Arch. Environ. Contam. Toxicol. 31, 166-169 (1996) ARCHIVES OF: Environmental Contamination a n d Toxicology © 1996 Springer-Verlag New York Inc. Differential Effects of Weathered Coal Fly Ash and Fly Ash Leaehate on the Maize Genome 1 L. M. McMurphy, D. E Biradar, C. Taets, A. L. Rayburn Department of Crop Sciences, University of Illinois at Urbana-Champaign, 320 Edward R. Madigan Laboratory, 1201 W. Gregory Drive, Urbana, Illinois 61801, USA Received: 1 November 1995/Revised: 28 February 1996 Abstract. Land application of coal fly ash is currently under consideration as a means of reducing the amount of industrial waste that must be landfilled. It has previously been reported that alterations occur in the maize genome when plants are grown in soil mixed with fly ash. This study was conducted to determine whether weathering coal fly ash by leaching it with water prior to mixing it with soil reduces its genotoxic effects. Fly ash leachate was produced by two leaching methods, a "one-day" and a "seven-day" method. Maize seedlings were treated with the two types of leachate and with one of the weathered fly ashes produced from the leaching experiments. Flow cytometry was used to determine whether nuclear alter- ations occurred in the seedlings as a result of treatment. Fly ash that had been weathered by leaching for one week did not cause changes in the mean DNA (deoxyribonuclei acid) amount (except for an increase in coefficient of variation--CV), plant height, or cell cycle. The leachate produced from this weather- ing process, however, caused changes in all these parameters. Leachate produced from a 24-h weathering process did not affect mean DNA amount, but did cause small changes in CV, plant height, and cell cycle. Weathering fly ash by leaching before applying it to the soil appears to reduce its potential hazard to the ecosystem. The leachate resulting from the weath- ering process is toxic to plants. Electric utilities generated approximately 80 million tonnes of coal ash in 1990 (Rehage and Holcombe 1990). Of this, approximately 62% was fly ash (Weinstein et aI. 1993). Thus, This research was supported by the Illinois Department of Energy and Natural Resources through the Hazardous Waste Research and Information Center, Champaign, Illinois (HWRIC #92-094) Correspondence to: A. L. Rayburn nearly 50 million tonnes of coal fly ash must be disposed of each year. Application of fly ash to agricultural land is currently under consideration as a means of reducing the reliance on landfilling (Adriano etal. 1980). Several studies have indicated beneficial effects of fly ash amendments on plant growth and yield (Adams et al. 1972; Fail and Wochok 1977; Elseewi et al. 1980; Thicke 1988; Keefer 1993). Although fly ash may supply some plant nutrients, many elements are in high concen- trations that may be harmful to plants and/or animals. Of particu- lar concern are metals and metalloids such as As, Ba, Cd, Cr, Mn, Mo, Ni, Pb, Sb, Se, Ti, V, and Zn that may cause genetic damage in addition to acute toxicity in a variety of organisms (Suloway et aI. 1983; Harte et al. 1991). McMurphy and Rayburn (1993) reported that alterations in the genome occurred when maize (Zea mays L.) seedlings were grown in soil mixed with acidic fly ash. Significant genomic alterations occurred even at agronomically acceptable concentrations of fly ash (Martens and Beahm 1978) that did not stunt seedling growth. The fly ash utilized for that study, however, had not been exposed to any weathering processes. Weathered fly ash may have fewer effects on the genome, because many of the harmful elements have been leached out. Coal fly ash leachate often contains high concentrations of A1, B, Ca, Cd, F, Fe, Mn, Mo, Pb, Sb, and Zn (Griffin et al. 1980). Leachate has been demonstrated to be toxic to a variety of aquatic organisms (Birge 1978; Cumbie and Van Horn 1978; Griffin et al. 1980; Suloway et al. 1983). Removal of these elements through leaching may leave a less detrimental weath- ered product. Martens and Beahm (1978) reported that when high rates of weathered fly ash are applied to land, uniform crop growth often occurs in the season following the application. But when unweathered fly ash is applied, uniform plant growth does not occur until approximately one year later. The purpose of the present work was to monitor the effects of weathered fly ash and fly ash leachate on the maize genome. The results should aid in assessing the safety of land applica- tion of weathered coal fly ash and in determining the ecological risk imposed by leachate generated through the weathering process.