AbstractsBiology & Animal Science

The revegetation (phytostabilization) of gold mine residues at Val d'Or, QC using Frankla-Inoculated alders

by Katrina Callender




Institution: McGill University
Department: Department of Natural Resource Sciences
Degree: MS
Year: 2015
Keywords: Biology - Microbiology
Record ID: 2062637
Full text PDF: http://digitool.library.mcgill.ca/thesisfile130385.pdf


Abstract

Canada has over 800 active mines that generate more than half a million tons of waste annually. Abandoned unreclaimed mines and waste typically remain unvegetated for tens to hundreds of years during which time they constitute a major eyesore to adjacent communities and pose further risks to their surroundings as contaminants are continuously spread via aeolian and water erosion. Phytoremediation has gained popularity as an efficient, cost-effective alternative to ex-situ techniques as it also restores aesthetic value, important for reclaiming large expanses of contaminated or degraded land. In this study, consisting of both greenhouse and field trials, the symbiotic associations of the pioneer actinorhizal tree and shrub species, alders, with N2-fixing actinomycetes of the genus Frankia and ectomycorrhizal (ECM) fungi were exploited to revegetate, i.e. phytostabilize, waste rock from an active gold mine in Val d'Or, Quebec. We assessed the performance of Frankia-inoculated alders in gold mine residues from Val d'Or, Quebec and investigated effects on microbial community dynamics using a metagenomic approach. Alders that are native to Canada were able to establish on nutrient-poor, moderately alkaline gold mine waste rock from Val d'Or, Quebec, and the use of amendments, including fertilizer, had little or negative impact on alder survival and growth. Soil quality improved as soil pH decreased to 7.5 and after 2 years, total extractable metal concentrations for aluminum, manganese, sodium, copper, etc., decreased up to 2-fold to within Canadian and Quebec regulatory requirements. Microbial enumeration and mineralization assays of C-14 labelled acetate demonstrated increases in soil bacterial density and activity and rhizosphere soils contained up to 2 orders of magnitude more bacterial cells per gram than bulk soils. Metagenomic and high-throughput sequencing of 16S rRNA genes (bacteria) and the ITS region (fungi) were performed using the Ion Torrent PGM, revealing bacterial-dominated (≥ 93.7% sequences) soil microbial communities. Treatment specific changes in microbial diversity and community composition were observed as plants established, including an increase in the abundance of the bacterial class Alphaproteobacteria complemented by a decrease in Betaproteobacteria, suggesting that Alphaproteobacteria may be a useful indicator species. Overall, alder revegetation positively impacted soil physico-chemical properties in addition to soil microbial community composition, diversity and activity demonstrating their successful establishment and potential to positively improve soil structure and quality. Genomics techniques can be applied to further investigate interactions of alders with other phytoremediating plants, fungi and bacteria and develop more efficient phytoremediation techniques. Le Canada compte plus de 800 mines en exploitation générant environ un demi million de tonnes de déchets par an. Les mines abandonnées ainsi que leurs déchets restent généralement sans végétation pendant des dizaines, voir des…