Unit 14: Atmosphere — Short Questions

Naturally occurring particulate matter (PM) include dust from earth's surface, and biological materials in the form of pollens, spores and animal debris.

• Volcanic eruptions can introduce very large quantities of gases and particulate matter (PM) into the atmosphere.

• Thunderbolt produces significant quantities of oxides of nitrogen (NOₓ).

• Other natural sources of air pollution are algae on the surface of the oceans, which gives out hydrogen sulfide (H₂S), wind erosion which introduces PM (particulate matter).

• Humid zones such as swamps, peat-bags or little deep lakes, which produce methane (CH₄).

Deforestation is purposeful cleaning or thinning of forests by humans. Forests absorb Green House Gases (GHGs) like CO₂ and clean air for us. So deforestation deteriorate the air quality. Deforestation has a wide range of negative impact on the environment, including loss of biodiversity, climate change, soil degradation and water cycle disruption.

Troposphere
In the troposphere temperature decreases with increases moving upwards in altitude this is because of decrees in concentration of atmospheric gases responsible of temperature maintenance on earth. It's range is from 17°C to -58°C.

Stratosphere
When we move up in the stratosphere temperature increase with the increase of altitude this is because of presence of ozone layer as ozone formation is an exothermic reaction. It's range is -58°C to -2°C.

Activity | Pollutant released

• Power stations | Sulfur dioxide
• Automobiles | Nitrogen dioxide
• Livestock and cattle | Ammonia
• Metallurgy | Heavy metals

Persistent Organic Pollutants (POPs) These are organic compounds that are resistant to degradation through chemical, biological and photolytic processes. These are toxic and adversely affect human health and the environment, traveled by wind and water.

Most POPs are generated in one country can affect people and wildlife far from where they are used and released. Owing to their persistence, they accumulate in the environment

Effects POPs can have significant adverse effects on human health.

Examples Polychlorinated Biphenyls (PCBs), Dichlorodiphenyl tri-chloroethane (DDT).

Polycyclic Aromatic Hydrocarbon (PAHs)
Polycyclic aromatic hydrocarbon (PAHs), composed of fused multiple aromatic rings are common environmental pollutants.

Effects on health They have potential toxicity and carcinogenic properties.

Examples Naphthalene, anthracene and phenanthrene.

Photochemical smog Photochemical smog is a type in which primary air pollutants like nitrogen oxides (NOₓ), VOCs and unburned hydrocarbons undergo photochemical reactions in the presence of sunlight and form secondary pollutants like ozone and peroxyacetyl nitrates (PAN).

Conditions Presence of sunlight, presence volatile organic compounds, presence of oxides of nitrogen and less movement of wind.

AQI systems provide data about presence and concentration of different air pollutants. These pollutants can include particulates matter (PM), nitrogen dioxides (NO₂), sulfur dioxide (SO₂), carbon monoxide (CO), ozone (O₃) and volatile compounds (VOCs). This data can be further used to for policies and make laws to reduce pollution.

PM₁₀ and PM₂.₅ refers to the size of particulate matter while PM₂.₅ is 2.5micrometer or less while PM₁₀ is 10 micrometer or less PM₂.₅ is considered more harmful due to its small size which allows these particles to penetrate deep inside the human respiratory system without being hindered by natural protective mechanisms.

Chemical reaction The most important chemical reactions are following:

2SO₂ + O₂ → 2SO₃
SO₃ + H₂O(l) → H₂SO₄(aq)

SO₂ from fossil fuels is oxidized to SO₃ which then reacts with water to form sulphuric acid.

2NO + O₂ → 2NO₂
3NO₂(g) + H₂O(l) → 2HNO₃(aq) + NO(aq)

Nitrogen oxide reacts with water to produce nitric acid and nitrous acid.

Specific measures to control smog particularly during the winter months when air quality deteriorates significantly. Restrictions the burning of crop residues, which is a major contributes to smog, use smog towers and technologies to reduce particulates matter in the air.

Oxides of nitrogen and other undesirable gases such as CO and various unburnt hydrocarbon are emitted by the vehicle engines. The most cars are equipped with catalytic converters to convert the harmful pollutants to harmless substances. CO is oxidized to CO₂, NOₓ are reduced to N₂. The unburnt hydrocarbon is converted to CO₂ and H₂O.

Heavy metal like lead, mercury and cadmium can indeed be significant air pollutants. They are released into the atmosphere from various industrial process, transportation and other human activities.

Major sources Metallurgy, battery waste and incineration.

The troposphere is the lowest layer of the atmosphere, extending up to about 8-16 km. It contains most of the atmospheric mass and almost all water vapour. Weather phenomena like clouds, rain, and storms occur here. Temperature decreases with altitude in this layer.

The stratosphere lies above the troposphere, up to about 50 km altitude. It contains the ozone layer, which absorbs harmful ultraviolet radiation. Unlike the troposphere, its temperature increases with height due to UV absorption. This layer is important for protecting life from UV damage.

The mesosphere extends from about 50 km to 80 km above the Earth. It is the coldest layer of the atmosphere, with temperatures dropping to -90°C. Most meteoroids burn up here due to atmospheric friction. The boundary at its top is called the mesosphere.

The exosphere is the outermost layer of the atmosphere, extending from about 500 km to thousands of kilometers. Air is extremely thin here and molecules can escape into space. It mainly contains hydrogen and helium atoms. This layer gradually merges with outer space.

Dry air is composed mainly of nitrogen (78%) and oxygen (21%), with argon (0.93%) as the next most abundant gas. Carbon dioxide makes up about 0.04%. Trace gases like neon, helium, methane, and ozone are present in smaller amounts.

Nitrogen is inert and makes up the largest portion of the atmosphere. It dilutes oxygen, preventing rapid combustion. It is also essential for living organisms as it is a key element in amino acids and proteins, entering the food chain through nitrogen fixation.

Water vapour is important for cloud formation and precipitation. It absorbs heat and contributes to the greenhouse effect. It plays a key role in the Earth's energy balance and weather systems. Its amount varies with temperature and location.

Primary pollutants are emitted directly into the atmosphere from sources like vehicles, industries, and natural processes. Examples include CO, SO₂, NO, and particulate matter. They can harm human health and the environment directly.

Chlorofluorocarbons are used as propellants for aerosols and as coolant in refrigerators and air conditions. CFCs are 100,000 times more effective than CO₂ at preventing heat from escaping from the Earth's atmosphere. The decomposition of one molecule of CFC's can destroy up to 100,000 molecules of ozone.

CFCl₃ + UV → CFCl₂ + Cl•
Cl• + O₃ → Cl•O + O₂
Cl•O + O → Cl• + O₂

Secondary pollutants are not emitted directly; they form in the atmosphere by chemical reactions of primary pollutants. Examples include ground-level ozone and peroxyacetyl nitrates (PANs). Sunlight often drives these reactions, as in photochemical smog.

Human-made sources include vehicle exhaust, industrial emissions, burning of fossil fuels, and agricultural activities. These release pollutants like CO₂, NOₓ, SO₂, and particulates into the atmosphere. They are major contributors to urban smog and climate change.

Particular matter (PM) consists of tiny particles suspended in the air, including dust, dirt, soot and smoke ranging from diameter of 2.5 micrometer to 10.0 micrometer. Inhalation of these particulate matter (PM) can cause inflammation and irritation of airways, leading to conditions such as asthma and bronchitis.

The short-term exposures of NO₂ and SO₂ can irritate the respiratory system, long term exposure increase the risk of respiratory infection, asthma and bronchitis.

Chlorofluorocarbons are used as propellants for aerosols and as coolant in refrigerators and air conditions. CFCs are 100,000 times more effective than CO₂ at preventing heat from escaping from the earth's atmosphere. The decomposition of one molecule of CFCs can destroy up to 100,000 molecules of ozone.

Anthropogenic activities are human-made actions or processes that affect the natural environment. The term comes from "Anthropos" (Human) and "genic" (produced by). These activities can have positive or negative impacts on ecosystems, climate and the Earth's resources.

Dry deposition Direct deposition is transfer of pollutants from air to surface of earth directly by absorbing into gravity or wind.

Wet deposition Wet deposition refers to transfer of pollutants to land via absorbing into precipitation.

Carbon monoxide is a colourless, odourless gas produced by incomplete combustion of carbon fuels. It binds to haemoglobin more strongly than oxygen, reducing oxygen transport in the body. High exposure can cause death.

CO emissions can be reduced by improving combustion efficiency, using catalytic converters in vehicles, ensuring proper ventilation for gas appliances, and shifting to cleaner fuels. Public awareness is also important.

Carbon monoxide is highly poisonous gas and cause suffocation if inhale. It binds blood hemoglobin more strongly than oxygen thus excluding oxygen from normal respiration. The CO poisonous can be reversed by giving high pressure oxygen.

Nitrogen oxides include NO and NO₂, produced mainly during high-temperature combustion. They are important air pollutants contributing to smog and acid rain. Natural sources include lightning and soil bacteria.

NO₂ irritates the respiratory system, reducing lung function and aggravating asthma. Long-term exposure can lead to chronic respiratory diseases. It also contributes to the formation of ground-level ozone.

The main human source is combustion in vehicles, power plants, and industries. High temperatures cause nitrogen and oxygen in air to react, producing NO and NO₂.

Because reaction of oxygen and nitrogen requires large amount of energy ordinarily not available in atmosphere.

N₂(g) + O₂(g) → 2NO(g) (high temperature)
2NO(g) + O₂ → 2NO₂ (Nitrogen-Dioxide)

Emissions can be controlled by catalytic converters in vehicles, using low-NOₓ burners, and switching to cleaner energy sources. Regulations and fuel quality improvements also help.

Ozone depletion is mainly caused by chlorofluorocarbons (CFCs) and other halogenated compounds. These release chlorine and bromine atoms in the stratosphere, which destroy ozone molecules.

Ozone depletion increases UV radiation reaching Earth, causing skin cancer, cataracts, and immune suppression. It also harms crops and marine life, especially phytoplankton.

Ground-level ozone is a secondary pollutant formed from NOₓ and VOCs in sunlight. It irritates the lungs, reduces crop yields, and damages materials like rubber.

It can be reduced by phasing out ozone-depleting substances under agreements like the Montreal Protocol. Using alternatives to CFCs and improving refrigeration technology are important measures.

The layer where the maximum concentration of ozone is present is called ozone layer. It is present in the 2nd layer of atmosphere that is "Stratosphere".

The region where the ozone layer depletes called ozone hole. Especially over the Antarctic region during the southern Hemisphere's spring (August to October).

Acid rain is rain with pH below normal (less than 5.6) due to dissolved acids like H₂SO₄ and HNO₃. It results from SO₂ and NOₓ emissions reacting with water in the atmosphere.

Acid rain lowers the pH of lakes and rivers, harming fish and other aquatic organisms. Many species cannot survive in acidic water, leading to reduced biodiversity.

Controlling acid rain requires reducing SO₂ and NOₓ emissions using scrubbers, catalytic converters, and cleaner fuels. International cooperation is essential since pollutants can travel long distances.

Photochemical smog forms when sunlight drives reactions between NOₓ and VOCs, producing ozone and PANs. It is common in sunny cities with heavy traffic.

Industrial smog forms from burning coal and oil in cool, humid conditions. It contains SO₂, soot, and water droplets, giving it a grey colour. It was historically common in cities like London.

The AQI is a scale that indicates how polluted the air is and the associated health risks. It is calculated using concentrations of pollutants like PM of size 2.5μm and PM of size 10 μm, SO₂, NO₂, CO, and O₃.

Children under 18, adult over 65, people with chronic heart and lung diseases are under high-risk, as they are more vulnerable to harmful effects of air pollution. Outdoor workers are at higher risk because of the prolonged exposure.

Following hypothesis will be made "the concentration of airborne particulate matters (PM 2.5) and nitrogen dioxide (NO₂) in urban areas is higher during peak traffic hours as compared to non-peak hours".

Advantage

• Formulating a hypothesis is the first step in designing the experiment.
• This hypothesis can be tested by collecting air quality data at different time of the day.

Air pollution is not confined to borders and effective management requires international cooperation. Because polluted air of one country can affect the air quality of other countries.

Busy roads sites and residential areas should be selected for monitoring. The data on traffic volume during rush hours and non-rush hours should be collected and finally compared. The reliable instruments and methods to collect air quality data should be used.

By carefully designing experiments, collecting and analyzing data, a hypothesis about air quality can be tested and the strategies for improving air quality can be made.

Analyzing and interpreting air quality data involves understanding the concentration of various pollutants, identifying trends overtime and assessing the implications for public health and environmental policy.