Investigating mercury in road sediment in Michigan City, Indiana: A new type of environmental pollution record

Abstract

Mercury (Hg) is well recognized as a toxic heavy metal known to detrimentally impact the health of humans and wildlife. A common source of Hg pollution is coal combustion emissions associated with energy generation. This study takes the novel approach of using road sediment to assess the presence, distribution, and concentrations of Hg in the environment. Here, the spatial distribution of Hg in road sediment is also evaluated relative to the Northern Indiana Public Service Company (NIPSCO) Generating Station in Michigan City, Indiana, U.S.—a coal-burning power plant. Given that NIPSCO plans to decommission the plant by 2028, this data provides a baseline for evaluating Hg concentrations in the local environment and for future assessment of environmental recovery from legacy pollution and/or impacts of pollution redistribution associated with site redevelopment. Our data reveal an average concentration of 6.8 (µg/kg) of Hg and a range from 1.5 µg/kg to 28.5 µg/kg in road sediment samples (n = 42). Across the ∼53 km² study area, the overall distribution of Hg is patchy and irregular spatially, however, higher concentrations are more proximal to the coal plant and are generally consistent with prevailing wind directions. Other significant Hg inputs are present in the region although, specifically two major areas of steel manufacturing located to the west of Michigan City and broadening the scope of sampling may be an essential next step. However, this investigation demonstrates that road sediment may be an effective medium for investigating Hg pollution in the environment globally.