A retrospective environmental assessment of Metropolis Lake (Kentucky): quantifying the human fingerprint on a fluviolacustrine depositional environment along the Ohio River

Metropolis Lake, a 50-acre lacustrine basin in Paducah, Kentucky, represents one of only three naturally formed shallow floodplain lakes in the state. Despite its status as a State Nature Preserve and its role as a refugium for rare fish species and ancient bald cypress trees, the lake’s proximity to major energy facilities—the Tennessee Valley Authority Shawnee Fossil Plant and the Paducah Gaseous Diffusion Plant (PGDP)—places it at the intersection of ecological sensitivity and industrial development. This study utilizes the lake’s sedimentary record to provide the first quantifiable evidence of how industrialization has shaped this unique fluvio-lacustrine environment.

As a sink for airborne and riverine contaminants, we hypothesize that Metropolis Lake sediments record a time series of human–lakescape interactions since at least the mid-20th century. Our research employs a multi-proxy approach—integrating sedimentology, geochemistry, and geochronology—to track the “human fingerprint” on the stratigraphic record. Specifically, we intend to establish a chronology using137Cs,210Pb, and Spheroidal Carbonaceous Particles (SCPs) to correlate contaminant fluxes with the operational histories of nearby power plants. Preliminary findings characterize the basin’s surface sediments as massive, organic-rich muds containing sponge spicules, diatoms, and charcoal, reflecting a well-mixed, shallow lacustrine environment subject to Ohio River flood pulses and groundwater influence. The total thickness of lacustrine sediment is not yet known; future coring and geophysics will reveal a fuller picture of the depositional history of this basin that will serve as the feedstock for a retrospective environmental assessment.

We hypothesize that peak concentrations of anthropogenic markers, such as Mercury (Hg) and SCPs, will synchronize with periods of maximum industrial output, distinguishing local point-source emissions from regional atmospheric background levels. By examining these anthropogenic geochemical anomalies and the preservation of human signals, this research addresses a critical knowledge gap, transforming Metropolis Lake’s sedimentary archive into a robust baseline for assessing the long-term ecological trajectory of the Ohio River floodplain.