Dissolution behavior of metals from particulate matter emissions*

Abstract

Exposure to air particulate matter (PM) is linked to numerous health effects. In order to improve the understanding of the role of its metallic components, their solubility was examined by using serial short-contact dissolutions totalling 1 h and additional sequential contact periods of 1, 4, and 8 days. The dissolution experiments were performed in solutions containing the main biological electrolytes. ICPMS determinations were used to quantify the dissolved metals. The total compositions were determined after closed vessel microwave digestion. Large variations in the rate and completeness of the dissolutions were observed. Fast and extensive dissolutions within the short-contact time (e.g., Zn, Cd) as well as slow dissolutions persisting during the last contact period (e.g., Ni, Cu, Sb, Pb) were found for smelting emissions. The multi-element determinations also made it possible to identify relationships between dissolution of different metals and define gradual composition changes of residual PM. When comparing with dissolutions performed in de-ionized water, similar major fractions were observed at short-contact time for minor components of smelting or combustion emissions (e.g., V, Ni, Cd), suggesting a preponderance of easily available forms at the surface of the relatively inert particle cores. The use of these time sequential methods may help in (1) modeling metal partitioning in biological media and (2) investigating the causes of adverse effects attributed to air PM. This work was presented in part at the 2006 Winter Conference on Plasma Spectrochemistry, January 8–14, 2006, Tucson, USA.