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Lab-scale thermodesorption tests used to estimate the evolution of available aliphatic hydrocarbons in contaminated soils during pilot-scale remediation experiments

Abstract : According to the European Environmental Agency, petroleum contamination affects more than 300,000 sites in Europe. Remediation treatments are often required to decrease the contaminant concentration to acceptable levels. The determination of the available fraction of a contamination is a major concern for risk assessment and management of contaminated sites. Indeed, the contaminant availability rules the efficiency of remediation treatments and the impact of the contamination on the biota (toxicity). The aim of this study was to use thermodesorption coupled with molecular analysis for the determination of the available fraction of the contamination. It is based on linking the desorption temperature to the binding strength between the contaminant and the soil constituents, i.e. the higher the desorption temperature of a compound, the higher its binding strength with the soil and the lower its availability. The method was tested on samples taken from pilot-scale remediation of petroleum-contaminated sludge from drilling deep extraction wells. This soil/sludge matrix presents 30,000 mg/kg of average total petroleum hydrocarbon content (TPH) with n-C12 – n-C30 as dominant fraction. The matrix was mixed with compost and top soil in different proportions and a biopile treatment was applied according to different modalities: -biodegradation only for 18 months, mechanical mixing every 2 months for aeration, -biodegradation only for 2 to 4 months and vegetation growth (Ray-grass and Alfalfa) afterwards, mixing only occurs every 2 months during the initial biodegradation phase, -undisturbed, non-amended sludge kept in the dark was used as control sample. Soil monitoring is performed every 2 months to compare all treatment conditions with time for global in-situ parameters (pH, biogas production, temperature, moisture content), biological (nematodes, bacteria and fungus qPCR) and chemical (contamination level, soil enrichment) parameters and vegetation features (biomass production, root development, omega 3 content). The first months of monitoring showed a limited degradation of contaminant in comparison to previous feedbacks on similar treatments. To understand this behavior, a focus was made on the contamination including global and molecular (GC-MS and GC-FID analyses) characterizations in addition to thermodesorption analyses. Molecular ratio based on compound degradability (n-C17/pristane, n-C18/phytane, LMW/HMW, alkyl-aromatic/parent compounds…) indicated that the biodegradation reached a more advanced stage in the biopile modalities compared to the control sample. Thermodesorption profiles indicated two distinct behaviors that could correspond to (i) the preferential degradation of the compounds desorbed at lower temperature (available compounds) and (ii) the increase in the content of n-alkanes desorbed at higher temperature that could indicate a binding and a stabilization of these compounds during the treatment. The study is still ongoing and the analyses of the coming samples will be carried out within the next few weeks to evaluate the possible increase of matrix binding effect of TPH with time during the biopile treatment pilot.
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Poster communications
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https://hal.univ-lorraine.fr/hal-03216676
Contributor : Coralie Biache Connect in order to contact the contributor
Submitted on : Tuesday, May 4, 2021 - 11:46:20 AM
Last modification on : Tuesday, May 10, 2022 - 3:38:05 PM

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  • HAL Id : hal-03216676, version 1

Citation

Coralie Biache, Pierre Faure, Catherine Lorgeoux, Anouk Barrere, Sébastien Kaskassian. Lab-scale thermodesorption tests used to estimate the evolution of available aliphatic hydrocarbons in contaminated soils during pilot-scale remediation experiments. Aquaconsoil, May 2019, Anvers, Belgium. ⟨hal-03216676⟩

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