Nitrogen and Oxygen Composition

Nitrogen (N₂)

• Nitrogen is a permanent gas that constitutes approximately 78% of the atmosphere.
• It serves as a vital building block for all living organisms including animals, plants, and fungi.
• Exists in forms such as free nitrogen gas (N₂), nitrogen oxides (NOₓ), and nitrogen hydrogen compounds (NH₃).
• It is non-reactive and freely available in gaseous form.
• Plants require nitrogen to be converted into nitrile, nitrate, or ammonia (NH₃) through nitrogen fixation, as they cannot directly absorb it.
• Leguminous plants such as pulses can independently fix nitrogen.
• Bacteria including Nitrosomonas, Nitrobacter, and Azotobacter aid in nitrogen fixation.
• Humans and animals acquire nitrogen through consuming plants or other animals.

Oxygen (O₂)

• Oxygen is the second most abundant gas in the atmosphere, making up approximately 20.8% to 21%.
• Highly reactive, readily forming oxides with minerals, such as iron to form rust (Iron Oxide) and aluminum to form Aluminum Oxide.
• Plays a crucial role in combustion, supporting fire.
• It is essential for respiration, which allows energy generation.
• Oxygen supports the metabolism of carbohydrates and fats.

Carbon Dioxide (CO₂)

• Carbon dioxide is a trace gas, present at approximately 0.03% in the atmosphere.
• It is a greenhouse gas that helps regulate temperature by absorbing heat.
• Plants use it in photosynthesis, along with chlorophyll and sunlight, to produce food.
• Absorbs infrared radiation, contributing to global warming by trapping heat, which increases global temperatures.
• CO₂ levels have risen from 280 ppm in the 1800s to 400 ppm in 2024.
• Primary causes of increasing levels include vehicular emissions, industrial pollution, thermal power plants, mining, and the burning of coal and fossil fuels.
• Melting glaciers, rising sea levels, increasing sea temperatures, coral reef death, and ocean eutrophication are effects.

Environmental, Economic, and Social Impacts of Climate Change

• Water body accumulation, climate pattern disturbance, and flora and fauna loss are effects.
• Agricultural productivity, income, taxes, GDP, and infrastructure development are economically affected.
• Includes risk of poverty, floods, and droughts.
• Drinking water accessibility, the fishing industry, farmers, tribes, women, children, tourism, and human development are socially affected.

Ozone (O₃)

• Ozone is a pungent gas that is harmful in high concentrations.
• It is found in the stratosphere, where it absorbs harmful UV rays "good" ozone.
• The troposphere has "bad" ozone, formed from hydrocarbons and pollutants.
• At an altitude of 50 km, oxygen (O₂) splits into O atoms due to UV rays, which then combine to form ozone (O₃).

Water Vapor

• Water vapor is a variable gas and the gaseous of water, originating from oceans, seas, water bodies, soil, plants, and vegetation.
• It traps heat, helping to regulate atmospheric temperature.
• At the Equator, it makes up 4% of atmospheric gases.
• At the Poles, the concentration is significantly lower at 0.02%.
• The majority of water vapor is concentrated within 6 km from the surface.
• Concentration decreases at higher altitudes
• Clouds, rain, fog, frost, mist, cyclones, and tornadoes are linked to water vapor.

Structure of the Atmosphere

• The atmosphere stretches between 16,000 and 28,000 km from Earth’s surface.
• The first 80 km are most relevant for scientific studies.
• 50% of the atmospheric mass is concentrated in the first 5.5 km.

Ionosphere and Solar Activity

• The ionosphere interacts with solar flares and affects radio wave transmission
• Communications systems can be disrupted by solar flares.
• Solar storms and coronal mass ejections (CMEs) disturb radio waves and GPS signals.
• Solar particles react with Earth’s magnetic field and atmosphere, creating auroras.

Auroras: Formation & Mechanism

• Energetic solar particles collide with gases in Earth's atmosphere
• Gas molecules are excited, lose energy, and emit photons of light, resulting in auroras.
• Aurora Borealis, or Northern Lights, appear near the North Pole.
• Aurora Australis, or Southern Lights, appear near the South Pole.

Exosphere: The Outermost Layer

• The exosphere is a rarefied outer atmosphere with vacuum-like conditions.
• Experiences extremely high temperatures, ranging from 5000°C to 6000°C
• Geostationary satellites orbit in this layer at approximately 36,000 km above Earth.
• It is the least explored atmospheric layer and is still being studied.

Nitrogen accounts for approximately 78% of the atmosphere and is essential for all life forms. While plants cannot directly absorb it, nitrogen fixation converts it into usable forms with the help of bacteria. Oxygen makes up about 21% of the atmosphere and is highly reactive.