General Cleanup Technology

Biological decontamination of NAPL-contaminated soils by the determination of the radon concentration in the soil air

Characteristic variations in radon concentration may be observed in the course of biological soil recycling processes. However, the order of magnitude of these variations is significantly smaller than anticipated, and the latter can only be quantified using ionization chamber measuring apparatus.

Summary

During the decontamination of soils which are contaminated with mineral oil hydrocarbons, hydrocarbon degradation is determined by the regular analysis of soil samples.  Since the results obtained by this method are influenced by numerous marginal conditions associated with the extraction of samples from spoil heaps, these results will often constitute an inadequate force of expression.

The objective of this project was the replacement of the chemical analysis of individual soil samples by the investigation of gases present in the pore spaces of spoil.  Radon was considered as a suitable indicator for this purpose, as it shows good solubility in Non-Aqueous Phase Liquids (NAPL).

Two test series have been conducted in order to determine whether characteristic variations in radon concentration in the course of soil recycling can be observed using a dosimeter.  The reduction in the concentration of mineral oil hydrocarbons was expected to entail the release of radon bonded with the latter, such that the radon concentration would return to its geognostically defined level.  The respective volume of the spoil tips considered was 81 m3, with minimum mineral oil hydrocarbon contamination of 15,000 mg/kg.

Results:

  • The order of magnitude of variations in the radon concentration was significantly smaller than anticipated.  Results obtained also show a dependency upon the ambient temperature and the intensity of exothermic biological reactions in soils.
  • Only ionization chamber measuring apparatus will be suitable for the integrated determination of radon concentration, rather than a dosimeter.

More Project Information

Project title: Monitoring of the status and progress of the biological decontamination of NAPL-contaminated soils by the determination of the radon concentration in the soil air

Project number: 0291213

Project period: 2000 - 2001

Project region: Germany (Saxony)

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Source: German National Library of Science and Technology Hannover (TIB)