Project Abstract

Vegetative Interceptor Zones for Containment of Heavy Metal Pollutants

Principal Investigators

Barbara A.D. Hetrick
University of Northern Iowa
E-mail: Barbara.Hetrick@uni.edu

G.M. Pierzynski
University of Northern Iowa
gmp@ksu.edu

Larry E. Erickson
Kansas State University
E-mail: lerick@ksu.edu

R.S. Govindaraju
Kansas State University

D.W. Sweeney
Kansas State University

Goals

This research has two purposes. First, the efficacy of different plant and microbial regimes in reducing surface water contamination from revegetated plots will be assessed. To determine the ability of various vegetation/microbial regimes to act as buffer strips, after the first year of the project the design of the experiment will be altered. Half of the plots will remain as non-interceptor strips, while half will receive surface runoff from contaminated tailings uphill from the plots. In this way the ability of the various vegetation strips to limit heavy metal-contaminated runoff can be quantified.

Rationale

In southeastern Kansas where heavy metals were mined until the middle of this century, the presence of large piles of gravel tailings with extremely high levels of cadmium, lead, and zinc pose a serious environmental and health risk which led the U.S. Environmental Protection Agency to designate this area as a Region VII Superfund Site in 1985. In areas not designated as Superfund sites, a need also exists for development of economic strategies for containment of heavy metal contamination. While vegetation interceptor strips have been used extensively in agricultural settings to reduce surface water contamination by agricultural herbicides and pesticides, the ability of vegetation buffer strips to limit spread of heavy metal contamination in surface water has not been studied, but could represent an economical alternative with broad application to mine spoils and areas of acid mine drainage as well.

Approach

Revegetation of Superfund and non-Superfund areas will be undertaken to stabilize the sites and reduce wind and water erosion from the tailings. Previous research by these investigators and that of the Bureau of Mines has suggested that certain soil microorganisms, the mycorrhizal fungi, contribute significantly to and may be mandatory for survival and establishment of vegetation on mine spoils. Both the ability of various vegetation regimes to limit surface water erosion and spread of heavy metal contamination, and the ability of these vegetation regimes to act as interceptor strips for contamination uphill from the vegetation strips will be studied in this project.

Status

Although investigators experienced significant difficulties collecting water samples due to flooding of the collection basins, they were able to obtain 21 samples, which were analyzed for sediment concentrations and total and soluble metal concentrations. A rainfall simulator was constructed for collecting water samples with accurate volume estimations from field plots. It was installed at a test site in Kansas and yielded useful data. Soil samples collected during the fall of 1995, at the initiation of the experiment, were analyzed for total metal concentrations. These concentrations were higher than expected for chat material. Fall 1995 soil samples were also analyzed for KC1-extractable ammonium and nitrate concentrations and for soil pH. Soil samples were again collected in the spring of 1996 and analyzed for extractable ammonium, nitrate, phosphorus, potassium, and soil pH. Soil samples gathered at this time were analyzed with the sequential extractable scheme of Tessier et al. (1979). Plant tissue samples were collected in May 1997 and analyzed for cadmium, lead, and zinc. There were no treatment effects on tissue composition. Root samples were also collected in April 1997 to assess the extent of mycorrhizal colonization, and mycorrhizae have been characterized. Techniques for evaluating the usefulness of commercially available mycorrhizal fungi designed for environmental restoration are being developed. Evaluation of vegetation as a means of slowing the migration of contaminated sediments has been completed. Work on modeling has included a review manuscript, which was completed and submitted for publication. Work is also in progress to develop models applicable to the experimental sites, as well as larger field sites. Future plans include increasing output of water from the rain simulator to collect more data from all test plots. This project is in its third year.

Clients/Users

This research will interest those in the mining industry, regulatory community, U.S. Environmental Protection Agency, and U.S. Department of Defense.

Keywords

heavy metals, interceptor zones, mycorrhizal fungi, Superfund, vegetation.