Characterisation of organic carbon
The characterisation of organic carbon in soils, waste materials and (secondary) building materials is an important aspect within research program of the Environmental Risk Assessment group at ECN. From our point of view, the total content of contaminants in a material is only of minor importance regarding to the environmental impact. The amount of contaminants that can be released from a material due to leaching processes is the key factor for environmental risk assessment of materials used in construction or being stored in disposal. Understanding the geochemical processes in these materials greatly enhance the prediction of the long-term leaching behaviour. The release of inorganic and organic contaminants from soils, (secondary) building- and waste materials is controlled to a large extent by the release of dissolved organic carbon (DOC). We have shown earlier that copper in MSWI bottom ash leachates binds very strongly to organic ligands and that copper leaching is primarily controlled by the availability of organic ligands. The properties of organic matter that contribute to the release of DOC (and facilitated contaminant leaching) are, therefore, important for environmental risk assessment.DOC is a sum parameter for all organic species in solution, examples are sugars, carbohydrates, organic acids, amino acids, lignin and humic- and fulvic acids. In natural systems (soil and water), it has been shown that particularly humic- and fulvic acids (or humic substances) have a high affinity for the binding of heavy metals and organic micro-pollutants (e.g. PAH and PCB).