Assessment of Metal Attenuation in a Natural Wetland System Impacted by Alkaline Mine Tailings, Cobalt, Ontario, Canada

Abstract

A natural wetland in the Farr Creek drainage basin near Cobalt, Ontario was studied because its floor is covered with alkaline mine tailings that contain elevated levels of metals, including As, Co, Cu, and Zn, due to mining that occurred intermittently from 1904 to the 1980s. Our objectives were to characterize the biogeochemical interactions occurring throughout the wetland and to assess its ability to effectively attenuate the metal contamination. We were not able to conclusively determine if this wetland is a net source or net sink for As, Co, Cu, and Zn; it is not clear whether this wetland has reached its capacity for attenuating these trace elements. Both oxidizing and reducing bacteria were quantified and found to be prevalent throughout the wetland, with similar population densities. It is likely that the presence of localized oxic zones in the root zones of Typha latifolia supported the oxidizing bacteria populations observed. The results indicate the importance of understanding the conditions in systems being used to treat mine drainage, as well as the importance of having a detailed understanding of the metals of concern in the mine waste.

Natural attenuation of arsenic in the wetland system around abandoned mining area

“…5. A remarkable thing is that the most As in the wetland sediment was detected predominantly in residual phases (step 5) accounting for silicate minerals and sulfides (Kelly et al 2007); however, in the case of the paddy soil, the percentage of residual phases was relatively lower than that obtained more reactive fractions. Moreover, As fraction extracted from step 1 to 3 corresponding to relatively liable phases was higher in the paddy soil than in the wetland sediment (about 40 and 20%, respectively).…”

Sustainable rehabilitation of mining waste and acid mine drainage using geochemistry, mine type, mineralogy, texture, ore extraction and climate knowledge

“…There are different gangue and secondary minerals (see Section 5.2.3) including efflorescent salts available in the mining waste and tailings (Appendix Tables 1e5), that can significantly immobilize PTMs by acid neutralization and adsorption mechanism (Alvarez-Valero et al, 2008;Quispe et al, 2013). However, since these tailings contain many PTMs, these can potentially contaminate the receiving environments (Kelly et al, 2007;Rusdinar et al, 2013). Furthermore, the detailed knowledge about ore and gangue mineralogy and their morphology should be considered during remediation of mining wastes (Parbhakar-Fox et al, 2013) (Fig.…”

“…Johnson and Hallberg (2005) identified both Fe and S-oxidizing bacteria such as Thiomonas sp., sulfate-reducing bacteria (SRB) and neutrophilic SRB in their treatment system. The neutralization of AMD, precipitation of ferruginous ochres (amorphous ferric hydroxide) and biogeochemical interactions have caused natural attenuation of heavy metals and sulfate in wetlands and streams connected to mining waste and tailings (Black and Craw, 2001) at Chambishi site in the Copperbelt of Zambia (Sracek et al, 2011), the Lot River near Enguiale's tungsten mine (Courtin-Nomade et al, 2005), As mine in Nishinomaki, Japan (Fukushi et al, 2003), and the Farr Creek drainage basin near Cobalt, Ontario (Kelly et al, 2007).…”

The impacts of century-old, arsenic-rich, mine tailings on multitrophic level biological assemblages in lakes from the Cobalt, Ontario, Canada region

“…Occurring at around the same time as the Klondike goldrush in the Yukon Territory, the discovery at Cobalt has been argued to be more historically important for Canada. This is due to how the mining activities in the Cobalt region continued to influence and solidify Canada's reputation as a mining powerhouse, even after the final mines were shut down in the 1980s (Baldwin & Duke 2005;Kelly et al 2007). Named Ontario's "Most Historic Town" in 2001, and declared a National Historic Site in 2002, Cobalt has been recognized as the birthplace of hard-rock mining in Canada, and the activities which took place in the region helped to pave the way for future exploration, mining, and settlement in both northern Ontario and Québec, as well as globally (Dumaresq 2009).…”

“…Of the work currently available on the impacts of mining in the Cobalt region, much of it has been focused on the conversion of lakes into wetland systems due to the input of arsenic-rich mine tailings, and the subsequent geochemical interactions between changing redox conditions and the mobilization of contaminants (Kelly et al 2007;Beauchemin & Kwong 2006;Kwong et al 2006). One such study by Kwong et al (2006) examined wetlands in both Farr and Mill Creek near Cobalt in order to characterize the composition of mine tailings settled along the bottom of the drainage system, as well as to clarify some of the transformation and mobilization processes involved with arsenic.…”