Seminar: A modified Chelex resin DGT

A modified Chelex resin DGT combines the advantages of both Micro-Chelex and Classical Chelex resin DGTs for Fe and Mn mapping in sediments

Chunyang Zhou

In a previous work, classic chelex (CC) DGT and the microchelex (MIC) DGT (suspended particulate reagent-iminodiacetate) that were deployed in anoxic sediment porewaters to assess Fe, Mn, Cd, Co, Cu and Ni mobilization, gave quite different results especially for Fe and Mn. In this study ground water samples were spiked with the afore mentioned metals. While the difference in Cd, Co, Cu, Ni and Fe concentrations between both DGT pistons was small, it was not the case for Mn. Therefore, experiments to validate the capacity of both resins for Fe and Mn as well as two binding competition experiments were carried out in oxygen free conditions to mimic an anoxic sediment environment.

Fe and Mn binding capacities on MIC DGT are around 2-4 µg, which means that they are far below those on CC DGT, while competition with stronger binding metals such as Cu and Cd still lowered the adsorption capacity for Fe and Mn. A modified chelex (MOC) resin was produced and validated in DGT samplers. The capacity of the ground resin gel included in a DGT was above 90 µg which is over 20 times higher than the MIC one. In addition, the bead size of the MOC resin is small enough to allow high resolution LA-ICPMS mapping of Fe and Mn in sediment pore waters.