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30th International Meeting on Organic Geochemistry (IMOG 2021)
- Conference date: September 12-17, 2021
- Location: Online
- Published: 12 September 2021
201 - 250 of 279 results
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Organic Matter Input to Marine Sediments off East Antarctica
Authors Z. Li, S. George and H. SadatzkiSummaryTo investigate the organic matter input to the East Antarctic sea floor during marine isotopic stages (MIS) 1 to 3, twenty samples from two kasten cores, KC02 (0–230 cm) and KC04 (0–245 cm) from the continental slope close to the Sabrina Coast were studied for their organic geochemical characteristics. The aliphatic and aromatic compounds all indicate a strong terrigenous organic matter input with a minor marine algal contribution. The transportation of organic matter by glaciers from the Antarctic land-mass and dust deposition could be possible explanations for such a significant terrigenous and allochthonous input.
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Under Low Oxygen Conditions, Ascomycete Fungi Blur Their Ergosterol Biosignature by Taking Up Sterols from the Environment
Authors C. Heim and C. BeimfordeSummaryStromatolithic Fe-oxide precipitating biofilms living in the subsurface at 160m depth of the Äspö Hard Rock Laboratory were investigated for their biomarker content and the inhabiting microbial community. Analytic microbial, molecular and biochemical methods, amongst next generation sequencing and biomarker studies (GC-MS), allowed a detailed characterization of the microbial community inhabiting the biofilms which surprisingly concisted of bacteria, archaea and fungi. Biomarker studies of the fungal isolates implicate that ascomycete fungi produce ergosterol under ideal oxygen conditions. In natural environments with low oxygen conditions, like in the investigated biofilm, fungi are able to take up sterols from the environmental food source, thereby blurring their conventional biomarker signature. Due to the ubiquity of the analysed ascomycetes in sediments, our results imply that fungi may simply be overlooked if we just rely on the classical ergosterol biomarker.
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The Kupferschiefer in Spremberg, East Germany: Signals of Organic Matter Alteration from Hydrogen Isotopes and Nso Compounds
Authors S. Poetz, Y. Liu, A. Vieth-Hillebrand, S. Yang, J.M. Magnall, S.A. Gleeson and H. SchulzSummaryOre forming processes in sediment-hosted sulfide deposits are widely regarded to involve organic matter (OM). However, the precise nature of interactions between OM and hydrothermal fluids are still debated as well as how the interconnected reactions develop over geological timescales. Here, we present results from an advanced characterization of organic matter in the Kupferschiefer from Spremberg in Northeast Germany with a focus on NSO (organonitrogen, sulfur and oxygen compounds) and compound specific hydrogen isotopes.
The observed strong enrichment of D in the n-alkanes that is not linked with thermal maturity likely occurred due to intensive hydrogen exchange with an evaporitic brine with an initial high δD value. Signals of slight degradation and oxidation argue against interaction of the organic matter with strongly oxidizing and hot metal bearing brines. Further work is required to assess if the fluids have become less oxidised and cooler due to water-rock interactions during migration (and yet maintained copper in solution) or if different fluids were involved in the mineralization of the Spremberg Kupferschiefer.
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Combined Source and Maturity Influence on Molecular Tracers and Implications For Oil-Source Correlation in Deep Reservoirs
More LessSummaryIn this study, geochemical characteristics of two Devonian oil families in Western Canada Sedimentary Basin (WCSB) will be used as an example, to demonstrate the source affected trends in thermal maturation of common biomarker compounds in crude oils. Our results suggest that deconvolution of the possible source and maturity effects is necessary to ensure the effective application of molecular tracers in oil-source correlation of the deep petroleum systems. Comparison of the molecular parameters for the three sample sets reveals several distinct compositional straits for the evaporate and carbonate sourced oils. The most important feature of the chemical composition and molecular distributions for these oils is the significant variation in the concentrations of sulfur containing compounds and the abundance of 17(H)-hopanes relative to other terpenoid components such as 8,14-secohopanes, C23 tricyclic terpane, C24 tetracyclic terpane, 18(H)-22,29,30-trisnorneohopane (Ts) and 18(H)-30-norneohopane (C29Ts). These oils form several continuums between the extreme end members of terpane and sterane distributions likley reflecting the inherited differences in source character, diagenetic change, and thermal cracking effects between the sulfate and iron-rich source rocks. Recognizing lithofacies signature and matrix effects is important for deep reservoired fluids, as it could signficantly increase the confidence of biomarker data interpretation.
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Basin scale evaluation: Organic geochemical characteristics of northern Perth Basin (Early Triassic)
Authors T. Taniwaki, C. Elders and K. GriceSummaryBiomarker analysis has been conducted on rock samples of the Late Permian to Early Triassic Kockatea Shale containing microbial mats in the northern Perth Basin. The northern wells of the northern Perth Basin exhibit darker shale horizons and contain microbial mats. These horizons contain abundant carotenoid biomarkers attributed to PZE and microbial mats. Such biomarkers are however, not identified in the southern wells of the northern Perth basin which are deposited under more oxic conditions in a tidal regime. In the northern wells, there are fluctuations of PZE conditions intruded by oxic conditions, caused by fluctuations of the chemocline. Elevated 2α-methylhopanes index and higher renieratane and renierapurpurane/isorenieratane ratio are identified in the microbial mats formed under oxic conditions. In addition, the higher proportion of both okenane against chlorobactane and isorenieratane and C33 n-alkylcyclohexane ratio (n-C33 ACH ratio) are identified in the microbial mat facies.
The combination of organic geochemistry (biomarker analysis) and geology (core observation, well analysis and seismic interpretation) show a strong relationship between basin morphology, paleogeography and paleoenvironmental conditions. The southern wells experienced higher influence of fluvial input (oxic conditions). The northern wells, which are far north of the fluvial input show evidence for PZE conditions.
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THE DIFFERENCES IN THE YIELD, PARAMETERS AND CARBON ISOTOPES OF LIGHT HYDROCARBONS OBTAINED BY TWO COLLECTION METHODS
More LessSummaryIn this study, two liquid hydrocarbon collection methods were used to collect light hydrocarbons generated from the cracking of crude oil in closed system, and the characteristics of the products collected were compared. Relative to the liquid nitrogen direct freezing collection (LNDF) method, the traditional liquid hydrocarbon collection (TLH) method can cause the yield loss of 10%-75% of light hydrocarbons, especially low carbon number light hydrocarbons (such as nC6, nC7, benzene, toluene, and 3-methylhexane). Because the TLH method can lead to various degrees of loss for different compounds in light hydrocarbons, it can also lead to the deviation of some light hydrocarbon parameters representing oil-oil correlation, indicating the maturity of crude oil and reflecting secondary alteration of crude oil. In addition, the δ13C values of nC6, nC7, benzene, toluene and 3-methylhexane collected by TLH method are heavier. These compounds with heavier δ13C values are the ones that have suffered the most yield loss in the TLH method. Therefore, the LNDF method can more accurately reflect the yield, parameters and carbon isotopes of light hydrocarbons in closed system pyrolysis.
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Mobilization of pre-aged organic carbon in the Nile-River watershed linked to hydologic changes during the past 20ka
Authors V. Meyer, G. Mollenhauer and E. SchefußSummaryThis project seeks to detect perturbations in the carbon cycle in large (sub-) tropical watersheds during the last deglaciation and the Holocene and to understand their climatic controls. It is generally assumed that in tropical regions, the fluvially exported organic matter is rather young due to rapid carbon turnover and often dense vegetation in the catchments. However, evidence for mobilization of pre-aged organic carbon in tropical regions has recently been obtained from the Congo-River catchment. Hydrology is suggested as a major control on the mobilization of pre-aged organic matter mediating the carbon storage in river-associated wetlands. Yet, the link between hydrology and the mobilization of old carbon in tropical regions as well as the associated climate feedbacks remain poorly constrained. Here, we investigate whether hydrologic changes affected the re-mobilization of pre-aged terrigenous organic carbon in the Nile-River watershed during the past 20ka. We present biomarker data from a sediment core recovered from the Mediterranean. Applying compound-specific radiocarbon analysis on terrigenous biomarkers we identify intervals of intensified mobilization of pre-aged terrigenous organic matter. We combine these data with compound-specific stable hydrogen isotope compositions of the same compounds to reconstruct past hydrologic conditions and their effects on mobilization of pre-aged organic matter.
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NOVEL INSIGHTS INTO PALEOVEGETATION RECONSTRUCTION OF THE BEERBERG PEAT SEQUENCE (THURINGIA, GERMANY) THROUGH THE USE OF MULTIPLE PROXIES
Authors C. Thomas, M. Galka, S. Czerwiński, K. Knorr, E. Van Loon, B. Jansen and G. WiesenbergSummaryUsing a core from the Beerberg peatland, we investigated the paleovegetation through multiple proxies including macrofossil, pollen, and biomarkers. The biomarker results, including n-alkanes, n-alcohols, and n-fatty acids, were used with the VERHIB model to estimate vegetation composition. The macrofossil and pollen results were used to calibrate and verify the model.
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Organic Geochemistry Studies of Carbonate-Evaporative Sourced Oils in the Southernmost Gom
Authors A.F. Cedeño Motta, S. Ohm and A. EscalonaSummaryOils derived from carbonate-evaporative sources are characterized by low API gravities, and overall low amounts of hydrocarbons as compared to polars and asphaltenes ( Orr, 1996 ). These aromatic-asphaltic oils originate from sulfur-rich type I-IIS kerogens at low levels of thermal stress ( Orr, 1996 ). The Peten-Corozal Basin in Guatemala and Belize lies at the southernmost end of the Mexican Gulf of Mexico (GoM) and hosts the most proximal areas of a mid-Cretaceous carbonate-rich platform, which is known to contain several source rock intervals. Bulk geochemical and biomarker data are used here to characterize the organic facies generating the oils found in the Peten-Corozal Basin.
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Carbon and Hydrogen Isotopic Analyses of Bacterial Lipids Reveal Dramatic Biogeochemical Responses to Ancient Warming
Authors R. Pancost, D. Naafs, J. Blewett, G. Inglis, V. Lauretano, X. Dang, S. Xie, A. Pearson, F. Elling and L. KatteinSummaryHere, we explore the use of bacterial and archaeal lipid carbon and hydrogen isotopic compositions to explore carbon cycling processes in modern settings and in response to ancient warming events. Investigations of Holocene peat and Eocene lignites reveal both stability over long time-scales but rapid, transient responses to climate perturbations.
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Pyrolysis of an Artificially Matured Shale Havning Type Ii Kerogen and Its Retained Oil: Implications for Late Gas Potential
More LessSummaryWe present the results of the pyrolysis using shale powder to see whether the presence of minerals and/or water has significant effects on the kerogen-oil interactions and related late gas generation. The results indicates minor effects of minerals and water in the shale on the gas generation processes under the employed conditions in this study. The oil expulsion has played an important role in enhancing late gas generation, which may be associated with the changes in the kerogen structure.
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Flame Extinguished! End-Triassic Mass Extinction Polycyclic Aromatic Hydrocarbons Reflect More Than Fire
Authors C. Fox, J.H. Whiteside, P.E. Olsen and K. GriceSummaryWidespread biomass burning events during the end-Triassic mass extinction are supported by combustion-derived polycyclic aromatic hydrocarbons (PAHs) from European and Greenland sections. However, our investigation into a range of PAHs from focal end-Triassic extinction outcrops in the southwest UK reveals otherwise. We find major discrepancies in combustion-derived PAHs that support ETE biomass burning events were more localised. In addition, we find evidence of soil erosion during the newly proposed marine expression of the end-Triassic extinction and no evidence of biomass burning. Finally, below the extinction horizon good correlation between increases in combustion-derived PAHs and low molecular weight S- and O-containing PAHs associated with the terrestrial realm suggest that increased continental run off could account for changes in pyrogenic PAHs given their degraded but pyrogenic source.
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Molecular Characterization of Dissolved Organic Matter in Deep Geothermal Fluids
Authors A. Leins, A. Vieth-Hillebrand, S. Regenspurg, F. Eichinger and S. PötzSummaryWithin the Horizon 2020 REFLECT project (Redefining geothermal fluid properties at extreme conditions to optimize future geothermal energy extraction), organic compounds in deep fluids from geothermal sites are being characterized and interpreted with regard to numerous site parameters. DOC concentrations and the relative abundance of DOC fractions from fluid samples of two sites located in Austria and Germany were analyzed via Liquid Chromatography - Organic Carbon Detection (LC-OCD). Fourier Transform Ion Cyclotron Resonance Mass Spectrometry (FT-ICR-MS) with Electrospray (ESI) and atmospheric pressure photoionization (APPI) has been applied to characterize DOM on a molecular level and its changes of time and flow path. The Austrian site Bad Blumau is located in Styrian Basin and uses deep fluids from a Palaeozoic carbonate reservoir (104°C). Samples were taken from production and injection side, as well as from the heat central. The Berlin drill site is part of the North German Basin and targets a limestone formation (Muschelkalk) with a reservoir temperature of 32°C. Samples were taken during a lift test over a period of 25 hours. A better understanding of the role of organic compounds in geothermal fluids might help to optimize present and future geothermal energy extraction.
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STRATIGRAPHIC CHANGES OF GEOCHEMICAL SIGNATURES OF THE CENOZOIC BALINGIAN COAL, SARAWAK, MALAYSIA.
Authors N.S. Zainal Abidin, K.A. Mustapha, W.H. Abdullah and M.H. HakimiAbstractThe thick coal seams of the Cenozoic Balingian coals in the Liang Formation, Sarawak, Malaysia are of interest in the present work. Through this paper, the genesis of the environmental conditions of thick coal seams in relation to their ancient peat and paleomires were investigated in vertical profile. A total of 40 coal samples were prepared and characterised based on organic geochemical analysis. The TOC content range is 40.5 to 58.2 wt.%, and the HI values range from 43 to 441 mg HC/g TOC in the samples tested. Collectively, the analysed coal samples were characterised by mixed Type II-III kerogen and predominantly Type III kerogen and demonstrated the ability to produce substantial gas and some oil generation potential. The carbon/nitrogen ratio of over 20, notable odd-over-even predominance, high long chain C25–35 n-alkanes (mean 79%), moderate ratios of pristane/phytane (mean 1.37) and diterpenes (mean 1.06), moderate carbon preference index (CPI, mean 1.98), high Tm/Ts (mean 2.52), high C29 norhopane/ C30 hopane (mean 3.21) and high C29 steranes (mean 63%) of the studied coals indicate the dominance of terrestrial source inputs. The ratio of C27/C31 (0.06 – 3.64) may further indicates a decrease in woody vs. herbaceous input characterised the upward trend. Peat’s doming is a significant factor of lowered in ash, and sulphur. The mildly influenced of brackish water in the ombrogenous peat were observed by slightly increase of C27, C28 steranes and decrease of C29 steranes and slightly increase of sulphur content. The ancient peat and mires are subjected to ever-wet climates, however an alternance relatively wet and dry episodes were deduced from the variation of n-alkanes, pristane/phytane and diterpanes ratios. The biomarker signatures, furthermore, indicative of oxygen-deficient and water-saturated conditions in the precursor mires due to seasonal dry/wet climates by high and reduced rainfall during peat growth.
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Organic Matter Distribution is Controlled by Sedimentological Parameters in Marine Oxygen Minimum Zone
Authors E. Bruni, T.M. Blattmann, N. Haghipour, D.B. Montlucon and T.I. EglintonSummaryOrganic matter (OM) in marine sediment is usually associated with mineral surfaces because it offers protection from degradation. As the amount of OM on a particle increases, so does its grain size, but its density decreases. The reduced density of the surface sediment results in a high propensity for resuspension, therefore aggregate transport represents an efficient way to relocate OM to offshore sites and depocentres on the continental slope. This process has significant effects on reconstructing past environments as OM is laterally displaced from where it was produced.
OM abundance in sediments is negatively correlated to oxygenation state; hence, oxygen minimum zones are often characterised by a soft, soupy sediment surface. We study samples from the Benguela upwelling system offshore Namibia, where widespread lateral transport has been described and significant age differences are reported between compounds (alkenones, crenarchaeol), calcareous shells, and bulk organic carbon. Working with the comprehensive dataset on environmental tracers on the Benguela upwelling system, we use bulk molecular tracers on core-top samples and their respective grain size and density fractions to trace resuspension effects on sedimentary OC ageing in anoxic and oxic water condition.
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Geochemical Fluid Classifications Using Supervised Machine Learning Techiniques
Authors G. Spaak, R. Van der Ploeg, J. Weijers, S. Van den Boorn, S. Bierman and O. PodlahaSummaryThis study explores the use of novel data analysis techniques such as supervised machine learning algorithms to unlock the full potential of large geochemical datasets
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Oil and Gas Potential Source of the Lake Baikal Sediments: Gas-Geochemical and Biomarker Study
Authors O. Vidishcheva, M. Delengov, N. Fadeeva, E. Poludetkina, E. Bakay, G. Akhmanov, A. Mazzini, N. Morozov and O. KhlystovSummaryThis paper presents the results of surface geochemical exploration of Lake Baikal bottom sediments. Such studies provide information on the quality, thermal maturity, age, and distribution of the underlying source rock in under-explored and poorly understood basin. The studies presented in the work were obtained during the Class@Baikal expeditions (2014–2020).
Gas-geochemical and biomarker study permit determine that the initial organic matter of both gas and oil source rocks has a mixed origin with a predominance of the terrestrial component.
Most of the samples of organic matter from the bottom sediments showed a severe biodegradation process. The samples from the oil seep present a unimodal distribution with n-C23 to n-C25 as the major peaks. The CPI values ∼ 0.97, and the Pr/Ph ratio is close to 1 indicating an input of algal/microbial organic matter with a significant input of terrestrial matter.
Biomarkers evidence the high maturity of initial organic matter (end of the oil generation zone - the beginning of the gas generation zone). Thus, the ratio Ts / (Ts + Tm) up to 0.78 (Parameter MPI-1 up to 1.59).
The δ13C isotopic composition ranges between −26 and −28‰ indicates a terrestrial organic matter origin.
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Development of Organic Matter Porosity During Thermal Maturation: Study on the Example of the Bazhenov Formation Source Rocks
Authors T. Karamov, E. Leushina, E. Kozlova, T. Bulatov and M. SpasennykhSummaryThe porosity of shales consists of mineral matrix voids and pores in organic matter. Since organic matter occupies up to 50% of source rock volume and most of the pores are connected, this type of porosity may considerably contribute to saturation of rocks by hydrocarbons. The study is devoted to the investigation of organic matter (kerogen) porosity development during thermal maturation of source rocks using SEM. On the example of the Bazhenov Formation source rocks, we have demonstrated the presence of nano- and micropores in solid organic matter at the beginning of the oil window and a developed porous structure at the end of the oil window with organic matter porosity of more than 50% of kerogen volume. The obtained results expand existing knowledge on void space volume of the Bazhenov formation and show that organic matter porosity of mature kerogen may several times exceed intergranular porosity of rock.
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New Frontiers in Compound-Specific δ2H Analysis
Authors S. Lengger, S. Kelly, K.W.R. Taylor, Y. Weber, S. Kopf, R. Berstan, M. Seed, I. Bull, J. Meyser, W. Leavitt, J. Blewett, A. Abrahim, A. Cannavan, A. Pearson and R. PancostSummaryElementar UK Ltd present present two pioneering new techniques for the analysis of larger and/or more polar organic molecules of biogeochemical interest which are traditionally considered unamenable for gas chromatography stable isotope ratio mass spectrometry (GC-IRMS) analysis, which have been developed by and in collaboratoration with Elementar GC-IRMS users from a variety of laboratories. This includes a rapid one-step derivatization procedure for the isotope analysis of the non-exchangeable hydrogen in mono and disaccharides and subsequent conversion to H2 by chromium reduction ( Abrahim et al, 2020 ), and the development of a high-temperature GC-IRMS (HTGC-IRMS) methodology employed for the analysis of a suite of compounds of interest ( Lengger et al., 2021 ).
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Preliminary Ams 14C Measurements from Holocene-Age Carbonate Concretions
Authors A. Mojarro, B. Uveges, M. Roberts, J. Vinther and R. SummonsSummaryIn order to better constrain the timescale and mechanisms for concretion formation, we have analysed two Holocene-age concretions from contrasting depositional environments which display divergent levels of soft-tissue preservation. Inorganic carbon samples (carbonate) were taken at successively greater distances from the center of the concretion for accelerator mass spectrometry (AMS) 14C dating.
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USING BACTERIAL HOPANOIDS TO FINGERPRINT PEAT-DERIVED ORGANIC MATTER ALONG THE TERRESTRIAL-AQUATIC CONTINUUM
Authors G. Inglis, B.D.A. Naafs, R. Pancost, J. Toney and J. BendleSummaryPeat is a heterogeneous mixture of (partly) decomposed plant material that forms large carbon stores. However, if peat-derived organic carbon (OCpeat) is eroded and transported along the terrestrial-aquatic continuum, it may act as a source of carbon to the atmosphere. Modern observational evidence suggests that carbon losses from peatlands are significant and an increasing component of the global carbon cycle ( Moore et al., 2013 ). Although relatively well-constrained at present, the transfer of OCpeat along the terrestrial-aquatic continuum remains poorly constrained in ancient settings. Radiocarbon measurements can be used to distinguish between fresh OC and older peat-derived OC ( Moore et al. 2013 ). However, because the half-life of 14C is relatively short, this approach cannot be used beyond ∼50,000 years and alternative techniques are needed to probe this during different climate states, e.g. greenhouse climates of the Eocene. Here we explore whether the stereochemical properties of bacterial hopanoids can be used to fingerprint peat-derived OM along the terrestrial-aquatic continuum.
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USING BACTERIAL HOPANOIDS TO FINGERPRINT PEAT-DERIVED ORGANIC MATTER ALONG THE TERRESTRIAL-AQUATIC CONTINUUM
Authors G. Inglis, B.D.A. Naafs, R. Pancost, J. Toney and J. BendleSummaryPeat is a heterogeneous mixture of (partly) decomposed plant material that forms large carbon stores. However, if peat-derived organic carbon (OCpeat) is eroded and transported along the terrestrial-aquatic continuum, it may act as a source of carbon to the atmosphere. Modern observational evidence suggests that carbon losses from peatlands are significant and an increasing component of the global carbon cycle ( Moore et al., 2013 ). Although relatively well-constrained at present, the transfer of OCpeat along the terrestrial-aquatic continuum remains poorly constrained in ancient settings. Radiocarbon measurements can be used to distinguish between fresh OC and older peat-derived OC ( Moore et al. 2013 ). However, because the half-life of 14C is relatively short, this approach cannot be used beyond ∼50,000 years and alternative techniques are needed to probe this during different climate states, e.g. greenhouse climates of the Eocene. Here we explore whether the stereochemical properties of bacterial hopanoids can be used to fingerprint peat-derived OM along the terrestrial-aquatic continuum.
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Evidence for the Role of Water in Ch4 Generation from Long-Term, Low Temperature Experimental Maturation of Immature Shales
Authors K. Doiron, P. Sauer, A. Schimmelmann, M. Mastalerz, A. Drobniak and S. BrassellSummaryThe conventional paradigm for generation of economically viable petroleum reserves involves thermal cleavage of C-C bonds within sedimentary organic matter. However, there is evidence for alternative chemical pathways yielding non-microbial methane generation at low temperatures. In addition, assessing the role of water in methane generation at temperatures lower than those required for it to form by thermal cracking represents a critical step for evaluating processes likely involved in catalytic methanogenesis. Previous pyrolysis experiments of source rocks in the presence and absence of water have yielded insights on the role of water in CH4 generation at a range of maturities including late-stage thermogenesis. Our studies explore the role of catalytic pathways in CH4 generation by experiments simulating maturation of immature source rocks at temperatures insufficient to achieve thermal cleavage of C-C bonds. These hydrous maturation experiments demonstrate that immature shales can generate CH4 at temperatures (80–100 °C). They establish the potential to yield δ13C values <-70 ‰ commonly associated with microbial gas by early CH4 generation at low maturity levels. Incorporation of 2H derived from 2H-enriched water in these hydrous maturation experiments confirms the role of water in catalytic processes generating CH4 at low temperatures.
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Trace Elements in Antarctic Algae and Moss
Authors S. Chatterjee, S. Das, A. Chakraborty and S. PalchaudhurySummaryConcentrations of Al, Fe, Co, Cu, Mn, Ni, Zn and V, were measured in algal and moss samples collected from areas surrounding different freshwater lakes in Larsemann Hills of East Antarctica. This study focuses on the relative distribution of these elements within these organisms, and the extent of bioaccumulation occurring in the algal and moss samples.
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Assessment of Sedimentary Botryococcenes in Vietnamese Maar Lakes as Paleoclimate Proxies
Authors K. Doiron, L. Stevens and S. BrassellSummaryIn contemporary settings, suites of C30-C37 hydrocarbons with botryococcene-related structures, including monocyclic and bicyclic components, have been identified in East African maar lakes and in the Everglades. The sedimentary concentrations of these compounds can be substantive, dwarfing other aliphatic hydrocarbon constituents. Distributions of botryococcenes in sediment samples spanning the past 32 kyr from Lake Masoko, Tanzania, reveal temporal variations attributed to variations in dominant strains of B. braunii rather than a response to changing environmental and climate conditions. Recognition of similar suites of botryococcenes in Vietnamese maar lakes with records that extend back past the Last Glacial Maximum now affords the opportunity to further assess the possibility that botryococcene distributions may record climatic information in these settings. The relative abundances of C34:2 botyrococcene (A) and C34:3 monocyclic botyrococcene (M) in a sediment core from Lake Ia M’He in the Central Highlands of Vietnam, expressed as % M/(A+M), reveals a progressive decrease in the proportions of the monocyclic component relative to the acyclic botyrococcene from the last glaciation to the recent past. These data suggest that assessment of links between the distribution of these specific botyrococcene components in Lake Ia M’He sediments and changes in climate is merited.
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Unsupervised and Supervised Machine Learning to Classify Oils from the Norwegian Continental Shelf North of 62°N
Authors J. Rinna, P. Aursand and B. LerchSummaryUnsupervised and supervised machine learning algorithms were applied on two large geochemical data sets, one from the Norwegian Sea and an other from the Barents Sea. Data bases were thoughtfully examined with regard to sample type, contamination, and data integrity, respectively. The purpose of this work is to compare both traditional and machine learning approaches for oil-oil and oil-source rock correlation on two large datasets on the Norwegian Continental Shelf. Unsupervised clustering of oil samples produces classes that are, overall, consistent with geological understanding of the origin of the oils. We established a workflow using supervised learning that enables an expert to infer oil types and source rock correlation in an immature (low confidence) area given available samples in a mature (high confidence) area. We emphasize through examples the importance of data quality and data consistency when using machine learning for automatic oil typing.
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Characteristics of dissolved organic matter released by hot-water extraction of organic-rich Guaymas Basin sediments
Authors J. Brünjes, M. Seidel, A. Teske and F. SchubotzSummaryThe Guaymas Basin (GB) in the Gulf of California is a young rift system where hot basaltic sill intrusions into unconsolidated organic-rich sediments lead to the generation of complex petroleum compounds and discharge of bioavailable dissolved organic matter (DOM) into the overlying water column. However, the contribution of hydrothermal heating to the release of recalcitrant DOM, for instance polycondensed aromatic compounds (PCAs), has not been studied yet. PCAs such as dissolved black carbon in marine DOM are thought to be mainly derived from incomplete combustion of terrestrial organic matter on land and accumulate in the oceanic carbon reservoir over thousands of years. Recent research, however, points to additional sources with a marine isotopic signature, for instance petrogenic carbon.
In our study, we investigate whether hydrothermally heated sediments release DOM that can contribute to the recalcitrant oceanic DOM pool. We simulated hot-water discharge events by Soxhlet extraction of sediment core samples from GB sites with in situ temperatures up to >105°C and analyzed DOM by ultra-high resolution mass spectrometry (FT-ICR-MS) and optical spectroscopy. Our preliminary results suggest that hydrothermal mobilization of DOM from organic-rich sediments can release aromatic and sulfur-enriched compounds that may contribute to the recalcitrant deep oceanic DOM pool.
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DEEP MICROBIAL SIGNATURES IN TERTIARY SEDIMENTS OF THE HARTOUŠOV CO2 MOFETTE SYSTEM, NW BOHEMIA
Authors K. Mangelsdorf, K. Adler, Q. Liu, H. Kämpf, R. Bussert, B. Plessen, H.M. Schulz, D. Lipus, P. Krauze, F. Horn, D. Wagner and M. AlawiSummaryPast and present microbial signatures were investigated in deep sedimentary successions of the Hartousov CO2 mofette system (NW Bohemia, Czech Republic). In about 78 m depth a CO2 reservoir was penetrated by the Hartousov borehole leading to a CO2 blow out. This core interval was selected for further analysis to test whether this section could represent a specific habitat stimulating a deep CO2-related microbial ecosystem. We applied organic geochemical, biogeochemical and microbiological approaches to characterize the deep mofette ecosystem. Necrotic microbial biomarkers reflect the microbial biomass during time of deposition and are not suitable to trace the deep biosphere at the Hartousov site. Common intact phospholipid life markers (IPLs) were not detected in significant amounts. However, two clusters of unknown lipids presumably with a sulfonic head group and ether side chains with different chain length could be identified, which might represent specific mofette related bacteria. Microbiological analysis point to a low abundant but characteristic microbial community consisting of Acidovorax, Aquabacterium, Hydrogenophaga, Sulfuricurvum and unknown genera of the family Comamonadaceae. Overall, although there is an adapted deep microbial community in the CO2 reservoir of the mofette system, this interval does not seem to represent a specific hotspot for deep microbial life.
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Arctic Alaska Petroleum Systems: Characterizing Mixtures and Charge History Using Advanced Geochemical Technologies
Authors P. Botterell, J.M. Moldowan, D. Houseknecht, S. Barbanti, J. Dahl and P. LillisSummaryThe Arctic Alaska petroleum province is geologically and geochemically complex. Mixed hydrocarbon charge from multiple source rocks and/or levels of thermal maturity is common within an individual oil pool. Molecular fingerprinting tools are used in the present study to characterize and establish genetic relationships among a suite of oils sampled from multiple discoveries and fields across the North Slope. Applications of Advanced Geochemical Technologies (AGTs) are utilized to identify and correlate fluids generated from deep sources, determine co-sources for oil mixtures, and ascertain controls on hydrocarbon provenance ( Dahl et al., 1999 ; Moldowan et al., 2015 ). The AGTs presented here comprise quantitative diamondoid analysis (QDA), quantitative extended diamondoid analysis (QEDA), compound specific isotope analysis of diamondoids (CSIA-D), biomarker assessments by gas chromatography-tandem mass spectrometry (GC-MS-MS), CSIA of hopane and sterane biomarkers (CSIA-Bh and CSIA-Bs, respectively), and CSIA of n-alkanes (CSIA-Ac). Diamondoid analyses reveal mixed-oil accumulations in most sampled reservoirs and allow the source(s) of both post-mature and oil-window maturity charge contributions to be identified. Age-diagnostic and source-sensitive biomarker parameters provide an assessment of age ranges and depositional environmental constraints of the sources of the oil-window components. Results of CSIA-Bh, -Bs, and -Ac provide greater insight into paleoenvironments of the generative sources.
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Testing the Sponge Biomarker Hypothesis Through Identification of 24-Isopropenylcholesterol Biosynthesis Enzymes
Authors M. Brown, H. McShea, B. Olagunju, J. Giner and P. WelanderSummaryIn order to improve interpretations of the demosponge biomarker 24-isopropylcholestane (24-ipc), we examine the biosynthesis of side chain alkylated sterols, including 24-isopropenylcholesterol, through functional analysis of sterol methyltransferases (SMTs). We experimentally demonstrate sponge SMTs are capable of multiple rounds of methylation as previously hypothesized. We also identify functional SMTs of probable bacterial origin capable of producing 24-methyl, 24-ethyl, and 24-isopropyl sterols, suggesting bacteria may be an overlooked source of side chain alkylated steranes in the geologic record, including 24-ipc.
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Pyrolysis-Compound Specific Isotope (δ13C, δ2H) Analysis (PY-CSIA) of Lignin Phenols in Soils from a Mediterranean Agro-Ecosystem
SummaryThis communication describes and validates a methodology based on analytical pyrolysis for the direct measure of lignin-derived phenols δ13C and δ2H isotope composition. The technique combines Py-GC with combustion (for C) and high-temperature conversion (for H) reactors and a continuous flow isotope ratio mass spectrometer (IRMS) (Py-CSIA).
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Cholesterol Production by the Bacterium Enhygromyxa Salina
Authors P. Welander and A. LeeSummaryWe demonstrate the production of cholesterol by Enhygromyxa salina, a heterotrophic marine bacterium. Cholesterol is a highly modified sterol that is preserved as cholestane in the rock record. Cholestane is often indicative of heterotrophic microbial eukaryotes. The production of cholesterol by E. salina is the first reported instance of cholesterol synthesis by a bacterium. Through genomic analyses, we show that E. salina has cholesterol biosynthetic genes that are homologous to the eukaryotic cholesterol pathway. However, we do observe some biosynthetic proteins that are unique to E. salina. Further, extensive lipid analyses demonstrate that cholesterol in this organism is conjugated to either a lipid or protein moiety and does not exist as a free sterol. Conjugated sterols play significant physiological roles in eukaryotes and understanding the nature of conjugated cholesterol in E. salina may provide insight into the physiological roles of these lipids in bacteria. Through these studies, we should be able to better assess what implications, if any, cholesterol production by bacteria has on our interpretation of sterol biomarkers in the rock record.
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Organic Carbon Aging as Recorded in Marine Sediments from the Cabo Frio Upwelling System (South-Eastern Brazil)
Authors M. Ceccopieri, A.L. Albuquerque, D. Lessa, R. Carreira and G. MollenhauerSummaryThe ¹⁴C-age offset between the organic matter (OM) and carbonates buried in marine sediments of the Cabo Frio upwelling system during the past 6.5 kyr was investigated. The ¹⁴C-ages of the OM were 787 ± 166 years older than those of foraminifera, which might be indicative of a long-term storage and re-processing of the OM on the mid-shelf sediments caused by local upwelling-related hydrodynamic processes. A gradual increase up to the maximum ¹⁴C-offset from 5.8 to 4.0 cal kyr BP may be a response to the intensification of the Brazil Current activity over the shelf, extending the sediment translocation and, consequently, the OC aging. Also, an intensification of the South American monsoon during this period might had favored the input of pre-aged terrigenous OM. Between 4.0 and 2.0 cal kyr BP the ¹⁴C-offset decreases, possibly due to a subsequent weakening in the bottom currents. After 1.8 cal kyr BP, a slightly increase in the ¹⁴C-offset could be caused by an upwelling enhancement. These results reinforce the existence of a temporal decoupling between the organic proxies commonly used in paleoceanographic studies and the correspondent age models applied, which highlights the need to interpret proxy-based information with caution, especially in upwelling regions.
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Calibration of Bacterial 3-Hydroxy Fatty Acid-Based Paleoclimate Proxies in Global Soils, Marine Sediments and Lakes
Summary3-Hydroxy fatty acids (3-OH-FAs), derived from Gram-negative bacterial outer membranes, have received recent attention for their potential as both: a) terrestrial temperature and pH palaeoclimate proxies; and b) marine sea-surface temperature proxies. However, the distribution and performance of 3-OH-FA based proxies at a global scale and in lake sediments remains largely unknown. This is a critical gap in knowledge as lake sediments are the most common terrestrial archive for paleoclimate. Here we explore (including the application of machine learning tools) 3-OH-FA lipid distributions in 186 globally distributed soils. We also investigate co-located lake sediments and catchment soils in China and the USA. We find that the ratio of anteiso to normal 3-OH-FAs of the C15 or C17 homologues (RAN15 or RAN17) shows a significant linear relationship with mean annual air temperature (MAAT) in global soils. However, in lakes these do not appear to be suitable for temperature calibration. Analysis of gene community composition reveals that Gram-negative bacterial populations from lake sediments are distinct from both soils and marine sediments (but are closer to the former). We find strong relationships between alternative 3-OH-FA based proxies and MAAT in lakes. Thus 3-OH-FA geochemical tools continue to show promise for palaeoclimate reconstruction.
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Pore water concentrations of low-molecular-weight organic acids – effects of thermal generation and decomposition
Authors O. Helten and C. Ostertag-HenningSummaryAt elevated temperatures e.g. caused by heat-emitting, high-level radioactive waste, low-molecular-weight organic acid (LMWOA) generation and decomposition from organic matter take place simultaneously. In the process, the generation can exceed the decomposition for individual compounds – and vice versa. As a result, concentrations of LMWOA in aqueous geological fluids undergo constant, temperature-dependent changes. This study presents hydrous pyrolysis data for the generation of three LMWOA (formate, acetate, and oxalate) from a natural claystone (Opalinus Clay). Experiments were conducted between 80–200 °C and at 20 MPa over 504 to 906 hours. Thus, the material was exposed to conditions resembling diagenesis to catagenesis. The results clearly show individual generation and decomposition behaviors. As an example, at 200 °C, acetate was continuously generated, whereas formate experienced rapid generation and successive decomposition. Oxalate decomposition outcompeted its generation, which resulted in concentrations below the limit of quantification after 48 hours. The observations are consistent with calculations using kinetic parameters for thermal LMWOA decomposition. This study emphasizes the importance of simultaneous thermal LMWOA generation and decomposition in the context of mineral dissolution, metal-ion and radionuclide complexation, for sorption processes and as a pathway to sustain microbial communities e.g. in the deep biosphere.
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An Overture to the Anthropocene: Isotopic Evidence of Strong CO2 Modulation of the Tropical Monsoon at the Dawn of Dinosaurs
Authors J. Whiteside, M. Schaller, P. Olsen, M. Margulis-Ohnuma and J. YagerSummaryGlobal climate model experiments predict that greenhouse-induced warming results in an intensification of the hydrological cycle, with amplification of the effects of astronomically paced precipitation cycles. Extreme high-CO2 intervals during the hothouse Early Mesozoic provide a test bed for this warming-induced hydroclimate hypothesis and a potential analog for our future. Here we present leaf wax n-alkane hydrogen isotope ratios, as well as lithological, plant structural forms, carbon isotope ratios, and the soil carbonate proxy for atmospheric pCO2, from non-marine strata in eastern North America, and marine strata in Peru for the hothouse world of the Late Triassic and Early Jurassic (232-200 million years ago). We place these data in the context of the modulation of the tropical monsoon by pCO2 and the ecological ascent of dinosaurs at the end-Triassic mass extinction.
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Intact Coenzyme-A-Thioester Analysis as a Tool to Characterize Bacterial Metabolism of Single Substrates and Crude Oil
More LessSummaryThis presentation reports on the development of a sensitive screening method for the detection of intact coenzyme-A-thioesters in microbial samples and its application to the study of an anaerobic n-alkane-utilizing bacterium growing under different substrate conditions. In particular, we report for the first time the coenzyme-A-thioester pattern occurring during growth of a bacterium with crude oil as a complex substrate mixture. The study reveals that intact coenzyme-A-ester analysis is a promising tool for the detection and characterization of active metabolism in microorganisms. The sensitivity of the newly developed method allows screening and identification of coenzyme-A-thioesters in microbial samples even if they occur in strongly differing abundances. We envisage that this approach can also be applied to natural samples for tracing ongoing metabolic processes.
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Deciphering the Input from Fossil and Recent Organic Carbon to Soils in Recultivation Sites in Lusatia, Germany
By S. IsmailSummaryPrevious studies from the recultivated open-cast mining sites of Lusatia differentiate only between the organic carbon pools. This enabled a rough estimation of the individual contributions but did not allow describing molecular differences between the pools nor molecular changes over time. Therefor our work aims to use Ultrahigh resolution mass spectrometry (Fourier transform ion cyclotron resonance mass spectrometry, FT-ICR-MS). It allows a deeper insight into the molecular composition of the different soil carbon pools in the recultivated open-cast mining sites. Negative ESI FT-ICR-MS measurements of the solvent extracts reveal a strong dominance of organo-oxygen compounds representing components with varying carboxylic and hydroxyl groups. The differences in the chemical compositions of the soil extracts from Bär-1 site allowed tracking the changes of the molecular composition of organic matter fractions. Higher amounts of lignite-derived compounds found in the lower part of the profile point to a reduced supply of recent organic carbon into the deeper parts of the profile and a low transformation of the recalcitrant lignite-derived OM at a depth below 40 cm due to missing melioration treatment and/or lacking roots. At Bär-2 site, the compositional inventory of the soil lipids is rather constant with depth completely lacking condensed aromatics.
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Investigating the Intramolecular Isotopic Structure of Isoprenoids Using Orbitrap Mass Spectrometry
By M. ÖztoprakSummaryIsoprenoids are a class of ubiquitous organic compounds constructed from C5 isoprene units. Pathways for their biosynthesis are highly conserved and distinct among the Domains of Life. Since the intramolecular isotopic composition of molecules strongly depends on the pathways by which they are synthesized, as well as the degree of conversion of their intermediates and the sources of their substrates, characterization of intramolecular isotopic signatures may allow for the recapitulation of these processes. Chemical and NMR methods for the study of intramolecular isotopic signatures, however, require large quantities of analyte (∼mmol), which is generally not feasible for geological samples. Here, we investigate the intramolecular carbon isotopic structure of phytane from chlorophyll of the cyanobacterium Anacystis nidulans (MEP phytane) and archaeol from the archaeon Halobacterium sp. NRC-1 (MVA phytane) at natural abundance (∼10 nmol). Orbitrap measurements were standardized relative to a commercially available phytane of unknown petrogenic origin and compared for bulk compound specific isotopic values via GC-irMS. Although intramolecular isotopic differences between analytes were not significant for mass fragment 85 m/z, our results demonstrate for the first time the accurate and precise detection of intramolecular isotopologues of large biomarker compounds at natural abundances using Orbitrap mass spectrometry.
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Microbial Membrane-Spanning Lipids: Determination of Biological Sources and Evolutionary Implications
SummaryBacterial membrane lipids are composed of a glycerol-3-phosphate backbone attached via ester bonds to fatty acid molecules, while those of Archaea have a glycerol-1-phosphate backbone linked to isoprenoids via ether bonds. The cytoplasmic membrane is generally organized as a bilayer, however the majority of archaeal membranes are organized as membrane-spanning lipids (MSLs), forming a monolayer of isoprenoidal glycerol dialkyl glycerol tetraethers (isoGDGTs). Some bacterial species produce lipids similar to the archaeal MSLs but non-isoprenoidal, i.e., branched glycerol dialkyl glycerol tetraethers (brGDGTs) that are likely produced by soil bacteria. During the past decade, these types of MSL have been increasingly used in molecular proxies. Some isoGDGTs are used in the paleotemperature proxy TEX86 to reconstruct past sea surface temperatures, while the BIT index evaluating terrestrial input is based on isoGDGTs and brGDGTs. Recently, novel GDGTs have been detected in various environments and proposed to have biomarker potential, however little is known about their sources, which is instrumental for their application as paleoproxies. Here, we investigated the biosynthetic pathway leading to the formation of bacterial MSLs by using cultivation and genomic analyses. In addition, we also investigated two anoxic and highly sulfidic environmental settings to determine the biological sources of specific isoGDGTs.
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Assessing Source Rock Organofacies Using the Ft-Icr Ms Amenable Nso-Compounds Inventory of Pyrolysates
Authors N. Mahlstedt, M. Noah and B. HorsfieldSummaryOpen-system pyrolysates of fourty-three immature source rock and coal samples covering all depositional environments and geological ages were prepared and analysed using Fourier transform-ion cyclotron resonance-mass spectrometry (FT-ICR MS) in connection with an electrospray source run in negative-ion mode to asses the fraction of acidic NSO compounds. The aim was to establish proxies based on the NSO inventory of pyrolysates for kerogen and petroleum type organofacies typing. The main result is that different depositional environments/ organofacies can be characterized using bulk NSO elemental and compound class distributions in combination with DBE class and Carbon number distributions. The feasability of the approach is demonstrated by Principal Components Analysis, whereas the geochemical background of the used loadings is discussed in detail in the paper/presentation.
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Physical Simulations of Petroleum Changes Related to Interaction with CO2 and CH4
Authors J.P. Lopes, A.J.M. Vieira and H.L.D.B. PenteadoSummaryDifferent accumulations in Brazilian marginal basins have CO2 contents varying between 0 to 80 mol %. Where the CO2 values reach their maximum, two distinct fluids were observed at the reservoir: a rich gas-condensate at the top, and a heavy oil at the bottom. The main objective of this study was to evaluate the compositional changes of oil due to the contact with CO2, in order to understand the alterations of the PVT and geochemical properties. It is evident that the mixing sequence (CO2-oil or oil-CO2) significantly alters not only the distribution of the components, but also the composition of the phases.
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Giant deep-sea Foraminifera are enriched in Archaea and associated lipid biomarkers in their agglutinated tests
Authors J. Bösche, J. Wendt, J. Lipp, S. Goffredi, L. Levin, E. Cordes, J. Cortes Nunez, K. Hinrichs and V. OrphanSummaryAs agglutinated Foraminifera, Xenophyophores inhabit the deep ocean floor and build their tests from particles of the environment. Despite their diversity and abundance, especially in areas of commercial interest for polymetallic nodules, the role of Xenophyophores in the deep-sea ecosystem and their physiology is still poorly understood. Previous studies hypothesized that their tests provide a habitat for deep-sea microbes. To further investigate Xenophyophores and associated microbes, we analyzed diverse Xenophyophores from the Quepos plateau and seamounts off Costa Rica for their lipid biomarkers and microbial 16S rRNA gene diversity.
In our data we identified archaeal glycerol dialkyl glycerol tetraethers with a high content of intact polar lipids and substantial amounts of the thaumarchaeal biomarker Crenarchaeol. This data is suggestive of a thaumarchaeal assemblage, which was independently confirmed through Illumina 16S rRNA amplicon sequencing. The spatial distribution of biomarkers we observed with mass spectrometry imaging in a section through a Xenophyophore test shows a heterogeneity, which we interpret as differences in activity, community composition and/ or growth stages of the archaeal community members.
Our lipid biomarker and molecular data suggests that Thaumarchaea are associated with diverse Xenophyophores and that their tests can provide a newly discovered micro-niche for these microbes.
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Properties and Transport of Organic Matter from the Inland to the Ocean - Influence of Coastal Wetlands.
Authors J. Gensel, M. Humphries, D. Sebag, M. Zabel and E. SchefußSummaryTo assess the influence of sub-tropical coastal wetlands on organic matter transport by rivers in southeastern Africa we conducted a multi-timescale study by characterising the current status, the recent past (∼2000years), and the time since the formation (∼6000 years) of South Africa's largest Freshwater Wetland System (MKhuze Wetland System, KwaZulu Natal). This approach and the application of multiple proxies such as plant-wax derived n-alkanes, their compound specific isotope composition, bulk organic matter parameters, Rock-Eval analyses, and persistent organic pollutant quantification enable us to decipher the three main drivers which can cause alteration in biomarker signals: (i) natural development of the system, (ii) adaptation/response to climatic events, and (iii), especially during the Late Holocene, anthropogenically induced changes. The combination of the present status (predominant vegetation, organic matter transport pathways and characteristics) with the decadally resolved records and a centennial archive promise to provide a comprehensive clarification of the evolution of a subtropical wetland in a coastal watershed and its response to climatic conditions.
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CARBON ISOTOPIC COMPOSITION OF LEAF WAX n-ALKANES OF MANGROVE PLANTS DISTRIBUTED ALONG A LATITUDINAL GRADIENT IN BRAZIL
Authors M. Ceccopieri, R. Carreira, A. Scofield, L. Almeida, C. Hamacher, C. Farias, M. Soares and A. WagenerSummaryHere we present baseline data of δ¹³C of n-alkanes (δ¹³Cn-alkanes) from leaf waxes of mangrove trees – Avicennia schaueriana, Rhizophora mangle and Laguncularia racemosa – distributed along a latitudinal gradient in Brazil. The objective was to evaluate the influence of trees physiology, local hydrology and climatic factors upon the molecular and isotopic signature of the leaf wax n-alkanes. Higher weighted average δ¹³Cn-alkanes (δ¹³CWA), average chain lenght (ACL25-35) and carbon preference index (CPI24-36) for R. mangle and A. schaueriana contrasting with lower values for L. racemosa seem to be linked to physiological characteristics of each species regarding intrinsic water use efficiency under the specific tidal flooding regime of mangrove forests. About the plant’s response to local environment influence, inverse correlations between all δ¹³Cn-alkanes values (δ¹³C₂₇, δ¹³C₂₉, δ¹³C₃₁, δ¹³C₃₃ and δ¹³CWA) and mean annual precipitation were found for the A. schaueriana samples. For the R. mangle species, a relationship between ACL25-35 and mean annual potential evapotranspiration and between CPI24-36 and mean annual temperature were observed. The different molecular and isotopic footprints of the three mangrove species presented here have potential to be used in future interpretations of n-alkanes as biomarkers in biogeochemical and paleoclimate studies near mangrove-dominated coastal regions.
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Quantifying Microplastics in Complex Environmental Samples: Py-Gc/Ms vs. Hyperspectral Ftir – Potential and Limitations
Authors S. Primpke, M. Fischer, C. Lorenz, G. Gerdts and B. Scholz-BoettcherSummaryIn a proof of principle, FTIR and PY-GC/MS are applied subsequently on identical filter for microplastics identification and quantification. Both approaches are of complementary scientific value since they result in particle numbers and sizes or polymer masses, respectively. Although the combined use of both methods is ideal, the transferability of particle related data, by far more referred in literature, into masses is an often-asked question.
The filter represented different complex environmental samples (waters from wastewater treatment plants, North Sea sediments and water) prior treated for selective MP pre-concentration. Associated with data evaluation, a general harmonization step regarding distinct polymer clusters of both methods was performed. A comprehensive data comparison revealed that FTIR and Py-GC/MS resulted in polymer types and qualitative distribution. This is attributed mainly to the size-influenced detection of both methods resulting in deviant quantitative calculations. The determined polymer mass is increasing with particle size. Consequently, the impact of few big particles is high regarding relative calculations for Py-GC/MS. In contrast, an inverse effect occurs in FTIR since particle counts ascend with decreasing particle size. Any calculative might lead to overestimation. A complementary use of both methods is highly recommended for reliable data generation.
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Evolution of Organic Matter Using Rock-Eval® Pyrolysis in Beech Forest Soils After Their Particle Size-Fractionation
Authors D. Sebag, E. Verrecchia, I. Kowalewski, T. Adatte, M. Aubert, G. Cailleau, T. Decaëns, J. Trap, F. Bureau and M. HeddeSummaryThis study presents the evolution of organic matter content using Rock-Eval® pyrolysis in Beech forest soils after their particle Size-fractionation. The amount of C in soil depends in microbial and physicochemical interactions between various biomass affecting its accumulation and its stability. As far as thermal stability of soil OM is supposed to mimic its biogeochemical stability, Rock-Eval® pyrolysis method is an efficient tool to quantify the organic and mineral carbon. To this end, litter and topsoil samples from a beech forest located in Normandy (France) were selected and fractionated by sieving from large debris to A-fine fractions. The TOC decreases from large debris to A-medium and drops in A-fine. Thermal stability inputs are highlighted through RE parameters when comparing litters and particle size fractions separated from topsoil samples (increase of TpS2 and OI, decrease of HI with decreasing fraction size in A horizons). Three distinct thermal stability C pools are identified
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Non-Pyrogenic Formation of Condensed Aromatic Compounds in Iron-Rich Environments
Authors P. Hatcher, A. Goranov and H. ChenSummaryExamination of wood decking that has been subjected to environmental change for about a decade in contact with Fe nails in the absence of sunlight shows significant modification due to active Fenton chemistry. The wood is blackened and the analysis of benzenepolycarboxylic acids shows that polycondensed aromatic molecules, commonly associated with black carbon from pyrogenic sources, are formed from the lignin abiotically and without pyrolysis. Because this transformation process occurs globally in soils, these results indicate that black carbon found globally in soils and other natural environments may not be exclusively from pyrogenic sources and that Fenton oxidation of wood is capable of producing black carbon. Such a finding will have an impact on the validity of global estimates of pyrogenic black carbon inputs to the environment.
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A Closer Look at 15N in Relation to Climate Change: Example from the California Current System
Authors Z. Erdem, P. Riekenberg, M.T.J. Van der Meer, N. Ohkouchi, N. Ogawa and D. RushSummaryThe nitrogen isotopic ratio of bulk sedimentary organic matter (δ¹⁵Nsed) has been an important tool to investigate biogeochemical dynamics in relation with the climate change. However, its signal could be altered during sinking and burial processes. In past decades new approaches were introduced in paleo-N investigations including compound-specific analysis. In this study, we present results of two approaches; N-isotopes of individual chlorophyll-derivatives (δ¹⁵Nchl) as well as amino acids (δ¹⁵NAA), to a sedimentary record collected from offshore California (ODP Site 1012). The region is characterized by strong upwelling in the surface, enhanced oxygen limitation, and denitrification in the subsurface waters, thus a suitable location to test these proxies. Here, we present the δ¹⁵Nsed and δ¹⁵NAA results covering the first 120 kyr whereas δ¹⁵Nchl measurements are covering the last 22 kyr of the record. The overall δ¹⁵NAA trend is following the δ¹⁵Nsed throughout the record with more-or-less stable offset as well as the interglacial-glacial variability suggesting that the nitrogen dynamics offshore California is mainly driven by climatic forces over time. At specific periods, compound-specific ¹⁵N divert from δ¹⁵Nsed suggesting more local changes and/or isotopic alterations.
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A Geochemical Context for Stray Gas Investigations in the N. Appalachain Basin: An Update of Analyses of Natural Gases
Authors F. Baldassare and E. ChapmanSummaryNatural gas production in the Marcellus Formation in NE Pennsylvania, USA has matured in the Northern Appalachian Basin. Our evaluation of time-series gas geochemistry data provides additional insight into the complexities of gas origin and migration.
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