Organic Geochemistry最新文献

{"title":"On-line hydropyrolysis gas chromatography-mass spectrometry (HyPy-GC–MS) for kerogen-bound biomarkers","authors":"Fu Wang ,&nbsp;Yuhong Liao ,&nbsp;Chang Samuel Hsu","doi":"10.1016/j.orggeochem.2024.104927","DOIUrl":"10.1016/j.orggeochem.2024.104927","url":null,"abstract":"<div><div>Flash pyrolysis gas chromatography-mass spectrometry (Py-GC–MS) is seldom used to release bound biomarkers, because its hydrogen-poor pyrolysis conditions usually result in a low yield of bound biomarkers and high concentrations of olefins. In this study, by using a Py-GC–MS system and immature kerogen/coal samples, we investigated the effects of heating rate (flash versus 30 °C/min), carrier/reaction gas (He versus H₂), hydrogen pressure, and catalyst [(NH₄)₂MoO₂S₂] on the yields and distributions of bound biomarkers. Also, the bound biomarkers obtained by different pyrolysis conditions were compared with those from catalytic offline hydropyrolysis (HyPy) and free biomarkers from extracted organic matter (EOM). We propose a new technology of hydropyrolysis-gas chromatography-mass spectrometry (HyPy-GC–MS) to be used to release bound biomarkers. HyPy-GC–MS using low-pressure H₂ at slow heating rate can increase the yield of bound biomarkers by 3–9 times, minimize the cracking of the hopanes side chain, better preserve the original sterane and terpane distributions, and have characteristics<!--> <!-->of lower maturity, compared with conventional flash Py-GC–MS without H₂. Additionally, the steroidal and terpenoid yields by HyPy-GC–MS using low-pressure H₂ at slow heating rate from immature kerogens were 3–6 times that by HyPy. Compared with EOM, biomarker maturity parameter derived from HyPy-GC–MS may not fully represent the actual maturity of samples. Higher hydrogen pressure can significantly facilitate the hydrogenation of unsaturated hydrocarbons into saturated hydrocarbons, but it can also decrease the yields of pyrolysates with higher carbon numbers (i.e., &gt;C₂₅), leading to a change in the biomarker ratios related to carbon numbers (e.g., the proportion of C₂₇-C₂₈-C₂₉ ααα20R steranes and TT₂₃/H₃₀ ratio).</div></div>","PeriodicalId":400,"journal":{"name":"Organic Geochemistry","volume":"200 ","pages":"Article 104927"},"PeriodicalIF":2.6,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143176264","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":"Controlling factors and geological applications of the drimane-skeleton compound content and composition of crude oils in complex petroleum systems: New insights from the Western Pearl River Mouth Basin, South China Sea","authors":"Peng Cheng ,&nbsp;Yuhao Ren ,&nbsp;Haifeng Gai ,&nbsp;Shangli Liu ,&nbsp;Tao Cheng ,&nbsp;Hui Tian","doi":"10.1016/j.orggeochem.2024.104925","DOIUrl":"10.1016/j.orggeochem.2024.104925","url":null,"abstract":"<div><div>Crude oils generally contain drimane-skeleton compounds, but the uncertainty of the main factors controlling drimane distributions limits their effective geological applications, especially in complex petroleum systems. In this study, the drimane-skeleton compound composition and the relative content of each drimane-skeleton compound to C₃₀ hopane (C_DSC) were systematically studied for crude oils in different structural regions of the Western Pearl River Mouth (WPRM) Basin, South China Sea. The results show that the C_DSC of crude oil is mainly controlled by its organic sources. Higher C_DSC values in crude oil indicates a greater contribution from terrigenous organic matter to their source rocks. For crude oils from source rocks with similar biotic inputs, the C_DSC values are controlled mainly by the depositional environment. Higher C_DSC values in crude oil correspond to higher concentrations of clay minerals and lower salinities. In addition, the drimane-skeleton compound composition of crude oil is largely controlled by its maturity. The ratios of drimane to homodrimane (Dr/HDr), total rearranged drimane to total drimane and homodrimane (TRDr/TDr), and 8-rearranged drimane to 9-rearranged drimane (8RDr/9RDr) synchronously increase with increasing maturity. These ratios can effectively characterize the maturity of various types of crude oils. The maturity range characterized by the drimane maturity parameters is greater than that characterized by conventional maturity parameters. Correlation diagrams based on drimane parameters and other organic geochemical parameters can be used to classify crude oils and reveal their sources and origins, which has great application potential in complex petroliferous basins, especially in deep and ultra-deep petroleum systems with abundant light oil/condensate.</div></div>","PeriodicalId":400,"journal":{"name":"Organic Geochemistry","volume":"200 ","pages":"Article 104925"},"PeriodicalIF":2.6,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143175325","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":"Constraining the sources of archaeal tetraether lipids in multiple cold seep provinces of the Cascadia Margin","authors":"Katherine J. Keller ,&nbsp;Mark M. Baum ,&nbsp;Xiao-Lei Liu ,&nbsp;Kemi Ashing-Giwa ,&nbsp;Isabel R. Baker ,&nbsp;Jerome Blewett ,&nbsp;Ann Pearson","doi":"10.1016/j.orggeochem.2024.104882","DOIUrl":"10.1016/j.orggeochem.2024.104882","url":null,"abstract":"<div><div>Archaeal isoprenoid glycerol dialkyl glycerol tetraether lipid (iGDGT) abundance profiles and carbon isotopic compositions reflect the relative distributions of archaeal sources, including planktonic, benthic, and methane-cycling contributions. Here, we analyze the carbon isotope ratios of iGDGTs purified from sediments of three different cold seep sites in Cascadia Margin, off the coast of Washington, USA. Together with relative abundance and glycerol configurations, we use the carbon isotope ratios to estimate the contributions of multiple archaeal sources to the sedimentary iGDGT assemblages and their impact on values of the TEX₈₆ and methane indices. Using a Bayesian mixing model, we robustly characterize three potential endmembers by determining their characteristic lipid distributions, inferred contributions to the total sediment inventory, and carbon isotopic signatures. Despite the geographic proximity of the sample locations, we find site-specific heterogeneity in relative iGDGT abundances and δ¹³C values. Planktonic and benthic methane-cycling sources predominate in all cases (contributing &gt; 98% of iGDGTs), while benthic non-methane cycling archaea contribute minimally to the sedimentary lipid pool. Environments with higher methane influence show an increased presence of anti-parallel iGDGTs, indicating that methane-cycling archaea may dominantly or exclusively synthesize iGDGTs in this configuration. Our results quantify the relationship between the methane index (MI) and methane impact in systems dominated by planktonic and benthic methane-cycling archaea. Within the framework of the TEX₈₆ temperature proxy, this permits a quantitative demonstration that it is overly simplistic to apply a MI cutoff threshold as a binary indicator to determine methane influence, and caution is needed when taking this approach in paleoclimate reconstructions.</div></div>","PeriodicalId":400,"journal":{"name":"Organic Geochemistry","volume":"200 ","pages":"Article 104882"},"PeriodicalIF":2.6,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143176249","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":"Contrasting particulate organic carbon and sediment trophic status in two Antarctic fjords: Hope Bay and Collins Bay","authors":"Stefanie Martínez ,&nbsp;Luis Cerpa ,&nbsp;Pablo Muniz ,&nbsp;Natalia Venturini","doi":"10.1016/j.orggeochem.2024.104926","DOIUrl":"10.1016/j.orggeochem.2024.104926","url":null,"abstract":"<div><div>Fjords of the Antarctic Peninsula are sensitive to climate change and important carbon sinks, due to their high sedimentation rates. We used several biogeochemical markers to establish sediment trophic status, origin, and sources of suspended and sedimentary organic carbon (OC) in two fjords, Hope Bay (HB) and Collins Bay (CB). Water samples at different depths and bottom sediments were collected in 2019/20 on board the R/V BAP Carrasco. Distinct glacier runoff settings between the two studied fjords were reflected in different physico-chemical water column conditions. Based on its isotopic and biopolymeric composition suspended particulate organic carbon (POC) in both HB and CB, can be considered fresh with high nutritional and energetic quality. Also, POC is derived from recent phytoplankton production, subjected to little bacterial degradation and zooplankton grazing. The predominance of muddy sediments and high total proteins (PRT) concentrations (2.88–3.04 mg g⁻¹) in CB, contrasting with sandy sediments and low PRT concentrations (1.37–1.55 mg g⁻¹) in HB, were consistent with a higher sedimentation rate in CB than in HB. The predominance of PRT-rich and fresh marine sedimentary OC in bottom sediments of the two fjords denoted the occurrence of an important benthic-pelagic coupling. Sedimentary C/N and δ¹³C indicated a main autochthonous marine origin of OC in bottom sediments of the two fjords. Biopolymeric carbon (BPC) concentrations showed that HB sediments are mesotrophic, whereas CB sediments are eutrophic, with a high organic load. Our results show the relevance of getting an integrated vision of both the pelagic and the benthic systems, for a better understanding of OC pathways and fate in Antarctic fjords undergoing rapid environmental changes linked to climate change.</div></div>","PeriodicalId":400,"journal":{"name":"Organic Geochemistry","volume":"200 ","pages":"Article 104926"},"PeriodicalIF":2.6,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143175351","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":"Large-scale accumulation of abiotic gases associated with subduction and volcanic activities in rift basins in eastern China","authors":"Dongya Zhu ,&nbsp;Quanyou Liu ,&nbsp;Xiaowei Huang ,&nbsp;Qingqiang Meng ,&nbsp;Jingbin Wang ,&nbsp;Pengpeng Li ,&nbsp;Zhijun Jin","doi":"10.1016/j.orggeochem.2024.104900","DOIUrl":"10.1016/j.orggeochem.2024.104900","url":null,"abstract":"<div><div>A series of large-scale abiotic gas reservoirs have been discovered in a few rift basins in eastern China. However, the compositions of the abiotic gases in each gas reservoir differ significantly, dominated by CO₂ or CH₄. This study aims to explore the factors controlling the large-scale generation and accumulation of different types of abiotic gases in the reservoirs. CO₂ is the major component of the abiotic gases in the Huangqiao, Huagou, and Pingfangwang reservoirs, exceeding 60 % up to 95 % and the δ¹³C_CO2 values are generally greater than −8‰. CH₄ is the major component in the Qingshen and Songnan reservoirs with content up to 94.98 %. The δ¹³C_CH4 values are commonly greater than −30 ‰ (up to −16.8 ‰) and the alkanes exhibit a reverse sequence (δ¹³C_CH4 &gt; δ¹³C_C2H6 &gt; δ¹³C_C3H8 &gt; δ¹³C_C4H10). Most of the ³He/⁴He ratios of the reservoirs are commonly greater than 1 Ra. The carbon isotope values and ³He/⁴He ratios indicate that most of the gas components (CO₂ or CH₄) are abiotic. The abiotic CO₂ is associated with mantle-degassing, and abiotic CH₄ is mantle-derived and/or attributed to Fischer-Tropsch (FT) reactions. The ratios of Fe³⁺/∑Fe of the basalt near the Huangqiao reservoir are higher than those near the Qingshen and Songnan reservoirs, suggesting the relatively oxygen-fugacity controls the major component of the abiotic gases. The northwestward subduction of the western Pacific Plate, starting from the Japan Trench, triggered extensive magmatic and volcanic activities, resulting in the release and accumulation of abiotic gases in the rift basins. The variation in oxygen fugacity associated with oxidizing materials (e.g., iron and manganese oxides) and carbonate and sulfate sediments carried by the subducted plate determined the presence of abiotic CO₂ or CH₄. As the subduction slab continues moving forward beneath the continental plate, the influence of high-oxygen-fugacity materials gradually decreases, causing the abiotic gases to transition from CO₂ to CH₄. The Huangqiao, Huagou, Pingfangwang, Songnan, and Qingshen gas reservoirs are located farther away from the subducting slab, which explains the gradual shift in the abiotic component in these reservoirs. In general, the majority of the abiotic gases are released from deep faults and magmatic eruptions. Therefore, we conclude that the abiotic gas reservoirs are located near deep faults and igneous rocks.</div></div>","PeriodicalId":400,"journal":{"name":"Organic Geochemistry","volume":"200 ","pages":"Article 104900"},"PeriodicalIF":2.6,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143176285","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":"Dissolved organic matter molecular composition controls potential biodegradability","authors":"Meiling Man,&nbsp;Myrna J. Simpson","doi":"10.1016/j.orggeochem.2024.104924","DOIUrl":"10.1016/j.orggeochem.2024.104924","url":null,"abstract":"<div><div>Dissolved organic matter (DOM) is a heterogenous mixture of plant- and microbial-derived compounds at various stages of decomposition. However, there is a lack of detailed information about the biodegradability of DOM from different terrestrial sources that have varying molecular compositions. To circumvent this, incubation experiments were conducted for two months using DOM isolated from three different terrestrial sources: forest soil, peat and leonardite, all with distinct extents of diagenesis. The dissolved organic carbon (DOC), total dissolved nitrogen (TDN) contents, pH, and headspace CO₂ production were measured. DOM composition was monitored using solution-state ¹H nuclear magnetic resonance (NMR) and ultraviolet–visible (UV–VIS) analyses. To further understand microbial responses, microbial biomass and community composition was analyzed with phospholipid fatty acid (PLFA). DOM isolated from forest soil and peat demonstrated high biodegradability and decreased DOC concentrations, higher CO₂ production rates and higher microbial biomass over the course of incubation. Forest soil-derived DOM composition had decreased aliphatic, and carbohydrate and peptide components in the early and late stages, respectively. Peat-derived DOM exhibited lower carbohydrate and peptide concentrations and higher carboxyl-rich alicyclic molecules (CRAM). In contrast, CRAM and aromatic enriched leonardite-derived DOM had low CO₂ production and microbial biomass, and no major changes in DOM chemical composition, suggesting limited biodegradability. Further, CO₂ production, microbial biomass, and DOM molecular weight and degradation indices were positively correlated with carbohydrates and peptides, and inversely related to CRAM and aromatic components. Overall, these results corroborated distinct biogeochemical dynamics with varied DOM molecular composition, and highlight that DOM enriched in bio-recalcitrant components limited microbial processing, and exhibited high geochemical stability.</div></div>","PeriodicalId":400,"journal":{"name":"Organic Geochemistry","volume":"200 ","pages":"Article 104924"},"PeriodicalIF":2.6,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143175326","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":"The δ13C composition and genetic origin of a series straight long-chain alkyl naphthalene isomer pairs in the Upper Cretaceous lacustrine sediments of Songliao Basin, China","authors":"Xinxing Cao ,&nbsp;Yan Li ,&nbsp;Zhiguang Song","doi":"10.1016/j.orggeochem.2024.104898","DOIUrl":"10.1016/j.orggeochem.2024.104898","url":null,"abstract":"<div><div>A series of straight long-chain alkyl naphthalene isomer pairs (LANs) have been detected in the Upper Cretaceous lacustrine sediments of Nenjiang Formation (K₂n¹⁺²) in the Songliao Basin, and their distribution and carbon isotopic composition were investigated. The results indicate that the composition and distribution of LANs exhibit significant variations. The relative abundance of methyl- and dimethyl-naphthalenes shows a reciprocal correlation with that of LANs, increasing and declining in tandem. The δ¹³C composition of LANs varies from −24.6 ‰ to –32.6 ‰, with an average of −28.5 ‰, which is notably higher than that of <em>n</em>-alkanes, ranging from −31.9 ‰ to −34.5 ‰. The δ¹³C composition of methylnaphthalenes (MNs) ranges from −26.9 ‰ to −27.1 ‰, which is generally more positive than the average δ¹³C composition of LANs. Analysis of the carbon isotopic composition of <em>n</em>-alkanes, methylnaphthalenes, and the series of LANs, along with their distribution patterns, suggests the presence of multiple formation mechanisms. Specifically, the observed declining variation pattern of δ¹³C values for LANs along with the increasing carbon number of the alkyl chain may indicate a novel formation pathway. This pathway likely involves a direct reaction between ¹³C-enriched naphthalene and ¹³C-depleted straight long-alkyl chains during diagenesis. The relative abundance ratio of total methyl-substituted naphthalenes (ΣMNs) to the total LANs (ΣLANs), expressed as the ΣMNs/ΣLANs ratio, exhibits a profile variation that correlates with the profile changes of the Pr/Ph ratio, TOC content, and HI index. This correlation indicates that specific environmental conditions or source inputs, such as reduced sedimentary conditions or specific algal contributions, may be conducive to the formation of LANs.</div></div>","PeriodicalId":400,"journal":{"name":"Organic Geochemistry","volume":"200 ","pages":"Article 104898"},"PeriodicalIF":2.6,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143175350","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":"Solvent effect in Soxhlet extraction of source rocks","authors":"Jing Liao ,&nbsp;Juncang Wang ,&nbsp;Hong Lu ,&nbsp;Guoying Sheng ,&nbsp;Ping’an Peng ,&nbsp;Chang Samuel Hsu","doi":"10.1016/j.orggeochem.2024.104917","DOIUrl":"10.1016/j.orggeochem.2024.104917","url":null,"abstract":"<div><div>An abundant series of saturated <em>n</em>-C₁₂ to <em>n</em>-C₃₂ fatty acid methyl esters (FAMEs) was unexpectedly detected in the aromatic fraction of Maoming oil shale extracts. Since no pretreatments involving saponification, acidification and esterification were used, these saturated <em>n</em>-FAMEs were suspected either originally present in samples or formed by inadventent methylation of <em>n</em>-FAs during Soxhlet extraction. Several carefully designed Soxhlet extraction experiments using a mixture of <em>n</em>-fatty acid standards (MFASTDs) with different volume ratios of dichloromethane (DCM) and methanol (MeOH) as solvents were performed to investigate if the methyl esterification (methylation) could indeed occur in the traditional Soxhlet extraction.</div><div>The results revealed that when methanol alone was used as the extraction solvent, the esterification of fatty acids was very weak. However, with the addition of a proper amount of dichloromethane, for example, 3:2 or 4:1 vol ratio (<em>v/v</em>) of DCM:MeOH as extraction solvent, strong esterification reactions occurred and the esterification of MFASTDs reached almost 100 %. With 9:1 <em>v/v</em> of DCM:MeOH as used in conventional Soxhlet extraction, MFASTDs at lower loadings were nearly all esterified, while at higher loadings, the esterification of short-chain FAs could reach ∼ 80 % while long-chain <em>n</em>-FAs were completely esterified. Therefore, we conclude that <em>n</em>-FAs can be methylated by conventional Soxhlet extraction and DCM plays an important role in esterification.</div><div>The saturated <em>n</em>-C₁₂ to <em>n</em>-C₃₂ FAMEs in Maoming oil shales might be from free <em>n</em>-FAs derived from <em>Botryococcus braunii</em> (<em>B. braunii</em>) since they shared similar carbon number distributions as <em>n</em>-alkanes in the same samples, especially with a striking predominance of <em>n</em>-C₂₇. Abundant clay minerals existing in the Maoming oil shales are believed responsible for the formation of free <em>n</em>-FAs because they can provide Brønsted acidity to accelerate hydrolysis of ester linkage to release the bound fatty acids to free forms in specific environment having suitable low water content.</div></div>","PeriodicalId":400,"journal":{"name":"Organic Geochemistry","volume":"200 ","pages":"Article 104917"},"PeriodicalIF":2.6,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143176247","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":"Effects of digestate application, winter crop species and development on dissolved organic matter composition along the soil profile","authors":"Anne-Flore Didelot ,&nbsp;Anne Jaffrezic ,&nbsp;Thierry Morvan ,&nbsp;Marine Liotaud ,&nbsp;Florian Gaillard ,&nbsp;Emilie Jardé","doi":"10.1016/j.orggeochem.2024.104923","DOIUrl":"10.1016/j.orggeochem.2024.104923","url":null,"abstract":"<div><div>Applying organic waste products (OWPs) and sowing cover crops are agronomic practices to improve soil health. OWPs can be used in anaerobic digestion. Because microorganisms consume some of the labile molecules, persistent molecules accumulate in digestate. Few studies have investigated the transfer of dissolved organic matter (DOM) in soil that received digestate. Previously, effects of digestate application on dissolved organic carbon (DOC) were compared to those of the original pig slurry under wheat and a mustard catch crop for nine years at a lysimeter experimental site. DOC concentrations after digestate application were higher in the topsoil every year, due to crop development, but did not differ between treatments in the subsoil. The objectives of this study were to determine whether the observed differences in DOC concentrations caused DOM composition to differ, to identify sources (e.g., digestate, root exudation) that may have contributed to the DOM pool and to assess the DOM composition in the subsoil. The DOM composition of lysimeter samples and water extracts from the OWPs applied were analyzed by thermochemolysis coupled with gas chromatography and mass spectrometry, which identified plant- and microbial-derived biomarkers. Under mustard, the DOM pool seemed to contain mainly persistent molecules from digestate that were desorbed due to the increase in pH caused by nitrate uptake. Under wheat, the DOC pool seemed supplied by both digestate and root exudation. After applying digestate, plant-derived molecules decreased, while microbial-derived molecules increased, as depth increased, and molecules may have been sorbed from the topsoil to subsoil.</div></div>","PeriodicalId":400,"journal":{"name":"Organic Geochemistry","volume":"200 ","pages":"Article 104923"},"PeriodicalIF":2.6,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143176248","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":"Field and laboratory study on the distribution, fate and transport of polycyclic aromatic hydrocarbons in the loess porous medium at a refinery polluted site: Understanding the soil-groundwater interface","authors":"Minkai Du ,&nbsp;Miao Li ,&nbsp;Weijie Liu ,&nbsp;Mingming Shi ,&nbsp;Xiaoqian Li ,&nbsp;Xinli Xing ,&nbsp;Shihua Qi","doi":"10.1016/j.orggeochem.2024.104902","DOIUrl":"10.1016/j.orggeochem.2024.104902","url":null,"abstract":"<div><div>Soil and groundwater pollution from industrial and agricultural activities has become a global concern. This study therefore investigates the occurrence, sources, and transport mechanisms of polycyclic aromatic hydrocarbons (PAHs) in the soil-groundwater system of a closed refinery. Field investigations and laboratory column experiments revealed widespread PAH contamination in both groundwater and soil, with higher concentrations near the groundwater level (6.45–8.75 m). PAHs in soil and groundwater were predominantly low and medium molecular weight compounds (LMW and MMW), originated from petroleum leakage and coal combustion. The region’s soil, primarily composed of loess and gravel with low total organic carbon (TOC) content (mean 0.07%), showed a positive correlation between PAH concentration and TOC/clay content, while sand content had no significant impact. Groundwater fluctuations influence PAH accumulation at the soil-groundwater interface (SGI), which may suggest potential for increased migration under varying hydraulic conditions. This vertical migration offers new insights into contaminant transport models in groundwater systems, particularly for arid regions, and could inform future remediation strategies for similar contamination scenarios.</div></div>","PeriodicalId":400,"journal":{"name":"Organic Geochemistry","volume":"200 ","pages":"Article 104902"},"PeriodicalIF":2.6,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143176263","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}