Biogeochemical CyclesBiogeochemical Cycles

Closed systemClosed system

The earth is virtually a closed system to The earth is virtually a closed system to everything except energy. Only energy everything except energy. Only energy from the sun enters our atmosphere and from the sun enters our atmosphere and only heat escapes. All other resources only heat escapes. All other resources must recycle.must recycle.

Biogeochemical CyclesBiogeochemical Cycles

What you should knowWhat you should know– Why importantWhy important– Where most of the nutrients are located most Where most of the nutrients are located most

of the time (sink)of the time (sink)– How the cycle worksHow the cycle works– Human impactsHuman impacts

Water/Hydrologic CycleWater/Hydrologic Cycle

Condensation

Precipitation

Runoff, infiltration and percolation

Evaporation, transpiration

Water Cycle – Human ActivitiesWater Cycle – Human Activities

We withdraw large quantities of fresh We withdraw large quantities of fresh water from streams, lakes and water from streams, lakes and undergroundunderground

We clear vegetation from land – increases We clear vegetation from land – increases runoff, reduces infiltration, increases runoff, reduces infiltration, increases flooding, speeds soil erosionflooding, speeds soil erosion

We modify water quality by adding We modify water quality by adding nutrients and other pollutantsnutrients and other pollutants

Carbon CycleCarbon Cycle

Photosynthesis/RespirationPhotosynthesis/Respiration

Carbon CyclesCarbon Cycles

Sinks and sourceSinks and source– Key part of nature’s thermostatKey part of nature’s thermostat

– Ocean – COOcean – CO22 dissolved in water (warm water dissolved in water (warm water

holds less), used by phytoplankton, carbonate holds less), used by phytoplankton, carbonate (CO(CO33 -2-2) and bicarbonate – 2) and bicarbonate – 2ndnd largest largest

– Calcium Carbonate in shells and skeletons Calcium Carbonate in shells and skeletons and limestone rock – largest storehouse of and limestone rock – largest storehouse of carbon (CaCOcarbon (CaCO33))

– Fossil FuelsFossil Fuels

Human ActivitiesHuman Activities

Burning fossil fuels and wood release COBurning fossil fuels and wood release CO22

Clearing trees and plants which absorb Clearing trees and plants which absorb COCO22 in photosynthesis in photosynthesis

Phosphorus CyclePhosphorus Cycle

Phosphorus CyclePhosphorus Cycle

A Sedimentary Cycle - most phosphorus A Sedimentary Cycle - most phosphorus found in rocks as phosphate salts It is found in rocks as phosphate salts It is released by the process of weatheringreleased by the process of weatheringBecause supply small in many soils it a Because supply small in many soils it a limiting factor for plant growth on landlimiting factor for plant growth on landHuman ImpactsHuman Impacts– Mining phosphorus to make fertilizerMining phosphorus to make fertilizer– Cut down tropical trees which increases runoffCut down tropical trees which increases runoff– Disrupt aquatic systems with runoffDisrupt aquatic systems with runoff

Nitrogen CycleNitrogen Cycle

Nitrogen CycleNitrogen Cycle

Atmosphere is 78% Nitrogen (N2)Atmosphere is 78% Nitrogen (N2)Crucial component in proteins, vitamins, DNA Crucial component in proteins, vitamins, DNA and RNAand RNANitrogen fixation – Bacteria converts N2 to Nitrogen fixation – Bacteria converts N2 to ammonia NHammonia NH33 which dissolves to form which dissolves to form ammonium NHammonium NH44

Nitrification I – Bacteria convert NHNitrification I – Bacteria convert NH44++ to Nitrite to Nitrite

NONO22--

Nitrification II – Bacteria convert NONitrification II – Bacteria convert NO22-- to NO to NO33

-- which is assimilated by plantswhich is assimilated by plants

Nitrogen CycleNitrogen Cycle

Ammonification – bacteria converts NHAmmonification – bacteria converts NH33

from decomposition which dissolves to from decomposition which dissolves to form NHform NH44

++. This is then reconverted by . This is then reconverted by

Nitrification I and II.Nitrification I and II.

Denitrification – bacteria – converts NODenitrification – bacteria – converts NO33 in in

soil to Nsoil to N22

Nitrogen CycleNitrogen Cycle

We add nitric oxide (NO) when we burn We add nitric oxide (NO) when we burn fuel. NO converted to NOfuel. NO converted to NO22 (nitrogen (nitrogen dioxide gas) and HNOdioxide gas) and HNO33 (Nitric acid) which (Nitric acid) which returns as acid deposition.returns as acid deposition.

Add NAdd N22O (nitrous oxide) by anaerobic O (nitrous oxide) by anaerobic decomposition of wastes and commercial decomposition of wastes and commercial fertilizers – depletes ozone in stratospherefertilizers – depletes ozone in stratosphereRelease nitrogen through destruction of Release nitrogen through destruction of forests grassland and wetlandsforests grassland and wetlands

Nitrogen CycleNitrogen Cycle

Upset aquatic system due to nitrates in Upset aquatic system due to nitrates in agricultural runoff and discharges from agricultural runoff and discharges from sewage plantssewage plants

Remove nitrogen from topsoil when we Remove nitrogen from topsoil when we harvest nitrogen rich crops, irrigate crops, harvest nitrogen rich crops, irrigate crops, burn or clear grasslands and forestsburn or clear grasslands and forests

Input nitrogen into air, water and soilInput nitrogen into air, water and soil

Sulfur CycleSulfur Cycle

Sulfur enters atmosphere as HSulfur enters atmosphere as H22S S

(Hydrogen sulfide), volcanoes and (Hydrogen sulfide), volcanoes and decomposition from swamps, SOdecomposition from swamps, SO22 (sulfur (sulfur

dioxide) from volcanoes, SOdioxide) from volcanoes, SO442-2- (sulfate) (sulfate)

from sea spray, dust storms and forest from sea spray, dust storms and forest fires.fires.

SOSO22 - combines with water to form sulfuric - combines with water to form sulfuric

acid (Hacid (H22SOSO44) to form acid deposition) to form acid deposition

Sulfur CycleSulfur Cycle

Human ImpactHuman Impact– Burn sulfur-containing coal and oil to produce Burn sulfur-containing coal and oil to produce

electric powerelectric power– Refine sulfur-containing petroleum to make Refine sulfur-containing petroleum to make

gasoline, heating oil, and other useful gasoline, heating oil, and other useful productsproducts

– Convert sulfur containing metallic minerals Convert sulfur containing metallic minerals ores into free metals such as copper, lead, ores into free metals such as copper, lead, and zincand zinc

The EndThe End