🌍

Understanding Biogeochemical Cycles

May 6, 2025

Environmental Science: Biogeochemical Cycles

Introduction

  • Presenter: Mr. Anderson
  • Topic: Biogeochemical Cycles
    • Biological, geological, and chemical processes by which nutrients move around the planet.

Key Concepts

  • Biogeochemical Cycles: The movement of nutrients through living (biotic) and non-living (abiotic) systems.
  • Conservation of Matter: The total amount of carbon and nitrogen is constant; it cycles between the living and non-living worlds.
  • Mnemonic for Nutrients: SCHNAPS - Sulfur, Carbon, Hydrogen, Nitrogen, Oxygen, Phosphorus.

Cycles Discussed

1. Water Cycle

  • Process:
    • Evaporation: Water from oceans, lakes, and streams.
    • Evapotranspiration: Water transpired from plants.
    • Condensation: Formation of clouds.
    • Precipitation: Rainfall.
    • Runoff: Water flows on the surface and through groundwater.
  • Importance: Essential for plant and animal hydration.

2. Carbon Cycle

  • Process:
    • Photosynthesis: Plants and phytoplankton absorb CO2.
    • Respiration: Animals release CO2 back into the atmosphere.
    • Fossil Fuels: Carbon stored in coal and oil, released upon combustion.
  • Cycle: Carbon moves from atmosphere to living organisms and back.

3. Nitrogen Cycle

  • Unique Aspect: Relies heavily on bacteria.
  • Key Processes:
    • Nitrogen Fixation: Bacteria convert atmospheric nitrogen into ammonia.
    • Assimilation: Plants absorb ammonia; animals obtain nitrogen by eating plants.
    • Decomposition: Converts nitrogen back into ammonium.
    • Nitrification: Ammonium is converted into nitrites and nitrates.
    • Denitrification: Returns nitrogen to the atmosphere.
  • Limiting Nutrient: Essential for growth, can cause eutrophication.

4. Phosphorus Cycle

  • Characteristics: No atmospheric component; cycle is slow.
  • Process:
    • Weathering: Releases phosphorus from rocks.
    • Assimilation: Plants absorb phosphorus from soil.
    • Return to Environment: Through excretion and decay.
    • Sedimentation: Phosphorus eventually settles in ocean sediments.
  • Limiting Nutrient: Can also lead to eutrophication.

5. Sulfur Cycle

  • Sources:
    • Bacteria: Convert to dimethyl sulfide.
    • Volcanic Activity: Releases hydrogen sulfide, forms sulfur dioxide.
    • Factories: Emit sulfur dioxide.
  • Process:
    • Acid Rain: Sulfuric acid and sulfates return sulfur to the earth.
    • Assimilation and Return: Integrated into living organisms and returned through decay.
  • Connection to Rock Cycle: Involves fossil fuels.

Conclusion

  • Matter is conserved and moves through biotic and abiotic systems.
  • Remember the nutrients using SCHNAPS.
  • Understand the importance of each cycle and its role in the planet's ecology.

Review Questions

  • Can you identify how each nutrient moves through its respective cycle?
  • Why are nitrogen and phosphorus considered limiting nutrients?

Note: This study guide summarizes the key points of biogeochemical cycles as discussed in the lecture. It is essential to understand each cycle's unique processes and their ecological importance.

Full transcript