ENVIRONMENTAL CONCERNS REFLECTED IN EMISSIONS FROM COAL AND OIL FIRED UTILITY BOILERS BASED ON TRACE ELEMENT SOLUBILITY PERSPECTIVES

The U.S. EPA has been conducting studies to update source profiles from coal and oil fired utility boilers. The emissions test locations included a coal-fired utility boiler (CFUB) that typically uses low sulfur (<0.7%) Eastern bituminous coal as a fuel source, whereas the oil-fired utility boiler (OFUB) uses number 6 residual oil containing 2.4 % sulfur. From both facilities co-located sets of fine fraction (<2.5 mm mass median aerodynamic diameter) particulate matter samples were acquired over a period of several days using a dilution sampler system (DSS) from stack sampling ports at a location of approximately 40 meters above the ground surface. The DSS is designed to dilute stack emissions with clean ambient air (1:35), and then allows sufficient residence time at near-ambient temperature and pressure conditions to promote condensation and coagulation of particulate matter. The PM_2.5 total metal concentrations were determined using energy dispersive x-ray fluorescence (ED-XRF). Subsequently the results from leaching experiments, designed to yield water and dilute acid extractable metal concentrations, were quantified using high resolution inductively coupled plasma mass spectrometry (HR-ICPMS). In general, the total amount of metals emitted from CFUB was greater than that emitted from the OFUB, but the water soluble fraction of the metals from the OFUB was higher than from the CFUB. In combination, these total concentration as well as solubility based trace element profiles will provide new insights from source apportionment, ecosystem impact and human health perspectives.