Presentation on theme: "AP Environmental Science Biogeochemical Cycles"— Presentation transcript:
1 AP Environmental Science Biogeochemical Cycles Mr. GrantLesson 35Biogeochemical Cycles
2 Objectives: Define the term biogeochemical cycles. Compare and contrast how carbon, phosphorus, nitrogen, and water cycle through the environment.Explain how human impact is affecting biogeochemical cycles
3 Define the term biogeochemical cycles. Biogeochemical Cycle: The comprehensive set of cyclical pathways by which a given nutrient moves through the environment.
4 Compare and contrast how carbon, phosphorus, nitrogen, and water cycle through the environment. A source is a reservoir that contributes more of a material than it receives, and a sink is one that receives more than it provides.Water moves widely through the environment in the water (hydrological) cycle.Most carbon is contained in sedimentary rock. Substantial amounts also occur in the oceans and in soil. Carbon flux between organisms and the atmosphere occurs via photosynthesis and respiration.Nitrogen in a vital nutrient for plant growth. Most nitrogen is in the atmosphere, so it must be “fixed” by specialized bacteria or lightning before plants can use it.Phosphorus is most abundant in sedimentary rock, with substantial amounts in soil and the oceans. Phosphorus has no appreciable atmospheric pool. It is a key nutrient for plant growth.
5 Nutrients circulate through ecosystems Matter is continually circulated in ecosystemsNutrient (biogeochemical) cycles = the movement of nutrients through ecosystemsAtmosphere, hydrosphere, lithosphere, and biospherePools (reservoirs) = where nutrients reside for varying amounts of time (the residence time)Flux = the rate at which materials move between poolsCan change over timeIs influenced by human activities55
6 Main components of a biogeochemical cycle Source = a pool that releases more nutrients than it acceptsSinks = a pool that accepts more nutrients than it releases
7 The hydrologic cycle Water is essential for biochemical reactions It is involved in nearly every environmental systemHydrologic cycle = summarizes how liquid, gaseous and solid water flows through the environmentOceans are the main reservoirEvaporation = water moves from aquatic and land systems into the atmosphereTranspiration = release of water vapor by plantsPrecipitation, runoff, and surface water = water returns to Earth as rain or snow and flows into streams, oceans, etc.
9 GroundwaterAquifers = underground reservoirs of sponge-like regions of rock and soil that hold…Groundwater = water found underground beneath layers of soilWater table = the upper limit of groundwater in an aquiferWater may be ancient (thousands of years old)Groundwater becomes exposed to the air where the water table reaches the surfaceExposed water runs off to the ocean or evaporates
11 The carbon cycleCarbon is found in carbohydrates, fats, proteins, bones, cartilage and shellsCarbon cycle = describes the route of carbon atoms through the environmentPhotosynthesis by plants, algae and cyanobacteriaRemoves carbon dioxide from air and waterProduces oxygen and carbohydratesPlants are a major reservoir of carbonRespiration returns carbon to the air and oceansPlants, consumers and decomposers1111
12 Sediment storage of carbon Decomposition returns carbon to the sedimentThe largest reservoir of carbonMay be trapped for hundreds of millions of yearsAquatic organisms die and settle in the sedimentOlder layers are buried deeply and undergo high pressureUltimately, it may be converted into fossil fuelsOceans are the second largest reservoir of carbon
14 The nitrogen cycle Nitrogen comprises 78% of our atmosphere It is contained in proteins, DNA and RNANitrogen cycle = describes the routes that nitrogen atoms take through the environmentNitrogen gas cannot be used by organismsNitrogen fixation = lightning or nitrogen-fixing bacteria combine (fix) nitrogen with hydrogenTo form ammoniumWhich can be used by plants
15 Nitrification and denitrification Nitrification = bacteria convert ammonium ions first into nitrite ions then into nitrate ionsPlants can take up these ionsAnimals obtain nitrogen by eating plants or other animalsDecomposers get it from dead and decaying plants or other animalsReleasing ammonium ions to nitrifying bacteriaDenitrifying bacteria = convert nitrates in soil or water to gaseous nitrogenReleasing it back into the atmosphere
17 Humans put nitrogen into the environment Fully half of nitrogen entering the environment is of human origin
18 The phosphorus cyclePhosphorus (P) is a key component of cell membranes, DNA, RNA, ATP and ADPPhosphorus cycle = describes the routes that phosphorus atoms take through the environmentMost phosphorus is within rocksIt is released by weatheringThere is no significant atmospheric componentWith naturally low environmental concentrationsPhosphorus is a limiting factor for plant growth
20 Explain how human impact is affecting biogeochemical cycles. People are affecting Earth’s biogeochemical cycles by shifting carbon from fossil fuel reservoirs into the atmosphere, shifting nitrogen from the atmosphere to the planet’s surface, and depleting groundwater supplies, among other impactsPolicy can help us address problems with nutrient pollution.
21 Human impacts on the hydrologic cycle Removing forests and vegetation increases runoff and erosion, reduces transpiration and lowers water tablesIrrigating agricultural fields depletes rivers, lakes and streams and increases evaporationDamming rivers increases evaporation and infiltrationEmitting pollutants changes the nature of precipitationThe most threatening impact: overdrawing groundwater for drinking, irrigation, and industrial useWater shortages create worldwide conflicts2121
22 Humans affect the carbon cycle Burning fossil fuels moves carbon from the ground to the airCutting forests and burning fields moves carbon from vegetation to the airToday’s atmospheric carbon dioxide reservoir is the largest in the past 800,000 yearsIt is the driving force behind climate changeThe missing carbon sink: 1-2 billion metric tons of carbon are unaccounted forIt may be taken up by plants or soils of northern temperate and boreal forests
23 Humans affect the nitrogen cycle Haber-Bosch process = production of fertilizers by combining nitrogen and hydrogen to synthesize ammoniaHumans overcame the limits on crop productivityFixing atmospheric nitrogen with fertilizersIncreases emissions of greenhouse gases and smogWashes calcium and potassium out of soilAcidifies water and soilsMoves nitrogen into terrestrial systems and oceansReduces diversity of plants adapted to low-nitrogen soilsChanged estuaries and coastal ecosystems and fisheries
24 Humans affect the phosphorus cycle Mining rocks for fertilizer moves phosphorus from the soil to water systemsWastewater discharge also releases phosphorusRunoff containing phosphorus causes eutrophication of aquatic systemsProduces murkier watersAlters the structure and function of aquatic systemsDo not buy detergents that contain phosphate
25 Solutions to the dead zone The Harmful Algal Bloom and Hypoxia Research and Control Act (1998)Called for an assessment of hypoxia in the dead zoneSolutions outlined included:Reduce nitrogen fertilizer use in Midwestern farmsApply fertilizer at times which minimize runoffUse alternative crops and manage manure betterRestore wetlands and create artificial onesImprove sewage treatment technologiesEvaluate these approaches
26 Decreasing pollutionScientists, farmers and policymakers are encouraged toDecrease fertilizer useWhile safeguarding agricultureOffering insurance and incentivesUsing new farming methodsPlanting cover cropsMaintaining wetlandsThere have been some successesDespite a lack of funding
27 Johan Rockstrom: Let the environment guide our development (18:11) TED VideoHuman growth has strained the Earth's resources, but as Johan Rockstrom reminds us, our advances also give us the science to recognize this and change behavior. His research has found nine "planetary boundaries" that can guide us in protecting our planet's many overlapping ecosystems."Rockstrom has managed in an easy, yet always scientifically based way, to convey our dependence of the planet's resources, the risk of transgressing planetary boundaries and what changes are needed in order to allow humanity to continue to develop.“Anna Ritter, Fokus magazineJohan Rockstrom: Let the environment guide our development (18:11)