Insoluble Organic Matter Research Articles

Compositional heterogeneity of insoluble organic matter extracted from asteroid Ryugu samples

AbstractWe report a Fourier transform infrared analysis of functional groups in insoluble organic matter (IOM) extracted from a series of 100–500 μm Ryugu grains collected during the two touchdowns of February 22 and July 11, 2019. IOM extracted from most of the samples is very similar to IOM in primitive CI, CM, and CR chondrites, and shows that the extent of thermal metamorphism in Ryugu regolith was, at best, very limited. One sample displays chemical signatures consistent with a very mild heating, likely due to asteroidal collision impacts. We also report a lower carbonyl abundance in Ryugu IOM samples compared to primitive chondrites, which could reflect the accretion of a less oxygenated precursor by Ryugu. The possible effects of hydrothermal alteration and terrestrial weathering are also discussed. Last, no firm conclusions could be drawn on the origin of the soluble outlier phases, observed along with IOM in this study and in the preliminary analysis of Ryugu samples. However, it is clear that the HF/HCl residues presented in this publication are a mix between IOM and the nitrogen‐rich outlier phase.

The dual role of potassium ferrate in promoting primary sludge hydrolysis and acidogenesis in anaerobic fermentation

Potassium ferrate (PF), a green disinfectant has been widely used in drinking water disinfection and has drawn immense attention for its application in sludge treatment. This research study has investigated the effects of PF on the hydrolysis and acidification of primary sludge (PS) to promote the short chain fatty acids (SCFAs) recovery, while achieving solid waste treatment and carbon emission reduction. The results showed that PF could effectively promote the accumulation of SCFAs, and maximum SCFAs yield of 4686.56 mg COD/L was achieved by PF assisted PS fermentation at a PF dosage of 0.4 g/g VSS, which was 2.05 times higher than the control. Substance transformation and enzyme activity analysis indicated that PF significantly promoted the release and hydrolysis of insoluble organic matters from PS through chemical oxidation and alkaline hydrolysis. Furthermore, high doses of PF could also inhibit the growth of methanogens and alter the dominant fermentation flora responsible for SCFAs production. Under the influence of high-dose PF, the foremost acidogenic bacteria were shifted into Trichococcus, Enterococcus, Streptococcus and Gallicola, which might be selectively enriched under the stress of residual Fe (Ⅲ) in the system. The PS fermentation liquid produced after PF pretreatment exhibited a higher C/N ratio and lower phosphorus concentration, which enhanced its suitability as carbon sources for denitrification in WWTPs. This study offered an environmentally friendly method for recovering SCFAs from PS and provided a viable approach to addressing the issue of carbon source shortage in wastewater treatment processes.

Abundant extraterrestrial purine nucleobases in the Murchison meteorite: Implications for a unified mechanism for purine synthesis in carbonaceous chondrite parent bodies

Extraterrestrial nucleobases are of key interest owing to their implications for the chemical evolution of primordial molecules in the solar system and their potential contributions to prebiotic chemistry on the early Earth. Recent advances in analytical techniques capable of detecting femto-mole-order nucleobases have allowed us to identify all five exogenous nucleobases—uracil, cytosine, thymine, adenine, and guanine—in carbonaceous chondrites and to quantify uracil obtained from the carbonaceous asteroid (162173) Ryugu. In this study, we optimized the analytical method using hot-water extraction followed by 6 M hydrochloric acid (HCl) extraction from a sample of the CM2 Murchison meteorite to reassess the abundances and distributions of extraterrestrial nucleobases. The target analyses performed using high-performance liquid chromatography paired with electrospray-ionization, high-resolution mass spectrometry revealed that purine nucleobases were substantially more enriched in the subsequent 6 M HCl extract (951 ± 104 parts per billion, ppb) than in the hot-water extract (199 ± 3 ppb). The most abundant nucleobase was guanine (649 ± 103 ppb in total). The 6 M HCl extract not only contained canonical nucleobases but also included rare nucleobase analogs from the purine family, such as 8-substituted purines. Unlike purines, we preferentially detected pyrimidine nucleobases in the hot-water extract and the acid hydrolysate (185 ± 17 ppb and 297 ± 5 ppb, respectively) rather than in the 6 M HCl extract (51 ± 4 ppb). The disparate distributions of purine and pyrimidine bases in the Murchison meteorite suggests that purines are more robustly incorporated than pyrimidines into meteoritic matrices and/or insoluble macromolecular organic matter. We propose a unified formation mechanism for purine nucleobases—which involves the synthesis of 5-aminoimidazole derivatives from hydrogen cyanide and its related molecules—that can account for the molecular distributions of the extraterrestrial purine nucleobases found in the Murchison meteorite.

The thermal history of Ryugu based on Raman characterization of Hayabusa2 samples

This paper is focused on the characterization of the thermal history of C-type asteroid Ryugu through the structure of the polyaromatic carbonaceous matter in the returned samples determined by Raman spectroscopy. Both intact particles and extracted Insoluble Organic Matter (IOM) from the two sampling sites on Ryugu have been characterized. The main conclusions are that (i) there is no structural difference of the polyaromatic component probed by Raman spectroscopy between the two sampling sites, (ii) in a manner similar to type 1 and 2 chondrites, the characterized Ryugu particles did not experience significant long-duration thermal metamorphism related to the radioactive decay of elements such as 26Al; (iii) some structural variability is nevertheless observed within our particle set. It can be interpreted as some particles having experienced some short-duration and weak heating (R3 in the scale defined by Quirico et al. 2018 and TII or lower according to the scale defined by Nakamura, 2005).

Low organic matter abundance and highly efficient hydrocarbon generation of saline source rock in the Qaidam Basin, NW China

The geochemical analysis and experimental simulation are comprehensively used to systematically study the hydrocarbon generation material, organic matter enrichment and hydrocarbon generation model of Paleogene source rock in the Western Qaidam Depression, Qaidam Basin, NW China. Three main factors result in low TOC values of saline lacustrine source rock of the Qaidam Basin: relatively poor nutrient supply inhibits the algal bloom, too fast deposition rate causes the dilution of organic matter, and high organic matter conversion efficiency causes the low residual organic carbon. For this type of hydrogen-rich organic matter, due to the reduction of organic carbon during hydrocarbon generation, TOC needs to be restored based on maturity before evaluating organic matter abundance. The hydrocarbon generation of saline lacustrine source rocks of the Qaidam Basin is from two parts: soluble organic matter and insoluble organic matter. The soluble organic matter is inherited from organisms and preserved in saline lacustrine basins. It generates hydrocarbons during low-maturity stage, and the formed hydrocarbons are rich in complex compounds such as NOS, and undergo secondary cracking to form light components in the later stage; the hydrocarbon generation model of insoluble organic matter conforms to the traditional “Tissot” model, with an oil generation peak corresponding to Ro of 1.0%.

Linear Polymer Comprising Dual Functionalities with Hierarchical Pores for Lithium Ion Batteries

AbstractOrganic materials with carbonyl, azo, nitrile and imine moieties are widely used in lithium batteries. The solubility of these materials in battery electrolytes is an issue. Aggregation of the organic molecules can suppress the solubility, but the accessibility of lithium‐ion is hindered. Therefore, insoluble porous organic materials are desired. Herein, we synthesized a linear polymer with carbonyl and azo functionalities. Due to the presence of easily isomerizable azo moiety, a porous polymer was obtained. The polymer showed nano and micropores. The battery with the porous polymer showed an impressive specific capacity of 400 mA h/g at 0.2 A/g. If the battery is pre‐conditioned, the specific capacity increased to 615 mA h/g at the same current density. The post‐mortem analysis of the battery confirmed that the polymer didn't dissolve in the battery electrolyte. The control material is a small molecule with carbonyl and azo moieties that showed a poor specific capacity of 40 mA h/g indicating the necessity to have a hierarchically porous dual‐functional polymer.

Ciprofloxacin sorption to purple soil: Potential mechanisms and factors influencing sorption

Understanding ciprofloxacin (CIP) sorption behavior onto purple soil is essential to minimize the associated environmental risks. However, CIP sorption onto the different components of purple soil and its underlying mechanisms are poorly understood. We performed a sorption experiment using original purple soils (Dayi soil (DORI) and Ya'an soil (YORI)), soils without dissolved organic matter (DOM) (DIOM and YIOM: insoluble organic matter remaining), and soils without organic matter (OM) (DM and YM: minerals remaining) to explore the CIP sorption behavior. Compared with DORI and YORI, the CIP sorption capacity of DM and YM decreased by 67.1% and 75.7%, indicating that the CIP sorption capacity was mainly contributed by OM. Compared with DORI and YORI, the CIP sorption capacity of DIOM and YIOM increased by 17.1% and 12.6%, suggesting that DOM in soil affected CIP sorption in purple soil. Redshifts and blueshifts confirmed that H-bonds and π-π interaction dominated the CIP sorption onto OM. CIP sorption was fitted by the Langmuir model, indicating monomolecular sorption. Compared with DORI and YORI, the KL of DM and YM was higher, implying that CIP sorption was faster and easier on minerals than on OM. Compared with K+, Ca2+ had a stronger hydration capacity but lower CIP sorption capacity in DM, suggesting that the stronger hydration capacity of cations was not conducive to CIP adsorption onto minerals and proving that the hydrophobic effect drove CIP adsorption. These mechanistic insights have important implications for understanding CIP sorption in purple soil.

Effect of forest soil viruses on bacterial community succession and the implication for soil carbon sequestration

Although the ecological importance of soil viruses is increasingly recognized, how soil viruses regulate the diversity, structure and succession of microbial communities has not been well understood. Here, we conducted an incubation experiment by mixing soil viruses and bacteria in different ratios, and tracked the changes in viral and bacterial cell abundances as well as bacterial community composition. Our results revealed that viral predation predominantly targeted host lineages that are r-strategists and was a key regulator of the succession of bacterial communities. Viral lysis markedly enhanced production of insoluble particulate organic matter, hence potentially contributing to carbon sequestration. In addition, treatment with mitomycin C led to significant shift in virus to bacteria ratio, and revealed bacterial lineages sensitive to lysogenic-lytic conversion, e.g., Burkholderiaceae in particular, indicating effect of prophage induction on bacterial community succession. Soil viruses also promoted homogeneous selection of the bacterial communities, suggesting the role of viruses in influencing bacterial community assembly mechanisms. Overall, this study provides empirical evidence of the top-down control exerted by viruses on soil bacterial communities and expanded knowledge about the associated regulatory mechanisms.

Development and evaluation of an improved offline aerosol mass spectrometry technique

Abstract. The offline aerosol mass spectrometry technique is a useful tool for the source apportionment of organic aerosol (OA) in areas and periods during which an aerosol mass spectrometer (AMS) is not available. However, the technique is based on the extraction of aerosol samples in water, while several atmospheric OA components are partially or fully insoluble in water. In this work an improved offline technique was developed and evaluated in an effort to capture most of the partially soluble and insoluble organic aerosol material, reducing significantly the uncertainty of the corresponding source apportionment. A major advantage of the proposed approach is that no corrections are needed for the offline analysis to account for the limited water solubility of some OA components. The improved offline AMS analysis was tested in three campaigns: two during winter and one during summer. Collocated online AMS measurements were performed for the evaluation of the offline method. Source apportionment analysis was performed separately for the online and the offline measurements using positive matrix factorization (PMF). The PMF results showed that the fractional contribution of each factor to the total OA differed between the online and the offline PMF results by less than 15 %. The differences in the AMS spectra of the factors of the two approaches could be significant, suggesting that the use of factor profiles from the literature in the offline analysis may lead to complications. Part of the good agreement between the online and the offline PMF results is due to the ability of the improved offline AMS technique to capture a bigger part of the OA, including insoluble organic material. This was evident by the significant fraction of submicrometer suspended insoluble particles present in the water extract and by the reduced insoluble material on the filters after the extraction process. More than half of the elemental carbon (EC) was on average missing from the filters after the water extraction. Significant EC concentrations were measured in the produced aerosol that was used as input to the AMS during the offline analysis.

Impact of Structural Flexibility of Amine Moieties as Bridges for Redox-Active Sites on Secondary Battery Performance.

Although environmentally benign organic cathode materials for secondary batteries are in demand, their high solubility in electrolyte solvents hinders broad applicability. In this study, a bridging fragment to link redox-active sites is incorporated into organic complexes with the aim of preventing dissolution in electrolyte systems with no significant performance loss. Evaluation of these complexes using an advanced computational approach reveals that the type of redox-active site (i. e., dicyanide, quinone, or dithione) is a key parameter for determining the intrinsic redox activity of the complexes, with the redox activity decreasing in the order of dithione>quinone>dicyanide. In contrast, the structural integrity is strongly reliant on the bridging style (i. e., amine-based single linkage or diamine-based double linkage). In particular, owing to their rigid anchoring effect, diamine-based double linkages incorporated at dithione sites allow structural integrity to be maintained with no significant decrease in the high thermodynamic performance of dithione sites. These findings provide insights into design directions for insoluble organic cathode materials that can sustain high performance and structural durability during repeated cycling.

Hydrogen isotopic evidence for nebular pre-hydration and the limited role of parent-body processes in CM chondrites

The conditions and environments in which hydrated phases in unequilibrated meteorites formed remain debated. Among carbonaceous chondrites, Mighei-type chondrites (CMs) display a large range in the degree of aqueous alteration, and thus record different stages of hydration and alteration. Here, we report the bulk H, C, and N contents, H and C isotopic compositions, and thermogravimetric signatures of the most- and least-altered CMs known so far, Kolang and Asuka 12236, respectively. We also report in-situ SIMS measurements of the hydrogen isotopic compositions of water in both chondrites. Compared to other CMs, Asuka 12236 has the lowest bulk water content (3.3 wt.% H2O) and the most D-rich water and bulk isotopic compositions (δD = 180‰ and 280‰, respectively). Combined with literature data, our results show that phyllosilicate-bearing CMs altered to varying degrees accreted water-ice grains with similar isotopic compositions. These results demonstrate that the hydrogen isotopic variations in CM chondrites (i) are not controlled by secondary alteration processes and (ii) were mostly shaped by interactions between the protoplanetary disk and the molecular cloud that episodically fed the disk over several million years. The minimally altered CM chondrites Paris and Asuka 12236 display peculiar, D-rich, hydrogen isotopic compositions that imply the presence of another H-bearing component in addition to insoluble organic matter and phyllosilicates. This component is most likely the hydrated amorphous silicates that are ubiquitous in these chondrites. CM bulk H and O isotopic compositions are linearly correlated, implying that (i) amorphous silicates in CM matrices were already hydrated by disk processes before the onset of CM parent-body alteration, and (ii) the quest for a hypothetically water-free CM3 is illusory.

Efficient carbon removal and excellent anti-clogging performance have been achieved in multilayer quartz sand horizontal subsurface flow constructed wetland for domestic sewage treatment

The present study aimed to investigate the application of a multilayer quartz sand substrate horizontal subsurface flow constructed wetland (HSFCW) for campus sewage treatment. It aimed to assess the pollutant removal efficiency and anti-clogging performance under the suggested maximum organic loading rate (250 g/m2/d). The results of the multilayer HSFCW (CW6) were compared to the mololayer HSFCW (CW1) for the removal of the chemical oxygen demand (COD), solid accumulation, and microbial communities. During operation, the combination conditions of high hydraulic loading rate (HLR) with low COD concentration were better for COD removal under a high organic loading rate (OLR) of 200–300 g/m2/d. The maximum removal rate reached 80.4% in CW6 under high HLR, which was 13.8% higher than that in CW1, showing better adsorption and biodegradation ability of organic matter. Impressive clogging resistance capacity was found in CW6 due to the lower contents of the insoluble organic matter (IOM) that are prone to clogging, indicating full degradation of organic matters, particularly IOM, in CW6 under high HLR. Less abundance of unclassified Chitinophagaceae (under low HLR), Pedobacter and Saccharibacteria_genera_incertae_sedis (under high HLR) in CW6, which contributed to aerobic membrane fouling, helped to prevent clogging. Moreover, Brevundimonas, Cloacibacterium, Citrobacter, Luteimonas contributed to IOM degradation, thus further enhancing the anti-clogging performance. In view of the better clogging resistance performance, the application of CW6 operated under high HLR and low COD concentrations was recommended to achieve economical, efficient, and steady COD removal for domestic sewage treatment in long-term operation.

The noble gas and nitrogen relationship between Ryugu and carbonaceous chondrites

Carbonaceous chondrites are considered to have originated from C-type asteroids and represent some of the most primitive material in our solar system. Furthermore, since carbonaceous chondrites can contain significant quantities of volatile elements, they may have played a crucial role in supplying volatiles and organic material to Earth and other inner solar system bodies. However, a major challenge of unravelling the volatile composition of chondritic meteorites is distinguishing between which features were inherited from the parent body, and what may be a secondary feature attributable to terrestrial weathering. In December 2020, the Hayabusa2 mission of the Japan Aerospace Exploration Agency (JAXA) successfully returned surface material from the C-type asteroid (162173) Ryugu to Earth. This material has now been classified as closely resembling CI-type chondrites, which are the most chemically pristine meteorites. The analysis of material from the surface of Ryugu therefore provides a unique opportunity to analyse the volatile composition of material that originated from a CI-type asteroid without the complications arising from terrestrial contamination. Given their highly volatile nature, the noble gas and nitrogen inventories of chondrites are highly sensitive to different alteration processes on the asteroid parent body, and to terrestrial contamination. Here, we investigate the nitrogen and noble gas signature of two pelletized grains collected from the first and second touchdown sites (Okazaki et al., 2022a), to provide an insight into the formation and alteration history of Ryugu. The concentration of trapped noble gas in the Ryugu samples is greater than the average composition of previously measured CI chondrites and are primarily derived from phase Q, although a significant contribution of presolar nanodiamond Xe-HL is noted. The large noble gas concentrations coupled with a significant contribution of presolar nanodiamonds suggests that the Ryugu samples may represent some of the most primitive unprocessed material from the early solar system. In contrast to the noble gases, the abundance of nitrogen and δ15N composition of the two Ryugu pellets are lower than the average CI chondrite value. We attribute the lower nitrogen abundances and δ15N measured in this study to the preferential loss of a 15N-rich phase from our samples during aqueous alteration on the parent planetesimal. The analyses of other grains returned from Ryugu have shown large variations in nitrogen concentrations and δ15N indicating that alteration fluids heterogeneously interacted with material now present on the surface of Ryugu. Finally, the ratio of trapped noble gases to nitrogen is higher than CI chondrites, and is closer to refractory phase Q and nanodiamonds. This indicates that Ryugu experienced aqueous alteration that led to the significant and variable loss of nitrogen, likely from soluble organic matter, without modification of the noble gas budget, which is primarily hosted in insoluble organic matter and presolar diamonds and is therefore more resistant to aqueous alteration.

Study on mutagenesis of high protease producing thermophilic bacteria by UV-DES and hydrolysis of excess sludge

Excess sludge a resource-rich organic waste, can be solubilized by thermophilic enzymes to extract proteins and anaerobic digestion of methane production to reduce sludge and use resources. At the same time, it can improve new ideas to relieve the pressure of the energy industry. To solve the problems of low enzyme-producing activity of wild strains and low hydrolysis rate of ES, this study utilized UV-DES compound mutagenesis to screen dominant mutant strains under optimized conditions, which were added to ES hydrolysis reaction system. The results showed that UV-DES mutagenesis could effectively improve the ability of S-TE and promote the hydrolysis of ES. The protease activity of the mutant strain KT16 obtained by screening was 46.7% higher than that of the original strain DC8. KT16 effectively degraded insoluble organic matter, reduced the average particle size of ES, and increased the concentrations of extracellular proteins, polypeptides, and amino acids to 1731.8, 521.3, and 510 mg·L-1, respectively. This study will provide a reference for the resource utilized.

Study on the pore structure and fractal characteristics on shale rock and isolated organic matter in lacustrine shales from the Changling fault depression in the Songliao Basin, China

The stock of shale gas in the Shahezi shale reservoir in the Changling fault depression, Songliao Basin, is believed to be worth exploring. In-depth study on the pore structure and fractal characterization of organic matter (OM) can help better understand the pore system of shale reservoir, which has implications for the exploration of lacustrine shale. To demonstrate the nanoscale pore structure and irregularity of the isolated OM, we collected a large number of samples and then conducted a series of laboratory experiments, such as X-ray diffraction, scanning electron microscopy, and [Formula: see text] and [Formula: see text] adsorption experiments to determine the pore structure parameters and reveal their heterogeneity according to Frenkel-Halsey-Hill theory. As suggested by the experimental results, the pore size distribution curve of the [Formula: see text] and [Formula: see text] exhibits similar pore peaks, whereas the trends of change in bulk shale and isolated OM samples are basically paralleled. The pore volume of the isolated OM ranges between 0.034 and [Formula: see text], which is approximately 0.90–3.06 times that of bulk shale samples. As for the fractal dimensions [Formula: see text] (2.594 on average) and [Formula: see text] (2.657 on average) of bulk shale, they are larger as compared with isolated OM, indicating that inorganic minerals can make a significant difference in the heterogeneity of shale pores. The fractal dimensions ([Formula: see text] and [Formula: see text]) of bulk shales indicate a close correlation with the parameters of pore structure, whereas there is no significant correlation observed between the dimensions of isolated OM and its parameters. In addition, thermal maturity and solid bitumen have only limited impact on the OM pore structure of isolated OM samples. Then, we conducted further research to reveal that the insoluble OM macerals derived from terrestrial higher plants can be used to explain the difference in pore structure and heterogeneity between isolated OM samples. Therefore, we arrived at the conclusion that the composition of macerals depends on the exact pore structure and fractal characteristics of isolated OM samples with similarity in thermal maturity.

The transition from soluble to insoluble organic matter in interstellar ice analogs and meteorites

Context. Carbonaceous chondrites are sources of information on the origin of the Solar System. Their organic content is conventionally classified as soluble (SOM) and insoluble organic matter (IOM), where the latter represents the majority. Aims. In this work, our objectives are to identify possible relations between soluble and insoluble organic matter generated in laboratory experiments and to extrapolate the laboratory analog findings to soluble and insoluble organic matter of meteorites to test their connection. Methods. Using laboratory experiments, processes possibly linking IOM analog (IOMA) to SOM analog (SOMA) precursors are investigated by assuming that dense molecular ices are one of the sources of organic matter in the Solar System. Each organic fraction is analyzed by laser desorption coupled to a Fourier transform ion cyclotron resonance mass spectrometer on a comprehensive basis. Results. SOMA and IOMA significantly differ in their chemical fingerprints, and particularly in their aromaticity, O/C, and N/C elemental ratios. Using an innovative molecular network, the SOMA–IOMA transition was tested, revealing connection between both classes. This new network suggests that IOMA is formed in two steps: a first generation IOMA based on precursors from SOMA, while a second IOMA generation is formed by altering the first IOMA generation. Finally, using the same analytical technique, the molecular content of IOMA and that of the Paris IOM are compared, showing their molecular similarities for the first time. The molecular network application to the Paris SOM and IOM demonstrates that a possible connection related to photochemical ice processing is present, but that the overall history of IOM formation in meteorites is much more complex and might have been affected by additional factors (e.g., aqueous alteration). Conclusions. Our approach provides a new way to analyze the organic fraction of extraterrestrial material, giving new insights into the evolution of organic matter in the Solar System.

Antarctic micrometeorite composed of CP and CS IDP‐like material: A micro‐breccia originated from a partially ice‐melted comet‐like small body

AbstractAsteroids and comets are thought to form in the inner and outer solar systems, respectively. Chondritic porous and smooth interplanetary dust particles (CP IDPs and CS IDPs, respectively) in the stratosphere are regarded as dust grains from comets and hydrated asteroids, respectively. Here, we describe an Antarctic micrometeorite (AMM) composed of lithologies of both CP and CS IDPs. In addition to the CS IDP‐like compact lithology that experienced severe aqueous alteration, the CP IDP‐like porous lithology shows evidence of very weak aqueous alteration. The structure of the organic matter in the porous lithology varies from that in the CP IDPs to aromatic‐rich organic matter. In contrast, the structure of the organic matter in the compact lithology is homogenous, which is consistent with higher degrees of aqueous alteration. Its structure is more similar to that of CP IDPs and Wild 2 samples than that of meteoritic insoluble organic matter, suggesting that the compact lithology formed from the porous lithology. Some CP IDPs are related to cometary dust streams, such as those originating from 26P/Grigg‐Skjellerup. In addition, the presence of this AMM indicates an additional origin of the CP IDPs and their equivalent AMMs. The mineralogy and organic chemistry of this AMM suggest that its parent body was composed of the same building blocks as those of the comets, and later experienced incomplete aqueous alteration. The AMM probably formed as microbreccia in the regolith layer composed of materials from a CP IDP‐like crust and a hydrated interior.

Bioturbation supplying young carbon into West Antarctic continental margin sediment

Accelerator Mass Spectrometry (AMS) 14C dating is a widely applied method for establishing high-precision chronologies used to underpin late Quaternary paleoclimatic studies. Feedbacks associated with Antarctic Ice Sheets (AIS) and Southern Ocean variance are thought to have played a critical role in regulating past global climate changes since the Last Glacial Maximum. However, determining the exact role of the AIS and Southern Ocean in these changes has proven difficult because of the sparse occurrence of biogenic carbonate suitable for AMS 14C dating in Antarctica. Consequently, AMS 14C dating is often measured on acid insoluble organic matter (AIOM) from bulk sediment samples, which are often biased towards ages that are older than the depositional age, due to pervasive reworking of old carbon. In this scenario, ages can still potentially provide maximum deposition ages, but such interpretations need to be assessed carefully. Here, we document AIOM and foraminifer AMS 14C dates at the same depth intervals from Antarctic continental margin cores, and we find AIOM AMS 14C dates can range between 2000 and 16,000 years younger than those of foraminifera samples. The younger AIOM 14C dates were found in bioturbated sedimentary facies, which often have extremely low sedimentation rates in Antarctica. In cores with low sedimentation rates, the down sediment contribution of organic carbon from macro-benthos can be quite significant in the sediment column with low organic carbon concentration. After considering possibilities of contamination, foraminifer reworking, and remineralization of secondary carbonate to explain this offset, we conclude that bioturbation plays an important role in the Antarctic carbon cycle as a young carbon supplier to depth into the sediment column. This has clear implications for using condensed sedimentary sections to date post-LGM records in Antarctica. These bioturbation processes also have implications for novel radiocarbon dating methods that have recently been developed to overcome sediment reworking processes and more accurately constrain timing of past AIS retreat, including ramped pyrolysis and compound specific isotopes methods.

Catalytic hydrogenation of insoluble organic matter of CS2/Acetone from coal over mesoporous HZSM-5 supported Ni and Ru

Catalytic hydrogenation of insoluble organic matter of CS2/Acetone from coal over mesoporous HZSM-5 supported Ni and Ru

Identification and characterization of a new ensemble of cometary organic molecules

In-situ study of comet 1P/Halley during its 1986 apparition revealed a surprising abundance of organic coma species. It remained unclear, whether or not these species originated from polymeric matter. Now, high-resolution mass-spectrometric data collected at comet 67P/Churyumov-Gerasimenko by ESA’s Rosetta mission unveil the chemical structure of complex cometary organics. Here, we identify an ensemble of individual molecules with masses up to 140 Da while demonstrating inconsistency of the data with relevant amounts of polymeric matter. The ensemble has an average composition of C1H1.56O0.134N0.046S0.017, identical to meteoritic soluble organic matter, and includes a plethora of chain-based, cyclic, and aromatic hydrocarbons at an approximate ratio of 6:3:1. Its compositional and structural properties, except for the H/C ratio, resemble those of other Solar System reservoirs of organics—from organic material in the Saturnian ring rain to meteoritic soluble and insoluble organic matter –, which is compatible with a shared prestellar history.