Spatial Distribution of Extractable Metals in Sediment Leached from Iron Foundry Slag

Full Title: Spatial Distribution of Extractable Metals in Sediment Leached from Iron Foundry Slag Deposit at Carp Lake, Davenport, IA, USA
Authors: Claire Helmke, Anshu Singh, and Roger C. Viader

Authors: Slag, a byproduct of the iron and steel smelting process, can contain elevated concentrations of metals such as cadmium, copper, iron, lead, nickel, zinc, and others. Before federal regulations required proper disposal, foundries deposited slag into the environment across the Midwest. Carp Lake, south of Davenport, IA, and part of the Nahant Marsh complex, has a slag deposit estimated to be 4,786 m3 (6,261 yd3) that was dumped on its northeast shore since as early as the 1920s. Due to environmental weathering, metal-laden slag is liberated from the pile and accumulates in the lake sediment. The metals persist indefinitely in the sediment and are a secondary contributor of metal contamination to the aquatic ecosystem. Since Carp Lake comes in direct contact with the Mississippi River during flood events, a study was conducted to better understand the extent of contamination prior to developing detailed remediation plans. Sediment samples were collected from 16 locations across Carp Lake and analyzed to determine the extractable concentrations of Cd, Cu, Ni, Pb, and Zn. A bathymetric map of the lake was developed using sonar and a Lowrance chart plotter. The effect of sample site distance from the edge of the slag pile and the depth of the samples were tested to determine if a relationship existed with the concentrations of individual metals. A relationship was found between the distance from the slag pile and the contamination within the sediment. However, there was no relationship between the depth of the sediment and the contamination of heavy metals.

This presentation was part of the 17th Emiquon Science Symposium which took place March 30, 2022 as a zoom webinar.