<p> In this study a combined field and laboratory approach was used to identify the
bio-geochemical processes that control trace metal (Ni, Co, Cr) reactive transport within
natural acid rock drainage (ARD) biofilms, over both diel and seasonal timescales.
Results indicated that metal (Mn, Ni, Co and Cr) scavenging by these biological solids is
stable on a seasonal time frame. Metal scavenging occurs within two key solids, the
organic constituents of the biofilm (Ni, Co) and associated biogenic hydrous Mn
oxyhydroxides (HMO; Ni, Co and Cr), and not in association with Fe-oxyhydroxysulphates
which dominate the mineralogy of the biofilm samples by mass. On a diel
basis, cycling of HMO and associated trace metal dynamics appear to be contingent on
the vertical migration of the biofilm oxic-anoxic boundary, a microbially controlled
process. </p> <p> The reactivity and sorptive capacities of synthetic HMO analogs for Ni were
further examined under well-characterized laboratory conditions. Analysis of the local
chemical environment of Ni sorbed to HMO by synchrotron-based X-ray absorption
spectroscopy was integrated with a bulk geochemical model of the acid-base
characteristics of HMO and a theoretical model of the HMO structure. The synergistic
use of these techniques allowed unique insight into the structural reactivity of HMO for
Ni and is the first study to mechanistically demonstrate why bulk surface complexation
models (SCM) are not accurate for HMO metal uptake. </p> <p> Overall, the results of this thesis highlight the utility of combined field and laboratory investigation to characterize relevant processes for reactive metal transport and underscore the need to: (1) consider microscale microbial-geochemical linkages in geochemical behaviour; (2) use caution when applying results derived from synthetic analogs to interpret natural system behaviour; and (3) examine processes at the appropriate scale e.g. microscale, to evaluate the mechanisms involved in metal reactions
with solids. </p> / Thesis / Doctor of Philosophy (PhD)
| Identifer | oai:union.ndltd.org:mcmaster.ca/oai:macsphere.mcmaster.ca:11375/19516 |
| Date | 04 1900 |
| Creators | Haack, Elizabeth Ann |
| Contributors | Warren, Lesley A., School of Geography and Geology |
| Source Sets | McMaster University |
| Language | English |
| Detected Language | English |
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