Monitoring of trace element in groundwater by DGT
Résumé
DGT passive samplers, are often used for the monitoring of trace elements in inland or marine surface waters. In these contexts, they offer significant advantages over spot sampling by their performance in terms of preconcentration and integration of changes in concentration over time. At the opposite, there is little application of these tools for underground water context. The needs for underground water monitoring are not the same as surface water. However it seems interesting to test the capabilities and limitations of these passive samplers in groundwater. In the proposed study DGT-chelex have been deployed in four campaigns of about 14 days in a piezometer installed on an uncontaminated sites. Spot sampling occurred before and after deployment of samplers and also with and without purging of the piezometer. During one campaign, DGT of varying diffusive gel thickness were used to study the thickness of the diffusive boundary layer in an underground environment (with low water flow) following the method described by Kent W. Et al. (Accuracy Of The DGT-Diffusive Boundary Layer and Effective Sampling Area Considerations, Anal. Chem. (2006), 78, 3780-3787). An estimate of this boundary layer has been done and it shows that in the context of this study (and probably for most of underground water), this effect can not be neglected. Concentrations of ten trace elements (Al, Cr, Mn, Fe, Ni, Co, Cu, Zn, Cd, Pb) were followed on these 4 campaigns and over a 4 months period. The results were interpreted in terms of reproducibility of measures over 4 months and DGT concentrations were compared with spot samples concentrations.
Domaines
Chimie analytique
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