The biogeochemical cycle describes the flow of nutrients and other elements between biotic and abiotic ecosystem components. The biogeochemical cycles are required to maintain ecological homeostasis and ensure the survival of life on Earth. This article will explain to you the Biogeochemical Cycle which will be helpful in preparing the Environment syllabus for the UPSC Civil service exam.

What is a Biogeochemical Cycle?

• A biogeochemical cycle is the passage of a chemical substance between the Earth's biotic and abiotic components.
• The atmosphere, hydrosphere, and lithosphere are all biotic components, whereas the biosphere is abiotic.
• As geology and chemistry play essential roles in the study of this process, the recycling of inorganic materials between living organisms and their environment is referred to as a biogeochemical cycle.

Nutrient Cycling

• A nutrient cycle is a cyclic mechanism through which nutrients travel in order to be recycled and used.
• Cells, organisms, communities, and ecosystems are all included in the pathway of a nutrient cycle.
• The pace of nutrient cycling is influenced by a variety of biotic, physical, and chemical variables.
• Since elements move cyclically from the environment to living creatures and back to the environment, nutrient cycles in nature are called biogeochemical cycles.

Nutrient Cycling - Types

Based on the Replacement Period

• Perfect Cycle: Nutrients are replaced at the same rate as they are used in a perfect nutrient cycle. Most Gaseous cycles are thought to be perfect cycles.
• Imperfect Cycle: Sedimentary cycles are imperfect because certain nutrients are lost from the cycle and become trapped in sediments, making them unavailable for immediate cycling.

Based on the Nature of the Reservoir

• Gaseous Cycle: The atmosphere or the hydrosphere serves as the reservoir in the gaseous cycle.
• Sedimentary Cycle: The reservoir in the sedimentary cycle is the Earth's crust.

Gaseous Cycles

Water, carbon, and nitrogen are the three most significant gaseous cycles.

Water (Hydrologic) Cycle

• The water (hydrological) cycle is the solar-driven continuous circulation of water in the Earth-atmosphere system.
• The atmosphere, oceans, lakes, rivers, soils, glaciers, snowfields, and groundwater are all key reservoirs for water in our world.
• Evaporation, transpiration, condensation, precipitation, deposition, runoff, infiltration, and groundwater flow are all processes that carry water from one reservoir to another.
• It also refers to the continuous flow of water between the land surface, oceans, and subsoil, as well as between species.
• The evaporation of water from the ocean's surface starts the hydrologic cycle.

*To know more about this topic, click this link Water (Hydrologic) Cycle

The Carbon Cycle

• Carbon, primarily in the form of carbon dioxide (CO2), is present in the atmosphere.
• A continual exchange of carbon between the atmosphere and organisms is referred to as the carbon cycle.
• The process of photosynthesis transports carbon from the atmosphere to green plants and ultimately to organisms.
• It returns to the atmosphere through the processes of respiration and decomposition of dead organic stuff. It is majorly a short-term cycle.

*To know more about this topic, click this link Carbon Cycle

The Nitrogen Cycle

• Nitrogen is a basic building unit of every living tissue and is a vital component of protein. It accounts for roughly 16 percent of all proteins by weight.
• There are three primary phases in the nitrogen cycle: nitrogen fixation, nitrification, and denitrification.
• The atmosphere, hydrosphere, and lithosphere are all part of this cycle.
• Nitrogen fixation is an anaerobic (oxygen-free) process that converts atmospheric nitrogen (N 2) to NH 3. It is done by nitrogen-fixing bacteria.
• Nitrification is a two-step process. The ammonium ion (NH4+) is first reduced to NO2.
• The molecule is then further oxidized to produce NO 3. Bacteria in the soil play a role in both processes once again.
• Denitrification is the conversion of nitrates to nitrogen gas. Denitrifying bacteria work in a similar way to nitrogen-fixing bacteria.

*To know more about this topic, click this link NitrogenCycle

Sedimentary Cycle

• Sedimentary cycles are biogeochemical cycles that have the Earth's crust as their reservoir.
• Iron, calcium, phosphorus, sulphur, and other earthbound elements are all part of the sedimentary cycle.
• Sedimentary cycles differ depending on the element, but they all have a solution (or water-related) phase and a rock (or sediment) phase.
• Sedimentary cycles take a very long time to complete.
• The Phosphorus cycle and Sulphur cycle are the most important sedimentary cycles.

Phosphorus Cycle

• Phosphorus circulates through rocks, water, soil, sediments, and organisms in a cycle.
• Rain and weathering cause phosphate ions and other minerals to be released from rocks throughout time.
• This inorganic phosphate is subsequently dispersed throughout the soil and water.
• Inorganic phosphate is taken up by plants from the soil. Animals may eat the plants after that.
• Phosphate is integrated into organic molecules such as DNA once it reaches the plant or animal.
• When a plant or animal dies, it decomposes, releasing organic phosphate into the soil.
• Bacteria that break down organic materials to inorganic forms of phosphorus can make organic forms of phosphate available to plants in the soil. Mineralisation is the name for this process.
• Phosphorus from the soil can end up in streams and, eventually, the oceans.
• It can be absorbed into sediments over time once it reaches that location.

*To know more about this topic, click this link Phosphorus Cycle

Sulphur Cycle

• The majority of the world's sulphur is bound up in rocks and salts or buried deep within oceanic sediments.
• Sulphur is also contained in the air we breathe. Both natural and human sources contribute to its presence in the atmosphere.
• Volcanic eruptions, microbiological activities, water evaporation, and decomposing organisms are just a few examples of natural resources.
• When sulphur enters the atmosphere as a result of human activity, it is primarily due to industrial activities that generate large amounts of sulphur dioxide (SO2) and hydrogen sulphide (H2S) gases.
• Sulphur dioxide reacts with oxygen to form sulphur trioxide gas (SO3), or with other chemicals in the atmosphere to produce sulphur salts, when it reaches the atmosphere.
• Sulphur dioxide can also form sulphuric acid when it reacts with water (H2SO4).
• Dimethyl Sulphide, which is exhaled into the atmosphere by plankton species, can also be used to make sulphuric acid.
• All of these particles will either fall back to earth or will react with rain and fall as acid deposits.
• Plants will then absorb the particles, which will then be released back into the atmosphere, restarting the sulphur cycle.

*To know more about this topic, click this link Sulphur Cycle

Calcium Cycle

• Calcium is primarily found in the form of rock, minerals, or structural calcium embedded in the mineral crystal lattices of soil particles, and it is not easily available.
• The majority of calcium in the soil is insoluble unless it is 'weathered off' of minerals or bacteria break down organic materials into soluble calcium.
• Some calcium, however, is held loosely or securely on the soil or in the soil solution and is available to plants and microbes.
• Animals, microbes, and plants decompose, and the calcium in their bodies is mineralized and released back into the soil.
• Roots also return minerals, carbohydrates, and other chemicals to the soil on a regular basis, including calcium.
• Calcium is adsorbed to the surface of the clay and negatively charged organic particles in the soil because it is a positively charged ion. Positively charged ions (cations) bind to soil particles and are referred to as "exchangeable ions" because they can be exchanged with other ions in the soil solution.
• Calcium enters an organic phase when it is taken by plants or microbes. Calcium is constantly exchanged between plant roots, microbes, and soil in this form.
• Decomposers break down a plant, animal, or soil fauna after it dies, and calcium is released back into the soil in a soluble form.
• As a result, calcium alternates between the soluble (and available) and the insoluble (and unavailable) phases.

*To know more about this topic, click this link Calcium Cycle

Importance of Biogeochemical Cycle

• It is required for the conversion of nutrients from one form to another so that they may be used by various organisms.
• For example, plants cannot take atmospheric nitrogen and must fix it and convert it to ammonium and nitrate before they can be used.
• Biogeochemical Cycles help to keep the ecosystem in balance by storing nutrients for future use.
• The transfer of elements from one location to another for utilization happens through a biogeochemical cycle, such as from air to soil or from water to soil.
• Living creatures interact with their surroundings' abiotic components through biogeochemical cycles.

Conclusion

Biogeochemical cycles are very crucial to ecosystems. Many of the nutrients that living creatures require, such as carbon, nitrogen, and phosphorus, are constantly on the move. Essential elements are frequently held in reservoirs, where they can be removed from circulation and stored for years. Thus the biogeochemical cycle functions as a recycling system in nature.

FAQs

Q1: What is a biogeochemical cycle?

Q2: What are the major types of biogeochemical cycles?

Q3: How does the water cycle function?

Q4: Why are biogeochemical cycles important?

Q5: What human activities impact biogeochemical cycles?

MCQs

1. Which of the following is NOT a biogeochemical cycle?

a) Carbon cycle

b) Oxygen cycle

c) Water cycle

d) Lunar cycle

2. What process is primarily responsible for returning water vapor to the atmosphere?

a) Evaporation

b) Transpiration

c) Precipitation

d) Condensation

3. Which cycle is most directly affected by agricultural practices?

a) Water cycle

b) Carbon cycle

c) Nitrogen cycle

d) Phosphorus cycle

4. What role do decomposers play in biogeochemical cycles?

a) They produce oxygen.

b) They break down organic matter.

c) They absorb carbon dioxide.

d) They increase soil erosion.

5. Which of the following cycles does not have a gaseous phase?

a) Carbon cycle

b) Water cycle

c) Nitrogen cycle

d) Phosphorus cycle

GS Mains Questions and Model Answers

Q1: Discuss the significance of biogeochemical cycles in maintaining ecological balance.

Answer: Biogeochemical cycles are vital for maintaining ecological balance as they regulate the flow of essential nutrients through ecosystems. They ensure the availability of key elements such as carbon, nitrogen, and phosphorus, which are necessary for the growth and survival of organisms. By recycling these elements, biogeochemical cycles contribute to soil fertility, plant growth, and overall ecosystem health. Disruptions in these cycles, often due to human activities, can lead to environmental imbalances, affecting biodiversity and ecosystem stability.

Q2: Analyze the impact of human activities on the nitrogen cycle.

Answer: Human activities, particularly industrial agriculture and fossil fuel combustion, significantly impact the nitrogen cycle. The extensive use of nitrogen-based fertilizers increases the availability of nitrogen in the soil, leading to nutrient runoff into waterways. This can cause eutrophication, resulting in algal blooms that deplete oxygen and harm aquatic life. Additionally, the release of nitrogen oxides from vehicles and industries contributes to air pollution and acid rain, further disrupting the natural balance of the nitrogen cycle and adversely affecting ecosystems.

Q3: Evaluate the role of the carbon cycle in addressing climate change.

Answer: The carbon cycle plays a crucial role in addressing climate change as it regulates the levels of carbon dioxide (CO2) in the atmosphere, a key greenhouse gas. Natural processes such as photosynthesis and respiration help maintain carbon balance, while human activities, particularly fossil fuel combustion and deforestation, have led to elevated CO2 levels. Understanding and managing the carbon cycle is essential for mitigating climate change impacts. Strategies such as reforestation, sustainable land use, and reducing carbon emissions are vital for enhancing carbon sequestration and promoting a stable climate.

Previous Year Questions on  Biogeochemical Cycle

1. UPSC CSE Prelims 2021

Question: Which of the following is true regarding the phosphorus cycle?

Answer: The phosphorus cycle primarily involves the movement of phosphorus through soil, water, and living organisms without a significant gaseous phase. This distinction is important for understanding its role in ecosystems.

2. UPSC CSE Mains 2020

Question: Discuss the interconnection between biogeochemical cycles and ecosystem health.

Answer: Biogeochemical cycles are interconnected with ecosystem health, as they facilitate nutrient recycling essential for plant and animal life. Disruptions in one cycle can adversely affect others, leading to imbalances in ecosystems. For instance, alterations in the nitrogen cycle through excessive fertilizer use can result in waterway eutrophication, impacting aquatic ecosystems. Understanding these interconnections is vital for conservation efforts and promoting sustainable practices that ensure the resilience of ecosystems in the face of environmental change.