Lung bioaccessibility of As, Cu, Fe, Mn, Ni, Pb, and Zn in fine fraction (< 20 μm) from contaminated soils and mine tailings

The present study aims (1) to characterize contaminated soils (n = 6) and mine tailings samples (n = 3) for As, Cu, Fe, Mn, Ni, Pb, and Zn content; and (2) to assess elemental lung bioaccessibility in fine fraction (d < 20 μm which might contribute to airborne particulate matter (PM) and thus be inhaled) by means of in vitro tests using Gamble's solution (GS) and an artificial lysosomal fluid (ALF). Elemental concentrations were high in the majority of samples, particularly for As (up to 2040 mg·kg^− 1), Fe (up to 30.7%), Mn (up to 4360 mg·kg^− 1), and Zn (up to 4060 mg·kg^− 1); and elemental concentrations (As, Cu, and Ni) in the sieved fraction (d < 20 μm) obtained from contaminated soils were significantly higher than in the bulk fraction (< 160 μm). In vitro tests with ALF yielded much higher bioaccessibility than tests with GS, and the use of ALF in addition to GS is recommended to assess lung bioaccessibility. Bioaccessibility in ALF was high for all elements after 2 weeks of testing both in terms of concentration (e.g. up to 1730 mg·kg^− 1 for As) and percentages (e.g. up to 81% for Pb). The elemental solubilization rate generally declined rapidly and continuously with time. Similarly, bioaccessibility increased rapidly and tended to reach a plateau with time for most samples and metals. However, it is not possible to recommend a general testing duration as the solubilization behavior was highly element and sample-specific.