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Microbial sulfate reduction and metal attenuation in pH 4 acid mine water.

Church CD, Wilkin RT, Alpers CN, Rye RO, McCleskey RB - Geochem. Trans. (2007)

Bottom Line: Scanning electron microscope (SEM) analyses of sediment show 1.5-micrometer, spherical ZnS precipitates.Phospholipid fatty acid (PLFA) and denaturing gradient gel electrophoresis (DGGE) analyses of Penn Mine sediment show a high biomass level with a moderately diverse community structure composed primarily of iron- and sulfate-reducing bacteria.DGGE coupled with sequence and phylogenetic analysis of 16S rDNA gene segments showed populations of Desulfosporosinus and Desulfitobacterium in Penn Mine sediment and laboratory cultures.

View Article: PubMed Central - HTML - PubMed

Affiliation: US Geological Survey, California Water Science Center, 4165 Spruance Road, San Diego, CA 92101, USA. clinton.church@ars.usda.gov

ABSTRACT
Sediments recovered from the flooded mine workings of the Penn Mine, a Cu-Zn mine abandoned since the early 1960s, were cultured for anaerobic bacteria over a range of pH (4.0 to 7.5). The molecular biology of sediments and cultures was studied to determine whether sulfate-reducing bacteria (SRB) were active in moderately acidic conditions present in the underground mine workings. Here we document multiple, independent analyses and show evidence that sulfate reduction and associated metal attenuation are occurring in the pH-4 mine environment. Water-chemistry analyses of the mine water reveal: (1) preferential complexation and precipitation by H2S of Cu and Cd, relative to Zn; (2) stable isotope ratios of 34S/32S and 18O/16O in dissolved SO4 that are 2-3 per thousand heavier in the mine water, relative to those in surface waters; (3) reduction/oxidation conditions and dissolved gas concentrations consistent with conditions to support anaerobic processes such as sulfate reduction. Scanning electron microscope (SEM) analyses of sediment show 1.5-micrometer, spherical ZnS precipitates. Phospholipid fatty acid (PLFA) and denaturing gradient gel electrophoresis (DGGE) analyses of Penn Mine sediment show a high biomass level with a moderately diverse community structure composed primarily of iron- and sulfate-reducing bacteria. Cultures of sediment from the mine produced dissolved sulfide at pH values near 7 and near 4, forming precipitates of either iron sulfide or elemental sulfur. DGGE coupled with sequence and phylogenetic analysis of 16S rDNA gene segments showed populations of Desulfosporosinus and Desulfitobacterium in Penn Mine sediment and laboratory cultures.

No MeSH data available.


Reaction path modeling results showing trends in mineral precipitation as H2S(aq) is added to solutions containing Cd, Cu, and Zn. a) At pH 4, covellite (CuS), greenockite (CdS), and sphalerite (ZnS) precipitate, but mackinawite (FeS) remains undersaturated. b) At pH 7, all metal sulfides precipitate. The model was also run with the Eh fixed at 0.0 mV. At this condition elemental sulfur (dashed line) precipitation is favored at pH 4 following metal sulfide precipitation. Initial metals concentrations were Fe (150 mg L-1), Zn (100 mg L-1), Cd and Cu (15 mg L-1).
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Figure 7: Reaction path modeling results showing trends in mineral precipitation as H2S(aq) is added to solutions containing Cd, Cu, and Zn. a) At pH 4, covellite (CuS), greenockite (CdS), and sphalerite (ZnS) precipitate, but mackinawite (FeS) remains undersaturated. b) At pH 7, all metal sulfides precipitate. The model was also run with the Eh fixed at 0.0 mV. At this condition elemental sulfur (dashed line) precipitation is favored at pH 4 following metal sulfide precipitation. Initial metals concentrations were Fe (150 mg L-1), Zn (100 mg L-1), Cd and Cu (15 mg L-1).

Mentions: Reaction path modeling was carried out in order to examine these expected trends in more detail. The LLNL thermochemical database (thermo.com.V8.R6+.dat) was modified to include solubility data for mackinawite (FeS) [74]) and greenockite (CdS) [75]. Penn Mine ground water containing Zn2+, Cd2+, Cu2+, and Fe2+ was titrated with H2S(aq) at constant pH. At pH 4, model results predict the initial precipitation of CuS after addition of as little as 0.1 μg H2S(aq) per liter of solution (Figure 7a). With increasing H2S(aq), CdS precipitation is followed by ZnS precipitation (Figure 7a). Precipitation of an iron sulfide is not predicted at pH 4, but precipitation of pyrite, troilite, and pyrrhotite was suppressed following Labrenz et al. [50] because it is unlikely that the rate of formation of these phases can compete with the formation rate of mackinawite. However, at pH 7 mackinawite formation is predicted following precipitation of ZnS (Figure 7b). In model runs with Eh constrained (0.0 to 0.15 V), elemental sulfur precipitation is predicted at pH 4 (dashed line on Figure 7a) but not at pH 7. These model results further suggest that metal sulfide precipitation can occur at low pH and help explain the trace metal ratios and the observed formation of elemental sulfur and mackinawite in the microcosms at pH 4 and 7, respectively.


Microbial sulfate reduction and metal attenuation in pH 4 acid mine water.

Church CD, Wilkin RT, Alpers CN, Rye RO, McCleskey RB - Geochem. Trans. (2007)

Reaction path modeling results showing trends in mineral precipitation as H2S(aq) is added to solutions containing Cd, Cu, and Zn. a) At pH 4, covellite (CuS), greenockite (CdS), and sphalerite (ZnS) precipitate, but mackinawite (FeS) remains undersaturated. b) At pH 7, all metal sulfides precipitate. The model was also run with the Eh fixed at 0.0 mV. At this condition elemental sulfur (dashed line) precipitation is favored at pH 4 following metal sulfide precipitation. Initial metals concentrations were Fe (150 mg L-1), Zn (100 mg L-1), Cd and Cu (15 mg L-1).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2211471&req=5

Figure 7: Reaction path modeling results showing trends in mineral precipitation as H2S(aq) is added to solutions containing Cd, Cu, and Zn. a) At pH 4, covellite (CuS), greenockite (CdS), and sphalerite (ZnS) precipitate, but mackinawite (FeS) remains undersaturated. b) At pH 7, all metal sulfides precipitate. The model was also run with the Eh fixed at 0.0 mV. At this condition elemental sulfur (dashed line) precipitation is favored at pH 4 following metal sulfide precipitation. Initial metals concentrations were Fe (150 mg L-1), Zn (100 mg L-1), Cd and Cu (15 mg L-1).
Mentions: Reaction path modeling was carried out in order to examine these expected trends in more detail. The LLNL thermochemical database (thermo.com.V8.R6+.dat) was modified to include solubility data for mackinawite (FeS) [74]) and greenockite (CdS) [75]. Penn Mine ground water containing Zn2+, Cd2+, Cu2+, and Fe2+ was titrated with H2S(aq) at constant pH. At pH 4, model results predict the initial precipitation of CuS after addition of as little as 0.1 μg H2S(aq) per liter of solution (Figure 7a). With increasing H2S(aq), CdS precipitation is followed by ZnS precipitation (Figure 7a). Precipitation of an iron sulfide is not predicted at pH 4, but precipitation of pyrite, troilite, and pyrrhotite was suppressed following Labrenz et al. [50] because it is unlikely that the rate of formation of these phases can compete with the formation rate of mackinawite. However, at pH 7 mackinawite formation is predicted following precipitation of ZnS (Figure 7b). In model runs with Eh constrained (0.0 to 0.15 V), elemental sulfur precipitation is predicted at pH 4 (dashed line on Figure 7a) but not at pH 7. These model results further suggest that metal sulfide precipitation can occur at low pH and help explain the trace metal ratios and the observed formation of elemental sulfur and mackinawite in the microcosms at pH 4 and 7, respectively.

Bottom Line: Scanning electron microscope (SEM) analyses of sediment show 1.5-micrometer, spherical ZnS precipitates.Phospholipid fatty acid (PLFA) and denaturing gradient gel electrophoresis (DGGE) analyses of Penn Mine sediment show a high biomass level with a moderately diverse community structure composed primarily of iron- and sulfate-reducing bacteria.DGGE coupled with sequence and phylogenetic analysis of 16S rDNA gene segments showed populations of Desulfosporosinus and Desulfitobacterium in Penn Mine sediment and laboratory cultures.

View Article: PubMed Central - HTML - PubMed

Affiliation: US Geological Survey, California Water Science Center, 4165 Spruance Road, San Diego, CA 92101, USA. clinton.church@ars.usda.gov

ABSTRACT
Sediments recovered from the flooded mine workings of the Penn Mine, a Cu-Zn mine abandoned since the early 1960s, were cultured for anaerobic bacteria over a range of pH (4.0 to 7.5). The molecular biology of sediments and cultures was studied to determine whether sulfate-reducing bacteria (SRB) were active in moderately acidic conditions present in the underground mine workings. Here we document multiple, independent analyses and show evidence that sulfate reduction and associated metal attenuation are occurring in the pH-4 mine environment. Water-chemistry analyses of the mine water reveal: (1) preferential complexation and precipitation by H2S of Cu and Cd, relative to Zn; (2) stable isotope ratios of 34S/32S and 18O/16O in dissolved SO4 that are 2-3 per thousand heavier in the mine water, relative to those in surface waters; (3) reduction/oxidation conditions and dissolved gas concentrations consistent with conditions to support anaerobic processes such as sulfate reduction. Scanning electron microscope (SEM) analyses of sediment show 1.5-micrometer, spherical ZnS precipitates. Phospholipid fatty acid (PLFA) and denaturing gradient gel electrophoresis (DGGE) analyses of Penn Mine sediment show a high biomass level with a moderately diverse community structure composed primarily of iron- and sulfate-reducing bacteria. Cultures of sediment from the mine produced dissolved sulfide at pH values near 7 and near 4, forming precipitates of either iron sulfide or elemental sulfur. DGGE coupled with sequence and phylogenetic analysis of 16S rDNA gene segments showed populations of Desulfosporosinus and Desulfitobacterium in Penn Mine sediment and laboratory cultures.

No MeSH data available.