Cycling of matter

IB Syllabus: 2.5.4

Ch. 4

Syllabus Statements

• 2.5.4: Describe and explain the transfer and transformation of materials as they cycle within an ecosystem

Biogeochemical cycles

• Nutrients needed for life are continuously cycled between living and nonliving things

• Life Earth Chemical cycles

• Driven by incoming solar energy

• Connect past – present – future by recycling chemical compounds

• Oxygen, Carbon, Nitrogen, Phosphorous, and water

Water Cycle

• Collects, purifies and distributes earth’s constant water supply– Evaporation – converts water into vapor– Transpiration – evaporation from plant leaves– Condensation – vapor to liquid– Precipitation – rain, sleet, snow, hail– Infiltration – movement of water into soil– Percolation – flow of water to aquifers– Runoff – movement of water over land surface

Hydrologic cycle

Water cycle

• Sun powers the cycle – 84% vapor from ocean

• Warmer air holds more water• Relative humidity = amount of water vapor

in a mass of air expressed as a % of the maximum the air could support at that temp

• Wind and air masses transport water around the earth

Water cycle II

• Precipitation – needs condensation nuclei to occur– Soil dust, volcanic ash, smoke, sea salt, particulates

• Some locked in glaciers, most into oceans as surface runoff

• Runoff sculpts earth’s surface & transports nutrients

• Water purification happens at many steps

Hydrologic Cycle

Human Influences

1. Withdrawing large quantities of fresh water from surface and ground water

• Aquifer depletion and saltwater intrusion

2. Clearing vegetation for agriculture, mining, construction

• Increase runoff, flooding, erosion, Decrease infiltration

3. Modifying water quality• Adding nutrients, changing natural processes

Carbon cycle

• “C” is the basic building block of life

• Global gaseous cycle based on CO2

• Producers remove CO2 from the atmosphere in photosynthesis

• Respiration of organisms puts CO2 back into atmosphere

• Organic carbon stored in living tissues and fossil fuel deposits

Terrestrial Carbon cycle

Carbon storages

1. Organisms store most of the carbon• organic compounds

2. Sedimentary rocks such as limestone• Carbon reenters cycle when sediments dissolve

naturally or by acid rain

3. Oceans• Gas dissolves into ocean at surface• Removed by marine algae in photosynthesis

4. Marine organisms• Reaction of CO2 with Ca in organisms to produce

CaCO3 for shells and

Aquatic Carbon Cycle

Human effects

1. Adding Carbon to the Atmosphere– Clearing trees and plants that absorb CO2

through photosynthesis– Burning fossil fuels and wood increasing

CO2

2. Enhance the greenhouse effect• Raise sea level• Disrupt food production• Destroy habitats

Nitrogen cycle

1. Nitrogen Fixation

• Specialized bacteria convert atmospheric N2 into NH3

– N2 + 3 H2 2 NH3

Done by

• Cyanobacteria – in soil and water

• Rhizobium – bacteria living in root nodules of a variety of legume plants

2. Nitrification

• A two step process

• Ammonia in soil converted to nitrite and nitrate

• Aerobic bacteria complete this process

– NH3 NO2- (toxic to plants)

– NO2- NO3

- (easily taken up by plants as nutrient

3. Absorption / Assimilation

• Plant roots absorb inorganic nitrogen ions– nitrates, ammonium

• Ions used to make nitrogen containing organic molecules– DNA, amino acids, proteins

• Animals get nitrogen by eating plants or other plant-eating animals

4. Ammonification

• After N has been used in living things and it leaves as waste or death…

• Bacterial decay results

• Producing– Simpler inorganic compounds like NH3

– Water soluble salts containing NH4+

5. Denitrification

• Anaerobic bacteria in waterlogged soils and bottom sediments

• Convert nitrogen compounds back into gas forms and release into the atmosphere

NH3 NO2- N2

NH4

+ NO3- N2O

Human effects on the N-cycle

1. Inputs of commercial inorganic fertilizer

2. Adding NO to the air through combustion of fuels

• Enters water cycle Acid Rain

3. Removing “N” from the crust by mining

4. Removing “N” from soil• Harvest crops, irrigation, deforestation

5. Adding “N” to aquatic systems from runoff

http://water.tamu.edu/images/erosion.jpg

The Phosphorous cycle

• Through water organisms earth’s crust• Very little in the atmosphere• Found as phosphate salts in terrestrial rocks and

ocean sediments• Into organisms by uptake & assimilation by

plants, consumption & assimilation by animals, then animal waste returns it to water or to the land (guano)

• Often a limiting factor in plant growth both terrestrial and aquatic

Phosphorous cycle

Human effects

1. Mining large amounts of phosphate rock• Inorganic fertilizers, Detergents

2. Reducing available phosphate in tropical forests by removing trees

• Soil nutrients washed away w/out trees

3. Adding excess phosphate to aquatic systems

• Runoff of animal waste, commercial fertilizer from farmland, municipal sewage discharge

Florida Phosphate mining

The sulfur cycle

• Most “S” stored underground in rocks and minerals including salts in ocean sediment

• Enters the atmosphere from volcanoes, sea spray, decomposition in aquatic habitats

• Marine algae may produce DMS sulfur compounds in large quantities

• In atmosphere it may mix into hydrologic cycle to form sulfuric acid – acid rain

Sulfur cycle

Human effects

1. Burning “S” containing coal and oil for electricity production

• 2/3 of human SO2 inputs

2. Refining “S” containing petroleum into gasoline, heating oil, etc.

3. Smelting of “S” compounds of metallic minerals producing pure metals

• Copper, Lead, Zinc

Cycle types

• With all cycles common features allow grouping

• Groups based on storages

–Sedimentary cycle – major storage in the ground

• E.x. phosphorous cycle

–Atmospheric cycle – major storage in the atmosphere

• E.x. nitrogen cycle

You should be able to create a flow diagram of Carbon, Water

and Nitrogen cycles

• http://www.colorado.edu/GeolSci/courses/GEOL1070/chap04/chapter4.html