The Biogeochemical Cycles

The Biogeochemical Cycles
Chapter 5 The Biogeochemical Cycles Botkin & Keller Environmental Science 5e

Environmental Science 5e
The Geologic Cycle The Geologic Cycle: The processes responsible for formation and change of Earth materials Best described as a group of cycles: Tectonic Rock hydrologic Biochemical Botkin & Keller Environmental Science 5e

Tectonic Cycle Creation and destruction of the Lithosphere

The Rock Cycle The rock cycle: Numerous processes that produce rocks and soils Depends on other cycles: tectonic cycle for energy Hydrologic cycle for water for erosion Rock is classified as Igneous – high heat, volcanic Sedimentary – weathering & erosion Metamorphic – compact, melting Botkin & Keller Environmental Science 5e

How Chemicals Cycle Biogeochemical Cycle The complete path a chemical takes through the four major components – or reservoirs – of Earth’s systems Atmosphere Hydrosphere Lithosphere Biosphere Botkin & Keller Environmental Science 5e

Biogeochemical Cycles and Life: Limiting Factors
Macronutrients Elements required in large amounts by all life Include the “big six” elements that form the fundamental building blocks of life: carbon oxygen hydrogen phosphorus nitrogen sulfur Micronutrients Elements required either in small amounts by all life or moderate amounts by some forms of life and not all by others Limiting factor When chemical elements are not available at the right times, in the right amounts, and in the right concentrations relative to each other Botkin & Keller Environmental Science 5e

Major Chemical Cycles Water (hydrologic) Carbon Nitrogen Phophorus Botkin & Keller Environmental Science 5e

The Hydrologic Cycle The Hydrologic Cycle: The transfer of water from the oceans to the atmosphere to the land and back to the oceans. POWERED BY THE SUN !! Includes: Evaporation of water from the oceans Precipitation on land Evaporation from land Runoff from streams, rivers, and sub-surface groundwater Transpiration from plants Botkin & Keller Environmental Science 5e

Human Impacts Withdrawal: Removal from society & industry faster than recharged (overdraft) Increased flooding: Removal of wetlands & creating non-pourous tracts Deforestation: Clearing land reduces transpiration, therefore there is a decrease in precipitation. Botkin & Keller Environmental Science 5e

Botkin & Keller Environmental Science 5e

The Carbon Cycle 4th most abundant element in the universe Building block of life Cycles through the geosphere, biosphere, ocean and atmosphere Two types of cycling Geological carbon cycle Biological carbon cycle Botkin & Keller Environmental Science 5e

Geological Carbon Cycle

How does this work? CO2 reacts with atmospheric water and minerals to produce calcium carbonate. Calcium carbonate rock (limestone) weathered by water – dissolves and travels to ocean. Forms sedimentary layers in the ocean. Through plate tectonics, sediments subduct and melts. Carbon is released into the atmosphere during volcanic eruption as CO2 Botkin & Keller Environmental Science 5e

Biological Carbon Cycle

Carbon Reservoirs Ocean – dissolved, calcium carbonate of marine organisms shells Geosphere – soils, fossil fuels Biosphere –living organisms Atmosphere – 0.038% of troposphere (Acts as natural thermostat for Earth) Botkin & Keller Environmental Science 5e

Human impacts Increases Carbon Dioxide in the atmosphere by: Burning of fossil fuels Clear cutting of trees Botkin & Keller Environmental Science 5e

The Nitrogen Cycle The nitrogen cycle: Limiting factor for primary productivity As nutrient: NO3 Conversion of N2 gas into nutrients – lightning & nitrogen fixing bacteria Nitrogen reservoirs: Atmosphere 78% of Troposphere Botkin & Keller Environmental Science 5e

Common nitrogen compounds
N2 - nitrogen gas NH4 - ammonium NH3 - ammonia NO3 - nitrate NO2 - nitrite (with -2 charge), nitrogen dioxide N2O - nitrous oxide, nitrogen oxide NO – nitric oxide, nitrogen monoxide HNO3- nitric acid Botkin & Keller Environmental Science 5e

Steps in the Nitrogen Cycle
Nitrogen fixation: N2 converted to NH4 or NH3 by bacteria Ammonification (mineralization) Decomposers turn organic material into NH4 or NH3 Nitrification Bacteria convert NH4 & NH3 into NO3 for plant uptake Denitrification Bacteria convert NH4 & NH3 into N2 & N2O Botkin & Keller Environmental Science 5e

Nitrogen fixation In order to be used by most living organism nitrogen must by in the form of NH3 or NO3. Nitrogen is ‘fixed’ by lightning or bacteria. ‘Fixing’ allows nitrogen to be made biologically available. Can be found on the roots of legumes. Botkin & Keller Environmental Science 5e

Nitrification Soil bacteria convert ammonia (NH4) into a form that plants can use NO3 Botkin & Keller Environmental Science 5e

Assimilation Plants absorb ammonium (NH3), ammonia (NH4) and nitrate (NO3) through their roots. Heterotrophs (or organisms that receive energy from consuming other organisms) obtain nitrogen from consuming plant proteins or other animals. Botkin & Keller Environmental Science 5e

Ammonification Decomposing bacteria convert dead organisms and other waste to ammonia (NH3) or ammonium (NH4), which can be reused by plants Botkin & Keller Environmental Science 5e

Denitrification Specialized bacteria (anaerobic) convert ammonia back to nitrates and nitrites THEN back into nitrogen gas and nitrous oxide, where they enter the atmosphere. Botkin & Keller Environmental Science 5e

Nitrogen Cycle Botkin & Keller Environmental Science 5e

Additional Info Assimilation: Plants take up inorganic nitrogen (NH3 & NO3) and convert to organic compounds (amino acids) Botkin & Keller Environmental Science 5e

Human Impacts Excess Nitrates Animal waste, municipal discharge Can promote algae growth Burning of Fossil Fuels Released NO, NO2 and HNO3 Use of inorganic fertilizers Increases denitrification by anaerobic bacteria, and therefore releases more NO2 into the atmosphere. Botkin & Keller Environmental Science 5e

The Phosphorus Cycle The phosphorus cycle: Involves the movement of phosphorus throughout the biosphere, hydrosphere and lithosphere Important because phosphorus is an essential element for life and often is a limiting nutrient for plant growth. Botkin & Keller Environmental Science 5e

Phosphorus Reservoirs
Ocean sediments Terrestrial rock layers Erosion releases PO4 for producers Limiting factor for primary productivity Botkin & Keller Environmental Science 5e

Guano Island The Guano Islands Act (11 Stat. 119, enacted 18 August 1856, codified at 48 U.S.C. ch. 8 §§ ) is United States federal law passed by the U.S. Congress that enables citizens of the United States to take possession of unclaimed islandscontaining guano deposits. Botkin & Keller Environmental Science 5e

Human Impacts Phosphate run-off from Sewage, mining & fertilizers Algal blooms Botkin & Keller Environmental Science 5e

The Biogeochemical Cycles

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