory emission caps have proven successful, such as the Acid Rain Program in the United States. Supporting and complying with such environmental policies is essential. On an individual level, conserving electricity, choosing energy-efficient appliances, and opting for cleaner transportation alternatives collectively reduce the demand for the fossil fuels that cause acid rain. Ultimately, a sustained commitment to renewable energy sources like solar, wind, and hydropower represents the most fundamental long-term solution, as they generate power without the associated harmful emissions.

Question 20. 

State an advantage of CNG (Compressed Natural Gas).

Ans:

One practical plus of using CNG is that it tends to be easier on engine components over time, leading to lower maintenance costs and longer engine life compared to traditional fuels.

Question 21. 

State how CFC breaks the ozone layer.

Ans:

Chlorofluorocarbons (CFCs) are synthetic compounds once widely used in cooling systems, aerosol sprays, and foam products. Due to their stability, they do not break down easily in the lower atmosphere. Over time, they drift upward into the stratosphere, where they encounter intense ultraviolet (UV) radiation from the sun.

This UV radiation causes CFC molecules to break apart, releasing chlorine atoms. These chlorine atoms initiate a chain reaction that damages the ozone layer. Specifically, a chlorine atom reacts with an ozone molecule (O₃), converting it into oxygen (O₂) and forming chlorine monoxide (ClO). The chlorine monoxide then reacts with another ozone atom, regenerating the chlorine atom while producing more oxygen.

The chlorine atom is not consumed in this process; it acts as a catalyst, meaning it can repeat this cycle thousands of times. This continuous reaction significantly depletes ozone molecules, thinning the ozone layer. As a result, harmful UV radiation penetrates the Earth’s atmosphere more easily, increasing risks to human health and ecosystems.

Question 22. 

Describe the methods of saving the ozone layer.

Ans:

The single most important action is the strict global enforcement and future strengthening of the Montreal Protocol. This international treaty, agreed upon in 1987, successfully mandated the phase-out of the primary culprits: chlorofluorocarbons (CFCs) and halons, commonly found in old refrigerators, air conditioners, aerosol sprays, and fire extinguishers. Continued vigilance is required to prevent the illegal trade of these banned substances and to responsibly destroy existing stockpiles. Furthermore, the protocol must adapt to address newer, less damaging but still problematic chemicals that have been used as replacements, such as hydrochlorofluorocarbons (HCFCs), ensuring they too are phased out on schedule in favor of truly ozone-safe alternatives.

At a national and industrial level, supporting and adopting green technologies is crucial. This means consumers should choose products labeled “ozone-friendly” or “CFC-free,” particularly for cooling and refrigeration. Industries must invest in and transition to natural refrigerants like ammonia, hydrocarbons, or carbon dioxide in their manufacturing processes. Proper maintenance and professional disposal of old air-conditioning units and refrigerators are essential to prevent the release of their trapped ozone-depleting chemicals. Governments can support this by funding research into safe alternatives and providing incentives for companies that develop and use environmentally benign technologies.

Finally, individual awareness and responsible choices play a supporting role. Using public transport, carpooling, or driving less reduces nitrogen oxide emissions, which can also harm the ozone layer. Educating others about the success of the Montreal Protocol demonstrates how global cooperation can solve environmental crises, building public will for continued action. Ultimately, saving the ozone layer is a ongoing task of global partnership, requiring persistent policy, innovative technology, and informed citizenship to ensure this critical shield fully recovers for future generations.

Question 23. 

1. Fill in the blank: The pollutants such as NO2, SO2, and SO3 dissolved in the moisture of air are the cause of ____________. 

2. Fill in the blank: Excessive release of carbon dioxide in the atmosphere is the cause of __________ effect which produces global warming. 

3. Fill in the blank: The ozone layer prevents the harmful ________ radiation of the sun from reaching the earth. 

4. Fill in the blank: The decrease in the concentration of ozone in the stratosphere is the cause of the formation of __________ holes. 

5. Fill in the blank: Ozone depletion is mainly caused by the active __________ atoms generated from CFC in the presence of UV radiation. 

Ans:

1. The pollutants such as NO₂, SO₂, and SO₃ dissolved in the moisture of air are the cause of acid rain.
2. Excessive release of carbon dioxide in the atmosphere is the cause of the greenhouse effect which produces global warming.
3. The ozone layer prevents the harmful ultraviolet (UV) radiation of the sun from reaching the earth.
4. The decrease in the concentration of ozone in the stratosphere is the cause of the formation of ozone holes.
5. Ozone depletion is mainly caused by the active chlorine atoms generated from CFC in the presence of UV radiation.

Question 24. 

1. Select the correct answer: Excessive release of carbon dioxide in the atmosphere is the cause of

1. Depletion of ozone
2. formation of polar vertex
3. global warming
4. formation of smog 

2. Select the correct answer: Inhalation of air polluted with carbon monoxide is dangerous because:

1. CO combines with O2 dissolved in the blood.
2. CO combines with hemoglobin of blood.
3. CO removes water from the body and causes dehydration.
4. CO causes coagulation of proteins in the body

3. Select the correct answer: A decrease in the amount of ozone in the stratosphere is called depletion of the zone and it is caused by

1. UV radiations of sun
2. Use of CFC compounds
3. excessive use of detergents
4. Use of polychlorinated biphenyls