Effects of soil organic matter molecular conformation and substrate additions on the formation and release of xenobiotics bound residues

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The sorption properties of soil organic matter (SOM) for hydrophobic organic contaminants (HOCs) can be modified by saturating the exchange sites with differently charged cations because this alters the molecular conformation of the organic matrix. Interactions with minerals can further influence the conformation and properties of SOM. These interactions are assumed to increase with aging and it will here be tested if they will also affect the formation of HOC bound residues and their biodegradability. Batch sorption experiments of ferrihydrite and montmorillonite with soil extracts, soil slurries and soil samples will be carried out to determine sorption of SOM to the minerals. The newly formed organo-mineral interfaces are characterized in terms of their sorptive properties for a hydrophobic (phenanthrene) and a polar compound (MCPA) and their physico-chemical properties (i.e. contact angle, glass transition temperature) in close cooperation with other SPP applicants. The main focus of this phase will be to set up a jointly planned long-term aging experiment where the interactions of cation treatments, minerals and biological activity on the formation and properties of organo-mineral interfaces and phenanthrene bound residues will be determined.