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2. Aims and objectives
The presence of harmful chlorinated substances in the subsurface is a large threat to our groundwater reserves. Fortunately, nature
has found several ways to destroy these compounds. In the subsurface, both biological and chemical processes may occur that cause
degradation to non-toxic end products. This is called natural attenuation or NA. Some of these NA processes are well-known and
can be demonstrated rather easily. For other processes that can potentially play an important role, it is more difficult to find evidence.
Traditional methods are not suited for demonstrating these processes and their significance in the subsurface is still unknown.
In this project, we investigate the use of a new analytical technique called "compound specific stable isotope analysis (CSIA)" to study
the relevance of the abovementioned NA processes. With CSIA, we can study the properties of single atoms in the contaminant molecules.
Chlorinated solvents consist of carbon and chlorine. By looking into both types of atoms, it is possible to identify and quantify
different NA processes. CSIA for carbon is already applicable for field application, but CSIA for chlorine has been developed very recently
and requires optimization.
The objective of the project is to optimize the use of CSIA for chlorine and to demonstrate the use of combined carbon and chlorine
isotope analysis as a tool for demonstrating natural attenuation of chlorinated solvents.
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3. Research activities
At the institute WAR of the Technical University of Darmstadt in Germany, the method for stable chlorine isotope analysis will be optimized
to make it suitable for application on samples from contaminated groundwater. At the same time, a laboratory study will be performed
at VITO in Belgium, in which the relation between the targeted degradation processes and the isotope analysis results will be
established.
Since the results of the isotope analyses from field sites are difficult to interpret and to explain, an existing computer model suitable for
interpreting carbon isotope data will be extended to make it applicable to chlorine isotopes.
In the next phase, the method will be applied at three field sites contaminated with chlorinated solvents. At the
same time, more conventional methods will be applied to obtain a complete picture on the natural processes. The site data will be interpreted
using the developed computer model.
The results from this project will help us to understand the complex natural processes that determine the fate of this class of harmful
groundwater contaminants.
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4. Dissemination activities
For this project to be meaningful, it is essential that the knowledge and the tools developed become known to the consultants, authorities
and scientists who work on the protection of our groundwater.
This will be achieved by publication in scientific and technical journals, by organizing a symposium and by incorporating the methods
in guidelines.
A first platform presentation on the ENACT project will be given at ConSoil 2008 in Milano (http://www.consoil.de).
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5. Perspectives
Stable carbon isotope analysis is rapidly becoming an accepted tool for studying contaminant processes in the subsurface. We expect
that this ENACT project will be a strong stimulus for application of chlorine isotope analysis and will lead to a better understanding on
NA processes for chlorinated solvents.
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6. Results
The project just past its midterm. The midterm report is under evaluation by the SNOWMAN Call Steering Committee.
As soon as it is approved, first results will be implemented into this page.
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