Bioaccessibility of Lead and Arsenic in Mining Waste and Mining-Affected Soils

In vitro bioaccessibility tests are used to estimate the release of contaminants from environmental samples during simulated digestion, making them available for intestinal absorption. In most cases, the samples are fine-grained materials with varying chemical, physical, and mineralogical properties, but it is not always clear how these properties influence the bioaccessibility of elements. The present study focusses on the bioaccessibility of lead (Pb) and arsenic (As) in mining waste and mining-affected soils. From the literature, data from mining waste and mining-affected soil samples were used to investigate the relation between chemical (element composition, pH, organic carbon content), physical (grain size distribution), and mineralogical properties of the samples and the gastric and intestinal bioaccessibility of Pb and As. Mean gastric As bioaccessibility was significantly lower in acidic samples than neutral and alkaline samples. A significant difference was also found between As and Pb bioaccessibility in mining residues and mining-affected soil samples. Overall, total Pb an As concentrations and pH were the most significant predictors of Pb and As bioaccessibility. Due to the lack of (quantitative) mineralogical data in many papers, it was not possible to make precise predictions of As and Pb bioaccessibility based on mineralogical sample composition. Despite the challenging nature of quantitative mineralogical characterization, it can contribute to a more precise estimation of the bioavailability of Pb and As in mining waste. Given their significant impact on the bioavailability of metal(loid)s, pH and the (quantitative) mineralogical sample composition should be more systematically determined and reported.