<p>Water-quality in freshwater ecosystems is linked to metal contaminant sequestration and transport by suspended aquatic floc. This doctoral thesis investigates the combined microscale biogeochemical processes as well as macroscale hydrodynamic mechanisms controlling trace metal dynamics of freshwater floc, through comparative assessments of floc versus bottom bed sediment metal(loid) (Ag, As, Co, Cu, Ni and Pb) sequestration/mobilization across aquatic ecosystems ranging in physico-chemistry (e.g. pH, organic carbon, Fe/trace metal concentrations) in the Boreal Forest Region of Ontario and under variable energy-regimes (i.e. calm, windy, prolonged-storm) in a shallow wave-dominated urban beach in Lake Ontario, Canada.</p> <p>The results establish differential biogeochemical controls in suspended floc versus bed sediments influencing the abundance, reactivity and type of Fe minerals affecting trace metal abundance and solid-phase partitioning patterns between these two compartments. Specifically, this work demonstrates a microbial underpinning to floc collection of amorphous Fe oxyhydroxides (FeOOH) controlling floc metal sorption, retention and overall metal concentrations that are significantly greater in suspended floc than bed sediment. In contrast, crystalline Fe oxides (FeOx) dominate sediment metal retention, due to reductive dissolution and/or mineral aging of FeOOH, where sediment solid-solution metal partitioning is more influenced by system physico-chemistry (i.e pH). Further, rapid fluctuations in energy regime influencing re-suspension/settling of floc and sediment (i.e. surficial fine-grained lamina (SFGL) versus underlying consolidated sediments) result in temporal and spatial hydrodynamic-dependent mixing of Fe mineral phases, altering metal abundance and solid-phase metal partitioning in each compartment.</p> <p>Collectively, findings of this innovative integrated thesis work provide new understanding of the physical and biogeochemical controls on Fe cycling/mineral transformations between floc and bed sediments, ultimately affecting trace metal iv behaviour between these compartments and fate in freshwater environments. This insight has important implications for policy development in improving risk management of aquatic systems under varying physico-chemical and hydrodynamic conditions.</p> / Doctor of Philosophy (PhD)
| Identifer | oai:union.ndltd.org:mcmaster.ca/oai:macsphere.mcmaster.ca:11375/13209 |
| Date | 10 1900 |
| Creators | Plach, Janina M. |
| Contributors | Warren, Lesley A, Geography and Earth Sciences |
| Source Sets | McMaster University |
| Detected Language | English |
| Type | dissertation |
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