APES Cycle and Pollutants Review

Carbon Cycle

Involves photosynthesis (plants absorb CO₂), respiration (release of CO₂), combustion (burning fossil fuels releases CO₂), fossil fuel formation, and decomposition.

Nitrogen fixation

(N₂ gas → usable ammonia by bacteria/lightning)

Nitrification

(ammonia → nitrites → nitrates)

Assimilation

(plants absorb nitrates)

Ammonification

(organic matter → ammonia)

Denitrification

(nitrates → N₂ gas back to atmosphere)

Phosphorus Cycle

Unlike carbon and nitrogen, it does not involve the atmosphere.

Major reservoirs

are rocks; cycles through weathering, erosion, and sediment deposition.

Hydrologic (Water) Cycle

Key processes evaporation, condensation, precipitation, infiltration, transpiration (plants releasing water vapor).

Primary Pollutants

(directly emitted from a source like vehicles or factories)

CO (carbon monoxide)

1st– incomplete combustion of fossil fuels.

NOx (nitrogen oxides)

1st– from cars and power plants.

SO₂ (sulfur dioxide)

1st – from burning coal and oil.

PM (particulate matter)

1st – dust, ash, soot.

VOC (volatile organic compounds)

1st – evaporate easily, contribute to smog. (form when primary pollutants react in the atmosphere)

Tropospheric Ozone (O₃)

2nd – formed when NOx and VOCs react in sunlight.

Photochemical Smog

2nd – from VOCs + NOx + sunlight → forms ozone and other compounds.

Acid Rain

2nd – SO₂ and NOx react with water vapor → sulfuric and nitric acid.