BACKGROUND SOIL TRACE METALS ACROSS CITIES CLARIFY COMPLICATED MIXES

Soil trace metal patterns and concentrations vary across cities, influenced by a variety of factors. A lot is known about lead gasoline additives and paint lead inputs to urban systems, but we don’t necessarily know how urban processes change soils away from these lead-enriched zones. Collection of background metal soil measurements away from roads and buildings is a vital part of minimizing impacts to human and ecosystem health, as these zones may cause unexpected exposures and reveal the interactions between urban and geochemical processes. However, while background measurements are becoming more common, there are few comparisons of background soil concentrations among cities, limiting our ability to draw conclusions about soil contamination mechanisms. This presentation compares trace-metal data from 13 North American cities, with a focus on lead and arsenic in “background” samples. In addition, potential industrial sources in these cities are assessed and compared with the chemistry data. Preliminary findings suggest interesting patterns, for example, historical cotton production centers seem to inherit lead and arsenic from pesticide use. Background data can clarify sources of trace metals and ultimately help mitigate and prevent negative impacts to human and ecosystem health. This work fills an important gap in our understanding of urban geochemical systems and provides important insight into the complicated urban geochemical system.