Size-dependent Characterization of Dusts from Mine Tailings Deposits

摘要

Airborne particles originating from mine tailings deposits may contain toxic concentrations of metal and metalloid contaminants. The risks associated with such particles are related to particle size given that finer particulates are more easily transported off-site and may be readily inhaled. Implications to human health should be assessed through a holistic size-resolved characterization comprised of geochemical, bioavailability, and toxicity experiments, which require gram-size samples that are difficult to collect using conventional sampling instruments. To address this limitation, a laboratory dust generator was developed with the goal of producing size-fractionated dust representative of the field to provide a common sample for multidisciplinary studies. In the dust generator setup, a clean air source enters a rotating drum where the source material is mixed and re-suspended. Entrained particles follow the airflow towards a cyclone separator. Fractionated material is then collected in a settling chamber and subjected to characterization. The instrument was optimized for the fractionation of tailings deposits from the arsenic and lead-contaminated Iron King Superfund site in Dewey-Humboldt, AZ. Chemical characterization shows the contaminants are more concentrated in the smaller size fractions, which are also more likely to affect surrounding communities and ecosystems. The equipment and methods developed for this assessment ensure uniformity between physical and chemical characterization, bioavailability and toxicity studies, thus providing a comprehensive representation of the emission source and the associated risks of exposure.