Activated Biochar-Amended Phytoextraction of Selenium in Contaminated Soil under Cold Climate in Northern Québec (Canada)

Abstract

Combining phytoextraction and biochar amendment was suggested as an alternative for selenium (Se) bioremediation in contaminated soils. The current study aimed to test the performance of activated biochar as an amendment for the phytoextraction of selenium-contaminated soil by Phleum sp. Results showed that Se immobilization in soil was enhanced by the addition of activated biochar owing to its improved physicochemical structure compared to pristine biochar. In parallel, activated biochar contributed to improving soil fertility by increasing pH and organic matter. The bioaccumulation factor (BAF) of Se in the absence of activated biochar and biochar amendment was 8.7, which suggests the suitability of the Phleum plant species as a Se secondary accumulator species to be further used in a Nordic context. Se plant uptake was positively correlated to Se level in soil, pH, redox potential, organic matter, cations (Ca, Mg, Na, K), metals (Al, Cr, Fe, Mn, Co, Pb) and anions (Cl, SO4). However, Se bioavailability for plant uptake was reduced due to Se immobilization in soil by activated biochar. Thus, activated biochar addition played an important role to support Se levels reduction in contaminated soil and consequently hinder phytoextraction performance by Phleum species. This combination of activated biochar and Phleum Se-accumulator plant was validated as an efficient solution for Se remediation in contaminated soil which could be applied at large scale under cold climates.

Keywords

• selenium
• activated biochar
• phytoextraction
• metals
• contaminated soil