1. BIOGEOCHEMICAL
CYCLES

2. What are Biogeochemical Cycles?
Bio – life
Geo – Earth
- literally “life-earth-chemical” cycle
- also called nutrient cycles

3. Biogeochemical Cycles cont’d
natural processes that recycle nutrients from the non-living environment to living organisms, then back to the non-living environment
A nutrient is a substance an organism needs to live, grow or reproduce e.g., carbon, oxygen and nitrogen

4. Biogeochemical Cycles
Macronutrients
- nutrients needed in large amounts
- make up > 95% of all organism’s mass
- e.g., C, N, P, K, H, O
Micronutrients
- the 30+ elements required by organisms in small amounts - e.g., iron, zinc

5. Carbon Cycle Carbon (C)
- basic building block of carbohydrates, fats, proteins and nucleic acids (such as DNA)
- the main source of C for organisms is CO2 from the atmosphere or dissolved in surface water

6. Carbon Cycle cont’d The 3 largest reservoirs of C are :
1. earth’s rocks
2. fossil fuels
3. ocean beds

7. Carbon Cycle cont’d Atmosphere (CO2) Diffusion Photosynthesis
Respiration, Decomposition
Combustion
Plants
Animals
Consumption
Burial and compaction
Oceans
Fossil fuels
Limestone

8. CARBON CYCLE
Atmosphere 750
Vegetation 610
Soils 1580

9. Carbon Cycle cont’d Two ways that humans have disturbed the cycle:
Forest & brush clearing
2. Burning fossil fuels and wood

10. Carbon Cycle cont’d
These activities have resulted in an increase in the level of carbon dioxide in the atmosphere.
0.036% of the atmosphere is carbon dioxide gas
Increases in the level of carbon dioxide linked to global warming

11. Nitrogen Cycle Nitrogen
- organisms need N to make proteins, DNA and other nitrogen compounds
- nitrogen gas, N2,makes up 78% of atmospheric volume
- N2 cannot be used directly by plants or animals

13. Nitrogen Cycle cont’d Ways Humans Intervene in N Cycle:
1. Adding excess nitrate and ammonia to aquatic ecosystems in agricultural runoff and discharge of municipal sewage. Leads to eutrophication.
2. Emitting large quantities of nitric oxide when fuel is burned. Leads to acid rain.

14. Phosphorus Cycle
is the movement of P through water, earth’s crust and living organisms
P, mainly in the form of phosphates, is an essential plant & animal nutrient
P is found is essential to bones, teeth & plant and animal cell membranes

15. Upliftment of the ocean floor
Phosphorus Cycle
Phosphate rocks
Fertilizer
Erosion
Upliftment of the ocean floor
Aquatic plants
Aquatic animals
Ocean Floor

16. Phosphorus Cycle cont’d
2 chief ways humans intervene with the P cycle:
Mining large quantities of phosphate rock to produce commercial inorganic fertilisers and detergents
- Phosphorus is a non-renewable resource and inefficient use may lead to shortage in the future and global food problems. (ScienceDaily, 2010)

17. Phosphorus Cycle cont’d
Adding excess phosphate to aquatic ecosystems in runoff or animal wastes from cropland, sewage discharge & livestock feedlots
- Excess phosphorus leads to growth of algae which blocks waterways. In extreme cases death of the algae results in oxygen deficiency and fish kills.

18. Hydrologic Cycle
describes the movement of H2O between oceans and land masses
collects, purifies and distributes Earth’s fixed supply of water
organisms are made up primarily of H2O

19. The Water Cycle
Source:

20. The Water Cycle
CONDENSATION
AQUIFER

22. Hydrologic Cycle cont’d
2 main ways humans interfere in H2O cycle:
Withdrawing large quantities of fresh water
Clearing vegetation from land for agriculture, mining, roads, construction, etc.