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CARBON CYCLING THROUGH ECOSYSTEMS

Presented by

Scott Weir, Air Quality Coordinator

Kickapoo Tribe in Kansas

CARBON CYCLING THROUGH ECOSYSTEMS

• CARBON (FROM LATIN: CARBO "COAL")

chemical element

nonmetallic

tetravalent — four electrons available

to form covalent chemical bonds

• FOURTH MOST ABUNDANT ELEMENT IN THE UNIVERSE

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DIAMONDS AND COAL: NATURALLY OCCURRING FORMS OF CARBON

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CARBON: ESSENTIAL TO LIFE ON EARTH

Organic compounds contain carbon

All living things need carbon• for structure• for energy

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THE CARBON CYCLE

Carbon is always on the move From• Atmosphere to plants• Plants to animals• Plants and animals to the ground• Living things to the atmosphere• Fossil fuels to the atmosphere• Atmosphere to the oceans

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CARBON MOVES FROM THE ATMOSPHERE TO PLANTS

Photosynthesis

• Carbon dioxide (CO2) pulled from air by plants

• Solar energy used to make plant food for energy

• Carbon incorporated into plant structure

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CARBON MOVES FROM PLANTS TO ANIMALS

Food Chains

• Carbon in plants moves to animals that eat them

• Predators get carbon from their prey

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CARBON MOVES FROM PLANTS AND ANIMALS TO GROUND

Death and Decomposition

• Decay of structure releases carbon to soil

• If buried deep underground, some become fossil fuels after millions of years

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CARBON MOVES FROM LIVING THINGS TO THE ATMOSPHERE

Aerobic Respiration

• Animals breathe in oxygen

• CO2 (resulting from oxidation of carbohydrates) is exhaled

• Plants also release CO2 from oxidation of carbohydrates

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COMPARISON OF PHOTOSYNTHESIS AND RESPIRATION

Photosynthesis Respiration

Produces sugars from light energy

Stores energyOccurs only in cells with

chloroplastsReleases oxygen

Uses waterUses carbon dioxide

Requires light

Burns sugars for energyReleases energy

Occurs in most cellsUses oxygen

Produces waterProduces carbon dioxideOccurs in dark and light

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CARBON MOVES FROM FOSSIL FUELS TO THE ATMOSPHERE

Combustion

• Fossil fuels burned to release energy

• CO2 is result of combustion (rapid oxidation)

• Releases 5,500,000,000 tons of carbon per year

• 3,300,000,000 tons remain in air• 2,200,000,000 tons dissolve in seawater

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CARBON MOVES FROM THE ATMOSPHERE TO THE OCEANS

Dissolved CO2

• Oceans and other bodies of water “soak up” atmospheric carbon

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ATMOSPHERIC CYCLE

CO2 leaves atmosphere through photosynthesis

CO2 also dissolves directly into water (oceans, lakes, etc.), as well as falling raindrops

Human activity over past 200 years has increased amount of atmospheric carbon

• Mainly as CO2

• Ecosystems extraction of CO2 from atmosphere has been reduced

• agricultural activity• deforestation

• Increased direct emission of CO2 • burning fossil fuels and • manufacturing concrete

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TERRESTRIAL BIOLOGICAL CYCLETerrestrial biosphere includes:

• organic carbon in all land-dwelling organisms• 500 gigatons (500 billion tons)

• carbon stored in soils• 1,500 gigatons

• 1/3 is inorganic (e.g., CaCO3)

Carbon uptake in terrestrial biosphere depends on biotic factors

• follows diurnal and seasonal cycles• strongest in Northern Hemisphere

• Less land mass in Southern Hemisphere

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TERRESTRIAL BIOLOGICAL CYCLE (CONT.)

Carbon leaves terrestrial biosphere in several ways

• Combustion or respiration of organic carbon releases it rapidly to atmosphere

• Carbon stored in soil can remain there for thousands of years before it is

• washed into rivers by erosion• Released to atmosphere through soil respiration

• increasing temperatures = faster rates of decomposition of organic matter

• resultant increase in flow of CO2

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OCEANIC CARBON CYCLE

Oceans contain the greatest quantity of actively cycled carbon on Earth

• surface layer holds large amounts of dissolved organic carbon

• Rapid exchange with atmosphere

• deep layer concentration of dissolved inorganic carbon (DIC) is about 15% higher than surface layer

• DIC is stored in deep layer for much longer periods

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OCEANIC CARBON CYCLE (CONT.)

Ocean receives carbon via dissolution of atmospheric CO2

• converted by organisms to organic carbon via photosynthesis

Also enters via rivers as dissolved organic carbon

• exchanged throughout food chain or • precipitated into ocean's deeper carbon rich layers

• as dead soft tissue

• in shells as calcium carbonate (CaCO3)

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OCEANIC CARBON CYCLE (CONT.)

Oceanic absorption of CO2 is important form of carbon sequestering

• Limiting human-caused rise of atmospheric CO2

Increased CO2 absorption makes water more acidic

• affects ocean ecosystems • increasing oceanic acidity reduces biological precipitation of

calcium carbonate

• decreases the ocean's capacity to absorb carbon dioxide• damages coral reefs

• Less CO2 absorbed

• Reduced biodiversity

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GEOLOGICAL CARBON CYCLE

• Operates slowly compared to other parts of global carbon cycle

• Important determinant of atmospheric carbon

• Thereby determinant of global temperatures

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GEOLOGICAL CARBON CYCLE (CONT)

Organic carbon stored in geosphere remains for millions of years

Most of Earth's carbon is stored inertly in lithosphere

• Some carbon in earth's mantle has been there since Earth formed

• 80% in geosphere is limestone • From sedimentation of CaCO3 stored in shells of marine

organisms

• 20% is stored as kerogens • formed via sedimentation and burial of terrestrial

organisms under high heat and pressure

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GEOLOGICAL CARBON CYCLE (CONT.)

How carbon leaves the geosphere

• CO2 is released during metamorphosis of carbonate rocks when they are subducted into mantle

• Released to atmosphere and ocean through volcanoes and hotspots

• Removed by humans through extraction of kerogens (fossil fuels)

• fossil fuels are burned to release energy• stored carbon is emitted to atmosphere

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HUMAN DISRUPTION OF CARBON CYCLING

Human activity has modified carbon cycle

• by affecting its component's functions • by directly adding carbon to atmosphere

Human-caused land use/land cover change (LUCC) has led to loss of biodiversity

• lowers ecosystems‘ ability to remove carbon from atmosphere

• directly leads to release of carbon from terrestrial ecosystems to atmosphere

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HUMAN DISRUPTION OF CARBON CYCLING (CONT)

Deforestation

• removes forests holding large amounts of carbon

• replaces them with agricultural or urban areas

• store comparatively small amounts of carbon

• more carbon stays in atmosphere

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HUMAN DISRUPTION OF CARBON CYCLING (CONT.)

Other human-caused changes•Air pollution

• damages plants • damages soils

•Agriculture and land use • higher erosion rates • lower soil carbon • decreased plant productivity

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HUMAN DISRUPTION OF CARBON CYCLING (CONT.)

Higher atmospheric CO2 levels

•Higher temperatures • Increased decomposition in soil

•More rapid return of CO2 to atmosphere

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HUMAN DISRUPTION OF CARBON CYCLING (CONT.)

Higher ocean temperatures

•more CO2 and acidic run-off change ocean chemistry

•damage coral reefs• Less CO2 absorbed

• Reduced biodiversity

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HUMAN DISRUPTION OF CARBON CYCLING (CONT.)

Burning fossil fuels transfers carbon from geosphere to atmosphere

• Began on large scale 150-200 years ago (start of “industrial revolution”)

• Much of fossil fuel reserves already consumed• Demand and amount burned are constantly increasing

• Rapid release of carbon stored up over 400 million years

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AN EXAMPLE…

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ANNUAL EMISSIONS FROM THIS EGU (1 METRIC TON = 2,200 POUNDS)

Total Facility Emissions in metric tons CO2e

(excluding Biogenic CO2)

• 12,687,836 (27,913,239,000 pounds per year)

Emissions by Gas in metric tons CO2e

• Carbon Dioxide (CO2) • 12,591,661 (27,701,654,000 pounds per year)

• Methane (CH4) • 30,557 (67,225,400 pounds per year)

• Nitrous Oxide (N2O) • 65,618 (144,359,600 pounds per year)

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27,913,239,000 POUNDS CO2E PER YEAR

SOURCE:HTTP://GHGDATA.EPA.GOV/GHGP/MAIN.DO

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CAUSE FOR CONCERN…

• China burns more coal than rest of world

combined

• India rapidly becoming industrialized

• As coal consumption decreases in U.S., coal

companies are exporting coal to Asia

• Reduced consumption in U.S. and Europe is

offset by increased consumption in Asia