Download
introduction to soils and soil resources n.
Skip this Video
Loading SlideShow in 5 Seconds..
Introduction to Soils and Soil Resources PowerPoint Presentation
Download Presentation
Introduction to Soils and Soil Resources

Introduction to Soils and Soil Resources

168 Views Download Presentation
Download Presentation

Introduction to Soils and Soil Resources

- - - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript

  1. Introduction to Soils and Soil Resources 2001 Lecture 7 Soil Air and Soil Organic Matter

  2. Table 9.1. Relative concentrations of atmospheric gases on Earth, Mars and Venus Credit: after Margulis and Hinkle, 1991

  3. Oxidation • Oxidation: A reaction in which atoms or molecules gain oxygen, or lose hydrogen or electrons Fe 2+ = Fe 3+ + e-

  4. Reduction • Reduction: A reaction in which atoms or molecules lose oxygen, or gain hydrogen or electrons: N2 + H2 = NH3

  5. Oxidation State • In a free state, oxidation state is zero. For example elemental sulfur (S0) • Monoatomic ions have oxidation state equal to the ionic charge. For example, Ca2+ has oxidation of +2

  6. Oxidation State • In a combined state, hydrogenhas oxidation state of +1; oxygen has oxidation state of -2 • For example: H2O • For example: H2SO4 (S = +6)

  7. Examples • Oxidation and reduction reactions occur in nature • Responsible for energy transformations • Examples are given in Table 9.2

  8. The atmosphere • The atmosphere is a large, layer system • Troposphere (80% air mass) • Stratosphere (Ozone region) • Mesosphere • Thermosphere

  9. Fig. 9.1. The profile of the atmosphere

  10. Fig. 9.2. Radiation Budget

  11. Greenhouse gases • Water vapor (H2O) • Carbon dioxide (CO2) parts per million • Methane (CH4) parts per million • Ozone (O3) parts per million • Nitrous oxide (N2O) parts per billion • Halocarbons (CFC’s) parts per trillion • Refer to Table 9.3 (Section 9.3)

  12. Fig. 9.3. Active sites, mineral particles and water films

  13. Atmospheric Air vs Soil Air (% volume)

  14. Soil Atmosphere • The soil atmosphere is different from the atmosphere (Table 9.4 in Section 9.4) • Soil is a biologically, porous medium • Activities of plant roots and soil biota change soil atmosphere • Metabolic pathways change if oxygen is limiting (Fig. 9.3 in Section 9.4)

  15. Aerobic Respiration C6H12O6 + O2 6 CO2 + 6 H2O + energy

  16. Anaerobic Respiration NO3- NO2- NO  N2O  N2 5 3 2 1 0 Nitrate is terminal electron acceptor when oxygen is limiting

  17. Gas Conc. (% vol.): Corn field Elliott and McCalla 1972. Soil Sci. Soc. Am. Proc. 36:68

  18. Gas Conc. (% vol.): Feedlot Elliott and McCalla 1972. Soil Sci. Soc. Am. Proc. 36:68

  19. Gas Dynamics • Normally O2 decreases and CO2 increases with depth • Normally, CO2<0.5% in soil atmosphere while O2 >10%

  20. Soil Organic Matter

  21. Air 25% Mineral Mineral 45% Organic Water Air Water 25% Organic 5% Soil: Major Components

  22. Soil Organic Matter • All organic substances, by definition, contain carbon • The element carbon is the foundation of all life

  23. Soil Organic Matter • SOM consists of living or dead plant material,living organisms, microbial and faunal products, and stabilized complex organic matter called humus • Organic matter has a profound impact on soil physical, chemical and biological properties

  24. Credit: U of A Extension & Pedosphere.com

  25. Physical Properties • The physical properties of soil horizons vary tremendously within a pedon • Example is given in Table 11.2 in Section 11.2

  26. Soil C • Present as organic matter • Present as inorganic carbon in form of carbonates in some soils • Example is given in Table 11.3 in Section 11.2

  27. OM Impacts • Formation of organo-mineral complexes • Aggregation • Cation and anion exchange capacity • Movement of pollutants • Decomposition and nutrient cycling (next lecture)

  28. Fig. 1.9. Pores and particles in soil (Pawluk) Credit: Pedosphere.com

  29. Porosity/Structure

  30. Fig. 6.12. Structure of a model humic acid (Schulten & Schnitzer, 1997)

  31. Fig. 6.10. Impact of soil pH on net charge oforganic acids

  32. Charge Characteristics * cmolc/kg

  33. Application • Given a soil with 5% OM and 20% montmorillonite clay. Calculate total negative charge. • Charge = 0.05(200) + 0.20(100) = 10 + 20 = 30 cmolc/kg

  34. Soils & the Global C cycle

  35. How much organic C is present in this landscape?

  36. How much organic C is present in the Prairies?

  37. How Much C is present in Canadian Soils? Credit: Acton and Gregorich (1995)

  38. Credit: Ecological Monitoring & Assessment Network

  39. Fig. 5.14. A Catena Credit: Rennie and Ellis (1995)

  40. Global Carbon Cycle: Units • Units:1 ton = 1 x 103 Kg = 1 x 106 g • 1 gigaton (Gt) = 1 billion tons = 1 x 109 tons 1 Gt = 1 x 109 tons1 ton = 1 x 106 g1 Gt = 1 x 1015 g = 1Pg (petagrams)

  41. Fig. 11.2. The Global Carbon Cycle

  42. Global Carbon Cycle: Pools • Atmosphere:750 Pg • Vegetation: 610 Pg • Soil: 1,580 Pg • Fossil Fuels: 5,000 Pg • Oceans (organic)1,020 Pg • Oceans (inorganic) 38,100 Pg • Carbonate Rocks1 x 106 Pg

  43. Fig. 11.2. The Global Carbon Cycle

  44. Global Carbon Cycle: Fluxes (Pg/yr) • Atmosphere to vegetation 61.4 • Vegetation to atmosphere 60 • Deforestation (loss) 1.6 • Change in land use (gain) 0.5 • Fossil Fuel combustion 5.5

  45. Fig. 11.2. The Global Carbon Cycle