GEOCHEMISTRY OF URBAN SOILS IN INDIANAPOLIS, INDIANA: A STUDY OF LEAD AND OTHER ANTHROPOGENIC METALS AT THE RESIDENTIAL SCALE

Indianapolis, Indiana has an industrial past that led to many environmental and public health concerns. One of the contaminants impacting urban soils is lead (Pb). Introduced by lead-based paint, leaded gasoline, smelting and other metal-related industries, this known neurotoxin left a legacy in many urban soils and results in modern day acute and chronic exposure risks. This research helps to determine where areas of high-risk are located on a residential scale; a crucial step in remediating this public health concern. Through the Safe Urban Gardening Initiative, over 1200 soil samples from Indianapolis were collected and analyzed to inform gardeners about safe practices and to provide a spatially extensive database for determining metals distribution. Samples were taken from four specific locations at each address: yard, garden, near street, and the dripline. We found that samples taken nearest to the home have the highest concentrations of Pb, with an average value of 672 ppm at the dripline (compare to a ‘background’ level of 20-50 ppm). Samples near the street averaged 266 ppm. Those in the yard and garden were usually the lowest in Pb. These values suggest the home may be a direct source from lead-based paints and/or a secondary source via trapping and concentrating Pb-enriched dust through a barrier effect.

Along with Pb, other metals were analyzed from these samples (Mn, Zn, Ba, Cr, and Cu). The concentrations of these metals in urban soils is poorly quantified and, while the impact of Pb exposure on human health is well understood and publicized, the same cannot be said for other metals often found in these soils. This data begins to offer some insight into what extent these metals exist in urban soils and where the highest concentrations are found on a residential scale. The data also reveals correlations between Pb and other metals which may make it possible to identify sources of the metals. No significant correlation was found between Pb and Ba, Cr, Cu, or Mn suggesting the sources for these metals are different than those of Pb. The strongest correlation (0.697) came with Zn, suggesting that Zn and Pb may have similar sources. One goal of this study is to bring attention to metals other than Pb that exist in urban soils and initiate exploration into the possible effects that exposure to high concentrations may have on human health.