Spatial analysis of industrial contamination using road sediment in a heavily urbanized area

Northern Lake County, Indiana, United States, is a heavily industrialized area, containing steel mills, oil refineries, and chemical manufacturers surrounded by extensive residential neighborhoods. As part of an ongoing community-academic partnership to address environmental contamination in this area, road sediment was selected as a sample medium which is abundant, simple, and cost-effective. Elemental analysis of road sediment can provide a short-term history of atmospheric deposition of pollutants of interest. In this study, 387 road sediment samples were collected from 332 sampling sites in Northern Lake County across two years. The samples underwent particle-induced X-ray emission and gamma-ray emission spectroscopy at the University of Notre Dame to quantify up to 24 elements in each sample. Empirical Bayesian Kriging geospatial analysis and Positive Matrix Factorization were completed to identify potential contamination hotspots and sources. Empirical Bayesian Kriging results showed heavy geoaccumulation indices and high contamination factors for elements near areas of ongoing industrial activity in the region, particularly along the Lake Michigan coastline. Positive Matrix Factorization showed source contributions that may be linked geospatially to regions of heavy industrial activity, which was further supported by corresponding individual correlations between elements of interest. The combination of road dust elemental analysis and geospatial techniques helped to better illustrate the short-term contamination landscape of Northern Lake County and inform community members about predicted regional hotspots. Future work will compare these "background" elemental concentrations outdoors to those measured from interior house dust collected in this region, to identify potential pathways for personal exposure.