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Use of Poplar Trees in Remediating Heavy Metal Contaminated Sites

Principal Investigators
Pierzynski, Tracy, Davis, Reddi, Erickson, Schnoor

Abstract

Goals: Research objectives are to investigate suitability of deep-planted poplars as a vegetative remediation strategy all future measurements could be compared. Survival measurements and leaf samples have been taken. As of September 1995, 400 out of the original 576 trees were alive for an overall survival rate of 69.4%. Addition of manure to the trenches significantly increased growth via increases in height and trunk diameter. The data clearly show that tree cultivar and soil amendments can influence survival and growth parameters. Soil samples have been collected from eight different areas and analyzed for lead concentration. Soil lead concentrations will be compared to leaf tissue lead concentrations after those analyses are complete. This project is in its third year.

Rationale: Abandoned sites associated with old heavy metal mining and smelting activities often have a large proportion of their area without vegetative cover. This allows erosional forces to proceed at a maximum rate, and materials with high heavy metal concentrations are dispersed by wind and water. Little research has addressed use of poplar trees in such a situation.

Approach: This study will focus on an abandoned zinc and lead smelter site in southeast Kansas. The investigators propose to begin investigations whose ultimate goal is to immobilize the metals in place. This would be accomplished with grading to 3-5% slope, to encourage runoff without excessive erosion, and the use of rapid growing poplar trees that have a high water demand. This strategy would minimize net percolation through mine spoil material, thus minimizing impact on ground water. Surface erosion would be effectively controlled once the trees are established. A thin soil cover would be employed to establish a perennial grass cover to prevent surface erosion until the trees had become established.

Status: This project has utilized an abandoned zinc/lead smelter site near Dearing, Kansas, for its investigation. Poplar trees were first planted in June 1994 but survival as of September of that same year was only 7%. This was attributed to the late planting date (which was necessary because of extremely wet conditions), a reduction in tree viability due to storage, and droughty conditions following planting. The trees were replanted in March 1995, a more appropriate planting time, in a split-plot design with the main plots being the in-trench treatments with or without manure and the subplots being poplar cultivar. Height and trunk diameter of each tree was measured to serve as a baseline to which all future measurements could be compared. Survival measurements and leaf samples have been taken. As of September 1995, 400 out of the original 576 trees were alive for an overall survival rate of 69.4%. Addition of manure to the trenches significantly increased growth via increases in height and trunk diameter. The data clearly show that tree cultivar and soil amendments can influence survival and growth parameters. Soil samples have been collected from eight different areas and analyzed for lead concentration. Soil lead concentrations will be compared to leaf tissue lead concentrations after those analyses are complete. This project is in its third year.

Clients/Users: This research is of interest to the mining industry and regulatory community.

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