Isotope fractionation of volatile organic contaminants in porous media under unsaturated conditions: Mechanisms and applications
| Responsable du projet | Daniel Hunkeler |
| Collaborateur | Simon Jeannottat |
| Résumé |
Organic compounds such as chlorinated compounds and petroleum
hydrocarbons are among the most common groundwater contaminants.
For risk assessment and in order to plan effective remediation
methods, it is important to know from where these contaminants
originate and to what extent they are removed by naturally
occurring biodegradation. A recently proposed approach to gain
insight into the origin and fate of organic compounds in
groundwater is the use of stable isotope analysis. Organic
contaminants from different sources (e.g. spills caused by
different companies) often have a different isotopic composition.
In other words, the naturally occurring stable isotopes (e.g. 13C
and 12C) are present in different proportions. Furthermore, during
biodegradation frequently the heavy isotopes become more and more
abundant in the contaminant because molecules with light isotope
are degraded faster by bacteria. This isotope enrichment trend
makes it possible to identify and quantify biodegradation. The
stable isotope method has so far mainly been investigated and
applied in groundwater studies. In contrast little information is
available so far on its use in the unsaturated zone between the
water table and the land surface. The main aim of the project is to
investigate whether the stable isotope method can also be used in
unsaturated zone studies to link contaminants detected at the
surface to subsurface sources and to demonstrate biodegradation.
The project focuses on volatile organic compounds because these
compounds diffuse rapidly through the unsaturated zone and hence
can contaminate groundwater or impact air quality in buildings.
Before the isotope method can be applied to solve practical
questions, more knowledge is necessary on how isotope ratios evolve
during transport and degradation of organic compounds under
unsaturated conditions. The effect of these processes on isotope
ratios will be investigated in laboratory column experiments. Such
experiments have the advantage that key experimental parameters can
be controlled exactly and mathematical approaches to quantify the
phenomena tested rigorously. In addition, several field sites will
be equipped with multilevel gas samplers and it will be
investigated whether isotope ratios can be used to link
contaminants to their source and/or to demonstrate
biodegradation. |
| Mots-clés |
Stable isotopes, organic contaminants, unsaturated zone, biodegradation |
| Type de projet | Recherche fondamentale |
| Domaine de recherche | Autres secteurs des sciences de l`environnement |
| Source de financement | FNS - Encouragement de projets (Div. I-III) |
| Etat | Terminé |
| Début de projet | 1-11-2008 |
| Fin du projet | 31-10-2011 |
| Budget alloué | 208'698.00 |
| Autre information |
http://p3.snf.ch/projects-121932# |
| Contact | Daniel Hunkeler |