18169970
Description
Flashcards by Kelly Chamberlain, updated more than 1 year ago
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Created by Kelly Chamberlain
over 5 years ago
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| Question | Answer |
| Steps in photosynthesis cycle (3) | 1. CO2 from atmosphere + soil water forms sugar 2. Animals eat plants and use carbon to build tissues 3. Animals return CO2 to environment by breathing and death |
| Reservoirs of Carbon (2) | CO2 in atmosphere and carbon in earth crust |
| Significance of Carbon cycle globally (3) | Driving force for other element cycles Photosynthesis/respiration Greenhouse effect and warming |
| Long term carbon cycles (2) | Silication Coalification |
| Silicate cycle (4) | Transformation of silicate rocks to carbonate rocks 1.Atmospheric CO2 dissolves in rain, forming carbonic acid 2. Carbonic acid dissolves silicate rocks and releases cations 3. Products travel to oceans 4. CO2 expelled to atmosphere via volcanic sea vents |
| How do plants accelerate mineral weathering? | Secrete organic acids |
| Effect of warm temperatures on plants? | Promotes weathering, soil formation, plant growth and root activity |
| Coalification cycle | Burial of organic matter Warm temps: Water accumulates forming hydromorphic soil and increased aquatic vegetation and detritus Cold periods: Vegetation and detritus becomes buried under mineral sediments |
| Role of microbes in carbon cycle | Major decomposers that break down organic matter returning CO2 to atmosphere and C to soil |
| What does decomposed organic matter by microbes become | Matter becomes microbial biomas and CO2 A fraction of carbon in matter becomes protected in soil |
| Major components of plant residues (5) | Carbohydrates: Starch, cellulose and hemicellulose Lignin Proteins Lipids |
| Starch digestion | Via Amylase Polymer of glucose units, high energy Accessible to most microbes |
| Cellulose & Hemicellulose structure and digestion | Cellulose - Linear polymer of glucose Hemicellulose - Surrounds cellulose Enzyme - Cellulase Microbes break down cellulose and hemicellulose via cellulase, high energy. Easy to digest |
| Lignin structure and digestion | Complex structure that is hard to decompose, surrounds cellulose. Microbes only break down lignin to reach cellulose. Digested via oxidation - free radicles released to break down lignin, CO2 released |
| Brown Rot and soft rot | Fungi which decompose polysaccharides associated with lignin |
| White rot | Fungi which truly decomposes lignin and the sugars associated with lignin |
| Protein digestion | Protein bonds hydrolysed by protease enzymes to release amino acids |
| Lipid digestion | Plants store lipids as fats and lipids make up waxes. Lipids digested Via lipases Dcomposition is slow as lipids are hydrophobic |
| Physical Protection of Organic matter in soil | Protection occurs in micropores where microbes cant access them, or in pores where the water current is discontinuous so microbes don't have access |
| Chemical protection of organic matter - Surface area | In clay soil, Iron ppts on clay particles and organic matter attaches to iron. Ppts increase surface area and increase amount of organic matter Energy required to remove matter from ppts |
| Chemical protection of organic matter - Chemical bonding | Organic matter is amphiphilic. Polar region faces minerals in soil and attracts cations |
| Physical role of organic matter | Binds particles to forms aggregates reduces erosion increases water capacity Increases tilth |
| Chemical role of Organic matter | Nutrient cycling Retains cations Buffers pH Filters contaminants |
| Biological role of organic matter | Source of C and energy to microbes Inactivate some pesticides Enhance degradation of pesticide residues |
| Major reservoirs of Nitrogen (3) | Atmosphere - most unreactive Igneous rocks Sedimentary rocks |
| Inorganic vs organic nitrogen | Inorganic in Atmosphere, organic in Soil, oceans and animals Organic N less reactive than inorganic N N is not reactive until fixed |
| Nitrogen transformations in soil (8) | Fixation Immobilisation/Mineralisation NH4+ Nitrification Denitrification NH3 volatilisation Leaching |
| Fixation | In Prokaryotes Conversion of atmospheric N2 to NH3 |
| Haber Bosch synthesis | Converts unreactive N2 to reactive NH3, used for fertilisers Requires lots of energy for transformation |
| Biological fixation of Nitrogen | Rhizobium bacteria in nodules, require nitrogenase enzyme. Plants supply energy to rhizobium which fixes N for plant N2 reduced to NH3, requires anoxic environment |
| Immobilisation of N | Microbial conversion of NH4+ and NO3- (mineral nitrogen) into organic N, requires carbon |
| Mineralisation | Unreactive organic N converted to reactive inorganic N Organic N in proteins degraded by enzymes forming amino acids and amines which are converted to Ammonium |
| Function of urea in soils | Added via fertiliser or animal waste Hydrolysed to NH4+, increasing soil pH, NH3 released to atmosphere |
| Activity of NH4+ in soil (5) | Uptake by plants Immobilisation by microbes Retention in soil particles Loss through ammonia - NH3 volatilisation Conversion to nitrite and nitrate (nitrification) |
| Nitrification | Oxidation of NH4+ to NO3- Microbes release energy during process require oxygen Microbes are acid sensitive, produce acids to control their chemical environment |
| Ammonia volitilisation | NH4+ converted to NH3 in soil and NH3 is lost to atmosphere |
| Nitrate Leaching | Inorganic nitrogen in soil: NH4+ and NO3- Significant environmental pollutants Causes eutrophication and forms N2O greenhouse gas |
| Denitrification | Anaerobic bacteria use nitrate as oxidant for respiration when O2 levels are low, high moisture, presence of C substrate Forms N2O |
| Nitrification Inhibitors | Restrict NH4+ conversion to NO3- so reduce NO3- conversion to N2 and N2O Did use DCD but now banned |
| Differences between Phosphorous and other cycles | Does not come from atmosphere No redox reactions involved Finite source and mined from reservoirs, mostly in liquid and solid phases |
| Phosphorous cycle | Pool: Sediment Weathers from rocks and released to ecosystem via soil Fungi and microbes accelerate release by releasing organic acids P from soil taken up by plants and plants eaten by animals, returned to soil via waste and mineralised |
| Contamination sources in phosphorous cycle | Sulfur oxidised to SO4 2- H2SO4 reacts with mined phosphate rock forming gypsum gypsum waste contains uranium and cadmium |
| Transformations of P | Organic and inorganic forms in soil, no redox required Organic is non reactive and needs to be mineralised |
| Adsorption | Rock weathering forms a precipitate on top of phosphorous deposit so only small amount available, added Phosphorous becomes locked in soil |
| Mobility of P in soil | Only slightly soluble so immobile in soil. Plants form root hairs to reach sources of phosphorous |
| Mycorrhizae and P uptake | Mycelium network of mycorrhizae extends through soil to reach phosphorous soils Plant provides fungi sugars and fungi provides water and nutrients to plant |
| Plant mycorrhizal relationship in good N and P concentrations | Inhibit mycorrhizal infection at adequate nutrient concentrations, very large energy expenditure to continue infection |
| Benefits of mycorrhizal infection | Changes chemical environment increasing the amount of inorganic P roots can uptake, Increases root surface area, increases root distance, decreases diffusion distance |
| How do mycorrhizal fungi modify root environment? | Direct: Produce phosphatases and organic acids Indirectly: Increases uptake of calcium which releases phosphorous Increased efficiency of NH3 use, reduces pH and increases P solubility |
| Ectomycorrhiza | External mycelial sheath around roots, hartig net - nutrient exchange |
| Endomycorrhiza | Arbuscular, most common association and effective at low phosphorous concentrations |
| Difference between Sulfur and Nitrogen | Sulfur does not need to be fixed, mostly available of sulphate |
| Hierarchy of energy in sulfur compounds | H2S S SO2 SO3 2- SO4 2- |
| Organic sulfur | Highly reduced forms are organic and in organic matter, essential for forming amino acids and proteins |
| Primary source of sulfur to atmosphere | DMS roduced by phytoplankton Has cooling effect, DMS scatters light. Increasing Phytoplankton to increase DMS and decrease temp investigated, but implications of increased phytoplankton unknown |
| Elemental sulfur | Frequently mined and found near hot springs Oxidised to SO42-, releases heat H2SO4 used to treat phosphate rock |
| Phases of sulfur cycle | Sedimentary: Sulfur locked in organic and sedimentary deposits released through weathering and decomposition Gaseous: sulfur circulates globally |
| Processes of sulfur cycle (4) | Assimilatory reduction (Immobilisation) Dissimilatory reduction Oxidation Desulphurylation (Mineralisation) |
| Assimilatory reduction | SO42- incorporated into cells Sulfate reduced to sulphides (S2-) and incorporated into amino acids |
| Dissimilatory reduction | So4 2- used as oxidant of sugars by anaerobic heterotrophs |
| Oxidation | Organisms oxidise reduced forms of sulfur to release energy H2S oxidised to S S oxidised to Sulfate |
| Pyrite | Iron and sulfure reduction forms Pyrite -Reduced S accumulates as pyrite |
| Restoration of sulfur contaminated sites | When exposed to oxygen, sulfur is reduced to SO4 2- decreasing pH and inhibiting growth Want to keep pyrite salt in reduced form, add water to reduce oxygen contact keeping sulfur reduced. Adding CaCO3 buffers pH |
| Mineralisation of S | Organic S broken down to H2S and other organic S gases |
| Acid rain formation | Fossil fuel burned releasing SO2 into atmosphere SO2 forms H2SO4 H2SO4 dissolved in and released in rain |
| What is Bioremediation | Cleaning up contaminants using microbes and plants by breaking down toxins into less harmful substances |
| Types of enzymes involved in bioremediation | Intra, ecto and extracellular enzymes |
| Classes of enzymes involved in | Hydrolases, dehalogenases and oxidoreductases |
| Xenobiotics | Pollutants, have resistance to attenuation due to chemical bonds, have not been around long enough for microbes to develop pathway to remove them |
| Key features of bio-remediating microbes | Grows quickly in niche environment Modifies or consumes pollutant quickly Does not produce harmful byproducts Non pathogenic Aerobic preferentially due to fast metabolism |
| Microbes in the Bioremediation of organic pollutants | Microbes that degrade pesticides and hydrocarbons as their sole source of carbon and energy |
| Common pollution events | spillages or leakages of crude oil |
| Optimal conditions for organic pollution degradation | Favourable temperature, good nutrient supply (C:N 30:1), sufficient nutrient supply |
| Anaerobic degradation of PAHs and Halogenated compounds | Dechlorinate PCBs and remove halogens from aliphatic and aromatic halogen-hydrocarbons. This reaction reduces or eliminates toxicity |
| Fungi and bioremediation of hydrocarbons | Ligninolytic fungi can digest lignin and degrade organic pollutants |
| Methanotrophs and bioremediation | Methanotrophs - Aerobic bacteria use methane as carbon source and energy Can degrade halogenated hydrocarbons and aromatic hydrocarbons Use methane monooxydase |
| Processes that microbes use to degrade pollutants (4) | Mineralisation Co-metabolism Polymerisation Bioaccumulation |
| Mineralisation | Pollutant used as growth: source of energy and carbon, releases CO2 |
| Co-metabolism | Energy source added to transform the pollutant |
| Polymerisation | Uses pollutant to form large polymer, less toxic and easier to degrade |
| Accumulation | Pollutant accumulates in microbe, effective in aquatic environments |
| Mechanisms of In Site remediation (4) | Biostimulation Bioaugmentation Bioventing Biosparging |
| Biostimulation | Stimulation of microbial activity |
| Bioaugmentation | Inoculating soil with microbes |
| Bioventing | Injecting air into unsaturated zones - provides oxygen to existing microbes |
| Biosparging | Using existing microbes to degrade pollutants in saturated zones. Injecting air and nutrients into saturated and unsaturated zones |
| Ex situ bioremediation pathways (3) | Land farming Turned Windrows Forced vented piles |
| Land farming | Contaminated soil excavated and spread out in thin layer over lined surface. Remediation enhanced by regular turning and addition of nutrients. Requires large area, but simple and cheap |
| Turned Windrows | Contaminated soil excavated and shaped into piles on a lined surface Pile periodically aerated Cheap and effective |
| Forced vented piles | Shaped into piles 3m high -6m wide Air injected or vacuum Vapours collected and treated by activated carbon to reduce emissions |
| Selenium decontamination | Adding contaminated soil to bioreactor, producing selenium metalloids, and other useful byproducts |
| Phytoremediation | Using plants Roots can absorb pollutants and heavy metals and break them down and prevent harmful substances from reaching waterways |
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