Carbon Content Research Articles

Identification of Hot Gas around Low-mass Protostars

The low carbon content of Earth and primitive meteorites compared to the Sun and interstellar grains suggests that carbon-rich grains were destroyed in the inner few astronomical units of the young solar system. A promising mechanism to selectively destroy carbonaceous grains is thermal sublimation within the soot line at ≳300 K. To address whether such hot conditions are common among low-mass protostars, we observe CH3CN transitions at 1, 2, and 3 mm with the NOrthern Extended Millimeter Array toward seven low-mass and one intermediate-mass protostar (L bol ∼ 2–300L ⊙), as CH3CN is an excellent temperature tracer. We find >300 K gas toward all sources, indicating that hot gas may be prevalent. Moreover, the excitation temperature for CH3OH obtained with the same observations is always lower (∼135–250 K), suggesting that CH3CN and CH3OH have a different spatial distribution. A comparison of the column densities at 1 and 3 mm shows a stronger increase at 3 mm for CH3CN than for CH3OH. Since the dust opacity is lower at longer wavelengths, this indicates that CH3CN is enhanced in the hot gas compared to CH3OH. If this CH3CN enhancement is the result of carbon-grain sublimation, these results suggest that Earth’s initial formation conditions may not be rare.

Climatological distribution of ocean acidification variables along the North American ocean margins

Abstract. Climatologies, which depict mean fields of oceanographic variables on a regular geographic grid, and atlases, which provide graphical depictions of specific areas, play pivotal roles in comprehending the societal vulnerabilities linked to ocean acidification (OA). This significance is particularly pronounced in coastal regions where most economic activities, such as commercial and recreational fisheries and aquaculture industries, occur. In this paper, we unveil a comprehensive data product featuring coastal ocean acidification climatologies and atlases, encompassing the fugacity of carbon dioxide, pH on the total scale, total hydrogen ion content, free hydrogen ion content, carbonate ion content, aragonite saturation state, calcite saturation state, Revelle factor, total dissolved inorganic carbon content, and total alkalinity content. These variables are provided on 1° × 1° spatial grids at 14 standardized depth levels, ranging from the surface to a depth of 500 m, along the North American ocean margins, defined as the region between the coastline and a distance of 200 nautical miles (∼370 km) offshore. The climatologies and atlases were developed using the World Ocean Atlas (WOA) gridding methods of the NOAA National Centers for Environmental Information (NCEI) based on the recently released Coastal Ocean Data Analysis Product in North America (CODAP-NA), along with the 2021 update to the Global Ocean Data Analysis Project version 2 (GLODAPv2.2021) data product. The relevant variables were adjusted to the index year of 2010. The data product is available in NetCDF (https://doi.org/10.25921/g8pb-zy76, Jiang et al., 2022b) on the NOAA Ocean Carbon and Acidification Data System: https://www.ncei.noaa.gov/data/oceans/ncei/ocads/metadata/0270962.html (last access: 15 July 2024). It is recommended to use the objectively analyzed mean fields (with “_an” suffix) for each variable. The atlases can be accessed at https://www.ncei.noaa.gov/access/ocean-carbon-acidification-data-system/synthesis/nacoastal.html (last access: 15 July 2024).

Photosynthetic activity of crops and sequestration of atmospheric carbon by meadow clover and spring wheat in crop rotation

The purpose of the research is to estimate the intensity of absorption of light energy by crop rotation crops during the growing season and determine the amount of atmospheric carbon absorbed during photosynthesis. In a long-term stationary experiment, the absorption of photosynthetically active radiation (FAR) by crops of meadow clover for 2 years of use and spring wheat in variants without fertilizers and when applying N60P60K60 was studied. Chlorophyll A, chlorophyll B and carotene, which serve as photoreceptors-pigments of photosynthesis in higher plants, were used to assess the intensity of absorption of light energy. The most active period of absorption of HEADLIGHTS by meadow clover leaves was noted from the stalking phase to flowering, the amount of chlorophyll A and B in the leaves was 11.08…14.32 mg/g dry weight, carotene – 2.2…3.3 mg/g dry weight. During photosynthesis, the carbon content in clover leaves varied in the range of 40.4…45.5 %. The content of the main products of photosynthesis, sugars, decreased from 9.8 % in the stalking phase to 3.4 % during seed formation. The most intensive process of photosynthesis of spring wheat took place during the period from the tillering phase to the beginning of maturation, the chlorophyll content was 9.14…11.90 mg/g dry weight, carotene was 2.5…4.3 times lower. Most sugars were noted at the beginning of entering the tube: without fertilizers – 15.3 %, when applying NPK of 60 kg d. v./ ha – 17.2 %. The amount of carbon absorbed by meadow clover crops during photosynthesis during the growing season, depending on the experimental options, was 2.26…2.42 t/ha (8.09…8.66 t/ha CO2), spring wheat – 1.49…1.93 t/ha (5.33…6.90 t/ha CO2).

Spatiotemporal distribution and transport flux of organophosphate esters in the sediment of the Yangtze River

The Yangtze River Basin is an important area for organophosphate esters (OPEs) consumption and emission. Studies proved high OPE detection in Yangtze River water, but there is limited information about the spatiotemporal distribution and transport flux of OPEs in sediment. The present study investigated 16 OPEs in sediment from upstream to mid-downstream of the Yangtze River. The mean concentration of OPEs was 84.30ng/g, and alkyl-OPEs was the primary component. Great specific surface area and high content of organic carbon significantly increased OPE concentration in Three Gorges Reservoir (TGR) by physical adsorption and chemical bonds (p<0.05), making TGR the most contaminated area in mainstream. No significant differences in OPE constituents were found in seasonal distribution. Four potential sources of OPEs were identified by principal component analysis and self-organizing maps, and traffic emissions were the dominant source for OPEs. The hazard quotient model results indicated that aryl-OPEs showed moderate risks in the mainstream of Yangtze River, alkyl-OPEs and Cl-OPEs showed low risks. TGR was a significant sink of OPEs in Yangtze River and buried 7.41 tons of OPEs in 2020, a total of 14.87 tons of OPE were transported into the sea by sediment.

The Impact of Catastrophic Forest Fires of 2021 on the Light Soils in Central Yakutia

This paper presents the results of studying changes in the main parameters and properties of soils in larch and pine forests growing on sandy soils of the Lena-Vilyui interfluve of Central Yakutia, where catastrophic forest fires occurred in 2021. According to the remote monitoring information system of Rosleskhoz, in 2021, almost 8.5 million hectares of forests burned in Yakutia, which is considered as one of the largest forest fires in Russia and in the world in that year. After the fire passes through the forest floor, the content of organic matter decreases as a result of combustion processes. The acidity of the soil changes towards its alkalization due to the entry of combustion products. Changes in soil profiles occur; turbation processes begin more intensively, which in turn change the natural distribution of soil indicator values such as the organic carbon content, the pH, and the number of exchangeable bases. Due to the sharp increase in heat supply after a fire, the depth of seasonal thawing in the soils of burnt larch forests increases by a quarter and by twofold in pine forests. With the beginning of the thawing of the seasonally frozen layer, all the soils experience waterlogging, and ground water occurs above the permafrost.

Physical and geochemical responses to bottom trawling on naturally disturbed sediments in the eastern Bering Sea

Abstract Recent concerns that commercial bottom trawling can contribute to a significant release of sequestered marine carbon have highlighted a need for research in this area. Here, a Before-After Control-Impact (BACI) experimental design was utilized in a previously untrawled area of the eastern Bering Sea. Six pairs of experimental and control corridors were sampled before, after, and 1 year after a trawl disturbance. Each experimental corridor was fished four consecutive times over ∼12 h with a commercial otter trawl. Results were contextualized with minimum detectable effects (MDE), and showed no evidence of a trawl effect on total organic carbon (P = .999, MDE ± 0.05% TOC), total nitrogen (P = .999, MDE ± 0.02% TN), δ13C, and δ15N isotope ratios and sediment size classes. Interannual changes observed in δ15N, sand, silt, and clay are attributed to natural variation. The study suggests that the characteristics of the study site, such as storm disturbances, high sand content, and low carbon content, limited the bottom-trawl effect on sediment composition following this initial trawl disturbance. The findings highlight the importance of site-specific studies that account for local conditions to support best management practices for commercial bottom trawling.

Exploiting Soil and Remote Sensing Data Archives for 3D Mapping of Multiple Soil Properties at the Swiss National Scale

Soils play a central role in ecosystem functioning, and thus, mapped soil property information is indispensable to supporting sustainable land management. Digital Soil Mapping (DSM) provides a framework to spatially estimate soil properties. However, broad-scale DSM remains challenging because of non-purposively sampled soil data, large data volumes for processing extensive soil covariates, and high model complexities due to spatially varying soil–landscape relationships. This study presents a three-dimensional DSM framework for Switzerland, targeting the soil properties of clay content (Clay), organic carbon content (SOC), pH value (pH), and potential cation exchange capacity (CECpot). The DSM approach is based on machine learning and a comprehensive exploitation of soil and remote sensing data archives. Quantile Regression Forest was applied to link the soil sample data from a national soil data base with covariates derived from a LiDAR-based elevation model, from climate raster data, and from multispectral raster time series based on satellite imagery. The covariate set comprises spatially multiscale terrain attributes, climate patterns and their temporal variation, temporarily multiscale land use features, and spectral bare soil signatures. Soil data and predictions were evaluated with respect to different landcovers and depth intervals. All reference soil data sets were found to be spatially clustered towards croplands, showing an increasing sample density from lower to upper depth intervals. According to the R2 value derived from independent data, the overall model accuracy amounts to 0.69 for Clay, 0.64 for SOC, 0.76 for pH, and 0.72 for CECpot. Reduced model accuracies were found to be accompanied by soil data sets showing limited sample sizes (e.g., CECpot), uneven statistical distributions (e.g., SOC), and low spatial sample densities (e.g., woodland subsoils). Multiscale terrain covariates were highly influential for all models; climate covariates were particularly important for the Clay model; multiscale land use covariates showed enhanced importance for modeling pH; and bare soil reflectance was a major driver in the SOC and CECpot models.

Sheep rotational grazing strategy to improve soil organic carbon and reduce carbon dioxide emission from spring wheat in an arid region

Context Cultivating forage crops is crucial to improve feed production, and grazing is an important utilisation method to improve soil fertility. Aim Improving soil organic carbon (SOC) content and reducing carbon dioxide (CO2) emission through grazing management from a spring wheat field. Methods We compared sheep rotational grazing and control, and studied their effects on SOC and CO2 emission from a spring wheat field. Key results Sheep rotational grazing improved SOC content (by 23.5%) and soil easily oxidised organic carbon (EOC) content (by 7.7%) and reduces soil microbial biomass carbon (MBC) content (by 35.8%) compared with the control. Sheep rotational grazing reduced CO2 emission compared with the control. Sheep grazing reduced cumulative CO2 emission by 28.9% and 33.0% in May and June compared with the control. Conclusions Sheep grazing improved SOC content and reduce CO2 emission from a spring wheat field. Implications Based on our short-term study, sheep rotational grazing has a significant effect on SOC, EOC and MBC contents and CO2 emission from spring wheat fields in arid regions. For a large-scale assessment of sheep grazing on soil fertility and CO2 emission, more investigation for different soils and climates is necessary. Furthermore, a long-term study is also necessary to better understand the effect of sheep rotational grazing on soil fertility and CO2 emission from spring wheat fields in arid regions.

Solid‐State Bonding of Iron or Steel with Stainless Steels by Spark Plasma Sintering Bonding

In this study, pure iron, S45C carbon steel (Fe–0.45mass%C), carburized iron, and nitrided iron are bonded with two types of stainless steels, i.e., SUS304 austenitic stainless steel (Fe–18mass%Cr–8mass%Ni) with face center cubic structure or SUS430 ferritic stainless steel (Fe–18mass%Cr) with body center cubic structure by a spark plasma sintering (SPS) machine. Bonding experiments are carried out by SPS bonding. It is found that the bonding temperature of the S45C/SUS samples is lower than that of Fe/SUS samples, and carbon atoms in the S45C play important role on the bonding performance. The bonding temperature for SUS304/SUS430 sample is more than 30 °C higher than those for the Fe/SUS and S45C/SUS samples. The presence of thin chromium oxides on both stainless steels reduces the bonding performance of SUS304/SUS430 sample. Better bonding performance is found for the carburized and nitrided iron for bonding with stainless steels. However, continuous single‐phase layer on the surface leads to reduce the bonding performance. It is concluded that not only the concentration of carbon and nitrogen but also the phase configuration in the iron at interface strongly influences the bonding performance between iron alloys and stainless steels by SPS bonding.

Bamboo charcoal application altered the mineralization process of soil organic carbon in different succession stages of karst forest land

Introduction: As a soil amendment, Bamboo charcoal helps to contributes to the improvement of soil carbon sequestration, but its effect on the accumulation and transformation of different soil organic carbon in soil of karst forests is not clear.Methods: The research focused on three distinct forest land succession stages: virgin forest, secondary forest, and planted forest. A 60-day indoor constant temperature culture experiment was conducted, applying bamboo charcoal to the soil of the three forest lands at four different addition ratios: 0%, 1.0%, 2.0%, and 4.0%. The analysis aimed to study the characteristics of SOC mineralization, different carbon fractions of organic carbon, and soil enzyme activity.Results: The findings revealed that bamboo charcoal application led to an increase in the organic carbon (SOC) content within the three forest soils. Moreover, the organic carbon content showed an increase corresponding to the increased proportion of bamboo charcoal, with the highest SOC content observed in the planted forest land with 4.0% bamboo charcoal. The overall performance of the C0/SOC value in the three forest soils was ranked as follows: planted forest &amp;lt; secondary forest &amp;lt; virgin forest (C0: the mineralization potential of soil organic carbon). In both planted and secondary forest soils, the C0/SOC value increased after the application of bamboo charcoal. However, in the virgin forest soil, the application of 1.0% and 4.0% bamboo charcoal reduced the C0/SOC value, while the application of 2.0% bamboo charcoal increased the C0/SOC value. Particularly the C0/SOC value of the planted forest soil without bamboo charcoal was the smallest at 0.047, whereas that in the virgin forest soil with 2.0% bamboo charcoal had the largest value at 0.161.Discussion: Herein, appropriate human intervention can enhance the carbon sequestration potential of forest soil, in different succession stages within the karst area. However, the external application of bamboo charcoal does not significantly improve the carbon sequestration potential in the planted and secondary forest. Notably, applying a higher proportion (4.0%) of bamboo charcoal can enhance the organic carbon sequestration potential, particularly in the virgin forest soil, representing the climax community of forest succession.

Nitrogen‐Rich Carbon Nanodot‐Sensitized TiO2 with MWCNT Composites for Efficient Visible Light Photocatalysis

AbstractTiO2‐based composite photocatalysts are currently being explored to address concerns intrinsic to TiO2, specifically high charge carrier recombination and UV light activation. Among various materials utilized for composite formation, carbon nanomaterials stand out due to their high electron conductivity, charge storage, photosensitization, and surface properties. However, high carbon content in composites has been shown to reduce performance with potential toxicity concerns. To harness the diverse properties of carbon nanomaterials in a single composite while optimizing the carbon content below 1% by weight, multi‐walled carbon nanotubes (MWCNT)/TiO2 sensitized by carbon nanodots (CND) are synthesized. The heterojunction formed between MWCNTs and TiO2 in the binary composite reduced the charge carrier recombination rate compared to TiO2. The addition of CNDs to MWCNT/TiO2 induced visible light absorbance of the resulting ternary composite, due to the forbidden electron transitions undergone in CND aggregates. CND/MWCNT/TiO2 exhibited a fivefold and 1.6‐fold increase in photocatalytic degradation of acid orange 7 and tetracycline under visible light compared to TiO2. This enhancement is attributed to the photosensitizing property of CNDs working in synergy with the charge storage ability of MWCNTs. A plausible charge transfer pathway for the activity of CND/MWCNT/TiO2 is proposed.

Influence of Water Erosion on Soil Aggregates and Organic Matter in Arable Chernozems: Case Study

Since Chernozems are among the most fertile soils in the world, the study of their degradation is of great interest. However, the microstructure and composition of the soil organic matter (SOM) in eroded Chernozems have not yet been sufficiently studied. We studied the SOM and aggregate states of eroded Chernozems using the example of two catenas with arable Haplic Chernozems in the Kursk region of Russia. In the plow horizons (the part of the soil most susceptible to water erosion), we determined the mean-weighted aggregate diameter (MWD), structure and water stability coefficients (SC and WS; dry and wet sieving, respectively), soil organic carbon (SOC) content, and SOM composition and content (qualitative and quantitative micromorphological analyses, respectively). It was shown that with an increase in the degree of erosion, the content of SOC decreased significantly, according to both chemical and micromorphological methods of evaluation. No significant relationships were found between the degree of erosion and the indicators of the structure (except for WS, which was significantly lower in non-eroded Chernozem than in slightly and moderately eroded soils). With the increasing degree of erosion, the humus state of these soils deteriorates at the microlevel, the intensity of humification decreases, the depth of the appearance of assimilated biogenic aggregates with finely dispersed calcite in the profile increases, the structure is destroyed, lumpy aggregates form, and the proportion of planar voids increases. The downslope transport of the soil solid phase under the impact of erosion is accompanied by the accumulation of the transformation products of carbohydrates, phenolic compounds, and black carbon in the passive pool of SOM in the Chernozems in the lower part of the catena. In the Chernozems located in the transit position of the slope, the composition of SOM is characterized by the predominance of lipids and nitrogen-containing compounds. Our unique results contribute to a deeper understanding of the formation of structure and water resistance in eroded soils.

Organic substitution regime with optimized irrigation improves potato water and nitrogen use efficiency by regulating soil chemical properties rather than microflora structure

Context or problemImproving water and fertilizer use efficiency is an inevitable choice for sustainable potato production in North China. However, the regulation mechanism of potato water and nitrogen use efficiency under water-nitrogen coupling (W-N) regime is still unknown. Objective or research questionThe objectives from a 3-year field experiment were (1) to assess the impact of W-N regimes on potato yield and water and nitrogen use efficiency, (2) to elucidate the soil microflora structure under W-N regimes, and (3) to determine the relationship between soil chemical properties, microflora structure, and potato water and nitrogen use efficiency. MethodsA three-year two-factor split-zone potato field experiment was conducted in arid and semi-arid regions of the Inner Mongolian Plateau, with irrigation [(rainfed (W0), optimized (soil-based) irrigation (W1), conventional irrigation (W2)] as the primary treatment and N fertilizer [no N (N0), chemical N (N1), 25 % manure substitution (N2)] as the secondary treatment. ResultsPotato yield and water productivity followed N2 > N1 > N0, and partial nitrogen productivity and nitrogen agronomic efficiency followed N2 > N1 at the same irrigation level. Potato yield, nitrogen internal efficiency, partial nitrogen productivity and nitrogen agronomic efficiency first increased and then decreased, whereas water productivity gradually decreased with increasing irrigation levels under the same fertilization regime. Moreover, potato yield, soil total nitrogen, organic carbon, and microbial biomass carbon and nitrogen content peaked with the W1N2 regime. W-N regimes significantly influenced soil microbial community structure. Soil microbial α-diversity was less variable under W1 and N2 conditions. Soil bacterial network complexity and robustness were higher in W1 and W2 than in W0 regimes, whereas the opposite was true for fungi. The complexity and robustness of the soil bacterial and fungal network demonstrated for three fertilization regimes were higher in N1 and N2 than in N0 regimes. Neutral community model showed that soil microflora in W-N regime was mainly influenced by stochastic processes. PLSPM showed that organic substitution regime with optimized irrigation improves potato water and nitrogen use efficiency by regulating soil chemical properties rather than microflora structure. ConclusionsW1N2 regime synergizes well to improve potato water and N use efficiency and soil microflora stability, and organic substitution regime with optimized irrigation improves potato water and nitrogen use efficiency by regulating soil chemical properties. Implications or significanceOur findings initially clarified the regulatory mechanisms of potato water and nitrogen use efficiency in North China, offering theoretical guidance for further optimizing irrigation and fertilization management.

Mineralogical and geochemical characteristics of mudstones from the Lower Cretaceous Prosopis Formation in the Bongor basin, Chad: Implications for provenance, paleoenvironment and organic matter enrichment

The Cretaceous greenhouse represents the largest global warming event since the Phanerozoic, significantly affecting the provenance, weathering, regional climate, and paleoenvironment of lake basins globally. During the period of global warming, the control of regional paleoenvironment over organic matter enrichment is still unclear. The Lower Cretaceous Prosopis Formation in the Bongor Basin features thick lacustrine organic-rich mudstones as major effective hydrocarbon source rocks with excellent hydrocarbon potential in the basin. However, the provenance, paleoclimate, paleoenvironment and mechanism of organic matter accumulation in this location have not yet been systematically studied. In this study, 22 dark gray mudstone samples were collected from three cored wells. Clay mineralogy, along with organic and inorganic elemental geochemical analyses were jointly carried out to determine the characteristics of the provenance, paleoclimate and paleoenvironment as well as the major controlling factors for organic matter enrichment. The results imply that the Prosopis Formation mudstones are mainly composed of clay minerals such as illite, kaolinite, chlorite, and illite/smectite mixed layers (I/S). Organic geochemistry indicated that all the studied mudstones reached the standard of good to excellent source rocks (the total organic carbon content ranged from 1.27% to 7.41%). Inorganic elemental geochemistry is characterized by high enrichment of Fe, Mg, P, Mn, Ti, Na, Ca, V, Co, Cu, Sr, Ba and B relative to UCC and PAAS, whereas rare earth elements (REEs) show enrichment of light rare earth elements (LREEs) and a deficiency of heavy rare earth elements (HREEs) relative to chondrite. The source composition of the mudstones is predominantly intermediate-felsic igneous rocks that have not undergone sediment recycling. The parent rocks experienced weak to moderate weathering, corresponding to semiarid paleoclimatic conditions of transitional nature. The organic-rich mudstones were deposited in fresh to brackish waters with paleoredox conditions ranging from weakly oxic to anoxic semi-deep to deep lake environments having relatively low initial productivity. Comprehensive study indicates that paleoredox and paleoclimate are important parameters affecting the enrichment of organic matter in lake basins during global warming. The aridification of climate is one of the most important reasons for the high input and efficient preservation of organic matter. The relatively semiarid climate both increased the supply of terrigenous nutrients to the lake basins and provided a driving force for the increase in salinity, thereby providing better sources and preservation conditions for organic matter.

The performance and charge behaviour in melter/smelter for the production of hot metal in hydrogen DRI-based steelmaking

Direct reduced iron (DRI)-based steelmaking requires high-grade iron ore (Fe &gt; 65 wt-%). However, a swift decline in ore grade has forced steelmakers to use lower-grade ores for DRI making, creating challenges in subsequent processes dealing with high gangue content for steelmaking. Hence, an intermediate melting/smelting furnace has been proposed to treat high gangue content from the DRI before transferring hot metal into an electric arc furnace (EAF)/basic oxygen furnace (BOF) for steelmaking. This study investigates and models the performance and charge behaviour in a melter/smelter with respect to the gangue content, DRI carbon content and temperature. The results showed that the specific energy consumption (SEC) and off-gas production increase with increasing temperature, carbon in DRI and gangue content. At 90 wt-% metallisation ratio (MR) using the lowest-grade ore (gangue 16 wt-%), the SEC at 1300 °C was calculated to be 706 kWh/tHM compared to 850 kWh/tHM at 1600 °C using 3.5 wt-% carbon. The MR is predicted to profoundly impact the SEC, as the increasing MR decreases the SEC markedly. At 90 wt-% MR, the SEC using the lowest-grade ore was 805 kWh/tHM, decreasing to 684 kWh/tHM using 100 wt-%MR. Increasing MR, carbon in DRI and temperature decreases slag production consistently while increasing with the increasing gangue. Using hot DRI onsite is predicted to significantly reduce the SEC compared to cold DRI. Overall, the energy demand from cold DRI is predicted to be 120 kWh/tHM higher than hot DRI. Increasing the scrap-to-DRI ratio is predicted to decrease the energy demand, that is, every 1.0 wt-% increase in scrap decreases the SEC by 2.5 kWh/tHM.

An Analysis of Primary Contributing Sources to the PM2.5 Composition in a Port City in Canada Influenced by Traffic, Marine, and Wildfire Emissions

Ambient air quality, specifically fine particulate matter (PM2.5) pollution, poses a global health concern due to its associations with adverse health effects and persistent presence in urban settings. This study investigates PM2.5 exposure in a traffic-influenced residential area in Vancouver, employing chemical speciation data sampled in the vicinity of a major road throughout 2018. Using receptor-oriented models, Positive Matrix Factorization (PMF), and Principal Component Analysis (PCA), major emission sources contributing to the total PM2.5 mass were identified. The Organic and Elemental carbon concentration time series analysis reveals impacts from traffic and episodic influences from wildfires and residential heating. Applying PMF, we attribute identified factors to specific sources: traffic (33%), secondary aerosols (27%), dust (14%), Marine Heavy Fuel Combustion (HFC) (12%), Local (9%), and rare metallic elements (5%), respectively. This apportioning is subsequently verified by PCA, which introduces a sea salt factor to the analysis. Applying the conditional probability function analysis on the integrated wind speed and direction, and the PM concentration data further confirms the partial PM mass apportionment to marine HFC, rare metallic elements, and local factors. Lastly, comparing the results with the 2015 emission inventory of Vancouver shows similarities in apportioning the share of primary sources while overlooking secondary emissions in the latter, emphasizing the importance of field sampling for accurate source characterization. This study highlights the necessity of receptor modeling coupled with field sampling in quantifying the contribution and chemical characteristics of secondary emission sources, particularly near residential neighborhoods. Precise characterization aids health exposure studies that contribute to informed air quality management and policy regulations.

Leaching phosphorous from the lime mud of kraft pulp mills: Towards sustainability

AbstractThe optimum conditions needed to separate phosphorus from the lime mud generated in kraft pulp mills were identified using different leaching solutions including carbonate, bicarbonate, and green liquor under variety of conditions. Carbonate ions seemed to be the active ion in the phosphorus leaching process. Bicarbonate solution seems to be the most effective leaching agent by removing 84% of phosphorus under the optimum operating conditions of 95°C, 2.92 m, and solution‐to‐ mud mass ratio of 3.6. The shrinking core model was used to determine the leaching mechanism and it showed that the leaching process is controlled by a mix of chemical reaction and diffusion through the particle. Two empirical models were developed to predict the leaching efficiency as a function of carbonate concentration and temperature. Counter‐current leaching was shown to be beneficial in increasing the leaching efficiency with the carbonate solutions.

Ultra-high temperature brazing of C/C using a simplified FeNiCrCu high-entropy alloy as filler

To increase remelting temperature of C/C brazed joint, a simplified FeNiCrCu high-entropy alloy (HEA) filler was designed in high-temperature brazing (HTB). The joint formation mechanism and fracture behavior were studied. The eutectic reaction of FeNiCrCu HEA with C/C could not occur, helping increase joint remelting temperature over HEA melting point (1334 °C). For the recommended parameter 1350 °C-2 min, dissolution of C/C occurred well, and no defect was observed both at interface and within bond seam. The maximum shear strength was 24.2 MPa due to the high strength in-situ (Cr,Fe)3C2 reinforced the high plastic Cu-Ni-Fe(S.S.) matrix and intimate wavy interface. Cr existed only in M3C2 in bond seam, reducing both carbon content and CTE of bond seam. For higher temperature and longer time, excessive dissolved carbon content resulted in the presence of large solidified carbon with defect at interface, joint shear strength decreased dramatically. These results provide a unique braze system for brazing carbon-based materials.

Organic geochemical and petrological investigations of the upper miocene bongaya formation in the pitas, onshore sabah basin, and its relevance for hydrocarbon potential

AbstractThe Upper Miocene Bongaya Formation coal, carbonaceous shale, and shale sediments were collected to investigate their origin, types, and maturity. The main objectives of this study were to verify and update previous claim of possible hydrocarbon showings and to gain new insights about the petroleum potential using different geochemical analysis approach. The primary methodology used in this study is the pyrolysis technique and coupled with petrographic analysis. The bulk geochemistry results revealed that the Bongaya sediments serve as favorable source rock, with the total organic carbon (TOC) content ranging from 0.90 to 63.10 wt% by weight, indicating fair to excellent organic richness. The coal samples exhibited the highest TOC values, followed by carbonaceous shale samples, while shale and coal laminated with sandstone samples displayed fair TOC amounts. Most of the Bongaya sediments analyzed in this study exhibited hydrogen index (HI) values of less than 200 mg HC/g TOC, indicating Type III organic matter, which signifies a significant influence of terrestrial organic matter. However, three coals displayed comparatively higher pyrolysis HI values, corroborated by Pyrolysis gas-chromatography (Py-GC) results and maceral types, indicating a mixture of Type II/III kerogen. This suggests that the Bongaya Formation sediment has the potential to generate gas with minor oil. Maceral analysis also revealed that most of the coal samples contained a high content of resinite maceral, which explains the waxy composition of the oil. The organic matter in the analyzed Bongaya sediments was found to be immature for petroleum generation, as evidenced by low huminite reflectance data (lower than 0.50% VR) and Tmax values between 372 and 432 °C. Consequently, the kerogen in the studied onshore Bongaya sediments has yet to enter the hydrocarbon cracking (catagenesis) phase before expelling petroleum. Therefore, it is essential to consider the offshore equivalent Bongaya sediments, which may be laterally extended offshore and buried at deeper depths to attain optimal maturity for hydrocarbon generation.

Is the impact of groundwater on lake greenhouse gas dynamics underestimated? A comparative analysis of subsurface and ecological factors

Lakes are recognized as important sources of greenhouse gases (GHGs) emissions to the atmosphere, influenced by various ecological processes. Groundwater discharge into lakes, despite its small volume, has high concentrations of dissolved carbon and nitrogen that significantly affect the production and emission of GHGs from lakes. Therefore, a comprehensive investigation of the mechanisms behind lake GHGs emissions under the influence of groundwater discharge and ecological processes, holds substantial scientific importance. However, due to uncertainties and quantification challenges associated with groundwater discharge, related research is currently limited. Here, we conducted year-round field observations on Honghu Lake, a large shallow eutrophic lake in Hubei Province, China. We analyzed the seasonal variation of GHGs emissions and quantified the groundwater discharge flux using radon (222Rn). The fluxes of methane (CH4), carbon dioxide (CO2), and nitrous oxide (N2O) at the water–air interface were estimated to be 31.1 ± 4.88 mg m−2 d−1, 386 ± 90.7 mg m−2 d−1, and 0.327 ± 0.072 mg m−2 d−1, respectively. CH4 is the primary greenhouse gas in Honghu Lake, contributing to 82.2 % and 62.2 % of the lake’s total emissions over 20-year and 100-year frames. The average rate of groundwater discharge was 8.19 ± 0.471 mm d−1, with the highest discharge rate in winter and the lowest in spring. The daily groundwater discharge volume accounts for 0.649 % of the lake’s total water volume. The daily contributions of groundwater discharge to the lake’s total emissions of CH4, CO2, and N2O were 0.318 %, 12.1 %, and 2.59 %, respectively. The facilitative role of groundwater discharge in CO2 emissions primarily manifests through the transport of dissolved organic carbon (DOC) and high concentrations of CO2 into the lake. Meanwhile, CH4 emissions depend on the activity of methanogenic bacteria, substrate availability, and anaerobic conditions, whereas N2O emissions are influenced by temperature and nutrient levels. Our study reveals that in the short term, the effect of groundwater on lakes is relatively minimal. Yet, its long-term role as a steady supplier of carbon and nutrients to lakes should not be overlooked. This study reveals the ways in which groundwater discharge and internal lake dynamics collectively fuel GHGs emissions. Our findings offer a new perspective and critical theoretical support for the assessment of lake greenhouse gas emissions.