COUPLING METEOROLOGY, MULTI-ELEMENT CONCENTRATIONS, AND PB ISOTOPES FOR SOURCE IDENTIFICATION OF FINE PARTICULATE MATTER AIR POLLUTION IN EAST ST. LOUIS

The St. Louis urban area is presently designated as a non-attainment area for airborne fine particulate matter < 2.5 μm in diameter (PM_2.5) by the U.S. Environmental Protection Agency. PM_2.5 is a concern from an adverse health effects perspective, the types of metals and their concentration in the PM is of particular concern. High-time resolution samples (every hour or less) have been shown to provide improved resolving power to identify PM_2.5 sources and their overall impacts to air quality. Ambient fine aerosols were collected at thirty minute intervals using a semi-continuous elements in aerosol system (SEAS) at the East St. Louis Midwest Supersite in 2002. The samples were analyzed for multi-element concentrations and Pb isotopes using sector field ICP-MS. By coupling meteorological measurements with the elemental and Pb isotope data, fingerprints for sources of PM from primary metal smelters, iron and steel production facilities, coal fired power plants and traffic sources were identified. The Mississippi Valley Type ore deposits in Missouri provided a unique low ²⁰⁷Pb/²⁰⁶Pb and ²⁰⁸Pb/²⁰⁶Pb isotope ratio fingerprint for smelter emissions which could be readily distinguished from higher Pb isotope ratios from other sources, and the more thorogenic Pb isotope ratios (higher ²⁰⁸Pb/²⁰⁶Pb) from coal fired power plant emissions. The thirty minute sample acquisition was critical for differentiating between sources from similar transport directions. Case studies from three periods with differing flow regimes will be used to demonstrate the resolving power of this coupled source apportionment technique.