Influence of microbial activity on the structure-chemistry and chemodynamics of nonextractable residues of xenobiotics in soil derived organo-clay complexes
Principal investigators: Prof. Dr. A. Schäffer, PD Dr. J. Schwarzbauer, Prof. Dr. P. Corvini
Co-workers: Dr. B. Schmidt, Dipl.-Biol. T. Klausmeyer, Dipl.-Chem. P. Riefer
Aims of the project
Organo-clay complexes in soil play a major role in the immobilisation and the persistence of xenobiotics and their metabolites. The project will contribute to understand the interactions in such complexes with a special attention to the spatial and structural arrangement of humic substances within organo-clay complexes which we expect to govern the sorption and binding of xenobiotics and their reactive metabolites. We will study the biogeochemical and chemodynamical behaviour of MCPA, NP and their metabolites during the formation, release and degradation of residues covalently bound to natural and model humics-coated clay.
Overview of the project
In the project we will use two substances, which exhibit a phenol-related structure. The first substance MCPA (4-chloro-2-methylphenoxy)acetic acid is widely used as a herbicide. It has been chosen as hydrophilic model substance for this project. Working with this compound will possibly allow for the extension of the knowledge acquired in the frame of this project to other structurally related phenoxy herbicides. Although MCPA will not sorb strongly to soil components, phenolic metabolites of MCPA will lead to significant amounts of non-extractable residues in soil.
The second substance is nonylphenol (NP). The endocrine disrupting chemical is ubiquitously distributed in the environment. NP is mainly found as a highly persistent microbial degradation product of NP polyethoxylate (NPnEO) surfactants used to a lower extent also for pesticide formulation. In practice NP is a technical mixture of 22 isomers. The main substance is 353-NP, which has the same estrogenic activity as the technical mixture.
Spiking experiments will be carried out by applying 13C- and 14C-labelled mixtures of single compounds to natural soils as well as to natural and model clay-humin complexes. 13C-labelled compounds may be necessary in order to attenuate signal to noise (natural 13C content of the organic matrix) for 13C-NMR analyses and furthermore for GC/MS based structure elucidation analysis. 14C-labelled substances are used for the recovery and assignment of bound/unbound molecules as well as for radioactivity balancing. Non-extractable radioactivity remaining in the solid phase will be measured after combustion of aliquots of the samples in an oxidizer and subsequent LSC analysis of the mineralised 14CO2 .
For this project soils will be used from Ultuna, Sweden, and Fuhrberg, Germany.
Riefer, P., Klausmeyer, T., Schwarzbauer, J., Schäffer, A., Schmidt, B., Corvini, P.F.X. 2011. Rapid incorporation and short-term distribution of a nonylphenol isomer and the herbicide MCPA in soil-derived organo-clay complexes. Environ. Chem. Lett. 9, 411-415.
Riefer, P., Schwarzbauer, J., Schäffer, A., Klausmeyer, T., Schmidt, B. 2011. First evidence for a stereoselective incorporation of nonylphenol diastereomers in soil-derived organo-clay complexes. Environ. Chem. Lett. 9, 293-299.
Riefer, P., Klausmeyer, T., Schäffer, A., Schwarzbauer, J., Schmidt, B. 2011. Distribution, fate and formation of non-extractable residues of a nonylphenol isomer in soil with special emphasis on soil derived organo-clay complexes. J. Environ. Sci. Heal. B 46, 394-403.