Carbon Profiles Research Articles

Soil metagenomics reveals reduced tillage improves soil functional profiles of carbon, nitrogen, and phosphorus cycling in bulk and rhizosphere soils

Conservation tillage practices (CAT) are known to benefit soil health and soil ecosystem functions relative to conventional tillage (CVT); however, much uncertainty remains concerning microbial functional traits and their subsequent effects on soil nutrients under different tillage practices. We analyzed the functional profiles of the C, N, and P cycles in response to CAT of no-tillage (NT), reduced tillage (RT), and CVT of moldboard plowing (MP) in bulk and rhizosphere soils using shotgun sequencing. CAT induced distinct microbial functional patterns relative to CVT, and these differences were generally more evident in rhizosphere soils than in bulk soils. CAT promotes multiple metabolic pathways such as C and N decomposition, fermentation, CO oxidation, N fixation, nitrate reduction and inorganic-P and organic-P transformations in bulk and/or rhizosphere soils. Variations in these metabolic pathways were mainly driven by Bradyrhizobium, Mesorhizobium, Nitrososphaera, Phenylobacterium, Rhizobium which are affiliated with Proteobacteria, Actinobacteria, Acidobacteria, Bacteroidota and Thaumarchaeota. Furthermore, 24 high-quality metagenome-assembled genomes (MAGs) were reconstructed, of which three novel MAGs (TL100, TL46, and TL57) harbored functional genes regulating all metabolic pathways. In particular, NT-enriched MAGs (such as Sphingomonas) promote fermentation, resulting in the reduction of soil total carbon (TC) relative to MP in bulk soils. RT retained the contents of soil TC and total nitrogen (TN) well and up-regulated the phoR gene carried by Streptomyces, which promoted the regulation of P-starvation concomitantly with the increase in the contents of total phosphorous (TP) and available phosphorous (AP) in bulk soil. Additionally, assimilatory nitrate reduction coupled with organic-P mineralization was facilitated by CAT in rhizosphere soil, leading to the mitigation of N loss and the activation of soil organic-P for crop uptake. Overall, our results revealed that CAT significantly accelerated multiple metabolic potentials, and RT could sustain soil nutrient contents better than NT.

Hybrid synthetic/natural fiber-reinforced strain-hardening magnesia-based composites

Synthetic fiber-reinforced strain-hardening magnesia (MgO)-based composites (SHMC) are an emerging group of fiber-reinforced cementitious composites (FRCC) with ultra-high ductility and CO2 sequestration potential. However, the size of SHMC members is limited by the inadequate carbonation depth of the MgO matrix. In this work, hybrid synthetic/natural fiber-reinforced SHMC are developed containing different contents of PVA fibers (0-2 vol.%) and sisal fibers (0-4 vol.%). The new Hybrid-SHMC were experimentally studied on micro-scale and composite scale. On the micro-scale, the effect of cement matrix carbonation on the PVA/sisal fiber-to-matrix interfacial bonds and the matrix moduli were studied by single-fiber pullout test and local nano-indentation. On the composite scale, the effect of fiber dosage on the compressive/tensile behavior and carbonation profile of SHMC were studied. The effects of the carbonation-induced micromechanical enhancements on the composite behaviors were validated by a micromechanics-based fiber-bridging model. The results demonstrated that the new hybrid SHMC could achieve ultra-high tensile ductility (>2.5%) and uniform carbonation simultaneously (≥ 0.25g CO2/g MgO at different depths). In Hybrid-SHMC, the PVA fibers mainly contributed to the mechanical crack-bridging and thus strain-hardening, while sisal fibers with porous microstructure improved the carbonation depth and thus the fiber-matrix interfacial bonds, composite compressive, and tensile performances.

Lifting the Profile of Deep Forest Soil Carbon

Forests are the reservoir for a vast amount of terrestrial soil organic carbon (SOC) globally. With increasing soil depth, the age of SOC reportedly increases, implying resistance to change. However, we know little about the processes that underpin deep SOC persistence and what deep SOC is vulnerable to climate change. This review summarizes the current knowledge of deep forest SOC, the processes regulating its cycling, and the impacts of climate change on the fate of deep forest SOC. Our understanding of the processes that influence deep SOC cycling and the extent of SOC stores is limited by available data. Accordingly, there is a large degree of uncertainty surrounding how much deep SOC there is, our understanding of the influencing factors of deep SOC cycling, and how these may be distinct from upper soil layers. To improve our ability to predict deep SOC change, we need to more accurately quantify the deep SOC pool and deepen our knowledge of how factors related to the tree root–soil–microbiome control deep SOC storage and cycling. Thereby, addressing the uncertainty of deep SOC contribution in the global C exchange with climate change and concomitant impacts on forest ecosystem function and resilience.

Multiple controls on the preservation of organic matter in the lower Mississippian Luzhai Formation black shale in southern China

The early Carboniferous experienced profound climate cooling that drove the Earth's climate from a mid-Paleozoic greenhouse into the Late Paleozoic Ice Age. Several climate cooling events have been reported, including the Tournaisian and Visean (early to mid-Early Carboniferous). In this study, we perform multi-proxy analyses (organic carbon isotopes, nitrogen isotopes, major and trace elements and organic petrology/geochemistry) of samples from an early Carboniferous section in Nandan region (Guangxi, China). Our goal is to investigate the global carbon‑nitrogen cycle, and associated oceanic productivity and redox perturbations, during a key climatic transition interval, as well as the controls on organic matter enrichment in the sediments. The carbon and nitrogen isotope profiles of the Nandan section record major perturbations during the mid-Tournaisian and early Visean. The mid-Tournaisian carbon isotope excursion (TICE) is marked by a positive δ13Corg shift of 1.8 ‰ (from −27.7 ‰ to −25.9 ‰), correlating with a positive δ15N shift. The early Visean carbon isotope excursion (VICE) is characterized by a positive shift in δ13Corg (from −28.2 to −25.5 ‰, with an excursion magnitude of 2.7 ‰), but associated with a negative shift in δ15N (from +5 ‰ to +4 ‰). The positive δ13Corg excursions during these events most likely reflect enhanced organic matter burial with expansion of anoxic seafloor in the global ocean. The drop in nitrogen isotope values in the early Visean is interpreted to be linked with less denitrification under more oxic conditions. The decrease of organic matter contents up section is consistent with the shift to more oxic conditions and increased sedimentary dilution caused by sea-level fall, which is ultimately controlled by orogenic events and climate cooling.

451 Establishing producer research sites for the development of beef and bison climate-smart agriculture

Abstract Greenhouse gas (GHG) emissions and livestock production are topics that are increasingly intertwined. While livestock production is frequently presented as harmful to the environment, this perception fails to consider the carbon sequestration that takes place in livestock grazing systems and the role that grazing ruminants have in maintaining healthy grassland ecosystems. Grazing lands, which are often unsuited to row crop agriculture, are estimated to account for 25% of the global soil sequestration potential for soil carbon storage. Grazing livestock producers are often overlooked in the GHG reduction conversation, despite over 70% of beef GHG emissions being attributed to the cow-calf sector, which is primarily grazing. Furthermore, there is a relative lack of data surrounding the implementation of climate-smart agriculture practices on grazing operations and a lack of cost-effective methods to measure carbon/GHG sinks and sources on these landscapes. The potential climate benefits are considerable, with nearly 940 million acres of rangelands in the U.S. supporting forage-based livestock production. South Dakota State University recently received funding to support a large-scale climate-smart project focused on grazing beef and bison. For this project, we are utilizing the Cottonwood Field Station that has over 80 yr of historical grazing data, along with six grazing beef and bison ranching operations in the Northern Great Plains. The work on these ranches will focus on measuring and monitoring the impacts of climate-smart NRCS land practices, including cover crops, improved pasture and range seedings, prescribed grazing, and prescribed burning. A significant focus will be extensive, annual soil sampling across these operations to continuously monitor changes in soil organic carbon, bulk density, texture, pH, and soil microbiome community profiles. Each operation will have GreenFeed methane pasture units deployed for 5 yr to monitor changes in beef cattle and bison methane emissions in response to climate-smart practice adoption. We are also assessing biodiversity pre and post climate-smart practice adoption, as biodiversity improvements may be one of the most overlooked and yet most important responses to climate-smart land practice implementation. Over the duration of this project, a large-scale, comprehensive data collection will be achieved and used to refine GHG and carbon sequestration estimates associated with range livestock systems. Data resulting from this project will be used to inform research protocols and prediction models, fill knowledge gaps, and shape science-based discussions and marketing strategies for climate-smart agricultural commodities.

Assessment of acute, subacute genetic toxicities and immunomodulatory activity of palm (Trachycarpus fortunei) buds

Ethnopharmacology relevancePalm buds are a natural green resource of the forest, which are not only rich in nutrients but contain a large number of phenolic acids and flavonoids, among other components. It has a variety of biological activities such as antioxidant and uterine smooth muscle stimulation.Aim of the study: To evaluate the safety of palm buds for use as a nutraceutical product and food by evaluating the toxicity, subacute toxicity and genotoxicity of the young palm buds. Also studied for its immune-enhancing activity. Materials and methodsAcute toxicity tests were performed in mice using the maximum tolerance method, and the manifestations of toxicity and deaths were recorded after administration of 10,000 mg/mL for 14 consecutive d (days) of observations. To assess subacute toxicity, mice were treated with palm buds (750, 1500, or 3000 mg/mL) daily for 28 days. The teratogenicity of palm buds was assessed by the Ames test, the mouse bone marrow cell micronucleus test, and the mouse spermatozoa malformation test. In addition, we evaluated the immune-enhancing ability of palm buds by the mouse carbon profile test, delayed-type metamorphosis reaction, and serum hemolysin assay. ResultsIn the acute toxicity study, the Median Lethal Dose (LD50) was greater than 10,000 mg/kg bw in both male and female rats. There were also no deaths or serious toxicities in the subacute study. The no-observed-adverse-effect level (NOAEL) was 3000 mg/kg bw. However, the mice's food intake decreased after one week. The medium and high dose groups had a reducing effect on body weight in mice of both sexes. In addition, the changes in organ coefficients of the liver, kidney and stomach in male mice were significantly higher in the high-dose group (3.23 ± 0.35, 0.75 ± 0.05, 0.57 ± 0.05 g) than in the control group (2.94 ± 0.18, 0.58 ± 0.05, 0.50 ± 0.02 g). Hematological analyses showed that all the indices of the rats in each palm sprout dose group were within the normal range. The results of blood biochemical indicators showed that there was a significant reduction in TP in the blood of male mice in the high-dose group (44.6 ± 7.8 g/L) compared to the control group (58.3 ± 15.1 g/L). In histopathological analysis, none of the significant histopathological changes were observed. The results of the immunological experiment in mice showed that the liver coefficient and thymus coefficient of the high-dose group (8400 mg/kg) were significantly lower than the control group. There was no remarkable difference in auricle swelling between each dose palm bud group (1400, 2800, or 8400 mg/kg) and the control group. The anti-volume number of the high-dose group was significantly increased. ConclusionPalm buds have non-toxic effects in vivo and have little effect on non-specific and cellular immunity in the test mice within the dose range of this experiment. The immunoenhancement in mice is mainly achieved through humoral immunity. In conclusion, our results suggest that palm buds are safe for use as healthcare products and food.

The hidden acceleration pump uncovers the role of shellfish in oceanic carbon sequestration

Whether shellfish mariculture should be included in the blue carbon profile as a strategy to combat climate change has been controversial. It is highly demanding not only to provide calibration quantitation, but also to provide an ecosystem-based mechanism. In this study, we chose mussel farms as a case study to evaluate their contributions to carbon sinks and their responses to sedimentary carbon fixation and sequestration. First, we quantified the air–sea CO2 flux in the mussel aquacultural zone and observed a weak carbon sink (−0.15 ± 0.07 mmol·m−2·d−1) during spring. Next, by analyzing the carbon composition in the sediment, we recorded a noticeable and unexpected increase in the sedimentary recalcitrant carbon (RC) content in the mussel farming case. To address this surprising sedimentary phenomenon, a long-term indoor experimental test was conducted to distinguish the consequences of mussel engagement with sedimentary RC. Our observational data support the idea that mussel engagement promotes accumulation of RC in sediments by 2.5-fold. Furthermore, the relative intensity of carboxylic-rich alicyclic molecule (CRAM)-like compounds (recalcitrant dissolved organic matter (RDOM)) increased by 451.4 % in the mussel-engaged sedimentary dissolved organic matter (DOM) in comparison to the initial state. Mussel engagement had a significantly positive effect on the abundance of sedimentary carbon-fixing genes. Therefore, we definitively conclude that mussel farming is blue carbon positive and propose a new alternative theory that mussel farming areas may have high carbon sequestration potential via an ecologically integrated “3 M” (microalgae–mussel–microbiota) consortium. The “mussel pump” accelerates carbon sequestration and enhances climate-related ecosystem services.

Enhanced crop yields as a potential mitigator of soil organic carbon losses under elevated temperature in erosional and depositional landscape

The dynamics of agricultural soil organic carbon storage have been considerably influenced by the evolution of crop species, offering promising opportunities for restoring soil organic carbon under elevated temperatures through yield improvements. However, the intricate interplay between climate change and surface erosion processes poses challenges in understanding agricultural soil carbon dynamics in hilly landscapes. This study aimed to address these challenges by assessing the effects of climate change on soil organic carbon dynamics under the Shared Socioeconomic Pathways 245 and 585. We utilized projections from 12 distinct global climate models, covering the period from 2015 to 2100. Additionally, we investigated the potential for improving soybean yields by 100 %, 200 %, and 300 % linearly by 2100 to offset the anticipated soil organic carbon losses. Using a coupled landscape and biogeochemical model, our analysis focused on a soybean field in Nenjiang County, China. Our findings revealed a distinct soil organic carbon profile in deposition areas, characterized by relatively low levels of soil organic carbon in surface layers, attributed to carbon influx from adjacent erosion areas with typically low carbon content. We modeled decreases in soil CO2 fluxes with escalating climate change, corresponding to expected decreases in soil organic carbon levels, despite concurrent rises in soil microbial activity linked to increasing temperatures. Erosion areas emerged as particularly vulnerable zones under elevated temperatures due to their higher proportion of soil CO2 fluxes relative to soil organic carbon levels compared to deposition areas. As a soil organic carbon restoration strategy, improvements in soybean yields showed promise in mitigating soil organic carbon losses through enhanced litter inputs and the cooling effects induced by shading the soil. This study underscored the potential for achieving the dual benefits of food security and soil organic carbon restoration in the coming decades through a unified approach to enhancing soybean yields.

Validation of the ERO2.0 code using W7-X and JET experiments and predictions for ITER operation

The paper provides an overview of recent modelling of global material erosion and deposition in the fusion devices Wendelstein 7-X (W7-X), JET and ITER using the Monte-Carlo code ERO2.0. For validating the modelling tool in a three-dimensional environment, W7-X simulations are performed to describe carbon erosion from the graphite test divertor units, which were equipped in operational phase OP 1.2 and analysed post-mortem. Synthetic spectroscopy of carbon line emission is compared with experimental results from the divertor spectrometer measurement system, showing a good agreement in the e-folding lengths in the radial intensity profiles of carbon. In the case of metallic wall materials, earlier modelling of the Be/W environment in JET and ITER is revisited and extended with an updated set of sputtering and reflection data, as well as including the mixing model for describing the Be/W dynamics in the divertor. Motivated by recent H/D/T isotope experiments in JET, limited and diverted configuration pulses are modelled, showing the expected trend of both Be and W erosion increasing with isotope mass. For the JET diverted configuration pulses, it is shown that Be migrates predominantly to the upper part of the inner divertor where it initially leads to strong W erosion. With longer exposure time, the growth of a Be deposited layer leads to a reduction of W erosion in that region. A similar trend is observed in simulations of the ITER baseline Q = 10 scenario, however with a more symmetric Be migration pattern leading to deposition also on the outer divertor.

The phase changes of the mortars containing waste glass powder during carbonation

The utilization of glass powder (GP) with high pozzolanic activity to replace cement is a promising option for reusing waste glass. In such systems, Carbonation is a key factor that affects the durability. However, carbonation mechanisms remain poorly understood. In this study, the phase evolution of the GP - cement composites exposed to CO2 was determined by accelerated carbonation tests of samples with different cement-to-GP substitution rates (0, 15, 30, and 50 wt%). The carbonation depth was determined using phenolphthalein spray tests. Furthermore, the chemical information regarding the carbonation profiles was obtained by the X-ray diffraction (XRD), thermogravimetric analysis (TG), and Fourier transform infrared spectroscopy (FT-IR). It was found that an increase in the GP content increased the carbonation depth of the samples because of the low calcium hydroxide (CH) content. The increase rate was more similar to those of fly ash (FA) and silica fume (SF) rather than that of Ca-rich granulated blast-furnace slag (GBS). Moreover, XRD and TG tests revealed that compared to the plain cement, GP addition influenced crystalline forms of CaCO3, as well as the quantity of produced CaCO3. Combined with the FT-IR test results, when the replacement level of the GP up to ≥30 wt%, the produced CaCO3 and the depolymerised C-S-H by the carbonation significantly differed from the pure Portland cement. This study offers insights into the carbonation mechanisms of GP – cement mortars to promote glass recycling.

Himalayas is barrier for transportation of light-absorbing particles from South Asia to inner Third Pole

Through a comprehensive investigation into the historical profiles of black carbon derived from ice cores, the spatial distributions of light-absorbing impurities in snowpit samples, and carbon isotopic compositions of black carbon in snowpit samples of the Third Pole, we have identified that due to barriers of the Himalayas and remove of wet deposition, local sources rather than those from seriously the polluted South Asia are main contributors of light-absorbing impurities in the inner part of the Third Pole. Therefore, reducing emissions from residents of the Third Pole themselves is a more effective way of protecting the glaciers of the inner Third Pole in terms of reducing concentrations of light-absorbing particles in the atmosphere and on glaciers.

High-resolution carbon and oxygen isotopic compositions of cultured brachiopods: Effect of pH, temperature and growth

Brachiopod shells are ubiquitous since the Early Cambrian up to now. As they secrete a shell made of low-magnesium calcite, more resistant to diagenesis than biocarbonates richer in Mg, their geochemical signatures are generally considered a powerful tool for paleo-environmental and paleo-climatic reconstructions. However, gaps in knowledge still remain on the underlying controls of the shell chemistry, in particular at a high spatial resolution. In this study, in situ oxygen and carbon isotope measurements by SIMS (Secondary Ion Mass Spectrometry) were performed in brachiopod shells of the cold-temperate water species Magellania venosa, constituted of a primary and a secondary layer. The individual specimens studied here grew under controlled conditions mimicking the natural environment and in experiments under low-pH (high pCO2) and high-temperature conditions. Transversal carbon and oxygen profiles showed a “brachiopod pattern” typical of extant two-layered brachiopods, with the primary layer depleted in 18O and 13C relative to equilibrium and the secondary layer showing a gradual increasing trend until reaching a near-equilibrium plateau. Overall, shells cultured at low pH were found to have δ18O and δ13C values closer to equilibrium when compared to shells from the control experiment. These near-equilibrium values may reflect a decrease in shell precipitation rate, leading to less kinetic effects, and/or a more rapid kinetics for the equilibration between DIC species and water. By close pairing of seawater δ18O and δ13C to that of shell microstructure, our study enables us to derive layer-specific C and O enrichment factors, which show the extent of pH and temperature effects superimposed on the seawater δ18O and DIC δ13C signal inherited. Finally, we show that during brachiopod shell growth, newly precipitated calcite is added to the calcite already existing, thus empirically validating the conceptual accretionary growth model proposed by Ackerly (1989).

Characterization of PM0.1 mass concentrations and elemental and organic carbon in upper Southeast Asia

Addressing the air pollution problem in upper Southeast Asia (USEA) becomes critical due to its serious impacts on human health and the environment. This study aims to investigate the characteristics of ultrafine carbonaceous particles (PM0.1; Dp <≤ 0.1 μm) in Chiang Mai, Thailand, and Tachileik, Myanmar. Carbon compositions, including elemental carbon (EC) and organic carbon (OC) in PM0.1, were determined by a carbon analyzer. The range of particle mass ranged from 3.2 to 18.4 μg/m3 with an average of 8.3 ± 4.4 μg/m3 and 5.4–20.8 μg/m3 with an average of 10.2 ± 4.3 μg/m3 in Thailand and Myanmar, respectively. The ratio of the EC, Char-EC/Soot-EC ratio, was found to be more applicable than the OC/EC ratio for identifying the sources of the emission. The char-EC/Soot-EC ratios in the PM0.1 were less than 1.0 in the rainy season. Vehicle exhaust had a significant impact on these samples. However, the higher Char-EC/Soot-EC ratios indicate that biomass burning was a major source. The correlation for PM0.1 with all carbon profiles was strong, especially during the dry season, suggesting that they were produced from the same emission source. The OC/EC vs. EC correlation for PM0.1 at the Chiang Mai and Tachileik sites appears to be affected by open biomass fires. Our findings suggest that biomass combustion is a probable source of PM0.1 in Thailand and Myanmar. Therefore, it is crucial to prioritize the management of open burning and traffic to mitigate PM0.1 pollution in this region.

The microbiota characterizing huge carbonatic moonmilk structures and its correlation with preserved organic matter

BackgroundMoonmilk represents complex secondary structures and model systems to investigate the interaction between microorganisms and carbonatic rocks. Grotta Nera is characterized by numerous moonmilk speleothems of exceptional size hanging from the ceiling, reaching over two meters in length. In this work we combined microbiological analyses with analytical pyrolysis and carbon stable isotope data to determine the molecular composition of these complex moonmilk structures as well as the composition of the associated microbiota.ResultsThree moonmilk structures were dissected into the apical, lateral, and core parts, which shared similar values of microbial abundance, richness, and carbon isotopes but different water content, microbiota composition, and organic matter. Moonmilk parts/niches showed higher values of microbial biomass and biodiversity compared to the bedrock (not showing moonmilk development signs) and the waters (collected below dripping moonmilk), indicating the presence of more complex microbial communities linked to carbonate rock interactions and biomineralization processes. Although each moonmilk niche was characterized by a specific microbiota as well as a distinct organic carbon profile, statistical analyses clustered the samples in two main groups, one including the moonmilk lateral part and the bedrock and the other including the core and apical parts of the speleothem. The organic matter profile of both these groups showed two well-differentiated organic carbon groups, one from cave microbial activity and the other from the leaching of vascular plant litter above the cave. Correlation between organic matter composition and microbial taxa in the different moonmilk niches were found, linking the presence of condensed organic compounds in the apical part with the orders Nitrospirales and Nitrosopumilales, while different taxa were correlated with aromatic, lignin, and polysaccharides in the moonmilk core. These findings are in line with the metabolic potential of these microbial taxa suggesting how the molecular composition of the preserved organic matter drives the microbiota colonizing the different moonmilk niches. Furthermore, distinct bacterial and archaeal taxa known to be involved in the metabolism of inorganic nitrogen and C1 gases (CO2 and CH4) (Nitrospira, Nitrosopumilaceae, Nitrosomonadaceae, Nitrosococcaceae, and novel taxa of Methylomirabilota and Methanomassiliicoccales) were enriched in the core and apical parts of the moonmilk, probably in association with their contribution to biogeochemical cycles in Grotta Nera ecosystem and moonmilk development.ConclusionsThe moonmilk deposits can be divided into diverse niches following oxygen and water gradients, which are characterized by specific microbial taxa and organic matter composition originating from microbial activities or deriving from soil and vegetation above the cave. The metabolic capacities allowing the biodegradation of complex polymers from the vegetation above the cave and the use of inorganic nitrogen and atmospheric gases might have fueled the development of complex microbial communities that, by interacting with the carbonatic rock, led to the formation of these massive moonmilk speleothems in Grotta Nera.

Litterfall-Associated Carbon Deposition and Vertical Profiles of Soil Organic Carbon in Different Land-Use Systems

Litterfall is one of the major inputs for soil nutrients. Understanding the connection of litterfall and soil organic carbon (SOC) as the part of ecological processes is a key step towards carbon sequestration as a climate change mitigation strategy. Yet, it remains inadequate to support by empirical pieces of evidence particularly in tropical ecosystems. In this study, litter traps were used to monitor the monthly organic carbon deposition over a year through litterfall, and soil samples were collected vertically up to 30 cm depth to define the SOC depth distribution in three different land use types located at Wondo Genet district, southern Ethiopia. The results were interpreted by deploying both the carbon stratification ratio (CSR) and carbon flow balance ratio (CFBR) as ecological indicators. The results revealed that both the annual litterfall amount and associated organic carbon input in plantation forest (958.4 ± 112 g·m−2·yr−1; 391.4 ± 112 g·C·m−2·yr−1) were higher than those in the homegarden (183.5.4 ± 26 g·m−2·yr−1; 67.4 ± 10 g·C·m−2·yr−1), conceivably due to few litter contributors (trees) present in the homegarden. The CSR of the homegarden (1.3 ± 0.01) was found between the ratio obtained for crop (1.2 ± 0.01) and plantation forest (1.4 ± 0.01), indicating that it is definitely a combination of pure plantation forest and crop system. The CFBR was higher in plantation forest (3.4 yr−1) than in soil of homegarden (0.77 yr−1), implying the net accumulation of soil carbon over time in the latter system. Hence, homegardens could be considered as a system of climate-smart practice with multiple-biogeochemistry pathways, which simultaneously address the social-absolute needs. Given the current tendency of transforming homegarden agroforestry to monoculture types owing to economical drivers, such indicators can dictate of making rational decisions related to land use planning and soil fertility management.

The influence of carbon dioxide concentration on carbonation behavior in cement paste

Accelerated carbonation is the main method of simulating carbonation in the laboratory, but there are significant differences in the CO2 concentrations adopted for accelerated carbonation testing among the various standards currently. In this work, X-ray imaging technology was used to study the distribution of the carbonation zone in samples at different CO2 concentrations and used for imaging, which was followed by quantitative analyses of the carbonation profile and the material compositions of the entire carbonation zone in combination with thermogravimetric analysis (TGA) and 29Si nuclear magnetic resonance (29Si NMR) analyses. The results showed that the carbonation profiles of cement paste were similar under 3% and 10% concentration, with the front line of carbonation developing parallel to the soffit of the sample. However, when the concentration was increased to 20%, the carbonation profile at partial carbonation zone could be changed due to shrinkage cracking. In addition, the compositions of the complete carbonation zone under different concentrations were similar, and the development of this zone followed Fick's law.

Long-term saline water irrigation affected soil carbon and nitrogen cycling functional profiles in the cotton field.

Saline water irrigation (SWI) plays an important role in alleviating water resource shortages. At the same time, the salt input of irrigation water affects soil microorganisms which participate in various ecological processes of terrestrial ecosystems. However, the responses of soil microbial functional potential to long-term SWI remains unclear. Therefore, Metagenomics method was utilized in cotton fields under long-term SWI to reveal the microbial functional profiles associated with soil carbon and nitrogen cycles. Results indicated that SWI impacted the microbial functional profiles of soil carbon and nitrogen cycles in the cotton fields significantly. Especially, irrigation water salinity inhibited the relative abundances of sacC and vanB, which are soil carbon degradation genes. SWI also affected the functional gene abundance of nitrogen degradation, dissimilatory nitrate reduction, and nitrification. Moreover, SWI significantly increased the abundance of Candidatus_Cloacimonetes in both carbon and nitrogen cycles. In the discussion, we used person analysis found that soil salinity, pH, and ammonium nitrogen were important factors affecting the abundance of functional genes and microbial taxa. Overall, this study indicated that long-term SWI significantly influenced specific microbial functional genes and taxa abundance, which may lead to predictable outcomes for soil carbon and nitrogen cycling, and is of great importance in exploring the impact of SWI on soil environments.

Uncovering the world's largest carbon sink-a profile of ocean carbon sinks research.

As the world's largest carbon sink, the oceans are essential to achieving the 1.5°C target. Marine ecosystems play a crucial role in the "sink enhancement" process. A deeper comprehension of research trends, hotspots, and the boundaries of ocean carbon sinks is necessary for a more effective response to climate change. To this end, academic literature in the field of ocean carbon sinks was investigated and analyzed using the core database of the Web of Science. The results show that (1) The ocean carbon sink is a global study. The number of literatures in the field of ocean carbon sinks is growing, and the USA and China are the main leaders, with the USA accounting for 31.19% of the global publications and China accounting for 26.57% of the global publications, and the environmental science discipline is the most popular in this field. (2) Keyword burst detection shows that the keywords "sink, sensitivity, land, dynamics, and seagrass" appear earliest and have high burst intensity, which are the hot spots of research in this field; the keyword clustering shows that the global ocean carbon sinks research mainly focuses on three themes: (i) carbon cycle and climate change; (ii) carbon sinks estimation models and techniques; and (iii) carbon sinks capacity and ocean biological carbon sequestration in different seas. Finally, targeted research recommendations are proposed to further match the ocean carbon sink research.

LNG AND CLIMATE CHANGE: EVALUATING ITS CARBON FOOTPRINT IN COMPARISON TO OTHER FOSSIL FUELS

The increasing global demand for energy, coupled with growing concerns about climate change, has prompted a critical examination of the environmental impact of various energy sources. Liquefied Natural Gas (LNG) has emerged as a significant player in the energy landscape, touted for its potential as a cleaner alternative to traditional fossil fuels. This review provides a concise overview of a comprehensive evaluation that assesses the carbon footprint of LNG in comparison to other fossil fuels. The research delves into the lifecycle analysis of LNG, scrutinizing its carbon emissions from extraction and production to transportation and combustion. This holistic approach seeks to unravel the nuanced environmental implications associated with LNG utilization. Comparative analyses with conventional fossil fuels such as coal and oil are conducted, aiming to offer a comprehensive understanding of LNG's relative environmental performance. Key aspects covered include the environmental considerations throughout the LNG supply chain, encompassing extraction, liquefaction, shipping, regasification, and combustion. Special attention is given to technological advancements and innovations that influence the carbon intensity of LNG operations. The assessment incorporates recent data and insights, providing an up-to-date perspective on the evolving landscape of LNG's carbon footprint. The review highlights the significance of evaluating the entire spectrum of emissions associated with different fossil fuels, acknowledging the varying impacts on global warming potential. Additionally, the research considers regional and geopolitical factors influencing the sourcing and consumption of LNG, contributing to a nuanced understanding of its carbon profile in diverse contexts. As the world navigates the transition towards a more sustainable energy future, this research aims to contribute valuable insights into the role of LNG in mitigating climate change. The findings have implications for policymakers, industry stakeholders, and environmental advocates, offering a basis for informed decision-making and strategic planning in the pursuit of a low-carbon energy paradigm.&#x0D; Keywords: LNG, Climate, Carbon, Footprint, Fossil Fuels.

Effects of seasonal deposition-erosion cycle on sedimentary organic carbon remineralization and oxygen consumption in a large-river delta-front estuary

Seasonal sediment deposition-erosion events are dominant drivers of particle-solute dynamics in large-river delta-front estuaries (LDEs), but their influence on elemental cycles is not yet fully understood. To better constrain the role of deposition-erosion events on elemental cycling in LDEs, benthic fluxes of dissolved inorganic carbon (DIC), oxygen, and pore-water solute profiles were measured over different seasons in the Changjiang LDE. Benthic DIC efflux (23.4 ± 6.0 mmol C m−2 d−1) was greater than oxygen influx (7.5 ± 2.0 mmol O2 m−2 d−1) in summer but less in winter (7.7 ± 1.2 mmol C m−2 d−1 and 10.1 ± 1.5 mmol O2 m−2 d−1, respectively). The additional oxygen consumption in sediments in winter was likely due to the oxidation of inorganic diagenetic reductive products (IDRP) (e.g., NH4+, Fe2+, and Mn2+) in deeper sediments exposed by erosion, which resulted in the development of an “oxygen debt”. Sedimentary oxygen respiration accounted for at least 48 % of total oxygen consumption (oxygen consumption in both water column and sediment) in winter and was significantly greater than in summer (∼15 %); this highlighted the importance of winter sediment erosion in oxygen depletion. In addition to IDRP oxidation, the remineralization of resuspended sedimentary organic carbon in water column also contributed to the oxygen consumption. The global dataset on benthic DIC and oxygen fluxes provides evidence that the “oxygen debt” is likely to be widespread in LDEs, exerting a significant impact on global carbon and oxygen cycling.