| Wilson, N; Brown, K; Webster-Brown, J: The behaviour of antimony and arsenic released from two surface geothermal features, New Zealand, (2010) | |
| Abstract: The antimony- and arsenic-rich geothermal features in the Taupo Volcanic Zone of New Zealand’s North Island allow investigation of how antimony (Sb) and arsenic (As) behave in essentially pristine aquatic environments. The discharges from Champagne Pool, a mixed alkali-chloride/sulfate hot spring at Wai-O-Tapu, and Frying Pan Lake, a chloride-sulfate hot spring at Waimangu, both contain in the order of 10 µg/kg Sb and several orders of magnitude more As. At Champagne Pool, downstream concentrations of Sb show diurnal variation and can be in excess of 200 µg/kg. A similar phenomena is observed for arsenic. Microbiological activity, which influences sulfide-sulfate equilibria, may contribute to the dissolution of sulfide minerals such as stibnite, Sb2S3. This activity may provide a mechanism that can explain the observed phenomena in both summer and winter. Antimony and As in the discharge from Frying Pan Lake exhibits little of the diurnal variation observed at Champagne Pool. At Wai-O-Tapu, most (> 80 %) of the Sb and As are removed from solution when it reaches Alum Lake, an acid-sulfate feature that contains elevated levels of dissolved sulfides. Most of the Sb and As discharged from Frying Pan Lake at Waimangu is transported into Lake Rotomahana, and any processes that act to remove the metalloids in the drainage between these two features are minor. It is concluded that, in the absence of dissolved sulfides and low (<3) pH conditions, Sb and As appear to behave generally conservatively downstream of geothermal features. |
