Effects of high rates of coal fly ash on soil, turfgrass, and groundwater quality

A field study (1993-1996) assessed the effects of applying unusually high rates of coal fly ash as a soil additive for the turf culture of centipedegrass (Eremochloa ophiroides). In addition, the quality of the soil and the underlying groundwater was evaluated. A Latin Square plot design was employed to include 0 (control, no ash applied), 280, 560, and 1120 Mg ha^-1 (mega gram ha^-1, i.e., tonne ha^-1) application rates of unweathered precipitator fly ash. The once applied fly ash was rototilled and allowed to weather for 8 months before seeding. Ash application significantly increased the concentrations in plant tissue of B, Mo, As, Be, Se, and Ba while also significantly reducing the concentrations of Mg, Mn, and Zn. The other elements measured (i.e., N, K, Ca, Cu, Fe, Ag, Cd, Cr, Hg, Ni, Pb, Sb, Tl, Na, and Al) were not affected. Of these elements Mg, Cu, and Mo concentrations in plant tissue increased with time while B and Se decreased temporally. The diminution of B and Na appears to be related to the leaching of soluble salts from ash-treated soils. Of all the elements measured, only Mn produced significant correlation (p = 0.0001) between the tissue and soil extractable concentrations. Ash treatment elevated the soil pH to as high as 6.45 with the enhanced effect occurring primarily in the 0-15 cm depth. Soil salinity increased with the application rate with the largest increases occurring in the initial year of application. However, by the second year, most of the soluble salts had already leached from the treatment zone into deeper depths, and by the fourth year, these salts had completely disappeared from the profile. The chemical composition of the underlying groundwater was not adversely impacted by the ash application. Plant tissue and groundwater data however, indicate that much higher rates of fly ash can be used on this type of land use where the plant species is tolerant of soil salinity and does not appear to bioaccumulate potentially toxic trace elements.