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HMET.pptx

  1. 1. College of Horticulture and Research Station, Jagdalpur course- HMET 5311 Submitted to: Submitted by: Dr Aashish Anant Group 06
  2. 2. “ Source and sink for greenhouse gases, Atmospheric chemistry and Plant senses and responses to increasing CO2 concentration
  3. 3. Green house gases • A greenhouse gas (GHG or GhG) is a gas that absorbs and emits radiant energy within the thermal infrared range, causing the greenhouse effect. • Carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), Ozone (O3), and chlorofluorocarbons (CFCs), along with water vapour are major greenhouse gases in atmosphere. • Without greenhouse gases, the average temperature of Earth’s surface would be about −18 °C (0 °F),rather than the present average of 15 °C (59 °F).
  4. 4. Green house effect • Greenhouse effect is the process by which radiations from the sun are absorbed by the greenhouse gases and not reflected back into space. • This insulates the surface of the earth and prevents it from freezing and maintains an optimium temperature which supports life on earth.
  5. 5. Sources of greenhouse gases • There are mainly two important sources of greenhouse gases that is: 1)Natural sources 2) Artificial or Anthropogenic sources • Natural sources of GHGs are volcanos, respiration by living organisms, decay and combustion of organic matter,wetlands for CH4 etc. • The amounts of GHGs are balanced in the atmosphere naturally by many physical, chemical or biochemical processes such as natural sinks that take-up CO2, e.g. terrestrial vegetation.
  6. 6. •Due to the industrial revolution and human intervention, the amount of greenhouse gases present in the atmosphere has drastically increased •The main source of increased carbon dioxide in the atmosphere is the burning of fossil fuels, coal, petroleum and natural gas •Urbanisation, deforestation and soil erosion has also contributed to the increased amount of carbon dioxide •Various industries, solid and wastewater management are a source of increased methane. •Rice cultivation has contributed considerably to increased greenhouse gases.
  7. 7. • Carbon dioxide (CO2): Fossil fuel use is the primary source of CO2. • CO2 can also be emitted from direct human-induced impacts on forestry and other land use, such as through deforestation, land clearing for agriculture, and degradation of soils. • Nitrous oxide (N2O): Agricultural activities, such as fertilizer use, are the primary source of N2O emissions. • Fossil fuel combustion also generates N2O. • Fluorinated gases (F-gases): Industrial processes, refrigeration, and the use of a variety of consumer products contribute to emissions of F-gases, which include hydrofluorocarbons (HFCs), perfluorocarbons (PFCs), and sulfur hexafluoride (SF6). • Water vapour:Increased evaporation from land areas and water sources.
  8. 8. Sinks for green house gases • A sink is a reduction in atmospheric GHGs by storing (sequestering) carbon or any other gas in another form. • A traditional carbon sink is underground coal and oil deposits where millions of year ago living plants (and other organisms) used atmospheric carbon to build the plant. • Growing trees sequester large amounts of carbon dioxide from the atmosphere through photosynthesis. • An increase in biomass from the growth of forests (both above ground and below ground) provides a carbon sink. • The soil is a great storehouse (sink) of carbon in the form of organic matter.
  9. 9. • The atmosphere, and more precisely the troposphere, is the largest sink for methane. • Methane in the troposphere reacts with hydroxyl (OH) radicals, forming mainly water and carbon dioxide • The major sink for atmospheric N2O is destruction in the stratosphere where the majority undergoes photolysis to N2 + O • .Greenhouse gas sinks reduce annual greenhouse gas emissions by 11.4%. Ten percent of these offsets are due to forests and soils.
  10. 10. Atmospheric chemistry • Atmospheric chemistry is the branch of atmospheric science focused on chemical processes within Earth’s atmosphere. • It is mainly determined and influenced by interaction between living organisms and atmosphere. • The composition of earth‘s atmosphere changes due to natural processes such as volcano emission, lighting and bombardment by solar particles from corona. • The problems addressed by atmospheric chemistry include acid rain, ozone depletion, photochemical smog, greenhouse gases and global warming
  11. 11. Global warming Global warming is a gradual increase in the earth’s temperature generally due to the greenhouse effect caused by increased levels of carbon dioxide, CFCs, and other pollutants. “
  12. 12. Ozone depletion How ozone is formed?
  13. 13. • The main cause for depletion of ozone is detrimental as excessive release of Cl and Br from man made compounds such as CFCs, Halogen, CCl4, Methyl chloroform etc. • These substances are generally categorized as Ozone depleting substance. • CFCs are released into atmosphere due to cleaning agents, coolants in refregirator, packing material, air conditioning etc. • Cl and Br generally alter the ozone forming reaction leading to ozone depletion.
  14. 14. Plant senses and responses to changes in CO2 concentration • Carbon dioxide is an essential component for plant growth and development. • Rising CO2 concentration can have both positive and negative effect on plants. • Currently the amount of CO2 in atmosphere is approximately 380ppm. • Plant physiological and biochemical responses to elevated C02 known as CO2 fertilization effect (Dhakhwa et al, 1997), have been studied in plants with different photosynthetic pathway namely C3 and C4.
  15. 15. A)Effect on photosynthesis • On the basis of photosynthetic activity, the plants are classified into C3 and C4. • They both respond differently to changing CO2 concentration. • However, in both cases the photosynthetic rate increases with increases in CO2 concentration.
  16. 16. B) Effect on rooting pattern • High carbon gain might increase root length, diameter and number and number and stimulate lateral growth production in plants grown under elevated CO2. • A shift in biomass may occur from leaves to roots under CO2 enrichment. • Root/shoot ratio increase.
  17. 17. C) Effect on leaf and stomata • Increased leaf area index, leaf duration , leaf thickness etc is generally observed. • Elevated CO2 also increase mesophyll and chloroplast content in leaves. • Partial closure of stomata may occurs due to rising CO2 concentration. • Due to this evapotranspiration rate is reduced to upto 10% but also less air pollutants enter into the cell.
  18. 18. Negative impacts • The few negative impacts are: • Increasee CO2 concentration will decrease the rate of seed germination. • Food quality is declining under the rising level of CO2. • According to some reasearches, 14% increase in lead and 8% drop in iron content of the crop is observed.

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