Distribution and incorporation mode of the herbicide MCPA in soil derived organo-clay complexes |
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Authors: | Patrick Riefer Timm Klausmeyer Burkhard Schmidt Andreas Schäffer |
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Institution: | 1. Institute of Geology and Geochemistry of Petroleum and Coal, RWTH Aachen University, Aachen, Germany;2. Institute for Environmental Research (Biology 5), RWTH Aachen University, Aachen, Germany |
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Abstract: | The incorporation of xenobiotics into soil, especially via covalent bonds or sequestration has a major influence on the environmental behavior including toxicity, mobility, and bioavailability. The incorporation mode of 4-chloro-2-methylphenoxyacetic acid (MCPA) into organo-clay complexes has been investigated under a low (8.5 mg MCPA/kg soil) and high (1000 mg MCPA/kg soil) applied concentration, during an incubation period of up to 120 days. Emphasis was laid on the elucidation of distinct covalent linkages between non-extractable MCPA residues and humic sub-fractions (humic acids, fulvic acids, and humin). The cleavage of compounds by a sequential chemical degradation procedure (OH?, BBr3, RuO4, TMAH thermochemolysis) revealed for both concentration levels ester/amide bonds as the predominate incorporation modes followed by ether linkages. A possible influence of the soil microbial activity on the mode of incorporation could be observed in case of the high level samples. Structure elucidation identified MCPA as the only nonextractable substance, whereas the metabolite 4-chloro-2-methylphenol was additionally found as bioavailable and bioaccessible compound. |
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Keywords: | MCPA residues non-extractable residues chemical degradation organo-clay complexes soil particle fractions |
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