Metals Soil Pollution and Vegetative Remediation

Principal Investigators
J.L. Schnoor, L.A. Licht, M.A. St. Clair, and C. Just, University of Iowa; and L.E. Erickson, Kansas State University

Abstract

Goal: The goal of the research is to determine feasibility and efficacy of vegetative remediation at a variety of sites with heavy metals soil pollution.

Rationale: Mine tailings and metals pollution of soils is a major problem globally, and it has been identified as a primary research priority area of the Great Plains/Rocky Mountain Hazardous Substance Research Center. The New York Times reported recently that mine tailings wastes account for almost half of all hazardous wastes worldwide. Risk assessments at Superfund sites often reveal that exposure to wind-blown dust by inhalation and ingestion of soil by ch ildren is the greatest risk to human health.

Approach: The proposed research is a comparative study at two sites (Dearing, Kansas, and Whitewood Creek, South Dakota) with greatly different problems, so the scope of the research is to expand the applications to determine more broadly the potential of this innovative approach. In this research the investigators will attempt to establish vegetation at these sites where it has not already been accomplished and to monitor movement of metals in the soil profile as a result of the remediation effort. The research will supplement and continue ongoing research of investigators at Whitewood Creek.

Status: This project has utilized an abandoned gold mining area near Whitewood Creek, South Dakota, for its investigation. Poplar trees were planted in May 1993, but survival has been compromised by frosts, hail damage, drought, deer browse, and apparent toxicity. Nevertheless, sufficient data have been collected to determine that poplar trees can survive in this relatively harsh environment and that the levels of arsenic and cadmium in leaf tissue are not of concern. In June 1995, there were approximately 150 poplar trees still living from a total of 3,000 that were planted in 1993. The surviving trees were sampled in order to understand long-term uptake and translocation of metals. Most of the poplar trees which grew well were concentrated in a specific area, and their heights were around 3.5 to 4.5 feet. The total number of well-developed poplar trees was approximately 80. The other poplar trees, which grew poorly, were scattered throughout portions of the site, and their heights varied from six inches to two feet. The poorly-developed poplar trees survived with native plants at the site. Fresh leaves and stems were sampled from poplar trees at eight different sites. Dead leaves and stems were collected from the ground where fresh leaves and stems were sampled. Surface soil was also collected from within a one foot radius around each sampled poplar tree. One whole tree was extracted, including roots. Soil samples at depths of 3, 9, 18, and 20 inches were collected from this same area. These samples will be analyzed for arsenic, cadmium, zinc, and lead. This project is in its third year.

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

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