Biogeochemical Cycles

Biogeochemical CycleBiogeochemical cycle is a pathway by which a chemical substance moves through both biotic (biosphere) and abiotic (lithosphere, atmosphere, and hydrosphere) compartments of Earth. A cycle is a series of change which comes back to the starting point and which can be repeated.

The term "biogeochemical" tells us that biological, geological and chemical factors are all involved. The circulation of chemical nutrients like carbon, oxygen, nitrogen, phosphorus, calcium, and water etc. through the biological and physical world are known as biogeochemical cycles. In effect, the element is recycled, although in some cycles there may be places (called reservoirs) where the element is accumulated or held for a long period of time (such as an ocean or lake for water).

The CyclesThe 5 biogeochemical cycles are:Water or Hydrologic CycleCarbon CycleNitrogen CyclePhosphorus CycleSulfur Cycle

Water CycleWater cycle is the cycle of evaporation and condensation that controls the distribution of the earth's water as it evaporates from bodies of water, condenses, precipitates, and returns to those bodies of water.

Water CycleWater can be in the atmosphere, on the land, in the ocean, and even underground. It is recycled over and over through the water cycle.  In the cycle, water changes state between liquid, solid (ice), and gas (water vapor).

Most water vapor gets into the atmosphere by a process called evaporation. This process turns the water that is at the top of the ocean, rivers, and lakes into water vapor in the atmosphere using energy from the Sun. Water vapor can also form from snow and ice through the process of sublimation and can evaporate from plants by a process called transpiration.

Water CycleWater can be in the atmosphere, on the land, in the ocean, and even underground. It is recycled over and over through the water cycle.  In the cycle, water changes state between liquid, solid (ice), and gas (water vapor).

Most water vapor gets into the atmosphere by a process called evaporation. This process turns the water that is at the top of the ocean, rivers, and lakes into water vapor in the atmosphere using energy from the Sun. Water vapor can also form from snow and ice through the process of sublimation and can evaporate from plants by a process called transpiration.

Water CycleThe water vapor rises in the atmosphere and cools, forming tiny water droplets by a process called condensation.  Those water droplets make up clouds. If those tiny water droplets combine with each other they grow larger and eventually become too heavy to stay in the air. Then they fall to the ground as rain, snow, and other types of precipitation.

Most of the precipitation that falls becomes a part of the ocean or part of rivers, lakes, and streams that eventually lead to the ocean. Some of the snow and ice that falls as precipitation stays at the Earth surface in glaciers and other types of ice. Some of the precipitation seeps into the ground and becomes a part of the groundwater.

Carbon CycleCarbon cycle are the combined processes, including photosynthesis, decomposition, and respiration, by which carbon as a component of various compounds cycles between its major reservoirs—the atmosphere, oceans, and living organisms.

Carbon CycleCarbon moves from the atmosphere to plants.In the atmosphere, carbon is attached to oxygen in a gas called carbon dioxide (CO2). With the help of the Sun, through the process of photosynthesis, carbon dioxide is pulled from the air to make plant food from carbon.

Carbon moves from plants to animals.Through food chains, the carbon that is in plants moves to the animals that eat them. Animals that eat other animals get the carbon from their food too.

Carbon CycleCarbon moves from plants and animals to the ground.When plants and animals die, their bodies, wood and leaves decay bringing the carbon into the ground. Some become buried miles underground and will become fossil fuels in millions and millions of years.

Carbon moves from living things to the atmosphere.Each time you exhale, you are releasing carbon dioxide gas (CO2) into the atmosphere. Animals and plants get rid of carbon dioxide gas through a process called respiration.

Carbon CycleCarbon moves from fossil fuels to the atmosphere when fuels are burned.When humans burn fossil fuels to power factories, power plants, cars and trucks, most of the carbon quickly enters the atmosphere as carbon dioxide gas. Each year, five and a half billion tons of carbon is released by burning fossil fuels. Of the huge amount of carbon that is released from fuels, 3.3 billion tons enters the atmosphere and most of the rest becomes dissolved in seawater.

Carbon moves from the atmosphere to the oceans. The oceans, and other bodies of water, soak up some carbon from the atmosphere.

Nitrogen CycleNitrogen cycle the continuous sequence of natural processes by which nitrogen in the atmosphere and nitrogenous compounds in the soil are converted, as by nitrification and nitrogen fixation, into substances that can be utilized by green plants and then returned to the air and soil as a result of denitrification and plant decay.

Nitrogen CycleNitrogen fixation: The conversion of atmospheric nitrogen into nitrogenous compounds by bacteria (Rhizobia) found in the root nodules of legumes and certain other plants, and in the soil.

Assimilation:Plants take nitrogen from the soil, by absorption through their roots in the form of their nitrate ions or ammonium ions. All nitrogen obtained by animals can be traced back to the eating of plants.

Nitrogen CycleNitrogen fixation: The conversion of atmospheric nitrogen into nitrogenous compounds by bacteria (Rhizobia) found in the root nodules of legumes and certain other plants, and in the soil.

Assimilation:Plants take nitrogen from the soil, by absorption through their roots in the form of their nitrate ions or ammonium ions. All nitrogen obtained by animals can be traced back to the eating of plants.

Nitrogen CycleAmmonification:When a plant or animal dies, or an animal expels waste, the initial form of nitrogen is organic. Bacteria, or fungi in some cases, convert the organic nitrogen within the remains back into ammonium (NH4

+).Nitrification:The oxidation of the ammonium compounds in dead organic material into nitrites and nitrates by soil nitrobacteria, making nitrogen available to plants.Nitrosomonas species converts ammonia to nitrites (NO2

-). Nitrobacter species are responsible for the oxidation of the nitrites into nitrates (NO3

-).

Nitrogen CycleDenitrification:Process occurs when nitrates (NO3

-) reduced to gaseous nitrogen (N2), as by bacterial action on soil.

Phosphorus CycleThe phosphorus cycle is the process in which phosphorus travels from its main source of rocks through ecosystems to living organisms.

Phosphorus CyclePhosphate MiningPhosphate rock is found from 15-50ft below the ground in a phosphate matrix. The matrix is comprised of phosphate pebbles, sand, and clay. The sandy layer is removed by electrically operated drag lines. Then high pressure water guns turn the sandy layer into a mixture called slurry. The slurry is then sent to a processing facility. After the phosphate is collected it is use for common human products, such as fertilizer.

IngestionAnimals eat plants and other organic materials containing phosphates.

Phosphorus CycleExcretionAnimals are a key element in the phosphorous cycle. They consume plants containing phosphorous and then excrete. The excrement is then turned into run-off in water and decomposed in either the ground or nearby water bodies by decomposers.

DecompositionOrganic material breaks down, returning organic phosphorus to the soil as inorganic phosphorus. The inorganic phosphorus then enters the oceans through runoff and erosion of rocks containing phosphorus.

Phosphorus CycleBurial and CompactionAfter decomposition organisms are compacted into sediments to form rock. This then allows phosphorous to become trapped inside rocks until geologic uplift occurs.

Geologic UpliftUplift exposing underground rocks to the surface allows phosphorus to be made available to under go the phosphorus cycle.

Phosphorus CycleErosionRocks or soil are broken down, transporting phosphorus across land or into water.

AbsorptionPlants absorb phosphates through their roots.

Sulfur Cycle Sulfur cycle is the natural cycle which includes the mineralization of organic sulfur to sulfide, oxidation of this to sulfate, and reduction of this to sulfide followed by microbial incorporation of this into organic compounds.

Sulfur CycleThe sulfur cycle includes both gases and solids.

Hydrogen sulfide gas (H2S) is released into the atmosphere by volcanic eruptions, hot springs , and the anaerobic decay of sulfur-containing biological material in swamps, bogs, and tidal flats.

Certain marine algae produce dimethyl sulfide, (CH3)2S, a volatile compound that enters the atmosphere as tiny droplets.

Sulfur dioxide gas is released into the atmosphere by volcanoes and also forms when dimethyl sulfide reacts with oxygen gas.

The burning of fossil fuels, such as coal and oil releases sulfur dioxide into the atmosphere.

Sulfur CycleSulfur dioxide reacts with atmospheric oxygen to produce sulfur trioxide (SO3).

Some sulfur trioxide reacts with tiny water droplets to form sulfuric acid (H2SO4).

Sulfur oxides also react with ammonia to produce tiny particles of ammonium salts.

The winds carry droplets of sulfuric acid and particles of sulfate salts, which then fall to the earth in acid deposition.

By adding sulfur compounds to the air, the use of fossil fuels increases the rate of acid deposition.

All living things require sulfur to make proteins.

Sulfur CyclePlants get sulfur by taking up ions of sulfate salts (SO4

2-) from the soil.Animals get sulfur by eating plants, and all living things release sulfur compounds when they decay.

Decomposition releases sulfate salts (SO4

2-), which can be taken up by plants, as well as gaseous hydrogen sulfide.

Sulfur CycleSome hydrogen sulfide enters the atmosphere.

But when decay occurs in an oxygen-free environment, anaerobic bacteria break down hydrogen sulfide and release sulfur gas (S2).

Oxygen-requiring bacteria can incorporate sulfur into sulfate salts, which can be taken up by plants and enter the food chain once again.