1) and the community compositions reflected this change in geochemical conditions. Several novel lineages were identified within the archaeal Thermoplasmatales order associated with the pyrite slump, and the Red Pool (pH 1.4) contained the only population of Acidithiobacillus. Relatively small populations of Sulfobacillus spp. and Acidithiobacillus caldus may metabolize elemental sulfur as an intermediate species in the oxidation of pyritic sulfide to sulfate. Experiments show that elemental sulfur which forms on pyrite surfaces is resistant to most oxidants; its solublization by unattached cells may indicate involvement of a microbially derived electron shuttle. The detachment of thiosulfate (S2O32-) as a leaving group in pyrite oxidation should result in the formation and persistence of tetrathionate in low pH ferric iron-rich AMD solutions. However, tetrathionate is not observed. Although a S2O32--like species may form as a surface-bound intermediate, data suggest that Fe3+ oxidizes the majority of sulfur to sulfate on the surface of pyrite. This may explain why microorganisms that can utilize intermediate sulfur species are scarce compared to Fe-oxidizing taxa at the Richmond Mine site."/>
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Table III Water chemistry of samples collected within the study site at the Richmond Mine 5-way area (at the 5-way, A, B, C weirs, and at the A-slump and red pool in 2001). Concentrations are reported in millimolar units, nd = not determined.

From: Acid mine drainage biogeochemistry at Iron Mountain, California

Sample name Date A1 As Ca Cd K Mg Mn Na Pb SiO2
99IM25-way May-99 54 1.6 5.9 0.14 nd 32 0.31 7.8 0.017 nd
OOIM15-way June-00 29 0.9 2.9 0.07 nd 17 0.15 4.5 0.009 nd
01IM15-way January-01 nd 0.316 nd 0.067 nd nd nd 0.596 nd 0.2
02IM15-way March-02 64 2.0 8.1 0.11 nd 32 0.31 11.8 0.026 nd
99IM2A1 May-99 61 1.2 6.1 0.10 nd 37 0.33 6.6 0.015 nd
OOIM1A1 June-00 47 0.4 3.3 0.05 3.3 26 0.24 1.5 0.047 1.3
01IM1A1 January-01 nd 0.3 nd 0.04 nd nd nd 0.5 0.036 nd
02IM1A1 March-02 63 1.5 6.8 0.10 nd 31 0.31 11.0 0.018 nd
99IM2B1 May-99 57 1.7 6.2 0.15 nd 30 0.31 9.2 0.019 nd
00IM1B1 June-00 34 0.9 2.9 0.08 nd 17 0.16 5.4 0.011 nd
01IM1B1 January-01 nd 0.4 nd 0.09 nd nd nd 0.6 0.018 nd
02IM1B1 March-02 nd nd nd nd nd nd nd nd nd nd
99IM2C1 May-99 51 0.8 3.8 0.13 3.4 29 0.29 2.5 0.046 1.5
OOIM1C1 June-00 41 0.6 3.2 0.10 2.7 23 0.23 1.9 0.039 1.3
01IM1C1 January-01 nd 0.4 nd 0.10 nd nd nd 0.5 0.039 nd
02IM1C1 March-02 65 1.8 8.1 0.10 nd 33 0.29 15.6 0.02 nd
02IMM B-back March-02 35 nd 7.3 0.11 nd 17 0.18 12.1 0.023 nd
02IM1 C-back March-02 67 nd 7.8 0.07 nd 32 0.29 16.0 0.02 nd
00IM1 A-slump June-00 3 0.2 1.9 0.00 nd 2 nd 0.2 0.015 1.0
01IM1 A red pool January-01 nd 0.0 nd 0.01 nd nd nd 0.2 0.006 nd
02IMM A-back March-02 80 2.5 10.2 0.13 nd 43 0.38 13.6 nd nd