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Abstract
Industrial processes, such as base metal smelting and refining, often result in the widespread distribution of heavy metals and acid forming compounds into the surrounding environment. The impact of this deposition on the neighboring ecosystems can be devastating, leading, in some cases, to perturbation or loss of ecological viability, which depends primarily on the amount, concentration and type of metal species. In order to restore the productivity of these lands, remediation practices aimed at reducing soil metal concentrations or minimizing their mobility and bioavailability are necessary. The cost associated with conventional (i.e. excavation and disposal) remediation methods can be prohibitively expensive (> $3 million ha-1), and therefore, alternative methods must be examined.
In this research, a variety of macroscopic, microscopic and cutting-edge spectroscopic tools were used to investigate the influence of in-situ chemical treatment (i.e., liming) and soil type (Welland Loam vs. Quarry Muck) on the speciation of nickel (Ni) in soils surrounding an historic Ni refinery in Port Colborne, Ontario Canada. In addition, Ni speciation and compartmentalization were determined in the Kotodesh cultivar of the Ni hyperaccumulator Alyssum murale (Waldst. & Kit.) to ascertain the biochemical mechanism used by A. murale to remove Ni and explore its potential as an alternative remediation method from these soils. In doing so, the development and implementation of novel synchrotron-based microtomographic methods were shown to be very effective at determining the location and concentration of metals within and throughout unaltered A. murale tissues.
Chemical treatment and soil type had a pronounced influence on the type of metal species formed in the refinery-enriched soils. Monitoring the dissolution of Ni from potential soil Ni species by pH 4 HNO3 using a stirred-flow technique, showed that 100% and 79% of NiO and NiS compared to 62% and 57% of the Ni Al-LDH and α-Ni(OH)2 remained after the 8-hr experiment. Making the soils calcareous with the addition of 33-88 Mt ha-1 dolomitic limestone was effective at reducing Ni mobility. In both the unlimed muck and mineral soils, roughly 2% of the total Ni was released throughout the duration of the 8 hour experiment compared to 0.1% for the treated soils.
Conventional sequential extraction methods were ineffective at accurately determining the Ni speciation in both muck and loam untreated field soils as well as a highly enriched forested muck soil.* (Abstract shortened by UMI.)
*This dissertation is a compound document (contains both a paper copy and a CD as part of the dissertation). The CD requires the following system requirements: Windows MediaPlayer or RealPlayer.
