Source Of Organic Matter Research Articles

Palmitic Acid Is Not a Proper Salinity Proxy in Baffin Bay and the Labrador Sea but Reflects the Variability in Organic Matter Sources Modulated by Sea Ice Coverage

AbstractPalmitic acid (PA) is ubiquitous in the biosphere and its hydrogen isotopic composition (δ2HPA) was proposed as a potential paleoenvironmental proxy for salinity, with δ2HPA values increasing with salinity. In this study, we analyzed 40 surface sediment samples from Baffin Bay and the Labrador Sea to examine the isotopic composition of PA in relation to local environmental variables, including salinity. In contrast to expectations, our results show a negative relationship between the δ2HPA and sea‐surface salinity, raising questions about its pertinence and usefulness as a salinity proxy. Instead, our results suggest that the relative abundance of distinct organisms that employ different metabolisms is the key in determining the hydrogen isotopic fractionations in PA. While we show that PA is mostly produced through photoautotrophic metabolisms by diatoms and dinoflagellates, varying contributions from heterotrophic metabolisms may obscure the stable isotope composition of PA. Surprisingly, we found no correlation between the stable carbon isotopic composition of the sedimentary organic matter (δ13Corg) and PA (δ13CPA), implying major differences in either the dominant organisms producing sedimentary PA or in carbon isotope fractionation during lipid biosynthesis. We also found that the presence of extended sea‐ice cover leads to enriched carbon and hydrogen isotopic compositions in PA. These enriched values suggest heterotrophic biodegradation in the water column and/or in the sediment as well as an increase in grazing activities. We propose that sea‐ice cover and surface water oxygenation modulate the relative impact of phototrophic and heterotrophic metabolisms, and therefore the isotopic composition of marine sedimentary PA.

Effect of Organic Matter and Different Nitrogen Sources in Annual Ryegrass Cultivation on Forage Yield and Quality

Üretimde verim ve kaliteyi artırmak için gübre uygulaması vazgeçilmezdir. Yoğun tarımsal faliyetler sonucunda her geçen gün verim düşmekte ve çevre kirliliği artmaktadır. Bu çalışmanın amacı; farklı organik madde ve azot kaynaklarının tek yıllık çimin verim ve kalitesi üzerine etkilerinin belirlenmesidir. Çalışma 2018-2020 yıllarında tesadüf blokları deneme desenine göre üç tekrarlı olarak yürütülmüştür. Tek yıllık çim hiçbir uygulama yapılmadan (kontrol), çiftlik gübresi (3000 kg da-1), tavuk gübresi (300 kg da-1), leonardit (100 kg da-1), biyolojik gübre (serbest yaşayan azot bakterileri) ve kimyasal gübre (10 kg N da-1) uygulanmıştır. Bunun yanında %50 tek yıllık çim + %50 fiğ, %50 tek yıllık çim + %50 yem bezelyesi olacak şekilde ikili karışım yapılmıştır. Tek yıllık çimin en yüksek yeşil ve kuru ot verimi çiftlik gübresinde belirlenirken, en düşük verim tek yıllık çimin yem bezelyesi ve fiğle yapılan ikili karışımlarında belirlenmiştir. Uygulanan bütün gübrelerde HP (ham protein), NDF (nötr deterjanda çözünmeyen lif), DMD (sindirilebilir kuru madde) ve ham kül oranları benzer olmuş, yem bezelyesi ve fiğin tek yıllık çimle yapılan ikili karışımlarında ham protein, DMD ve ham kül oranları yüksek, NDF oranı ise düşük çıkmıştır. Otun ADF (asit deterjanda çözünmeyen lif) oranı en yüksek çiftlik gübresinde çıkmıştır. Elde edilen sonuçların ışığında çiftlik gübresinin verimi önemli derecede artırdığı, otun kalitesinde de olumlu bir etkisinin olduğu belirlenmiştir. Tek yıllık çim yetiştiriciliğinde çiftlik gübresi tavsiye edilebilir.

Sedimentary diterpane origins—inferences from oils of varying source depositional environment and age

The potential of C20 tricyclic and tetracyclic diterpane distributions in oils (and by extension, rock extracts) to aid the interpretation of sources of organic matter and depositional environments—spanning carbonate, marl, freshwater and saline lacustrine, normal marine and transitional—from Neoproterozoic to Neogene, is investigated using GC-MS and GC-MS-MS analysis of a range of oils of known origin. Contributions from gymnosperms are readily distinguished by abundant characteristic tricyclics and/or tetracyclics [e.g., 5β(H)-rimuane, 5β(H)-rosane, isopimarane and phyllocladanes]. Even at low levels, phyllocladane appears a reliable indicator of Carboniferous or younger source. A fairly uniform, limited range of diterpanes at relatively low abundance is observed in oils from other sources, with the 13β(H),14α(H)-cheilanthane often being the most abundant C20 diterpane associated with carbonates and marls. Other tricyclics include the previously proposed 8β-methyl-13α-ethylpodocarpane and a series of unidentified compounds, mostly sharing mass spectra with abundant fragment ions at m/z 123, 163 and 191, together with methyl (m/z 261), but not ethyl, loss from the molecular ion. This limited range of tricyclics suggests a common group of source organisms (probably bacterial) and or diagenetic transformation resulting in a few thermodynamically stable products. It may explain why pimarane is at most a trace component, despite pimaroids being widely occurring natural products. Where gymnosperms have made little contribution, C20 tetracyclic diterpanes are typically sparse and comprise beyerane, atisanes and possibly also 16α(H)-kaurane (which co-elutes with the first of the pair of atisane isomers), with beyerane usually the most abundant in terms of m/z 276→123 response. These compounds are not detected in oils from Neoproterozoic and Cambrian carbonates, but analysis of more samples is required to confirm this trend. Despite some caveats, diterpane distributions can provide useful information related to age and depositional environment as well as providing a tool for oil-oil correlation.

Combined use of positive matrix factorization and 13C[sbnd]15N stable isotopes to trace organic matter-bound potential toxic metals in the urban mangrove sediments

Coastal sediments act as sinks of sediment organic matter (SOM) and metals because of their special land–sea location and depositional properties. However, there are few reports on the correlation between the sources of organic matter (OM) and associated potential toxic metals (PTMs). In this study, we combined CN stable isotope analysis and positive matrix factorization to identify the matter and metal sources of OM and glomalin-related soil protein (GRSP) in an estuary under several decades of urbanization. The results of the positive matrix factorization (PMF) reveal a correlation between the sources of total sediment metals and the sources of OM-related metals. The sources of both SOM-bound PTMs and GRSP-bound PTMs are significantly related to the sources of total PTMs. OM sources were elucidated through 13C-15 N stable isotopes, and the potential sources of different types of OM differed. In addition, there is a significant correlation between OM-associated PTMs and organic matter sources. Interestingly, the functional groups of SOM were mainly influenced by multiple PTM sources but no OM source, while the functional groups of GRSP were regulated by a single metal source and OM source. This study deepened the understanding of the coupling between PTMs and SOM. The possibility of combined use of positive matrix factorization and 13C-15 N stable isotope tracing of metals as well as the sources of each metal fractions has been evaluated, which will provide new insights for the transportation of PTMs.

Characterization and sources of water-soluble organic species in PM2.5 in a remote mountain environment in Southeastern China

A comprehensive campaign was conducted in 2014–2015 to characterize and identify potential sources of water-soluble organic matter (WSOM) in a remote mountain area in Southeastern China. Weekly measurements of PM2.5 and its dominant chemical components, including organic carbon (OC), elemental carbon (EC), water-soluble inorganic ions (WSIIs), water-soluble organic carbon (WSOC), Humic-like Substances (HULIS), water-soluble organic species (sugar alcohols, anhydrosugars, primary sugars, and carboxylic acids), and trace elements were conducted. PM10, PM2.5, NO2, O3, and meteorological parameters were also routinely measured at the same site. WSOM was dominated by HULIS (49%), carboxylic acids (12%), and saccharides (3%, a sum of sugar alcohols, anhydrosugars, and primary sugars). Carboxylic acids exhibited a flat seasonal variation, while high mass concentrations of sugar alcohols and anhydrosugars were observed in summer and winter, respectively. The converting factor from WSOC to WSOM was estimated to be 2.1 for this mountain site. Six major source factors were identified for WSOM using positive matrix factorization (PMF) analysis, which include aqueous processes, biogenic secondary organic aerosols (SOAs), biomass burning, mixed urban aerosols, soil dust, and secondary nitrate. These factors contributed 34 ± 22%, 20 ± 24%, 18 ± 18%, 14 ± 8%, 10 ± 13%, and 5 ± 10%, respectively, to annual WSOM mass concentration. Results of this study suggest that aqueous chemical reactions of gaseous pollutants during the transport process, the transport of biomass burning, urban aerosols and dust storm, and local formation of biogenic SOAs contributed to WSOM in the remote area of Southeastern China.

Spatiotemporal variability of dissolved inorganic macronutrients along the northern Antarctic Peninsula (1996–2019)

AbstractThe northern Antarctic Peninsula is a key region of the Southern Ocean due to its complex ocean dynamics, distinct water mass sources, and the climate‐driven changes taking place in the region. Despite the importance of macronutrients in supporting strong biological carbon uptake and storage, little is known about their spatiotemporal variability along the northern Antarctic Peninsula. Hence, we explored for the first time a 24‐year time series (1996–2019) in this region to understand the processes involved in the spatial and interannual variability of macronutrients. We found high macronutrient concentrations, even in surface waters and during strong phytoplankton blooms. Minimum concentrations of dissolved inorganic nitrogen (DIN; 16 μmol kg−1), phosphate (0.7 μmol kg−1), and silicic acid (40 μmol kg−1) in surface waters are higher than those recorded in surrounding regions. The main source of macronutrients is the intrusions of Circumpolar Deep Water and its modified variety, while local sources (organic matter remineralization, water mass mixing, and mesoscale structures) can enhance their spatiotemporal variability. However, we identified a depletion in silicic acid due to the influence of Dense Shelf Water from the Weddell Sea. Macronutrient concentrations show substantial interannual variability driven by the balance between the intrusions of modified Circumpolar Deep Water and advection of Dense Shelf Water, which is largely modulated by the Southern Annular Mode (SAM) and to some extent by El Niño‐Southern Oscillation (ENSO). These findings are critical to improving our understanding of the natural variability of this Southern Ocean ecosystem and how it is responding to climate changes.

Molecular fossil chronicles and geochemical probes of Paleogene coals from Meghalaya, India

The Paleogene coals from the Jaintia, Khasi, and the Garo hills of Meghalaya, India, are studied for biomarker distributions, carbon isotope signatures (δ13Cbulk), and Rock-Eval pyrolysis (REP) to elucidate their organic matter (OM) source, depositional environment, thermal maturity, and hydrocarbon generation potential. Sulfur-rich OM (1.52 wt%–24.57 wt% S dry-basis) with Hydrogen Index (HI) values ranging from 172 mg HC/g TOC – 353 mg HC/g TOC suggest the presence of type IIS-IIIS admixed kerogen. Mixed gymnosperm – angiospermous OM input to the peatland is implied by δ13Cbulk values spanning from −26.7‰ to −25.5‰, −27.4‰ to −25.1‰, and −27.0‰ to −25.2‰ in the Jaintia, Khasi, and Garo coals, respectively. Further, the presence of pimarane, isopimarane, labdane, rimuane, phyllocladanes, and ent-beyerane, mark the conifer OM input, substantiated by the 1,7-dimethylphenanthrene (1,7-DMP), 1,6-dimethylnaphthalene (1,6-DMN), and 1,2,5- trimethylnaphthalene (1,2,5-TMN) compounds. The abundances of these gymnosperm markers decline from the Garo to the Jaintia coals implying plausible shifts in paleovegetation. Compound A from the oleanoid skeleton and subordinate amounts of oleanane indicate variable contributions from angiosperms. The oleanane index declines from the Garo to Jaintia coals suggesting a lower contribution of angiospermous OM from Garo to the Jaintia samples, which may also indicate a shift in the OM depositional environment towards the Jaintia Hills. Dibenzothiophene isomers increase while dibenzofuran isomers decrease from the Garo to Jaintia coals suggesting shifts from terrestrial to marginal marine depositional environment. Additionally, the gammacerane index increases from the Garo to Jaintia coals implying a transition from a stratified brackish water column or marine transgression to the peatland of the Jaintia Hills. Moreover, the studied coal samples exhibit variable thermal maturity. The mean random vitrinite reflectance of the Garo coals (R¯r=0.48%–0.61%) indicates subbituminous to bituminous rank, while the Khasi (R¯r=0.44%–0.60%) and Jaintia coals (R¯r=0.26%–0.75%) belong to subbituminous to bituminous D, and lignite to bituminous C rank, respectively. Tmax of these coals ranges from 414 °C to 446 °C, indicating the samples span from pre-catagenetic to catagenetic stages of maturation. Saturated C32-bishomohopane epimer and C30 βα-moretane/αβ-hopane ratios, along with aromatic MPI-3 and 3-MP/retene ratios, exhibit an increasing maturity trend from the Garo Hills to the Jaintia Hills samples.

Paleohydrological changes during the Late Holocene recorded in the sediments of two mountain lakes in the Tatra Mountains (Central Europe)

Changes in local hydrological and climatic conditions over the last 5500 years have been reconstructed based on geochemical and paleobiological features recorded in the sediments of two mountain lakes. The lakes are located in the Tatra Mountains, in the highest mountain range of the Carpathians (Central Europe), which during the Holocene constituted an important climatic barrier. Because both studied lakes are relatively shallow, even relatively minor fluctuations in water level are clearly recorded both in the geochemical characteristics of the sediments and in the phyto- and zooplankton communities. The multiproxy records indicate several periods of high water stands: 5.4–5.2 ka, 3.5–2.7 ka, 1.4–1.0 ka and 0.5–0 ka, and prominent dry periods 2.7–2.1 ka and 1.7–1.5 ka. Comparison of the reconstructed water levels of the Tatra lakes with records from other European regions suggests that at the boundary of the Middle and the Late Holocene, the hydrological conditions in the Tatras were similar to those in Western and Central Europe. Later, beginning approximately 3500 years ago, records from the Tatras, the northern surroundings of the Pannonian Basin, and the southern part of the Carpathians were unified. In addition to changes in local and regional hydrology, the records from the studied lakes allowed us to reconstruct changes in lake productivity. Relatively high δ13C values, compared to the sedimentary organic matter of other lakes in the region, point to in-lake primary production as a major source of sedimentary organic matter in both lakes. The stable C:N ratio values suggest a constant proportion of organic matter coming from in-lake primary production and transported from the lake catchment. However, the amount of organic carbon and nitrogen and, most of all, differences in the composition of stable C and N isotopes indicate changes in the lake environment. These changes were correlated with some paleotemperature proxies from the region.

High-resolution record of temporal change in organic matter burial over the past ∼8,600 years on the northwestern continental slope of the South China Sea

Sedimentary organic matter (SOM) on continental slopes in marine regions can sensitively record climatic and environmental changes. In this study, total organic carbon content (TOC), total nitrogen content (TN), and their stable isotope compositions (δ13C and δ15N) for sediments of core G02 were investigated (at ∼24.2-year resolution) to reveal the temporal variations in organic matter sources and the main controls on the sources and distribution of buried organic matter on the northwestern continental slope of the South China Sea over the last ∼8600 years. Results of a δ13C binary mixing model reveal that ∼82.3 ± 3% of SOM is derived from marine autochthonous sources. We suggest that the carbon and nitrogen contents and compositions of SOM are governed by distinct factors. The more positive δ15N values before the Pulleniatina Minimum Event occurrence are ascribed to stronger subsurface water intrusion by the Kuroshio Current, which led to enhanced subsurface denitrification and in turn counteracted the effect of mixing with surface water caused by the East Asian winter monsoon. Sedimentary δ13C values show a fluctuant decrease during ca. 8.6–3.0 cal kyr BP and a conspicuous increase during ca. 3.0–1.4 cal kyr BP. These changes are attributed to the decrease of marine productivity induced by the continuous weakening East Asian monsoon effect and the decrease of terrigenous organic carbon input induced by the weakened Indian summer monsoon precipitation, respectively. Since ca. 1.4 cal kyr BP, human activities have become the dominant factor in controlling the production and distribution of organic carbon. The results provide an important basis for understanding of source-sink processes of organic matter and the factors influencing these processes on continental slopes in low-latitude marginal seas.

Terrestrial versus aquatic source identification of sedimentary n-alkane and sugar biomarkers: a case study from the Bale Mountains, Ethiopia

Organic matter in sedimentary archives is abundantly used to reconstruct paleoenvironmental and climate histories. Thereby, distinguishing between the terrestrial and aquatic origin of sedimentary organic matter is often a prerequisite for robust interpretations. In this case study, we use published data for modern plants and topsoils to identify the terrestrial versus aquatic source of n-alkane and sugar biomarkers in two afro-alpine sediment archives (Lake Garba Guracha and Depression B4) in the Bale Mountains, Ethiopia. The results of our comparative approach show that the long-chain n-alkanes C29, C31, and C33 in the sedimentary archives yielded patterns similar to those typical for the potential terrestrial input. By contrast, the relative abundances of the sedimentary mid-chain n-alkanes C23 and C25, and at least partly C27, are significantly increased compared to the plants and topsoils. This suggests that they are primarily produced by aquatic macrophytes and micro-organisms. The Paq ratio (C23 + C25)/(C23 + C25 + C29 + C31) is validated as a suitable source identification proxy in our study area. The sugar biomarkers xylose (xyl) and arabinose (ara) are abundant in the plant and topsoil samples. By comparison, high relative abundances of fucose (fuc) and rhamnose (rham) are generally only observed in sediments. This indicates that these sugar biomarkers are primarily produced by aquatic macrophytes or micro-organisms. Therefore, the ratio (fuc + rham)/(ara + xyl) is a suitable sugar biomarker proxy for organic matter source identification. The relative abundances of galactose and mannose are systematically decreasing and increasing, respectively, from leaves over O-layers to Ah-horizons. Furthermore, they are not significantly different from the abundances found in the sediments. This hinders terrestrial versus aquatic source identification using galactose and mannose.

Gas ebullition associated with biological processes in radioactively contaminated reservoirs could lead to airborne radioactive contamination

BackgroundStorage reservoirs of radioactive waste could be the source of atmospheric pollution due to the efflux of aqueous aerosol from their water areas. The main mechanism of formation of aqueous aerosols is the collapse of gas bubbles at the water surface. In this paper, we discuss the potential influence of biological factors on gas ebullition in the water areas of the radioactively contaminated industrial reservoirs R-9 (Lake Karachay) and R-4 (Metlinsky pond) of the Mayak PA. The emission of the released non-dissolved gases captured with gas traps in reservoir R-9 was (88–290) ml/m2 per day (2015) and in reservoir R-4 (270–460) ml/m2 per day (2016). The analysis of gas composition in reservoir R-4 (60% methane, 35% nitrogen, 2.4% oxygen, 1.5% carbon dioxide) confirms their biological origin. It is associated with the processes of organic matter destruction in bottom sediments. The major source of organic matter in bottom sediments is the dying phytoplankton developing in these reservoirs. ConclusionThe obtained results form the basis to set a task to quantify the relationship between the phytoplankton development, gases ebullition and radioactive atmosphere contamination.

Integrative study of Permian coal-bearing horizons: biostratigraphy, palaeovegetation, and palaeoclimate in the South Karanpura Basin.

The article deals with the integrated and comprehensive study of the coal-bearing horizons from the South Karanpura Basin to delineate the biostratigraphy, palaeovegetation, palaeodepositional settings, and palaeoclimate in and around the investigated area during the deposition of Permian sediments. Highly diversified megafloral assemblages consist 13 genera and 72 species of order Glossopteridales, Cordaitales and Equisetales are documented among which 37 taxa are newly reported from Barakar and Raniganj formations of the area. Palynoassemblages-I and -II are recovered, which demonstrate the biostratigraphic age as Kungurian and Wordian-Capitanian, respectively. Overall the vegetation represents a luxuriant forest subjugated by arborescent deciduous trees bearing Glossopteris foliage with some conifers, cordaites, filicales, and peltaspermales. The biomarker study of the basin illustrates the unimodal distribution of n-alkanes in the sample set ranges from C14 to C29 which suggests major input from a single source of organic matter. The involvement of microbial activity and algal input is suggested for the basin. A relatively moderate-to-high water level condition can be inferred from elevated n-C25. The high CIA, PIA values and A-CN-K plot suggest intense weathering conditions in the source area. The source rocks are characterized by mature clayey type with abundant clay mineral, i.e., kaolinite. The current study portrays that the Permian climate was cooler in initial phase, which later on became warm temperate with high humidity. The palaeofloral entities and geochemical parameters suggest absolute diversification of Permian flora, the existence of continental freshwater setting in the vicinity and oxic to anoxic environment with fluctuating ground water conditions during the deposition of sediments.

Formation mechanism of organic-rich mixed sedimentary rocks in saline lacustrine basin, Permian Lucaogou Formation, Jimsar Sag, Junggar Basin, Northwest China

The organic-rich mixed sedimentary rocks deposited in a saline lacustrine environment are widespread in the Lucaogou Formation (P2l), Jimsar Sag, Junggar Basin. These rocks have complex lithology (mainly including mudstone, dolomitic mudstone and argillaceous dolomite) and significant changes in geochemical characteristics. Presently, the formation mechanism of organic-rich mixed sedimentary rocks in the P2l of the Jimsar Sag is obscure. To address these issues, the formation mechanism of mudstone, dolomitic mudstone and argillaceous dolomite is revealed by evaluating their sedimentary environment, primary productivity and sources of organic matter using organic petrology, organic geochemistry and inorganic geochemistry. The results show that the mixed sedimentary rocks of the P2l exhibit excellent hydrocarbon generation potential. The mixed sedimentary strata were mainly deposited in saline and suboxic to anoxic water column, and the main source of organic matter was aquatic organisms. During the changes from mudstone, dolomite mudstone to argillaceous dolomite deposition, the paleoclimatic condition varied from warm-humid to arid-hot with more frequent hydrothermal activity, which enhanced the salinity of the water column, leading to a higher proportion of halotolerant algae (cyanobacteria and green algae). The improvement in the paleoproductivity caused by volcanic activity was the most critical factor to promote the enrichment of organic matter in the mixed sedimentary rocks. In addition, the decomposition of algae and stratified water column were conducive to the formation of a stable and suboxic to anoxic bottom water environment, which improves the preservation conditions of organic matter, and also favored the organic matter enrichment in mixed sedimentary rocks. Therefore, the frequent changes in paleoclimatic conditions and periodic hydrothermal activity controlled the formation of different lithologies in the P2l. High primary productivity and good preservation conditions promoted the accumulation of organic matter in these mixed sedimentary rocks.

Empirical testing of cryoconite granulation: Role of cyanobacteria in the formation of key biogenic structure darkening glaciers in polar regions.

Cryoconite, the dark sediment on the surface of glaciers, often aggregates into oval or irregular granules serving as biogeochemical factories. They reduce a glacier's albedo, act as biodiversity hotspots by supporting aerobic and anaerobic microbial communities, constitute one of the organic matter (OM) sources on glaciers, and are a feeder for micrometazoans. Although cryoconite granules have multiple roles on glaciers, their formation is poorly understood. Cyanobacteria are ubiquitous and abundant engineers of cryoconite hole ecosystems. This study tested whether cyanobacteria may be responsible for cryoconite granulation as a sole biotic element. Incubation of Greenlandic, Svalbard, and Scandinavian cyanobacteria in different nutrient availabilities and substrata for growth (distilled water alone and water with quartz powder, furnaced cryoconite without OM, or powdered rocks from glacial catchment) revealed that cyanobacteria bind mineral particles into granules. The structures formed in the experiment resembled those commonly observed in natural cryoconite holes: they contained numerous cyanobacterial filaments protruding from aggregated mineral particles. Moreover, all examined strains were confirmed to produce extracellular polymeric substances (EPS), which suggests that cryoconite granulation is most likely due to EPS secretion by gliding cyanobacteria. In the presence of water as the only substrate for growth, cyanobacteria formed mostly carpet-like mats. Our data empirically prove that EPS-producing oscillatorialean cyanobacteria isolated from the diverse community of cryoconite microorganisms can form granules from mineral substrate and that the presence of the mineral substrate increases the probability of the formation of these important and complex biogeochemical microstructures on glaciers.

Biomarker characteristics of the heterocyclic and polycyclic aromatic hydrocarbons in the crude oils from West Siberian Basin, Russia: an implication for correlation with organic matter input, depositional environment and maturity

The distribution of aromatic hydrocarbon in sediments and oils is known to be affected by thermal maturity, source input and depositional conditions. Hence, the aromatic hydrocarbon fraction of four oil samples from different wells of the West Siberian Basin (central Russia) was investigated to determine the source of organic matter (OM), depositional environment and maturity of their source rocks. Biomarker ratios and parameters of aromatic compounds indicate that the studied oils were generated from clay-rich source rocks containing a mixed organic matter of marine and terrestrial origin, which were deposited in freshwater/deltaic to marine environmental settings under suboxic to relatively oxic conditions. Furthermore, the maturity-sensitive aromatic hydrocarbon parameters indicate that the source rocks are thermally mature, and in the peak to late maturity stage of the oil generation window. Oil–oil correlation results of various established aromatic biomarker proxies for organic matter origin, depositional environment and lithology suggests that the analyzed west Siberian Basin’s oils were generated from a variety of geological sources and can be grouped into two distinct oil families. The first oil family (group I) was generated from clay-rich source rock containing mixed organic matter with relatively high amounts of terrestrial plant input and deposited in a non-marine (freshwater/deltaic) environment under relatively oxic conditions, while the second oil family (group II) was derived from mixed organic matter with high marine OM input that was deposited in marine environment under suboxic conditions. The findings of the heterocyclic and polycyclic aromatics highlighted in this study can help for better understanding of the genetic ties between oils and their sources and have an impact on traditional hydrocarbon development in the Basin.

Composition and sources of suspended particles in the Pacific Arctic region

During the 6th (2014) and 7th (2016) Chinese Arctic Expedition (CHINARE), samples of suspended particulate matter (SPM) were collected from both surface (depth: <1.0 m) and subsurface (depth: approximately between 10 and 150 m) waters over the northern shelf of the Bering Sea and in the western Arctic Ocean. To investigate the distribution and sources of organic matter in both the surface water and the vertical profile, the concentration and stable carbon isotopic composition of SPM, particulate organic carbon (POC), and particulate nitrogen (only in surface water samples) were determined, and some particle samples were selected for examination using scanning electron microscopy. Results showed apparent geographical partitioning and temporal variation in both the concentration and the composition of SPM. Higher SPM concentrations were observed in nearshore, shelf break, and sea ice edge areas; the distribution of POC concentration displayed a similar pattern, with higher values found from the northern part of the Bering Shelf to southern parts of the Chukchi Shelf. In surface water, SPM mainly comprised clay and detrital minerals with higher POC contents, lighter δ13C values, and higher POC/PN ratios, indicating organic matter predominantly derived from terrestrial sources in areas south of St. Lawrence Island and north of 73°N. The downward trend of heavier δ13C values, together with reduction in clay and detrital minerals, suggests that vertical transport of SPM is hindered by stratification, resulting in transport of terrestrial materials toward northern basin areas. In the Chukchi Slope and Canada Basin areas, extremely light δ13C values (as low as −33.41‰ PDB) were mainly observed at depths of 20–60 m, where the Polar Mixed Layer (PML) intersects with the Upper Halocline Layer (UHL). Under the condition of low sea ice extent in 2016, the POC-δ13C values were heavier in the PML than in the UHL in the Chukchi Slope and Canada Basin areas. These findings provide insights into the sources, transport, and fate of organic matter in the Pacific Arctic region, which have important implications for understanding the biogeochemical cycles and ecosystem dynamics in this remote and rapidly changing environment.

Evaluation of the distribution of N, P and organic matter in sediment and the pollution status of Lakes in southeastern Hubei Province, China

Eutrophication caused by nutrients and organic matter (OM) pollution is a common problem in the world. The contents of total nitrogen (TN), total phosphorus (TP) and OM in sediments were determined in four typical lakes in southeastern Hubei, China, in the spring of 2019, and their pollution status was evaluated by organic and comprehensive pollution indexes to identify pollution sources and provide specific directions for the pollution control in key areas of the lakes. We found the following: (1) Both nutrients and OM in Cihu Lake and Bao’an Lake were relatively high. Cihu Lake had the highest nutrient and OM in both surface and core sediments. TN, TP and OM in the surface sediments of Cihu Lake reached 700.9 mg/kg, 1668.8 mg/kg and 62.8 kg/g, respectively. The contents of nutrients and OM in Daye Lake and Liangzi Lake were relatively low. OM in these two lakes was significantly lower than that in the Cihu Lake (p < 0.05). (2) The organic pollution and comprehensive pollution revealed that the pollution level of Cihu Lake and Bao’an Lake was moderate to severe. The level of pollution in Daye Lake and Liangzi Lake was mainly mild and moderate. (3) TN pollution was the main factor affecting sediment pollution in the four lakes compared to TP. The risks associated with N pollution merit increased attention. (4) Correlation analysis showed that there was not always a significant correlation between nutrients and OM in surface sediments (p > 0.05). It indicated that the sources of nutrients and OM in sediments were not identical but were affected by many factors. However, the relationship between nutrients and OM was closer in core sediments. In the future, targeted measures should be taken to reduce sediment pollution based on specific pollution sources and pollution conditions in the four lakes, especially Cihu Lake.

Effects of organic matter in drinking water and wastewater on micropollutant adsorption to activated carbon

AbstractImproving the removal of micropollutants from wastewater effluent is crucial to protect surface water quality. This can be achieved by applying adsorption to granular activated carbon. However, activated carbon filters used for wastewater treatment have a shorter lifetime than filters used for drinking water production. It was assessed whether this is related exclusively to the higher organic matter concentration in wastewater effluent, compared to drinking water, or also to organic matter characteristics. Influent of activated carbon filters from a drinking water plant and wastewater effluent were used as organic matter sources, and their effect on micropollutant affinity for activated carbon and adsorption rate was compared at the same dissolved organic carbon concentrations. Organic matter characterization (excitation–emission matrices and parallel factor—PARAFAC—analysis) and fractionation methods, based on size and hydrophobicity, were combined to assess the relevance of specific components that affect micropollutant removal. The results show that both organic matter concentration and composition determine their effect on micropollutant affinity for activated carbon and adsorption rate. The affinity of micropollutants for activated carbon is more reduced in the presence of organic matter from wastewater effluent. Adsorption rate is lower in the presence of organic matter originating from drinking water plants at levels around 10 mg/L, compared to wastewater effluent. One PARAFAC component is more abundant in drinking water organic matter and is likely responsible for this effect. This knowledge supports the development of strategies to overcome bottlenecks on the application of activated carbon filters in water treatment.

Distinct Modes of Aged Soil Carbon Export in a Large Tropical Lake Basin Identified Using Bulk and Compound‐Specific Radiocarbon Analyses of Fluvial and Lacustrine Sediment

AbstractThe 14C content of sedimentary organic matter (OM) and specific organic molecules provide valuable information on the source and age of OM stored in sediments, but these data are limited for tropical fluvial and lake sediments. We analyzed 14C in bulk OM, palmitic acid (C16), and long‐chain n‐alkanoic acids (C24, C26, and C28), within fluvial and lake sediments in the catchment of Lake Izabal, a large tectonic lake basin in Guatemala. We combined these measurements with bulk and compound‐specific δ13C measurements, as well as sediment organic carbon to nitrogen (OC:N) ratios, to understand the source and age of sedimentary OM in different regions of the lake catchment. Most fatty acid and bulk OM samples were characterized by pre‐modern carbon, indicating important input of aged carbon with residence times of hundreds to thousands of years into sediments. We identified two mechanisms leading to aged carbon export to sediments. In the high‐relief and deforested Polochic catchment, older OM and fatty acids are associated with low % total organic carbon (TOC) and low OC:N, indicating aged OM associated with eroded mineral soil. In the smaller, low‐relief, and largely forested Oscuro catchment, old OM and fatty acids are associated with high %TOC and high OC:N ratios, indicating export of undegraded aged plant biomass from swamp peat. The age of bulk OM and fatty acids in Lake Izabal sediments is similar to the ages observed in fluvial sediments, implying that fluvial input of aged soil carbon makes an important contribution to lake sediment carbon reservoirs in this large tropical lake.

Structure of coal-bearing sections of swampy coastal-marine lowlands of the Kama coal basin in the territory of the Tatarstan

The paper considers sections of the Visean coal-bearing formation of the Kama coal basin on the territory of the western slope of the South Tara arch. The sections are composed of coals, mudstones, siltstones, and sandstones, which were formed under continental conditions at the beginning of the Visean. The rocks of the coal-bearing formation were formed within the coastal shallow-marine plain with a lacustrine-marsh type of sedimentation. The formation of coals occurred during the formation of isolated swampy lakes on the surface of the floodplain lowlands. The source of organic matter was tree-like and herbaceous vegetation that develops in waterlogged lake water bodies in a hot, wet humid climate. According to the degree of coalification, coals belong to brown coals, their composition is dominated by a black, structureless, amorphous mass of coalified plant matter (fusen). As impurities, there are large fragments of plant remains belonging to the groups of intertinites and macerals. The coals are enriched in mineral, ash components, represented by kaolinite and finely dispersed quartz grains. Ash content will not exceed 20%.