A comprehensive guide to the Gaseous Cycle and its role in the nutrient cycle. Understand its significance in ecosystems and its relevance for UPSC preparation.

Carbon Cycle (Gaseous Cycle): The Role of Carbon in the Atmosphere and Ecosystems

: the reservoir is the atmosphere or the hydrosphere — water cycle, carbon cycle, nitrogen cycle, methane (compound) cycle, etc.

Steps in the Carbon Cycle and Their Environmental Impact

• Description: The carbon cycle describes the movement of carbon between the atmosphere, oceans, land, and living organisms.
• 1. Carbon Fixation: Plants absorb carbon dioxide (CO2) from the atmosphere during photosynthesis to produce organic compounds.
• 2. Respiration: Organisms release carbon dioxide back into the atmosphere as a byproduct of cellular respiration.
• 3. Decomposition: Dead plants and animals are broken down by decomposers, releasing carbon dioxide into the soil and atmosphere.
• 4. Combustion: Burning of fossil fuels and biomass releases carbon dioxide into the atmosphere.
• 5. Carbon Sequestration: Some carbon is stored in long-term reservoirs such as forests, oceans, and sedimentary rocks.

Nitrogen Fixing – Converting Atmospheric Nitrogen (N2) into Ammonia (NH3)

• Description: Nitrogen fixation is the conversion of atmospheric nitrogen gas (N2) into ammonia (NH3) by nitrogen-fixing bacteria.
• Process: Nitrogen-fixing bacteria in the soil or in the root nodules of leguminous plants convert N2 gas into ammonia through biological or industrial processes.
• Importance: Ammonia serves as a vital nutrient for plants, facilitating their growth and development.

Nitrification – The Conversion of Ammonia to Nitrites and Nitrates

• Description: Nitrification is the conversion of ammonia (NH3) into nitrites (NO2-) and nitrates (NO3-) by nitrifying bacteria.
• Process: Nitrifying bacteria oxidize ammonia to nitrite, then to nitrate, in the presence of oxygen.
• Role: Nitrites and nitrates are essential nitrogen compounds that can be absorbed by plants as nutrients.

Methane Cycle (Gaseous Cycle): Understanding the Movement and Impact of Methane

Natural Sources of Methane Emissions in Ecosystems

• Description: Methane is produced naturally by anaerobic bacteria during the decomposition of organic matter in wetlands, oceans, and the digestive systems of animals.
• Process: Methanogenic archaea break down organic material in the absence of oxygen, producing methane as a byproduct.
• Role: Methane is a potent greenhouse gas that contributes to global warming and climate change.

Human Sources of Methane Emissions and Their Environmental Consequences

• Description: Human activities such as agriculture, livestock farming, rice cultivation, and fossil fuel extraction also contribute to methane emissions.
• Process: Practices like enteric fermentation in livestock, rice paddies, and landfills release methane into the atmosphere.
• Impact: Increased methane concentrations exacerbate climate change and contribute to environmental degradation.

Methane Sink: How Methane is Removed from the Atmosphere

• Description: Methane is removed from the atmosphere through oxidation by hydroxyl radicals (OH-) and soil bacteria.
• Process: Methane reacts with hydroxyl radicals in the atmosphere, forming water vapor and carbon dioxide, which are less potent greenhouse gases.
• Role: Methane sinks help regulate atmospheric methane concentrations and mitigate its impact on climate change.