Lecture 03 - 26 Jan.doc

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Environmental Science
Environmental Science 1021F/G
Christie Stewart

ES1021G Lecture 3 – January 26, 2012 Part 1: Flows & Cycles of Nutrients What are nutrients? Nutrients are any chemicals that are required for the proper functioning of organisms Autotrophs use inorganic nutrients in their nutrition Animals require organic nutrition – the biomass of other organisms Examples of inorganic nutrients: Gaseous carbon dioxide (CO ) 2 - + Ionic nitrate (NO 3 an-3ammonium (NH ) 4 Ionic phosphate (PO ) 4 Ionic sulphate (SO )4& gaseous sulphur dioxide (SO ) 2 Ionic calcium (Ca ), magnesium (Mg ), potassium (K ) + Nutrient flows and cycles Four most important nutrient, carbon, nitrogen, phosphorus, sulpher Nutrient cycling refers to the transfers (fluxes of H2O in atmosphere from gaseous to liquid water and vice versa), transformations (water to gas and back) , and recycling (nothing goes to waste, everything goes back through the cycle) of nutrients A nutrient budget is a quantitative estimate of the quantities present in compartments and the fluxes (rates of movement) between them (we burn rocks/coal and it becomes gas in the atmosphere). The budget is how much is in each stage at a given time, or how much we have to work with. Most nutrient systems are open, there are inputs and outputs (do not memorize, just shows compartments, fluxes, and transformations of nutrient cycles.) The Page 1 of 13 ES1021G Lecture 3 – January 26, 2012 Soil Ecosystem (EXAM) Soil is an ecosystem comprised of inorganic material (rock bits from weathering), organic matter (decaying biomass), and a great diversity of organisms(worms, bacteria, fungi, etc) (as much going on below the soil as on the surface, it is where most nutrient cycling occurs on terrestrial habitats) It is derived from original parent materials, which over time are modified by climatic factors (especially percolating water) and organisms Mature soils (have been developing for thousands of years) develop distinctive (unique to where they have formed) that are dependent on local climatic conditions and the kind of ecological community in which they have developed Ex. Red Soils- rich in iron Peat Soils-dead animals and peat biomass Black Soils- dark, high in nutrients, farming soil Loam- ideal mixture of sand, silt and clay Soil type is important for crops that can grow and defines how we can use our natural resources, and the ecosystem and viability of natural resources can be in that biosphere Factors that determine soil types Chernozem – a soil that develops in natural grasslands (good fro crops) Podzol – develops in coniferous boreal forest (not god fro crops, unless it’s a Christmas tree farm) Brown forest soil – develops in temperate hardwood forest Gleysol – develops in cool temperate habitats that are periodically waterlogged (very little sand) Solonetz – develops in desert communities Page 2 of 13 ES1021G Lecture 3 – January 26, 2012 Organic – develops in fens and bogs (most of soil is not from rock, but dead and decaying plants) [Combine last three soil type to make ideal loam] Soil Horizons Soil horizons are distinctive layers that vary in their physical and chemical properties: O horizon - Litter layer – organic matter identifiable as plant litter Duff layer – litter fragments still visible Humus layer – well-humified organic matter (humus is the acid formed when plants break down, brown colour) A horizon – a zone of eluvation (out-leaching) of organics, Fe, Al, Ca, Mg (all components becoming elements, not recognizable anymore, a lot of root penetration as well) B horizon – a zone of eluviation (deposition) of materials leached from the A horizon (minerals being deposited from above) C – parent materials (bigger constituent of parent materials, mixture of lysopheric material from below and organic material from above) R – the regolith, or underlying rock Plants  O horizon  A horizon  B horizon  C horizon  R horizon (parent rock) Nutrient cycles Carbon Cycle: (first and most important) Carbon is the most abundant building block of life, accounting for about ½ of dry biomass Page 3 of 13 ES1021G Lecture 3 – January 26, 2012 The largest store of C is in carbonate rocks, such as limestone (CaCO )3and dolomite (Ca,MgCO ) looks almost identical to limestone 3 The most abundant atmospheric form is CO (~382 ppm in 2009) Photosynthetic autotrophs fix CO i2to simple sugars, which is used to drive the metabolic production of all biochemicals Organic-carbon is eventually returned to the atmosphere via decomposition, mostly as CO , an2 some CH (when you day all of the carbon in you will decompose and return to the soil 4 or become carbon dioxide or methane) [KNOW, RECOGNIZE AND LABEL FOR EXAM] Geological compartment contains fossil fuels- where most carbon is kept When we combust fossil fuels we want to break the C-C bonds in order to get energy, leaving the rest of the carbon to be released into the atmosphere (772 billion tonnes in the atmosphere) How to get carbon out of the atmosphere - uptake by plants (from atmosphere to terrestrial organic atmosphere aka biological uptake) - By uptake by oceans (oceans have a certain amount of dissolved carbon dioxide) sediment in oceans has 10^17 tonnes of carbon as carbon in plants and animals that die, decay in the sediment layer of the oceans, which then gets transferred (in millions of years) to the geological compartment of earth Nitrogen Cycle: [not on exam] Nitrogen is rather abundant in organic matter, accounting for 1-2% of biomass Its largest store is in the atmosphere, of which 78% is nitrogen gas (N2) Nitrogen is an insignificant constituent of rocks and minerals, but it is present in all organic Page 4 of 13 ES1021G Lecture 3 – January 26, 2012 matter Nitrogen fixation by microorganisms converts N to 2mmonia (NH ), a n3trient for autotrophs During decomposition, ammonification converts organic-N to ammonium (NH ) 4 Nitrification converts ammonium to nitrate (NO ) 3- Tends to be in living environments or atmosphere - Can be fixed by lightning Different elements are more important in some cycles then others, know nutrients major compartments for EXAM Page 5 of 13 ES1021G Lecture 3 – January 26, 2012 Phosphorus Cycle: Phosphorus is somewhat abundant in organic matter, accounting for ~0.2% of biomass (still considered significant, even though percentage small) Its largest store is rocks and minerals, but it is rarely abundant The key nutrient is phosphate (PO ) 4hosphate leads to eutrophication in lake ecosystems, which often limits primary productivity, especially in freshwater It is metabolically necessary for plants, so providing phosphates to areas where it is low, leads to explosions of life A wide variety of microbes convert organic-P to phosphate during decomposition (when phosphate is added, decomposition in increased and oxygen is deprived leading to death of fish) Sulphur Cycle: Sulphur is somewhat abundant in biomass Its largest stores are in rocks and sulphide minerals In the atmosphere it occurs as sulphur dioxide (SO ) 2nd hydrogen sulphide (H S), 2nd as -2 particulates containing sulphate (SO )4 The key nutrient for plants is sulphate, but they also absorb SO f2om the atmosphere so plants regularly take up sulphur Chemoautotrophic bacteria can oxidize various forms of sulphide into sulphate, gaining energy and creating acidity Nutrients- Summary - Nutrients are chemicals essential for the metabolism of organisms and ecosystems - Insufficiency or excess of nutrients can limit or harm ecosystems (eutrophication) - Nutrients cycle between inorganic and organic forms and between ecosystem compartments - Soil is an important ecosystem compartment for the major nutrient cycles Part 2: Evolution Page 6 of 13 ES1021G Lecture 3 – January 26, 2012 Origins of life on Earth Pre-biotic conditions are not well known, but the atmosphere is thought to have been a chemically ‘reducing’ environment dominated by: hydrogen sulphide (H S)2(used by early forms for building biomass instead of oxygen) methane (CH ) 4 ammonia (NH ) 3 carbon dioxide (CO ) 2forests are the lungs of the earth) Traces of simple organic compounds, such as amino acids, were also present, having been spontaneously created, perhaps during lightning events Lots of water The genesis of life occurred ~3.5 billion years ago, enormously increasing the amounts of biochemicals and other organic matter in the environment (more complex amino acids and biochemical forming) When photosynthetic organisms evolved, ~2.5 billion years ago, they released oxygen (O ) as a2 waste, so the atmosphere became an ‘oxidizing’ environment dominated by: nitrogen (N ) 2 oxygen (O )2 the O 2llowed ozone (O ) 3 to form, providing a shield against deadly solar ultraviolet radiation Evolution Evolution is a science- based theory – it relies on objective interpretation of observations of the natural world and other kinds of research According to this theory: There was a natural genesis, ~4.5 B years ago, under conditions suitable for the origin of the first life forms
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