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Soil Pollution


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soil pollution, pollution transport process, breakthrough curve

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Soil Pollution

  1. 1. Soil Pollution By 1305053 Tahmid Imran Imon Land Reclamation Engineering
  2. 2. What is Soil? Soil is unconsolidated natural bodies or materials Forming by natural action By weathering process Composed of mineral matter, organic matter, air and water Differentiated by different horizons. 2 Fig 1: Soil
  3. 3. What is Soil Pollution?  The change in physical , chemical and biological conditions of the soil  Through man’s or natural intervention  Resulting in degradation in quality. 3 Fig 2: Soil Pollution
  4. 4. Causes 4 MANMADE CAUSESNATURAL CAUSES Fig 3: Natural Pollution Fig 4: Manmade Pollution
  5. 5. 5 Fig 5: Chart of pollution caused by humans and nature
  6. 6. Soil Pollution Around The World 6Fig 6 : Soil Pollution Around The World
  7. 7. Sources of Soil Pollution Industrial Wastes-  fly ash,  organic compound, inorganic complexes, non-biodegradable material Urban Waste-  Domestic waste  Solid waste- garbage and rubbish material-plastic, glasses, metallic cans, fibers, paper, rubbles, fuel residues, leaves, containers. Radioactive Pollutants-  Nuclear dust and radioactive waste  Thorium, Uranium, Carbon (C-14) substance in soil, rock, water and air  Nuclear fission, heavy water (Sr-90, Cs-137) cause gamma radiation. 7
  8. 8. Sources of Soil Pollution Agricultural Practices-  Pesticides, insecticides, weedicides and herbicides  Toxic metal-lead, arsenic, mercury, cobalt, cadmium, cyanide etc. Chemical and Metallic Pollutants-  Different type chemical, metallic and fertilizer industries.  Organic and Inorganic pollutants (Fe, Cu, Co, Zn, Hg, As, Ni, Cd, Pb, alkalis and acid etc.) Affect soil texture, fertility and stabilization of soil. Biological Agents-  Large quantity of animal, birds and human etc. cause land pollution  Leached in soil and cause chronic salts hazardous to plants and animal.  Pathogenic organism by naturally, Pathogenic organism by human , Pathogenic organism by animal . 8
  9. 9. Sources of Soil Pollution  Soil Erosion-  Natural process of detachment and removal of soil material (water, wind, ice or gravity).  Due to running of water, wind, ice or geological agent.  Agriculture development, construction and mining activities.  Acid Rain-  Air pollution- motor vehicle, factory emission etc. cause acid rain (HNO3, H2SO4)  Other Sources-  Absorption of toxic metal  Soluble salts, Mining  Wastewater applied soils  Solid waste applied soils,  Food processing waste,  Sugarcane trash in field,  Municipal garbage & composed etc. 9
  10. 10. Types of Soil Pollution Agricultural Soil Pollution i) pollution of surface soil ii) pollution of underground soil Soil pollution by industrial effluents and solid wastes i) pollution of surface soil ii) disturbances in soil profile Pollution due to urban activities i) pollution of surface soil ii) pollution of underground soil 10
  11. 11. Fig 8: Excess application of pesticides Fig 9: Excess use & disposal of Plastics and Polyethene wastes Fig 7: Drought Fig 10: Disposal of oil 11
  12. 12. Fig 12: Industrial wasteFig 11: Solid waste Fig 14: Volcanic eruptionFig 13: Mining 12
  13. 13. Pollutants in Soil  Chemical and metallic pollutants o Different type industries o Metallic industries o Inorganic pollutants (Fe, Cu, Co, Zn, Hg, As, Ni, Cd, Pb, alkalis and acid etc.  Agro-chemicals o Pesticides, insecticides, weedicides and herbicides o lead, arsenic, mercury, cobalt, cadmium, cyanide. 13
  14. 14. Pollutants in Soil  Radioactive material o Thorium, Uranium, Carbon (C-14) etc.  Biological agents o Algae, fungi, bacteria, protozoa, viruses, nematodes, worm etc. o Industries waste, o Enter in air, water and food chain. 14
  15. 15. Common chemicals causing soil pollution  Petroleum hydrocarbons  gasoline,  jet fuels,  mineral oils etc.  Heavy metals  arsenic,  cadmium,  led etc. 15 Fig 15: Gasoline Fig 16: Cadmium
  16. 16. Common chemicals causing soil pollution  Pesticides  bifenthrin,  captan,  carbaryl etc.  Solvent  toluene,  turpentine,  acetone,  methyl- acetate etc. 16 Fig 17: Turpentine Fig 18: Carbaryl
  17. 17. Pollution Transport Process There are many processes that contributes the movement of soil pollution. Among these 3 main physical process are: 1) Convection 2) Diffusion and 3) Dispersion. 17
  18. 18. Convection The process by which heat is transferred by the movement of heated fluid.  In pollution transport system we focus on the convection as vertical movement of air.  In environmental studies, mainly in meteorological studies convection also includes horizontal movement of fluid. 18Fig 19: Convection
  19. 19. Pollution by Convection Pollutants mixes with air Air gets warm and light It rises up Becomes cold Condenses Forms convictive cloud Falls in the earth and waterbodies with pollutants 19Fig 20: Pollution by convection
  20. 20. Diffusion  Diffusion means mixing and spreading out.  The diffusion of gases and liquids refers to their mixing without external force.  Diffusion is the process through which pollutant molecules move through air or water.  As the molecules move, they eventually strike other Molecules which sends them in opposite ways.  Diffusion moves pollutants from high concentration to low concentration, spreading them out 20Fig 21: Diffusion
  21. 21. Pollution by Diffusion  Consider the dye in this picture as pollutant.  Which is dropped in the jar of fresh water.  The dye will dissolved in the water uniformly.  After sometimes the dye will mix in such manner  That the mixture can not be traced back to single source.  In this process the pollutants moves through the soil in fluid form, causing soil pollution. 21Fig 22: Pollution by diffusion
  22. 22. Dispersion Dispersion is a mixture In which fine particles of one substance are scattered throughout another substance. A dispersion is classed as a suspension, colloid, or solution. 22Fig 23: Dispersion
  23. 23. Pollution by Dispersion  Dispersion is caused by different flow paths that a fluid takes in a geological medium.  Some paths are fast as the fluid may pass through the big pore spaces.  Some paths are slow as the fluid may encounter friction while passing through the narrow paths.  During the flow different pollutant may come in contact with the fluid hence cause soil pollution. 23Fig 24: Pollution by dispersion
  24. 24. Mathematics  The bulk motion of the fluid, and controls contaminant transport through the soil column by molecular diffusion and mechanical dispersion.  In this study selenium, nitrogen and pesticide were modeled.  Steady–state water flow condition the transport terms for selenium are: ………. (1) Where, Js = total selenium flux, JDL = the diffusion flux in the liquid phase and JCL = the convection flux in the liquid phase. 24
  25. 25. Mathematics  In the case of diffusion in a porous media, the equation represented by, ………….(2) Where, CL = concentration in the liquid phase and DM(θ) = the molecular diffusion coefficient  The value of DM(θ) can be estimated as: ………….(3) Where, DOL = the diffusion coefficient in a pure liquid phase and a, b = empirical constants 25
  26. 26. Mathematics  The convective flux of selenium can be represented as: ………….(4) Where, q = the water flux, and Dh (q) = hydrodynamic dispersion coefficient  Combining the diffusion coefficient and dispersion coefficient as: ………….(5) Where, D (θ, q) = the apparent diffusion coefficient 26
  27. 27. Mathematics  Substituting equations (2), (4)and (5) into equation (1) the overall selenium flux is given as: ………….(6)  Partitioning selenium between absorbed and solution phases, adsorption of selenium are assumed taken to be nonlinear equilibrium process described by: ………….(7) Where, Cs = the concentration of selenium absorbed on the soil Ks = the adsorption coefficient for selenium, C = the concentration of selenium in the soil solution n = exponent for selenium. 27
  28. 28. Mathematics  The total amount of selenium (CT) contained in the solution and adsorbed phases in a soil volume of one liter are: ………….(8) Where, ρ = the soil bulk density  Substituting equation (7) for Cs in equation (8) one can get the convection- dispersion equation: ………….(9)  Selenium transports in soil system occur under unsteady water flow condition. The water content (θ ) and water flux (q) both vary with depth and time. 28
  29. 29. Mathematics  Using continuity relationships of mass over space and time gives: ………….(10) Where, CT = total selenium concentration in sorbed and Φ = solution phases and represents all sources of selenium.  Substituting equation (4) and (9) into (10) gives general one-dimensional transport equations for selenium transport: ………….(11) Where, C = concentration of all selenium species in soil solution, Φ = solution phases and represents all sources of selenium. 29
  30. 30. Mathematics  The above equation is in general form, similar equation can be written for different nitrogen and pesticides species in soil column.  One dimentional water Flow and contaminant transport model was applied to simulate Selenium in soil column.  The equation predicts the concentration of different contaminant. 30
  31. 31. Breakthrough Curve  When you infiltrate a solution of some substance in to packed bed column  The solution travels through the pore spaces from inlet to outlet.  Some of the solution will travel faster than average  Some slower than average, because some routes are faster than others.  The breakthrough curve is a plot of the concentration measured at a fixed point in the column  Usually at or near to the outlet, versus time.  It is a “S” shaped curve. Fig 25: Breakthrough Curve
  32. 32. Breakthrough Curve Analysis Breakthrough happens when an adsorption column is saturated. So,  First pass a solution through a column of substance with a constant flow rate.  The solution will travel through the pore spaces of the substance.  Some solution will travel faster and some will be slow due to the friction and size of the pore spaces.  As the column gets saturated, the solvent starts appearing.  The concentration is usually measured near or at the outlet 32
  33. 33. Breakthrough Curve Analysis 33Fig 26: Breakthrough Curve Analysis
  34. 34. Breakthrough Curve Analysis  Find how much volume can pass per minute or second (mL/min).  Then begin to pass your solution and collect each 10 mL.  Then draw the results of your analyzed target with the time using your flow rate.  It is usually a S shape curve  When this curve no longer changes, the column is saturated.  Specifically you can look at the slope of the central part of the S curve.  When the slope stays constant, you've achieved column saturation. 34
  35. 35. References ₪ International Journal of Environmental Science & Technology ₪ Soil contamination – Wikipedia ₪ Google image – soil pollution ₪ – soil pollution ₪ - Soil pollution ₪ List of Pollutants • Environmental Pollution - Tropical Rainforest Animals ₪ ₪ ₪ ₪ ₪ ₪ 35
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