Electronic Thesis and Dissertation Repository

Degree

Doctor of Philosophy

Program

Civil and Environmental Engineering

Supervisor

Dr. Denis O'Carroll

Abstract

This thesis began by verifying that nanoscale zero valent iron (nZVI) synthesis methods could be scaled up and implemented at the field scale in a safe manner. This led to successful demonstration of nZVI injection and mobility under constant head gravity injection into a contaminated utility corridor in Sarnia, Ontario. Where field studies have fallen short in the past was linking the somewhat qualitative field geochemical parameters to other evidence of nZVI transport. Definitive nZVI detection was elusive in previous field studies due to the highly reactive nature of the particles caused by their high surface area. nZVI was detected and characterized in this study using UV/Vis spectrophotometry, Dynamic light scattering, zeta potential, Transmission Electron Microscopy, and energy dispersive x-ray spectroscopy, proving that field mobility was reliably achieved.

The second study provides the first insight into the interactions and reaction that occur on an active field site immediately following nZVI injection. A fine temporal resolution of samples was used to define chlorinated ethene, ethane, and methane (cVOC) degradation among nZVI impacted zones, showing that these zones were distinct from areas that were not affected by nZVI. Building upon previous indirect evidence that nZVI enhances organohalide-respiring microorganisms, this study set out to prove that microbiological communities on sites were enhanced following injection. Quantitative polymerase chain reaction (qPCR) was used to target Dehalococcoides spp. (dhc) and vinyl chloride reductase genes (vcrA). The distinct zones where nZVI treatment was applied subsequently had high abundances of dhc and vcrA. The qPCR methods presented in the second study can act as a template for future field investigation on nZVI.

Finally, the long-term effects of the injection amendments nZVI and Carboxymethyl-cellulose were monitoring on the microbial communities on site. It was hypothesized that the organohalide-respiring species on site would be enriched and cVOC degradation would be sustained due to the polymer amendments that accompany nZVI injection. Over a two year period next-generation pyrosequencing, qPCR, and cVOC degradation were monitored, providing the first ever phylum level microbiological evaluation at a field site undergoing remediation.