Physical, Metabolic, and Energetic Investigations of Methane-Metabolizing Microbial Communities

Understanding the roles of microorganisms in environmental settings by linking phylogenetic identity to metabolic function is a key challenge in delineating their broad-scale impact and functional diversity throughout the biosphere. This work addresses and extends such questions in the context of marine methane seeps, which represent globally relevant conduits for an important greenhouse gas. Through the application and development of a range of culture-independent tools, novel habitats for methanotrophic microbial communities were identified, established settings were characterized in new ways, and potential past conditions amenable to methane-based metabolism were proposed. Biomass abundance and metabolic activity measures – both catabolic and anabolic – demonstrated that authigenic carbonates associated with seep environments retain methanotrophic activity, not only within high-flow seep settings but also in adjacent locations exhibiting no visual evidence of chemosynthetic communities. Across this newly extended habitat, microbial diversity surveys revealed archaeal assemblages that were shaped primarily by seepage activity level and bacterial assemblages influenced more substantially by physical substrate type. In order to reliably measure methane consumption rates in these and other methanotrophic settings, a novel method was developed that traces deuterium atoms from the methane substrate into aqueous medium and uses empirically established scaling factors linked to radiotracer rate techniques to arrive at absolute methane consumption values. Stable isotope probing metaproteomic investigations exposed an array of functional diversity both within and beyond methane oxidation- and sulfate reduction-linked metabolisms, identifying components of each proposed enzyme in both pathways. A core set of commonly occurring unannotated protein products was identified as promising targets for future biochemical investigation. Physicochemical and energetic principles governing anaerobic methane oxidation were incorporated into a reaction transport model that was applied to putative settings on ancient Mars. Many conditions enabled exergonic model reactions, marking the metabolism and its attendant biomarkers as potentially promising targets for future astrobiological investigations. This set of inter-related investigations targeting methane metabolism extends the known and potential habitat of methanotrophic microbial communities and provides a more detailed understanding of their activity and functional diversity.

Avaliação da corrosão microbiológica do aço carbono 1020 em água do mar sintética na presença de bactérias redutoras de sulfato

Bactérias redutoras de sulfato (BRS) possuem um papel importante na corrosão de ligas metálicas expostas em hábitats marinhos, óleos e solos úmidos. A redução do sulfato por estas bactérias resulta na produção de H2S, podendo influenciar os processos anódico e catódico na corrosão de materiais. Neste trabalho, o comportamento da corrosão microbiológica no aço carbono AISI 1020 foi avaliada em meio Postgate C, na presença e na ausência de BRS, as quais foram isoladas da camada de ferrugem presente numa tubulação submersa da Baía de Guanabara RJ. A taxa de corrosão e o comportamento eletroquímico do aço nas duas condições foram investigados através dos métodos de perda de massa e de polarização potenciodinâmica. A formação do biofilme e dos produtos de corrosão na superfície do aço foram observados por microscopia eletrônica de varredura (MEV) e por espectroscopia de energia dispersiva (EDS). Em complementação, foi realizada a quantificação das BRS (planctônicas e sésseis) pelo método do número mais provável (NMP). A presença de BRS no meio ocasionou o deslocamento do potencial de corrosão para valores mais negativos em todos os tempos de ensaio estudados, indicando um aumento no processo corrosivo. Nos ensaios de perda de massa, a taxa de corrosão do aço carbono foi maior na ausência de BRS, provavelmente devido à formação de um biofilme na superfície do metal nos ensaios com inóculo, e a uma menor tendência de haver corrosão generalizada neste tipo de meio. As micrografias de MEV revelaram a presença de agregado celular na superfície do aço carbono durante o experimento, e a presença de pites profundos após remoção do biofilme, mostrando prevalência deste tipo de corrosão. Com 35 dias de ensaio, a densidade de corrente de corrosão aumentou na presença de BRS

Desenvolvimento de metodologias para a determinação da atividade biogênica de bactérias redutoras de sulfato

A corrosão causada por H2S biogênico frequentemente resulta em danos extensos na indústria do petróleo. O presente trabalho avaliou parâmetros de crescimento microbiano e aplicou metodologias de determinação de sulfetos por técnicas espectrofotométrica na região da luz visível e radiorespirométrica para avaliação da atividade metabólica, correlacionando com a população de bactérias redutoras de sulfato, determinada através da técnica do Número Mais Provável (NMP). Amostras de água de formação e consórcio de BRS foram avaliadas através do arraste de sulfetos estáveis produzidos biogenicamente e quantificados por espectrofotometria. O cálculo das velocidades instantâneas e específicas de produção de sulfetos permitiu avaliar de que maneira alguns parâmetros de crescimento microbiano podem afetar o metabolismo das BRS. A detecção de concentrações traço de sulfetos biogênicos pode ser realizada através de ensaios radiorespirométricos. Para isto, diluições em série de água do mar sintética com três amostras distintas foram avaliadas. Os testes realizados indicam que o acréscimo do tempo de incubação de cultura microbiana anaeróbia mista contribuiu para o aumento das capacidades de redução de sulfato, assim como o aumento das fontes de carbono. Ambas as técnicas provaram ser um rápido teste para a detecção de sulfetos biogênicos, particularmente aqueles associados aos produtos de corrosão, sendo uma ferramenta muito útil para monitoração e controle de tanques de armazenamento de água e óleo, plataformas continentais de petróleo e diversos tipos de reservatórios. O presente trabalho prevê a continuidade dos experimentos, através de avaliação de um maior universo de amostras da indústria do petróleo e medições menos espaçadas da técnica espectrofotométrica, além da avaliação radiorespirométrica em modo contínuo, evitando os efeitos inibitórios do H2S

油气、微生物与砂岩型铀矿形成关系研究——以东胜铀矿床和钱家店铀矿床为例

Sandstone-type uranium deposits are frequently found close to oil fields or uraniferous sandstones contain bitumen or petroleum. However, few evidence has been presented to indicate the association of uranium mineralization with petroleum oxidation. Thus, Dongsheng uranium deposit in Ordos Basin and Qianjiadian deposit in Kailu Basin are taken for examples to solve the puzzle. Integration data from sedimentary petrology, mineralogy, race elements geochemistry, isotope geochemistry and organic geochemistry, the uranium and petroleum sources, and diagenetic paragenesis of the host sandstone are analyzed, and then the genetic relationship between microbes, petroleum and uranium deposits are discussed. The observation under microscope shows that the host sandstone samples from Middle Jurassic Zhiluo Formation in the Dongsheng deposit contained different kinds of metamorphic rock fragments, which should have been derived form outcrops north to this basin. The LREE/HREE ratios of gneiss and amphibolite sampled from outcrops were close to the highest and the lowest LREE/HREE ratios of the sandstones with well-compared chondrite-normalized REE patterns, respectively. So these results consistently indicated that parent rocks of sandstones were mainly contributed from these two kinds of metamorphic rocks. There was very high Th/U ratio for granite gneiss, which was a mainly potential U resource. Hydrocarbon inclusions and adsorbed hydrocarbons are observed under fluorescence microscope in the host sandstone of Dongsheng uranium deposit, suggesting that the sandstones may have been utilized as oil migration pathways. Based on biomarker parameters, it is indicated that the inclusion oils and adsorbed hydrocarbons were marginally mature to mature, and were derived from humic-sapropel type organic matter under poor reducing freshwater to semi-saline environment. The features are similar to those of organic matter extracted from Triassic sandstone and source rock, but are different from that of cretaceous sandstone. Thus, it can be concluded that the inclusion oils and adsorbed hydrocarbons were mainly derived from Triassic lacustrine facies source rock. Observation results under Scanning Electron Microscopy and Electron Microprobe with Energy Spectrum Analysis show that, in Dongsheng area, the main uranium ore mineral is coffinite. The coffinite is intimately intergrown or coexists with pyrite and calcite, thus, the solution during mineralization stage is inferred to be alkaline. The alkaline environment is not favored for uranium to be pre-concentrated by absorption, and then be reduced abiogenetically. δ34S of pyrite and δ13C of calcite indicate that pyrite was formed by bacterial sulfate reduction (BSR) and part of the carbon of calcite has been dirived from oxidation of petroleum, respectively. Additionally, petroleum is found biodegraded. All the lines of evidence consistently indicate that petroleum was involved in uranium mineralization. Coffinite with microbe-like structures is found in the high U sandstone samples and is composed of nanoparticles, indicating the coffinite is biogenic. The conclusion are also supportted by laboratory experiment studies, which have shown that SRB are capable of utilizing U(VI) as the preferred electron acceptor for respiration and reduce U(VI) to U(IV) directly, coupled the oxidaton of organic matter and sulfate reduction. Based on the research results mentioned above, in the Dongsheng area, coffinite is likely to have formed by mixing of brine containing petroleum derived from Triassic with uranium-bearing meteoric water from outcrops north to Ordos Basin. SRB utilize hydrocarbon as carbon source, and directly reduce U(VI) resulting in precipitation of coffinite. The product of metabolism, H2S and CO2, was precipitated as pyrite and calcite during mineralization stage. Petroleum in fluid inclusions and adsorbed type in host sandstone from Lower Cretaceous Yaojia Formation in Qianjiadian uranium deposit, Kailu Basin, are derived from Jurassic Jiufotang Formation in this basin and the uranium mineral consists mainly of pitchblende. The δ34S and δ13C values of pyrite and calcite during mineralization stage indicate SRB have likely degraded petroleum, which is similar to that of Dongsheng deposit. The alkaline environment as indicated by the diagenetic mineral assemblage calcite, Fe dolomite, pyrite and pitchblende deposit suggests that U ore in the Qiangjiajiadian has a similar origin, i.e., direct reduction by SRB. However, less part of pitchblende is intergrown with kaolinite, suggesting the solution during mineralization stage is acidic. The environment is favorable for U(VI) to be adsorded on quartz or other mineral, and then reduced by H2S produced by SRB. Thus, it can be concluded that U(VI) reduction with petroleum oxidation by SRB and other microbes is an important ore-forming mechanism in petroleum-related sandstone-type uranium deposits. The finding is significant in that it provides a theoretical basis for exploration of both uranium and petroleumr.

华南埃迪卡拉纪末期硅质岩和深海的氧化还原状态

A suit of cherts deposited in deep-ocean basin of South China during terminal Ediacaran and the beginning of Early Cambrian (about 550～540Ma). The origin of these cherts are controversial, and contrary standpoints exist for the redox state of the terminal Ediacaran deep-ocean because of poor study. In this paper, a detailed sedimentology, element and stable isotope geochemistry study were conducted for cherts of Liuchapo Formation in Anhua County, Hunan Province, Laobao Formation in Sanjiang County, Guangxi Province, and Piyuancun Formation in Xiuning County, Anhui Province. Some conclusions were drawn: (1) These cherts were mainly formed through chemical deposition of dissolved silica derived from chemical weathering in continent. Biological processes played a part in the cherts formation, however, the influence of hydrothermal fluids and detritus materials were trivial. (2) The terminal Ediacaran deep-ocean was anoxic and gradually oxidized. (3) Intense bacterial sulfate reduction decreased sulfate concentration in the ocean and the water column became euxinic during Ediacaran-Cambrian transition period. (4) Due to a high CO2 concentration in the terminal Ediacaran atmosphere, chemical weathering in continent dramatically increased and huge amounts of nutrimental material were transferred into ocean. The biota bloomed because of the nutrimental material. Degradation of huge amounts of organic matter maintained dissolved organic carbon reservoir in the ocean, and prolonged the deep-ocean anoxia.

湘西地区上震旦统上部－下寒武统底部黑色岩系沉积学及地球化学

Widespread black chert-shales occur in the Ediacaran-Cambrian(E-C) boundary successions along the flank of Yangtze Platform, South China, remarkable changes in sedimentology, geochemistry and biology were recorded. Although extensive studies were carried out upon this boundary succession, the origin of black chert-shales still remain controversial. This paper focuses on the E-C black chert-shales in western Hunan, South China, upon which detailed depositional and geochemical changes are documented, accordingly a depositional model for black chert-shales is proposed. Stratigraphic anatomy across the depositional strike demonstrates that the shallow-water Dengying dolostone along the platform margin sharply pass basinward into the Liuchapo chert successions, which indicate syndepositional extensional faulting at depth could have occurred along the platform margin. The deep-water Niutitang phosphorite-rich black shales are either underlain by the Dengying dolostones on the platform margin toward platform interior or directly by the Liuchaopo chert successions farther basinwards. By detailed investigation, silica chimneys are firsly identified approximately in the chert along platform margin; two types of silica chimneys, including mounded and splayed/funnelized chert(generally brecciated) bodies are further sorted out. The mounded chert are exitbited by domed or hummocky surfaces on the top and irregular spongy to digitiform internal fabrics; within the silica mounds, abundant original vesicles/voids and/or channels were mostly plugged by initial chalcedony, quartze crystals with minor dolomite and bladed barite crystals. Splayed/funnelized brecciated chert “intrusion” cross-cut the uppermost dolostones capping to the horizon underneath, and are directly overlain by the Niutitang phosphorite-rich black shales. Their similarities to the silica chimneys reported from the oceanic spreading centres suggest a similar origin responsible for these unique silica bodies which is also supported by the microthermonmetric data and element geochemistry. High P, Ba, Fe contents and positive correlation between Fe and TOC concentrations in the Niutitang black shales indicate a high palaeo-productivity in the Early Cambrian ocean. The low Th/U and the high V/Cr, V/Sc, V/(V+Ni) ratios in the black shales suggest an anoxic water condition during this interval. Furthermore, Positive Eu anomalies and high Ba contents in the sediments also imply a hydrothermal influence on the formation of Niutitang black shales. To better constrain the placement of deep-water successions straddling the E-C boundary and the timing of hydrothermal silica chimneys, sensitive high-resoluton ion microprobe(SHRIMP) U-Pb dating of zircon grains from tuffs within the chert succession of Liuchapo Formation at Ganziping was conducted and yields a weighted-mean 206Pb/238Pb age at 536.6±5.5Ma, younger than E-C boundary age(542.0±0.3Ma). This age combined with carbon isotopic data is then proposed to correspond to the U-Pb age of zircons(538.2±1.5Ma) from the Zhongyicun member of Meishucun Formation at Meishucun in eastern Yunna, thus, the E-C boundary in Gazngziping was placed between the Dengying formations and Liuchapo formatioms. therefore, the silica chimneys took place at the beginning of the Cambrian period. The temporal coincidence of silica chimneys and negative excursions of δ13C and δ34Spy pairs suggest hydrothermal activities were likely responsible for the isotopic changes. Under such a circumstance, vast amounts of greenhouse gases(CO2, CH4, H2S), with highly 13C-depleted carbon and 34S-depleted sulfur would be released into the ocean and atmosphere. A positive shift in δ34Scas and Δ34S values from the late Ediacaran to the Early Cambrian could be a reflection of enhanced bacterial sulfate reduction(BSR), strengthened by the intensified oceanic anoxia stimulated by hydrothermal activities. Based on the analyses of sedimentology and geochemistry, a model- “oceanic anoxia induced by hydrothermal–volcanic activies” was proposed to responsible for the formation of black chert-shales during this E-C transition. Under this case, hydrothermal-volcanic activies could release large large amount of greenhouse into atmosphere and metal micronutrients into the ocean, which may lead to global warming, stratified ocean, thereby a high palaeoproductivity; on the other hand, the massive releasing of reduced hydrothermal fluids with abundant H2S, could have in turn enhanced the ocean anoxia. All of these were favourable the for preservation of organic matter, and subsequent extensive deposition of black silica-shales.

流体地球化学：成因、流动和流体-岩石相互作用及塔里木盆地实例研究

Geofluid in sedimentary basins is related to petroleum generation, migration, accumulation and preservation, and is a topic of geological frontier. By integrating the multi-discipline methods of petroleum geochemistry, sedimentology, hydrogeology, petroleum geology and experimental geochemistry, the thesis has carried out experiments of microcline dissolution in solutions with organic acids, crude oil, brines with high total dissolved solids (TDS), and has dealt with Al distribution between the crude oil and the brines after the experiments. Cases for study includes Central Tarim, Hetianhe Gas Field and Kucha forland basin with data containing fluid chemistry and isotopic compositions, thin sections of sandstones and carbonates, homogenization temperatures and salinities of fluid inclusions, isotopic compositions of bulk rock and autigenic minerals. The aims are to elucidate fluid origin and flow in the three areas, effect of hydrocarbon emplacement on diagenesis, and to show occurrence of microbe-mediated, and thermochemical sulfate reduction in the Tarim Basin. Microcline dissolution experiments show that after 100 hour, part of the dissolved Al distributes in the crude oil, and the Al concentrations in the crude oil rise when organic acids are added. The result can be used to explain that most oilfield waters in the Tarim Basin are characterized by less than 3mg/L Al. Crude oil added to the solutions can enhance microcline dissolution, which is also observed in the case - Silurian sandstones with early crude oil emplacement in the Central Tarim. Al and Si have higher concentrations in the experiments of oxalic acid than of acetic acid under the same pH conditions, suggesting that there exist Al-oxalate and Si-oxalate complexes. Presence of acetate can enhance the activity of Ca and Al, but Al concentrations have not been increased significantly due to formation of small Al-acetate complex during the experiments. Relationships between δD and δ~(18)O in conjunction with chemistry of oilfield waters show that the waters are evaporated connate waters, which subsequently mixed with meteoric water, and were influenced by water-rock interactions such as salt dissolution, dolomitization of calcite, albitization of feldspar. In the Hetianhe Gas Field where salt dissolution took place, δD and δ~(18)O values can be used to trace nicely meteoric water recharge area and flow direction, but TDS can not. Part of the waters have high TDS but very light δD and δ~(18)O. When combined with paleo-topography, or fluid potentials, meteoric water is suggested to flow eastward in the Hetianhe Gas Field, which is the same with the Central Tarim. Whist in the Kuche forland basin, meteoric water may have permeated Cambrian-Ordovician strata. Relationship between ~(87)Sr/~(86)Sr and 1/Sr can be used to indicate migration and mixing of brines from carbonate strata (low ~(87)Sr/~(86)Sr ratio but high Sr content), clastic strata (high ~(87)Sr/~(86)Sr ratio but low Sr content) and crystalline basement (high ~(87)Sr/~(86)Sr ratio and heavy δ~(18)O value). Using this approach, it can be found that ~(87)Sr-depleted brine from Ordovician carbonates have migrated up to and mixed with ~(87)Sr-enriched waters from Silurian and Carboniferous sandstones, and that Silurian brines have mixed with meteoric water. In the Kuche forland basin, brines from the Cambrian and Ordovician carbonates have higher ~(87)Sr/~(86)Sr ratios than those from the overlying sandstones, when combined with chemistry, δ~(15)N and ~3He/~4He ratios of the coexisting natural gases, suggesting that the brines were derived from the basement. There exists some debate on the effect of hydrocarbon emplacement on mineral diagenesis. Case-study from Silurian sandstones in the Central Tarim show that quartz has kept overgrowing secondarily when oil saturation was decreased by meteoric water flushing subsequently to hydrocarbon emplacement. Silicon precipitates on the water-wet quartz surface, leading to decreased Si concentration close to the surface. A Si grads can result in Si diffusion, which supplies Si for quartz overgrowth. Hydrocarbon oxidation-sulfate reduction is an important type of organic-inorganic interaction. Not only can it make secondary alteration of hydrocarbons, but generate H_2S and CO_2 gases which can improve reservoir property. Thermochemical sulfate reduction took place at the temperatures more than 125 ℃ to 140 ℃ in the Cambrian-Ordovician carbonates, the products - H_2S and CO_2 gases migrated up to the Silurian, and precipitated as pyrite and calcite, respectively. The pyrite has an average δ~(34)S value close to those of Ordovician seawater and anhydrite, and calcite has δ~(13)C value as low as -21.5‰. In the Hetianhe Gas Field, sulfate reduction bacteria carried by meteoric water flowing eastward may have preferentially depleted ~(12)C of light hydrocarbon gases, and results in heavier δ~(13)C values of the residual hydrocarbon gases and higher molar CO_2 in the natural gases in the west than in the east. Coexisting pyrite has δ~(34)S values as low as -24.9‰.

Low-frequency electrical response to microbial induced sulfide precipitation

We investigated the sensitivity of low-frequency electrical measurements to microbe-induced metal sulfide precipitation. Three identical sand-packed monitoring columns were used; a geochemical column, an electrical column and a control column. In the first experiment, continuous upward flow of nutrients and metals in solution was established in each column. Cells of Desulfovibrio vulgaris (D. vulgaris) were injected into the center of the geochemical and electrical columns. Geochemical sampling and post-experiment destructive analysis showed that microbial induced sulfate reduction led to metal precipitation on bacteria cells, forming motile biominerals. Precipitation initially occurred in the injection zone, followed by chemotactic migration of D. vulgaris and ultimate accumulation around the nutrient source at the column base. Results from this experiment conducted with metals show (1) polarization anomalies, up to 14 mrad, develop at the bacteria injection and final accumulation areas, (2) the onset of polarization increase occurs concurrently with the onset of lactate consumption, (3) polarization profiles are similar to calculated profiles of the rate of lactate consumption, and (4) temporal changes in polarization and conduction correlate with a geometrical rearrangement of metal-coated bacterial cells. In a second experiment, the same biogeochemical conditions were established except that no metals were added to the flow solution. Polarization anomalies were absent when the experiment was replicated without metals in solution. We therefore attribute the polarization increase observed in the first experiment to a metal-fluid interfacial mechanism that develops as metal sulfides precipitate onto microbial cells and form biominerals. Temporal changes in polarization and conductivity reflect changes in (1) the amount of metal-fluid interfacial area, and (2) the amount of electronic conduction resulting from microbial growth, chemotactic movement and final coagulation. This polarization is correlated with the rate of microbial activity inferred from the lactate concentration gradient, probably via a common total metal surface area effect.

Geophysical imaging of stimulated microbial biomineralization

Understanding how microorganisms influence the physical and chemical properties of the subsurface is hindered by our inability to observe microbial dynamics in real time and with high spatial resolution. Here, we investigate the use of noninvasive geophysical methods to monitor biomineralization at the laboratory scale during stimulated sulfate reduction under dynamic flow conditions. Alterations in sediment characteristics resulting from microbe-mediated sulfide mineral precipitation were concomitant with changes in complex resistivity and acoustic wave propagation signatures. The sequestration of zinc and iron in insoluble sulfides led to alterations in the ability of the pore fluid to conduct electrical charge and of the saturated sediments to dissipate acoustic energy. These changes resulted directly from the nucleation, growth, and development of nanoparticulate precipitates along grain surfaces and within the pore space. Scanning and transmission electron microscopy (SEM and TEM) confirmed the sulfides to be associated with cell surfaces, with precipitates ranging from aggregates of individual 3-5 nm nanocrystals to larger assemblages of up to 10-20 m in diameter. Anomalies in the geophysical data reflected the distribution of mineral precipitates and biomass over space and time, with temporal variations in the signals corresponding to changes in the aggregation state of the nanocrystalline sulfides. These results suggest the potential for using geophysical techniques to image certain subsurface biogeochemical processes, such as those accompanying the bioremediation of metal-contaminated aquifers.

Oxygen and hydrogen sulfide concentration of Nootka Sound bottom water

Senior thesis written for Oceanography 445

Características geoquímicas de sedimentos del perfil Callao, Octubre 2008

Se determinó la tendencia y variabilidad vertical de las características geoquímicas de los sedimentos y del agua intersticial en los primeros 10 cm superficiales de dos testigos de Callao, colectados en dos estaciones del perfil Callao, durante el Crucero Miniox BIC Olaya 0810: (1) E-2, a 8 mn de la costa y 98 m de profundidad, donde la materia orgánica presentó un amplio rango de variabilidad (4,75% a 56,34%) y una tendencia al incremento con la profundización del perfil vertical, al existir condiciones geoquímicas que favorecen una mayor preservación de la materia orgánica y una lenta remineralización; y (2) E-5, a 30 mn de la costa y 178 m de profundidad, donde la materia orgánica presentó una distribución más homogénea en el perfil vertical (30,72% a 36,17%). Las elevadas correlaciones (r > 0,7) de la materia orgánica total con el carbono orgánico total, así como con los fosfatos y los silicatos en sedimentos superficiales indican que la materia orgánica gobierna parcialmente las concentraciones de carbono y fósforo. La variabilidad en la conducta de distribución de las concentraciones de metales Redox sensitivos en los sedimentos recientes, está asociada a condiciones anóxicas y a la intensa actividad sulfato reductora característica en la zona de estudio.

Insights into redox cycling of sulfur and iron in peatlands using high-resolution diffusive equilibrium thin film (DET) gel probe sampling

High spatial resolution vertical profiles of pore-water chemistry have been obtained for a peatland using diffusive equilibrium in thin films (DET) gel probes. Comparison of DET pore-water data with more traditional depth-specific sampling shows good agreement and the DET profiling method is less invasive and less likely to induce mixing of pore-waters. Chloride mass balances as water tables fell in the early summer indicate that evaporative concentration dominates and there is negligible lateral flow in the peat. Lack of lateral flow allows element budgets for the same site at different times to be compared. The high spatial resolution of sampling also enables gradients to be observed that permit calculations of vertical fluxes. Sulfate concentrations fall at two sites with net rates of 1.5 and 5.0nmol cm− 3 day− 1, likely due to a dominance of bacterial sulfate reduction, while a third site showed a net gain in sulfate due to oxidation of sulfur over the study period at an average rate of 3.4nmol cm− 3 day− 1. Behaviour of iron is closely coupled to that of sulfur; there is net removal of iron at the two sites where sulfate reduction dominates and addition of iron where oxidation dominates. The profiles demonstrate that, in addition to strong vertical redox related chemical changes, there is significant spatial heterogeneity. Whilst overall there is evidence for net reduction of sulfate within the peatland pore-waters, this can be reversed, at least temporarily, during periods of drought when sulfide oxidation with resulting acid production predominates.

Geochemistry of iron and manganese in soils and sediments of a mangrove system, Island of Pai Matos (Cananeia - SP, Brazil)

Five zones along a transect of 180 m were selected for study on the Island of Pai Matos (Sao Paulo, Brazil). Four of the zones are colonised by vascular plants (Spartina SP, Laguncularia LG, Avicennia AV and Rhizophora RH) and were denominated soils, and the other zone, which lacks vegetation, was denominated sediment (SD). The geochemical conditions differed significantly in soils and sediment and also at different depths. The soils were oxic (Eh > 350 mV) or suboxic (Eh: 350-100 mV) at the surface and anoxic (Eh < 100 mV) at depth, whereas in the sediment anoxic conditions prevailed at all depths, but with a lower concentration of sulphides in the pore water and pyrite in the solid fraction. Under these geochemical conditions Fe is retained in the soils, while the Mn tends to be mobilized and lost. The most abundant form of iron oxyhydroxide was lepidocrocite (mean concentration for all sites and depths, 45 +/- 19 mu mol g(-1)), followed by goethite (30 19 mu mol g(-1))and ferrihydrite (19 +/- 11 mu mol g(-1)),with significant differences among the mean concentrations. There was a significant decrease with depth in all the types of Fe oxyhydroxides measured, particularly the poorly crystalline forms. The pyrite fraction was an important component of the free Fe pool (non-silicate Fe) in all soils as well as in the sediment, especially below 20 cm depth (mean concentration for all sites and depths, 60 +/- 54 mu mol CI). Furthermore, the mean concentration of Fe-pyrite for all sites and depths was higher than that obtained for any of the three Fe oxyhydroxides measured. The Fe-AVS was a minor fraction, indicating that the high concentrations of dissolved Fe in the soils in the upper area of the transect result from the oxidation of Fe sulphides during low tide. Mossbauer spectroscopy also revealed that most of the Fe (III) was associated with silicates, in this case nontronite. The presence of crystals of pyrite associated with phyllosilicates in samples from the upper layer of the soils may indicate that pyritization of this form of Fe(III) is more rapid than usually reported for ocean bed sediments. The sequential extraction of Mn did not reveal any clearly dominant fraction, with the Mn-carbonate fraction being the most prevalent, followed by exchangeable Mn and oxides of Mn, whereas pyrite-Mn and Mn associated with crystalline Fe-oxides were present at significantly lower concentrations. The high concentration of dissolved Mn found in the soils in the lower part of the transect is consistent with the fact that the solubility is determined by the carbonate fraction. Unlike for Fe, in the soils in the higher zone, which are subject to intense drainage during low tide, there was loss of Mn, as reflected by the concentration of total Mn. (C) 2008 Elsevier B.V. All rights reserved.

Ecogenômica de archaea e monitoramento de comunidades de procariotos redutores de sulfato: aplicações na indústria de petróleo e gás

The human activities responsible for the ambient degradation in the modern world are diverse. The industrial activities are preponderant in the question of the impact consequences for brazilian ecosystems. Amongst the human activities, the petroliferous industry in operation in Potiguar Petroliferous Basin (PPB) displays the constant risk of ambient impacts in the integrant cities, not only for the human populations and the environment, but also it reaches the native microorganisms of Caatinga ground and in the mangrove sediment. Not hindering, the elaboration of strategies of bioremediation for impacted areas pass through the knowledge of microbiota and its relations with the environment. Moreover, in the microorganism groups associated to oil, are emphasized the sulfate-reducing prokaryotes (SRP) that, in its anaerobic metabolism, these organisms participate of the sulfate reduction, discharging H2S, causing ambient risks and causing the corrosion of surfaces, as pipelines and tanks, resulting in damages for the industry. Some ancestries of PRS integrate the Archaea domain, group of microorganisms whose sequenced genomes present predominance of extremophilic adaptations, including surrounding with oil presence. This work has two correlated objectives: i) the detection and monitoring of the gene dsrB, gift in sulfate-reducing prokaryotes, through DGGE analysis in samples of mDNA of a mangrove sediment and semiarid soil, both in the BPP; ii) to relate genomic characteristics to the ecological aspects of Archaea through in silico studies, standing out the importance to the oil and gas industry. The results of the first work suggest that the petrodegraders communities of SRP persist after the contamination with oil in mangrove sediment and in semiarid soil. Comparing the populations of both sites, it reveals that there are variations in the size and composition during one year of experiments. In the second work, functional and structural factors are the probable cause to the pressure in maintenance of the conservation of the sequences in the multiple copies of the 16S rDNA gene. Is verified also the discrepancy established between total content GC and content GC of the same gene. Such results relating ribosomal genes and the ambient factors are important for metagenomic evaluations using PCR-DGGE. The knowledge of microbiota associated to the oil can contribute for a better destination of resources by the petroliferous industry and the development of bioremediation strategies. Likewise, search to lead to the best agreement of the performance of native microbiota in biogeochemical cycles in Potiguar Petroliferous Basin ecosystem

Remoção de etanol e benzeno em reator anaeróbio horizontal de leito fixo na presença de sulfato

In this study it is reported the operation of a horizontalflow anaerobic immobilized biomass (HAlB) reactor under sulfate-reducing condition which was also exposed to different amounts of ethanol and benzene. The HAIB reactor comprised of an immobilized biomass on polyurethane foam and ferrous and sodium sulfate solutions were used (91 and 550 mg.l -1, respectively), to promote a sulfate-reducing environment. Benzene was added at an initial concentration of 2.0 mg.l -1 followed by an increased to 9 e 10 mg. l -1, respectively. Ethanol was added at an initial concentration of 170 mg.l -1 followed by an increased range of 960 mg.l -1. The reactor was operated at 30 (± 2) °C with hydraulic detention time of 12 h. Organic matter removal efficiency of 90% with a maximum benzene degradation rate of 0.07 mv, benzene.mg -1 vss.d -1 Thus, this work corroborate the data obtained for Cattony et al (2005) and also demonstrate that compact units of HAIB reactors, under sulfate reducing conditions, are a potential alternative for in situ aromatic compounds bioremediation.