A REVIEW OF METAL POLLUTION IN URBAN ENVIRONMENTS IN THE CITY OF HAMILTON OHIO: PERSPECTIVES FROM BULK CHEMICAL ANALYSES, LEAD ISOTOPES AND ELECTRON MICROSCOPY

Hamilton, Ohio is a post-industrial Midwestern city that is in a mode of environmental and economic recovery. Over 150 years of intense manufacturing has left the city with a legacy of complex environmental pollution problems. One area of particular concern is the extent and nature of metal pollution in the city. Bulk chemical analyses indicate that metal pollution in road sediment and other sediment samples from within the city is pervasive and complex. Zinc, copper and lead have high concentrations well above environmental background as defined by local glacial till. Cu and Zn ratios from sediment samples show distinct populations associated with coal pollution sources. Electron microscopy identifies different types of metal particulate including individual particles and aggregates of clay particles with adsorbed pollutants. Specific pollutant sources are identified, including lead chromate derived from road paint. Lead isotopes identify lead chromate as a major contributor to lead pollution in the street environments that is more significant than lead contribution from coal. Furthermore direct microscopy and experimental evidence indicates that dissolution of lead chromate occurs commonly and suggests there is a contribution of dissolved lead and chromium to stormwater runoff. Furthermore direct evidence of the transport of lead chromate paint fragments from the street to the Great Miami River sediment is provided by electron microscopy. Coal burning is identified as a major contributor to pollution in the city and coal spherules are a common component of nearly all sediment samples. Barite is also suspected of being derived from coal as are other metal particles consistent in composition with steels used in coal furnaces. As the municipal coal plant is being decommissioned and the city transitions to a light industrial and service economy, the extent of pollution input should decline. These studies are a benchmark for urban pollution investigations in the Midwest and will serve as a base line to determine the extent of attenuation, if any, of metal pollution as the city enters a phase of environmental recovery.