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Physico-chemical properties of environmental compartments

Physico-chemical properties of environmental compartments. Soil/ sedimenary organic matter. Aims: To provide knowledge about main components of environmental compartments (soil/sediments) Outcomes:

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Physico-chemical properties of environmental compartments

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  1. Physico-chemical properties of environmental compartments Soil/sedimenary organic matter

  2. Aims: • To provide knowledge about main components of environmental compartments (soil/sediments) • Outcomes: • Students will understand the main properties of components of environmental compartments (soil/sediments) Environmental processes / Pollutants and environmental compartments (i)

  3. Environmental processes / Pollutants and environmental compartments (i)

  4. Soil/Sediment Organic Matter (SOM) • Content: • ~0 to 5% of most soils • Up to 100% of organic soils (histosoils) • Higher in moist soils and northern slopes • Lower in drier soils and southern slopes • Cultivation reduce SOM • High surface area and CEC • High content of C and N Environmental processes / Pollutants and environmental compartments (i)

  5. Environmental processes / Pollutants and environmental compartments (i)

  6. Environmental processes / Pollutants and environmental compartments (i)

  7. Environmental processes / Pollutants and environmental compartments (i)

  8. Fig 3.3 Four theories on how humic substances are formed Pathway 1: probably not important Pathways 2 & 3: polymerization of quinones, probably predominant in forest soils Pathways 4: Classical theory, probably predominant in poorly drained soils Environmental processes / Pollutants and environmental compartments (i)

  9. Negative charge comes primarily from ionization of acid functional groups (e.g. hydroxyl, carboxyl) Environmental processes / Pollutants and environmental compartments (i)

  10. SOM structures soil humic acid black carbon (soot, HSACM) seawater humic Environmental processes / Pollutants and environmental compartments (i)

  11. SOM properties • Voids can trap • Water • Minerals • Other organic molecules • Hydrophobicity/hydrophilicity • Reactivity • H-bonding, chelating of metals Environmental processes / Pollutants and environmental compartments (i)

  12. Functional groups and charge characteristics • PZC ~ 3 (pH of zero charge) • Up to 80% of CEC in soils is due to SOM • Acid functional groups • Carbonyls pKa < 5 • Quinones also pKa < 5 • Phenols pKa < 8 • SOM constitutes most of the buffering capacity of soils Environmental processes / Pollutants and environmental compartments (i)

  13. Environmental processes / Pollutants and environmental compartments (i)

  14. Source In The Handbook of Environmental Chemistry: Aboul-Kassim, T.A.T., Simoneit, B.R.T., 2001. Chemistry and Modeling. Springer-Verlag, Berlin. P107-167. ISBN: 3-540-41650-1 Environmental processes / Pollutants and environmental compartments (i)

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