Contamination of Slag-Derived Heavy Metals in Water, Sediment, and Ceratophyllum demersum Under Ambient Environmental Conditions in Carp Lake, Davenport, IA, USA

Abstract Metal processing has played a key role in modern industrial development. In addition to economic prosperity, the residuals from these processes have resulted in a legacy of environmental contamination. While there are numerous laboratory studies of metal leaching from slag piles, there remains a lack of information on the impacts of iron slag weathering under ambient environmental conditions. This study builds on previous work where environmental weathering of an abandoned iron slag pile at Carp Lake, located adjacent to the Mississippi River in Davenport, Iowa, USA, was found to have contaminated soils and terrestrial vegetation with cadmium, copper, nickel, lead, and zinc. Lake water, lake sediment, and vegetation ( Ceratophyllum demersum ) were collected, processed, and analyzed to determine concentrations of the previously cited metals in each compartment. Metal concentrations in water were distributed homogeneously across Carp Lake. Notably, Cd and Pb concentrations exceeded US Environmental Protection Agency criteria for acute and chronic exposure, respectively. Average sediment metal concentrations were highest at the site located closest to the slag pile. C. demersum (coontail) appeared in Carp Lake after major regional flooding in 2019 and contained measurable concentrations of Cd, Cu, Ni, Pb, and Zn; Cd and Ni were present in plant tissue at levels that exceeded literature reports. While metal concentrations in coontail suggested that the plant might be used to recover select metals from Carp Lake, its role as a pathway for metal accumulation and biomagnification in aquatic wildlife and migratory waterfowl remains an important issue for further study.