Transcript Chapter 2
Chapter 5
The Biogeochemical Cycles
Botkin & Keller Environmental Science 5e
How Chemicals Cycle
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Biogeochemical Cycle
– The complete path a chemical takes through the four major components – or reservoirs – of Earth’s systems 1. Atmosphere 2. Hydrosphere 3. Lithosphere 4. Biosphere Botkin & Keller Environmental Science 5e
Chemical Reactions
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Chemical reaction:
– The process in which new chemicals are formed from elements and compounds through chemical change Botkin & Keller Environmental Science 5e
Fig 5.3
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Fig 5.4
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Biogeochemical Cycles and Life: Limiting Factors
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Macronutrients
– Elements required in large amounts by all life – Include the “big six” elements that form the fundamental building blocks of life: carbon hydrogen oxygen 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
The Geologic Cycle
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The Geologic Cycle:
– The processes responsible for formation and change of Earth materials – Best described as a group of cycles: • Tectonic • Hydrologic • Rock • Biochemical Botkin & Keller Environmental Science 5e
Fig 5.6
Botkin & Keller Environmental Science 5e © 2005 John Wiley and Sons Publishers
Tectonic Cycle
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Tectonic cycle:
– Involves creation and destruction of the solid outer layer of Earth, the lithosphere
Plate tectonics:
– The slow movement of these large segments of Earth’s outermost rock shell – Boundaries between plates are geologically active areas Botkin & Keller Environmental Science 5e
Fig 5.7
Botkin & Keller Environmental Science 5e © 2005 John Wiley and Sons Publishers
Tectonic Cycle: Plate Boundaries
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Divergent plate boundary:
– Occurs at a spreading ocean ridge, where plates are moving away from one another – New lithosphere is produced (seafloor spreading)
Convergent plate boundary
– Occurs when plates collide • Produces linear coastal mountain ranges or continental mountain ranges
Transform fault boundary
– Occurs where one plate slides past another • San Andreas Fault in California Botkin & Keller Environmental Science 5e
The Hydrologic Cycle
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The Hydrologic Cycle:
– The transfer of water from the oceans to the atmosphere to the land and back to the oceans. Includes: • Evaporation of water from the oceans • Precipitation on land • Evaporation from land • Runoff from streams, rivers, and sub-surface groundwater Botkin & Keller Environmental Science 5e
Fig 5.8
Botkin & Keller Environmental Science 5e © 2005 John Wiley and Sons Publishers
The Rock Cycle
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The rock cycle:
– Numerous processes that produce rocks and soils – Depends on other cycles: • tectonic cycle for energy • Hydrologic cycle for water – Rock is classified as • Igneous • Sedimentary • Metamorphic Botkin & Keller Environmental Science 5e
Fig 5.9
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Fig 5.12
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Fig 5.13
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The Carbon Cycle
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Carbon is the element that anchors all organic substances The carbon cycle:
– Carbon combines with and is chemically and biologically linked with the cycles of oxygen and hydrogen that form the major compounds of life Botkin & Keller Environmental Science 5e
Fig 5.14
Botkin & Keller Environmental Science 5e © 2005 John Wiley and Sons Publishers
Fig 5.15
Botkin & Keller Environmental Science 5e © 2005 John Wiley and Sons Publishers
Fig 5.16
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The Carbon Cycle: Unanswered Issues
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The Missing Carbon Sink
– Substantial amounts of carbon dioxide released into the atmosphere but apparently not reabsorbed and thus remaining unaccounted for Botkin & Keller Environmental Science 5e
Fig 5.17
Botkin & Keller Environmental Science 5e © 2005 John Wiley and Sons Publishers
The Carbon-Silicate Cycle
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The carbon-silicate cycle:
– A complex biogeochemical cycle over time scales as long as one-half billion years.
– Includes major geological processes, such as: • Weathering • Transport by ground and surface waters • Erosion • Deposition of crustal rocks – Believed to provide important negative feedback mechanisms that control the temperature of the atmosphere.
Botkin & Keller Environmental Science 5e
Fig 5.18
Botkin & Keller Environmental Science 5e © 2005 John Wiley and Sons Publishers
The Nitrogen Cycle
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The nitrogen cycle:
– Cycle responsible for moving important nitrogen components through the biosphere and other Earth systems – Extremely important because nitrogen is required by all living things
Nitrogen fixation:
– The process of converting inorganic, molecular nitrogen in the atmosphere to ammonia or nitrate
Denitrification:
– The process of releasing fixed nitrogen back to molecular nitrogen Botkin & Keller Environmental Science 5e
Fig 5.19
Botkin & Keller Environmental Science 5e © 2005 John Wiley and Sons Publishers
The Phosphorus Cycle
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The phosphorus cycle:
– Involves the movement of phosphorus throughout the biosphere 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
Fig 5.20
Botkin & Keller Environmental Science 5e © 2005 John Wiley and Sons Publishers