Euradwaste '08 - EU Bookshop - Europa

comprise μ-XRF and μ-XAFS spectroscopy, sequential extraction, U(IV)/U(VI) separation with
234 U/ 238 U ratio determination. Detailed information can be found in [4]. In addition, sorption experiments
have been performed and exchangeable uranium determined by isotope exchange with
233 U, e.g. [9], [13]. μ-XRD and μ-XAFS were applied the first time to natural samples and the
method was further developed within the FUNMIG project.
Real system analyses: This work package comprised the integration of results from both other work
packages and available information from site characterisation. Moreover, analyses of specific environmental
isotopes, in particular � 34 S in dissolved sulphates as well as � 13 C and 14 C in DOC have
been performed. Additional work was carried out on characterisation of DOC and SOC (integration
with RTDC2). DOC was characterised by IR and MALDITOF spectroscopy, whereas extracted
humic substances were characterised using elementary analysis, ash and moisture content, UV-Vis
spectroscopy, FTIR spectroscopy and acidobasic titrations. Details can be found in [5].
3. Results
3.1 Colloids
As described above part of the work was dedicated to method-development and qualification. During
the project a new mobile geomonitoring system including a system for the laser-induced breakdown
detection of colloids (LIBD) was developed [3]. It was successfully applied to the detection
of colloids in natural groundwater samples from Ruprechtov site and other sites in Sweden.
It could be shown that colloid concentrations down to μg/l are detected with the special sampling
technique. By comparison with in-situ probe measurements in several boreholes it was also demonstrated
that reducing conditions with minimal access of atmosphere oxygen are maintained. In-situ
experiments in granite demonstrated that colloid generating processes like redox changes (e.g. in
EDZ) and/or mechanical erosion can increase the natural colloid background by up to several orders
of magnitude.
The LIBD determined natural background colloid concentrations found at Ruprechtov are compared
with data of studies performed in Äspö (Sweden) and Grimsel (Switzerland). A comprehensive representation
of colloid concentrations in different water samples as determined by LIBD as a function
of the respective ionic strength is given in Figure 2 [3]. Increasing ionic strength usually forces
colloid aggregation which is reflected in lower colloid concentration in the respective groundwater.
In the Ruprechtov groundwater samples the ionic strength varies in the range of 2·10 -3 to 1.1·10 -2
mol/l without any significant influence on the measured colloid concentration. The broad bandwidth
of detected colloid concentrations in groundwater of ionic strength