The impacts of Fe mine tailings in the oral bioaccessibility of potentially toxic elements: a study case on the world's largest mining disaster

This dataset compiles the results of a multidisciplinary geochemical study evaluating the role of iron (Fe) oxides in controlling the oral bioaccessibility of potentially toxic elements (PTEs) in estuarine soils affected by Fe-rich mine tailings from the 2015 Mariana disaster (Brazil). Soil samples were collected from eight locations in the Doce River estuary, sixyears after the arrival of tailings in Regência (2021). Given that soil oxidation can occur during sample preparation (e.g., drying), potentially altering PTE behavior, we hypothesized that this step may influence oral bioaccessibility outcomes. To investigate this, in vitro oral bioaccessibility tests (Unified BARGE Method, UBM) were applied to three sets of samples: FD (Fine and Dry): Air-dried at 45 °C and sieved to <250 µm (standard method); BD (Bulk and Dry): Air-dried at 45 °C and sieved to <2 mm; BW (Bulk and Wet): Field-moist samples, refrigerated immediately after sampling (<4 °C), without drying or sieving. Sample Preparation Note:All samples labeled as BW, BWg, BWgi, FDg, and FDgi were freeze-dried (lyophilized) prior to spectroscopic analysis. This procedure was used to preserve sample integrity after in vitro digestion steps and to standardize moisture content across treatments. The study also examined the distribution of Fe and PTEs in the solid phase using non-specific sequential extraction (CISED) and mineralogical characterization (FTIR, DRS, and XRD), both before and after UBM testing. The dataset includes: Field data (pH, Eh, temperature, moisture, GPS coordinates); UBM bioaccessibility results; Total and extractable element concentrations (USEPA 3052 and sequential extraction); FTIR, DRS, and XRD spectra and images; Soil particle size distribution (granulometry); CISED extraction data (non-specific 14-step leaching profiles). These data contribute to understanding the influence of Fe oxides on PTE speciation and oral bioaccessibility, supporting environmental risk assessments in Fe-contaminated estuarine systems.