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UAU102F, University of Iceland Fall In Earth science, a biogeochemical cycle is a pathway by which a chemical substance moves through both biotic (biosphere) and abiotic (lithosphere, atmosphere, and hydrosphere) compartments of Earth. Introduction to Environmental Science Throstur Thorsteinsson [email protected] Fig 5.3 Biogeochemcial (element) cycles Carbon (C ) Oxygen (O) Hydrogen (H) Nitrogen (N) Phosphorus (P) Potassium (K) Sulfur (S) Calcium (Ca) Sodium (Na) Magnesium (Mg) Manganese (Mn) Molybdenum (Mo) Cobalt (Co) Zinc (Zn) Aluminum (Al) Copper (Cu) Iron (Fe) others © 2005 John Wiley and Sons Publishers Fig 5.5 Macronutrients Elements required in large amounts by all life Include the “big six” elements that form the fundamental building blocks of life: carbon oxygen hydrogen phosphorus nitrogen sulfur Micronutrients Elements required either in small amounts by all life or moderate amounts by some forms of life and not all by others Limiting factor When chemical elements are not available at the right times, in the right amounts, and in the right concentrations relative to each other © 2005 John Wiley and Sons Publishers Throstur Thorsteinsson ([email protected]) 1 UAU102F, University of Iceland Fall Fig 5.6 The Geologic Cycle: The processes responsible for formation and change of Earth materials Best described as a group of cycles: Tectonic Hydrologic Rock Biochemical © 2005 John Wiley and Sons Publishers Fig 5.7 Tectonic cycle: Involves creation and destruction of the solid outer layer of Earth, the lithosphere Plate tectonics: The slow movement of these large segments of Earth’s outermost rock shell Boundaries between plates are geologically active areas © 2005 John Wiley and Sons Publishers Divergent plate boundary: Occurs at a spreading ocean ridge, where plates are moving away from one another New lithosphere is produced (seafloor spreading) Convergent plate boundary Occurs when plates collide Produces linear coastal mountain ranges or continental mountain ranges Transform fault boundary Occurs where one plate slides past another San Andreas Fault in California Throstur Thorsteinsson ([email protected]) 2 UAU102F, University of Iceland Fall Fig 5.8 The Hydrologic Cycle: The transfer of water from the oceans to the atmosphere to the land and back to the oceans. Includes: Evaporation of water from the oceans Precipitation on land Evaporation from land Runoff from streams, rivers, and sub-surface groundwater © 2005 John Wiley and Sons Publishers Fig 5.9 The rock cycle: Numerous processes that produce rocks and soils Depends on other cycles: tectonic cycle for energy Hydrologic cycle for water Rock is classified as Igneous Sedimentary Metamorphic © 2005 John Wiley and Sons Publishers Carbon (C), the fourth most abundant element in the Universe, after hydrogen (H), helium (He), and oxygen (O), is the building block of life. On Earth, carbon cycles through the land, ocean, atmosphere, and the Earth’s interior in a major biogeochemical cycle Geological scale and the biological/physical scale. Gaseous form CH4, CO2 Atmosphere Solid form CaCO3 Shells Liquid form CO3, HCO3 Ocean Throstur Thorsteinsson ([email protected]) 3 UAU102F, University of Iceland Fall Carbon Emissions from Primary resource for use of fossil fuels increased since 1950 from 1.63 to 7.57 billion tons of carbon CO2 Concentration 399 parts per million (http:// /) Increased 20 percent since 1959 photosynthesis Anthropogenic emissions from: Burning fossil fuels Mining Land conversion Industrial processes Do we have a problem? 2100 Atmospheric concentrations expected to increase drastically 350 ppm considered safe (2 degrees temp increase) See 350.org Throstur Thorsteinsson ([email protected]) Average Global Temperature in 2006 14.6°C, expected to increase from 1.4° – 6°C in 100 years 11 of the 12 years between 1995-2006 were amongst the 12 warmest years on record for global average temperature Glaciers melting, profound impact on ecosystems 4 UAU102F, University of Iceland Photosynthesis: energy (sunlight) + 6CO2 + Energy (sunlight) 6 CO 2 H 2O H2O=> C6C6H12O6 H12O6 6 O2+ 6O2 Fall During winter in the northern hemisphere, photosynthesis ceases when many plants lose their leaves, but respiration continues. At spring, photosynthesis resumes and atmospheric CO2 concentrations are reduced. Respiration: C6H12O6 (organic matter) + C6 H 12O6 6 O2 6O2 => 6CO2 + 6 H2O + energy 6 CO2 6 H 2O Energy Fossil fuels Deforestation Desertification Land-use Throstur Thorsteinsson ([email protected]) 5 UAU102F, University of Iceland Fall The nitrogen cycle: Cycle responsible for moving important nitrogen components through the biosphere and other Earth systems Extremely important because nitrogen is required by all living things; manufacture of protein and DNA Nitrogen fixation: The process of converting inorganic, molecular nitrogen in the atmosphere to ammonia or nitrate, can now be used. Denitrification: The process of releasing fixed nitrogen back to molecular nitrogen that cannot be used Since 1960 Flows of biologically available nitrogen in terrestrial ecosystems doubled Flows of phosphorus tripled > 50% of all the synthetic nitrogen fertilizer ever used has been used since 1985 Human-produced Reactive Nitrogen Humans produce as much biologically available N as all natural pathways and this may grow a further 65% by 2050 Fig 5.19 The phosphorus cycle: Involves the movement of phosphorus throughout the biosphere and lithosphere Important because phosphorus is an essential element for life and often is a limiting nutrient for plant growth. © 2005 John Wiley and Sons Publishers Fig 5.20 © 2005 John Wiley and Sons Publishers Throstur Thorsteinsson ([email protected]) 6