SCANNING ELECTRON MICROSCOPY INVESTIGATION OF URBAN SOILS IN A REDEVELOPING REGION OF HAMILTON, OHIO SHOWS EVIDENCE OF LEGACY POLLUTION

The city of Hamilton located in Bulter County, Ohio had an extensive manufacturing history and is currently experiencing a new phase of revitalization and redevelopment. After 150+ years of metal manufacturing, paper mill operation and coal use, the extent and nature of metal pollution in the city is not well constrained. One issue the city faces is understanding the nature and form of legacy pollution as old properties are turned over and are developed. As an initial assessment of metal pollution, samples from disturbed soils were obtained from a site in the north central region of the city that is currently undergoing extensive redevelopment. Samples are from a 1 meter of exposure of mixed anthropogenic soils that were eventually removed as part of construction activities. Scanning electron microscopy investigation of samples indicate two primary forms of particulate pollution. A major form was technogenic spherules which exhibited a diverse range of textures including essentially smooth glassy surfaces, mixed dendritic to spinel-like textures, corroded textures or textures with irregular holes, and textures that are intermediate between these types. Energy dispersive spectroscopy analysis of technogenic spherules indicate compositions dominated by Mg, Al, Si, Ca, and Fe and are consistent with compositions observed in previous investigations of road sediment in Hamilton. Technogenic spherules were commonly on the order of several tens of micrometers in diameter. These particles are interpreted to be largely from coal-fired powerplants that have been either removed or converted to natural gas. Lead-bearing particles were identified by backscatter electron detection and energy dispersive spectroscopy and occurred commonly in multi-micrometer scale clusters composed of nanoparticles. Many of these particles appear to be dominated by elemental lead, however some textures and associated compositions are consistent with lead paint fragments. This investigation shows that a diverse variety of pollutants may occur in soils in this area of the city and care should be taken regarding possible children’s exposure, development of urban gardens, and workers that may have extensive exposure to soils in the area. XRF surveys of soils are recommended for future development and long term risk mitigation.