Biogeochemical Cycles: Water, Carbon, Nitrogen, Phosphorus & Human Impact

Biogeochemical Cycles

Cycles that describe the movement and transformation of essential elements through the biotic (living) and abiotic (non-living) components of the Earth.

Hydrological Cycle

A cycle driven by water's properties, involving processes like evaporation, condensation, and precipitation.

Water's Polarity

Water molecules have a slightly positive charge on one end and a slightly negative charge on the other, allowing them to form hydrogen bonds.

Universal Solvent

Due to its polar nature, water can dissolve a wide range of substances, making it essential for transporting nutrients and facilitating chemical reactions.

High Specific Heat Capacity

Water can absorb and release large amounts of heat with only small changes in temperature, helping regulate Earth's climate.

Energy Storage in Water

Water's ability to absorb heat means it plays a significant role in energy transfer and storage within the Earth system.

Evaporation

The process where water turns into vapor.

Condensation

The process where vapor turns back into liquid.

Precipitation

Water falling from the atmosphere as rain, snow, etc.

Transpiration

The process where water is released from plants.

Sublimation

The process where ice directly turns into vapor.

Infiltration

The process where water seeps into the ground.

Percolation

The process where water moves through soil and rock.

Groundwater Flow

The movement of water underground.

Fast Nutrient Cycles

Cycles where nutrients change form and location relatively quickly, driven by biological processes.

Slow Nutrient Cycles

Cycles where nutrient transformations can take thousands or millions of years, driven by geological processes.

Organic Nutrient Forms

Nutrient forms that are generally more readily available and usable by life.

Inorganic Nutrient Forms

Nutrient forms that are often less available to living organisms.

Carbon Cycle

The cycle that describes the movement of carbon, essential for virtually all life processes.

Photosynthesis

The process where plants and phytoplankton take in atmospheric CO2 and convert it into organic compounds.

Respiration

The process where organisms release CO2 back into the atmosphere through breathing.

Decomposition

The process where microorganisms break down dead organic matter, releasing carbon back into the soil and atmosphere.

Fossilization

The process where organic matter can form fossil fuels over millions of years, storing carbon in the lithosphere.

Burning of Fossil Fuels

Human activities that release large amounts of stored carbon into the atmosphere as CO2.

Ocean Exchange

Carbon dioxide dissolves in and is released from oceans, and is also incorporated into marine sediments.

Nitrogen Cycle

A cycle involving the conversion of atmospheric nitrogen into usable forms by nitrogen-fixing bacteria, and the processes of ammonification, nitrification, assimilation, and denitrification.

Importance of Nitrogen

Nitrogen is a crucial component of DNA and amino acids, making it vital for protein synthesis and overall growth.

Atmospheric Nitrogen (N₂)

The most abundant form of nitrogen in the atmosphere, largely unavailable to most plants.

Nitrogen Fixation

Conversion of atmospheric N₂ into usable forms (like ammonia) by nitrogen-fixing bacteria, often found in legume root nodules or soil.

Ammonification

Decomposition of organic matter by decomposers (bacteria and fungi) releases ammonia (NH₄⁺).

Nitrification

Conversion of ammonia to nitrites (NO₂⁻) and then to nitrates (NO₃⁻) by nitrifying bacteria.

Assimilation

Plants absorb nitrates from the soil to build organic molecules.

Denitrification

Conversion of nitrates back into atmospheric nitrogen (N₂) by denitrifying bacteria, completing the cycle.

Dissolution

Nitrogen compounds can dissolve in water, facilitating their transport through the hydrosphere.

Phosphorus Cycle

A cycle involving the movement of phosphorus through rocks, soils, water bodies, and living organisms.

Importance of Phosphorus

Phosphorus is essential for DNA, energy storage (ATP), and bone health.

Primary Reservoirs of Phosphorus

Phosphorus is mainly found in the lithosphere (rocks) and hydrosphere.

Weathering of Rocks

Phosphorus is released from rocks through weathering and erosion, entering soils and water bodies.

Aerosolization

Phosphorus can become airborne through combustion and volcanic activity.

Uptake by Organisms

Plants absorb dissolved phosphorus from soil and water.

Food Webs

Phosphorus moves through terrestrial and marine food webs as organisms consume each other.

Sedimentation

Phosphorus eventually settles in ocean sediments, where it can be locked away for long periods.

Fertilizers

Human use of fertilizers introduces significant amounts of phosphorus into aquatic systems through runoff.

Oxygen Cycle

The cycle involving the movement of oxygen through the atmosphere, biosphere, and lithosphere.

Atmospheric Production of Oxygen

Some oxygen is produced in the atmosphere when sunlight breaks down water molecules.

Reservoir in Lithosphere

Most oxygen on Earth is stored in oxide minerals within the Earth's crust and mantle, but this oxygen is bound and unavailable to life.

Usage of Oxygen

Oxygen is consumed by animals, plants, bacteria, fire, and processes like rusting (oxidation).

Human Interference

Human activities significantly alter the natural balance of biogeochemical cycles.

Burning Fossil Fuels

Releases large amounts of CO₂ into the atmosphere, contributing to climate change.

Agriculture

Involves practices that can alter soil nutrient content, increase erosion, and lead to runoff of fertilizers.

Fertilizer Usage

Excessive use of fertilizers, particularly those containing nitrogen and phosphorus, can lead to eutrophication of water bodies (algal blooms), disrupting aquatic ecosystems.

Biogeochemical Cycle

The pathway by which a chemical substance moves through biotic and abiotic compartments of Earth.

Biosphere

The sum of all ecosystems on Earth, encompassing all living organisms and their environments.

Abiotic

Non-living components of an ecosystem (e.g., water, soil, atmosphere, rocks).

Biotic

Living or once-living components of an ecosystem (e.g., plants, animals, fungi, bacteria).

Polar Molecule

A molecule with an uneven distribution of electron density, resulting in a partial positive and partial negative charge.

Specific Heat Capacity

The amount of heat required to raise the temperature of one gram of a substance by one degree Celsius.

Eutrophication

The excessive richness of nutrients in a lake or other body of water, frequently due to runoff from the land, which causes a dense growth of plant life and death of animal life from lack of oxygen.