Biogeochemical Cycles Reviewer Carbon Cycle

Basic building block of life (carbohydrates, fats,

Defined as the movement of elements. Bio-
biological organisms (bacteria, plants, and animals), protein, nucleic acids) ALSO found in 𝐶𝑂2 that makes
up less than 1% of the atmosphere.
Geo-involving geological processes like weathering of
rocks, chemical refers to chemical processes such Terms in carbon cycle:
as formulation of molecules.
Plants Matter: atmospheric carbon is removed
KEY ELEMENTS: hydrogen, oxygen, carbon, through photosynthesis (incorporation of carbon in
nitrogen, phosphorous, and sulfur plant structures and compounds).
Water Cycle Terrestrial biosphere: Forest stores 86% of above-
ground carbon, 73% of soil carbon (carbon found in
The process where water goes through different
soil).
states (frozen, ice or water
Oceans: Removal of dissolved inorganic carbon:
vapor)
basic water, too much carbon: acidification of water
Processes
Sedimentary deposits: Limestone as the largest
Evaporation: Water to gas from water- reservoir of carbon and carbon trapped in fossil fuels.

bodies (lakes, rivers, oceans, seas, etc.) Burning: Burning of fossil fuels, vehicle & industrial
factory emissions.
Transpiration: occurs mostly in the day, water from
plants transferred to the atmosphere. Weatherization: weathering (breakdown from
natural elements- rain, wind, sunlight) releases 𝐶𝑂2
Evapotranspiration (combination of the two)
and carbonic acid.
Condensation: water vapor condenses to airborne
Human Impact (Industrial Rev) on Carbon Cycle-
particles creating dew/ fog/ clouds.
Before Industrial revolution, transfer rates of 𝐶𝑂2
Frozen water: water trapped in cooler regions of the
from photosynthesis and respiration (including
Earth. Ice, snow.
decay) were balanced.
Precipitation: “rain” any or all forms of water falls to
1) More 𝑪𝑶𝟐 deposited than removed.
the ground. Can be raindrops or ice-crystal
2) Increase caused by burning wood & fossil fuels
formations (snow).
3) Deforestation
Runoff: Flow of water from drainage basin or
Nitrogen Cycle
watershed that falls on the stream or stream
channels. Atmospheric Nitrogen converted to nitrogen
oxides (thru lightning → deposited to soil by rain →
Storage of water on Earth are atmosphere, surface
assimilated by plants & animals → returned as
of the earth and underground.
feces/ decomposed back to elemental nitrogen by
Human Impact on Water Cycle- bacteria)

1) Withdrawing water from lakes, aquifers, and Involves:

rivers: Ground water depletion, saltwater
Nitrogen fixation: Electrical discharge → nitrogen
intrusion
oxides from molecular nitrogen.
2) Clearing of land for agriculture and
urbanization: Increased runoff, decreased Two groups of microorganisms responsible for
infiltration, increased flood risk, accelerated soil nitrogen fixation:
erosion.
3) Destruction of wetlands: Disturbing of natural Acetobacter- found in alkaline soils.
processes purifying water. Clostridium pasteranium- found in acid soils.
4) Pollution of water sources: infectious
agents/diseases Nitrification- ammonia → nitrate/nitrite
5) Building powerplants: Increased thermal Two groups of microorganisms responsible for
pollution nitrification:

Nitrosomonas- oxidize ammonia → nitrite & water

Nitrobacter- oxidize nitrite → nitrate

Assimilation: plants using nitrogen to synthesize Human Impact on Phosphorous Cycle-
amino acids, oils and nucleic acids. Likewise,
- Removal of large amounts of phosphate from the
animals assimilate it thru eating plants and eating
earth for fertilizers disrupt phosphorous cycle.
other animals that eat plants.
- Clearance of tropical forest expose topsoil to
Ammonification: when plant/animals die/ animals
increased erosion, reduces phosphate levels in
excretes, the initial form of nitrogen is found in amino
tropical soils.
acids and nucleic acids. Bacteria & fungi convert
organic nitrogen → Ammonia - Eroded topsoil and fertilizer containing phosphate
ions washed to streams, lakes and oceans cause
Denitrification: Nitrates → gaseous nitrogen, used
increase growth of cyanobacteria, green algae and
by facultative anaerobes (organisms that flourish in
aquatic plants that decrease oxygen in water,
aerobic environment but can breakdown oxygen-
killing other aquatic organisms in the food web.
containing compounds to obtain oxygen in anaerobic
environments, ex. Fungi and bacteria Pseudomonas). Sulfur Cycle
Human Impact on Nitrogen Cycle- Sulfur (S)
1) Extensive cultivation of legumes (soy, alfalfa • (Elemental/pure) sulfur is found in
and c underground deposits or near natural
2) lover) hotsprings or volcanoes.
3) Extensive use of chemical fertilizers & • Plays a vital role in organisms, particularly an
pollution of vehicles and industrial plants. essential component in proteins.
4) Biomass burning • Important determinant of acidity of rainfall,
5) Cattle and feedlots surface water and soil.
6) Industrial process

Phosphorous Cycle
In Lithosphere (earth)
Phosphorous:
- 13th most abundant element in Earth’s crust, 9th
- essential to produce DNA and cell in sediments
membranes, formation of bones and teeth. - Mobilized by slow weathering of rock material.
- A key element in fertilizer. Dissolved in runoff, moves with river water,
- Sourced from rocks that are eroded and deposited as sediments in oceans.
release phosphate ions.
- Does not cycle through the atmosphere. In Hydrosphere (water)
- Cycles slower than water, carbon and - Storage of sulfur in oceans, dissolved through
nitrogen cycle. dissolved sulphate.
• simple biogeochemical cycle, movement of P - Dimethyl sulfide- produced by algal and
through water, the earth’s crust and living bacterial decays in sea water. (most volatile
organisms. sulfur)
• Most phosphorous compounds in the cycle - Highest concentrations in coastal marches
contain phosphate ions or hydrogen phosphate and wetlands
ions which are an important plant nutrient. - 2nd most abundant in rivers w/ concentrations
When phosphate ions are washed away, they are fluctuating highly with seasons and frequent
soaked into the soil where plants gobble it up and drought, flood, and normal flow. Rivers transport
incorporate in their tissues. 110 million tons of sulfur/year to oceans.
Sample cycle: In Soil & Biosphere
Phosphate ions absorbed by soil → consumed by • Major nutrient in biosphere (concentrated
plants, incorporated into tissues→ animal consumes mostly in soil where it enters biosphere
plant with phosphate (transferred to animal’s tissue) through plant uptake)
→ animal dies, decomposing bacteria cycle • Sulfur in soil are mainly as organic or
phosphate back into soil. inorganic compounds.
Note: Phosphates not consumed by plants, in the • Plants take it up as sulphate and is passed
right soil conditions, can turned back into rocks. with the food chain in the biosphere.
• Death and decomposition of animals bring
back sulfate into the soil.
• Anaerobic decomposition in soil releases
organic sulfur as hydrogen sulfide, dimethyl
 sulfide and other organic compounds into the
atmosphere.

In the Atmosphere

Six important sulfur compounds in the atmosphere:

- Carbonyl Sulfide (COS) most abundant,

produced through decomposition process in
soil.

- Carbon disulfide more reactive, similar sources.

- Dimethyl sulfide- most natural gas released

from oceans and its higher concentrations
during the night.

- Hydrogen sulfide- produced in nature during

anaerobic decay & other stagnant water which
maximum concentrations occurring in tropical
forests.

- Sulfur dioxide- Natural source is oxidation of

hydrogen sulfide and its use in combustion of
fossil fuel.

- Sulfate aerosol- largest natural source of

sulphate aerosol particle originates from sea
spray.