Quantification of sulphide oxidation rates in marine sediment

AbstractWater radiolysis continuously produces H2 and oxidized chemicals in wet sediment and rock. Radiolytic H2 has been identified as the primary electron donor (food) for microorganisms in continental aquifers kilometers below Earth’s surface. Radiolytic products may also be significant for sustaining life in subseafloor sediment and subsurface environments of other planets. However, the extent to which most subsurface ecosystems rely on radiolytic products has been poorly constrained, due to incomplete understanding of radiolytic chemical yields in natural environments. Here we show that all common marine sediment types catalyse radiolytic H2 production, amplifying yields by up to 27X relative to pure water. In electron equivalents, the global rate of radiolytic H2 production in marine sediment appears to be 1-2% of the global organic flux to the seafloor. However, most organic matter is consumed at or near the seafloor, whereas radiolytic H2 is produced at all sediment depths. Comparison of radiolytic H2 consumption rates to organic oxidation rates suggests that water radiolysis is the principal source of biologically accessible energy for microbial communities in marine sediment older than a few million years. Where water permeates similarly catalytic material on other worlds, life may also be sustained by water radiolysis.

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Note: Natural heavy-metal release by sulphide oxidation in the High Arctic

Canadian Geotechnical Journal ◽

10.1139/t98-047 ◽

1998 ◽

Vol 35 (5) ◽

pp. 895-901 ◽

Cited By ~ 13

Author(s):

Bo Elberling ◽

Bjarne Riis Langdahl

Keyword(s):

Oxygen Uptake ◽

Zinc Content ◽

High Arctic ◽

Metal Release ◽

Sulphide Oxidation ◽

Oxidation Rates ◽

Metal Contents ◽

Uptake Rates ◽

Order Of Magnitude ◽

Heavy Metal Release

An assessment of the environmental impact of the weathering of sulphide-rich rocks at Citronen Fjord, North Greenland, provided information on sulphide oxidation rates and metal release from outcrops of sediment-hosted, stratiform ore that may be mined for its zinc content. In situ oxygen uptake rates were measured at the surface of partly weathered sulphide-rich outcrops and compared with metal contents in streams and soil water. The oxygen uptake rates measured during August 1996 were of the same order of magnitude as those reported from mine tailings at lower latitudes. The variation in metal concentrations and pH of the drainage waters reflects the spatial variation in sulphide oxidation and carbonate buffering. High weathering rates of sulphide minerals occur in the High Arctic during the summer, and release of heavy metals must be considered a potential environmental issue if mining is initiated.Key words: sulphide oxidation, pyrite, sphalerite, oxygen, High Arctic, zinc.

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Evaluation of sulphide oxidation rates: a laboratory study comparing oxygen fluxes and rates of oxidation product release

Canadian Geotechnical Journal ◽

10.1139/t94-045 ◽

1994 ◽

Vol 31 (3) ◽

pp. 375-383 ◽

Cited By ~ 56

Author(s):

B. Elberling ◽

R.V. Nicholson ◽

E.J. Reardon ◽

R Tibble

Keyword(s):

Water Table ◽

Oxidation Rate ◽

Water Saturation ◽

Temporal Trends ◽

High Water ◽

Sulphide Oxidation ◽

Oxidation Rates ◽

Mapping Tool ◽

Fine Grain ◽

The Impact

A series of column experiments were conducted to evaluate three methods to determine sulphide oxidation rates in mine tailings. Measurements were made of (i) the flux of oxygen across the surface of the tailings, (ii) the oxygen consumption rates at the tailings surface, and (iii) the total sulphate produced in the pore water over time. Two columns were prepared with a mixture of quartz sand and pyrrhotite and overlain with varying thicknesses and grain sizes of a nonreactive layer. The impact of nonreactive layers with varying water-table depths on the overall oxidation rate was also evaluated. Modelling was applied to verify the importance of diffusion and kinetic control of the different column configurations. The results indicate that the overall rate of oxidation is reduced when fine-grain layers are applied. This is due to the high water saturation conditions generated by the fine material regardless of the depth to the water table. The consistency and precision of the methods used to measure relative oxidation rates were noted and a new practical field mapping tool is recommended. The new method provides rapid measurements of relative oxidation rates that can be applied to existing tailings rehabilitation with soil-type covers to show spatial and temporal trends. Key words : sulphide oxidation, tailings, laboratory experiment, oxidation rate methods, water saturation, cover materials.

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