Organic Geochemistry最新文献

{"title":"Electrospray ionisation suppression in aquatic dissolved organic matter studies – Investigation via liquid chromatography–mass spectrometry","authors":"Jeffrey A. Hawkes","doi":"10.1016/j.orggeochem.2024.104852","DOIUrl":"10.1016/j.orggeochem.2024.104852","url":null,"abstract":"<div><p>Ionisation suppression is a persistent issue in electrospray ionisation mass spectrometry, which decreases the signal of co-eluting analytes. In non-targeted analysis, where analyte and organic matrix identity is unknown, this poses a very challenging analytical problem when it comes to quantitatively assessing differences between samples, including in a compositional sense. In this study, I demonstrate the problems that arise due to ionisation suppression using a very simple sample mixing scheme between a fresh, metabolite rich sample (a leaf leachate) and a forest pond water. Samples were analysed after solid phase extraction on Agilent PPL and using high performance liquid chromatography coupled to electrospray ionisation – Orbitrap mass spectrometry, charged aerosol detector and diode array detector, the latter two allowing quantification of eluting material. I found that more than half of the well-resolved analytes expected to be present (at equal concentration) were completely lost from detection after mixing with pond water DOM. The average recovery of analytical signal (i.e., the signal weighted average), was about 50%, and was highly variable between analytes. Ionisation suppression also affected the signal obtained from the geochemical background DOM, and material recovery decreased slightly when mixing samples and extracting at a higher volume on PPL. Overall, the results showed that ionisation suppression is an extremely important problem for comparison of biogeochemical samples, even when only considering presence and absence of detected features. A multi detector approach and liquid chromatographic separation adds great value in comparison to use of only high resolution mass spectrometry (in direct infusion mode).</p></div>","PeriodicalId":400,"journal":{"name":"Organic Geochemistry","volume":"196 ","pages":"Article 104852"},"PeriodicalIF":2.6,"publicationDate":"2024-08-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0146638024001177/pdfft?md5=ea44ab4b9d9bda29a26c158d352410bc&pid=1-s2.0-S0146638024001177-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142083610","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":"Compound-specific radiocarbon analysis of sedimentary fatty acids: Potential as a dating tool for lake sediments of Mt. Fuji volcanic region, Japan","authors":"Shinya Yamamoto ,&nbsp;Yosuke Miyairi ,&nbsp;Yusuke Yokoyama ,&nbsp;Yukihiko Serisawa ,&nbsp;Hisami Suga ,&nbsp;Nanako O. Ogawa ,&nbsp;Naohiko Ohkouchi","doi":"10.1016/j.orggeochem.2024.104860","DOIUrl":"10.1016/j.orggeochem.2024.104860","url":null,"abstract":"<div><p>Compound-specific radiocarbon analysis (CSRA) is a promising tool for dating sediment sequences where traditional dating methods are impractical. However, the applicability of CSRA of short-chain fatty acids as a dating tool remains poorly understood, especially in lacustrine settings. Accordingly, we determined the radiocarbon content (Δ¹⁴C) of individual fatty acids in sediments of Lake Yamanaka (central Japan), as well as their stable carbon and hydrogen isotope ratios, to evaluate the potential of CSRA as a dating tool in volcanic lake environments. We found that the Δ¹⁴C values of plant-derived (C₂₄, C₂₆, and C₂₈) <em>n</em>-fatty acids (–99‰ to –149‰) were considerably lower than the Δ¹⁴C of charred plants (139‰) within the sediments and those of living aquatic plants (–52‰ to –58‰) in Lake Yamanaka, suggesting that contributions from pre-aged terrestrial and aquatic plant materials likely affect these acids. Similarly, the Δ¹⁴C of C₁₆ <em>n</em>-fatty acid (–95‰) in surface sediments was much lower than the Δ¹⁴C of modern aquatic plants (–52‰ to –58‰), as well as the Δ¹⁴C of dissolved organic carbon (DIC) in surface water (–48‰). Together with the stable isotope results, we conclude that in addition to autochthonous aquatic sources, contributions from pre-aged terrestrial carbon sources significantly affect the Δ¹⁴C of C₁₆ <em>n</em>-fatty acids. Comparing fatty acid Δ¹⁴C and concentration data across lakes within the Mt. Fuji region suggests that CSRA of the C₁₆ acid provides valid chronological information only when the C₁₆ originates exclusively from autochthonous aquatic sources, with minor allochthonous terrestrial input.</p></div>","PeriodicalId":400,"journal":{"name":"Organic Geochemistry","volume":"196 ","pages":"Article 104860"},"PeriodicalIF":2.6,"publicationDate":"2024-08-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141998281","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 organic matter persistence in hyperhumic colluvial soils caused by palaeofires, root inputs and mineral binding","authors":"Joeri Kaal ,&nbsp;Antonio Martínez Cortizas ,&nbsp;Gerrit Angst ,&nbsp;Cynthia Kallenbach ,&nbsp;Cruz Ferro Vázquez ,&nbsp;Felipe Criado-Boado","doi":"10.1016/j.orggeochem.2024.104848","DOIUrl":"10.1016/j.orggeochem.2024.104848","url":null,"abstract":"<div><p>Understanding the formation of long-term persistent soil organic matter (SOM) is key to optimizing soil management and predicting the response of the terrestrial organic carbon (OC) pool to climate change, yet our knowledge of the soil-type dependent weight of different stabilization pathways (e.g., recalcitrance and mineral binding) is fragmentary. Owing to their stratigraphy, the exceptionally SOM-rich (up to 2 m of mineral soil with &gt;5% OC) colluvial slope deposits of Atlantic Europe (Haplic Umbrisol [colluvic/hyperhumic]) are archives of palaeo-environmental conditions including SOM formation pathways. The objective of this study was to determine how the different drivers of persistent SOM formation influenced the formation of these organic-rich soils. For this purpose, we use Holocene (∼9000 yrs) molecular composition records obtained from pyrolysis-GC–MS (Py-GC–MS) and thermally assisted hydrolysis and methylation (THM-GC–MS). The results emphasize three pathways to stability (i.e., persistence on millennial timescales): 1) palaeofires that generated recalcitrant pyrogenic SOM, 2) release of root-derived aliphatic macromolecules (suberin-like SOM), and 3) formation of microbial necromass. Pathways 1 and 2 are controlled by land use: Pathway 1 was relatively important under intense anthropogenic fire regimes and pyrophytic shrubland expansion; Pathway 2 was stimulated during early forest phases and under pasture conditions, when past societies focused vegetation management on grazing instead of fire; Pathway 3 was controlled by binding with aluminium-dominated mineral phases. However, we found indications that Pathway 2 (suberin input and preservation) relied partially on sorptive preservation as well. Aided by structured equation modeling (SEM), we show that the formation of persistent SOM pools was driven by balanced weights of i) microbial <em>vs.</em> plant-derived SOM and ii) intrinsic chemical properties of SOM (recalcitrance continuum) <em>vs.</em> mineral binding/occlusion, which varied in keeping with interactions between past land use, topography and vegetation. These findings are inconsistent with the prevalent paradigm of persistent SOM formation by sorptive/occlusive preservation of microbial necromass alone.</p></div>","PeriodicalId":400,"journal":{"name":"Organic Geochemistry","volume":"195 ","pages":"Article 104848"},"PeriodicalIF":2.6,"publicationDate":"2024-08-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S014663802400113X/pdfft?md5=38b28a7580aa3f892f9168d1f48580c9&pid=1-s2.0-S014663802400113X-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141935210","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":"Five series of benzohopanes in early Cretaceous sediments from the Chaoyang Basin, NE China","authors":"Lian Jiang ,&nbsp;Li Li ,&nbsp;Hans P. Nytoft ,&nbsp;Yunpeng Wang ,&nbsp;Simon C. George","doi":"10.1016/j.orggeochem.2024.104843","DOIUrl":"10.1016/j.orggeochem.2024.104843","url":null,"abstract":"<div><p>Five series of benzohopanes were identified in a set of immature to early-oil-window early Cretaceous sediments from the ZK1006 well, Chaoyang Basin, NE China. Series a (C₃₁-C₃₅), b (C₃₃-C₃₅), and c (C₃₁-C₃₅) benzohopanes form by different pathways, while the newly-found series d (C₃₁-C₃₄, maybe to C₃₅?) and e (C₃₁-C₃₂, maybe to C₃₅?) benzohopanes have similar formation mechanisms. Series a is usually the predominant benzohopane series, but occasionally samples are dominated by series c benzohopanes. Series b benzohopanes may be associated with terrigenous organic matter. Series a and b benzohopanes are possibly influenced by redox properties, while paleosalinity more likely controls the formation and enrichment of series c benzohopanes. Two novel parameters (a benzohopane index, and the C₃₅/C₃₄ benzohopane ratio) are proposed to be useful paleoenvironmental proxies in the study area. A high benzohopane index and C₃₅/C₃₄ benzohopane ratio may indicate an anoxic environment.</p></div>","PeriodicalId":400,"journal":{"name":"Organic Geochemistry","volume":"195 ","pages":"Article 104843"},"PeriodicalIF":2.6,"publicationDate":"2024-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0146638024001086/pdfft?md5=4f48228f7edbb96b94da6c27c1774a94&pid=1-s2.0-S0146638024001086-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141883037","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 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}