Omar Felix

Chemical and Environmental Engineering

Metals and Metalloids in Atmospheric Dust: Can Lead Isotope Analysis Be Used for Source Apportionment?

When determining lead contamination sources, total lead concentration is not sufficient for a precise evaluation. In order to identify the source of a contaminant, isotopic analyses have been introduced as “fingerprints” of environmental pollution. Isotopic composition is a powerful tool for the determination of contamination sources because each source of lead may have a distinct isotopic ratio. By comparing these ratios, sources of lead can be identified and their relative contribution determined. Lead isotope ratios were measured for atmospheric dust samples from various field locations in Arizona. These locations included the City of Hayden, where there is an active copper mine and smelter, as well as arsenic and lead contaminated mine tailings; the Iron King Superfund site in Dewey-Humboldt, which has an inactive copper mine with arsenic and lead contaminated mine tailings, and Tucson, which represents a common urban environment used as a background for comparison. In addition to atmospheric aerosols, soil samples were taken at Hayden and Dewey-Humboldt at different distances from the main source to assess the extension of contamination from the source. Results have shown that lead isotopic analyses are a powerful tool for source apportionment; different isotopic ratios have been measured for different sites of study. The results obtained from the soil samples were compared to isotopic ratios obtained from aerosol samples in order to analyze possible deposition of aerosols.  Isotopic ratios measured for soil samples changed with distance from the source, indicating that the influence of the main source decreases with distance as was expected.