The effect of Composition and Temperature on Hydrolytic Degradation

A commonly cited example is the

A commonly cited example is the water cyclewater cycle..

Biochemical Cycles Biochemical Cycles

• All chemical elements occurring in organisms are part of biogeochemical cycles. In addition to

being a part of living organisms, these chemical elements also cycle through abiotic factors of ecosystems such as water (hydrosphere), land ( lithosphere), and the air (atmosphere). The living factors of the planet can be referred to

collectively as the biosphere. All the nutrients—

such as carbon, nitrogen, oxygen, phosphorus, and sulfur—used in ecosystems by living

organisms operate on a closed system; therefore, these chemicals are recycled instead of being lost and replenished constantly such as in an open

system.

Biochemical Cycles (Cont) Biochemical Cycles (Cont)

• The flow of energy in an ecosystem is an open system; the sun constantly gives the planet

energy in the form of light while it is eventually used and lost in the form of heat throughout the trophic levels of a food web. Carbon is used to make carbohydrates, fats, and proteins, the

major sources of food energy. These compounds are oxidized to release carbon dioxide, which can be captured by plants to make organic

compounds. The chemical reaction is powered by the light energy of the sun.

Biochemical Cycles (Cont) Biochemical Cycles (Cont)

• It is possible for an ecosystem to obtain energy without sunlight. Carbon must be combined with hydrogen and oxygen in order to be utilized as an energy source, and this process depends on

sunlight. Ecosystems in the deep sea, where no sunlight can penetrate, use sulfur. Hydrogen

sulfide near hydrothermal vents can be utilized

by organisms such as the giant tube worm. In the sulfur cycle, sulfur can be forever recycled as a

source of energy. Energy can be released through the oxidation and reduction of sulfur compounds (e.g., oxidizing elemental sulfur to sulfite and

then to sulfate).

Important Cycles Important Cycles

• The most well-known and important biogeochemical cycles, for example, include the carbon cycle, the nitrogen cycle, the oxygen cycle, the phosphorus cycle, the sulfur cycle

and the water cycle. There are many biogeochemical cycles that are currently being studied for the first time as climate change and human impacts are drastically changing the

speed, intensity, and balance of these relatively unknown cycles. These newly studied biogeochemical cycles include the mercury cycle and the human-caused cycle of atrazine, which may affect certain species.

• Biogeochemical cycles always involve hot equilibrium states: a balance in the cycling of the element between compartments. However, overall balance may involve compartments distributed on a global scale.

The Nitrogen Cycle The Nitrogen Cycle

• Nitrogen comprises 78.08 % of the atmosphere making it the largest constituent of the gaseous envelope that surrounds the Earth. Nitrogen is important in the make up of

organic molecules like proteins.

Unfortunately, nitrogen is inaccessible to most living organisms. Nitrogen must be

“fixed” by soil bacteria living in association with the roots of particular plant like legumes, clover, alfalfa, soybeans, peas, peanuts, and beans. Living on

nodules around the roots of legumes, the bacteria chemically combine

nitrogen in the air to form nitrates (NO3) and ammonia (NH3) making it available to plants. Organisms that feed on the plants ingest the nitrogen and release it in organic wastes.

Denitrifying bacteria frees the nitrogen from the wastes returning it to the atmosphere.

Nitrogen Cycles Nitrogen Cycles

Oxygen Cycle Oxygen Cycle

• Oxygen is the second most abundant gas in Earth’s

atmosphere and an essential element of most organic

molecules. Though oxygen is passed between the lithosphere, biosphere and atmosphere in a variety of ways,

• photosynthesizing vegetation is largely responsible for oxygen found in the atmosphere.

• The cycling of oxygen through the Earth system is also accomplished by weathering of carbonate rock.

• Some atmospheric oxygen is bound to water molecules from plant transpiration and

evaporation.

• Oxygen is also bound to carbon dioxide and released into the atmosphere during animal respiration.

CARBON CYCLE CARBON CYCLE

• - Carbon (C) enters the biosphere during photosynthesis:

CO2 + H2O --->

C₆H₁₂O₆ + O₂ + H₂O

- Carbon is returned to the biosphere in

cellular respiration:

O₂ +H₂O + C₆H₁₂O₆

---> CO₂ +H₂O + energy

PHOSPHORUS CYCLE PHOSPHORUS CYCLE

• Facts:

• - Component of DNA, RNA,

ATP, proteins and enzymes - Cycles in a sedimentary cylce

- A good example of how a mineral element becomes part of an organism.

- The source of Phosphorus (P) is rock.

- It is released into the cylce through erosion or mining.

- It is soluble in H2O as phosphate (PO4)

- It is taken up by plant roots, then travels through food chains.

- It is returned to sediment

SULFUR CYCLE SULFUR CYCLE        

• Facts:

• - Component of protein

- Cycles in both a gas and sedimentary cycle.

- The source of Sulfur is the lithosphere(earth's crust.

- Sulfur (S) enters the

atmosphere as hydrogen sulfide (H2S) during fossil fuel combustion, volcanic eruprtions, gas exchange at ocean surfaces, and decomposition.

- H₂S is immediately oxidized to sulfur dioxide (SO2)

- SO2 and water vapor makes H2SO4 ( a weak sulfuric acid),which is then carried to Earth in rainfall.

- Sulfur in soluble form is taken up by plant roots and incorporated into amino acids such as cysteine. It then travels through the food chain and is eventually released

through decomposition.