COMPARISONS OF METAL GEOCHEMICAL PHASE DISTRIBUTIONS IN NEW YORK CITY, PITTSBURGH, AND LOS ANGELES SOILS

Urban development, industrialization and vehicular emissions contribute trace metals to soils across the urban landscape. Background soil metals (i.e., away from the roadside and dripline) in cities depend on industrial history and local/regional contaminant transport. In the environment, trace metals are associated with various geochemical forms, corresponding to distinct soil fractions. This distribution across geochemical environments dictates metal accessibility to biota. While metal speciation and bioavailability are well described in the literature, variability in metal geochemical phase distributions across cities is less understood. This research evaluates metal total concentrations and phase distributions in urban soils of New York City, Pittsburgh, and Los Angeles and documents unique metal distribution patterns in each city. New York City soils were elevated in total concentrations of Pb, Cd, and Zn. Los Angeles, with its drier climate, had higher proportions of metals in the exchangeable phase, suggesting increased bioavailability. There is pronounced Mn enrichment in Pittsburgh soils, potentially indicative of the city’s intense industrial legacy. In particular, comparisons of Fe and Mn concentrations among the cities suggest distinct interactions between human and geochemical processes. The study findings confirm the complexity of urban soil metal contamination and demonstrate the importance of soil properties, environmental conditions, and industrial history in clarifying urban soil processes.