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30th International Meeting on Organic Geochemistry (IMOG 2021)
- Conference date: September 12-17, 2021
- Location: Online
- Published: 12 September 2021
121 - 140 of 279 results
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Car and Truck Tire Wear Particles in Environmental Samples –A Comparison With “Traditional” Microplastic Mass Loads
Authors I. Goßmann, M. Halbach and B.M. Scholz-BöttcherSummaryTire wear particles (TWP) are assumed to be the most dominant source of microplastics (MP). In environmental samples TWP particles occur as heteroaggregates with road material and particles. Combined with their variable composition both points lead to the fact that reliable determination methods for TWP are rare.
Therefore, identification and quantification of TWP was implemented in an existing pyrolysis-gas chromatography-mass spectrometry (Py-GC/MS) method for MP determination. The resulting TWP mass loads were compared to “traditional” MP shares. The latter included polymers such as PE, PP, PS, PET and PVC.
The widely held belief of TWP being the most dominant source of MP applies to sites in direct vicinity to TWP sources, only. An increasing distance to these sources leads to a decrease in TWP concentration in respective environmental samples. This points to a low long-distance transport potential of TWP compared to “traditional” MP which occurred ubiquitous.
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Modes of Soil Organic Carbon Sequestration and Carbon Use Efficiency Determined by Soil Aeration Status
Authors T. Meador, J. Niedzwiecka, S. Jabinski, T. Picek, R. Angel and H. ŠantrůčkováSummaryMicrobes regulate key ecosystem functions and global estimates of microbial activity in any habitat invoke on one or more scaling factors, including cell abundance, size, carbon content, and carbon use efficiency (CUE). Choice of CUE can sway C flux estimates by approximately one order of magnitude and propagate high uncertainty into global C budgets. Moreover, microbial CUE studies have focused on aerobic metabolisms and must still address the intensifying hydration-desiccation cycles that alter soil aeration status and prevalent anaerobic microniches in soils, where terminal electron acceptors such as iron may influence CUE. Here we employed a stable isotope labeling approach to follow the fate of ¹³C-glucose amended to two forest soils (100 μmol g-1; AT% = 3) with varying iron content and incubated under different oxygen levels, taking multiple channels of C assimilation into account.
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Formation of liquid hydrocarbons in bituminous coals: Natural observations and experiments
Authors L. Zieger, R. Littke and C. Hartkopf-FröderSummaryThe potential of forming liquid hydrocarbons for Pennsylvanian bituminous coals from Germany was studied, combining a set of organic-petrological and organic-geochemical methods as well as pyrolysis experiments.
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STRUCTURAL VARIATION AND PROVENANCE OF SULFUR-RICH ORGANIC MATTER IN NÖRDLINGEN POST-IMPACT SEDIMENTS
More LessSummaryThe Nördlinger Ries crater in southern Germany was formed by a meteorite impact 14.6±0.2 Ma ago and contains a sequence of Miocene post-impact lacustrine sediments. A suite of bulk rock and kerogen samples from exploration well Nördlingen-1973 (18–260 m depth) has been analysed in terms of bulk geochemical composition, organic petrology, online Curie Point-pyrolysis gas chromatography-mass spectrometry and attenuated total reflectance Fourier-transform infrared spectroscopy for getting insights into the chemical composition and structural evolution of the kerogen up the sedimentary sequence in relation to sources for organic matter.
The results show that hydrogen- and sulphur-rich kerogen prevails in the post-impact sediments, having abundant aliphatic and thiophenic constituents, which is proved by high H/C (1.6 on average), intensive aliphatic CH stretching vibration bands at 2700–3000 cm-1 in ATR FT-IR spectra, abundant aliphatic and thiophenic pyrolyzates. The OM mainly originates from algal and microbial material as suggested by prominent n-alkane/-alkene doublets and iso-alkanes. Type III kerogen occurs in the uppermost unit, containing more aromatic and phenolic constituents with abundant phenolic and aromatic pyrolyzates, in which OM is partly of higher land plant origin with ample vitrinite and inertinite particles.
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Seasonal to Decadal Sea Surface Temperature Changes During the Younger Dryas/Holocene Transition in the Tropics
Authors L. Wörmer, J. Wendt, B. Boehman, G. Haug and K. HinrichsSummaryWe explored how the Younger Dryas (YD)/Holocene transition impacted tropical sea surface temperature (SST) by evaluating marine sedimentary archives at scales unattainable for conventional molecular stratigraphy. In sediments from the Cariaco Basin, we analysed the well-established UK’37 SST proxy via mass spectrometry imaging, and obtained 2D-images of sedimentary proxy distribution at 100 µm resolution and corresponding downcore SST profiles with subannual resolution.
SST in the Cariaco Basin remains relatively constant over the YD/Holocene transition, suggesting a decoupling from the major environmental change associated to this event, i.e. the northward shift of the intertropical convergence zone. However, we were able to reveal a short-lived ∼50 year episode of abrupt warming during which average SST increased about 1°C. This episode is synchronous with the Preboreal Oscillation cooling, that led to drier, colder conditions in Europe and North America.
The comparison of proxy values, elemental composition and sediment colour from every µm-sized spot further provides clues on SST seasonality and its modulation across the YD/Holocene transition.
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Sedimentary Branched Tetraethers in an African Lake Record 170 KYR of Tropical Temperature Change: Assessment of Calibrations
Authors A. Baxter, F. Peterse, D. Verschuren and J. Sinninghe DamstéSummaryIn order to improve our understanding of Earth’s climate history, proxies that accurately reconstruct past temperatures are needed. The distribution of branched glycerol dialkyl glycerol tetraethers (brGDGTs), the membrane lipids of certain bacteria, is correlated to temperature in modern settings, and therefore is at the basis of several paleothermometers. Here we apply several brGDGT based temperature calibrations developed specifically for lakes to the sediment sequence from Lake Chala, in equatorial East African, to generate temperature records which cover the last 170 kyr in unprecedented high temporal resolution (210 years on average). Surprisingly, application of the recently developed East African lake calibration leads to ambiguous results. By contrast applying a calibration created before the discovery of 5- and 6-Me brGDGT isomers produces a temperature record strongly reminiscent of established climate records such as the isotope records from Antarctica and contains periodicities relating to orbital precession and obliquity. Therefore it appears that 6-Me brGDGTs are key to the temperature signal archived in Lake Chala. In Lake Chala today, 5- and 6-Me brGDGTs generally occupy different parts of the water column, and thus their relative abundance may be indirectly related to temperature through changes in lake depth or seasonal mixing.
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Polymer Characterization by the Rock-Eval® Device for Identification of Plastics in Sediments
Authors M. Romero-Sarmiento, H. Ravelojaona, D. Pillot and S. RohaisSummaryIn this work, artificial thermal degradation experiences using the Rock-Eval® device were performed on selected polymer microsphere samples. The main idea of this work is to create a database of different polymer standard responses (PE, PE100, PA6, PA11, PFA and PET) using the specific Rock-Eval® FID peak signals. This study attends to demonstrate if this quick thermal degradation method can be also used to characterize the plastic contents (detection, type, quantity) in sedimentary samples
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PAIRED SUB-ANNUAL BIOMARKER AND ELEMENTAL CLIMATE PROXIES REVEAL MONTHS OF CLIMATE SIGNAL INTEGRATION IN THE ARABIAN SEA
Authors T. Napier, L. Wörmer, J. Wendt, A. Lückge and K. HinrichsSummaryLaminated Pakistan Margin (northeastern Arabian Sea) marine sediments provide excellent, continuous archives of past climate conditions that can be used to reconstruct the variability of the Southwest (summer) and Northeast (winter) monsoons of India. Sea surface temperatures (SSTs) were reconstructed using UK'37 and CCaT proxies, with a resolution of 0.1-year. Both proxies reconstruct reasonable SSTs compared to the instrumental range, but neither proxy captures the full ∼6°C annual cycle. However, there is coherence on interannual to decadal timescales between instrumental SSTs and proxy-derived SSTs, indicating the proxies capture the same climatic cyclicity as instrumental SSTs. In particular, the UK'37 and instrumental SSTs have similar interannual to decadal trends, which is apparent when comparing UK'37 SSTs with an 11-month moving mean of the instrumental SSTs. The proxy SST signal is a temporal integration of SSTs from up to several months. We posit that this may be linked to variable sinking flux throughout the year. The sinking flux of these organisms increases during periods of high productivity (spring-summer, winter) or high lithogenic flux. These organisms likely remain in suspension when sinking flux is low, which may last several months; subsequent aggregation then integrates their SST signals.
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Occurrence of Human-Excreted Contaminants Within a Decantation Tank: A Clue of Their Historical Consumption?
Authors T. Thiebault, L. Fougère, A. Simonneau, E. Destandau, C. Le Milbeau and J. JacobSummaryThis study investigated the occurrence of drug target residues (DTR) in a decantation tank. This installation trapped the coarse fractions of a unitary sewer system, collecting both stormwater and wastewater. While this 17 m deep underground building could constitute a nonesuch opportunity to study the historical evolution of illicit and licit drug consumption in the catchment, the deposition processes and the record of DTRs remain largely unknown at present. Five cores were acquired from 2014 to 2017. 152 sediment samples were extracted using a mixture of water:methanol (1:1) prior to the DTRs quantification in the extracts. Several classical sedimentological analyses such as total organic carbon, facies description and granulometry were also performed on these samples, in order to understand the most important factors impacting their deposition.
The key-role of the speciation of DTRs was highlighted by the higher contents in neutral and anionic DTRs in organic layers, whereas only cationic DTRs were found in mineral layers. The considerable modifications in the sediments’ properties are therefore the most important driver impacting their DTR concentrations in decantation tank sediments. Further research remains necessary to fully understand the deposition process, but this study provides new clues explaining these temporal evolutions.
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New Insights into Microbial Wax Ester Biosynthesis, Natural Occurrence and Adaptive Role
By G. VincentSummaryWax esters (WE) are a major class of storage lipid compounds synthesized by bacteria in which they can have different physiological functions. So far, the potential for WE biosynthesis by prokaryotes has been mostly investigated in aerobic bacteria, and this metabolic capacity is considered not to have arisen in archaea. Additionally, the use of WE in geochemical and environmental studies has been overlooked due to their apparent rapid hydrolysis during early diagenesis. However, some reports have documented a possible formation of WE by facultative or phototrophic anaerobic bacteria, and WE have been reported in up to 40,000 years old lacustrine sediments, suggesting their possible formation in anoxic environments and preservation in the geological record under adequate conditions. Here, we present a combination of recent laboratory and field studies demonstrating that WE can be biosynthesized in various anoxic environments by several families of anaerobic bacteria and that such storage lipids may be specifically important for some microbial communities to survive in environments experiencing harsh environmental conditions. Our data also describe original interactions between abiotic and biotic processes that can occur during OM diagenesis and show that WE can constitute an interesting molecular tool to decipher carbon transformation pathways in the geosphere.
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Lake Dziani Dzaha (Mayotte, Indian Ocean): A Modern Analogue for Type I Kerogen Formation
Authors I. Jovovic, V. Grossi, P. Adam, M. Ader, F. Baudin, I. Antheaume, D. Jézequel, F. Arnaud, E. Malet, E. Bard, M. Capano, L. Simon, S. Mignard, P. Cartigny and F. GelinSummaryIn the past, highly productive (hyper)saline and alkaline environments have proved propitious for large accumulation of sedimentary OM that led to the formation of Type I kerogens, such as those of the Green River Formation.
A sediment core that covers most of the history of Lake Dziani Dzaha, a hypereutrophic saline, alkaline and mostly anoxic crater lakewhich waspostulatedto be a modern analogue of such environments, has been investigated using several analytical approaches comprising bulk (Rock-Eval and C, N, S elemental analyses), isotopic (δ13,14C, δ15N, δ18O, δ33,34,36S), and sedimentological descriptions.
This study revealed that, despite strong environmental changes undergone by the lake since its formation, the conditions prevailing in the lake supported by a continuous high primary production have led to an excellent preservation of OM and to early diagenetic reductive and sulfurization processes which have yielded an exceptionally reduced character of the OM with respect to its short diagenetic history (< 6 ky).
The similarities observed between the sediments of Lake Dziani Dzaha and some source rocks associated to Type I kerogens suggest that early diagenetic processes can have a strong and rapid impact on the accumulation of OM in some (semi)closed and highly productive aquatic ecosystems.
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Role of Ecosystem Engineers on the Organic Matter Characteristics in the Northern Intertidal Zone of the Seine Estuary (Nw France)
Authors A. Huguet, J. Morelle, C. Anquetil, M. Sourzac, K. Judith, J. Lebrun-Thauront, J. Maubert, F. Orvain and E. ParlantiSummaryIntertidal zones have a key ecological role in estuaries. The area covered by the intertidal mudflats in the Seine estuary (NW France) was divided by 3 over the last centuries. The preservation of these areas is a priority but requires a detailed understanding of their functioning. The latter is complex and notably depends on the presence and activity of benthic macrofauna, which can act as ecosystem engineers, strongly affecting the other organisms.
The aim of this study was to assess the influence of the two predominant ecosystem engineers in the Seine Estuary mudflats (Hediste diversicolor and Scrobicularia plana) on the dissolved and sedimentary organic matter (OM) quality. The role of the ecosystem engineers on the quality of the sedimentary OM was evaluated through the analysis of complementary lipid biomarkers. The characteristics of the dissolved OM (DOM) from the corresponding interstitial waters were concomitantly determined by spectroscopic analyses.
Even though it was shown that H. diversicolor and S. plana play a major role on the microphytobenthos dynamics, the seasonality was shown to have a more pronounced effect on the sedimentary OM characteristics than benthic organisms. In contrast, the DOM was suggested to be sensitive and reactive to the ecosystem engineer activities.
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APPLICABILITY OF INFRARED ALIPHATIC STRETCHING REGION FOR CHARACTERISATION OF OILS OF THE SAME GENETIC TYPE
Authors J. Stevanovic, A. Rakitin and K. StojanovicSummaryThe work focuses on the applicability of infrared (IR) aliphatic stretching region for characterisation of oils of the same genetic type. Paraffinic oils (56 samples) from the Turija-Sever oil field were studied. The oils are similar originate from mixed aquatic/terrestrial sources and were generated from Tertiary source rocks in an early stage of oil window. However, slight differences among the oils were observed. They are reflected in a higher contribution of algal organic matter (OM) to the group I oils formed in more reducing environment (western part of the field), compared to the oils from eastern part (group II). The IR CH2/CH3 branching factor segregates oils into two identical groups (I and II) established based on biomarkers and aromatic hydrocarbons. The group I oils showed lower values of CH2/CH3 factor than group II oils. Enhanced CH2/CH3 ratio for group II oils indicate that in the case of uniform maturity greater average length of polymethylene fragments results from a higher content of long chain n-alkanes signifying an increased impact of terrigenous OM (land plant waxes). Correlation between the normal to isoprenoid alkanes sum ratio and the CH2/CH3 factor is useful for detecting slight differences between oils of the same genetic type.
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Subsurface Lithoautorophy Revealed Through Unique Biomarker Distributions and Compound-Specific Carbon Isotopes
Authors M. Selensky, A. Masterson, J. Blank, S. Lee and M. OsburnSummaryThe shallow subsurface spans the transition between the deep subsurface and surface biospheres. Microbial communities in the subsurface are known to subsist on organic carbon transported from the surface and/or carbon fixed in situ via chemolithoautotrophy. However, the relative balance between these two sources is unknown. Cave environments fortunately present opportunities to directly interrogate shallow subsurface microbial ecology. Here, we explore the lipid biomarkers and carbon sources used by microbes in the lava caves of Lava Beds National Monument, CA, USA. To accomplish this, we extracted intact polar lipid (IPL)-derived fatty acids from cave biofilms, speleothems, and surface soils. We observe 127 discrete compounds in total, including 36 branched isomers. Whereas soils are dominated by straight-chain fatty acids and dicarboxylic acids, bacterial branched and trans-unsaturated fatty acids are particularly abundant in cave biofilms. Compound-specific stable carbon isotope analysis (CSIA) revealed very negative δ13C values in such biofilm fatty acids (down to −47.8‰ vs. VPDB). By comparing these values to the isotopic compositions of dissolved organic (−29.8 +/− 2.0‰) and inorganic carbon (−6.0 +/− 1.9‰) in water entering the caves as drips, we infer that biofilm microbes source a significant portion of their biomass from in situ fixation of previously-respired carbon.
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Subsurface Microbial Communities Utilise a Wide Range of Aromatic Compounds in Anoxic Coal Seams
Authors B. Campbell, S. Gong, P. Greenfield, D. Midgley, I. Paulsen and S. GeorgeSummaryCoal bed methane is a key source of energy in the transition from fossil fuels to renewables. Although a large proportion of this methane is generated via subsurface biological processes, little is known about the degradation pathways and microbial communities responsible. Previous literature has identified many of the microbial communities present in methane-producing coal seams and speculated as to which of these microbes are responsible for possible coal-to-methane degradation processes in situ.
Anoxic microcosms were established with a range of different monoaromatic and polyaromatic compounds as sole sources of carbon. These microcosms were inoculated with a coal seam microbial community sourced from a methane-producing well in the Surat Basin, Queensland, Australia. After incubation, community amplicon sequencing of the 16S rRNA gene revealed the identities of microbes that increased in relative abundance on each of the aromatic substrates. Putative degradation pathways for the substrates were hypothesized, along with which microbes are likely to be active in different parts of the degradation pathways, based on both these analyses and pre-existing literature on anaerobic degradation of aromatic compounds from non-coal environments.
This research provides valuable insights into the catabolism of organic matter in coal in situ.
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Fires Support Biome Shifts in E Siberia? Interglacial Fire-Vegetation-Climate Feedbacks Reconstructed from MIS-11-Sediments of Lake El’gygytgyn
Authors E. Dietze, A. Andreev, K. Mangelsdorf, M. Theuerkauf, C. Kraamwinkel, M. Melles, H. Meyer, T. Tessendorf, V. Wennrich and U. HerzschuhSummaryThe ongoing spread of forest fires in the Siberian Arctic raises concerns on how far increasing temperatures and fire occurrence lead to biome shifts from tundra to summergreen or evergreen boreal forest. Here, we investigate vegetation and fire regime shifts during late MIS 12 and MIS 11 c. 390–430 kyrs ago using sedimentary charcoal, anhydrosugars and pollen from Lake El'gygytgyn, NE Siberia. We find different types of centennial-to-millennial-scale biome shifts, partly accompanied by fire regime shifts. We assess the role of fire in driving and/or responding to biome changes, especially periods of abrupt warming, to gain understanding of what we can expect during the ongoing warming of the high-northern latitudes.
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Application of Mc-Icp-Ms Method for Sulfur Isotopic Analysis in Reservoir Rocks
Authors B. Gareev, G. Batalin and A. ChugaevSummaryWe have developed a technique for determination of 34S/32S isotopic ratio in pyrite using multiple-collector inductively coupled plasma mass-spectrometer NEPTUNE PLUS equipped with J-interface and desolvating nebulizer sample injection system (Aridus II). This configuration of the NEPTUNE PLUS, as well as a high-resolution mode, made it possible to significantly reduce (>10000 times) major isobaric interferences by 32 mass from O2+. For mass bias correction, standard-sample bracketing was applied.
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Decadal Sea Surface Temperature Variability in the Eastern Mediterranean During the Last Interglacial
Authors I. Obreht, D. De Vleeschouwer, L. Wörmer, M. Kucera, D. Varma, M. Prange, T. Laepple, J. Wendt, S.D. Nandini-Weiss, H. Schulz and K. HinrichsSummaryUnderstanding the climate variability from geological periods with warmer-than-present climate is of great relevance for understanding the climate of the future warmer world. The Last Interglacial (LIG; ∼130,000 to 116,000 years ago) is the most recent geologic period with warmer-than-present climate, where climate reconstructions from the LIG provide an opportunity to evaluate climate variability from a warmer world. However, conventional analytical methodology applied on classical geological archives does not provide access to information on annual and decadal patterns of climate variability. In this study, we apply novel analytics on a unique marine geological archive to generate the first annually to subdecadally resolved continuous millennial-scale record indicative of Earth's climate variability during the last warmer-than-present interglacial. We will examine the naturally occurring cyclicity and variability of sea surface temperature and constrain the rate of SST change on decadal to centennial time-scales in the warmer-than-present LIG in the Eastern Mediterranean.
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Impact of Oxyegn Level on the Distribution of Branched Tetraethers in Soil Profiles
More LessSummaryThe influence of oxygen level on brGDGT-based proxies was evaluated by studying GDGTs in three soil profiles with contrasting oxygen level.
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Realizing the Full Potential of Lipidomics: A New Protool for an Improved Extraction of the Intact Polar Lipids of Archaea
Authors T.W. Evans, F.J. Elling, Y. Li, A. Pearson and R.E. SummonsSummaryThe investigation of intact polar lipids (IPLs) is a powerful tool for investigating the physiology of Archaea in cultures and their prevalence in environmental samples. IPLs are typically extracted using the Bligh and Dyer protocol. However, recent studies have exposed both, bias and a low extraction efficiency for archaeal lipids obtained by this technique. Here, we tested different solvent mixtures, mechanical rupture techniques and chemical detergents/enzymatic lysis buffers for their potential to destroy the cell envelope and thus increase the extraction efficiency of archaeal IPLs in pure cultures and environmental samples. The tests with different solvent mixtures revealed highest IPL yields when samples were extracted with a monophasic solvent system that included a trichloroacetic acid buffer. Freeze-thaw cycles prior to the extraction after Nishihara and Koga (1987) enhanced the extraction efficiency by 1.7-times, while other investigated mechanical rupture techniques (bead beating and osmotic shock) showed no increase. The use of chemical detergents in combination with freeze-thaw cycles resulted in significantly higher IPL yields than the experiments without the pre-treatment.
The results demonstrate that the novel protocol results in significantly higher archaeal IPL abundances than the Bligh and Dyer protocol, suggesting that earlier studies may have overlooked the majority of IPLs.
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