Dissertation Defense-Marika Avkopashvili

METAL POLLUTION DYNAMICS IN COMPLICATED URBAN ENVIRONMENTS Urban soils preserve long-term records of pollution produced by urbanization, industrial development, and atmospheric deposition. In historically industrial cities, these records are difficult to interpret because metal concentrations reflect overlapping effects of pollution sources, geology, climate, topography, soil chemistry, and atmospheric transport. This dissertation investigates metal pollution dynamics in complex urban environments by integrating soil geochemistry, sequential extraction, Pb isotope source tracing, atmospheric inversion analysis, gamma radiation records, unconventional well data, and HYSPLIT air-mass trajectory modeling. First, I compared Pittsburgh soils with available New York City and Los Angeles datasets, showing that elevated Mn in Pittsburgh reflects industrial legacy, vegetation cycling, and metal retention processes. In contrast, Los Angeles showed greater exchangeable metal fractions, highlighting the role of climate in metal bioavailability. Second, I investigated soil metal enrichment around the Clairton Coke Works. Soils surrounding the facility showed metal enrichment near the plant, although spatial patterns were not explained by distance alone. Pb isotope ratios indicated that soil Pb reflects a mixture of lithogenic background, legacy anthropogenic inputs, and a local coking-related industrial signature most evident near the facility and along atmospheric transport pathways. Third, I analyzed long-term radiosonde, EPA RadNet gamma, unconventional gas well, and HYSPLIT trajectory datasets to examine how atmospheric conditions influence near-surface gamma radiation variability in Pittsburgh. These analyses show that atmospheric inversions influence gamma variability, especially under specific daytime, seasonal and air-mass direction conditions, while well-related signals appear indirect and dependent on transport pathways and boundary-layer stability. Together, thes