British Columbia Mine Reclamation Symposium

Leonardite and biochar for mine impacted water and soils Stewart, K. J.; Janin, A.


Immobilization of metals using soil amendment processes is increasingly being considered as an effective and low cost remediation alternative in the mining industry. Both leonardite, a carbon-rich material rich in humic acids and biochar, an organic material that has undergone pyrolysis, have shown to adsorb heavy metals, such as Cd and Zn and promote plant growth. We examined the potential to use leonardite and biochar for metal sequestration in mining impacted water and soils, by determining their capacity to adsorb metals in water, sequester metals in tailings and promote plant growth. Biochar removed up to 95% Cd and 90% Zn from synthetic water and resulted in a 74% reduction of Cd and 18% of Zn leached from columns containing tailings. Whereas, leonardite only adsorbed 38% Cd and 29% Zn from synthetic water and resulted in column leachate with higher concentrations of heavy metals. Leonardite amendments caused decreases in pH and mobilization of metals from tailings may be due to acidification. Above and belowground growth of 2 different northern native herb species (Lupinus arcticus and Hedysarum alpinum) in amended tailings were examined. Amendments had little influence on growth with only the leonardite and lime treatment showing increased belowground biomass. This initial trial demonstrates that both amendments show potential for on-going management of contaminated waters and tailings, however, additional liming agents are likely necessary with leonardite.

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