Abstract
A surface flow wetland was constructed in the Burnside Industrial Park, Dartmouth, Nova Scotia, to treat stormwater runoff from the surrounding watersheds which are comprised primarily of commercial properties and two former landfills. The objectives of this study were: (a) to compare the uptake of iron by red maple, white birch and red spruce trees growing under flooded soil conditions in the constructed wetland and well drained soil conditions in a nearby reference site, (b) to evaluate the seasonal variability of iron in these trees and (c) to determine the distribution of iron in different compartments of these trees (leaves, twigs, branches, trunk wood, trunk bark and roots). The average iron concentrations in the aboveground compartments of red maple, white birch and red spruce trees were within the range of iron concentrations reported in the literature for these trees. Red maple, white birch and red spruce trees in the constructed wetland had significantly greater iron concentrations in their roots than the same species in the reference site. The average iron concentrations in the leaves of red maple trees in the constructed wetland and the reference site displayed an increasing trend towards the end of the growing season while the average iron concentrations in the twigs of red maple and white birch trees in the constructed wetland and the reference site displayed maximum concentrations at the beginning of the growing season. Red maple, white birch and red spruce trees in the constructed wetland retained a major portion of their overall iron concentration in their root systems.
Highlights
Heavy metals are elements that have the ability to be molded or shaped, conduct heat and electricity and form stable cations
Iron was present in higher concentrations in the trunk bark of species compared to the trunk wood
The average iron concentrations in the aboveground compartments of red maple, white birch and red spruce trees were within the range of iron concentrations reported in the literature for these trees regardless of the sampling location
Summary
Heavy metals are elements that have the ability to be molded or shaped, conduct heat and electricity and form stable cations. Current remediation methods for heavy metal contaminated environments are often expensive and physically invasive[7]. Physical approaches isolate contaminants from the surrounding environment using capping systems and in situ vertical barriers. These technologies do not remove the contaminants from the soil matrix. Wastewater remediation relies on the addition of chemical agents to the water and physical settling of metal contaminated sludge, which poses the problem of sludge disposal. Within the last fifteen years, efforts have been directed towards finding biological strategies for remediation of metal contaminated environments that are less expensive and less invasive.
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