Biogeochemical Cycles

Objectives:

Identify and describe the flow of nutrients in each biogeochemical cycle.

Explain the impact that humans have on the biogeochemical cycles.

Environmental Spheres

Elements of Life

Organic = carbon-based molecules Examples: C6H12O6, CH4 Inorganic = molecules without carbon–carbon or carbon–hydrogen bonds Examples: NaCl, NH4, H2SO4

Elements of Life

92 naturally occurring elements Elements Found in Living Organisms CHNOPS (macronutrients) Carbon, Hydrogen, Nitrogen, Oxygen, Phosphorus, Sulfur

78% Nitrogen

21% Oxygen

<0.04% Carbon Dioxide

Atmospheric Gases

What Sustains Life on Earth?

Solar energy, the cycling of matter, and gravity sustain the earth’s life.

Figure 3-7

Two Secrets of Survival: Energy Flow and Matter Recycle

An ecosystem survives by a combination of energy flow and matter recycling.

Figure 3-14

MATTER CYCLING IN ECOSYSTEMS

Nutrient Cycles: Global Recycling Global Cycles recycle nutrients through the

earth’s air, land, water, and living organisms. Nutrients are the elements and compounds that

organisms need to live, grow, and reproduce. Biogeochemical cycles move these substances

through air, water, soil, rock and living organisms.

Fig. 3-26, p. 72

Precipitation Precipitation

Transpiration

Condensation

Evaporation

Ocean storage

Transpiration from plants

Precipitation to land

Groundwater movement (slow)

Evaporation from land Evaporation

from ocean Precipitation to ocean

Infiltration and Percolation

Rain clouds

Runoff Surface runoff

(rapid)

Surface runoff (rapid)

The Water Cycle

Effects of Human Activities on Water Cycle

We alter the water cycle by: Withdrawing large amounts of freshwater. Clearing vegetation and eroding soils. Polluting surface and underground water. Contributing to climate change.

The Carbon Cycle

• Plants take in CO2 because they need carbon and oxygen to use in photosynthesis.

• Through photosynthesis plants make carbohydrates and other substances e.g. protein • When animals eat plants they use some of the carbon containing compounds to grow • Some carbon-containing compounds are used to release energy by respiration.

Fig. 3-27, pp. 72-73

Carbon Cycle

bioh.wikispaces.com

Carbon Cycle

geos.ed.ac.uk

Effects of Human Activities on Carbon Cycle

We alter the carbon cycle by adding excess CO2 to the atmosphere through: Burning fossil fuels. Clearing vegetation

faster than it is replaced.

Figure 3-28

• Living organisms need nitrogen to make proteins

• The air is 79% nitrogen which is inert • Nitrogen fixing changes N2 into a useable

form • This happens by lightning, nitrogen – fixing

bacteria and artificial fertilizers

The Nitrogen Cycle

AIR

N2

AIR

N2

Nitrogen Cycle

bioh.wikispaces.com

Effects of Human Activities on the Nitrogen Cycle

We alter the nitrogen cycle by: Adding gases that contribute to acid rain. Adding nitrous oxide to the atmosphere through

farming practices which can warm the atmosphere and deplete ozone.

Contaminating ground water from nitrate ions in inorganic fertilizers.

Releasing nitrogen into the troposphere through deforestation.

Effects of Human Activities on the Nitrogen Cycle

Human activities such as production of fertilizers now fix more nitrogen than all natural sources combined.

Figure 3-30

The Human System

The Human System

Excessive use of fossil fuels Use of coal or nuclear power Use of agricultural land to produce meats Lack of recycling Excessive use of fertilizers Destruction of tropical rain forests Nutrient overcharge into aquatic ecosystems Production and use of nonbiodegradable

compounds

Fig. 3-31, p. 77

Dissolved in Ocean

Water

Marine Sediments Rocks

uplifting over geologic time

settling out weathering sedimentation

Land Food Webs

Dissolved in Soil Water, Lakes, Rivers

death, decomposition

uptake by autotrophs

agriculture

leaching, runoff

uptake by autotrophs

excretion

death, decomposition

mining Fertilizer

weathering

Guano

Marine Food Webs

The Phosphorus Cycle

Effects of Human Activities on the Phosphorous Cycle

We remove large amounts of phosphate from the earth to make fertilizer.

We reduce phosphorous in tropical soils by clearing forests.

We add excess phosphates to aquatic systems from runoff of animal wastes and fertilizers.

Fig. 3-32, p. 78

Hydrogen sulfide

Sulfur

Sulfate salts

Decaying matter

Animals

Plants

Ocean

Industries Volcano

Hydrogen sulfide Oxygen

Dimethyl sulfide

Ammonium sulfate

Ammonia

Acidic fog and precipitation Sulfuric acid

Water Sulfur trioxide

Sulfur dioxide

Metallic sulfide deposits

The Sulfur Cycle

Effects of Human Activities on the Sulfur Cycle

We add sulfur dioxide to the atmosphere by: Burning coal and oil Refining sulfur containing petroleum. Convert sulfur-containing metallic ores into free

metals such as copper, lead, and zinc releasing sulfur dioxide into the environment.

What is the ultimate interface of all 4 reservoirs for these cycles?

Soil