Hydrothermal systems on active volcanoes can be studied through characterization of the emitted fluids and surface discharges using major element and isotopic compositions of fumaroles and thermal springs within the volcanic area. This thesis aims at understanding the geochemistry of the existing hydrothermal systems of Kanlaon, Biliran and Bulusan volcanoes in the Philippines and the contribution of magma degassing in the formation of fluids circulating within the hydrothermal system. This study also aims at improving the geochemical monitoring program of PHIVOLCS by suggesting parameters to use in evaluating the volcano’s activity and their evolution that may lead to volcanic unrest.Kanlaon volcano’s extensive hydrothermal system evolved into two distinct hydrothermal systems independent of each other. A mature hydrothermal system represented by Pataan thermal area is characterized by neutral Na + K chloride (bicarbonate) fluids and an immature system, represented by Hagdan is characterized by the presence of acid-sulfate waters. Chemical and isotopic analyses were performed on thermals waters to classify the samples that are linked to the existence of these two hydrothermal systems. Using Cl-SO4-HCO3 relative abundances, Kanlaon’s thermal waters are classified as acid sulfate, acid sulfate-chloride, neutral chloride, and neutral bicarbonate waters. The linear trend formed by Na + K and Cl of Pataan and Mambucal samples can be explained by groundwater/meteoric dilution. This is consistent with the light sulfur isotopic signatures between δ34S = -3.4 ‰ and +1.2 ‰ of the mature hydrothermal system. This implies that the origin of sulfur is linked to the surficial oxidation of H2S. In contrast, the immature hydrothermal system shows significantly heavier sulfur isotopic composition (δ34S = +8.2 ‰), which indicates that sulfur may have originated from the disproportionation of magmatic SO2 or from the fractionation between hydrothermal sulfate and sulfide (SO42-/H2S) pairs that have achieved isotopic equilibrium.On Biliran Volcano, the area of Vulcan thermal grounds exhibits the greatest thermal activity. Thermal waters of Biliran are classified into 6 types based on their geochemistry and location on the ground. Location 1 is composed of summit springs and location 2-6 are springs found along the periphery of the volcano with varying distances from the summit springs. Immature waters are discharging from the springs located at the summit. These are the acid sulfate-chloride waters. The high concentration of SO42- and Cl- is a clear indication of the presence of magmatic HCl, H2S, and SO2. The high δ34S (+14.7 ‰ to +26.6 ‰) values suggest that these fluids were formed from the disproportionation of magmatic SO2. The acidity of the summit springs is coming from the HCl which is a contribution from the degassed magma at depth. Mature neutral (SO42- - HCO3-) Cl springs are found away from the summit moving towards the margins of the neutralization zone. Neutral Cl fluids evolved from progressive neutralization of previously acidic fluid by water-rock interaction that migrated laterally and emerged as bicarbonate waters in the periphery of the volcano. Mt. Bulusan hydrothermal system is complex and tends to show the signature of a deep neutral Cl fluid. Based on Cl and SO42-, there are two groups of springs and these are found in two different locations. Type I springs are located on Mt. Bulusan close to the crater. The predominance of HCO3- and SO42- can be associated with shallow interactions and processes (i.e. boiling of hydrothermal fluids producing steam) that modify the fluid of meteoric in origin. Major gases such as CO2(g) and H2S(g) are incorporated in the groundwater via condensation. Type II springs are located on the periphery of the volcano, far from the location of Type I springs. These springs are characterized by the presence of Cl- and HCO3- ions at concentration levels greater than SO42- concentrations. The low solubility of CO2 allows the gas phase to be transported over long distances and converted to HCO3-. The origin of Type II fluids can either be through adsorption of CO2-bearing gases, or condensation of CO2-rich geothermal steam. The proximity of one Type II spring to sea level can have a bearing on the origin of Cl- in the fluids, but the fact that all Cl- composition of these springs are quite uniform, this means that the chloride must have come from one source and that it is highly unlikely to receive any contribution from seawater. This is also supported by the Cl/B and Cl/Li composition of Type II springs. Mt. Bulusan does not have ‘pure’ neutral chloride water signature but rather a mixture of neutral Cl waters and HCO3-rich waters. / Le travail de thèse est consacré à l’étude de systèmes hydrothermaux de volcans actifs qui ont été caractérisés grâce à l’étude géochimique (éléments majeurs et composition isotopique) des fluides hydrothermaux émis en surface de zones volcaniques. L’objectif principal de la thèse est l’interprétation de la composition géochimique des fluides hydrothermaux présents dans 3 systèmes actifs :les volcans Kanlaon, Biliran et Bulusan aux Philippines. Cette étude a également pour but d’améliorer le programme de monitoring de l’activité volcanique du PHIVOLCS (Philippine Institute of Volcanology and Seismology) en proposant des paramètres géochimiques utiles à l’évaluation de l’état d’activité d’un volcan et qui peuvent également fournir de signaux précurseurs d’une activité éruptive. Dans le cas du Volcan Kanlaon, la présence de deux systèmes hydrothermaux distincts a été mise en évidence grâce à l’analyse géochimique et isotopique des eaux thermales présentes dans le massif volcanique. Un système hydrothermal « mature » caractérisé par des fluides neutres chlorures (Na+K/Cl) est présent sous la zone hydrothermale de Pataan. Le deuxième système hydrothermal, situé dans la zone de Hagdan, présente au contraire des propriétés d’un système « immature » dominé par des fluides de type acide sulfate. En comparant les abondances relatives en Cl-SO4-HCO3, différents types de composition de sources thermales sont observées :acide sulfate, acide sulfate-chlorure, neutre chlorure et neutre bicarbonate. La corrélation linéaire qui existe entre les alcalins (Na+K) et les chlorures dans les échantillons de Pataan et de Mambucal suggère une origine identique et un processus de simple dilution par des eaux d’origine météoritique. D’autre part, la signature isotopique des sulfates à Mambucal avec une gamme de valeurs de δ34S entre -3.4 ‰ et +1.2 ‰ est typique de l’oxydation à proximité de la surface de l’H2S et tend à confirmer le caractère « mature » du système hydrothermal. La signature isotopique contrastée des sulfates de Hagdan avec un δ34S = +8.2 ‰ suggère que l’origine du soufre dans ce système « immature » pourrait être liée soit à la disproportionation du SO2 d’origine magmatique soit résulté d’un fractionnement isotopique à l’équilibre au niveau du sytème hydrothermal de la paire SO42-/H2S.Dans le cas du volcan Biliran, l’activité hydrothermal principale est située dans la zone sommitale de Vulcan. 6 types de composition géochimique différents ont été mis en évidence. Dans la zone sommitale de l’édifice volcanique, des eaux « immatures » de type acide sulfate-chlorure ont été identifiées. Les concentrations élevées en SO42- et Cl- suggèrent une contribution magmatique et la présence de HCl, H2S and SO2 émis par le dégazage d’une intrusion magmatique superficielle. Les valeurs élevées en δ34S (+14.7 ‰ à +26.6 ‰) suggèrent clairement que les sulfates proviennent de la réaction de disproportionation de SO2 d’origine magmatique. D’autre part, les valeurs d’acidité de ces sources sont nettement corrélées à l’abondance des chlorures et donc à la contribution d’HCl gazeux d’origine magmatique. En périphérie de la zone sommitale, les sources chaudes sont caractérisées par des eaux « matures » de type (SO42- - HCO3-) + Cl- dont l’acidité est largement neutralisée. Des fluides neutre chlorures provenant de la neutralisation progressive de fluides acides par interaction avec les roches encaissantes et enrichis en bicarbonates sont également présents dans les zones périphériques du volcan Biliran.Le système hydrothermal du Mt. Bulusan est complexe mais tend à révéler la présence d’un réservoir profond de composition neutre chlorure. Deux groupes de sources chaudes distincts sont présents dans deux zones distinctes de l’édifice volcanique. Sur base des compositions en Cl et SO42-, deux groupes distincts de sources chaudes ont été observées. Le type I, localisé à proximité du cratère du Bulusan, est caractérisé par la prédominance de HCO3- et SO42- et pourrait résulter de la condensation et dissolution de vapeurs (H20(g), CO2(g) et H2S(g)) essentiellement hydrothermales par des eaux superficielles d’origine météoritique. Le type II, observé beaucoup plus en périphérie de l’édifice volcanique, se distingue par l’abondance des ions Cl- et HCO3- qui dominent largement les concentrations en SO42-. L’origine des sources chaudes de type II est liée à la condensation/dissolution de vapeurs hydrothermales riches en gaz carbonique, le CO2 ayant, en raison de sa plus faible réactivité chimique, la faculté de diffuser latéralement sur de longue distance au sein d’un édifice volcanique. La proximité de certaines sources de type II avec la mer tend à suggérer une origine marine pour le chlore. Cependant, le même type II est également observé à grande distance de la mer où une contribution marine est difficilement envisageable. D’autre part, les compositions relatives en Cl/B and Cl/Li des sources de type II ne semblent pas compatibles avec une origine marine. Aucune composition de fluide « mature » de type neutre chlorure n’a été observée, l’origine des fluides de type II pourrait cependant résulter d’un mélange entre des eaux enrichies en HCO3- et des eaux neutres chlorures. / Doctorat en Sciences / info:eu-repo/semantics/nonPublished

<p> S^32/S^34 ratios have been determined between some coexisting sulfides from the Heath Steele B-1 orebody and five other stratiform deposits in the Bathurst-Newcastle area, New Brunswick, and in crushed ore samples and pyrites from three across deposit profiles in the B-1 orebody. Zn, Cu, Pb and Ag abundances have been established across the orebody. Fractionations of S^32/S^34 ratios between coexisting sulfides have been determined in heating experiments at temperatures of 350 to 500°C and isotope effects measured in aqueous precipitation and exchange experiments at 25°C. S^32/S^34 fractionations between given coexisting sulfides from all the sulfide deposits are found to show only small variations. Isotope exchange is generally rapid in dry sulfide systems. Metal sulfides in aqueous solutions are slightly enriched in S^32 relative to the H2S with which they precipitate or communicate. It is concluded that the sulfide deposits have been regionally metamorphosed. The origins that have been proposed for the deposits so far are discussed and a model is suggested to explain the sulfur isotope and base metal abundances in the B-1 orebody.</p> / Thesis / Doctor of Philosophy (PhD)

This thesis makes several contributions to improve our understanding of the Neoproterozoic Paleobiology. In chapter 1, a comprehensive quantitative analysis of the Ediacara fossils indicates that the oldest Ediacara assemblage "the Avalon assemblage" already encompassed the full range of Ediacara morphospace. A comparable morphospace range was occupied by the subsequent White Sea and Nama assemblages, although it was populated differently. In contrast, taxonomic richness increased in the White Sea assemblage and declined in the Nama assemblage. The Avalon morphospace expansion mirrors the Cambrian explosion, and both may reflect similar underlying mechanisms. Chapter 2 describes problematic macrofossils collected from the Neoproterozoic slate of the upper Zhengmuguan Formation in North China and sandstone of the Zhoujieshan Formation in Chaidam. Some of these fossils were previously interpreted as animal traces. Our study of these fossils recognizes four genera and five species. None of these taxa can be interpreted as animal traces. Instead, they are problematic body fossils of unresolved phylogenetic affinities. Chapter 3 reports stable isotopes of the Zhamoketi cap dolostone atop the Tereeken diamictite in the Quruqtagh area, eastern Chinese Tianshan. Our new data indicate that carbonate associated sulfate (CAS) abundance decreases rapidly in the basal cap dolostone and δ34SCAS composition varies between +9â ° and +15â ° in the lower 2.5 m. In the overlying interval, CAS abundance remains low while δ34SCAS rises ~5â ° and varies more widely between +10â ° and +21â °. δ34Spy is typically greater than δ34SCAS measured from the same samples. We propose that CAS and pyrite were derived from two isotopically distinct reservoirs in a chemically stratified basin. Chapter 4 studies δ13C, δ18O, δ34SCAS, and δ34Spy of the Zhoujieshan cap carbonate that overlies the Ediacaran Hongtiegou glaciation. The Zhoujieshan cap dolostone shows positive δ13C values (0 â 1.7â °). δ34SCAS shows rapid stratigraphic variations from +13.9 to +24.1â °, probably due to relatively low oceanic sulfate concentrations. δ34Spy shows a steady stratigraphic trend. Thus, the δ34SCAS and δ34Spy trends are decoupled from each other. The decoupling of δ34SCAS and δ34Spy trends suggests that CAS and pyrite were derived from different sulfur pools, which were probably due to the postglacial basin stratification. / Ph. D.

In order to understand the response of authigenic minerals to the gas hydrate geo-system, various authigenic pyrites were picked out under Zeiss Microscope and their S isotopes were analyzed later from 652 sediments samples at intervals of about 1.5m recovered from all 5 sites of Integrated Ocean Drilling Program (IODP) Expedition 311 on Cascadia Margin, northeastern Pacific. SEM photos of picked pyrites exhibit various aggregation features mainly in forms of strawberry, pillar/rod and dumbbell in sizes from 200 m to 1000m. Typical cubic pyrite crystals could be seen under smaller scale SEM photos. Most δ34S values in Site U1325 at the west deeper water location of IODP 311 show negative values low to -33.964‰ CDT, distinctly contrasted to the δ34S in Site U1329 at the east shallower location having much more positive values up to 28.29‰ CDT. At the cold venting position assigned as Site U1328 the δ34S values show strong negative values in the upper part of sediments column above 135 mbsf (meter below sea floor), increasing gradually with the depth from -35.83‰ CDT to -1.32‰ CDT, and then display many positive excursions up to 32.49‰ CDT below 135 mbsf, which is significantly distinguished from the values in nearby non-cold venting Site U1327 having much less positive excursions in the lower part of column below 110 mbsf. In all sites a general negative δ34S excursion occur in the upper part of sediments columns above 30~35 mbsf except in Site U1328 having more depth, indicating the potential current sulfate methane interface (SMI) activity zones. Distinct positive δ34S excursions up to the highest δ34S value 53.65‰ CDT from strawberry pyrites aggregations might indicate that sulfide products by AOM probably inherit completely the sulfate having high δ34S value and no sulfate was left after AOM at a high methane flux under gas hydrate geological background.

The Silver Hart property is a high grade silver-lead-zinc deposit consisting of polymetallic vein style, manto (carbonate replacement) style, and skarn type mineralization. Host rock consists of calcareous and non-calcareous sediments of the Cassiar Platform, mainly biotite schists, limestone units, and the monzogranite unit of the Cassiar Batholith. Bulk geochemistry shows that silver concentrations are closely related to copper and antimony values, suggesting freibergite, a silver-rich endmember of tetrahedrite, is the dominant silver mineral. EPMA (microprobe) analyses identified 6 silver minerals present; silver-bearing anglesite, freibergite, diaphorite, stephanite, pyrargyrite, and silver substitution in galena. Sulfur isotope analyses of galena gave an average δ34S of 6.9‰ vs VCDT, indicating a mixed mineralizing fluid source. Metal zoning patterns indicates that there is a thermal gradient across the main vein from hottest in the south-west, above the monzogranite intrusion, to coolest in the north-east. Microprobe analyses of freibergite indicates initial ore-forming fluid temperatures were between 250°C - 350°C, with subsequent cooler mineralization fluids of 170°C - 200°C.

No description available.

Em ambientes poluídos como a região metropolitana de São Paulo é imprescindível o conhecimento da natureza da poluição para que sejam estabelecidos procedimentos de minimização ou de controle das emissões. O estudo da poluição atmosférica já vem sendo realizado há muitos anos, sendo os componentes inorgânicos estudados a partir da determinação em amostras coletadas em filtros, soluções, entre outros meios. Neste trabalho é apresentado um método de determinação da razão isotópica de enxofre utilizando a técnica da Espectrometria de Massas com Plasma de Argônio como fonte de íons. O uso de um espectrômetro de massas de dupla focalização com fonte de íons por plasma de argônio, HR-ICPMS, o qual atinge resoluções (m/&#916;m) de até 8000, permitiu a resolução dos pfcoS dos isótopos 32S e 34S das interferência isobáricas mais comuns e/ou intensas, assim as medições foram realizadas utilizando-se diretamente as m/z dos isótopos do enxofre: A discriminação de massa foi avaliada analisando-se o material de referência NIST 8555 Sulfeto de Prata. A discriminação de massa em elementos leves como é o caso do enxofre é mais acentuada do que para os mais pesados. Assim, uma solução do material de referência era analisada a cada seqüência de 5 ou 6 soluções das amostras. A razão isotópica do enxofre foi determinada em amostras de ar atmosférico coletadas em Sâo Paulo, Ilha Rei George; na Península Antártica e diretamente do escapamento de um carro movido a gasolina e a diesel, utilizando-se um amostrador de grandes volumes e um conjunto de filtros composto de: um filtro de fibra de vidro para a coleta da fração grossa seguido de dois filtros de celulose impregnados com uma mistura de KOH e trietanolamina para a coleta do SO2 e sua oxidação a SO42-. Dois procedimentos de extração dos compostos de enxofre foram utilizados: uma somente com água e outra mais enérgica com ácido nítrico em forno de microondas. Os resultados obtidos indícaram que os dois procedimentos de extração resultam em soluções com composição isotópica diferentes. Além disso, a razão isotópica entre as soluções provenientes dos filtros de fibra de vidro e de celulose são também diferentes. Provavelmente, devido ao fracionamento existente em função da forma química do enxofre presente preferencialmente numa fração ou noutra. A análise quantitativa dos metais revelou uma presença de Fe em concentrações altas (5000-20000 ng/m3), enquanto que os demais (Mn, Cu, Cr, Ni, V, Sr, Cd, Co, Nd, Gd, Ir, Rh, Zr, Re e Ag) estavam presentes em concentrações mais baixas (< 300 ng/m3). Pelas características da amostragem, o Fe foi associado à ressuspensão do solo. O Nd, Gd, Ir, Rh, Re e Ag puderam ser tanto associados à ressuspensão do solo quanto à emissões por automóveis. O Mn, Cu, Cr, Ni, V e Sr foram associados à emissões devido à queima de combustíveis fósseis. / Polluted areas like the Great São Paulo nave a compltex pollution composition. The knowledge of this composition is essential in order to minimize or controt tne dífferent sources. Several atmospheric pollution studies have been done analyzing the inorganic fraction in samples collected in filters, solutions and other media. In this study, the sulfur isotopic ratio determination by using the mass spectrometry with an argon plasma as a source of ions is presented. A double focusing sector field mass spectrometer with an argon plasma, HR-ICPMS, was used. Since 8000 resolution (m/&#916;m} can be achieved, the 32S and 34S sulfur isotopes can be directly measured with no interferences from the common isobaric interferences (oxygen compounds). Tne isotopic ratio was determined in materials collected by using a high volume sampler. These samples were collected in São Paulo, in the King George Island; Antarctic and directly from the gases exhaust of agasoline and diesel vehicles. Two different filters were used : an external glass fiber filter was used to collect the gross fraction followed by two KOH-Triethanolamine impregnated cellulose filter to collect S)2. Two extraction procedures were used. The first one is an energetic extraction with nitric acid and micro-wave heating and the second one only with water being the soluble sulfur compounds extracted from the filters after had left 24 hours in a beaker with water. Mass discrimination was evaluated by analyzing the NlST 8555 Silver Sulphide Reference Material. As the mass discrimination is more prominent in light elements, the reference material solution was analyzed within a sequence of 5 or 6 samples. The results indicated dífferent isotopic ratio between the solutions obtained with these two extraction procedures. Different isotopic ratios were also observed in the sulfur isotopic composition in the gross and the fine fraction. This is probably due to different sulfur species present preferentially in a given fraction. The quantitative analyses of metals revealed a high Fe concentration (5000-20000 ng/m3) and lower concentrations (<300 ng/m3) to the others (Mn, Cu, Cr, Ní, V, Sr, Co, Co, Ncf, Go, Ir, Rh, Zr, Re and Ag). lron was associated to the soil dust. Neodymium, Gd, Ir, Rh, Re and Ag were associated to the soil dust and to the vehicles emissions. Manganese, Cu, Cr, Ni, V and Sr were associated to the vehicles emissions.

Em ambientes poluídos como a região metropolitana de São Paulo é imprescindível o conhecimento da natureza da poluição para que sejam estabelecidos procedimentos de minimização ou de controle das emissões. O estudo da poluição atmosférica já vem sendo realizado há muitos anos, sendo os componentes inorgânicos estudados a partir da determinação em amostras coletadas em filtros, soluções, entre outros meios. Neste trabalho é apresentado um método de determinação da razão isotópica de enxofre utilizando a técnica da Espectrometria de Massas com Plasma de Argônio como fonte de íons. O uso de um espectrômetro de massas de dupla focalização com fonte de íons por plasma de argônio, HR-ICPMS, o qual atinge resoluções (m/&#916;m) de até 8000, permitiu a resolução dos pfcoS dos isótopos 32S e 34S das interferência isobáricas mais comuns e/ou intensas, assim as medições foram realizadas utilizando-se diretamente as m/z dos isótopos do enxofre: A discriminação de massa foi avaliada analisando-se o material de referência NIST 8555 Sulfeto de Prata. A discriminação de massa em elementos leves como é o caso do enxofre é mais acentuada do que para os mais pesados. Assim, uma solução do material de referência era analisada a cada seqüência de 5 ou 6 soluções das amostras. A razão isotópica do enxofre foi determinada em amostras de ar atmosférico coletadas em Sâo Paulo, Ilha Rei George; na Península Antártica e diretamente do escapamento de um carro movido a gasolina e a diesel, utilizando-se um amostrador de grandes volumes e um conjunto de filtros composto de: um filtro de fibra de vidro para a coleta da fração grossa seguido de dois filtros de celulose impregnados com uma mistura de KOH e trietanolamina para a coleta do SO2 e sua oxidação a SO42-. Dois procedimentos de extração dos compostos de enxofre foram utilizados: uma somente com água e outra mais enérgica com ácido nítrico em forno de microondas. Os resultados obtidos indícaram que os dois procedimentos de extração resultam em soluções com composição isotópica diferentes. Além disso, a razão isotópica entre as soluções provenientes dos filtros de fibra de vidro e de celulose são também diferentes. Provavelmente, devido ao fracionamento existente em função da forma química do enxofre presente preferencialmente numa fração ou noutra. A análise quantitativa dos metais revelou uma presença de Fe em concentrações altas (5000-20000 ng/m3), enquanto que os demais (Mn, Cu, Cr, Ni, V, Sr, Cd, Co, Nd, Gd, Ir, Rh, Zr, Re e Ag) estavam presentes em concentrações mais baixas (< 300 ng/m3). Pelas características da amostragem, o Fe foi associado à ressuspensão do solo. O Nd, Gd, Ir, Rh, Re e Ag puderam ser tanto associados à ressuspensão do solo quanto à emissões por automóveis. O Mn, Cu, Cr, Ni, V e Sr foram associados à emissões devido à queima de combustíveis fósseis. / Polluted areas like the Great São Paulo nave a compltex pollution composition. The knowledge of this composition is essential in order to minimize or controt tne dífferent sources. Several atmospheric pollution studies have been done analyzing the inorganic fraction in samples collected in filters, solutions and other media. In this study, the sulfur isotopic ratio determination by using the mass spectrometry with an argon plasma as a source of ions is presented. A double focusing sector field mass spectrometer with an argon plasma, HR-ICPMS, was used. Since 8000 resolution (m/&#916;m} can be achieved, the 32S and 34S sulfur isotopes can be directly measured with no interferences from the common isobaric interferences (oxygen compounds). Tne isotopic ratio was determined in materials collected by using a high volume sampler. These samples were collected in São Paulo, in the King George Island; Antarctic and directly from the gases exhaust of agasoline and diesel vehicles. Two different filters were used : an external glass fiber filter was used to collect the gross fraction followed by two KOH-Triethanolamine impregnated cellulose filter to collect S)2. Two extraction procedures were used. The first one is an energetic extraction with nitric acid and micro-wave heating and the second one only with water being the soluble sulfur compounds extracted from the filters after had left 24 hours in a beaker with water. Mass discrimination was evaluated by analyzing the NlST 8555 Silver Sulphide Reference Material. As the mass discrimination is more prominent in light elements, the reference material solution was analyzed within a sequence of 5 or 6 samples. The results indicated dífferent isotopic ratio between the solutions obtained with these two extraction procedures. Different isotopic ratios were also observed in the sulfur isotopic composition in the gross and the fine fraction. This is probably due to different sulfur species present preferentially in a given fraction. The quantitative analyses of metals revealed a high Fe concentration (5000-20000 ng/m3) and lower concentrations (<300 ng/m3) to the others (Mn, Cu, Cr, Ní, V, Sr, Co, Co, Ncf, Go, Ir, Rh, Zr, Re and Ag). lron was associated to the soil dust. Neodymium, Gd, Ir, Rh, Re and Ag were associated to the soil dust and to the vehicles emissions. Manganese, Cu, Cr, Ni, V and Sr were associated to the vehicles emissions.

The purpose of this thesis was to experimentally investigate the influence of increasing sulfide concentrations on the 34S isotope enrichment in sulfate during dissimilatory sulfate reduction (DSR). Two independent batch culture experiments with different maximum sulfide concentrations of up to 20 mM in the first and up to 40 mM in the second experiment were conducted using the marine sulfate reducer Desulfobacter latus. A comparison of the results from both experiments revealed a distinct offset towards more positive δ34S(SO42-) values in the 'high-sulfide' experiment, compared to the 'low-sulfide' experiment. While a Rayleigh type fractionation model was able to match the slopes - i.e., enrichment factors - of both experiments, it failed to reproduce the proper y-axis intercept in the 'high-sulfide' experiment. I therefore propose a new fractionation model that allows for a backward flow of ambient H2S into the bacterial cell and a subsequent enzymatically mediated oxidation of H2S to sulfate. The new backward flow increases with elevated H2S concentrations and is described as a first order rate constant. Unlike a Rayleigh type fractionation model, my model explains the slope and y-intercept of both experiments with a single parameter set. The new model with H2S-reflux further suggests that it can be used to determine growth kinetic parameters like the half-saturation constant through δ34S measurements. These findings support the hypothesis of microbially mediated, bi-directional S-fluxes between oxidized and reduced sulfur species. Because the S-transport during DSR appears to be bi-directional, great care must be taken when evaluating culture experiments with a Rayleigh type fractionation model, owing to the fact that an evident S-backward flow violates the prerequisites for applying the Rayleigh model. A variable S-backward flow results in variable enrichment factors which increased from -11 (no H2S) to ≈-17 ‰ (40 mM of H2S) in my experiments. I show for the first time the significance of a bi-directional H2S transport across the cell membrane during DSR and its consequences for the 34S-isotope fractionation in sulfate.

The purpose of this thesis was to experimentally investigate the influence of increasing sulfide concentrations on the 34S isotope enrichment in sulfate during dissimilatory sulfate reduction (DSR). Two independent batch culture experiments with different maximum sulfide concentrations of up to 20 mM in the first and up to 40 mM in the second experiment were conducted using the marine sulfate reducer Desulfobacter latus. A comparison of the results from both experiments revealed a distinct offset towards more positive δ34S(SO42-) values in the 'high-sulfide' experiment, compared to the 'low-sulfide' experiment. While a Rayleigh type fractionation model was able to match the slopes - i.e., enrichment factors - of both experiments, it failed to reproduce the proper y-axis intercept in the 'high-sulfide' experiment. I therefore propose a new fractionation model that allows for a backward flow of ambient H2S into the bacterial cell and a subsequent enzymatically mediated oxidation of H2S to sulfate. The new backward flow increases with elevated H2S concentrations and is described as a first order rate constant. Unlike a Rayleigh type fractionation model, my model explains the slope and y-intercept of both experiments with a single parameter set. The new model with H2S-reflux further suggests that it can be used to determine growth kinetic parameters like the half-saturation constant through δ34S measurements. These findings support the hypothesis of microbially mediated, bi-directional S-fluxes between oxidized and reduced sulfur species. Because the S-transport during DSR appears to be bi-directional, great care must be taken when evaluating culture experiments with a Rayleigh type fractionation model, owing to the fact that an evident S-backward flow violates the prerequisites for applying the Rayleigh model. A variable S-backward flow results in variable enrichment factors which increased from -11 (no H2S) to ≈-17 ‰ (40 mM of H2S) in my experiments. I show for the first time the significance of a bi-directional H2S transport across the cell membrane during DSR and its consequences for the 34S-isotope fractionation in sulfate.