An investigation of trace metal speciation of natural waters using a novel in situ sampling device
LE3 .A278 2009
Bachelor of Science
An improved in situ passive sampling device was developed for studying trace metal speciation in the aquatic environment. Unique features of this research were i) the use of a range of diffusive layer thicknesses to study lability of trace metal species (Mn, Co, Ni, Cu, Zn, Cd, and Pb) combined with ii) kinetic speciation by a competing ligand exchange method (CLEM) using Chelex 100, the same chelating resin that is used in the in situ sampling devices, thereby allowing effects of the competing ligand to be separated from the effects introduced by the in situ sampling devices. In situ sampling techniques, such as Diffusive Gradients in Thin films (DGT), provide a means of assessing the labile metal concentration in natural waters, allowing for a more accurate assessment of metal bioavailability. Several problems inherent to the design of DGTs have prompted the development of novel in situ sampling devices; the focus of this research is to test a newly developed in situ sampler prototype and compare its effectiveness to DGT and kinetic speciation (CLEM) results. The results obtained by DGT, EmporeTM devices, and CLEM were found to be operationally defined by i) the experimental timescale, ii) the binding phase, and iii) the metal-to-ligand ratio. CLEM was able to accurately predict the relative lability of metals in various metal-to-ligand ratios; however, the lack of a preconcentration step limits its utility to polluted waters. By contrast, preconcentration of metals in the receiving phase during deployment of the in situ passive sampling devices allowed metals in ultra-trace level waters to be measured.
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