Organic Geochemistry最新文献

{"title":"Geochemical fingerprints of Dongpu Depression crude oils in Bohai Bay Basin, northern China: Insights from biomarkers and isotopic compositions of selected alkylnaphthalenes and alkylphenanthrenes","authors":"N’Guessan Francois De Sales Konan ,&nbsp;Meijun Li ,&nbsp;Youjun Tang ,&nbsp;Erfan Mohammadian ,&nbsp;Bo Liu ,&nbsp;Andre Hyacinth Latyr Tine ,&nbsp;Lukman Adesina Olayinka ,&nbsp;Zhejun Pan","doi":"10.1016/j.orggeochem.2024.104845","DOIUrl":"10.1016/j.orggeochem.2024.104845","url":null,"abstract":"<div><p>The Dongpu Depression is a rift lake in the Bohai Bay Basin of eastern China, where abundant oil and gas resources were discovered. Previous geochemical investigations of Dongpu Depression oils have revealed a notable lack of data regarding the isotopic compositions of individual polycyclic aromatic hydrocarbons (PAHs) from the discovered Cenozoic crude oils. Using gas chromatography-mass spectrometry (GC–MS) and gas chromatography-isotope ratio mass spectrometry (GC-IRMS), a novel approach combining molecular parameters and stable carbon isotope compositions of individual PAH was applied to study the depositional environment conditions, the different source inputs, the maturation stage and to identify the potential family of five crude oils selected from Dongpu Depression.</p><p>A decrease of Ga/C₃₀H together with low Pr/Ph ratios and changes in isotopic compositions indicate that the five Dongpu Depression oils were derived from OM deposited in an anoxic saline environment with a stratified water column where mixing of saline water and freshwater occurred. The low isoprenoid, tricyclic and tetracyclic terpane ratios in combination with the δ¹³C values of 1,6-DMN, 1,2,5-TMN, 1,3,6,7-TeMN, 9-MP and 1-MP attest that their sources have a mixed origin with high aquatic organism (planktonic) input and a lower land plant (C₃ plant) contribution. The δ¹³C values of phenanthrene between −30.0 ‰ and −20.0 ‰ indicate that the studied Dongpu Depression oils belong to a single family generated from the peak to the late oil generation stage (Rc-TNR-2 between 0.85 and 1.15 %). A correlation with various basins indicates that oil samples featured by δ¹³C values of Phen between −30.0 ‰ and −20.0 ‰ correspond to crude oils derived from mixing of aquatic and high plant contributions with different degrees of mixtures, which have not yet reached their cracking stage (Rc &lt; 2.0 %). Crude oils from the Carboniferous and Mesozoic-Cenozoic Tarim rocks, Australian petroleum systems, Termit Basin, Bongor Basin, Fushan Depression and the studied Dongpu Depression oils belong to that group of oils. Crude oils characterized by lighter phenanthrene isotopic compositions (δ¹³C values of Phen &lt; −30.0 ‰) are mainly derived from marine/aquatic input and have already entered the cracking window (Rc &gt; 2.0 %). This group of oils is represented in this study by the Cambrian-Ordovician Tarim Basin oil samples. The research shows the importance of the aromatic isotopic compositions in petroleum system characterization and could be used as a reference for a practical exploration campaign of petroleum.</p></div>","PeriodicalId":400,"journal":{"name":"Organic Geochemistry","volume":"195 ","pages":"Article 104845"},"PeriodicalIF":2.6,"publicationDate":"2024-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141883036","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Computational analysis of the thermodynamic stability and isomeric composition of cholestane","authors":"Yuki Nukumi ,&nbsp;Hirofumi Sato ,&nbsp;Ryosuke Saito ,&nbsp;Masahiro Higashi","doi":"10.1016/j.orggeochem.2024.104841","DOIUrl":"10.1016/j.orggeochem.2024.104841","url":null,"abstract":"<div><p>Cholestane is produced by diagenesis of cholesterol in the geosphere being known to have four main stereoisomers. The abundance ratios of these stereoisomers are important indicators of the geospheric thermal history. However, it has been unclear whether the isomeric ratios are caused by kinetic or thermodynamic dominance. In this study, we analyzed the isomeric ratios of cholestane under thermodynamic dominance using the density functional theory. The calculated isomeric ratios are in good agreement with the limit values in the geosphere, indicating that the isomeric ratios in the geosphere can be obtained under thermodynamic control. We also discussed the factors contributing to their stabilities.</p></div>","PeriodicalId":400,"journal":{"name":"Organic Geochemistry","volume":"195 ","pages":"Article 104841"},"PeriodicalIF":2.6,"publicationDate":"2024-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141883038","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Soil chemistry effect on GDGT abundances and their proxies in soils of the Okavango Delta","authors":"Julie Lattaud ,&nbsp;Mangaliso J. Gondwe ,&nbsp;Marco Griepentrog ,&nbsp;Carole Helfter ,&nbsp;Cindy De Jonge","doi":"10.1016/j.orggeochem.2024.104847","DOIUrl":"10.1016/j.orggeochem.2024.104847","url":null,"abstract":"<div><p>Branched and isoprenoid glycerol dialkyl glycerol tetraethers (brGDGTs, and isoGDGTs) are two families of membrane lipids commonly used to reconstruct paleo-environmental parameters. Their use as a quantitative proxy for past temperatures has been hindered by the discovery of other environmental controls on their distribution in soils, such as changes in bacterial community composition, chemistry and aridity. To test for the impact of aridity-driven soil chemistry changes, GDGT concentrations and derived proxies were measured in 43 soils along a chemical gradient in the Okavango Delta. All brGDGT concentrations increase with decreasing pH. Alkalinity-promoted (6-methyl and cyclopentane-containing) brGDGTs show a secondary concentration increase in arid soils, characterized by a high pH&gt;8 and cation exchange capacity (CEC&gt;30 cmolc kg⁻¹). The concentration of 5-methyl brGDGTs increases faster that of 6-methyl brGDGTs in arid compared with non-arid soils. Although limited variability in temperature is present (∼2 °C), significant variation in MBT′_5ME values is observed (0.63–0.96) likely driven by the variation in CEC. IsoGDGTs are present in lower concentrations than brGDGTs, and Ri/b values, a potential proxy for paleohydrological reconstruction, correlating with soil water content (r = 0.45, p &lt; 0.01). TEX₈₆ values (0.57–0.97) correlate with pH across the aridity transect. In this region, where accurate proxies and quantitative paleostudies are scarce, the impact of aridity-driven chemistry changes on GDGT-proxies is shown, i.e., MBT′_5ME is overall controlled by CEC, but correlates negatively with pH in non-arid soils and with IR_6ME in arid alkaline soils. Furthermore, we propose GDGT-based proxies for concentration in exchangeable calcium, past hydrological changes and soil pH.</p></div>","PeriodicalId":400,"journal":{"name":"Organic Geochemistry","volume":"195 ","pages":"Article 104847"},"PeriodicalIF":2.6,"publicationDate":"2024-07-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0146638024001128/pdfft?md5=34ba9059d03692184680790b11c7e28f&pid=1-s2.0-S0146638024001128-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141935211","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Geochemical analysis of bituminous samples from the Pre-Pottery Neolithic B site of Nahal Efe (Northern Negev, Israel): Earliest evidence in the region and an example of alteration of the Dead Sea bitumen","authors":"Jacques Connan ,&nbsp;Ferran Borrell ,&nbsp;Jacob Vardi ,&nbsp;Samuel Wolff ,&nbsp;Steven M. Ortiz ,&nbsp;Michael Engel ,&nbsp;Renaud Gley ,&nbsp;Alex Zumberge","doi":"10.1016/j.orggeochem.2024.104844","DOIUrl":"10.1016/j.orggeochem.2024.104844","url":null,"abstract":"<div><p>Thirty-six bituminous samples from the Pre-Pottery Neolithic site of Nahal Efe (8000–7700 cal. BCE, Negev, Israel) were analysed to determine their origins. Most samples are mixtures of bitumen with minerals, predominantly quartz, calcite, dolomite and aragonite. The aragonite is from marine shells, which were crushed to be incorporated into the mixtures.</p><p>Dead Sea bitumen was identified in all samples. The Nahal Efe geochemical data were compared to samples from Tell Yarmuth (2800–1100 BCE), Tall Dhiban (700–800 cal. BCE), Tel Gezer (1250–700 cal. BCE) and to floating asphalt blocks from the Dead Sea. The stable carbon isotope values of resins and asphaltenes of the Nahal Efe bitumens differ from those of the Dead Sea floating blocks, Tell Yarmuth, Tel Gezer and Tall Dhiban, apparently a consequence of diagenesis. Thus, δ¹³C values of asphaltenes may not always be a reliable representative of the stable carbon isotope composition of the unaltered source bitumen. Surprisingly, the sterane and terpane patterns of the Nahal Efe samples are not severely biodegraded and clearly indicate a Dead Sea bitumen source. No difference was recorded between mixtures and pure bitumen. Some changes have, however, been observed when using quantitative data on biomarkers. The shifts in δ¹³C values of resins and asphaltenes is not related to biodegradation but rather to oxidation of the Nahal Efe samples.</p><p>This is the earliest and most complete evidence of Dead Sea bitumen exploitation and use, which included the preparation of different ‘recipes’, in the Negev and Sinai arid regions.</p></div>","PeriodicalId":400,"journal":{"name":"Organic Geochemistry","volume":"195 ","pages":"Article 104844"},"PeriodicalIF":2.6,"publicationDate":"2024-07-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0146638024001098/pdfft?md5=3e72c4c602ee6c1f5b59c4e06a61f000&pid=1-s2.0-S0146638024001098-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141883149","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Comparison of dissolved organic matter composition from various sorbents using ultra-high resolution mass spectrometry","authors":"Oriane M. Yvin ,&nbsp;Martin R. Kurek ,&nbsp;Amy M. McKenna ,&nbsp;Jon R. Hawkings ,&nbsp;Robert G.M. Spencer","doi":"10.1016/j.orggeochem.2024.104846","DOIUrl":"10.1016/j.orggeochem.2024.104846","url":null,"abstract":"<div><p>Solid phase extraction (SPE) of a variety of diverse dissolved organic matter (DOM) endmembers through eight commercially available sorbents was examined (ENV, PLEXA, PPL, HLB, Isolute 101, C18/ENV+, C18, Envirelut) representing styrene divinylbenzene polymer (SDVB) and silica-based sorbents. We assessed dissolved organic carbon (DOC) recovery and DOM composition via 21 T Fourier transform-ion cyclotron resonance mass spectrometry (FT-ICR MS). DOC recoveries and SPE-DOM composition differed more by endmember type than by sorbent. Silica-based sorbents retained DOM with many N-containing formulae, while SDVB-based sorbents retained DOM with more S-containing formulae. Extraction pH exerted a greater influence on DOM composition, notably through the presence of strong groupings composed of saturated and lowly oxygenated formulae at basic pH, and of aromatic and highly oxygenated formulae at pH 2, irrespective of endmember or sorbent. There was above 25% DOC recovery, regardless of sorbent or endmember; &gt;90% of the relative abundance (RA) of molecular formulae were shared with PPL, which is currently the most commonly utilized sorbent for DOM. This clearly highlights the ability of the selected sorbents to retain representative DOM across diverse endmembers. Such findings may be useful for future targeted DOM studies (e.g., bioincubations, wastewater and drinking water applications) interested in focusing on specific compositional changes and will provide a better understanding of how organic carbon cycling is impacted by anthropogenic processes.</p></div>","PeriodicalId":400,"journal":{"name":"Organic Geochemistry","volume":"196 ","pages":"Article 104846"},"PeriodicalIF":2.6,"publicationDate":"2024-07-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141847694","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Fire-induced shifts in stalagmite organic matter mapped using Synchrotron infrared microspectroscopy","authors":"Liza K. McDonough ,&nbsp;Micheline Campbell ,&nbsp;Pauline C. Treble ,&nbsp;Christopher Marjo ,&nbsp;Silvia Frisia ,&nbsp;Jitraporn Vongsvivut ,&nbsp;Annaleise R. Klein ,&nbsp;Viktoria Kovacs-Kis ,&nbsp;Andy Baker","doi":"10.1016/j.orggeochem.2024.104842","DOIUrl":"10.1016/j.orggeochem.2024.104842","url":null,"abstract":"<div><p>Understanding organic matter (OM) in cave mineral deposits (speleothems) is essential for interpreting land use and climatic changes, and the incorporation of trace elements associated with organic compounds. However, the sources and composition of OM in speleothems are poorly understood due to challenges associated with measuring OM at low concentrations and the destructive nature of most speleothem OM analysis techniques. Synchrotron Fourier-transform infrared (FTIR) microspectroscopy is a promising non-destructive technique that can be used to investigate stalagmite OM composition. We use FTIR to analyse vegetation, soil, calcium carbonate and ash end-members and demonstrate the use of Synchrotron infrared microspectroscopy (IRM) mapping to detect temporal changes in the OM composition of a stalagmite from a shallow cave in south-west Western Australia. Our analysis reveals predominant FTIR peaks in the stalagmite linked to amides and CH₂ groups, suggesting potential microbial contributions, with smaller proportions of aromatic, CH₃ and C<img>O groups. High-resolution transmission electron microscopy revealed that this OM is likely hosted in sets of nanopores spaced hundreds of nanometers apart, aligned along calcite crystallographic orientations. Furthermore, we assess the impact of known wildfire events as discrete short term environmental changes on the stalagmite’s OM composition. The temporal variability in OM functional group composition after fires implies complex fire-soil-vegetation-microbial interactions. This research demonstrates the effectiveness of Synchrotron IRM mapping in providing insights into the short and long-term environmental influences on stalagmite OM composition. Expanding this research to other regions and climates could further enhance the interpretation of OM changes in speleothem-based palaeoclimate reconstructions.</p></div>","PeriodicalId":400,"journal":{"name":"Organic Geochemistry","volume":"195 ","pages":"Article 104842"},"PeriodicalIF":2.6,"publicationDate":"2024-07-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0146638024001074/pdfft?md5=d509225c9d8bbb039d5cf4ef34459fae&pid=1-s2.0-S0146638024001074-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141845564","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Large variability and 2H-depletion of Middle Miocene to Pleistocene alkenone hydrogen isotopes in the Equatorial Pacific reflect subsurface, low light haptophyte growth","authors":"Katrin Hättig ,&nbsp;Panteleimon Prokopiou ,&nbsp;Stefan Schouten ,&nbsp;Marcel T.J. van der Meer","doi":"10.1016/j.orggeochem.2024.104840","DOIUrl":"10.1016/j.orggeochem.2024.104840","url":null,"abstract":"<div><p>Hydrogen isotope ratios of haptophyte derived long-chain alkenones (δ²H_C37:2) have shown to be a useful tool for reconstructing past isotopic compositions of surface seawater (δ²H_SSW). The δ²H_SSW is related to global ice volume, sea surface salinity and the local hydrological cycle. Here, we present a hydrogen isotope record of alkenones spanning the last 14.5 Ma from IODP site U1338 in the east equatorial Pacific. The alkenone-based reconstructed δ²H_SSW is substantially more negative and variable than reconstructed δ²H_SSW based on published oxygen isotopes of coccolith carbonates. This suggests that factors other than the isotopic composition of seawater affect the hydrogen isotopic composition of alkenones. The relatively negative and highly variable δ²H_C37:2 values are in line with published modern observations on alkenones from suspended particulate matter in the equatorial and north Pacific, with the highest values at relatively high light conditions at the surface and the lowest values at higher water depth and relatively low light conditions. This suggests that the relatively negative and highly variable δ²H_C37:2 values in these Middle Miocene to Pleistocene sediments are likely derived from haptophytes growing below the sea surface under variable low light conditions. In regions where the contribution of alkenones from subsurface production, due to high subsurface nutrients, at low light intensities to the sediment is relatively high the δ²H_C37:2 has to be interpreted with care as a proxy for δ²H_SSW.</p></div>","PeriodicalId":400,"journal":{"name":"Organic Geochemistry","volume":"196 ","pages":"Article 104840"},"PeriodicalIF":2.6,"publicationDate":"2024-07-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0146638024001050/pdfft?md5=a69a426889b12c40d0c297c335a93ddd&pid=1-s2.0-S0146638024001050-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141781565","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Seasonality of amino acid enantiomers and microbial communities at MOLA time series in the NW Mediterranean Sea","authors":"Anabel von Jackowski ,&nbsp;Nawal Bouchachi ,&nbsp;Quentin-Boris Barral ,&nbsp;Paul Labatut ,&nbsp;Barbara Marie ,&nbsp;Olivier Crispi ,&nbsp;Karine Escoubeyrou ,&nbsp;Charles-Hubert Paulin ,&nbsp;Celine Dimier ,&nbsp;Josephine Ras ,&nbsp;Alexander Hayward ,&nbsp;Eva Ortega‐Retuerta","doi":"10.1016/j.orggeochem.2024.104839","DOIUrl":"10.1016/j.orggeochem.2024.104839","url":null,"abstract":"<div><p>Seasonality in light, temperature, and nutrient availability are well-known to regulate phytoplankton blooms and the bacterioplankton community. During the spring bloom, phytoplankton release biomolecules as part of the dissolved organic matter (DOM) pool exploited by the bacterioplankton. Here, we investigated the seasonal variability of phytoplankton biomass, enantiomers of dissolved hydrolyzable amino acids (DHAA), bacterioplankton abundances and community composition at the Microbial Observatory Laboratory Arago (MOLA) in the NW Mediterranean Sea from 2019 to 2021. Phytoplankton biomass estimated from pigment biomarkers suggests a spring bloom succession from cryptophytes, haptophytes, and prasinophytes in March to diatoms in April. The spring bloom coincided with a 50% increase in L-enantiomers of DHAA and an increase in bacterial abundance. After the spring bloom, elevated concentrations of D-enantiomers of DHAA and gamma-aminobutyric acid suggest bacterial processing of labile biomolecules contributed to the seasonal accumulation of dissolved organic carbon (DOC). Linking organic molecules with the free-living bacterioplankton community showed a seasonal succession of niches and substrate regimes. The parallel analysis of DOM and bacterioplankton community provides an important baseline for bacteria-substrate relationships over the seasonal cycle in the northwestern Mediterranean Sea.</p></div>","PeriodicalId":400,"journal":{"name":"Organic Geochemistry","volume":"196 ","pages":"Article 104839"},"PeriodicalIF":2.6,"publicationDate":"2024-07-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0146638024001049/pdfft?md5=2e86bb1bf2a4206301bbba0cda8f8bca&pid=1-s2.0-S0146638024001049-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141840020","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Geochemistry Articles – May 2024","authors":"","doi":"10.1016/j.orggeochem.2024.104814","DOIUrl":"10.1016/j.orggeochem.2024.104814","url":null,"abstract":"","PeriodicalId":400,"journal":{"name":"Organic Geochemistry","volume":"195 ","pages":"Article 104814"},"PeriodicalIF":2.6,"publicationDate":"2024-07-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141705023","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The preservation of photosynthetic and hydrological signals in the carbon and hydrogen isotope compositions of n-fatty acids in the seasonal wetland soils of the Okavango Delta (Botswana)","authors":"Julie Lattaud ,&nbsp;Mangaliso J. Gondwe ,&nbsp;Matthias Saurer ,&nbsp;Carole Helfter ,&nbsp;Cindy De Jonge","doi":"10.1016/j.orggeochem.2024.104832","DOIUrl":"https://doi.org/10.1016/j.orggeochem.2024.104832","url":null,"abstract":"<div><p>The Okavango wetland (Botswana) is the world’s largest inland delta. A strong seasonality in water input leads to the contraction and extension of wetlands in the floodplains. The extreme evapotranspiration and little precipitation lead to a difference in the hydrogen isotope signature of rain, soil and river water. Biomarkers, such as plant waxes, are stored in the soils and preserved on geological timescales. To understand which signal is preserved in the stable isotope signatures of plant waxes, soils along a 250 m-long transect spanning waterlogged to dry soils were collected over several seasons and three years. In addition, plants, and plant and soil water were collected along this transect. First, carbon isotope ratios (δ¹³C) of plant waxes (i.e, <em>n</em>-fatty acids) were used to classify their metabolism. δ¹³C of bulk organic matter and individual <em>n</em>-fatty acids analyzed in the soils show a strong dependance on the type of vegetation found along the transect (C₃ versus C₄ plants). Hydrogen isotope ratios (δ²H) of water present in soil showed that shallow-rooted C₄ grasses use superficial soil water, whereas the xylem water δ²H content in trees growing near the flooded channel indicated the use of river water. In addition, plant hydrogen fractionation between lipids and rain showed a strong influence of carbon metabolisms with larger fractionation for C₃ plants compared with C₄ grasses. <em>n</em>-fatty acid δ²H ratios in surface soils followed the hydrological variation in the Delta with its floods and dry periods. Hence δ²H of long-chain fatty acids seems to track the river-level variation rather than precipitation.</p></div>","PeriodicalId":400,"journal":{"name":"Organic Geochemistry","volume":"195 ","pages":"Article 104832"},"PeriodicalIF":2.6,"publicationDate":"2024-07-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0146638024000974/pdfft?md5=3e9087196b9fab43136f18bf44b2aabc&pid=1-s2.0-S0146638024000974-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141582347","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}