Geology of Greenland Survey Bulletin 176 - 1997
Review of Greenland activities 176, pp. 39-43: The role of bacteria in degradation of exposed massive sulphides at Citronen Fjord, North Greenland: project 'Resources of the sedimentary basins of North and East Greenland'
Bjarne R. Langdahl and Bo Elberling
The multidisciplinary research project 'Resources of the sedimentary basins of North and East Greenland' was initiated in 1995 with financial support from the Danish Research Councils (Stemmerik et al., 1996). The Citronen Fjord zinc prospect (Fig. 1) discovered by Platinova A/S in 1993 is by far the largest sulphide occurrence known in North Greenland, and is currently being investigated as a potential exploitable resource. However, the mining and processing of sulphide ores can create serious pollution problems in the surrounding terrestrial and aquatic ecosystems by exposing large amounts of sulphidic material to atmospheric oxygen and ?attack- by mineral-oxidising bacteria. At lower latitudes, the slow abiotic oxidation of metal sulphides is known to be significantly accelerated by bacterial attack. A microbiological investigation of the Citronen Fjord zinc deposit was initiated in the summer of 1995 to investigate the role bacteria might play in oxidation of sulphidic material in High Arctic areas. This is a joint project involving the Danish Environmental Research Institute (Department of Arctic Environment) and the University of Aarhus (Department of Microbial Ecology).
Pyrite is the dominant sulphide mineral in the Citronen Fjord deposit (Kragh et al., 1997). Pyrite oxidises when exposed to atmospheric oxygen and meteoric water, and acid, sulphate and iron are released:
FeS 2 + 7/2 O 2 + H 2 O --> Fe 2+ + 2 SO 4 2- + 2 H +
At Citronen Fjord, oxidation of the exposed sulphides has produced impressive, vividly coloured gossans (Figs 1, 2). These gossans offer a rare opportunity to study microbial and chemical sulphide oxidation processes, as well as the microbial diversity in a still undisturbed environment. The present investigation represents a zero-line study of microbial activity, and will provide an important reference standard with respect to the potential effects of mining of the Citronen Fjord zinc deposit on microbial processes.
The project addresses two main subjects: (1) the physiology of microbes living in this extreme environment; and (2) the role of bacteria in degradation of exposed metal sulphides. Detailed physiological experiments and tests of isolated microbes have recently been conducted in the laboratory and the results are discussed briefly below.
The role of bacteria in the degradation of sulphidic material has been investigated in a combination of in situ measurements and laboratory studies. High priority was given to evaluation of the total in situ oxidation of sulphidic material in the gossans, including abiological and biological processes. The relative importance of bacterial and chemical oxidation will be evaluated on the basis of future laboratory experiments combined with the results obtained from total oxidation rate measurements and analyses of collected water samples.
Oxygen consumption measurements
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