Formation of Carbonate Nanoglobules by a Mixed Natural Culture under Hypersaline Conditions

The present study demonstrated formation of Ca and P rich nanoglobules by a mixed natural halophilic population enriched from hypersaline lake sediments in laboratory culture experiments. Nanoglobules consisting of complex mixture of Ca, P, O, and C with minor amount of Mg occurred in the external envelop of bacterial cell in the first week of incubation at various Mg+2/Ca+2 ratios and salinity at 30 °C. Unlike the control experiments (e.g., non-viable cells and without cells), later aggregation and transformation of nanoglobules caused the precipitation of calcium and/or magnesium carbonates in variable amount depending on the Mg+2/Ca+2 ratios of the medium after 37 days of incubation. By showing the nucleation of carbonates on bacterial nanoglobules closely associated with the cell surfaces of mixed natural population this study emphasis that formation of nanoglobules may not be specific to a microbial strain or to activity of a particular microbial group. Formation of carbonate nanoglobules under various conditions (e.g., Mg+2/Ca+2 ratios, salinity) with the same halophilic culture suggest that the although metabolic activity of bacteria have an influence on formation of nanoglobules the mineralogy of nanoglobules may be controlled by the physicochemical conditions of the precipitation solution and the rate of mineral precipitation

Mineralogy, Geochemistry and Fluid Inclusion Data from the Tumanpınarı Volcanic Rock-Hosted Fe-Mn-Ba Deposit, Balıkesir-Dursunbey, Turkey

The Tumanpınarı mineralization is a volcanic rock-hosted epithermal Fe-Mn-Ba deposit located in the southwestern part of Dursunbey, Balıkesir, Turkey. The deposit constitutes one of the most important deposits of the Havran-Dursunbey metallogenic sub-province in which numerous Early Miocene Fe-Mn-Ba deposits are distributed. The ore occurs as open-space fillings in faults, fractures, and breccias in the andesite. Early hydrothermal activity was responsible for four types of hypogene alteration in decreasing intensity: silicification, sericitization, hematization and argillic alteration. The mineral assemblage includes pyrolusite, psilomelane, hematite, and barite as well as minor magnetite, manganite, poliannite, limonite, braunite, bixbyite, galena, pyrite, and goethite. Mineralogically, three ore types are recognized as pyrolusite + psilomelane + hematite + barite ore, pyrolusite + psilomelane + poliannite ore and barite + pyrolusite + psilomelane + hematite ore (barite-dominant ore). In addition to Fe, Mn and Ba, the ore contains substantial quantities of Pb, Zn, As. Chemically, the transition from fresh to altered rocks has little effect on the elemental levels for Si, Al, Fe, Ca, Mg, K, Rb, Sr and H2O. The homogenization temperature of fluid inclusions hosted in the main stage quartz and barite ranged from 113 to 410 °C with salinities ranging from 0.4 to 14.9 eq. wt % NaCl, respectively. Overall, the available data suggest that the deposits formed as the result of the interaction of two aqueous fluids: a higher-salinity fluid (probably magmatic) and a dilute meteoric fluid

Tetrathionate and Elemental Sulfur Shape the Isotope Composition of Sulfate in Acid Mine Drainage

Sulfur compounds in intermediate valence states, for example elemental sulfur, thiosulfate, and tetrathionate, are important players in the biogeochemical sulfur cycle. However, key understanding about the pathways of oxidation involving mixed-valance state sulfur species is still missing. Here we report the sulfur and oxygen isotope fractionation effects during the oxidation of tetrathionate (S4O62-) and elemental sulfur (S degrees) to sulfate in bacterial cultures in acidic conditions. Oxidation of tetrathionate by Acidithiobacillus thidoxidans produced thiosulfate, elemental sulfur and sulfate. Up to 34% of the tetrathionate consumed by the bacteria could not be accounted for in sulfate or other intermediate-valence state sulfur species over the experiments. The oxidation of tetrathionate yielded sulfate that was initially enriched in S-34 (epsilon S-34(so4-S4O6)) by +7.9 parts per thousand followed by a decrease to +1.4 parts per thousand over the experiment duration, with an average epsilon S-34(SO4-S4O6) of +3.5 +/- 0.2 parts per thousand after a month of incubation. We attribute this significant sulfur isotope fractionation to enzymatic disproportionation reactions occurring during tetrathionate decomposition, and to the incomplete transformation of tetrathionate into sulfate. The oxygen isotope composition of sulfate (delta O-18(so4)) from the tetrathionate oxidation experiments indicate that 62% of the oxygen in the formed sulfate was derived from water. The remaining 38% of the oxygen was either inherited from the supplied tetrathionate, or supplied from dissolved atmospheric oxygen (O-2). During the oxidation of elemental sulfur, the product sulfate became depleted in S-34 between -1.8 and 0 parts per thousand relative to the elemental sulfur with an average for epsilon S-34(So4-S0) of -0.9 +/- 0.2 parts per thousand and all the oxygen atoms in the sulfate derived from water with an average normal oxygen isotope fractionation (epsilon O-18(SO4-H2O)) of -4.4 parts per thousand The differences observed in delta O-18(SO4) and the sulfur isotope composition of sulfate (delta S-34(so4)), acid production, and mixed valence state sulfur species generated by the oxidation of the two different substrates suggests a metabolic flexibility in response to sulfur substrate availability. Our results demonstrate that microbial processing of mixed-valence-state sulfur species generates a significant sulfur isotope fractionation in acidic environments and oxidation of mixed-valence state sulfur species may produce sulfate with characteristic sulfur and oxygen isotope signatures. Elemental sulfur and tetrathionate are not only intermediate-valence state sulfur compounds that play a central role in sulfur oxidation pathways, but also key factors in shaping these isotope patterns

S and O isotope ratios of sulfate suggest enhanced monosulfides oxidation in a historical Pb–Zn mine site

© 2021 Elsevier LtdAqueous and solid tailings geochemistry of two contrasting depositional sites (water-saturated and subaerial) in a historical Pb–Zn mine tailings in Balya, Turkey were chemically and isotopically (δ34S and δ18O) characterized to trace source of sulfate and elucidate oxidation pathways of sulfide mixtures. Aqueous geochemistry data of water-soluble fractions (n = 15) obtained from the batch leaching tests applied on the subaerial mine tailings (SA-MT) revealed three geochemically distinct zones: i) oxidized zone (OXZ, 10–75 cm), ii) transition zone (TZ, 75–125 cm) and iii) unoxidized zone (U-OXZ, 125–350 cm). The OXZ is characterized by a sharp decrease in sulfur and metals contents of the tailing rocks while high sulfate and metals concentrations in their water-soluble fractions. In contrast, the TZ and U-OXZ zones are mainly characterized by low sulfate but relatively high metal concentrations with slightly acidic pH values (4.9–6.2). Compared to the SA-MT tailings geochemical profiles of the pore waters of the water-saturated tailings (S-MT) showed remarkably high sulfate, Fetot and metals concentrations with strong acidic pH values (1.9–3.8). The δ34S and δ18O values of sulfate suggest that galena and/or sphalerite are the main source of sulfate and metals at the tailings site. The differences in sulfur isotope values (Δ34SSO4-sulfide) appear to be reflective of the extend of oxidation of monosulfides (e.g. galena) under two contrasting conditions of the tailings. The large sulfur isotope differences (Δ34SSO4-sulfides ~ -4.5 ± 0.2‰) imply incomplete oxidation of monosulfides to sulfate with aqueous geochemistry record of low sulfate, high metal and slightly acidic pH values. In contrast, the small Δ34SSO4-sulfide (<1 ± 0.2‰) values indicate the tailings site where complete oxidation of monosulfides to sulfate occurred resulting in acidic condition having with high sulfate, metal concentrations. The δ18OSO4 values were enriched than those of background water in tailings sites with the similar Δ18OSO4–H2O values (+8.9 to +11‰). Based on field data revealing enhanced galena and/or sphalerite oxidation relative to pyrite, the observed Δ18OSO4–H2O (avg., 9‰) values coupled with the relationship between δ34SSO4 values and sulfate concentration can be reflective of oxidation of monosulfides in contrast to disulfide minerals (e.g, pyrite) within polymetallic rich AMD systems

Distribution and Contamination of Heavy Metals in the Surface Sediments of Ambarli Port Area (Istanbul, Turkey)

The geochemical characteristics of the surface sediments of the Ambarli Port in Istanbul providing service for over 43.000 ships in the last decade are basically unknown. In this study, The distribution of total carbonate and metals in sediments was investigated and geochemical forms of the sediment-associated metals assessed to identify their possible sources. Metal contamination levels of sediments were evaluated with the aid of enrichment factor (EF) and index of geoaccumulation (I-geo) calculations. The degree of pollution in surface sediments yielded the I-geo ranking: Zn > Pb> Cr > Cu > As > Fe > Ni=Al >V, essentially not revealing pollution by Al, As, Fe, Ni and V. The highest Igeo and EF levels of Cr, Cu, Ni and Zn were found at the nearest station to Ambarli Port, indicating port activities as the source. Sequential selective leaching tests confirmed that As, Cr and Fe were mostly found in the residual phase, whereas Cu, Ni, Pb, V and Zn were mainly associated with the non-residual phase, possibly indicating the potentially higher mobility of the latter ions than those inherited from parent geological material. Based on statistical approaches, anthropogenic and natural geological factors were identified controlling the heavy metal variability in the sediments. This research is the first of its kind ever carried out in the Ambarli Port Area of Turkey

Evaluation of Contamination by Selected Elements in a Turkish Port

Enrichment factor and geoaccumulation index analyses revealed significant anthropogenic pollution by Al, As, Cu, La, Mo, Pb, Se, and Zn in the surface sediments of cores from Ambarli Port Area, whereas Ba, Fe, Ni, Sr in all sediments could be considered to be derived from pollution-free sources. Pb-210 dating shows deposition in the upper 2 cm between 1979 and 2009, indicating anthropogenic contamination of Al, As, Cu, La, Mo, Pb, Se, and Zn in sediments. As, Cr, Cu, Pb, and Zn in the upper parts may occasionally have reached toxic biological levels. The toxicity order for benthic organisms was Ni>Cr>As>Zn>Cu>Pb

Biogeochemistry of Balikesir Balya Pb-Zn Mine Tailings Site and Its Effect On Generation of Acid Mine Drainage

Biogeochemical characteristsics of Balikesir-Balya Pb-Zn Mine Waste site, known as the oldest and largest mine tailing site in Turkey, and its influence on generation of acid mine drainage was investigated by geochemical, molecular and microbiological approach. The oxidation of sulfide rich rocks and waste, mostly left over from Balya Pb-Zn mining activities, is generating acidic water with low pH (2.7), and contributing to metal contamination containing up to 1.88 mg/L Pb, 24 mg/L Zn, 2.5 mg/L As ve 17 mg/L Cu. Geochemical and molecular/microbiological analysis on mine waste, sediment and water samples (acidic, surface) show that acidic surface waters generated from sulfide weathering are principal pathways for mobility and redistribution of environmentally important elements into the environments. Based on cultivation based microbiological analysis carried out on acidic ponds developed around and in Balya Mine waste sites, the mean acidofilic sulfur oxidizing bacteria (aSOB) and acidophilic iron oxidizing bacteria were determined as 8.4x10(8)cell/ml ve 9.6x10(7) cell/ml, respectively. The relatively low values for surface water of Maden creek, where mine wastes reach, were determined as 3.8x10(6) cell/ml ve 5.7x10(3) cell/ml, respectively. Molecular analysis of 16S rDNA gene sequences from acidic sediment and sediment from Maden Creek show the dominance of S and Fe-oxidizing prokaryotes belonging to Acidithiobacillus spp. genus in the primary drainage communities. Relatively small populations of Sulfobacillus spp. were also determined. Moreover, species belong to Thiobacillus spp. and Thiovirga spp. genus were only determined on the sediment samples from Maden creek with low acidity relative to acidic sediment. These sulfur oxidizer indicates a dynamic microbial population which adapt to changing geochemical conditions. Identification of Fe oxidizer and reducer along with Jarosite, plumbojarosite and goethite in the sediments of acidic ponds indicate significance of microbial Fe cycle governing mobilization and redistribution of the metals in the waste site. Overall, it is shown that microorganisms regulating S and Fe cycle in Balya mine waste site is the key factors controlling generation and chemistry of acidic drainage water

Kinetic oxygen isotope effects during dissimilatory sulfate reduction: A combined theoretical and experimental approach

Kinetic isotope effects related to the breaking of chemical bonds drive sulfur isotope fractionation during dissimilatory sulfate reduction (DSR), whereas oxygen isotope fractionation during DSR is dominated by exchange between intercellular sulfur intermediates and water. We use a simplified biochemical model for DSR to explore how a kinetic oxygen isotope effect may be expressed. We then explore these relationships in light of evolving sulfur and oxygen isotope compositions ([delta]34SSO4 and [delta]18OSO4) during batch culture growth of twelve strains of sulfate-reducing bacteria. Cultured under conditions to optimize growth and with identical [delta]18OH2O and initial [delta]18OSO4, all strains show 34S enrichment, whereas only six strains show significant 18O enrichment. The remaining six show no (or minimal) change in [delta]18OSO4 over the growth of the bacteria. We use these experimental and theoretical results to address three questions: (i) which sulfur intermediates exchange oxygen isotopes with water, (ii) what is the kinetic oxygen isotope effect related to the reduction of adenosine phosphosulfate (APS) to sulfite (SO32-), (iii) does a kinetic oxygen isotope effect impact the apparent oxygen isotope equilibrium values? We conclude that oxygen isotope exchange between water and a sulfur intermediate likely occurs downstream of APS and that our data constrain the kinetic oxygen isotope fractionation for the reduction of APS to sulfite to be smaller than 4[per mille sign]. This small oxygen isotope effect impacts the apparent oxygen isotope equilibrium as controlled by the extent to which APS reduction is rate-limiting