Nurgul Balci

Reproducing Authigenic Carbonate Precipitation in the Hypersaline Lake Acıgöl (Turkey) with Microbial Cultures

ABSTRACT In the present study, laboratory precipitation experiments using similar water chemistry and two different bacterial cultures from Lake Acıgöl sediments, a hypersaline lake in Turkey, were performed to reproduce mineral assemblages similar to those found in the lake. Two different bacterial cultures induce various calcium/magnesium carbonates precipitation under all the experimental conditions (solid vs. liquid): Hydromagnesite, dypingite, huntite, monohydrocalcite, and aragonite. The geochemical program PHREEQC was used to calculate the mineral saturation indexes in the cultures and in lake water. Carbonate mineral assemblages identified in the experiments seem to be independent of the type of microorganisms but rather controlled by the chemical composition and physical conditions of the media. The relative amounts of monohydrocalcite, hydromagnesite, and dypingite are controlled by varying sulfate concentration from 0 to 56 mM. This demonstrates a kinetic effect that could similarly affect the mineral assemblage in the lake. Also the spherical morphology of hydromagnesite points to growth of these minerals under partial inhibition in the brine under high concentrations of ions and organic polymers produced by the microbial communities. As reproduced by the culture experiments, the authigenic carbonate mineral assemblage of Lake Acıgöl most likely results from interplay of ionic composition of the brine and microbial effects.

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°) to sulfate in bacterial cultures in acidic conditions. Oxidation of tetrathionate by Acidithiobacillus thiooxidans 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 34S (ε34SSO4−S4O6) by +7.9‰, followed by a decrease to +1.4‰ over the experiment duration, with an average ε34SSO4−S4O6 of +3.5 ± 0.2‰ 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 (δ18OSO4) 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 (O2). During the oxidation of elemental sulfur, the product sulfate became depleted in 34S between −1.8 and 0‰ relative to the elemental sulfur with an average for ε34SSO4−S0 of −0.9 ± 0.2‰ and all the oxygen atoms in the sulfate derived from water with an average normal oxygen isotope fractionation (ε18OSO4−H2O) of −4.4‰. The differences observed in δ18OSO4 and the sulfur isotope composition of sulfate (δ34SSO4), 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.

Prediction of Acid Mine Drainage (AMD) and Metal Release Sources at the Küre Copper Mine Site, Kastamonu, NW Turkey

Waste and lithological rocks were subjected to aqueous leaching, acid base accounting (ABA), and net acid generation (NAG) tests, and detailed mineralogical investigations were conducted to predict acid mine drainage (AMD) formation at Turkey’s largest historical copper deposits. The field water chemistry from springs and seeps on the mine site were compared with the static and long term aqueous leaching test results. During the ABA, NAG and long term paste pH tests, ore rich and ore bearing wastes showed a paste pH <4, implying their acid generating nature. The relationship between net neutralization potential and acid producing potential revealed that waste rocks with a low sulfur content were generally low potential sources of AMD. Consistent with the static test results, aqueous leaching tests revealed that greater concentrations of Fe, Cu, Zn, Ni, Pb, Cd, Co and As were released from the wastes rich in pyrite. The test methods all generally agreed that the ore-rich wastes (O, P1C, P1D) were the main sources of AMD and metal contamination in the district.ZusammenfassungMineralhaltiger Abraum und Nebengesteine waren Gegenstand von wässrigen Eluatversuchen, Säure-Basen-Berechnungen (ABA) und Net Generation Tests (NAG) sowie detaillierter mineralogischer Untersuchungen, um Vorhersagen zur Bildung von säurehaltigen Bergbau-Abwässern (AMD) in der größten historischen Kupfer-Lagerstätte der Türkei zu treffen. Die Chemie der Oberflächenwässer von Quellen und der Sickerwässer aus dem Bergbau wurden mit den Ergebnissen der statischen und der Langzeit-Auswaschungstest verglichen. Während der ABA, NAG und der Langzeit-Paste-pH-Tests, zeigten erzreiche und Erz-führende Abfälle einen Paste-pH Wert <4, die auf ihre Säure produzierenden Eigenschaften schließen lassen. Die Beziehung zwischen dem Netto Neutralisationspotential (NNP) und dem Säure produzierenden Potential (APP) offenbarten, dass Abraum mit geringen Schwefelgehalten grundsätzlich eine Quelle mit geringem Potenzial für AMD ist. Übereinstimmend mit den statischen Testergebnissen und den Eluatversuchen in wässrigen Lösungen, zeigten die Ergebnisse dass größere Konzentrationen von FE, Cu, Zn, Ni, Pb, Cd, Co und As in pyritreichen Abfällen freigesetzt wurden. Alle Testmethoden stimmten darin überein, dass die erzreichen Abraummassen (0, P1C, P1D) die Hauptquellen für säurehaltige Abwasser (AMD) und Kontaminationen mit Metallen im Distrikt sind.ResumenLos residues y rocas litológicas se sometieron a ensayos de lixiviación acuosa, balance ácido/base (ABA) y de generación neta de ácido (NAG) e investigaciones mineralógicas detalladas se realizaron para predecir la formación de drenaje ácido de mina (AMD) en los mayores depósitos de cobre en Turquía. La química del agua de los manantiales y las filtraciones en el sitio de la mina se compararon con los resultados de la prueba de lixiviación acuosa a largo plazo y estática. En los ensayos ABA, NAG y de medida de pH a largo plazo, residuos ricos en mineral y el mineral mostraron un pH <4, lo que implica su naturaleza generadora de ácido. La relación entre el potencial neto de neutralización (NNP) y el potencial de producción de ácido (APP) mostraron que las rocas residuales con un bajo contenido en azufre fueron bajas fuentes potenciales de AMD. Coincidiendo con los resultados de los ensayos estáticos, los ensayos de lixiviación acuosa mostraron que las mayores concentraciones de Fe, Cu, Zn, Ni, Pb, Cd, Co y As fueron liberadas por los residuos ricos en pirita. Los métodos de ensayos coincidieron en que los residuos ricos en mineral (O, P1C, P1D) eran las principales fuentes de AMD y de contaminación con metales en el distrito.抽象采用淋滤、酸碱平衡(ABA)和净产酸能力(NAG)试验及矿物学分析的方法预测土耳其最大历史遗留铜矿废物及岩石的酸性矿山废水(AMD)形成。对比了野外泉水和渗水的水化学特征与静态及长期淋滤水试验结果。在ABA、NAG和长期糊状pH试验期间,富矿和含矿废物的糊状pH小于4,表明其产酸潜质。净中和潜力(NNP)与产酸潜力(APP)关系说明低硫废矿石为低潜力酸性废水(AMD)释放源。与静态试验结果一致,动态淋滤试验揭示富含黄铁矿废矿石的铁、铜、镍、镉、钴和砷淋释放浓度更大。由系列试验获得的一致结论是富矿废矿石(岩样O、P1C和P1D)为主要产酸源(AMD)和金属污染释放源。

Geochemical Characteristics of Sedimentary Manganese Deposit of Binkılıç, Trache Basin, Turkey

The Binkilic manganese deposit, occurring in the Congeria and Fish Series of the Oligocene in Thrace Basin, is associated with relatively rapid marine transgressions and regressions across older basement rock and is called as shallow-marine basin-margin deposit. The geochemical characteristics of the deposit were examined by means of major oxide, trace and rare elements (REE) contents and the origin of mineralization was discussed. The deposit contains lower Mn / Fe ratios than those of hydrothermal and sedimentary exhalative deposits. The concentrations of Ba, Co, Sr, Cu, Zn and Ni are closely related to the increase of manganese content and indicate the element’s nature in various manganese minerals. According to trace element spider diagram normalized to shale composite NA, the ore is clearly enriched in Sr, Ni while distinctly depleted in Rb. The chemical analysis results indicated that total REE contents of the samples are relatively low and the ratio of ΣLREE/ΣHREE shows a primary enrichment for LREE that has occurred during the Mn oxidation process. The increase in total LREE is mainly associated with the amount of terrigenous material that was transported in the depositional environment. The chondrite-normalized REE patterns are remarkably similar, yielding HREE-depleted curves with a small negative Ce and middle positive Eu anomalies and reflect their same origin of ore source. The Ce values and Ce/Ce* ratios show that the Binkilic deposit is mainly associated with the marine basin and the ore is formed in both anoxic and oxic conditions. The major oxide, trace element and REE assessments indicated that the Binkilic Mn deposit occurred as a diagenetic type of Mn deposit with terrigenous material addition, but some manganese oxides are related to the upwelling of reducing waters containing abundant organic matter and dissolved Mn to the shallow-marine areas.