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Mark Campbell

Constructed Wetlands and the soil properties and biogeochemical processes that increase efficiency in Nitrate removal . Mark Campbell. Brief Intro of Wetlands. Turkey Creek Wetland A restored floodplain wetland at a private farm in rural McLean County, Illinois. Characteristics of Wetlands.

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Mark Campbell

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  1. Constructed Wetlands and the soil properties and biogeochemical processes that increase efficiency in Nitrate removal Mark Campbell

  2. Brief Intro of Wetlands Turkey Creek Wetland A restored floodplain wetland at a private farm in rural McLean County, Illinois

  3. Characteristics of Wetlands • Wetlands are transitional areas between land and water • Main Characteristic present of surface or near-surface water, at least periodically • The hydrology of wetlands is generally one of slow flows and either shallow waters or saturated substrates • Also forms an Anaerobic environment

  4. Benefits Costs • Provides the removal of contaminants: Nitrates, Phosphorous, metalloids • Allows for sedimentation to occur • Low Cost Removal as opposed to Ion-Exchange • Control of Flooding • Ecosystem for wildlife • Loss of Land use $$$$ • Aesthetic Value

  5. Soil Profile Permeability

  6. Differences between Soils in Constructed and Natural Wetlands 5 cm Depth 20 cm Depth Campbell et al (2002)

  7. Comparison • It was also found that the diversity of plant communities were higher in reference sites • Even in long-term CW’s the organic matter did not reach levels of reference sites • This has shown to be an indicator of removal of nitrogen (Reddy and D’Angelo 1997).

  8. Another comparative study O’Geen et al (2007)

  9. What is the chemistry that goes on that in hydric soils that helps with denitification?

  10. Factors that affect Denitrification rates • Temperature • With season, can not control, lower temp. lower rate • pH • pH in natural waters is in the between 6 to 8, optimal pH for denitrifying bacteria • Redox Potential • Organic Carbon and Dissolved Oxygen • Retention time/Flow Rate

  11. Biochemistry • Organic Material is oxidized by aerobic respiration use Oxygen as the electron receptor, while anaerobic conditions use Nitrogen as receptor (Metcalf and Eddy 2003). • Corganic + 4 NO3- + 4H+ = 2N2 + 5CO2 + 2H2O • Pseudomonas • Thiobacillus

  12. Constructed wetlands have found to remove ≈40% of NO3-ther is a high degree of variability there have been reports of up to 75% and low of 15% (Kovacic et al. 2000)

  13. Effects of DO and TN Removal H. C. Kim et al. (2010)

  14. Flow Rate and Retention Time • During pulse flows, in the case of storm events the amount of denitrification is greatly reduced (Kovaic 2006). • Still wetlands need slow flow, to have some mixing in the water. Need to create anaerobic environment. • The average retention time 6-8 days for optimal conditions (Zedler 2003). • Horizontal substrate is more important, while increase in depth lowers efficiency(Garcia et al 2010).

  15. Substrate soils for CW Since high levels of nutrients Sand and Gravel- cheap Soils with high clay content- good at retaining phosphorous Organic Substrate- sawdust, compost, or hay. USDA-NRCS Handbook for constructed wetlands

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