Bioaccessibility of Heavy Metals from a Primary Lead Smelter
Emissions arising from primary lead smelting contain a range of contaminants which are known to have adverse effects on human health, including lead, arsenic and cadmium. Important characteristics in determining the potential for adverse health impacts include the mineralogy of phases containing the heavy metals and the particle size of the emissions.
Particle size distribution of fugitive emissions collected from the sinter plant, blast furnace and slag fuming operations indicated that greater than 90% of high temperature process emissions were less than 1.5 microns in diameter (EAD) and contained a number of phases, including PbS, PbSO4, Pb°, PbClOH, Pb5(AsO4)3Cl, As2O3, CdSO4, ZnS and ZnO.
The bioaccessibility of lead, arsenic and cadmium from the sinter plant, blast furnace and slag fumer was determined using a physiologically based extraction test (PBET). The percent of extractable Pb, As and Cd was assessed at 15 and 120 minutes. The results indicated Pb in sinter plant, blast furnace and slag fuming emissions were 39%, 95% and 96% soluble. Arsenic in the dusts was 49%, 100% and 89% soluble respectively and cadmium was 54%, 725% and 107% soluble, respectively.
The percentage of bioaccessible metals in the fume was found to increase with the level of oxidation of the species and with decreasing particle size. The results of this study showed that the emissions from high temperature processes contain a significant proportion of potentially bioavailable heavy metals and that efforts should be increased to eliminate fugitive emissions from these sources.