A multidisciplinary investigation on bio-oxidation gold mine tailings from Dandong, China as a potential arsenic pollution source

Abstract

Very little is known about bio-oxidation tailings as an arsenic (As) pollution source. A comparison study was carried out between three flotation tailings (N1-1, N1-2 and N1-3) and three bio-oxidation tailings (N2-1, N2-2 and N2-3), collected from the Yangshu gold mine in China. A combined approach of mineralogy, geochemistry and environmental geochemistry was applied to explore geochemical and mineralogical properties, As fractions and its release behavior of the bio-oxidation tailings. The results showed that extremely high total As (TAs) of 25,200–27,100 μg/g (air-dry weight) observed in N2-1, N2-2 and N2-3 was about 30 times higher than that (616–940 μg/g) in N1-1, N1-2 and N1-3. The main elements were As, Ca, Fe and S, the mineral phases were gypsum (CaSO4) (accounting for >95 wt%), and the corresponding As was present as FeAsS and As2O5 in N2-1, N2-2 and N2-3. A larger amount of As in the water-soluble (5.80–9.98 μg/g), exchangeable (9.42–15.70 μg/g), carbonate-bound (29.23–63.36 μg/g) and Fe/Mn oxide-bound (5825–12,218 μg/g) fractions was found in N2-1, N2-2 and N2-3. Solution TAs released from N2-2 was higher than the level released from N1-1, and predominantly present in the oxidised form as arsenate As(V) in 192 h. The bio-oxidation tailings are able to release more As, and are a potential As pollution source of soil, surface and ground water.