Soil trace element changes during a phytoremediation trial with willows in southern Québec, Canada

ABSTRACT

This study determined the changes in trace elements (TE) (As, Cd, Cu, Ni, Pb, Zn) chemistry in the soils of a willow (“Fish Creek” – Salix purpurea, SV1 – Salix x dasyclados and SX67 – Salix miyabeana) plantation growing under a cold climate during a three-year trial. The soil HNO₃-extractable and H₂O-soluble TE concentrations and pools significantly decreased under most cultivars (Fish, SX67). Yet, TE changes showed inconsistent patterns and localized soil TE increases (Ni, Pb) were measured. Temporal changes in soil TE were also detected in control plots and sometimes exceeded changes in planted plots. Discrepancies existed between the amount of soil TE change and the amount of TE uptake by willows, except for Cd and Zn. Phytoremediation with willows could reduce soil Cd and Zn within a decadal timeframe indicating that they can be remediated by willows in moderately contaminated soils. However, the time needed to reduce soil As, Cu, Ni and Pb was too long to be efficient. We submit that soil leaching contributed to the TE decrease in controls and the TE discrepancies, and that the plantation could have secondary effects such as the accelerated leaching of soil TE.

KEYWORDS:

• phytoremediation
• trace elements
• willows
• field trial
• soil leaching

Acknowledgments

The contribution of Julien Arsenault, Simon Constantineau, Joanie Labonté, Julie Labonté, Catherine Mercier and Audrey Veillette to field and laboratory work is acknowledged by the authors. Joanie Labonté realized the soil maps. The authors thank DRDC for access to their landfill site.

Funding

The authors acknowledge funding for this work by the GenoRem Project, which is primarily financed by Genome Canada and Genome Quebec, and by a Discovery grant from the Natural Sciences and Engineering Research Council of Canada (NSERC) to FC.