Soil Chemistry and Chemical Soil Quality



soil structure (aggregate formation)

   Soil chemistry
and
chemical soil quality

                                                                                       

      
  Adsorbed PO4 on Goethite (molecule structure)                    

Cyanide pollution, what are the effects?
    Chair group 

    group leader: prof W.H. van Riemsdijk

Humic acid (molecule structure)


Chemical substances (nutrients, contaminants) interact with reactive soil particles, e.g. with organic matter, clay, iron(hydr)oxide and aluminiumhydroxide. This will affect their bioavailability and mobility in the soil. Also soil particles interact with each other, e.g. organic matter adsorbs onto iron(hydr)oxide. This affects soil structure (formation of soil aggregates).

 

We study the speciation of compounds in the soil by fundamental research and by more practically motivated studies. Research projects focus mainly on modelling adsorption (new model concepts: CD-MUSIC, NICA-Donnan, LCD; computer models used: ECOSAT and Orchestra) and on chemical analysis (new method: DMT = Donnan Membrane Technique) and soil particle characterization (new method: asymmetric flow FFF). With the multi surface modeling approach (organic matter + clay + iron(hydr)oxides) compound behaviour can be described rather satisfactory.


Info poster DMT   

 

 

  
The CD-MUSIC model describes adsorption of charged compounds (heavy metals, phosphate, arsenate, etc.) on charged metal(hydr)oxides. The NICA-Donnan model describes the binding of (heavy) metals on organic matter taking into account the heterogenic nature of organic matter in the soil, including DOC (Dissolved Organic Carbon).
The LCD model is developed to describe the binding of organic matter molecules (e.g. Fulvic or humic acid) onto the charged surface of metal(hydr)oxides. 

The animation shows the adsorption of fulvic acid on goethite and at the same time the desorption of phosphate (PO4). Protons are released.
More information: Weng et.al., EST, 2008

        
Pot experiment showing effects of copper and pH on growth of grass.        
                   

The presence of contaminants in the soil environment has been a concern for many years. The activities of man, particularly since the industrial revolution, have led to a substantial increase of trace elements and organic contaminant loadings of soils, both by diffuse (airborne) and local emissions. In addition, human activities lead to the production of large and ever increasing volumes of waste materials (e.g. from various domestic, industrial and mining activities, as well as energy production), which also contain elevated levels of such substances. These waste materials generally enter the soil environment by either land-filling or by their beneficial utilization in construction applications such as building materials and road bases.      

 

Major research challenges:

  • to identify the underlying processes that control the actual risks of contaminant mobility and bioavailability in the soil environment
  • to develop methods for the measurement and/or prediction of the relevant contaminant fractions (“speciation”) and the associated risks of contaminant migration and uptake by biota 


The applicability for real world problems is diverse. Usually, the problems studied concern the fate of nutrients or contaminants. However, also soil formation problems, aspects of risk analysis and soil protection, soil fertility/fertigation, etc. may benefit from the outcome of this research

Research projects:  

  
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