High Organic Carbon Content Research Articles

Identification of methane cycling pathways in Quaternary alluvial-lacustrine aquifers using multiple isotope and microbial indicators

Groundwater rich in dissolved methane is often overlooked in the global or regional carbon cycle. Considering the knowledge gap in understanding the biogeochemical behavior of methane in shallow aquifers, particularly those in humid alluvial-lacustrine plains with high organic carbon content, we investigated methane sources and cycling pathways in groundwater systems at the central Yangtze River basins. Composition of multiple stable isotopes (2H/18O in water, 13C in dissolved inorganic carbon, 13C/2H in methane, and 13C in carbon dioxide) was combined with the characteristics of microbes and dissolved organic matter (DOM) in the study. The results revealed significant concentrations of biogenic methane reaching up to 13.05 mg/L in anaerobic groundwater environments with abundant organic matter. Different pathways for methane cycling (methanogenic CO2-reduction and acetate-fermentation, and methane oxidation) were identified. CO2-reduction dominated acetate-fermentation in the two methanogenic pathways primarily associated with humic DOM, while methane oxidation was more closely associated with microbially derived DOM. The abundance of obligate CO2-reduction microorganisms (Methanobacterium and Methanoregula) was higher in samples with substantial CO2-reduction, as indicated by isotopic composition. The obligate acetate-fermentation microorganism (Methanosaeta) was more abundant in samples exhibiting evident acetate-fermentation. Additionally, a high abundance of Candidatus Methanoperedens was identified in samples with apparent methane oxidation. Comparing our findings with those in other areas, we found that various factors, such as groundwater temperature, DOM abundance and types, and hydrogeological conditions, may lead to differences in groundwater methane cycling. This study offered a new perspective and understanding of methane cycling in worldwide shallow alluvial-lacustrine aquifer systems without geothermal disturbance.

Methane flux at the water-gas interface is influenced by complex interactions among phytoplankton, phosphorus inputs and methane-functional bacteria: A microcosm systems study

Phytoplankton affect carbon cycling and emissions in eutrophic reservoirs dramatically, but our knowledge about carbon emissions response to phytoplankton bloom and phosphorus enrichment is rather limited. Here we performed a microcosm experiment with five treatments to investigate how phytoplankton blooms and phosphorus addition will impact the carbon emissions and the methane-functional bacterial community. During the 43-day incubation, the CH4 and CO2 flux at the water-air interface in the five water columns fluctuated between 7.536 and 16.689 μmol and between 2788.501 and 4142.726 μmol, respectively. The flux of CH4 and CO2 during phytoplankton decay was 1.542 to 10.397 times and 4.203 to 8.622 times higher, respectively, compared to that during phytoplankton growth. Furthermore, exogenous phosphorus increases bloom biomass of phytoplankton and subsequent CH4 production, even with low nitrogen concentrations. The addition of 1 mg KH2PO4 resulted in a conservative increase of 0.0715 μmol in CH4 emission and 11.911 μmol in CO2 emission in the water column, respectively, compared to the in-situ water column. High throughput sequencing determined that hydrogenotrophic Methanoregula dominated methanogens (MPB) and Methylocystaceae dominated methanotrophs (MOB) in the sediment. Phosphorus inhibited the relative abundance of Methanoregula after incubation, resulting in a significant decrease. Real-time quantitative polymerase chain reaction indicated that the absolute abundance of MPB and MOB (i.e., the mcrA gene and the pmoA gene) in the sediments ranged from 5.1354E+06 to 6.3176E+07 copies·g−1 and 1.1656E+06 to 9.5056E+06 copies·g−1, respectively. The mcrA gene showed a preference for sediments with high organic carbon content. The effect of eutrophication on CH4 emissions is closely related to nutrient load and distinct niche of methane-functional bacteria.

Organic petrology and geochemistry of the Devonian-Mississippian bakken formation, Williston Basin, North Dakota

The Devonian–Mississippian (D–M) black shales of the Bakken Formation are of interest as a hydrocarbon source due to their high total organic carbon (TOC; 2.2–17.4%) content. The Upper and Lower Members of the Bakken Fm. are shallow marine (100–150 m) sequences. Thirty samples were selected for maceral identification, kerogen typing, and solid bitumen reflectance (SBRo) based on TOC content and down-core spacing. The shales contain alginite, bituminite, abundant solid bitumen (SB), and minor amounts of inertinite. Solid bitumen increases in quantity with increasing thermal maturity. Pyrolysis (85 samples) provided S1 (avg. 8.0 mg HC/g rock), S2 (avg. 24.3 mg HC/g rock), hydrogen index (HI; avg. 201 mg HC/g TOC), oxygen index (OI; avg. 7 mg CO2/g TOC), and Ro (0.60–1.03%) calculated from Tmax. Plots of HI vs. OI and HI vs. Tmax (°C) were used to assess kerogen type but are not consistently in agreement with the petrographic assessment. Some samples from more thermally mature cores plot as Type III (vitrinite) kerogen instead of Type II (alginite and bituminite) kerogen, the latter confirmed through petrographic observations of lower maturation samples. This is largely due to increased SB in more thermally mature samples (Ro = 0.83–1.03%), as SB is known to have a lower HI content than Type II kerogen. Petrographic data show more alginite and bituminite (19–55%) in the thermally less mature samples (Ro = 0.60–0.83%) compared to more dispersed SB (67–86%) and less alginite and bituminite (<1%) in the more thermally mature samples (Ro = 0.89–1.01%).Early research on the Bakken Fm. reported lower than expected vitrinite reflectance values and attributed them to vitrinite “suppression”. The scarcity of vitrinite and abundance of SB suggest that early work likely reported reflectance on SB. Recent attempts to assess the thermal maturity of the Bakken black shales have converted SBRo to vitrinite reflectance equivalence (VRE). However, there are multiple SB populations present in these shales and it is not always clear which SB populations were included, possibly contributing to error. In the current study, only smooth, homogenous SB was measured (0.68–1.14% SBRo) and VRE values calculated (0.54–1.49%) to assess thermal maturity from the basin margin to the depocenter; inclusion of measurements on granular, heterogeneous SB (14–21 vol%), which are ~53% lower than those for smooth, homogenous SB (3–12 vol%), results in lower mean reflectances, especially in more mature samples. Vitrinite reflectance equivalent data calculated using the D–M New Albany Shale equation of Liu et al. (2019) agrees with liptinite fluorescence and Rock-Eval Ro, whereas VRE based on the D–M Woodford Shale equation of Cardott and Comer (2021) does not. This suggests the importance of applying VRE equations from similar formations both in terms of thermal history, as well as kerogen type and age. Results from SBRo, Rock-Eval Ro, VRE, and observations of alginite fluorescence indicate that samples from the current study range from the early oil window into the condensate, wet gas zone.

Color origin and its sedimentary and paleoenvironmental significance of the Permian-Triassic strata in the Ordos Basin, China

The Permian-Triassic strata in the Ordos Basin deposit a colorful set of strata. Although there have been many studies on oil and gas resources here, little attention has been paid to the genesis mechanism of its color. To analyze the color origin of the Permian-Triassic claystones and to clarify the dialectical relationship between rock color and sedimentary environment, petrological and geochemical methods such as polarization microscope, scan electron microscope, X-ray diffractometer, and inductively coupled plasma-mass spectrometer are used. The results indicate that the minerals with different colors, composition, and content serve as colorants in sedimentary rocks, with the predominant dyeing component in dark claystones being the organic matter, whereas red beds primarily acquire their color from hematite and other ferric minerals. In addition, different rock colors correspond to distinct chemical composition variations. The black-gray rocks of the Yanchang and Shihezi Formations have high total organic carbon content, Fe2+/Fe3+, V/Cr, and low CaO/(MgO × Al2O3) and Sr/Cu, whereas the red-brown rocks of the Liujiagou and Heshanggou Formations exhibit the opposite. Therefore, different colors of the rocks stem from their different mineral and chemical compositions, which in turn influenced by the changes in the paleoclimate, paleoenvironment, and tectonic movements. Comprehensive analysis of color, mineral, and chemical composition reveals the evolution process of paleoclimate and paleoenvironment in the Ordos Basin from the late Permian to Triassic, beginning with a warm humid climate characterized by a weak oxidation environment in the Shihezi and Shiqianfeng Formations, transitioning to a hot arid climate in the Liujiagou and Heshanggou Formations, and returning to a warm humid climate with a weak oxidation environment in the Zhifang and Yanchang Formations. This evolution history aligns with the global tectonic and climate evolution. Overall, systematic analysis of sedimentary rock color can provide an important basis for the study of the paleoclimate and paleoenvironment.

Evaluation of Microbiological and Chemical Properties of Soils as a Result of Anthropogenic Denudation

Excessive agricultural intensification adversely affects soil quality, particularly in hilly terrain, leading to increased erosion. Anthropogenic denudation, intensified by tillage erosion, results in the displacement of soil material from hilltops and shoulders to their bases. The research hypothesis posits that tillage erosion adversely affects the microbiological and chemical properties of soils, especially at the hilltops of intensively cultivated areas. The study aimed to assess the microbiological and chemical properties of Luvisols cultivated under conventional plowing in the moraine region of the Southern Krajna Lakeland, Poland. The evaluation focused on the results of soil sample analyses taken from the hilltops and foothills of eroded mounds. Microbiological investigations included determining the abundance of actinomycetes, filamentous fungi, heterotrophic bacteria, cellulolytic microorganisms, copiotrophs, and oligotrophs. Additionally, pH values and the contents of phosphorus, potassium, magnesium, total organic carbon, and nitrogen were determined. A higher abundance of bacteria, actinomycetes, and copiotrophs was observed at the foothills. Statistically significant differences due to slope effects were noted for all chemical parameters, with higher concentrations of organic carbon, nitrogen, potassium, and phosphorus found in the foothill areas. Understanding denudation processes can contribute to sustainable soil resource use and agrocenosis conservation.

Carbon Storage Potential of Soil in Diverse Terrestrial Ecosystems

Soil is one of the largest carbon reservoirs sequestering more carbon than vegetation and atmosphere. Due to the enormous potential of soil to sequester atmospheric CO2, it becomes a feasible option to alleviate the current and impending effects of changing climate. Soil is a vulnerable resource globally because it is highly susceptible to global environmental problems such as land degradation, biodiversity loss, and climate change. Therefore, protecting and monitoring worldwide soil carbon pools is a complicated challenge. Soil organic carbon (SOC) is a vital factor affecting soil health since it is a major component of SOM and contributes to food production. This review attempts to summarize the information on carbon sequestration, storage, and carbon pools in the major terrestrial ecosystems and underpin soil carbon responses under climate change and mitigation strategies. Topography, pedogenic, and climatic factors mainly affect carbon input and stabilization. Humid conditions and low temperature favor high soil organic carbon content. Whereas warmer and drier regions have low SOC stocks. Tropical peatlands and mangrove ecosystems have the highest SOC stock. The soil of drylands stores 95% of the global Soil Inorganic Carbon (SIC) stock. Grasslands include rangelands, shrublands, pasturelands, and croplands. They hold about 1/5th of the world’s total soil carbon stocks.

Abundance, biomass and species richness of macrozoobenthos along an intertidal elevation gradient.

Ecology aims to comprehend species distribution and its interaction with environmental factors, from global to local scales. While global environmental changes affect marine biodiversity, understanding the drivers at smaller scales remains crucial. Tidal flats can be found on most of the world's coastlines and are particularly vulnerable to anthropogenic disturbances. They are important transient ecosystems between terrestrial and marine ecosystems, and their biodiversity provides important ecosystem services. Owing to this unique, terrestrial-marine transition, strong environmental gradients of elevation, sediment composition and food availability prevail. Here, we investigated which regional and local environmental factors drive the spatio-temporal dynamics of macrozoobenthos communities on back-barrier tidal flats in the East Frisian Wadden Sea. On the regional level, we found that species composition changed significantly from west to east on the East Frisian islands and that total abundance and species richness decreased from west to east. On the local abiotic level, we found that macrozoobenthos biomass decreased with higher elevation towards the salt marsh and that the total abundance of organisms in the sediment significantly increased with increasing mud content, while biodiversity and biomass were not changing significantly. In contrast to expectations, increasing Chl a availability as a measure of primary productivity did not result in changes in abundance, biomass or biodiversity, but extremely high total organic carbon (TOC) content was associated with a decrease in biomass and biodiversity. In conclusion, we found regional and local relationships that are similar to those observed in previous studies on macrozoobenthos in the Wadden Sea. Macrozoobenthos biomass, abundance and biodiversity are interrelated in a complex way with the physical, abiotic and biotic processes in and above the sediment.

Appraising the characteristics of particulate matter from leather tanning micro-environments, their respirational risks, and dysfunctions amid exposed working cohorts.

Leather tanneries are known for chemical laden work environments and pulmonic complaints among workers. This study presents an analysis of tannery micro-environments emphasizing on size-based variation in composition of particulate matter and consequent respiratory dysfunctions. Qualitative (FTIR, SEM-EDX) and quantitative assessment (elemental composition, carbon forms) of PM10 and 2.5 has been employed. For lung function evaluation of workforce, spirometry with ATS proprieties was used. The peak concentrations of both PM10 and 2.5 have been found at PU, FU, and B&S. The LTCR for only Cr is high for both PM2.5 and PM10. HQ was high for Al, Cr, and Mn for both PM sizes. The maximum organic and secondary organic carbon in PM10 was found at FU and in PM2.5 at PU. The varied PM composition included carbohydrate (B&S, WMO), ether (S&S, P&S) and hydroxyl (B&S, S&S, P&S), proteins, polyenes, vinyl groups (S&S, P&S, FU), alcohols (PU and FU), and aldehyde present at PU. These results were armored by high organic and total carbon concentrations for the same sites. Therefore, PM are classified into biogenic (carbonaceous: microbial and animal remains) from PU and WMO, incidental (industrial, mixt physico-chemical character) from PU, FU, WMO, B&S and P&S, and geogenic (crustal mineral dust) from RHT, B&S, PU, and P&S. Furthermore, increase in metal concentrations in PM10 (Cr, Mn, Co, Ni, V, As, Be, Ba, and Cd) and PM2.5 (As, Pb) while TC, OC, and SOC in PM2.5 caused depreciation overall lung function. The exposure to biogenic and incidental PM nature are key cause of pulmonic dysfunction.

The deep soil water dynamics and its environmental controls after long-term revegetation

The increase in the extreme drought trend, reduction in soil erosion, and acceleration of deep soil desiccation are renewing interests in soil water dynamics and its environmental controls after long-term (>30 years) grass and shrub revegetation on the Chinese Loess Plateau (CLP). However, inconsistent findings have been reported on soil water dynamics in these typical land uses due to the multi-dependent environmental controls. The objectives of this study are to identify the spatial variability of soil water dynamics and its controls in a small watershed. For this purpose, spatiotemporal soil water storage in 1 m interval to a depth of 5 m was decomposed into a temporal mean (i.e., time-stable pattern) and temporal anomaly (Atn), which varies over time and is related to soil water dynamics. Atn was then decomposed into a space-invariant temporal anomaly (i.e., spatial mean of Atn) and a space-variant temporal anomaly (Rtn), which reflects the spatial variability of soil water dynamics. The Rtn was further decomposed using the empirical orthogonal function (EOF) to identify its major controls. Results showed that soil water dynamics (gain and loss) decreased from grassland to abandoned cropland followed by shrubland after long-term revegetation. The hot spots in deep soil water dynamics (2–5 m) were identified in layered soils with an overlying sand layer and underlying silt layer, and grassland with the coexistence of tree-shrub-grass and high deep soil organic carbon (SOC) content. 50–70% of the total variations of Rtn were explained by the first two spatial patterns (EOFs). Silt and SOC content controlled EOF1 of Rtn at 0–2 and 2–5 m, respectively. Plant canopy and soil profile properties (e.g., layered soils with an overlying sand layer and underlying silt layer) controlled EOF2 of Rtn at 0–1 and 2–5 m, respectively. The EOF analysis suggests that silt and SOC dominated soil water storage capacity, plant canopy regulated water flux, and variations of hydraulic properties in soil profiles may jointly drive spatial variability of soil water dynamics.

Improved thermal conductivity parameterization of SHAW model in permafrost regions on the Qinghai-Tibet Plateau

Soil thermal conductivity is critical for determining the hydrological and energy transfer processes in permafrost regions and simulating hydrological and thermal dynamic processes with land surface models. In this study, improved thermal conductivity parameterizations of the Simultaneous Heat and Water model (SHAW) were assessed using observation data from permafrost regions on the Qinghai-Tibet Plateau (QTP). The results indicated that the SHAW could precisely describe soil hydrological and thermal processes at the Tanggula (TGL) site. In general, the performances of Johansen's, Luo's, and the ORCHIDEE-MICT model's soil organic matter (SOM) parameterizations were superior to the original De Vries's parameterization. The SOM parameterization performed the best. The root mean square error (RMSE) of the active layer's soil temperature was 0.42 °C lower than that of the original parameterization at the Xidatan (XDT) site and 0.2 °C lower at the TGL site. In particular, the RMSE of the soil temperature at 3 m depth at TGL was 0.8 °C lower than that of the original parameterization. The average Nash-Sutcliffe Efficiency (NSE) for simulating the active layer soil temperature using the SOM parameterization was 0.915 at TGL site and 0.806 at XDT site. While De Vries parameterization yielded average NSE values of 0.771 and 0.627 for soil temperature simulations at the two sites, respectively. The results indicate that the soil organic carbon cannot be ignored in the simulation of hydrological and thermal processes in permafrost areas with a high soil organic carbon content. Notably, the simulated soil temperatures during the freezing period and the soil liquid water content during the thawing period improved significantly after modifying the thermal conductivity parameterization of SHAW. Therefore, the revised SHAW more accurately reflects the water and heat transfer processes of permafrost and can be used to analyze land-atmosphere interactions.

Distribution and treatment needs of soil-transmitted helminthiasis in Bangladesh: A Bayesian geostatistical analysis of 2017-2020 national survey data.

In Bangladesh, preventive chemotherapy targeting soil-transmitted helminth (STH) infections in school-age children has been implemented since 2008. To evaluate the success of this strategy, surveys were conducted between 2017 and 2020 in 10 out of 64 districts. We estimate the geographic distribution of STH infections by species at high spatial resolution, identify risk factors, and estimate treatment needs at different population subgroups. Bayesian geostatistical models were fitted to prevalence data of each STH species. Climatic, environmental, and socioeconomic predictors were extracted from satellite images, open-access, model-based databases, and demographic household surveys, and used to predict the prevalence of infection over a gridded surface at 1 x 1 km spatial resolution across the country, via Bayesian kriging. These estimates were combined with gridded population data to estimate the number of required treatments for different risk groups. The population-adjusted prevalence of Ascaris lumbricoides, Trichuris trichiura, and hookworm across all ages is estimated at 9.9% (95% Bayesian credible interval: 8.0-13.0%), 4.3% (3.0-7.3%), and 0.6% (0.4-0.9%), respectively. There were 24 out of 64 districts with an estimated population-adjusted STH infection prevalence above 20%. The proportion of households with improved sanitation showed a statistically important, protective association for both, A. lumbricoides and T. trichiura prevalence. Precipitation in the driest month of the year was negatively associated with A. lumbricoides prevalence. High organic carbon concentration in the soil's fine earth fraction was related to a high hookworm prevalence. Furthermore, we estimated that 30.5 (27.2; 36.0) million dosages of anthelmintic treatments for school-age children were required per year in Bangladesh. For each of the STH species, the prevalence was reduced by at least 80% since treatment was scaled up more than a decade ago. The current number of deworming dosages could be reduced by up to 61% if the treatment strategy was adapted to the local prevalence.

Sugarcane mill mud-induced putative host (soybean (Glycine max))-rhizobia symbiosis in sandy loam soil.

Domestic production of controlled-release, compost-based, and microbe-enhanced fertilizers is being expanded in the U.S. as a part of rural development. Sugarcane mill mud is a sterilized (≈90°C) agricultural byproduct in surplus that has received interests as a soil amendment in several Southern states, because of its high phosphorus and organic carbon contents. Addition of mill mud to sandy loam significantly increased the nodule formation compared to fertilized and unfertilized controls. Mill mud addition also resulted in pod yields similar to the fertilized control. Though not found in mill mud itself, mill mud additions correlated with an increase in soil Rhizobia as determined by deep 16S rRNA gene sequencing. We hypothesize that Firmicutes in sterilized mill mud induced Rhizobia that in turn enhanced soybean (Glycine max) growth. Collectively, mill mud enhanced the plant growth promoting bacteria when applied to a silt loam, although the relative influence of mill mud-derived bacteria, organic carbon, and nutrients is yet to be determined.

Unexpected high alkyl carbon contents in organic matter-rich sandy agricultural soils of Northwest Central Europe

Carbon sequestration in Plaggic Anthrosols is most often investigated by bulk soil carbon inventories, without considering the form in which the carbon is stored (e.g., particulate or mineral-associated organic matter (OM), its capacity, or its chemical composition). Here, we focus on the unusual high organic carbon (OC) accumulation in sandy Plaggic Anthrosols and adjacent reference soils under agricultural use. In these soils, the mineral fraction ≤20 µm which is commonly assumed to be the major factor for OC stabilization, are very low in mass proportion. Soil organic matter (SOM) physical fractionation was done to evaluate the quantity and quality of OC in the topsoil (Ap horizon). For the fraction ≤20 µm (medium and fine silt-, and clay-sized particles), we measured the concentration of OC and calculated its OC storage capacity and contribution. The OC of the fraction ≤20 µm was radiocarbon-dated and analyzed for its chemical composition by solid-state 13C NMR spectroscopy. The highly sandy (∼90 % sand and coarse silt) soils showed an accumulation of OC much higher than the conventionally calculated saturation level controlled by the proportion of the fraction ≤20 µm. Unexpectedly, Plaggic Anthrosols and the respective reference soils showed similar fractional OC concentrations, radiocarbon ages, and OM composition. The isolated fraction ≤20 µm contained, on average, 81 % of the total soil OC in only 9 % of the corresponding soil mass. All soil fractions ≤20 µm are characterized by a high mean OC concentration in the topsoil (reference soils: 226 ± 66.5 mg OC g−1, Plaggic Anthrosols: 202 ± 59.0 mg OC g−1) with a C/N ratio of 15 on average for both soils. The OM composition of the fraction ≤20 µm was specifically rich in alkyl-C, with unusually low proportions of O-alkyl-C and low contents of aryl-C. The radiocarbon concentration (F14C) indicated that topsoil OM of the ≤20 µm fraction is stored for long time periods with high mean conventional radiocarbon ages (14C) not only for Plaggic Anthrosols (F14C: 0.92 ± 0.04; 14C: 639 yBP) but also for the reference soils (F14C: 0.93 ± 0.04; 14C: 575 yBP) and received low inputs of OC derived from recent photosynthesis. Our data indicate the existence of specific SOM accumulation processes in the investigated sandy agricultural soils, resulting particularly large SOM stocks which cannot be explained by mechanistic association of OM with mineral surfaces. It is not clear, if this inherited OM is stable under present-day soil and management conditions.

Effects of microtopography on within-field spatial variation of inherent soil properties in Andosols of Tokachi district, Hokkaido

ABSTRACT In large-scale upland cropping systems, understanding the magnitude of soil property variations and mapping the distribution are essential to improve soil nutrient management. The Tokachi district of Hokkaido has large-scale upland fields, and the soils are dominated by Andosols that inherently have characteristic clay minerals and high soil organic carbon content. In the region, microtopography is known to exist that can affect soil formation and within-field variation of the inherent soil properties. However, limited information exists about the relationship between microtopography and the spatial variation of inherent soil properties that are important for nutrient dynamics. Therefore, this study aimed to assess the effect of microtopography on the within-field variation of inherent soil properties in Andosols of Tokachi district, Hokkaido. Within a 6.6-ha field with an elevation difference of 3.2 m, four soil profiles were surveyed at different topographical positions, and 530 surface soil samples were collected at 12-m intervals. Samples were analyzed for total carbon (TC), acid-oxalate extractable Al, Fe, and Si (Alo, Feo, and Sio), pyrophosphate extractable Al and Fe (Alp and Fep), cation exchange capacity (CEC), and phosphate absorption coefficient (PAC). Geostatistical analysis was applied to understand the spatial structure of the surface soil properties. All soil profiles were dominated by volcanic parent materials, and they were classified into different types of Andosols. An exceptional variation of inherent soil properties was found in the surface soil, with TC content ranging from 35.2 to 124 g kg−1 and CEC from 20.3 to 55.7 cmolc kg−1. Geostatistical analysis showed that TC content varied over a large distance (range: 226 m) while allophane content varied at a shorter distance (range: 118 m). Our findings revealed that microtopography affected the soil water dynamics and erosion of the surface soil particles which caused the variation of TC, CEC, and allophane. Further studies must be conducted to understand the effects of the variation of these inherent soil properties on soil nutrient availability and crop productivity.

Effects of Lotus (Nelumbo nucifera Gaertn.) on the Methane Emission in Littoral Zones of a Subtropical Lake, China

Freshwater lakes represent a potential source of methane (CH4) emission into the atmosphere. However, the CH4 emission contribution to the total emission in the littoral zones of lakes, especially emergent macrophytes (e.g., lotus), is poorly known. Lotus has been cultivated in almost all provinces in China; it is not only an aquatic plant, but also a kind of vegetable. In this study, two sampling zones (lotus plant and open water) were established in the lake of the middle reaches of the Yangtze River. The CH4 emission was measured using a floating opaque chamber and gas chromatography between April and December in the years 2021 and 2022. The results indicated that the flux of CH4 emissions ranged from 0.10 to 59.75 mg m−2 h−1, with an average value of 5.61 mg m−2 h−1, in the open water, while ranging from 0.19 to 57.32 mg m−2 h−1, with an average value of 17.14 mg m−2 h−1, in the lotus plant zone. The maximal CH4 emissions occurred in July and August for the open water, which was highly related to the air and water temperature, whereas it happened in September for the lotus plant zone, possibly due to the high vegetation biomass, indirectly enhancing the high soil organic carbon content, plant-mediated CH4 emission, as well as the lower dissolved oxygen concentration, thus strengthening the production and emissions of CH4. Considering the carbon emissions (both CH4 and CO2) and plant productivity, although greater CH4 emission occurred in the lotus plant zone, it could still represent a potential carbon sink (213 g m−2 yr−1) compared to the open water.

Impact of Thermal Maturation of the Upper Cretaceous Bituminous Limestone of Attarat Um Ghudran Central Jordan on Calcareous Nannofossil Preservation.

Oil shale deposits of the Late Cretaceous from three boreholes in central Jordan were examined to assess the impact of thermal maturation on the content of nannofossils. Thermal activity has been shown to have a strong effect on organic matter content and composition but its effect on calcareous nannofossil assemblages remains inconclusive. This study aims to determine the impact of thermal maturation on nannofossil assemblages and to compare this to an estimated maturity level based on bulk geochemical analysis. Micropaleontological and geochemical analyses were conducted on 31 samples from three oil shale wells drilled in Attarat Um Ghudran central Jordan. Several types of nannofossil preservation have been recorded, including dissolution, overgrowth, and breakage. In the Jordan oil shale sections, nannofossils exhibit a variety of preservation types, with intense dissolution in the middle part of the study sections. The vast majority of the samples had high TOC enrichment, with 29 samples exceeding values of >10%. Kerogen recovery and quality from the oil shale are very good, with a predominance of fluorescent amorphous organic matter (AOM) and minor algal components. The low fluorescence preservation index (FPI), which is 1 in most of the samples, indicates that alteration occurred due to intense thermal activities in the study interval. The palynomorph and AOM fluorescence, ranging from a spore coloration index (SCI) of 3 to 5, suggest that the studied samples were approaching the oil window. A correlation between the nannofossil preservation and geochemical parameters shows a predominance of poorly preserved nannofossils along with high total organic carbon contents and an elevated hydrogen index (HI). We show that low FPI values and a higher level of maturity are associated with poor nannofossil preservation, suggesting that nannofossils, in conjunction with petrographic analysis of kerogen, could be used as a rapid screening technique for estimating levels of oil-shale maturity. The nature of the tectonism in the study area, including faulting and a metamorphosed zone, enhanced the maturity, which might explain why the nannofossils were so significantly affected.

No detectable upper limit when predicting soil mineral-associated organic carbon stabilization capacity in temperate grassland of Central Argentina mountains

Soil organic carbon (SOC) is the major active organic carbon (OC) reservoir within terrestrial ecosystems. SOC is stored in different soil organic matter fractions, among which mineral-associated organic matter is considered the more stable. It has been proposed that the OC stored in this fraction (i.e., MAOC-mineral associated organic carbon) depends on the proportion of fine soil particles. This idea has been challenged by studies that found soils with significantly higher MAOC values than predicted by several models. We assessed the soil MAOC contents in central Argentina mountain grasslands. These soils store high OC contents, and thus may constitute a valuable case to evaluate the soils' saturation behavior. We compared the actual soil MAOC content of these mountain grasslands with the predictions from different MAOC saturation models, and we explored if there were indications of saturation behavior by: a) plotting the MAOC against the total SOC contents, and b) by plotting the OC contents in the fine fraction against the fine soil particles content. We found a positive relationship between MAOC and the fine particle content in the soils studied. However, we also found that even the model with the highest upper limit of MAOC stabilization underestimated the MAOC contents of these grasslands. In addition, we found the absence of an inflection point when plotting the MAOC against total SOC contents. Finally, we observed a weak but significant negative relationship between the concentration of OC in the fine fraction and the proportion of the fine fraction of the soil, with high OC loading values in the coarser soils. These last patterns could be indicators of non-saturation behavior. Our results provide additional evidence that many of the models currently used for predicting the OC saturation deficit of soils may be underestimating the potential MAOC stabilization capacity of certain soils. Additionally, our findings contribute to the evidence challenging the ideas of OC saturation on a fine soil particles basis. We highlight some lines of research that should be developed to confirm the existence of a MAOC saturation behavior, as well as to continue exploring the drivers of OC accrual in different systems.

Environmental controls on organic matter enrichment of the lower Cambrian source rocks in the Tarim Basin, Northwest China

In the Tarim Basin, the largest petroliferous basin in China, a set of organic-rich deposition hosted in the lower Cambrian Yuertusi Formation is considered to be the main hydrocarbon source rocks. However, the limited and scattered distribution of the lower Cambrian constrains present studies mostly on some certain sections where samples are accessible, inhibiting a systematic understanding of characteristics of these source rocks and controls on organic matter enrichment. Here, we conduct a systematic study on a drillcore in northwestern margin of the Tarim Basin (Taxibei), integrated with previously published data from other available sections. These data show the Yuertusi Formation was mainly composed of mudstone/shale, carbonate and siliceous rocks, and distributed dominantly in the Taxibei, northern (Tabei) and eastern-northeastern areas of the Tarim Basin (Tadong-Tadongbei) with an increased thickness (mean 30 m to mean 60 m) towards the Tadong-Tadongbei areas. High total organic carbon (TOC) contents (up to 30%) were found in the mudstone/shale dominated intervals in both the Taxibei and Tabei areas, characterized by I-II kerogen and highly to over-matured thermal maturity. Paleo-redox reconstruction based on high V/(V + Ni) ratios (>0.6) and FeHR/FeT ratios (>0.38) suggests anoxic watermass conditions occurred during the deposition of the organic-rich intervals along with moderate sedimentation rate, providing consistently good preservation for organic matter accumulation. Based on a combined analysis, we infer primary productivity in surface waters exerted a key control on TOC contents of the organic-rich intervals, which was driven by nutrient supplies from hydrothermal activities with partial upwelling effects in the Taxibei area, and from upwelling waters in the Tabei area.

How geoecological components of a terroir can be altered by spatial changes of vineyards – A case study from Eger Wine District (Hungary)

Terroir is a concept referring interactions of natural (topography, lithology, climate, soil etc.) and human (economic conditions, traditions, cultivation practices, etc.) factors; therefore, terroir is spatially delimited and subjected to environmental, socio-economic, and temporal changes. The geoecological background of wine districts are considered more stable among them, but, because of its natural diversity and the spatial changes of production sites, changes in abiotic terroir components might occur too. In this study the spatial changes of grape production sites in Eger Wine District (Hungary) across two and a half centuries (1784 to 2018), and their consequences on the composition of the geoecological factors (lithology, topography, soil characteristics) were analyzed. Modernization of cultivation, urbanization and increase of built-up areas around the central settlement resulted in decreased concentration, i.e. increased spatial dispersion to more remote vineyards further from Eger. It also has consequences on the lithological and topographical composition of the production sites. Besides the slightly increasing extent of vineyards (from 5346 ha to 7413 ha) we found a distinct decrease of vineyards at higher elevations and a substantial increase at lower elevations. Distribution according to slope gradient changed also remarkably, with the share of vineyards on &lt;5 % slopes from 38 % to 65 %. These changes resulted in transformations of pedological characteristics according to the comparison of vineyard’s extent with soil map data: vineyards shifted to slightly acidic, more fertile (i.e. deeper soil layer with higher organic carbon content) soils. The share of vineyards with different lithology and parent material also changed: loose, calcareous Tertiary sediments decreased almost to half, and the share of vineyards over acidic volcanics and their weathered regoliths almost doubled. Comparing these two dominant lithological types and soil profiles derived from them, different pedological characters and taxonomic status were found (Phaeozems and Vertisols). However, comparison of these two lithological types based on main topsoil characteristics (pH, SOC, carbonates, depth of fertile soil layer, N, P, K content) according to 25 randomly chosen surficial soil samples at production sites, showed no significant differences.. In the case of this particular wine district, spatial changes of the production sites affected mostly the distribution by elevation, by slope gradient, but did not alter significantly the surface soil character of the terroir.

Comparative Study of Individual and Combined Application of Humic Acid, Wood Vinegar, and Biochar on Soil Zn Chemical Fractions and Its Uptake by Sour Orange (Citrus aurantium L.) Seedlings

ABSTRACT The addition of organic materials in arid and semi-arid regions not only improves the physicochemical and biological characteristics of the soil but also increases plant growth. In this study, the effect of individual and combined application of humic acid (HA) (150 mg kg−1 soil), wood vinegar (WV) (75-fold dilution), and biochars (corn straw biochar (CSB) and cotton residue biochar (CRB) each at 2% wt.) on the soil Zn chemical fractions and its uptake by Sour Orange (Citrus aurantium L.) seedlings were investigated in a calcareous soil. The results showed the CRB was more effective in increasing the Zn concentration in fractions with high bioavailability (soluble+exchangeable (WsEx) and organic (OM) forms) than the CSB. This may be due to its higher organic carbon content (74%) and electrical conductivity (3.52 dS m−1) than those for the CSB. There was no significant difference between HA and WV in terms of the effect on soil Zn chemical fractions. The CRB+WV and CRB+HA were the best treatments for enhancing the soil Zn bioavailability. The greatest increase in the shoot dry matter yield (2.5-fold) and Zn uptake (29%) was associated with the combined treatment of CRB+HA compared to the control. Furthermore, the shoot dry matter yield of Sour Orange seedlings had a significant and positive correlation with the Zn-WsEx fraction and Zn uptake. It could be concluded that among the treatments, the combined application of CRB+HA was the best in enhancing soil Zn bioavailability, Zn uptake and shoot dry matter yield of Sour Orange seedlings in the calcareous soil.