Evaluation of Bahiagrass (Paspalum notatum) as a Vegetative Cover for a Landfill Containing Coal Combustion Waste

Abstract

A vegetative cover is a remedial technique utilized on landfills and waste sites for soil stabilization and for the physical and/or chemical immobilization of contaminants. Many herbaceous plants, primarily grasses, exhibit rapid growth, are moderately resistance to environmental stress, and are therefore often used as cover crops in environmental restoration and remediation projects. Use of bahiagrass (Paspalum notatum) was examined as a potential cover species and phytostabilizer on an unlined landfill (488-D Ash Basin, 488-DAB) containing approximately one million Mg of coal combustion wastes (CCWs) at the U.S. Department of Energy's Savannah River Site (SRS) in South Carolina. Use of soil amendments and treatments to relieve physical limitations at the site (compaction) and promote vegetation success were implemented and assessed. The influence of these treatments on metal uptake by bahiagrass was also evaluated. Results indicated that the survival of bahiagrass growing in plots treated with a surface amendment (15 cm layer of material applied over the CCWs) was the highest in those containing a topsoil cover and followed the order: topsoil > biosolid > ash > apatite > control. Ripping of the landfill prior to planting also resulted in increased survival for the bahiagrass. Significant differences with respect to survival and metal uptake were not observed in plots that were inoculated with vesicular-arbuscular mycorrhizae (VAM) over those not inoculated. However, significant differences (p < 0.05) were observed in plant tissue concentrations of Al, Cr, Fe, Ni, and Zn in plots treated with ash over those of the topsoil and biosolid treatments. Results indicated that the use of soil amendments and subsurface (physical) treatments were essential for plant survival and that periodic monitoring of plant species should be continued to ensure that metal toxicity and secondary contaminant problems do not arise with time.