Differential effects of weathered coal fly ash and fly ash leachate on the maize genome

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 alterations 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 weathering 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 weathering process is toxic to plants.