Isotopic Series Research Articles

Oxygen isotope dendrochronology allows dating of historical timbers across a wide geographical region.

We explore the applicability and geographic reach of two northwest European stable oxygen isotope (δ18O) chronologies for the precision dating of annually resolved δ18O series developed from late 15th-century oak (Quercus sp.) roof timbers from St. James’ Church in Bruges, Belgium. In doing so this study assesses ring-width dendrochronology and provenance analysis alongside oxygen isotope dendrochronology in Belgium and its surrounding regions.The δ18O-series of the historical timbers display a high internal coherence, allowing the construction of a mean isotope series (1325 to 1468 CE). Cross-dating against master chronologies for Central England, U.K. and Fontainebleau, France, provide reliable matches that surpass statistical thresholds and quality control measures, corroborating the dating results obtained from conventional ring-width dating.Oxygen stable isotope dendrochronology emerges as a valuable tool for precise dating of historical timber structures. This pilot study demonstrates the applicability of existing reference chronologies beyond their core regions and underscores its significance in cultural heritage studies. Despite the demanding nature of the technique in terms of time and expertise, the potential benefits warrant continued investment in expanding the temporal and geographic coverage of well-replicated oxygen isotope reference chronologies.

Baleen stable isotopes reveal climate-driven behavioural shifts in North Atlantic fin whales

Climate variability impacts the structure and functioning of marine ecosystems and can trigger behavioural responses in organisms. We investigated whether such variability modulates diet and migration in the North Atlantic fin whale (Balaenoptera physalus). To reconstruct the dietary and migratory behaviours over time, we conducted stable isotope analysis of nitrogen (δ15N) and carbon (δ13C) along baleen plates from 29 fin whales sampled off southwestern (SW) Iceland in summer. We estimated a baleen growth rate of 16.1 ± 2.5 cm per year from the stable isotope oscillations observed along the baleens. We also assigned a deposition date for each baleen segment, thus obtaining isotopic sequential time series. We then assessed the potential association of these time series with the main climate patterns of the North Atlantic basin. Baleen δ15N and δ13C values are associated with the North Atlantic Oscillation (NAO) and the Atlantic Multidecadal Oscillation (AMO). During high AMO and low NAO periods, which tend to decrease krill abundance, there is an increase in both the mean and standard deviation of baleen δ15N values, suggesting that fin whales shift to higher trophic resources and expand their dietary niche. Additionally, high AMO periods, which relate to positive temperature anomalies, lead to a decrease in baleen δ13C values, suggesting that fin whales adjust their migratory routes and destinations towards higher latitudes. Significant variation in isotopic niche width between years also reflected these dietary and migratory behavioural shifts. This highlights the plasticity of the North Atlantic fin whale behaviour, a trait likely to strengthen the resilience of the species within the current context of rapid and intense climate variability.

Ground state properties and bubble structure of the isotopic chains of Z = 125 and 126 using the relativistic mean-field formalism

The ground state properties of Z = 125 and 126 nuclei are investigated, taking the isotopic series from the proton to neutron drip-lines. This analysis uses the relativistic mean-field approach with NL3 and the Relativistic-Hartree–Bogoliubov model with DD-ME2 parameterization. The bulk properties under examination include the binding energy per nucleon, the neutron separation energies, the differential variation of the separation energy, the quadrupole deformation parameter β 2, and the single-particle energy. We observed the stability at N = 172 and 184 over the isotopic chain for both parameter sets. The quadrupole deformation parameter reveals a shape transition from prolate to spherical and back to prolate with mass number. No signature of a super- and/or hyper-deformed structure is found over the isotopic chain. Furthermore, the analysis is extended to examine the bubble structure, revealing a bubble/semi-bubble structure for a few neutron-rich isotopes.

Unveiling the origins and transport processes of radioactive pollutants downstream from a former U-mine site using isotopic tracers and U-238 series disequilibrium

High U concentrations (reaching up to 14,850 mg ⋅ kg−1), were determined in soils and sediments of a wetland downstream of a former U mine in France. This study aims to identify the origin of radioactive contaminants in the wetland by employing Pb isotope fingerprinting, (234U/238U) disequilibrium, SEM, and SIMS observations. Additionally, information about U and 226Ra transport processes was studied using U-238 series disequilibrium. The results of Pb fingerprinting highlighted inherited material inputs of different U-mines with mainly two types of U-ores: i) pitchblende (UO2), and ii) parsonsite (Pb2(UO2)(PO4)2). Moreover, significant disequilibrium of (230Th/238U) and (226Ra/230Th) activity ratios highlighted the mobility of 238U and 226Ra in the wetland, primarily driven by the water table fluctuations. Finally, this work uncovered a limitation of Pb isotope fingerprinting in the case of parsonsite materials, as the high natural Pb content of this mineral may hide the uranogenic Pb signature in the samples.

The Dynamic Evolution Model of the Chemical and Carbon Isotopic Composition of C1-3 during the Hydrocarbon Generation Process.

A new approach is presented in this paper for the dynamic modeling of the chemical and isotopic evolution of C1-3 during the hydrocarbon generation process. Based on systematic data obtained from published papers for the pyrolysis of various hydrocarbon sources (type I kerogen/source rock, type II kerogen/source rock, type III kerogen/source rock, crude oil, and asphalt, etc.), the empirical evolution framework of the chemical and isotopic composition of C1-3 during the hydrocarbon generation process was built. Although the empirical framework was built only by fitting a large amount of pyrolysis data, the chemical and isotopic composition of C1-3 derived from the pyrolysis experiments all follow evolution laws, convincing us that it is applicable to the thermal evolution process of various hydrocarbon sources. Based on the simplified formula of the isotopic composition of mixed natural gas at different maturities (δ13Cmixed), δ13Cmixed = X×niA×δ13CiA+Y×niB×δ13CiBX×niA+Y×niB, it can be derived that the cumulative isotopic composition of alkane generated in a certain maturity interval can be expressed by the integral of the product of the instantaneous isotopic composition and instantaneous yield at a certain maturity point, and then divided by the cumulative yield of alkane generated in the corresponding maturity interval. Thus, the cumulative isotopic composition (A(X)), cumulative yield (B(X)), instantaneous isotope (C(X)), and instantaneous yield (D(x)) in the dynamic model, comply with the following formula during the maturity interval of (X0~X). A(X) = ∫X0XCX×DXdxB(X), where A(X) and B(X) can be obtained by the fitting of pyrolysis data, and D(x) can also be obtained from the derivation of B(X). The dynamic model was applied on the pyrolysis data of Pingliang Shale to illustrate the quantitative evolution of the cumulative yield, instantaneous yield, cumulative isotope, and instantaneous isotope of C1-3 with increasing maturity. The dynamic model can quantify the yield of methane, ethane, and propane, as well as δ13C1, δ13C2, and δ13C3, respectively, during the hydrocarbon generation process. This model is of great significance for evaluating the natural gas resources of hydrocarbon source rock of different maturities and for identifying the origin and evolutionary process of hydrocarbons by chemical and isotopic data. Moreover, this model provides an approach to study the dynamic evolution of the isotope series of C1-3 (including reversed isotopic series), which is promising for revealing the mechanism responsible for isotopic reversal when combined with post-generation studies.

Intra-annual stable isotopes in the tree rings of Hymenaea courbaril as a proxy for hydroclimate variations in southern Amazonia

The hydrology of Amazonia is changing due to climate and land-use changes, especially in the southern region, which has warmed and dried faster than other tropical regions. Yet there are no long-term hydrological records to put these changes in a historical perspective. Here we investigate the use of tree-ring carbon (δ13C) and oxygen isotopes (δ18O) to assess the seasonal variation in climate for the southern Amazonia basin. We analysed the intra-annual variation of δ13C and δ18O in 10 segments of each tree ring from 2013 to 2017 from individuals of Hymenaea courbaril, a long-lived and widespread neotropical tree species. We find strong seasonal patterns of tree-ring δ13C supporting previous observations of annual growth rhythms for this species. The intra-annual variation in δ18O shows that the lowest values generally occur just after the middle point of ring formation, corresponding to the peak rainy season. We find strong correlations between the δ18O in the middle of the growth ring and vapour pressure deficit (r = 0.92, P = 0.02) and precipitation (r = −0.93, P = 0.02). We further find associations between the oxygen isotopic series and the discharge of the Araguaia basin’s main rivers during the rainy period. Our results show that these δ18O records are sensitive to fluctuations in rainfall and humidity, and thus to river discharge in the region. Longer reconstructions of based on tree-ring δ18O of Hymenaea courbaril could provide a novel proxy to assess past hydrological changes.

Experimental validation of energy dependences of YALO3:Mn TL detectors: irradiation to ISO radiation qualities.

The effect of application of filters, made of different materials and various thickness, is studied by Monte Carlo calculations using MCNP6.2 code. The calculated data were validated by experimental studies (benchmark tests). Experimental results obtained for YAlO3:Mn high-Z TL detectors irradiated to different standard ISO radiation qualities (X-ray series N-40, N-60, N-80, N-100, N-120, N-150 and N-200 as well as isotopic series S-Cs) modified by various metal (copper and aluminum) filters of thickness of 0.5, 0.8 and 1mm. The experimental results are compared with results of Monte Carlo simulations done for the same 'radiation-attenuator-detector' combinations and geometry. Obtained results show good consistence between the experimental and calculated data that testifies adequacy of the used calculations and their applicability to modeling of modification of an output from the high-Z detectors exposed to photons of various energies.

Responses of Tree Growth and Intrinsic Water Use Efficiency to Climate Factors and Human Activities in Upper Reaches of Tarim River in Alaer, Xinjiang, China

With global warming and increasing human activities, exploring the impact of the rising atmospheric carbon dioxide concentration and climate change on forest ecosystems is crucial. In this study, we focus on Euphrates poplar (Populus euphratica Oliv.) in the upper reaches of the Tarim River in the Alaer region of Xinjiang. We use dendrochronological methods, tree-ring width, and stable carbon isotope series to explain basal area increment (BAI) and intrinsic water use efficiency (iWUE) changes. We further explore the influence of past climate change and human activities on the radial growth and iWUE of P. euphratica through stable oxygen isotope analysis combined with historical literature records. The results showed that relative humidity had an essential effect on Δ13C and δ18O fractionation in P. euphratica tree rings, whereas the vapor pressure deficit (VPD) was considered the main factor influencing the inter-annual variability of the iWUE and BAI. Since 1850, long-term variations in iWUE have exhibited an upward trajectory correlated with rising atmospheric CO2 levels. Approximately 13% of this iWUE increase can be attributed to changes in carbon-concentration-induced water use efficiency (cciWUE). Although Δ13C and δ18O were generally uncorrelated between 1850 and 2018, around 1918, their relationship changed from being weakly correlated to being significantly negatively correlated, which may record changes related to the upstream Tarim River diversion. During the period from 1850 to 2018, both the BAI and iWUE showed an increasing trend for P. euphratica growth; however, the relationship between them was not stable: during 1850–1958, both variables were mainly influenced by climatic factors, while during 1959–2018, the most important influence was due to human activities, specifically agricultural development and irrigation diversions. An abrupt surge in the BAI was observed from 1959 to 1982, reaching its peak around 1982. Surprisingly, post-1983, the escalating iWUE did not correspond with a continuation of this upward trajectory in the BAI, highlighting a divergence from the previous trend where the enhanced iWUE no longer facilitated the growth of P. euphratica. Despite P. euphratica having adapted to the continuously rising Ca, improving its iWUE and growth capacity, this adaptive ability is unstable and may easily be affected by human activities. Overall, the increase in Ca has increased the iWUE of P. euphratica and promoted its growth at a low frequency, while human activities have promoted its development at a high frequency.

Inference and visualization of nuclear magnetic moment studies with neuro-fuzzy systems

This study aims to predict the magnetic moments of nuclei with odd-A numbers in a certain region of which the magnetic moment has not yet been calculated, using the Adaptive Neuro-Fuzzy Inference System (Anfis) method. In our Anfis model the proton number (Z), neutron number (N), and spin value (I) are used as inputs for nuclei with 1 ≤ Z ≤ 88. With 652 nuclei in the dataset, consisting of the provided input data, 528 odd-A nuclei were used for training, and 124 odd-A nuclei were used for testing. The fact that the Anfis model was closer to the experimental data in the training and testing processes than the theoretical methods encouraged us to make inferences about the nuclei of which experimental nuclear magnetic moment is unknown. Motivated by the presence of odd-A nuclei exhibiting I π = 1/2±, 3/2±, and 5/2± ground-state configurations near the doubly closed-shell, within the 1 ≤ Z ≤ 28 regions, along with the limited knowledge of nuclear properties in this range. This study has conducted magnetic moment inferences for 165 nuclei lacking experimental data. Specifically, Na, F, and P isotopes have been chosen as Magnetic moment value inferences made for these isotopes using Anfis have also been compared with the theoretical results of the Quasiparticle-Phonon Nuclear Method (QPNM) and with the Shell Model calculations. There is a satisfactory agreement between our predictions and the results of these two theories. Furthermore, it is noteworthy that within the same isotope series, nuclei with identical ground-state configurations consistently yield compatible results, irrespective of the availability of experimental magnetic moments. In addition, the fact that the values obtained from test and train operations remain within acceptable error limits, with a range of approximately 0.03%–0.04%, reveals the reliability of our system. Since the Neuro-Fuzzy system will be a first in the field of nuclear technologies, we believe that the outputs of our study will be a good reference for future studies.

Organic matter enrichment in Asia's palaeolake controlled by the early and middle Eocene global warming and astronomically driven precessional climate

The sediments deposited in continental lake systems record sensitive palaeoclimate signals and provide better perspectives for understanding rapid palaeoclimate changes and their implications. To better understand the terrestrial record and climate-driven organic matter enrichment mechanism in a low-latitude region, which have rarely been investigated, we studied the Eocene terrestrial records from the Beibuwan Basin, South China Sea (SCS). Cyclostratigraphic analysis was conducted to assess the orbital forcing. Milankovitch-scale astronomical signals were determined by spectral analyses, evolutionary Fast Fourier transform, and sedimentation rates estimation of the natural gamma ray logging data in the depth domain. A floating astronomical time scale (ATS) was constructed based on astronomical tuning that converts the depth domain to the time domain by sedimentation rates. The ATS was calibrated using published dating result of 35.2 Ma from the Eocene to the Oligocene. This ATS constrains the ages of two organic-rich lacustrine petroleum source intervals of the Eocene Liushagang Formation in the Beibuwan Basin at ∼49-47 Ma and ∼40.9–40.2 Ma, respectively. A comparison of the timing of these two source rocks with a published global benthic carbon and oxygen isotope series shows that they correspond to Eocene positive carbon isotope excursions. This finding suggests that organic carbon burial in Eocene lacustrine basins responded to early and middle Eocene Climatic Optimum (i.e., EECO and MECO). We used geochemical data based on X-ray fluorescence core scans for further investigation of the effect of orbital forcing on organic matter enrichment. The high Rb/Sr, K + Ti + Rb and Sr/Ca geochemical ratios and stable Mo and U/Th values all correspond to the precessional minimum, suggesting that the orbital precessional minimum is responsible for a warm and humid climate, and brackish and hypoxic water conditions. Thus, four schematic hypotheses were proposed to explain the effect of the precessional monsoonal climate on organic matter enrichment. This study provides a terrestrial record that documents the mid-Eocene global warming event well and provides evidence that the orbital precessional climate controlled organic matter enrichment in Asia's palaeolake.

A 195-Year Growing Season Relative Humidity Reconstruction Using Tree-Ring Cellulose δ13C in the Upper Tarim River Basin, NW China

Reconstruction of relative humidity changes in the upper Tarim River using carbon isotopic tree-ring chronology bridges the gap in historical observations on the Tarim River Basin in Arid Central Asia. Populus euphratica Olivier (P. euphratica), growing in the Tarim River Basin of Xinjiang, is an excellent record of past climate change. Based on precise dating, we analysed alpha-cellulose stable carbon isotopes in four cores of P. euphratica taken from the Alaer region of the upper Tarim River Basin. The four stable carbon isotope series records were corrected by the “pin method” and then combined into a carbon isotopic discrimination (Δ13C) series by the “numerical mix method”. The discrimination (Δ13C) series were clearly correlated with the mean relative humidity (RHAS) in April–September of the growing season (n = 60, r = −0.78, p < 0.001), and according to the climate response analysis, we designed a simple regression equation to reconstruct the mean relative humidity (RHAS) in April–September from 1824 to 2018 on the Alaer region. The reconstructed sequence showed mainly dry periods in the last 195 years, 1857–1866 and 1899–1907, while primarily wet periods from 1985 to 2016. Due to increased global warming and human activities, the climate shifted from “warm–dry” to “warm–wet” in the mid-to-late 1980s, when there were signs of a shift from “warm–wet” to “warm–dry” in the 2010s, with an increasing trend towards aridity. The RHAS series of Alaer compares well to other hydroclimate series’ surrounding the research area, and the spatial correlation analysis indicates that the reconstructed series has good regional representativeness. On an interdecadal scale, the revamped RHAS series is positively correlated with the Atlantic Multidecadal Oscillation (AMO) and negatively correlated with the North Atlantic Oscillation (NAO), reflecting the influence of westerly circulation on regional wet and dry variability. At the same time, the RHAS may also be influenced by The Pacific Decadal Oscillation (PDO).

Developing tree ring chronologies from New Zealand matai (Prumnopitys taxifolia (D.Don) Laub.) for archaeological dating: Stable isotope dendrochronology

Aotearoa New Zealand has a rich cultural heritage but dating wooden objects using classic dendrochronology is challenging due to a paucity of master tree-ring width chronologies for species commonly identified in the archaeological record. This paper explores the potential for using a stable isotopic approach to dendrochronology for matai (Prumnopitys taxifolia (D.Don) Laub.). A total of six annual stable oxygen isotope (δ18O) series for matai growing in the Pureora Forest Reserve, were analysed and their oxygen isotopes found to exhibit a level of coherence that enabled cross-dating. A provisional chronology covering the period 1930–2018 CE was developed and tested against a sample of matai from the Kauaeranga Valley (200 km to the north of Pureora) and a sample of miro (Prumnopitys ferruginea (D.Don) Laub.). Miro is another species common in the cultural archive, but also difficult to date using ring-width dendrochronology. Both the Kaueranga matai and Pureora miro samples cross matched against the site chronology at the correct position, but with weaker dating statistics (Student’s t: 4.26 and 4.11 respectively) compared to the results obtained for two (non-2019) sampled Pureora matai analysed in this study (Student's t: 6.80 and 5.66). These results nevertheless demonstrate the presence of a regional-scale dating signal which may be developed for future use as a precision dating tool.

Environmental reconstructions based on aquatic and terrestrial snails originating from the Early Bronze Age and the Late Islamic Period– A stable isotope case study from the Al-Khashbah archaeological Site, Sultanate of Oman

Fossil shells of terrestrial and aquatic snails provide important information for the reconstruction of the Early Bronze Age environmental conditions in the Sultanate of Oman. Terrestrial species can be used to reconstruct available and thus consumed vegetation and the origin of precipitation, while aquatic species are useful for temperature estimates. The aim of this study is to identify past environmental conditions by generating high-resolution stable isotope series from well-preserved aragonitic shells of gastropods. A total of seven shells of the terrestrial species Zootecus insularis and five aquatic snails, Melanoides tuberculata, from Al-Khashbah were sampled. Eight of them were dated to the Early Bronze Age and four belong to the Late Islamic period that can be used as a reference. Stable isotope data of carbon (δ13Cshell) of the terrestrial snails indicate a change in digested vegetation from C3 plants in the Early Bronze Age to C4 plants in the Late Islamic period. δ18Oshell data obtained by the fully aquatic snails (range of max. 1 ‰) suggests a habitat, e.g., groundwater, with a strong environmental buffering effect. Though sudden rainfall events followed by subsequent evaporation are not recorded in the isotope record, data suggest highly variable palaeoprecipitation regimes with different origins (Indian Ocean and Mediterranean).

A Comparison of the Geochemical Characteristics of Ultra-Deep Natural Gas in the Kuqa Foreland and Marine Craton Areas in the Tarim Basin, China

This research analyzed the composition and hydrocarbon isotope geochemical characteristics of ultra-deep natural gas (buried deeper than 6000 m) in more than 130 wells in the Tarim Basin. Characteristics of the ultra-deep natural gas components in the Tarim Basin are as follows: natural gas in the Kuqa sandstone reservoir is developed as dry gas, with a high methane content (an average of 95.53%) and a low ethane content (an average of only 1.39%). The ultra-deep gas of the marine craton carbonate reservoirs in the North Tarim-Central Tarim-East Tarim area is developed as wet gas. It is mainly composed of methane ranging from 56.1% to 98.8%, with an average content of 76.36% and also contains a small amount of ethane amounting to 6.74%. CO2 and H2S contents of ultra-deep condensate gas in the Central Tarim area are high, with maximum values of 24.2% and 23.1%, respectively. Isotopic characteristics are as follows: δ13C1 values of Kuqa natural gas are distributed between −36‰ and −25.3‰, with an average of −28.2‰, δ13C2 values are distributed between −26.2‰ and −13.8‰, with an average of −18.3‰. Most gas samples in Kuqa area are developed with the reversal of carbon isotopic series as δ13C2 > δ13C3, and the δ13CCO2 values are distributed between −19.5‰ and −10.3‰. The δ13C1 values of ultra-deep gas in marine craton carbonate rocks are distributed between −54.4‰ and −33.3‰, with an average of −42.6‰. δ13C2 values are distributed between −41.1‰ and −29.4‰, with an average of −33.8‰, and δ13CCO2 values are distributed between −28.2‰–0.6‰. According to the identification chart, it can be seen that the ultra-deep gas in the sandstone reservoir of the Kuqa foreland is mainly coal-derived gas in the high over-mature stage, and the reversal of carbon isotopic series may be caused by the mixing of natural gas of the same type and different sources. The natural gas in carbonate reservoirs of marine craton is mainly oil-type gas with complex sources, including both kerogen cracking gas and oil cracking gas. CO2 can be formed by organic and inorganic genesis. Inorganic CO2 is most likely to be generated by the dissolution of carbonate rocks under acid formation water.

World Atlas of late Quaternary Foraminiferal Oxygen and Carbon Isotope Ratios

Abstract. We present a global atlas of downcore foraminiferal oxygen and carbon isotope ratios available at https://doi.org/10.1594/PANGAEA.936747 (Mulitza et al., 2021a). The database contains 2106 published and previously unpublished stable isotope downcore records with 361 949 stable isotope values of various planktic and benthic species of Foraminifera from 1265 sediment cores. Age constraints are provided by 6153 uncalibrated radiocarbon ages from 598 (47 %) of the cores. Each stable isotope and radiocarbon series is provided in a separate netCDF file containing fundamental metadata as attributes. The data set can be managed and explored with the free software tool PaleoDataView. The atlas will provide important data for paleoceanographic analyses and compilations, site surveys, or for teaching marine stratigraphy. The database can be updated with new records as they are generated, providing a live ongoing resource into the future.

Geochemical Characteristics and Origin of Tight Gas in Member Two of the Upper Triassic Xujiahe Formation in Western Sichuan Depression, Sichuan Basin, SW China

Natural gas in the tight sandstone reservoirs in Member two of the Upper Triassic Xujiahe Formation in the Western Sichuan Depression of the Sichuan Basin has complex geochemical characteristics, and the origin and source of the tight gas are revealed based on the geochemical analysis and comparison in this study. The tight gas has the dryness coefficient of 0.950–0.994, which is positively correlated with the CH4 content. The gaseous alkanes display positive carbon isotopic series, with the δ13C1 and δ13C2 values ranging from −35.6‰ to −30.3‰ and from −29.1‰ to −21.0‰, respectively, and the δD1 values range from −176‰ to −155‰. Genetic identification based on the carbon and hydrogen isotopic compositions indicates that a small amount of tight gas is typically coal-derived gas, whereas most of the tight-gas samples have experienced mixing by oil-associated gas. Geochemical comparisons suggest that the tight gas displays distinct differences with the typical oil-associated gas in Member four of the Middle Triassic Leikoupo Formation in the Chuanxi gas field and the typical coal-derived gas in Member five of Xujiahe Formation in the Xinchang gas field. It is also apparently different from the typical coal-derived gas in Member two of Xujiahe Formation in both Zhongba and Qiongxi gas fields. Among the tight gas in Member two of the Xujiahe Formation from the Western Sichuan Depression, the coal-derived gas is generated mainly by the humic mudstone in the Upper Triassic Ma’antang and Xiaotangzi formations, with assistance of the humic mudstone in Member two of the Xujiahe Formation, whereas the oil-associated gas is derived from the sapropelic limestone in the Ma’antang Formation.

The geochemical characteristics and origin of Ordovician ultra-deep natural gas in the North Shuntuoguole area, Tarim Basin, NW China

Ultra-deep Ordovician in Shuntuoguole area, Tarim Basin, NW China, has complex oil & gas phases, in which light oil, volatile oil, condensate and dry gas phases coexisting. The study compares the geochemical characteristics and origin of Ordovician ultra-deep natural gas in the North Shuntuoguole (SB) area to that of gas in the Shuntuo (ST), South Shuntuoguole (SN), Gulong (GL), and Gucheng (GC) areas using natural gas composition, carbon isotope and hydrogen isotope data and light hydrocarbon data. The Ordovician ultra-deep natural gas in the SB area is wet gas, with dryness indexes ranging from 0.52 to 0.88 and minimal H2S content. The carbon isotopes of natural gas are relatively low, with δ13C1 and δ13C2 values ranging from −49.6‰ to −44.7‰ and −39.3‰ to −32.7‰, respectively. All the natural gas shows positive carbon and hydrogen isotope series. The n-alkane and iso-alkane dominate the C5–C7 light hydrocarbon, with the methylcyclohexane index of light hydrocarbon lower than 35%. All of the Ordovician natural gas in the Shuntuogule area is oil-type gas. The Ordovician natural gas in the SB area is dominated by kerogen cracking gas, with a small fraction of wet gas from the early stages of oil cracking, whereas, all of the gas in the ST, SN, GL and GC areas comes from oil cracking. The Cambrian source rocks led directly to both types of cracking gases. The distribution of two types of cracking gas in the Shuntuogule area is correlated with the maximum paleogeothermal temperature and (or) present temperature of the Ordovician. The maximum paleogeothermal temperature and present Ordovician temperature in the SB area are 170–180 °C and 150–160 °C, respectively, which are lower than those in ST and SN areas, and have not yet achieved the temperature of large amount oil cracking. As a result, light oil and volatile oil phases were preserved in the SB area, which was dominated by kerogen cracking gas, whereas reservoir phases varied from condensate to dry gas phases, and natural gas is oil-cracking gas, from ST to SN to GL to GC areas, due to large scale oil cracking caused by high present temperature and (or) paleo-geothermal temperature of the Ordovician.

Geochemical characteristics of natural gas in tight sandstone of the Chengdu large gas field, Western Sichuan Depression, Sichuan Basin, China

SINOPEC has made significant progress in natural gas exploration in terrigenous tight sandstone in the Western Sichuan Depression, making it one of the predominant exploration areas in the Sichuan Basin. Although the Chengdu large gas field was located in the main reservoirs of Upper Jurassic tight sandstone, few geochemical proofs were presented to support the explanation of the gas source, and regional differences in natural gas have been poorly investigated. The Jurassic tight gas in the Chengdu large gas field has a dryness coefficient (C1/C1-5) of 0.939–0.982, and the δ13C1, δ13C2, and δD1 values range from −33.7‰ to −30.7‰, −25.4‰ to −22.3‰, and −162‰ to −153‰, respectively, with positive carbon and hydrogen isotopic series of gaseous alkanes. The carbon and hydrogen isotopic compositions of the Jurassic tight gas indicate that it is typically coal-derived gas. The measured vitrinite reflectance (RO) values of source rocks of Member 5 of the Xujiahe Formation, which are demonstrated as the main source of Jurassic tight gas, are consistent with the calculated RO values according to the two-stage fractionation model of coal-derived gas. Effective source rocks are rare in the Lower Jurassic Baitianba Formation of the study area, which is considered to have only a minor contribution to the Jurassic gas reservoirs. The geochemical characteristics of Jurassic natural gas from various gas fields in the Western Sichuan Depression vary depending on the effect of different gas sources and accumulation processes.

Methane (CH<sub>4</sub>) sources in Krakow, Poland: insights from isotope analysis

Abstract. Methane (CH4) emissions from human activities are a threat to the resilience of our current climate system. The stable isotopic composition of methane (δ13C and δ2H) allows us to distinguish between the different CH4 origins. A significant part of the European CH4 emissions, 3.6 % in 2018, comes from coal extraction in Poland, the Upper Silesian Coal Basin (USCB) being the main hotspot. Measurements of CH4 mole fraction (χ(CH4)), δ13C, and δ2H in CH4 in ambient air were performed continuously during 6 months in 2018 and 2019 at Krakow, Poland, in the east of the USCB. In addition, air samples were collected during parallel mobile campaigns, from multiple CH4 sources in the footprint area of the continuous measurements. The resulting isotopic signatures from sampled plumes allowed us to distinguish between natural gas leaks, coal mine fugitive emissions, landfill and sewage, and ruminants. The use of δ2H in CH4 is crucial to distinguish the fossil fuel emissions in the case of Krakow because their relatively depleted δ13C values overlap with the ones of microbial sources. The observed χ(CH4) time series showed regular daily night-time accumulations, sometimes combined with irregular pollution events during the day. The isotopic signatures of each peak were obtained using the Keeling plot method and generally fall in the range of thermogenic CH4 formation – with δ13C between −59.3 ‰ and −37.4 ‰ Vienna Pee Dee Belemnite (V-PDB) and δ2H between −291 ‰ and −137 ‰ Vienna Standard Mean Ocean Water (V-SMOW). They compare well with the signatures measured for gas leaks in Krakow and USCB mines. The CHIMERE transport model was used to compute the CH4 and isotopic composition time series in Krakow, based on two emission inventories. The magnitude of the pollution events is generally underestimated in the model, which suggests that emission rates in the inventories are too low. The simulated isotopic source signatures, obtained with Keeling plots on each simulated peak, indicate that a higher contribution from fuel combustion sources in the EDGAR v5.0 inventory would lead to a better agreement than when using CAMS-REG-GHG v4.2 (Copernicus Atmosphere Monitoring Service REGional inventory for Air Pollutants and GreenHouse Gases). The isotopic mismatches between model and observations are mainly caused by uncertainties in the assigned isotopic signatures for each source category and the way they are classified in the inventory. These uncertainties are larger for emissions close to the study site, which are more heterogenous than the ones advected from the USCB coal mines. Our isotope approach proves to be very sensitive in this region, thus helping to evaluate emission estimates.

O21 - Topic: AS02-Epidemiology: CONDITIONAL RELATIVE SURVIVAL IN MYELODYSPLASTIC SYNDROMES REVEALS A PERMANENT EXCESS MORTALITY RISK FOR LONG-TERM SURVIVORS: A POPULATION-BASED STUDY IN THE NETHERLANDS

SINOPEC has made significant progress in natural gas exploration in terrigenous tight sandstone in the Western Sichuan Depression, making it one of the predominant exploration areas in the Sichuan Basin. Although the Chengdu large gas field was located in the main reservoirs of Upper Jurassic tight sandstone, few geochemical proofs were presented to support the explanation of the gas source, and regional differences in natural gas have been poorly investigated. The Jurassic tight gas in the Chengdu large gas field has a dryness coefficient (C1/C1-5) of 0.939–0.982, and the δ13C1, δ13C2, and δD1 values range from −33.7‰ to −30.7‰, −25.4‰ to −22.3‰, and −162‰ to −153‰, respectively, with positive carbon and hydrogen isotopic series of gaseous alkanes. The carbon and hydrogen isotopic compositions of the Jurassic tight gas indicate that it is typically coal-derived gas. The measured vitrinite reflectance (RO) values of source rocks of Member 5 of the Xujiahe Formation, which are demonstrated as the main source of Jurassic tight gas, are consistent with the calculated RO values according to the two-stage fractionation model of coal-derived gas. Effective source rocks are rare in the Lower Jurassic Baitianba Formation of the study area, which is considered to have only a minor contribution to the Jurassic gas reservoirs. The geochemical characteristics of Jurassic natural gas from various gas fields in the Western Sichuan Depression vary depending on the effect of different gas sources and accumulation processes.