THE FIRST POLLUTION INVESTIGATION OF ROAD SEDIMENT FROM MICHIGAN CITY, INDIANA: INITIAL FINDINGS

There are minimal investigations of road sediment as an effective media to decipher mercury (Hg) pollution in the United States. Mercury is a toxic heavy metal that is well known to be harmful to both humans and the environment. A common source of Hg is coal combustion emissions. This study reveals both the nature and spatial distribution of Hg concentrations in road sediment relative to the NIPCO Michigan City Generating Station in Michigan City, Indiana. A Milestone DMA-80 Hg analyzer was used to determine concentrations of Hg in samples and revealed an average concentration of 6.8 parts per billion (ppb) of Hg, with a range of concentrations of 1.4 ppb to 28.4 ppb. The distribution of Hg concentrations is interpreted to primarily originate from the coal plant, as Toxic Release Inventory (TRI) data from surrounding industrial sites do not indicate substantial Hg emissions. Although TRI data for NIPCO is broadly consistent with concentrations of Hg observed throughout Michigan City, we recognize that minor contributions from other local industrial and natural sources cannot be excluded. Additionally, scanning electron microscopy revealed technogenic spherules in multiple samples, which are indicative of nearby combustion processes. Technogenic spherules exhibit a range of sizes and textures. Some have smooth, glassy textures, while other textures include concentric rings, and others show abrasion. Spherules commonly varied in diameter from 1-20 μm. Overall, this investigation demonstrates that road sediment may be an effective media for investigating Hg and other forms of pollution associated with coal plants, and further study regarding the processes and complexities in similar industrial environments is warranted.