Arsenic bioaccessibility in gold mine tailings of Delita, Cuba

Abstract

A bioaccessibility test was carried out in four tailings collected at a former mining area in Delita, Cuba. A previous risk assessment study identified arsenic (As) as the main critical contaminant in this area and showed that the tailings had high As concentrations (up to 3.5%). This study aimed at: (i) evaluating As bioaccessibility in four tailings (R1, R2, R3 and R4) from a gold mining area to obtain a better health risk estimate; and, (ii) identifying the mineral phases responsible for most of the bioaccessible As using XRD, SEM-EDS, and XAS. The results showed that bioaccessible As in the tailings ranged from 0.65 to 40.5%. The main factors influencing As bioaccessibility were a high occurrence of amorphous iron arsenate; occurrence, even at low content, of iron oxyhydroxides and stability of mineral phases in the environment of the gastrointestinal tract. Although arsenopyrite, arsenates and goethite were confirmed by mineralogical methods such as optical microscopy, XRD, and SEM-EDS, XAS showed that scorodite–oxidation state As(+V)–was dominant in most of the tailings. This confirms that the low bioaccessibility of As in most of the tailings is due to the slow kinetics of As release from scorodite.