1a. Objectives (from AD-416)
To identify appropriate soil amendments and plant species for revitalization of degraded infertile or phytotoxic soils at remediation sites; to collaborate on fact sheets on urban gardening, revitalization and phytoremediation; to collaborate on papers and presentations on ecological revitalization and on technology transfer for soil risk assessment and remediation technologies including phytoremediation.
1b. Approach (from AD-416)
Initial remediation test will examine soil amendments and plant species to achieve revegetation of severely infertile serpentine asbestos mine waste from site in Vermont. Composts, gypsum and NPK fertilizers will be used in combinations to correct Ca and P deficiency by surface amendment of highly sloping barren mine waste site. Promising plant species will be grown on different treatments to identify species which can grow well on amended mine waste and root into the mine waste if calcium and essential nutrients are supplied. Best adapted plant species for the northern Vermont site will be identified. Plants will be analyzed to evaluate remediation of infertility. Will advise on EPA field test of revegetation of site using methods developed in this experiment. On other projects, will collaborate with EPA in preparing fact sheets and manuscripts on soil remediation, urban and brownfield gardening and farming, and phytoremediation.
3. Progress Report
US-EPA and the State of Vermont Department of Environmental Conservation sought to identify methods to reduce the cost of remediation of a site where about 400 acres of crushed serpentine rock remains from mining for asbestos near Eden and Lowell, Vermont. This research group had considerable experience in infertility of serpentine derived soils, and in use of composts and biosolids to achieve revegetation of infertile or metal toxic sites. Although the mine waste contains high levels of nickel, chromium, manganese, iron and cobalt, the pH of the mine waste is 8-10 which keeps these elements from becoming soluble. The key problem was severe infertility. Application of ordinary fertilizers cannot provide adequate P or Ca for plant growth. And the mine waste is essentially devoid of organic matter and soil microbes which are necessary for a stable ecosystem. The estimated cost for remediation of the site using engineering methods was $240 million, using grading to reduce slopes, and cover with 24 inches of topsoil. The plan would have been to purchase a farm and to remove all topsoil to provide the cover soil. A greenhouse pot test with 9 plant species was undertaken with unamended and NPK amended mine waste, 2 inches of compost over the mine waste without and with added gypsum, all compared to a local fertile topsoil. Perennial ryegrass, tall fescue, Kentucky bluegrass and alsike cover which are recommended for soil revegetation in northern Vermont performed very well when compost was applied. Further, especially with the added gypsum, roots of these species grew densely into the mine waste layer because of nutrients leached from the compost layer to the mine waste layer, while roots in the mine waste from the control mine waste treatment were weak, few, and brown. Analysis confirmed the lack of metal toxicity to any species studied. Based on the success of the greenhouse test of mine waste remediation, the cooperators decided to install replicated field tests of the best treatment for establishment of vegetative cover on the mine waste, that is the combination of compost, gypsum, limestone and NPK fertilizer. A two inch layer of the mixed compost plus amendments was applied to different slope areas of the site, and seeded. Plant cover will be evaluated before frost in 2010, and growth and plant composition evaluated during 2011. EPA was also provided assistance with explanation that Pb in soils cannot be practically phytoextracted, but can be inactivated by incorporation of phosphate, composts, or biosolids. Discussion of urban soil and gardening assisted EPA with development of programs regarding urban gardening and agriculture. The cooperating researchers met at BARC to review experimental progress, discuss research plans and maintained regular email communication about experiments in progress. Regular reports of progress were made to US-EPA and the success of the greenhouse test led to the cooperative installation of a field demonstration test in Vermont.