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08:38
Combined Size and Density Fractionation of Soils for Investigations of Organo-Mineral Interactions
Published on: February 15, 2019
Dioxins in primary kaolin and secondary kaolinitic clays
Martin Schmitz1, Georg Scheeder, Sarah Bernau
1Federal Institute for Geosciences and Natural Resources (BGR), Hannover, Germany. martin.schmitz@bgr.de
Environmental Science & Technology
|December 4, 2010
Summary
Naturally occurring dioxins (PCDD/F) in Tertiary ball clays are enriched during sedimentation, not from human sources. This study presents a model explaining variable dioxin levels in kaolinitic clays based on natural processes.
Area of Science:
- Environmental Science
- Geochemistry
- Organic Chemistry
Background:
- Dioxins (PCDD/F) detected in Tertiary ball clays since 1996, with origins unclear.
- Anthropogenic sources are unlikely; a natural enrichment model is needed.
Purpose of the Study:
- To test a hypothesis of natural dioxin enrichment during clay sedimentation.
- To investigate factors influencing dioxin levels in kaolinitic clays.
Main Methods:
- Collected and analyzed primary kaolin and sedimentary kaolinitic/lignitic clays from European profiles.
- Assessed mineralogy, chemistry, organic carbon, and PCDD/F concentrations.
Main Results:
- PCDD/F levels varied significantly: primary kaolin (3-91 pg/g), secondary kaolinitic clay (711-45935 pg/g), lignitic clays (13513-1191120 pg/g).
- Dioxin concentrations followed a 'natural formation pattern', decreasing from highly chlorinated to less chlorinated congeners.
- No correlation found between PCDD/F levels and bulk clay composition.
Conclusions:
- Findings support the hypothesis of dioxin enrichment during natural clay sedimentation.
- Sedimentary processes are the primary driver of high dioxin concentrations in these clays.
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