High Organic Carbon Content Research Articles

Extreme eutrophication and salinisation in the Coorong estuarine-lagoon ecosystem of Australia's largest river basin (Murray-Darling)

Estuaries in rainfall poor regions are highly susceptible to climatic and hydrological changes. The Coorong, a Ramsar-listed estuarine-coastal lagoon at the end of the Murray-Darling Basin (Australia), has experienced declining ecological health over recent decades. Twenty years of environmental data were analysed to assess patterns and drivers of water quality changes. Large areas of the Coorong are now persistently hyper-saline (salinity >80 psu) and hypereutrophic (total nitrogen, TN > 4 mg L−1, total phosphorus, TP > 0.2 mg L−1, chlorophyll a > 50 μg L−1) which coincided with reduced flushing due to diminished freshwater inflows and increasing evapo-concentration. Sediment quality also was related to flushing, with higher concentrations of organic carbon, TN, TP and sulfides as salinity increased. While total nutrient levels are very high, dissolved inorganic nutrients are generally low. Increased lagoonal flushing would be beneficial to reduce the hypersalinisation and hypereutrophication and improve ecosystem health.

Study of Physiochemical Properties of Experimental Soil and Effect of Integrated Nutrient Management on Physical and Chemical Properties of Soil while harvesting of Phaseolus Vulgaris

As world population increases as day by day and to fulfill the need of food commodities, it is need to be applying the integral practices to enhance the soil fertility by improving the physical and chemical properties. In present study was done on, ‘Effect of Integrated Nutrient Management on Physical and Chemical Properties of Soil’. A field experiment was conducted in rabi 2005-2006 on experimental farm of department of ACSS, MAU, Parbhani to study, "Integrated nutrient management for Phaseolus Vulgaris (Rajma).Lowest bulk density of soil was observed due to application of only vermicompost. Wherever the highest bulk density was observed when only inorganic fertilizers were applied. Maximum water holding capacity of soil and porosity was recorded where vermicompost @ 5 tonnes ha-1 only was applied. Maximum water holding capacity was where 5 tonnes of vermicompost ha-1 with biofertilizers were applied. Maximum water holding capacity may be due to high organic carbon content resulting in soil aggregation. While these characters of soil were recorded minimum when only inorganic fertilizers were applied. The minimum porosity i.e., 48.60 per cent was recorded where 150% RDF of NPK/ha was applied through inorganic fertilizers. Soil pH and EC where highest only inorganic fertilizers were applied. The lowest pH and EC were recorded due to use of vermicompost only. The per cent organic carbon was highest in the soil where only vermicompost was applied only, whereas the lowest organic carbon was observed due to application of inorganic fertilizers.

Prediction of environmental factors responsible for chlorophyll a-induced hypereutrophy using explainable machine learning

Hypereutrophy of water bodies is an undesirable phenomenon due to the influence of a complex of environmental factors. The aim of the work was to predict the responsibility of environmental factors in changing water quality from eutrophic to hypereutrophic states. Hypereutrophy was defined as exceeding the concentration of chlorophyll a of 56 μg/L according to the Trophic State Index (TSI). The study was conducted on the Vistula Lagoon in the southern Baltic Sea. The work was carried out using the prediction and explanation ensemble XGBoost with SHAP modelling. On the global scale of the whole basin and at local sites, the importance of a number of physicochemical, nutritional and phytoplankton factors for hypereutrophy was calculated using mean Shapley values. High concentrations of organic carbon and nitrogen forms and, to a lesser extent, high water temperature mainly caused hypereutrophy. In the case of cyanobacterial biomass, the strong effect of low values of this factor maintains the eutrophic state more stable than higher values maintain hypereutrophy. XGBoost- SHAP modelling as an explanatory tool for the interpretation of water monitoring results can be useful for better management of coastal and inland waters.

Geochemistry of Precambrian black shales from Ossa-Morena Zone (Portugal): depositional environment and possible source of metals

The paleodepositional environments related to Ediacaran black shales from the Série Negra succession in Ossa-Morena tectonostratigraphic zone were investigated using their geochemical composition to identify the sedimentary sources and depositional conditions. Their potential for assisting the genesis of metal deposits was also discussed. The sedimentary sources of the black shales are related to the break up of a Cadomian magmatic-arc developed in the North Gondwana realm, where the Ossa-Morena Zone was located during late Ediacaran times, showing acidic to mixed signatures. Some ratios were calculated based on redox sensitive elements, indicating both anoxic and oxic paleoenvironmental conditions. The anoxic conditions were predominant and they were identified on samples with higher organic carbon content, emphasizing that the redox conditions favored organic matter preservation and the accumulation of selected metals. Considering the mode of occurrence, the elements Ag, Cd, Cu, Pb and Se are assumed to be preferentially associated with sulfides, whereas Mo and U are preferentially organically bound. The results reveal that the black shales from the Série Negra succession in Ossa-Morena Zone might represent a source of metals, which were probably remobilized during Variscan events.

Potential analytical interferences when measuring Tmax during temperature programmed pyrolysis of hydrothermally altered volcanoclastic sediment

AbstractThe temperature of maximum pyrolysis yield (known as Tmax) can be used to determine the level of thermal alteration in sedimentary organic matter; higher Tmax values represent higher thermal alteration. Tmax is commonly measured on petroleum source rocks or similar sediments with high organic carbon contents. It would be desirable to measure the Tmax of volcanic sediments because they can have complex patterns of thermal alteration. However, volcanic sediments often have low total organic carbon contents and consequently are susceptible to analytical interferences. Despite this, it can be shown that meaningful Tmax measurements can still be made in sediment with organic carbon contents as low as 0.2% and that interference caused by bitumen or ionizable salts can be mitigated by solvent extraction and rinsing with water. Thus, it is reasonable to use temperature programmed pyrolysis to assess levels of thermal alteration in even low total organic carbon volcanoclastic sediments.

An integrated petrophysical analysis based on NMR, organic geochemistry and mineralogy. The Vaca Muerta source rock-unconventional play at different thermal maturities

The Vaca Muerta Formation (Upper Jurassic–Lower Cretaceous) of the Neuquén Basin, Argentina is a world-class source rock and renowned as an unconventional reservoir for both oil and gas. The present study examines rotary sidewall cores representative of the oil and gas windows to analyze correlations between nuclear magnetic resonance (NMR T2 and T1-T2 maps at 2 MHz), Gas Filled Porosity (GFP), Rock-Eval programmed pyrolysis and quantitative X-ray diffraction (XRD) mineralogy. Shale samples are characterized by high present-day total organic carbon contents ranging from 3 to 7.20% (mean: 4.30%) for Well A at the oil window and, 0.72 to 11.77% (mean: 5.86%) for Well B at the gas window. The analyzed set also covers a wide compositional spectrum from carbonate-rich (> 50% of calcite and minor dolomite), mixed carbonate-siliciclastic (30 to 50% of calcite), to siliciclastic-rich (< 30% of calcite) samples. Notably, the clay fraction is dominated by interstratified illite-smectite minerals with less than 10% of expandable layers. Total porosity, calculated from Gas Filled Porosity plus NMR T2 Cumulative Distribution, is in the range of 10 to 20 porosity units. In this work we also present a new NMR sequence to detect solid-like organic matter with NMR at 2 MHz in an integrated workflow to characterize petrophysical properties of the Vaca Muerta Formation.

Organic matter accumulation mechanism under global/regional warming: Insight from the Late Barremian calcareous shales in the Qiangtang Basin (Tibet)

The Late Barremian (Early Cretaceous) is a global/regional warming interval. Deciphering the mechanism of organic matter (OM) accumulation in this interval could cast lights on OM accumulation mechanism under global/regional warming. This study presented high-resolution geochemical data of the Late Barremian marls and calcareous shales in the Qiangtang Basin to unravel the effect of paleoclimate and hydrothermal activity on OM enrichment, and to further discuss OM enrichment mechanism under warming climates. Our work revealed that the Late Barremian calcareous shales in the Qiangtang Basin showed high total organic carbon contents and were deposited under an anoxic-euxinic condition, high bioproductivity, and relatively stable high-salinity water mass. Hydrothermal activity was intense during this calcareous shale interval deposition. Hydrothermal fluids not only released reducing gas to increase the reducibility of water column, but also provided sufficient nutrients to enhance bioproductivity, thus facilitating the preservation and accumulation of OM. A climate transition from cold-arid to warm-humid occurred at the onset of calcareous shale deposition. A warming climate evidences in the late Barremian succession in the Qiangtang Basin suggested at least a regional warming event. The OM enrichment in the Late Barremian calcareous shales in the Qiangtang Basin was caused by the combined effect of regional (warming climate) and local (hydrothermal activity) factors. Accelerated hydrological cycle under warming climates promoted fluvial delivery of nutrients to sedimentary basins, and thus flourished bioproductivity. Local factors (e.g., hydrothermal activity and water-column stratification) facilitated OM accumulation and preservation under a warming setting.

Geochemistry and organic petrology of the bituminite shales from the Kapurdi mine, Rajasthan of NW India: implications for waxy oil generation potential

This study examines the geochemical and petrographic characteristics of seven bituminite shales from the Kapurdi mine in the Rajasthan, NW India, in order to assess their organic matter inputs and evaluate the oil-prone potentials. These bituminite shale samples exhibit high total organic carbon (TOC) content (up to 45.11 wt.%). The high TOC contents were correlated with low total sulfur content of less than 1 wt.% and suggest that these bituminite shales were deposited in a fresh lacustrine environment. The dominance of such lacustrine environmental setting was confirmed by the presence of the Botryococcus algae. The analyzed bituminite shales are characterized by a bimodal distribution of normal alkanes and relatively low isoprenoid Pr/Ph, Pr/n-C17 and Ph/n-C18 ratios. These characteristics suggest that these bituminite shales contain a blend of organic matter that was derived primarily from algal lacustrine and other aquatic organic matter, with terrigenous land plants and deposited under suboxic to anoxic environmental conditions. Such findings of the organic matter (OM) input and environmental conditions are consistent with mainly Types I and II kerogen and small amounts of Type II/III kerogen, thus yielding both oil and gas prone to higher concentrations of oil generation potential. The dominance of hydrogen-rich kerogen and oil generation potential is in agreement with the findings of high hydrogen index (HI = 240–425 mg HC/g TOC) and H/C atomic ratio of more than 1.20. The abundance of n-alkene and n-alkane doublets in the pyrolysis–gas chromatography (Py–GC) also indicates that these bituminite shales have potential to generate high concentrations of paraffinic waxy oil. Most of the maturity indicators show that the bituminite shales from the Kapurdi mine have not yet entered the main stage of oil generation window, exhibiting a range of immature stages. Therefore, as highlighted in this study, these bituminite shales can be considered as a good candidate for oil shale reoterting processes to release commercial amounts of oil upon using artificial heating techniques such as hydrothermal conversion.

The Soil Environment of Abandoned Charcoal Kiln Platforms in a Low-Altitude Central European Forest

This study examines the soil environment of eight charcoal kiln platforms and the neighboring soil in Czech and Bohemian low-altitude forest stands. Both mixed and undisturbed soil samples were used to assess the hydrophysical soil properties, nutrient content, cation exchange capacity, enzyme activity, and soil active carbon content, while soil color, stoniness, root density, and horizon thickness were estimated in the field. Charcoal-rich horizons had high total organic carbon concentrations and total nitrogen content (about 150% and 40% higher than in the organomineral horizons of the control plot, respectively), with total carbon stocks being higher than those in neighboring forest soils. Fine root density was highest in the charcoal-rich horizons, encouraged by high soil porosity, aeration, and favorable chemical properties. Enzyme group activity differed between individual soil horizons and kiln and control plots, with depolymerization enzyme activity highest in charcoal-rich horizons and humification enzyme activity highest in mineral horizons. Phosphatase, chitinase, and phenoloxidase activity were highest in charcoal-rich horizons, while β-glucosidase activity remained similar across horizons. After long-term abandonment, kiln sites shift from inhospitable sites to localized hotspots for plant and microbial growth, having more favorable physical, enzymatic, and chemical soil properties than the surrounding areas. This study confirmed that kiln production platforms act as microhabitat hotspots, also providing information on a wide spectrum of soil properties linked with soil microorganisms and root growth.

Grinding Beads Influence Microbial DNA Extraction from Organic-Rich Sub-Seafloor Sediment.

Sub-seafloor sediment is the largest microbial habitat on Earth. The study of microbes in sub-seafloor sediment is largely limited by the technical challenge of acquiring ambient microbial DNA because of sediment heterogeneity. Changes in the extraction method, even just by one step, can affect the extraction yields for complicated sediment samples. In this work, sub-seafloor sediment samples from the Baltic Sea with high organic carbon content were used to evaluate the influence of different grinding beads on DNA extraction. We found that the grinding beads can affect the DNA extraction from the organic-matter- and biosiliceous-clay-rich samples. A mixture of 0.5-mm and 0.1-mm grinding beads exhibited higher DNA yields and recovered more unique taxa than other bead combinations, such as Stenotrophomonas from Gammaproteobacteria and Leptotrichia from Fusobacteria; therefore, these beads are more suitable than the others for DNA extraction from the samples used in this study. This advantage might be magnified in samples with high biomass. On the contrary, the use of only small beads might lead to underestimation for certain Gram-positive strains. Overall, the discovery of abundant widespread deep biosphere clades in our samples indicated that our optimized DNA extraction method successfully recovered the in situ microbial community.

Regularities of distribution of particulation types of modern bottom sediments and organic carbon by depth in the western part of the Barents sea

In this article, the possibilities of statistical analysis methods were demonstrated on the example of studying modern bottom sediments in the western part of the Barents Sea. As a result of cluster and dispersion analyses, regularities in the distribution of granulometric types of modern bottom sediments and organic carbon dissolved in them with depth within the sublittoral and bathyal zones of the sea were established. Based on the results obtained, it was concluded that the size distribution of sediments was due to the mechanical differentiation of sedimentary material as it was transported by sea currents, as well as the distance from the main sources of drift — Novaya Zemlya, the Kola Peninsula and Svalbard. At the same time, the accumulation of organic carbon in bottom sediments was associated with the peculiarities of the distribution of communities of marine organisms within the considered facies zones. The high content of organic carbon in the bathyal zone of the sea was associated with an increase in primary productivity here, as well as with the transfer by sea currents of the accumulated biogenic material of the littoral and sublittoral zones towards the bathyal.

The Effect of Pyrolysis Temperature and the Source Biomass on the Properties of Biochar Produced for the Agronomical Applications as the Soil Conditioner.

Biochar is a versatile carbon-rich organic material originating from pyrolyzed biomass residues that possess the potential to stabilize organic carbon in the soil, improve soil fertility and water retention, and enhance plant growth. For the utilization of biochar as a soil conditioner, the mutual interconnection of the physicochemical properties of biochar with the production conditions used during the pyrolysis (temperature, heating rate, residence time) and the role of the origin of used biomass seem to be crucial. The aim of the research was focused on a comparison of the properties of biochar samples (originated from oat brans, mixed woodcut, corn residues and commercial compost) produced at different temperatures (400-700 °C) and different residence times (10 and 60 min). The results indicated similar structural features of produced biochar samples; nevertheless, the original biomass showed differences in physicochemical properties. The morphological and structural analysis showed well-developed aromatic porous structures for biochar samples originated from oat brans, mixed woodcut and corn residues. The higher pyrolysis temperature resulted in lower yields; however, it provided products with higher content of organic carbon and a more developed surface area. The lignocellulose biomass with higher contents of lignin is an attractive feedstock material for the production of biochar with potential agricultural applications.

Biocrust-linked changes in soil aggregate stability along a climatic gradient in the Chilean Coastal Range

Abstract. Biological soil crusts (biocrusts) composed of cyanobacteria, bacteria, algae, fungi, lichens, and bryophytes stabilize the soil surface. This effect has mainly been studied in arid climates, where biocrusts constitute the main biological agent to stabilize and connect soil aggregates. Besides, biocrusts are an integral part of the soil surface under Mediterranean and humid climate conditions, mainly covering open spaces in forests and on denuded lands. They often develop after vegetation disturbances, when their ability to compete with vascular plants increases, acting as pioneer communities and affecting the stability of soil aggregates. To better understand how biocrusts mediate changes in soil aggregate stability under different climate conditions, we analyzed soil aggregate samples collected under biocrust communities from four national parks in Chile along a large climatic gradient ranging from (north to south) arid (Pan de Azúcar, PA), semi-arid (Santa Gracia, SG), Mediterranean (La Campana, LC) to humid (Nahuelbuta, NA). Biocrust communities showed a stabilizing effect on the soil aggregates in dry fractions for the three northern sites and the wet aggregates for the southernmost site. Here, permanent vascular plants and higher contents of organic carbon and nitrogen in the soil control aggregate stability more than biocrusts, which are in intense competition with higher plant communities. Moreover, we found an increase in stability for aggregate size classes < 2.0 and 9.5–30.0 mm. The geometric mean diameter of the soil aggregates showed a clear effect due to the climatic gradient, indicating that the aggregate stability presents a log-normal instead of a normal distribution, with a trend of low change between aggregate size fractions. Based on our results, we assume that biocrusts affect the soil structure in all climates. Their role in aggregate stability is masked under humid conditions by higher vegetation and organic matter contents in the topsoil.

Molecular signature of soil organic matter under different land uses in the Lake Chaohu Basin

The concentration and molecular composition of soil organic matter (SOM) are important factors in mitigation against climate change as well as providing other ecosystem services. Our quantitative understanding of how land use influences SOM molecular composition and associated turnover dynamics is limited, which underscores the need for high-throughput analytical approaches and molecular marker signatures to clarify this etiology. Combining a high-throughput untargeted mass spectrometry screening and molecular markers, we show that forest, farmland and urban land uses result in distinct molecular signatures of SOM in the Lake Chaohu Basin. Molecular markers indicate that forest SOM has abundant carbon contents from vegetation and condensed organic carbon, leading to high soil organic carbon (SOC) concentration. Farmland SOM has moderate carbon contents from vegetation, and limited content of condensed organic carbon, with SOC significantly lower than that of forest soils. Urban SOM has high abundance of condensed organic carbon markers due to anthropogenic activities but relatively low in markers from vegetation. Consistently, urban soils have the highest black carbon/SOC ratio among these land uses. Overall, our results suggested that the molecular signature of SOM varies significantly with land use in the Lake Chaohu Basin, influencing carbon dynamics. Our strategy of molecular fingerprinting and marker discovery is expected to enlighten further research on SOM molecular signatures and cycling dynamics. High-throughput MS was used to screen SOM structures in Lake Chaohu Basin Spectrum processing algorithm was developed for profiling SOM molecular fingerprints Molecular markers were identified to reveal SOM signatures for different land uses Molecular signature of SOM varies significantly with land use in Lake Chaohu Basin

Preservation of Organic Matter in Aqueous Deposits and Soils Across the Mars‐Analog Qaidam Basin, NW China: Implications for Biosignature Detection on Mars

AbstractA variety of aqueous deposits and soils from gullies, fluvial channels, mountain slopes, alluvial fans, playas, polygons, and yardangs have been found on Mars. However, the occurrence of sedimentary organic matter (SOM) in these landscapes under hyperarid and strongly radiative conditions has yet to be fully assessed. With various desiccated landforms analogous to those on Mars, the Qaidam Basin in northwestern China is considered a promising hyperarid Martian analog. Here, aqueous deposits and soils from nine landforms across the extremely dry northwestern Qaidam and from four landforms across the dry southeastern Qaidam were sampled and investigated. Our results reveal that landform and moisture are important controls on organic carbon distribution across the Qaidam Basin, while sedimentary origin has a dominant effect in the extremely dry northwestern Qaidam. Combined with previous studies, low organic carbon contents of soils in the extremely dry northwestern Qaidam suggest possibly low rates of microbial carbon input and of organic carbon degradation in Mars‐like environments. High organic carbon contents of aqueous deposits together with increasing trends along rivers indicate preservation of relic SOM and possibly slow degradation rates of organic matter as compared to their exposure timescale. Moreover, soils from the distal alluvial fan are found to favor the concentration of pedogenic organic carbon as compared to those from other landforms in the dry southeastern Qaidam and from all landforms in the extremely dry northwest. This suggests that subsoils in the distal fans are promising candidate targets for biosignature detection on Mars.

Labile carbon input and temperature effects on soil organic matter turnover in subtropical forests

The objective of this study was to assess the effects of labile organic carbon (LOC) input on the dynamic turnover of soil organic matter (SOM) with temperature in subtropical forests. Soil samples were collected from three subtropical forests: an evergreen broadleaf forest, a mixed pine and broadleaf forest, and a pine forest. To simulate LOC inputs, soil samples were supplemented with 13C-glucose at levels of 0, 0.2, 0.6, and 1.2 mg C g−1 soil. The soils with the LOC treatments were incubated for six weeks at temperatures of 15, 25, and 35 °C. Results showed that the increase in LOC inputs reduced the priming effects of SOM decomposition significantly, whereas native SOM mineralization increased with temperature. The preferential utilization of LOC by microorganisms reduced SOM decomposition, resulting in net SOC increases with LOC inputs. In the temperature range, the net increases in SOC with the LOC inputs were −0.19 to 0.56 mg C g−1 soil. Moreover, the LOC inputs aided microbial anabolism and promoted the formation of new mineral-associated organic matter and the aggregation of particulate organic matter, resulting in carbon sequestration. Among the forest soils, the soil with the highest organic carbon content, total nitrogen, and carbon to nitrogen ratio (i.e., the mixed forest soil) had the lowest priming effects and was the most conducive to net carbon increase. The priming and carbon sequestration caused by the LOC inputs were not sensitive to temperature changes. Our findings suggest that the increase in the supply of LOC has the potential to alleviate SOM decomposition and increase carbon storage in subtropical forest soils.

Assessment of Available Macro and Micronutrient Status in Soils of Mansala-Kayikoro, Kita Mali

Background: The soil fertility assessment is crucial for sustainable agriculture and plant yields. The knowledge of the trophic level of agricultural soil fertility is mandatory in order to define the development of food crops due to the lack of soil fertility assessment in this region and the decrease in crop yields. Methods: In this context, an investigation was carried out to study the fertility status of the Mansala-Kayikoro soils and some essential soil properties, such as pH, CEC, OM, EC etc. Ten soil samples were collected from farming areas and analyzed for macronutrients, micronutrients and essential soil physicochemical properties. Result: Soils of the Kayikoro area were highly acidic to slightly acidic in reaction with a low to high organic carbon (OC) content. According to the data, the cation exchange capacity (CEC) was deficient. The available macronutrients such as N, P and K content in the soils were found below the requirement of plant. The concentration of micronutrients such as iron, copper, manganese and zinc was slightly low in the analyzed samples.

Insight into characteristics of sulphur-based autotrophic denitrifying microbiota in the nitrate removal

ABSTRACT Mariculture wastewater is characterized by low organic carbon to nitrogen ratio (C/N) but high nitrate concentration, which makes it difficult to remove nitrate by the completely heterotrophic denitrification. However, high nitrate discharge poses a threat to the natural environment and human health. Thus, we enriched sulphur-based autotrophic denitrifying (SAD) microbiota and optimized the nitrate removal under different environmental factors and electron donor conditions. The results showed that the dominant genera in the enriched microbiota were previously confirmed autotrophic denitrifiers, Sulfurovum, Thioalkalispira-Sulfurivermis, and Sedimenticola, with a high relative abundance of 41.14%, 21.01%, and 6.17%. Among the environmental factors, pH was the key factor affecting SAD microbiota, and pH 7–9 favoured nitrate removal. However, high pH led to nitrite accumulation (e.g. 10 mg/L at pH = 9), which should be strictly avoided. With regard to electron donors, the optimal concentrations of thiosulphate and nitrate were 50 and 5 mg/L, respectively. The best organic carbon is acetate with an optimal concentration of 10 mg/L. Meanwhile, the initial concentration of thiosulphate was proportional to the nitrate removal rate, while higher concentrations of organic carbon stimulated the heterotrophic denitrification potential of microbiota and thus benefited to dentrification. This study showed that the enriched SAD microbiota was able to achieve efficient nitrate removal under suitable environmental conditions and mixed electron donors and thus presented the potential for application in the treatment of mariculture wastewater.

Geochemical and Petrological Characterization of the Early Eocene Carbonaceous Shales: Implications for Oil and Gas Exploration in the Barmer Basin, Northwest India.

Carbonaceous shales of the Early Eocene Dharvi/Dunger Formation in the onshore Barmer Basin, northwest India were studied for the first time by integrating geochemical and organic petrological analyses. The carbonaceous shales of the Early Eocene Dharvi/Dunger Formation are characterized by a higher organic carbon content (TOC) of >10 wt % and consist mainly of a mixture of organic matter of types II and III kerogen, with exhibited hydrogen index values ranging between 202 and 292 mg HC/g TOC. The dominance of such kerogen is confirmed by the high amounts of huminite and fluorescent liptinite macerals. Consequently, the carbonaceous shales of the Early Eocene Dharvi/Dunger Formation are promising source rocks for both oil and gas generation potential, with oils of high wax contents, according to pyrolysis-gas chromatography results. The chemical and optical maturity results such as low values huminite/vitrinite reflectance, production index, and T max show that most of the examined carbonaceous shale rocks from the outcrop section of the Kapurdi mine have entered the low maturity stage of oil generation, exhibiting a range of immature to the very early-mature. Therefore, as highlighted in this study, the substantial abundance in hydrocarbon generation potential from these carbonaceous shales in the Dharvi/Dunger Formation may represent future conventional petroleum exploration in the southern part of the Barmer Basin, where the Dharvi/Dunger Formation has reached deeper burial depths.

Significant overestimation of black carbon concentration caused by high organic carbon in aerosols of the Tibetan Plateau

Black carbon plays an important role in climate change. Whereas, accurate measurement of black carbon (also known as elemental carbon (EC)) is still a challenging issue because portion of the pyrolytic carbon produced from the organic carbon (OC) can cause the overestimation of EC when measured by thermal-optical method. As one of the remote regions in the world, the Tibetan Plateau (TP) is characterized as high OC/EC ratio in its atmosphere. In this study, potential influence of relative high OC concentration to EC were investigated at three remote sites (Yaze, Everest and Nam Co) in the TP. The results showed that carbonaceous aerosols from different sources can affect the fraction of OC extracted by methanol. Concentration of OC extracted by methanol had a significantly positive correlation with the reduction of pyrolytic carbon and EC concentrations, indicating that part of OC extracted by methanol can decrease the production of pyrolytic carbon and then reduce the overestimation of EC. After considering this effect, it is shown in this study that actual EC concentration at Yaze, Everest and Nam Co were overestimated by approximately 40.0 ± 12.6%, 28.8 ± 9.1% and 24.8 ± 4.7%, respectively. Accordingly, combined with the overestimation of EC concentration by carbonates, actual ratios of solar energy absorbed by organic carbon to EC were 1.67, 2.33 and 2.78 times those of original ones at Yaze, Everest and Nam Co, respectively. Therefore, warming effect caused by EC on the TP should be lower than that previously estimated. This phenomenon needs to be considered for both in situ study and model simulation in the future.