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Describing Redoximorphic Features

Describing Redoximorphic Features. Prepared by: Mr. Brian Oram Wilkes University http://www.water-research.net. Goals of Presentation. What is a redoximorphic feature? What is the difference between mottling and redoximorphic features? How do these features form?

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Describing Redoximorphic Features

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  1. Describing Redoximorphic Features Prepared by:Mr. Brian OramWilkes University http://www.water-research.net

  2. Goals of Presentation • What is a redoximorphic feature? • What is the difference between mottling and redoximorphic features? • How do these features form? • What do these features mean and how can we use?

  3. Is this motting or a redoximorphic feature? Answer: Both

  4. Is this Mottling or Redoximorphic Feature Color variationis not always a Redoximorphic Feature ! Mottled Color Pattern – Variation in Grain Size, Moisture Content, and Amount of Coatings

  5. What Was the Difference? Associated with alternating periods of unsaturated and saturation conditions, variation in moisture, textural variation, but under aerobic conditions. Associated with alternating periods of unsaturated and saturation conditions with alternating aerobic and anaerobic conditions.

  6. Therefore, • A redoximorphic feature is a feature formed under a set of conditions that indicates that the soil has been saturated and anaerobic for some period of time. • Does it tell us how long ? Not really! • The term redoximorphic replaces the old terms: mottles and low chroma colors.

  7. Formation of Redoximorphic Features • To form redoximorphic features we needed all of the following: • Decomposable organic material is present. • Bacteria are active (Proper temperature and environment- above biological zero- > 42 F). • Soil is saturated. • Soil is Anaerobic – stagnant water or water with a low flow. If one of these factors or conditions are not present – No Redoximorphic Features Form. The reactions we are going to discuss are oxidation and reduction reactions.

  8. Oxidation and Reduction Reactions • Influence Soil Colors • Control and Influence the amount of Oxygen, Nitrogen, Iron, Manganese, Sulfate, and Carbon in the soil. • Responsible for denitrification, formation of sulfur or rotten egg odors, and creation of methane gas. • Formation of features we can use to estimate the depth to saturated and anaerobic conditions and a rough estimate the depth to the water table.

  9. Oxidation and Reduction Reactions • In these reactions: The electrons from one substance is removed and transferred to another substance. • Examples: • Aerobic Environment Organic material is consumed by bacteria and the bacteria release hydrogen ions and electrons (e-). The electron reacts with the oxygen and hydrogen to form WATER (H20). 02 (air) + 4 e- + 4H+ == 2H20 In this reaction, oxygen is reduced to form water and the carbon or food for the bacteria is oxidized. • Anerobic Environment Organic material is consumed by bacteria and the bacteria release hydrogen ions and electrons (e-). The electron reacts with the nitrate and hydrogen to cause Denitrification -Great We are Getting Rid of Nitrogen. 1 NO3- + 10e- + 12 H+ = N2 (gas) + 6 H20

  10. Oxidation and Reduction Reactions- The Order of Reactions • As the soil becomes saturated, oxygen is the first ion to be reduced. • After the soil is saturated and anaerobic, the order of reduction is as follows: • Nitrates • Manganese (Mn02) • Iron (Fe2O3) • Sulfate • Carbon Dioxide Therefore – a saturated soil with reduced iron –indicates the oxygen, nitrate, and manganese has been reduced, but the sulfate and carbon dioxide is style in an oxidized state. How can we use this knowledge ????

  11. How do we use ? The Answer: Iron Prismatic Soil StructureRedoximorphic feature associated with the oxidation and reduction of iron. Anaerobic Saturated ConditionsFe203+4e- +4H+ = 2Fe+2 +3H20 When the soil aerates or as reduced Iron diffuses, the iron reoxidzes. Creates Zones of Depletion and ZonesOf Concentration.

  12. How do we use ? The Answer: Iron – Close UP ! Zone of Depletion- Iron Reduced and/or Removed (Gray) Matrix Color (Predominate Color) Zone of Accumulation (Redder) These observation indicates the either the soil mass or zones in the soil has areas within the soil that are both saturated for a sufficient period of time for the soil to become anaerobic.

  13. What the Data Means or Suggests. Monitoring Shows Saturated Conditions Extend To this Zone. Saturated Aerobic Redoximorphic Features Observed Saturated and Anaerobic Observed Saturated Conditions During Testing

  14. Describing Redoximorphic Features Prepared by:Mr. Brian OramWilkes University http://www.water-research.net

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