A laboratory-based microcosm study was conducted from September 2023 to July 2024 by the Office of Research (ORD) Cincinnati Lab (ORD-CESER-LRTD-CAISB). QA Category B data was generated following established methodologies and quality-assurance procedures. ORD clearance policy requirements for internal technical review, quality assurance review and supervisor reviewer/approval were met. This data is to be published on ScienceHub following satisfaction of EPA ORD policies. No interpretation of the data is provided. The results of this study will be described in detail in a publication subjected to external, expert peer review.

Sediments, collected from the Lower Coeur d’Alene Basin (CDA) in the Bunker Hill Mining and Metallurgical Complex Superfund Site (Bunker Hill), were used in microcosms set up and monitored by ORD Cincinnati staff. The study was designed to evaluate the impact of repeated wetting and drying cycles on sediment porewater metal concentrations in the Lower CDA. Sediments were subjected to three wetting-drying cycles, and porewater was sampled throughout the duration of the experiment. Two sediment types were subjected to two different treatments (Permanently wet vs wet/dry) with 3 replicates of each, yielding 12 total microcosms. Each wetting-drying cycle lasted 30 days and was followed by 30 days of drying (Figure 1). This data package summarizes sediment, sediment porewater and surface water results including total metal concentrations in sediment and sediment porewater, dissolved organic carbon (DOC) concentrations, dissolved iron and sulfide, UV absorbance at 254 nm, YSI measurements of porewater, sulfate concentrations, times series data of redox potential (Eh), and lead (Pb) speciation analysis of select samples. See attached QA Memo detailing QA/QC procedures used for each parameter and a schematic of the microcosms.