1. Biogeochemical Cycles

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

3. Biogeochemical Cycles What you should know –Why important –Where most of the nutrients are located most of the time (sink) –How the cycle works –Human impacts

4. Water/Hydrologic Cycle Condensation Precipitation Runoff, infiltration and percolation Evaporation, transpiration

5. Water Cycle – Human Activities We withdraw large quantities of fresh water from streams, lakes and underground We clear vegetation from land – increases runoff, reduces infiltration, increases flooding, speeds soil erosion We modify water quality by adding nutrients and other pollutants

6. Carbon Cycle

7. Photosynthesis/Respiration

8. Carbon Cycles Sinks and source –Key part of nature’s thermostat –Ocean – CO 2 dissolved in water (warm water holds less), used by phytoplankton, carbonate (CO 3 -2 ) and bicarbonate – 2 nd largest –Calcium Carbonate in shells and skeletons and limestone rock – largest storehouse of carbon (CaCO 3 ) –Fossil Fuels

9. Human Activities Burning fossil fuels and wood release CO 2 Clearing trees and plants which absorb CO 2 in photosynthesis

10. Phosphorus Cycle

11. A Sedimentary Cycle - most phosphorus found in rocks as phosphate salts It is released by the process of weathering Because supply small in many soils it a limiting factor for plant growth on land Human Impacts –Mining phosphorus to make fertilizer –Cut down tropical trees which increases runoff –Disrupt aquatic systems with runoff

12. Nitrogen Cycle

13. Atmosphere is 78% Nitrogen (N2) Crucial component in proteins, vitamins, DNA and RNA Nitrogen fixation – Bacteria converts N2 to ammonia NH 3 which dissolves to form ammonium NH 4 Nitrification I – Bacteria convert NH 4 + to Nitrite NO 2 - Nitrification II – Bacteria convert NO 2 - to NO 3 - which is assimilated by plants

14. Nitrogen Cycle Ammonification – bacteria converts NH 3 from decomposition which dissolves to form NH 4 +. This is then reconverted by Nitrification I and II. Denitrification – bacteria – converts NO 3 in soil to N 2

15. Nitrogen Cycle We add nitric oxide (NO) when we burn fuel. NO converted to NO 2 (nitrogen dioxide gas) and HNO 3 (Nitric acid) which returns as acid deposition. Add N 2 O (nitrous oxide) by anaerobic decomposition of wastes and commercial fertilizers – depletes ozone in stratosphere Release nitrogen through destruction of forests grassland and wetlands

16. Nitrogen Cycle Upset aquatic system due to nitrates in agricultural runoff and discharges from sewage plants Remove nitrogen from topsoil when we harvest nitrogen rich crops, irrigate crops, burn or clear grasslands and forests Input nitrogen into air, water and soil

17. Sulfur Cycle Sulfur enters atmosphere as H 2 S (Hydrogen sulfide), volcanoes and decomposition from swamps, SO 2 (sulfur dioxide) from volcanoes, SO 4 2- (sulfate) from sea spray, dust storms and forest fires. SO 2 - combines with water to form sulfuric acid (H 2 SO 4 ) to form acid deposition

18. Sulfur Cycle Human Impact –Burn sulfur-containing coal and oil to produce electric power –Refine sulfur-containing petroleum to make gasoline, heating oil, and other useful products –Convert sulfur containing metallic minerals ores into free metals such as copper, lead, and zinc

19. The End