Biogeochemical Cycles

Objectives:

• Identify the flow on each biogeochemical cycle.

• Explain the impact that humans

have on the

biogeochemical

cycles.

Biogeochemical cycles

• Biogeochemical cycles: The chemical interactions (cycles) that exist between the atmosphere, hydrosphere, lithosphere, and biosphere.

• Biogeochemical cycles are components of the broader cycle that govern the functioning of planet Earth

Biogeochemical cycles• The transfer of matter involves biological,

geological and chemical processes; hence the name biogeochemical cycles derives. Biogeochemical cycles may also be referred to as cycles of nature because they link together all organisms and abiotic features on earth (see Figure at next slide). Matter is continually recycled among living and abiotic elements on earth.

• biogeochemical cycles facilitate the transfer of matter from one form to another and from one location to another on planet earth. Additionally, biogeochemical cycles are sometimes called nutrient cycles, because they involve the transfer of compounds that provide nutritional support to living organisms.

PathwaysofBiogeochemicalCycles

• Parts that comprise planet earth have been categorized into four spheres (regions). One is the sphere which has life and it is called the biosphere (it is the region occupied by living organisms such as plants, animals, fungi) and the other three spheres are largely devoid of life, they include;

• lithosphere (region occupied by soil, land and the earth crust), atmosphere (air and space) and hydrosphere (areas covered by water such as rivers, lakes and oceans). However, where the biosphere overlaps the lithosphere, atmosphere or hydrosphere, there is a zone occupied by living organisms.

Categories of biogeochemical cycles

• Biogeochemical cycles differ in their pathways, and on this basis the biogeochemical cycles have been categorized into two:

Sedimentary cycles:

Phosphorus cycle Sulfur cycle

Gaseous cycles

Carbon cycle Oxygen cycle

Nitrogen cycle Hydrological cycle

Sedimentary cycles:

• these cycles involve the transportation of matter through the ground to water; that is to say from the lithosphere to the hydrosphere.

Phosphorus cyclePhosphorus is commonly found in water, soil and sediments. Phosphorus cannot be found in air in the gaseous state. This is because phosphorus is usually a liquid at standard temperatures and pressures. Phosphorus is mainly cycled trough water, soil and sediments. However, very small particles in the atmosphere may contain phosphorus or its compounds. Phosphorus moves slowly from deposits on land and in sediments, to living organism , and much more slowly back into the soil and water sediment. The phosphorus cycle is the slowest one of the sedimentary cycles.

Fig. 3-31, p. 77

Dissolvedin Ocean

Water

Marine Sediments Rocks

uplifting overgeologic time

settling out weatheringsedimentation

LandFoodWebs

Dissolvedin Soil Water,Lakes, Rivers

death,decomposition

uptake byautotrophs

agriculture

leaching, runoff

uptake byautotrophs

excretion

death,decomposition

mining Fertilizer

weathering

Guano

MarineFoodWebs

The cycle basically starts out in the earth’s soil. The soil contains phosphate and when something grows out of the soil it should have phosphate as well.

When the plants grow they are consumed by herbivore and omnivore animals

The animal’s waste or the animal’s body when it dies becomes detritus.

Detritus is non-living organic material. When the detritus goes deep into the soil, detritivores in the soil decompose and become the soil’s phosphate and the cycle repeats.

Sulfur cycle• Sulfur in its natural form is a solid, and

restricted to the sedimentary cycle in this form. It is transported by physical processes like wind, erosion by water, and geological events like volcanic eruptions. However, in its compounds such as sulfur dioxide, sulfuric acid, salts of sulfate or organic sulfur, sulfur can be moved from the ocean to the atmosphere, to land and then to the ocean through rainfall and rivers.

Fig. 3-32, p. 78

Hydrogen sulfide

Sulfur

Sulfate salts

Decaying matter

Animals

Plants

Ocean

IndustriesVolcano

Hydrogen sulfideOxygen

Dimethyl sulfide

Ammoniumsulfate

Ammonia

Acidic fog and precipitationSulfuric acid

WaterSulfurtrioxide

Sulfur dioxide

Metallicsulfidedeposits

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.

Gaseous cycles

• these involve the transportation of matter through the atmosphere. Common example of gaseous cycles are:

Carbon cycle

• Carbon is one of the most important elements that sustain life on earth. Carbon dioxide and methane gases (compounds of carbon) in the earth's atmosphere has a substantial effect on earth's heat balance. It absorbs infrared radiation and hence may contribute to global warming and climate change.

MARINE CARBON CYCLE

Slide 35Slide 35Slide 35

Diffusion between atmosphere and ocean

Carbon dioxidedissolved in ocean water

Marine food websProducers, consumers,

decomposers, detritivores

Marine sediments, includingformations with fossil fuels

Combustion of fossil fuels

incorporation into sediments

death, sedimentation

uplifting over geologic time

sedimentation

photosynthesis aerobic respiration

Figure 4-29aPage 78

Slide 36Slide 36Slide 36

photosynthesis aerobic respirationTerrestrial

rocks

Soil water(dissolved

carbon)

Land food websproducers, consumers,

decomposers, detritivores

Atmosphere(most carbon is in carbon dioxide)

Peat,fossil fuels

combustion of wood (for clearing land; or for fuel

sedimentation

volcanic action

death, burial, compaction over geologic timeleaching

runoff

weathering

Figure 4-29b Page 79

Combustion of fossil

fuels

TERRESTRIAL CARBON CYCLE

Carbon Cycle DiagramCarbon in Atmosphere

Plants use carbon to make

food

Animals eat plants and

take in carbon

Plants and animals die

Decomposers break down dead things, releasing

carbon to atmosphere and

soil

Bodies not decomposed —

after many years, become

part of oil or coal deposits

Fossil fuels are burned; carbon

is returned to atmosphere

Carbon slowly released from

these substances returns to

atmosphere

The Carbon Cycle

• Fossil fuels release carbon stores very slowly

• Burning anything releases more carbon into atmosphere — especially fossil fuels

• Increased carbon dioxide in atmosphere increases global warming

• Fewer plants mean less CO2 removed from atmosphere

Human Impact

Nitrogen cycle

• Nitrogen gas is the most abundant element in the atmosphere and all the nitrogen found in terrestrial ecosystems originate from the atmosphere. The nitrogen cycle is by far the most important nutrient cycle for plant life.

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 3-30Figure 3-30

Oxygen cycleOxygen cycle• The oxygen cycle describes the

movement of oxygen within and between its three main reservoirs: the atmosphere, the biosphere, and the lithosphere. The main driving factor of the oxygen cycle is photosynthesis and because of this, oxygen and carbon cycles are usually linked and the two cycles are collectively called oxygen-carbon cycle.

Fig. 3-26, p. 72

PrecipitationPrecipitation

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

RunoffSurface runoff

(rapid)

Surface runoff (rapid)

Photosynthesis

respiration

Rabbit eats food, breaks it down and releases CO2.

Plant uses CO2 to make food.

Rabbit gives off CO2, which is taken in by the

plant.

Plant gives off O2, which is taken in by the

rabbit.

How are photosynthesis and cellular respiration similar?

•

• Photosynthesis uses carbon dioxide and produces oxygen.

• Cellular respiration uses oxygen and produces carbon dioxide.

All Animals and Other Consumers Use Oxygen

• We use oxygen to break down simple sugar and release energy.

• This can be done through respiration or fermentation.

• Animals mainly use respiration.

OXYGEN-CARBON DIOXIDE CYCLE.

Hydrological cycle• This is some times called the water cycle.

Water is the most important chemical of life for all living organisms on earth. Water in the atmosphere is usually in form of vapor but condenses to liquid water and can solidify when temperatures are 00C to form ice. Ninety three percent of water on earth is in solid state mainly comprising the ice caps and glaciers of Polar Regions.

• The earth has a limited amount of water. That water keeps going around and around and around and around and (well, you get the idea) in what we call the "Water Cycle". This cycle is made up of a few main parts:

• Evaporation or (Transpiration)• Condensation• Precipitation• Accumulation or (Collection)• Ground Water• Saturation• Infiltration

• Evaporation is when the sun heats up water in rivers, lakes or the ocean and turns it into vapor or steam. The water vapor or steam leaves the river, lake or ocean and goes into the air.

Evaporation

• Water vapor in the air gets cold and changes back into liquid, forming clouds. This is called condensation.

• You can see this at home when you take a shower and the windows and mirrors in the bathroom fog up. You can also do this by breathing on a mirror.

Condensation

• Precipitation occurs when so much water has condensed that the air cannot hold it anymore. The clouds get heavy and water falls back to the earth in the form of rain, hail, sleet or snow.

Precipitation

• When water falls back to earth as precipitation, it may fall back in the oceans, lakes or rivers or it may end up on land. When it ends up on land, it will either soak into the earth (infiltration) and becomes part of the “ground water” that plants and animals use to drink or it may run over the soil and collect in the oceans, lakes or rivers where the cycle starts all over again.

Accumulation

HUMAN IMPACTS TO WATER CYCLE

1. Water withdrawal from streams, lakes and groundwater. (salt water intrusion and groundwater depletion)

2. Clear vegetation from land for agriculture, mining, road and building construction. (nonpoint source runoff carrying pollutants and reduced recharge of groundwater)

3. Degrade water quality by adding nutrients(NO2, NO3, PO4) and destroying wetlands (natural filters).

4. Degrade water clarity by clearing vegetation and increasing soil erosion.

Nature of elements transported in biogeochemical cycles

• When living organisms die and decay, their body structures disintegrate and may be reduced to constituent molecules. Depending on the region where disintegration of the organisms occurred, the component molecular elements then join the biogeochemical cycle.

Elements transported in the biogeochemical cycles have been categorized as:

• 1. Micro elements – these are elements required by living organisms in smaller amounts. Examples of such elements include boron used mainly by green plants, copper used by some enzymes and molybdenum used by nitrogen-fixing bacteria.

• 2. Macro elements – these are elements required by living organisms in larger amounts. Examples of such elements include carbon, hydrogen, oxygen, nitrogen, phosphorous, sulfur.

The importance of biogeochemical cycles

• Biogeochemical cycles serve a variety of functions at ecosystem level and in ensuring survival of various organisms including humans. Below are some of the importance's of biogeochemical cycles.

Importance'sofBiogeochemicalCycles• enable the transformation of matter from one

form to another.

• enable the transfer of molecules from one locality to another.

• facilitate the storage of elements

• assists in functioning of ecosystems.

• cycles link living organisms with living organisms, living organisms with the non living organisms and nonliving organisms with non living organism.

• regulate the flow of substances.

Thank you for your

attention