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Chapter 5The Biogeochemical Cycles

Botkin & KellerEnvironmental Science 5e

How Chemicals Cycle

Biogeochemical Cycle The complete path a chemical takes

through the four major components – or reservoirs – of Earth’s systems1. Atmosphere2. Hydrosphere3. Lithosphere4. Biosphere


Chemical Reactions

Chemical reaction: The process in which new chemicals are

formed from elements and compounds through chemical change



Fig 5.3

© 2005 John Wiley and Sons Publishers


Fig 5.4


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


Nutrients and Limiting Factors

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


The Geologic Cycle

The Geologic Cycle: The processes responsible for formation

and change of Earth materials Best described as a group of cycles: Tectonic Hydrologic Rock Biochemical



Fig 5.6


Tectonic Cycle

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



Fig 5.7


Tectonic Cycle: Plate Boundaries

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


The Hydrologic Cycle

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



Fig 5.8


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

Rock is classified as Igneous Sedimentary Metamorphic



Fig 5.9



Fig 5.12



Fig 5.13


The Carbon Cycle

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



Fig 5.14



Fig 5.15


Idealized diagram illustrating photosynthesis for a green plan (tree) and generalized reaction.


Fig 5.16


Idealized diagram showing the carbon cycle in a lake.

The Carbon Cycle:Unanswered Issues

The Missing Carbon Sink Substantial amounts of carbon dioxide

released into the atmosphere but apparently not reabsorbed and thus remaining unaccounted for



Fig 5.17


The Carbon-Silicate Cycle

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.



Fig 5.18


The Nitrogen Cycle 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 nitrogenBotkin & Keller

Environmental Science 5e


Fig 5.19


The Phosphorus Cycle

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.



Fig 5.20


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Chapter 5ogoapes.weebly.com/uploads/3/2/3/9/3239894/apes-chapter_5-ppt.pdf · Chapter 5 The Biogeochemical Cycles ... Environmental Science 5e Fig 5.6 ... oxygen and hydrogen that