Organic-rich Samples Research Articles

Insights on Using Solid Bitumen Reflectance as a Thermal Maturity Proxy in the Bakken Formation, Williston Basin, USA.

To further refine the use of solid bitumen reflectance (BRo in %) as a measurement of thermal maturity in source-rock reservoirs, we examined its relationship to other thermal proxies in the Bakken Formation. Comparisons included criteria from programmed temperature pyrolysis, gas chromatography (GC), and Fourier transform infrared (FTIR) spectroscopy. Thirty-two organic-rich samples from the lower and upper shale members of the Devonian-Lower Carboniferous Bakken Formation were collected from eight cores across the Williston Basin, USA, at depths (∼7575-11,330 ft) representing immature through post peak oil/early condensate thermal maturity conditions based on proximity to current hydrocarbon production. Unmodified BRo values were correlated to programmed temperature pyrolysis parameters (hydrogen index, production index, and T max), normal hydrocarbon and isoprenoid analysis of extractable organic matter (pristane/n-C17 and phytane/n-C18) from GC analysis, and peak ratios from FTIR spectroscopy (branching ratio and A-factor). Strong correlations between unmodified BRo values (not corrected to a vitrinite reflectance equivalent, VRe) and other thermal proxies suggest that BRo can be used as a direct thermal proxy in marine Paleozoic source-rock reservoirs where vitrinite is rare or absent. Moreover, an apparent overestimation of VRe at the lowest thermal maturity investigated herein may argue against the application of BRo conversion to VRe in the Bakken Formation. Solvent extraction caused a consistent decrease in BRo when average post-extraction values from a given well were compared to BRo prior to extraction, although the decrease in mean value was not statistically significant. These results are discussed in the context of advocating for the use of unmodified BRo values as a best practice for thermal maturity determination in Paleozoic marine source-rock reservoirs.

Nitrogen isotopic compositions of organic-rich shales (∼560 Ma) in the Chengkou region, South China: Implications for a stable and relatively large nitrate reservoir of the late Ediacaran ocean

The late Ediacaran period is a critical transitional period in Earth's history, marked by the evolution of the Ediacara biota (∼574 to 538.8 Ma). The marine redox state and nutrient level, having a close relationship with bioevolution, can be reflected by sedimentary nitrogen isotopes (δ15N). Doushantuo Formation Member IV, a widespread organic-rich interval during this critical period of South China, may provide important clues for nitrogen (N) cycling. However, high-resolution δ15N research on Member IV is still lacking. In this study, a drill core from the Chengkou sub-basin, with the well-developed Doushantuo Member IV, was carefully studied base on its N isotopic composition. The implications for the N cycling characteristics are discussed using a combination of proxies for bottom water redox conditions and basin openness. The total nitrogen (TN) concentrations (up to 0.79 wt%) of these organic-rich samples are substantially higher than those of other counterpart profiles. The TOC content shows a positive linear relationship with TN concentration, and a significant positive TN-intercept (∼0.21 wt%) represents the addition of inorganic N produced by the remineralization of sinking organic N. The high TN concentrations may also be due to the flourishing and enhanced burial of primary producers. The δ15N value in the Doushantuo Member IV progressively decreases from ∼8.2‰ to ∼3.2‰ (from bottom to top), a result of the changes in basin openness and the enhancement of N2-fixation. Compilation shows the δ15N and δ13Corg values are approximately covariant, and both have significant temporal and spatial variations at this member of South China, indicating a strong heterogeneity in the water column redox environments and changes in the type of primary producers. A mode δ15N value of 4‰ indicates a stable and relatively large nitrate reservoir in the late Ediacaran ocean.

Determination of atmospherically deposited microplastics in moss: Method development and performance evaluation

The investigation of atmospheric microplastic pollution is a rising topic within microplastic research. However, sampling strategies concerning atmospheric microplastics are not standardized yet and strongly depend on the scientific objectives investigated. A few research groups are currently focused on determining atmospherically deposited microplastics in moss, as it can be a biomonitoring system for other atmospheric pollutants such as heavy metals, nitrogen, and persistent organic components. In this context, and for atmospheric microplastics in general, almost all examinations focus on determining microplastic numbers and shapes, while polymer masses are barely investigated. However, particle- and mass-based information are needed to assess the fate of atmospherically transported microplastics in the environment. For this purpose, this study shows the development and evaluation of a new sample preparation method for determining microplastics in moss for both analytical approaches using thermal extraction desorption-gas chromatography-mass spectrometry (TED-GC-MS) and Raman microspectroscopy (µRaman). Further, this newly developed microplastics/moss separation method (µPEEL) was compared to oxidative digestion using Fenton's reagent, usually used as a sample preparation method for organic-rich samples and moss. The method comparison was performed concerning green analytical chemistry (GAC) and its respective method functionality. The greenness was assessed using the software tool AGREEprep, which covers ten comprehensive aspects of GAC. Both methods’ functionality was assessed regarding observable matrix interferences and the data quality achieved. It is demonstrated that µPEEL benefits GAC and method functionality since harmful chemicals can be avoided, matrix interferences can be minimized, and the separation quality is increased.

Simultaneous molecular fingerprinting of natural organic matter and synthetic polymers (PE, PET, PP, PS and PVC) using analytical pyrolysis

The rapid accumulation of plastics in the environment has created the need for methods that allow to identify synthetic organic matter (SyOM) in sample matrices dominated by natural organic matter (NOM). We investigated the molecular composition of mixtures of peat with several key synthetic polymers –polyethylene (PE), polypropylene (PP), polyethylene terephthalate (PET), polystyrene (PS) and polyvinyl chloride (PVC)– using pyrolysis-GC-MS (Py-GC-MS) and thermally assisted hydrolysis and methylation (THM-GC-MS), to determine the capacities of these analytical tools to identify and quantify SyOM accumulation in organic-rich sample matrix without prior elimination of the NOM. The detection limit of Py-GC-MS depends mainly on the pyrolysis yield (signal intensity per unit of mass; PS > PE > PP > PET > PVC) and the specificity of the markers in the NOM matrix (PS > PET > PP > PVC > PE). Py-GC-MS allowed the identification of PET at a concentration of 0.002%, PS at 0.01%, PP at 0.1%, PE at 0.2% and PVC at 2%. Quantification was more problematic, as most markers showed inconsistent trends with SyOM concentration. THM-GC-MS yielded similar results, albeit the products of PP and PE could be more easily distinguished from NOM products because of the protection of the NOM’s fatty acids from decarboxylation, and because THM-GC-MS minimizes PET decarboxylation, enabling the use of the dimethyl terephthalate marker (detection limits: 0.02% for PE, PP and PET, 0.1% for PS and 0.2% for PVC). High-throughput analytical pyrolysis approaches have a clear potential to identify SyOM, but quantification requires NOM removal. In addition, we raise awareness of co-pyrolysis effects in simultaneous NOM-SyOM analysis, such as the influence of HCl formed during pyrolysis of PVC, which inhibits the intramolecular reorganization during cellulose pyrolysis and thus mitigates formation of the key product levoglucosan, and the effect of NOM on the balance between monomer, dimer and trimer products of PS. This study significantly advances on the analysis of widespread plastics polymers in NOM-rich environmental samples by pyrolysis and identify pitfalls in data interpretation.

Improving of an easy, effective and low-cost method for isolation of microplastic fibers collected in drying machines filters

Microplastic fibers have been found to be a dominant form of microplastics in water matrixes, and textile industry and domestic washing of synthetic textiles as one of its main sources. Additionally, there is a lack of knowlidge about microplastic fiber release during mechanically drying clothes and textiles due to differences in the isolation of microplastic fiber methods. Limited information available in the literature in terms of the isolation of microplastic fibers from organic-rich samples after using different household equipment represents one of the main challenges leading us to our main goal, to optimise an effective, simple, and low-cost method for the isolation of microplastic fibers from textile fibers of different origins without damaging their structure. This is achieved by primarily removing mineral matter by using density separation with a saturated solution of ZnCl2 followed by removal of organic matter by using hydrogen peroxide (H2O2) and FeCl3 as a catalyst. Identification of microplastic fibers was obtained by optical microscope, Fourier-transform infrared spectroscopy and Thermogravimetric analysis. Clear microscope (both optical and SEM) images, high percentage of obtained FTIR spectra overlap with Polymer Sample laboratory, clear TGA of isolated samples confirmed that this method can be used as a simple and effective method for isolation of microplastic fibers from organic components rich samples of different origin.

Automatic organofacies identification by means of Machine Learning on Raman spectra

In this study we compare and evaluate different unsupervised clustering algorithms for organofacies discrimination in low maturity dispersed organic matter based on Raman spectroscopic analyses. A total of 1363 Raman spectra were collected from a set of 27 organic-rich samples from the Lower Toarcian shale interval of the Paris Basin sub-surface. Rock-Eval pyrolysis data indicate a type II to type III kerogen with a vitrinite reflectance (Ro%) between 0.45% and 0.65%, and Tmax between 415 °C and 438 °C. Organic petrographic observations under transmitted light reveal the presence of organofacies composed by amorphous organic matter, opaque, and translucent phytoclasts. An optical classification of organic particles was performed on about 40–60 fragments per sample and used as the ground truth. Raman spectra were obtained for all the classified fragments and principal component analysis was performed to underline the variability among spectra. Unsupervised clustering was then applied on Raman spectra principal components. Three clustering methods were applied to evaluate their effectiveness in predicting number, shape and density of clusters and a contingency matrix was used to quantify their ability to predict different organofacies. Gaussian Mixture Model (GMM) was found to be the best algorithm for organofacies identification showing an accuracy mostly between 80% and 90%. This work outlines how unsupervised clustering of Raman spectra of dispersed organic matter can reduce the uncertainty in thermal maturity assessment and help the classification of highly heterogeneous organofacies when using large datasets for Earth and planetary sciences studies.

Hydrocarbon generation and retention potential of Chang 7 organic-rich shale in the Ordos Basin, China

This study investigates the hydrocarbon generation and retention potential of Chang 7 organic-rich shale, with an emphasis on the producibility of retained hydrocarbons, using a sample set chosen to represent a maturity spectrum of 0.54–0.9% R o and organic matter of type II and mixed type II–III. Based on the present-day hydrogen index (HI pd ), the sample sets were divided into three sections: Upper, Middle and Lower. The three sections have a high hydrocarbon generation potential, with an average original total organic carbon (TOC o ) content of 12.27, 3.10 and 5.13 wt%, of which 49.39, 23.62 and 49.86 wt% represents generative organic carbon (GOC), and an original hydrogen index (HI o ) of 581.27, 278.05 and 586.82 HC g −1 rock in the Upper, Middle, and Lower sections, respectively. The bulk of the analysed samples exhibited moderate–high oil saturation, yet the oil crossover effect was only observed in two organic-rich samples, indicating organic-rich shale-oil resource systems. The sorption capacity of organic matter controls oil retention in the Chang 7 shale system, where the oil saturation index increases with increasing maturity in the oil window until a maximum retention capacity of about 82–83 mgHC g −1 TOC is reached at a vitrinite reflectance of 0.8% and thereafter decreases with further maturity. Supplementary material: A detailed spreadsheet of the back-calculated original geochemical parameters using the mass-balance method of Jarvie (2012 a ) is available at https://doi.org/10.6084/m9.figshare.c.6387577

Pyrite Dissolution in the Cretaceous Yogou Formation of the Niger (Chad) Basin: Implications for Basin Evolution under a Rift Tectonic Setting.

This is the first study of pyrite minerals in the entire West and Central African Rift System (WCARS). Several polished organic-rich core samples from the Cretaceous Yogou Formation of the Niger (Chad) Basin located in the WCARS were investigated for their pyrite content using FE-SEM and SEM-EDS imaging techniques. An attempt was made to classify the types and provenance of the pyrites and to highlight the control of rift fractures on the oxidation and dissolution of pyrites in the region. Three major types of pyrites are present in the studied formation, including euhedral pyrite (EPy) crystals, pyrite framboids (FPy), and sunflower pyrites (SPy). A statistical analysis of 307 FPy shows that the framboids are diagenetically formed with an average diameter of 6.61 μm. SPy is present in a relatively low amount compared to framboids. The pyrites underwent a variety of diagenetic modifications, from mechanical compaction to oxidation, dissolution, and recrystallization. Unoxidized pyrites primarily contain Fe, S, and C, but oxidized pyrites also contain O, Al, and Si. There is a strong correlation between the fractures and the spatial distribution of the physicochemical alteration of the pyrite in the study. Dissolution in relatively deep-buried samples occurs mainly along fracture planes. The fractures provide a pathway for oxidants and other metal elements to reach the pyrites. The pattern of pyrite dissolution reflects the timing of fracture formation and fracture activities as a purveyor or drainage for fluids in the organic-rich samples investigated. The pyrites are associated intimately with organic matter (OM); thus, the relationship between the fracture and the pyrites' transformation is significant in the assessment of organic matter preservation at deep-burial depth.

The Control of Shale Composition on the Pore Structure Characteristics of Lacustrine Shales: A Case Study of the Chang 7 Member of the Triassic Yanchang Formation, Ordos Basin, North China

The pore structure characteristics of shales are controlled by their mineral and organic matter compositions. However, the contributions of different components to the pore structure characteristics of lacustrine shales remain poorly understood. In this study, fifteen Chang 7 Member shales of the Yanchang Formation, Ordos Basin, were investigated through total organic carbon (TOC), X-ray diffraction (XRD), scanning electron microscopy (SEM), and low-pressure N2 and CO2 adsorption analyses to study the control of shale composition on the pore structure characteristics of lacustrine shales. The results show that the average TOC content of the Chang 7 Member shales is 9.63 wt.%. XRD analysis shows that minerals in the Chang 7 Member shales consist of quartz, feldspars, clay minerals, and pyrite. The clay minerals were dominated by illite, chlorite, and interstratified illite/smectite. The mesopore characteristics of the Chang 7 Member shales and micropore characteristics of organic-lean shales are mainly controlled by clay minerals, whereas the micropore characteristics of organic-rich samples are controlled by both clay minerals and organic matter. SEM observations show that the phyllosilicate framework pores are the main pore type in the Chang 7 Member shales. The results of this study provide important insights into compositional control on the pore structure characteristics of lacustrine shales.

Application of heart-cutting two-dimensional liquid chromatography-mass spectrometry to the characterization of highly polar impurities in calcium gluconate injection

The separation and characterization of small polar impurities in polar drugs such as calcium gluconate products are always challenging, due to their poor retention on traditional reversed phase (RP) columns. Although ion-pair reversed-phase liquid chromatography (IPRP-LC) and hydrophilic interaction liquid chromatography (HILIC) are commonly used methods for polar compound analysis, both methods have some drawbacks. For example, IPRP-LC is incompatible with mass spectrometry (MS) due to the presence of non-volatile salts in its mobile phase and HILIC has limited sensitivity due to the poor solubility of polar drugs in the organic-rich sample diluents used in HILIC separations. In order to characterize the highly polar impurities in calcium gluconate injections, a heart-cutting two-dimensional liquid chromatography (2D-LC) method coupled with quadrupole time-of-flight mass spectrometry (Q-TOF/MS) was developed in this study. An IPRP-LC method in the first dimension (1D) provided the selectivity for the separation of polar analytes, using a 100% aqueous mobile phase containing phosphate buffer and ion-pair reagent. Heart cuts of target peaks were collected with sample loops and transferred to the second dimension (2D) HILIC column using an organic-rich mobile phase. In order to solve the mobile phase mismatch problem between the two dimensions, a make-up flow module was introduced in the 2D-LC system to dilute the 1D-water-rich fractions with acetonitrile before entering the sample loops. By optimizing the loop size and dilution factor, good retention and peak shape of the highly polar impurities were obtained on the 2D-HILIC column, and the ion suppression effect for MS detection from the ion-pair reagent and non-volatile salt in the 1D-effluent was minimized. A total of five impurities were identified through fragmentation studies by Q-TOF/MS analysis and their fragmentation pathways were proposed. Four of them were further confirmed by reference substances. This study not only provided useful information for quality control of calcium gluconate injections, but also provided an alternative method for polar impurity characterization in pharmaceuticals.

Diagnostic biosignature transformation under simulated martian radiation in organic-rich sedimentary rocks

As we look for traces of ancient life on Mars, we need to consider the impact of ionizing radiation in the biosignature preservation process. Here, we irradiated two organic rich terrestrial samples (Enspel and Messel shales) that have Martian analog mineralogies, with simulated cosmic rays to a dose of 0.9 MGy, equivalent of 15 million years of radiation exposure on the Martian surface. We compared a range of biosignatures before and after exposure, including total organic carbon, bulk stable carbon isotope ratios, diagnostic lipid biomarkers (hopanes and steranes), and Raman signatures akin to those collected by the Scanning Habitable Environments with Raman and Luminescence for Organics and Chemicals (SHERLOC) instrument on Perseverance. While we did not observe a significant difference in total organic carbon, bulk stable carbon isotopes, or Raman G-band signatures, we found that five lipid biomarkers decreased by a factor of two to three in the Enspel shale. This degree of degradation exceeds current predictions by existing models or experimental studies in organic rich samples and challenges our current understanding of complex biosignatures under ionizing irradiation.

Characterization of bituminite in Kimmeridge Clay by confocal laser scanning and atomic force microscopy

This work investigates bituminite (amorphous sedimentary organic matter) in Upper Jurassic Kimmeridge Clay source rock via confocal laser scanning microscopy (CLSM) and atomic force microscopy (AFM). These petrographic tools were used to provide better understanding of the nature of bituminite, which has been historically difficult to identify and differentiate from similar organic matter types in source rocks. As part of an International Committee for Coal and Organic Petrology (ICCP) working group, an immature (0.42% vitrinite reflectance), organic-rich (44.1 wt% total organic carbon content) sample of Kimmeridge Clay was distributed to multiple laboratories for CLSM characterization. The primary observations from CLSM imaging and spectroscopy include: 1) the interpreted presence of Botryococcus algae as a contributor to bituminite precursors; 2) color red-shift of sulfide reflectance and bituminite auto-fluorescence from below the sample surface; 3) positive alteration of bituminite from laser-induced photo-oxidation of the sample surface, including fluorescence blue-shift; 4) fluorescence blue-shift associated to higher fluorescence intensity regions in bituminite indicative of compositional (fluorophore) differences; 5) the need for fluorescence spectroscopy standardization as applied via CLSM; and 6) the suitability of CLSM fluorescence spectroscopy to predict solid bitumen reflectance from bituminite spectral emission via calibration to an extant dataset. Secondary CLSM observations include detection of reflected laser light from highly reflective inclusions in bituminite, including sulfides and fusinite, and radiolytic alteration of bituminite caused by substitution of U for Fe in sulfides. Findings from AFM include the observation that surface roughening or surface flattening of bituminite are induced by differential broad ion beam (BIB) milling and are dependent on the location and scale of AFM topology measurement. This result highlights our still limited understanding of the effects of BIB milling on sedimentary organic matter and indicates the need for further research before this technique can be advanced as a standard practice in petrographic sample preparation. Collectively, the results of this study illustrate the general applicability and versatility of AFM and CLSM as tools for organic petrology research, specifically for better understanding of the nature and properties of the bituminite maceral.

Influence of organic matter type on porosity development in the Wufeng-Longmaxi Shale: A combined microscopy, neutron scattering and physisorption approach

The upper Ordovician Wufeng Shale and lower Silurian Longmaxi Shale are part of the Fuling shale gas play located in the south-eastern part of the Sichuan Basin, southern China, representing the first commercial shale gas production project outside North America. We studied the occurrence of porosity at the micro- and nano-scale in samples of contrasting organic richness representing the typical lithofacies from the post-mature part of the Wufeng-Longmaxi gas play. Using a combination of site specific, high-resolution scanning and transmission electron microscopy with bulk measurements based on small angle neutron scattering and cryogenic Argon physisorption, along with conventional organic petrology, we highlight the impact of different types of organic matter (OM) (primary versus secondary) on the development of OM-hosted porosity. The results indicate that at the bulk scale the overall porosity in the samples is proportional to their organic content and organic hosted pore account for 30–40% of the total pore volume of the rocks. Nevertheless, most of the pores identified via electron microscopy imaging seem to reside in the organic matter, indicating that potentially a large part of the pores volume detected by neutron scattering and Argon physisorption is visually not detected. Organic matter focused nanoscale imaging revealed that mesopores are preferentially present in the solid bitumen and not in the primary detrital organic particles. Organic lean samples show low porosity and dominance of micropores, while organic-rich samples show higher porosity and a broader spectrum of pore sizes. Importantly, most of the meso pores are located in organic matter petrographically interpreted as solid bitumen, while detrital organic particles like graptolites show minimal visible porosity under high resolution electron microscopy and pore sizes in the micro pore range (i.e. <2 nm).Distinguishing between primary and secondary OM is therefore important for understanding the creation of an interconnected network of porous OM during hydrocarbon migration. This may have an important control on the estimation of gas in place and the gas transport properties of the shale.

The Sedimentary Geochemistry and Paleoenvironments Project.

The Sedimentary Geochemistry and Paleoenvironments Project.

Effects of Supercritical CO2 on Matrix Permeability of Unconventional Formations

We studied the effects of supercritical carbon dioxide (scCO2) on the matrix permeability of reservoir rocks from the Eagle Ford, Utica, and Wolfcamp formations. We measured permeability using argon before exposure of the samples to scCO2 over time periods ranging from days to weeks. We measured permeability (and the change of permeability with confining pressure) when both argon and scCO2 were the pore fluids. In all three formations, we generally observe a negative correlation between initial permeability and carbonate content—the higher the carbonate content, the lower the initial permeability. In clay- and organic-rich samples, swelling of the matrix resulting from adsorption decreased the permeability by about 50% when the pore fluid was scCO2 although this permeability change is largely reversible. In carbonate-rich samples, dissolution of carbonate minerals by carbonic acid irreversibly increased matrix permeability, in some cases by more than one order of magnitude. This dissolution also increases the pressure dependence of permeability apparently due to enhanced mechanical compaction. Despite these trends, we observed no general correlation between mineralogy and the magnitude of the change in permeability with argon before and after exposure to scCO2. Flow of scCO2 through μm-scale cracks appears to play an important role in determining matrix permeability and the pressure dependence of permeability. Extended permeability measurements show that while adsorption is nearly instantaneous and reversible, dissolution is time-dependent, probably owing to reaction kinetics. Our results indicate that the composition and microstructure of matrix flow pathways control both the initial permeability and how permeability changes after interaction with scCO2. Electron microscopy images with Back-Scattered Electron (BSE) and Energy Dispersive Spectroscopy (EDS) revealed dissolution and etching of calcite minerals and precipitation of calcium sulfide resulting from exposure to scCO2.

The organic output from mechanical-biological treatment plants as a source of microplastics: Mini-review on current knowledge, research methodology and future study perspectives.

Plastic pollution is one of the biggest environmental problems facing the world. In recent years, microplastics, polymer particles from 1 µm to 5 mm, have been getting much attention. The presence of microplastics has already been confirmed in aquatic and marine ecosystems, soil, atmosphere, biota, and others. The organic output from mechanical-biological treatment (MBT) plants was added to the list of microplastics sources only recently. However, according to preliminary estimates, it may be the second-largest source of microplastics. This article presents an overview of already published investigations on this microplastics source and explains the supposed pathway of microplastics in the MBT plants. The main waste treatment processes that can affect the amount of microplastics in the organic output have been identified as shredding, sieving and, to a lesser extent, aerobic or anaerobic processing. This mini-review also includes methods used in the scientific literature for microplastics extraction, purification, and identification in organic-rich samples, their advantages and limitations. Particular attention is paid to the methods of identifying the small microplastics, less than 1 mm, since the methods for particles 1-5 mm have been more extensively studied. Furthermore, future research needs are highlighted.

Composition of organic matter and thermal maturity of Mesozoic and Cenozoic sedimentary rocks in East Herzegovina (External Dinarides, Bosnia and Herzegovina)

This paper presents the first data on the organic matter and thermal maturity of Mesozoic and Cenozoic sedimentary rocks in the East Herzegovina region of the External Dinarides. Representative, organic-rich samples from outcropping sedimentary rocks of different ages in the area (Triassic to Neogene) were selected and analysed. The organic matter was studied by Rock-Eval pyrolysis and under the microscope in reflected non-polarized light and incident blue light. The results obtained show the presence of different types of organic matter in the area and thermal maturity stages from immature (Cenozoic) to early mature (Mesozoic). Vitrinite is abundant in the samples analysed, with the exception of Cretaceous samples that contain mostly lamalginite and bituminite. While measured vitrinite reflectance in end-member samples (Triassic shale 0.78 % Rr and Neogene coal 0.34% Rr) are in good correlation with the Tmax parameter from Rock-Eval pyrolysis. T max generally shows lower values in most Mesozoic samples. The organic petrographic data indicate that specific kerogen in Cretaceous and some Triassic sedimentary rocks is a probable reason for the significantly lower T max values. In addition, the results of pyrolysis documented before and after extraction revealed that free hydrocarbons (bitumen) in the surface samples analysed suppress the Tmax values.

Microplastics and Nanoplastics in the Freshwater and Terrestrial Environment: A Review

This review is a critical analysis of current freshwater and terrestrial research with an emphasis on transport, behaviour, fate and subsequent ecological impacts that plastic pollution poses. The current methods of extraction and evaluation of organic-rich samples are also explored for both micro- and nanoplastics. Furthermore, micro- and nanoplastics are discussed with reference to their environmental and health implications for biota. Regulations imposed on the manufacture and distribution of plastics globally are also noted. Within the review, the current literature has been presented and knowledge gaps identified. These include the characterization and quantification of micro- and nanoplastics entering and forming within the freshwater and terrestrial environment, the fate and behaviour of micro- and nanoplastics under varying conditions and the impacts of micro- and nanoplastics on freshwater and terrestrial ecosystems.

Variation in the diagenetic response of aragonite archives to hydrothermal alteration

Diagenesis of carbonate minerals is ubiquitous throughout the geologic record. Alteration is initiated immediately after deposition, or takes place in the endo- and exoskeletons as early as during the lifetime of a given carbonate-secreting biota, and can continue throughout the burial history of carbonate sediments and rocks. Variations in the diagenetic response of carbonate archives pose challenges for the reconstruction of past environmental conditions based on proxy data. This paper comparatively assesses alteration features of different aragonitic materials by experimentally-induced diagenesis. A multitude of factors lead to different reactivity and responses of a given aragonite archive, and provide insight to the interpretation of diagenetically altered material in the rock record. Chosen materials used in this study include relatively organic-rich samples such as coral skeletons and bivalve shells, and organic-lean abiotic carbonates such as speleothems and aragonite single crystals. Obtained datasets include distributions of elements, organics, carbon and oxygen isotope ratios, and crystallographic features. Observed variations in diagenetic responses include mineralogy of the diagenetic phases, rate and extent of mineral transformation, distribution of foreign ions in the crystal lattice (primarily Sr, Mg, and S), and the number of specific processes and products along diagenetic pathways. Alteration is shown to be primarily controlled by the initial diagenetic susceptibility of the sample (including porosimetry and structural characteristics, concentrations of organic material, and primary amounts of trace elements in the carbonate, such as Mg). Structural characteristics lead to initial internally “fluid-” or “rock-buffered” conditions, with low porosity and permeability resulting in a greater effect of internal fluids and organics. Differences in the amount of organic content and internal fluids affect transformation rates, secondary mineralogy, and isotope equilibria. Samples with relatively high porosity, high mineral transformation rates, and high primary Mg/Ca, may preferentially form secondary aragonite during fast equilibration with the diagenetic environment. Our results suggest that the degree and nature of diagenetic alteration of aragonite materials are strongly controlled by the micro- to nano-scale internal architecture governing the availability and transfer of aqueous fluids. Results of this study provide significant implications for the interpretation of diagenetic signals in carbonate archives, and have direct significance for the mechanistic understanding of carbonate diagenesis and (paleo)environmental conditions.

A new chemical separation procedure for the determination of rare earth elements and yttrium abundances in carbonates by ICP-MS

The determination of rare earth elements (REEs) and Y in carbonates can be complicated by low REE abundances and the presence of significant amounts of Ba resulting in problematic interferences when analysed by ICP-MS. We describe here a novel ion-exchange method using the DGA resin (TODGA), combined with addition of a Tm spike, which allows the separation of the REEs+Y as a whole prior to analysis using an Element XR ICP-MS. This method was validated with results obtained on three different reference carbonate materials (CAL-S, JLs-1 and BEAN, an in-house standard), yielding reproducibility levels better than 3% (RSD) in most cases. This new separation scheme is particularly well suited for carbonate samples having very low REE contents, but could be equally applied to various rock types and organic-rich sample matrices whenever quantitative Ba removal is required.