University of Arkansas, Fayetteville Division of Agriculture


Fly ash is a byproduct of the combustion of coal, primarily by coal-fired power plants. Over 97.8 million tonnes of fly ash are produced each year in the United States. Fly ash can contain trace elements in concentrations that can cause health risks. Recent spills have highlighted that fly ash disposal is problematic. The objective of this study was to evaluate the effects of fly-ash type (fresh and weathered) from a local coal-burning power plant and extraction time (2 and 6 h) on dilute-acid extractable concentrations of phosphorus (P), arsenic (As), and selenium (Se). Ash samples were extracted with 0.1 M HCl and shaken for either 2 or 6 h. Extracts were analyzed by inductively coupled argon plasma mass spectrometry. Phosphorus concentrations increased with the longer extraction time, but there was no significant difference between ash type. Arsenic and Se concentrations were greater in fresh ash and decreased with longer extraction time in fresh ash, but no difference between extraction times was observed in weathered ash. It was determined that P concentrations were not related to As and Se concentrations, but were possibly dependent on calcium phosphates because of the high pH of fly ash. The lower As and Se concentration in the fresh ash, 6-h extraction, as compared to the 2-h extraction suggests that a process analogous to environmental weathering occurred during extraction. Research into the behavior and speciation of these insoluble forms will help explain movement and behavior of trace elements in fly ash.