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Biogeo chem
 

Biogeo chem

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  • Phosphorus, one of the "big six" elements required in large quantities by all forms of life, is often a limiting nutrient for plant and algal growth, particularly in areas where nitrogen is not already limiting. For instance, if it is not present in sufficient amounts, plants and algae will not thrive. However, if phosphorus is too abundant, it can cause environmental problems. Lake Sammamish (east of Seattle), for instance, is currently having serious problems with summer algal blooms because of excess inputs of P into the lake. Seattle's Lake Washington experienced similar problems before the current wastewater collection and treatment system was installed in the 1960s and 70s. Unlike carbon and nitrogen, phosphorus does not have a gaseous phase, so transfers are relatively slow. Thus, the phosphorus cycle is significantly different from the carbon and nitrogen cycles. The rate of transfer of phosphorus in Earth’s system is slow compared with that of carbon or nitrogen. Phosphorus exists in the atmosphere only in small particles of dust. In addition, phosphorus tends to form compounds that do not easily dissolve in water. Consequently, phosphorus is not readily weathered chemically. It does occur commonly in an oxidized state as phosphate, which combines with calcium, potassium, magnesium, or iron to form minerals.

Biogeo chem Biogeo chem Presentation Transcript

  • Biogeochemical Cycle Gunjan Mehta VSC, Rajkot
  • Outline Fundamentals of Biogeochemical cycles Definition Types of Biogeochemical cycles Sedimentary cycles Gaseous cycles Hydrological cycle
  • ‘Fundamentals’ of biogeochemical cycles Biogeochemical cycles are cycling of chemical elements or nutrients from the abiotic environment to organism and then back to the abiotic environment. The pathway by which chemical circulate through ecosystem involve both living (biotic) and nonliving (geological) components. Involved organism (bio), environmental geology (geo) & chemical changes (chemical)
  •  They enable a specific chemical element or nutrient to be taken and reused through various forms. They also cause the circulation of these elements in the atmosphere, hydrosphere, litosphere and biosphere
  • Definition BIO: Biology. Life. Living things. These cycles all play a role in the lives of living things. GEO: Earth. Rocks. Land. This refers to the non- living processes at work. CHEMICAL: Molecules. Reactions. Atoms. All cycles include these small pathways. Complete molecules are not always passed from one point to the next.
  • The overall movement of nutrients from the physical environment, through organism, and back to the environment constitutes a biogeochemical cycle.
  • Biogeochemical Cycles Components Divided into 2 components: i. A large reservoir pool of elements – Chemical elements in inorganic forms in the abiotic components of biosphere. - From where the element are absorbed by autotrophic organism and converted into complex organic form - Eg: fossil fuels, minerals, sediments. ii. An exchange/cycling pool – Chemical elements or nutrients in complex organic forms in the biotic components of biosphere. - The element is passed along food chain and ultimately converted back into inorganic form to be released into the environment - Eg: atmosphere, soil, water
  • Definition BIO: Biology. Life. Living things. These cycles all play a role in the lives of living things. GEO: Earth. Rocks. Land. This refers to the non- living processes at work. CHEMICAL: Molecules. Reactions. Atoms. All cycles include these small pathways. Complete molecules are not always passed from one point to the next.
  •  There are two types of biological cycles:-1. Gaseouscycle: element returns to and is withdrawn from the atmosphere as a gas. Eg; Carbon, Nitrogen, Oxygen2. Sedimentary:the element is absorbed from the sediment by plant roots passed to heterotrophs and eventually returned to the soil by decomposers, usually in the same area. Eg. Phosphorus, Sulphur3. Hydrological cycle: Separate cycle
  • The N cycle
  • The N cycle over land
  •  Nitrogen is essential to all living systems: Eighty percent of Earths atmosphere is made up of nitrogen in its gas phase. Atmospheric nitrogen becomes part of living organisms in two ways:1. through bacteria in the soil that form nitrates out of nitrogen in the air.2. through lightning. During electrical storms, large amounts of nitrogen are oxidized and united with water to produce an acid that falls to Earth in rainfall and deposits nitrates in the soil. Plants take up the nitrates and convert them to proteins that travel up the food chain through herbivores and carnivores.
  •  When organisms excrete waste, the nitrogen is released back into the environment. When they die and decompose, the nitrogen is broken down and converted to ammonia. Nitrates may also be converted to gaseous nitrogen through a process called denitrification and returned to the atmosphere, continuing the cycle.
  • Human impacts:1. by artificial nitrogen fertilization (through the Haber Process, using energy from fossil fuels to convert N2 to ammonia gas (NH3) and planting of nitrogen fixing crops (Vitousek et al., 1997).2. transfer of nitrogen trace gases (N2O) to the atmosphere via agricultural fertilization, biomass burning, cattle and feedlots, and other industrial sources (Chapin et al. 2002). N2O in the stratosphere breaks down and acts as a catalyst in the destruction of atmospheric ozone.3. NH3 in the atmosphere has tripled as the result of human activities. It acts as an aerosol, decreasing air quality and clinging on to water droplets (acid rain).
  • 4. Fossil fuel combustion has contributed to a 6 or 7 fold increase in NOx flux to the atmosphere. NO alters atmospheric chemistry, and is a precursor of tropospheric (lower atmosphere) ozone production, which contributes to smog, acid rain, and increases nitrogen inputs to ecosystems (Smil, 2000).5. Ecosystem processes can increase with nitrogen fertilization, but anthropogenic input can also result in nitrogen saturation, which weakens productivity and can kill plants (Vitousek et al., 1997) → algae blooms.6. Decreases in biodiversity both over land and in the ocean can result if higher nitrogen availability increases nitrogen- demanding species (Aerts and Berendse 1988).
  • The Oxygen cycle
  • Plants use the energy of sunlight to convert carbondioxide and water into carbohydrates and oxygen viaphotosynthesis. 6CO2 + 6H2O + energy → C6H12O6 + 6O2Photosynthesizing organisms include the plant life of theland areas as well as the phytoplankton of the oceans.The tiny marine cyanobacteria Prochlorococcus wasdiscovered in 1986 and accounts for more than half ofthe photosynthesis of the open ocean.Animals form the other half of the oxygen cycle breathingin oxygen used to break carbohydrates down into energyin a process called respiration. O2 + carbohydrates → CO2 + H2O + energy
  • CARBON CYCLECarbon moves from the atmosphere toplants .In the atmosphere, carbon is attached to oxygen in a gas calledcarbon dioxide (CO2). Through the process of photosynthesis,carbon dioxide is pulled from the air to produce food made fromcarbon for plant growth.Carbon moves from plants to animals .Through food chains, the carbon that is in plants moves to theanimals that eat them. Animals that eat other animals get thecarbon from their food too.Carbon moves from plants and animals to soils.When plants and animals die, their bodies, wood and leavesdecays bringing the carbon into the ground. Some is buried andwill become fossil fuels in millions and millions of years.
  • Carbon moves from the atmosphere to the oceans.In aquatic ecosystems, CO2 from the air combines with water toproduce bicarbonate ion (HCO3), a source of carbon forphotosynthetic protists. When aquatic organisms respire, the CO2they give off becomes bicarbonate ionCarbon moves from living things to the atmosphere.Each time you exhale, you are releasing carbon dioxide gas (CO2)into the atmosphere. Animals and plants get rid of carbon dioxide gasthrough a process called respiration.Carbon moves from fossil fuels to the atmospherewhen fuels are burned.When humans burn fossil fuels to power factories, power plants,cars and trucks, most of the carbon quickly enters the atmosphereas carbon dioxide gas. Each year, five and a half billion tons of carbonis released by burning fossil fuels. That’s the weight of 100 million adultAfrican elephants! Of the huge amount of carbon that is released fromfuels, 3.3 billion tons enters the atmosphere and most of the restbecomes dissolved in seawater.
  • The carbon fixed into complex organic compounds is returnedto the atmosphere by the counterbalancing release of carbondioxide mainly through:Cell respirationEach time you exhale, you are releasing carbon dioxide gas(CO2) into the atmosphere. Animals and plants need to get ridof carbon dioxide gas through a process called respiration.CombustionWhen humans burn fossil fuels to power factories, powerplants, cars and trucks, most of the carbon quickly enters theatmosphere as carbon dioxide gas.Chemical weatheringChemical weathering of inorganic deposits, such as limestoneand marble from the skeletal remains of shell animals such ascorals and gastropods.
  • Carbon Cycle CO2 - fixation  Photosynthetic autotrophs Aerobic respiration ------> CO2 Fossil fuel burning ------> CO2 Volcanic eruptions ------> CO2 Atmosphere, soils, plant biomass  Largest holding stations for Carbon
  • PHOSPHORUS CYCLE
  • in the ocean
  • and just over land
  •  The phosphorus cycle describes the movement of phosphorus through the lithosphere, hydrosphere, and biosphere. The atmosphere does not play a significant role, because phosphorus and phosphorus-based compounds are usually solids at the typical ranges of temperature and pressure found on Earth. Phosphorus normally occurs in nature as part of a phosphate ion, consisting of a phosphorus atom and some number of oxygen atoms, the most abundant form (called orthophosphate) having four oxygens: PO43-. Most phosphates are found as salts in ocean sediments or in rocks. Over time, geologic processes can bring ocean sediments to land, and weathering will carry terrestrial phosphates back to the ocean.
  •  Plants absorb phosphates from the soil and phosphate enters the food chain. After death, the animal or plant decays, and the phosphates are returned to the soil. Runoff may carry them back to the ocean or they may be reincorporated into rock. The primary biological importance of phosphates is as a component of nucleotides, which serve as energy storage within cells (ATP) or when linked together, form the nucleic acids DNA and RNA. Phosphorus is also found in bones, and in phospholipids (found in all biological membranes). Phosphates move quickly through plants and animals; however, the processes that move them through the soil or ocean are very slow, making the phosphorus cycle overall one of the slowest biogeochemical cycles.
  • Human influence: Artificial fertilizers and other wastes not absorbed by plants mostly enter the groundwater and collect in streams, lakes and ponds. The extra phosphates are a major contributor to the process called eutrophication, which causes excessive growth of water plants and algae populations and subsequent depletion of dissolved oxygen potentially suffocating fish and other aquatic fauna.
  • The carbon cycle
  • Sulphur cycle
  • Introduction Flow of a chemical through certain subdivisions  Atmosphere  Lithosphere  Hydrosphere  Biosphere Usually of Elements (Institute)
  • Introduction Sulfur- S, it is an element  Naturallyfound in earth  At room temp., it is a solid  Present in proteins, amino acids, vitamins, and enzymes, necessary for plants and animals  Often reacts with hydrogen creating hydrogen (“Sulfur”) sulfide  Can dissolve in water  With metals in water, forms metal sulfides;sulfates in air
  • Sulfur Cycle (“Part IV”)
  • Sulfur Cycle In ground: most found in rocks, or salt in earth, or as sediment at bottom of ocean  Found as S, H2S, SO4-2, (NH4)2SO4  Enter ground: Plants absorb, or left by acid deposition (fog or precipitation)  As SO4-2, (NH4)2SO4, and then turn H2S by bacteria, decay, (“Oxygen”) use and plant  Stored: Ground, rock, ocean, somewhat in air
  • Sulfur Cycle Sulfur is transferred into biosphere then back into ground, or from ground to atmosphere  Microorganisms turn it into H2S (gas)  Oxidized in atmosphere to SO2, and then to H2SO4 (an acid) with water contact  Mined ores released to atmosphere in factories as H2S and SO2  Volcanoes and hot springs
  • Sulfur Cycle Deposited next in water  Through precipitation, dry deposition, leaching  Rainfall= deposited 73E12 grams sulfur in 1960  SO4-2 leaches from soil into ocean as sediment  H2SO4 falls into ocean  Dimethyl Sulfide, carbonyl sulfide (biogenic gases), released by plankton returns back into atmosphere (turns into SO2)  Either re-evaporated, left as sediment for long time, or deposited on land  High amount of sulfur is deposited on land by sea  When back on land, cycle repeats
  • Driving Force Driven by:  constant addition of sulfur to environment by earths interior (geosphere)  Human disturbance, addition of sulfur to atmosphere, (also dug up from environment)  Natural processes (incl. Biological, hydrological, due to sun’s energy) (“A Black Smoker”)  Plant uptake, microbes (Desulfovibrio sp. or Desulfotomaculum sp.)
  • Percentages of Sulfur Common in ground as FeS2 Reservoirs Oceanic Rocks Sediment Freshwater Ice Atmosphere Sea (“Sulfur Cycle”)
  • Percentages of Sulfur Most sulfur in particulate form  Therefore it is a sedimentary cycle  Very short residence time in atmosphere (1-2 days)  Even in atmosphere, found as aerosols (<1 micrometer), not gas usually  In atmosphere, way less than 1%  Its around .000314 percent  90-95% SO2 from power plants and factories
  • Human Effect (“Arial”) When mine ores, sulfur/sulfides released into soil (“Sulfur Mining”) Combustion of fossil fuels  Release of SO2, causes acid rain, increases amount already present  28% of sulfur in rivers from pollution, mining, erosion, etc.  Help move cycle but also upset balance- too much S means acid rain  Hydrodesulphurization (refine hydrocarbons)- surplus of S in Alberta Canada
  • Phosphorus CycleNo gaseous phaseSlow rate of transferReleased by erosion of exposed rockAbsorbed by plants, algae, and somebacteriaExported from terrestrial ecosystems byrunoff to oceansMay be returned through seabird guano