Citation:
תקציר:
The recently developed Diffusion Gradient in Thin-films (DGT) technique is based on a simple device that accumulates metals in situ, over time in a Na resin gel. Metal ions diffuse through a hydrogel membrane and are rapidly bound by the resin. The many advantages associated with the DGT technique (simplicity, in situ technique, low detection limits, and ability to measure many metals) have lead to its rapid application in aquatic environments. Caveats have been recognized with the DGT technique when it is used in aquatic environments. These include: the ability of strongly complexed organic-metal molecules to diffuse through the hydrogel and become complexed by the resin gel, and in freshwater lakes with a low concentration of cations ($Σ$ [cations] $łeq$ 2 $\times$ 10 -4 M), it is hypothesized that the diffusion coefficient of metal ions entering the DGT device increases. Both of these caveats overestimate the concentrations of labile inorganic metals in the deployment solution. The hypothesis that deploying DGT devices equipped with two different hydrogel formulations (``open'' and ``tight'') will provide reasonable measurements of DGT-labile ``organic'' and ``inorganic'' concentrations of Mn, Cd and Pb was tested in the field. DGT devices were deployed in three lakes (Lake Tantare, Lake 8t. Joseph and Lake Memphremagog). To compare the responses of the DGT devices with the total dissolved metal concentration (