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| Titel |
Enhanced in situ Biodegradation of Perchlorate in the Vadose Zone |
| VerfasserIn |
Idan Katz, Zeev Ronen, Eilon Adar, Ofer Dahan |
| Konferenz |
EGU General Assembly 2011
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 13 (2011) |
| Datensatznummer |
250055046
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| Zusammenfassung |
| Perchlorate is an environmental contaminant that is mostly manufactured as ammonium perchlorate in the military industry. Natural attenuation and biodegradation of perchlorate in the vadose zone is usually limited due to the absence of carbon and energy sources as well as moister that promotes anaerobic reducing conditions. Yet, previous studies showed that under favorable physical and chemical conditions local bacteria are capable to degrade the perchlorate contamination. The required conditions include 1) high sediment water content 2) negative redox potential and 3) available carbon source as both electron donor and carbon source. Therefore, a study on enhanced biodegradation of perchlorate in the deep vadose zone was conducted through pilot scale experiment which aim to achieve favorable degradation conditions.
Using a drip irrigation system, infiltration carbon enriched solution ( as ethanol) from the top soil will percolate through the unsaturated zone. However, water flow and solute transport in the unsaturated zone is highly unstable and sensitive to pedologic and hydraulic conditions, and to the soil-microbial environment. As a result, natural field heterogeneity may lead to uncertainties with regards to the capability of achieving the desired degrading conditions through enhanced percolation from land surface. In order to cope with this problem, we used a vadose zone monitoring system (VMS). The system is designed for continuous measurement of the vadose zone water content profiles and allows frequent sampling of the sediment pore water. By using the VMS we can monitor the direct impact of the percolating water on the actual hydraulic and chemical conditions. And though a combination of real time monitoring and controlled irrigation from the top soil, we’ll try to achieve optimal degrading conditions at site.
Preliminary conditions at the site where evaluated. The results indicated that the vadose zone pore water contains high concentrations of contaminates, with maximum chloride and perchlorate concentrations of 22000 and 23000 mg/L respectively. After the evaluation of the initial conditions, we started to apply wetting pulses with a carbon sources to the soil. Apparently, in the upper section of the vadose zone there was a decrease in perchlorate concentrations and rise in the chloride concentration. This phenomenon can indicate that the biodegradation process is taking place. However, DOC concentrations in the percolating water declined sharply with depth, this is due to microbial consumption of the carbon source in the upper layers. These preliminary results indicate that application of carbon source from land surface to deep sections of the vadose zone is limited and impose a significant obstacle for deep soil remediation. The future objective of this study is to optimize the wetting sequence to allow improved transport conditions for carbon source to deeper sections of the vadose zone. By that to enhance biodegradation in deep vedose zone |
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