Different Forms Of Carbon Research Articles

Sediment porewaters serve as a transient organic carbon pool at the land-ocean interface

The organic carbon (OC) cycle at the land-ocean interface is an important component of the global carbon budget, yet the processes that control the transfer, transformation, and burial of OC in these regions remain poorly understood. In this work, we examined sedimentary OC (SOC) in short core sediments, dissolved inorganic carbon (DIC), dissolved organic carbon (DOC), and chromophoric dissolved organic matter (CDOM), as well as other solutes in sediment porewaters of the Changjiang Estuary and adjacent East China Sea (ECS) shelf. The main goal of this work is to investigate the variation of the sources and composition of different forms of carbon in estuarine sediments associated with different sedimentary regimes, to further understand the role of sediment porewater in carbon sequestration at the land-ocean interface. Concentrations of Fe2+ and Mn2+ in porewaters of the muddy sediments are much higher than those in the sandy sediments, and SO42− decreases with depth in the deep sediment layer, indicating the degradation of SOC in mobile muds is mainly driven by suboxic and/or anoxic diagenetic processes (e.g., iron-manganese reduction). The accumulation of DIC in the muddy sediment is higher compared to the sandy sediment, indicating relatively complete SOC remineralization. The DOC in porewaters of the muddy areas is mainly composed of highly degraded and low molecular weight humic-like substances (C1), whereas in the sandy area, porewater DOC is mainly composed of less degraded and high molecular weight protein-like substances (C2 and C3). The average DOC stock (28.5 t/km2) in the upper 30 cm sediment porewaters is significantly higher than that of DIC (12.5 t/km2) in sandy area, but less in muddy areas (17.0 t/km2 of DOC vs. 25.4 t/km2 of DIC). The total DOC stock in sediment porewaters of the sandy area accounted for ∼61 % of DOC stock in water column of the ECS, indicating that the porewater is an important DOC pool in the ECS. However, this DOC pool is rather transient due to its high reactivity and mobility, especially in sandy area. Nevertheless, compared with other marine environments, the carbon stock of DOC (average of 43.8 t/km2) in porewaters of stable sedimentary environments is much higher than that of DIC (average of 21.7 t/km2). This work further supports the notion that sedimentary regime plays an important role in OC cycling at the land-ocean interface and highlights the significance of sediment porewaters as a vast carbon pool in marine ecosystems.

Podejście do jakości wody w zlewni osadzonej w krajobrazie rolno-leśnym nieznacznie zdegradowanym przez działalność rolniczo-hodowlaną

The headwater streams constitute landscapes with their own entity and are strongly influenced by their environment. They have a large impact on health and integrity, both for water quality and wildlife downstream. Studies on water quality from atlantics agroforestry catchments are scarce. Knowledge about water quality in agroforestry headwater catchments is important for assessing downstream effects and as a baseline for net impacts of land-use change. We analyzed physicochemical water variables of a headwater stream framed in a rural-agroforestry catchment with very little agricultural area, low livestock density and very little human population in NW Spain. Stream water samples were collected at the catchment outlet at approximately biweekly intervals over three years. All water samples were analyzed for the following quality parameters: pH, water temperature (T), electrical conductivity (EC), dissolved oxygen (DO), chemical oxygen demand (COD), major cations (Ca, Mg, Na, K), anions (Cl, SO4), nutrients [total dissolved carbon (TDC), dissolved organic carbon (DOC), nitrites nitrogen (NO2-N), nitrate nitrogen (NO3-N), ammonium nitrogen, Kjeldahl nitrogen (KN), total nitrogen (TN), dissolved, particulate and total phosphorus (DP, PP, TP)], and suspended solids (SS). Discharge was also measured. The mean concentrations of major anions, cations and different forms of carbon, nitrogen and phosphorus were rather low compared to global “average” values. Overall, the mean values of the main physicochemical water quality indicators offers similar values to those found in other rural catchment in humid temperate climates with low agricultural activity and demography, although such concentrations could have been underestimated as they mostly correspond to regular sampling and therefore ignore the influence of rainfall-runoff events.

Microorganisms Directly Affected Sediment Carbon–Nitrogen Coupling in Two Constructed Wetlands

Clarifying the carbon–nitrogen coupling pattern in wetlands is crucial for understanding the driving mechanism of wetland carbon sequestration. However, the impacts of plants and environmental factors on the coupling of carbon–nitrogen in wetland sediments are still unclear. Sediment samples from plant (Typha angustifolia and Phragmites australis)-covered habitats and bare land were collected in two constructed wetlands in northern China. The contents of different forms of carbon and nitrogen in sediments and plants, and the sediment microbial community were detected. It was found that the sediment carbon to nitrogen (C/N) ratios did not differ significantly in the bare sites of different wetlands, but did in the plant-covered sites, which highlighted the different role of plants in shifting the carbon–nitrogen coupling in different constructed wetlands. The effects of plants on the sediment carbon–nitrogen coupling differed in two constructed wetlands, so the structural equation model was used and found that sediment microorganisms directly affected sediment C/N ratios, while water and sediment physicochemical properties indirectly affected sediment C/N ratios by altering sediment microbial functions. Multiple linear regression models showed that water pH, sediment moisture content, water dissolved oxygen, and water depth had a greater influence on the carbon metabolism potential of the sediment microbial community, while sediment moisture content had the greatest impact on the sediment microbial nitrogen metabolism potential. The study indicates that variations in environmental conditions could alter the influence of plants on the carbon and nitrogen cycles of wetland sediments. Water environmental factors mainly affect microbial carbon metabolism functions, while soil physicochemical factors, especially water content, affect microbial carbon and nitrogen metabolism functions.

Effects of heavy rain on the concentrations and forms of carbon, nitrogen and phosphorus in urban rivers of northern China.

Non-point source pollution caused by rainfall runoff is an important pollution source for river water. To explore the impact of heavy rain on urban river water environments, this paper studied the changes in carbon, nitrogen, and phosphorus levels, composition, and structure in the river water of Kaifeng, China, during the heavy rain in July 2021. The results showed that the concentrations of different forms of carbon, nitrogen, and phosphorus all increased under the effect of the heavy rain. The increase of phosphorus in the river was the largest, and that of carbon was the smallest. The most significant pollution from carbon, nitrogen, and phosphorus occurred in the HJ River. Colored dissolved organic matter (CDOM) was present in the form of macromolecules after the rain, and the degree of humification was deeper compared with before the rain. But heavy rain did not affect the CDOM composition in urban rivers. The spectral slope (SR) and the absorption coefficient at 240nm to 420nm (E2/E4) values showed that the CDOM was dominated by exogenous input after the rain, with endogenous pollution again becoming the main factor one week after the rain.

Comparison of near and mid-infrared reflectance spectroscopy for the estimation of soil organic carbon fractions in Madagascar agricultural soils

Assessing the different pools of soil organic carbon (SOC) improves our understanding of how and at what rate the different forms of carbon (C) are being formed or lost in soils. Physical fractionation of soil organic matter (SOM) has often been used to separate and quantify SOC pools, but this approach is very tedious and can rarely be performed on large sample sets. Infrared spectroscopy has proven useful for time- and cost-effective quantification of total SOC, which prompted us to study its ability to characterise the distribution of SOC in physical fractions. This study aimed to compare the potential of near- and mid-infrared reflectance spectroscopy (NIRS and MIRS, respectively) to predict the distribution of SOC in particle-size and particle-density fractions, using spectra of unfractionated soils. A set of 134 sieved (< 2 mm) soil samples originating from seven sites in contrasting pedoclimatic regions of Madagascar was studied. For each sample, five SOM fractions were separated: the particulate organic matter fraction (POM) and the particle-size fractions >200 μm, 50–200-μm, 20–50-μm and < 20 μm. The mass (g fraction 100 g−1 soil), SOC concentration (gC kg−1 fraction) and SOC amount (gC fraction kg−1 soil) were determined for each fraction in the laboratory. The NIR and MIR spectra were acquired on finely ground (< 0.2 mm) aliquots of unfractionated soil. Then, spectra were used for the prediction of each variable (i.e., the mass, SOC concentration and amount of each fraction, and SOC content of unfractionated soil), which was achieved with locally weighted partial least squares regression (LW-PLSR) on NIRS and MIRS data separately. For both spectral ranges, the same samples were used for calibration (n = 109, selected for spectral representativeness) and validation (n = 25).Models based on NIRS and MIRS yielded excellent predictions for SOC content in unfractionated soil (R2 = 0.98 and ratio of performance to interquartile range RPIQ ≥13) and accurate predictions (R2 ≥ 0.75 and RPIQ ≥2) for the mass, SOC concentration and SOC amount in most fractions. The predictions of SOC concentrations and SOC amounts were better in the fractions <200 μm (R2 ≥ 0.85 and RPIQ >3), especially in the fraction <20 μm (R2 > 0.9 and RPIQ >4.5). In most cases, NIRS slightly outperformed MIRS. This result contradicts most previous studies performed on soils from temperate regions but confirms those performed on soils from tropical regions.Infrared spectroscopy allowed accurate prediction of SOC distribution in particle-size fractions, which paves the way to high-throughput characterization of SOM.

The influence of the deep subtropical reservoir on the karstic riverine carbon cycle and its regulatory factors: Insights from the seasonal and hydrological changes

Reservoirs are widely established worldwide with considerable environmental impacts, especially on the riverine carbon cycle. However, the influence of reservoirs on the cycling of different forms of carbon and its regulation factors (e.g., seasonal variations versus hydrological management) have not been simultaneously studied. To fill this knowledge gap, seasonal water samples from the deep subtropical reservoir (Longtan reservoir) in the Pearl River were collected, and the concentrations and stable carbon isotopes of dissolved inorganic carbon (DIC), dissolved organic carbon (DOC), and particulate organic carbon (POC) were determined. The variations in stable carbon isotopes of DIC (-11.4‰ to -5.2‰), DOC (-32.2‰ to -26.2‰), and POC (-38.9‰ to -25.3‰) in the river-reservoir system indicated active production and degradation processes in different layers. We estimated that up to 23.0% of DIC, 20.5% of DOC, and most POC were intercepted or degraded within the reservoir. Our results further illustrated that hydrological management (water storage regulation) and seasonal variations from different perspectives controlled the cycling of different forms of carbon in the reservoir. In addition, with the gradual increase in the number of reservoirs, hydrological management can be considered as a potentially effective strategy to adjust the carbon biogeochemical cycling of reservoirs in the future.

Microbial-mediated contribution of kelp detritus to different forms of oceanic carbon sequestration

Kelp is one of the most important primary producers in the coastal oceans. When it matures or begins to decay, a substantial amount of detritus sinks and is degraded by microorganisms. However, the fate of these detritus after long-term microbial degradation, which is closely related to their ultimate carbon sequestration function, is not yet clear. Here, by studying the long-term (210-day) microbial degradation dynamics of kelp detritus, we reveal that the bioavailable components of kelp detritus (when kept in the dark) persisted for over four months. This left a considerable amount (in total, ca. 8.85%) of different forms of stable carbon that could function in long-term carbon sequestration. Among them, recalcitrant dissolved organic carbon (RDOC), recalcitrant particulate organic carbon, dissolved inorganic carbon, particulate inorganic carbon, and residual large particulate carbon accounted for 1.27%, 0.12%, 6.00%, 0.04%, and 1.41% of the initial kelp detrital carbon, respectively. The remaining organic carbon resisted further degradation due to the high content of humic-like substances, polycyclic aromatics, and highly aromatic compounds. Microbial community structure showed obvious successional characteristics during the long-term degradation process, driving the gradual transformation of the detritus-derived organic carbon from labile to recalcitrant. Notably, microbial transformation of the bioavailable components of kelp detritus contributed 28.7% of the remaining RDOC molecular species. This study provides novel insights into the contribution of the microbial-mediated degradation of kelp detritus to different forms of carbon sequestration.

Assessment of remediation of soils, moderately contaminated by potentially toxic metals, using different forms of carbon (charcoal, biochar, activated carbon). Impacts on contamination, metals availability and soil indices

The present study aims to assess the effect of three forms of carbon, i.e., charcoal, biochar and activated carbon using as soil amendments (or soil conditioners) in two soils, an acid and alkaline one. For this purpose, a pot experiment was conducted by mixing six sub-samples for each soil along with the three amendments in the appropriate proportion. Total, pseudo-total and available metal concentrations were determined. Moreover, the BCR fractionation method was applied and the four soil fractions were identified. A significant decrease in the concentrations of all four metals in the water-soluble and exchangeable fraction (F1) was observed. At the same time, a high reduction was observed in the available concentrations of metals as well, ie those that were extracted after using the DTPA solution. Soil indices were also used in order to monitor and evaluate the possible ecological risk and the effect in metal concentrations after the application of the amendments. The use of the studied materials can be very promising soil conditioners, as they can precisely, economically, time-effectively, and efficiently can remediate soils, moderately contaminated with toxic metals.

Spatial-temporal distribution of carbon, nitrogen and phosphorus concentrations and eutrophication evaluation of mountainous small river in a cascaded damming

梯级筑坝对河流水环境演化的影响是国内外关注的热点.小型山区河流高密度梯级开发对水体生源要素的空间格局以及水环境演化的累积影响特征尚不清楚.以重庆市五布河为研究对象，对流域内8个“河流-水库-下泄水”交替系统中表层水体理化因子及碳（C）、氮（N）、磷（P）形态组成进行季节性监测，探讨了梯级筑坝对小型河流生源要素空间格局及水体富营养化风险影响的累积特征及驱动机制.结果表明：梯级水电开发对五布河流域水生生境和生源要素空间分配的影响具有潜在的累积效应，各库区水体碳氮磷浓度均呈逐级增加的空间规律；水库段的有机碳及不同形态的氮、磷浓度均高于入库河流，因此水体养分浓度呈现出河段尺度（即单个河流-水库-下泄水系统）和流域尺度（即上游至下游）耦合的空间变异模式.上游水库中溶解性氮、磷的再释放及下泄输移能够补给下游库区，加之下游水库泥沙对氮、磷的吸附-沉积作用的减弱，导致水体氮、磷总量及溶解性氮、磷的占比沿程增加，呈现梯级筑坝对水环境演化的累积影响.梯级筑坝影响下河流碳氮磷总量的相关性减弱，而溶解性养分间的相关性增强，形成了特殊的养分协同演化；水库群之间水力滞留时间的差异与水体碳氮磷浓度具有较好的线性关系，是影响流域养分分配的关键因素.五布河流域水体均为高富营养化风险，由于梯级筑坝下水体溶解性养分的逐级增加，下游水库水华风险更大；水力滞留时间与水体富营养化指数及叶绿素a浓度呈显著正向关，结合氮磷比特征的分析，本研究认为外源磷输入控制及水力滞留时间的调节是五布河梯级水库富营养化防控的有效途径.;Rivers, as the channel connecting terrestrial and marine ecosystems and transporting a large amount of nutrients to ocean, are important for maintaining the global material cycle. The construction of cascade dams leads to river fragmentation and changes the distribution of carbon, nitrogen and phosphorus in the water. At present, a lot of studies have been conducted on the ecological effects of cascade development in large rivers, but few studies focus on small mountainous rivers. The spatial-temporal patterns and controls of the distribution of carbon, nitrogen and phosphorus from cascade river-reservoir systems in the small mountainous rivers remain unclear. In this study, we investigated the spatial-temporal variations of carbon(C), nitrogen(N) and phosphorus(P) concentrations along a cascade damming river (Wubu River) in Southwest China. The results showed that carbon, nitrogen and phosphorus showed an obvious cumulative effect, that was, the contents of C, N and P gradually increased from the first reservoir upstream to the last reservoir downstream underlying cascade dams. And, the organic carbon, as well as nitrogen and phosphorus in the reservoir section, were higher than in those inflow rivers. Thus, different forms of carbon, nitrogen, and phosphorus concentration in the reach (river-reservoir-release water system) scale and river basin scale (the upstream to downstream) displayed the double coupling variation pattern. Primary production and plankton proliferation were the main mechanisms of organic carbon accumulation in the river. At the same time, cascade reservoirs may form a series of nitrogen and phosphorus storage tanks and reactors to promote the release and transport of dissolved nitrogen and phosphorus. The re-release and transport of dissolved N and P in the upstream reservoir can replenish the downstream reservoir, increasing the content of N and P in the downstream reservoir and the proportion of dissolved N and P, thus leading to the cumulative effect of water deterioration. The decrease in the adsorption-deposition effect of sediment on nitrogen and phosphorus nutrients in downstream reservoirs also leads to the accumulation of soluble nitrogen and phosphorus concentrations. The correlation of C, N and P in the river was weakened, but there was a significant relationship between dissolved nutrients, forming a special nutrient co-evolution. Furthermore, the hydraulic retention time of the reservoir groups had a good linear relationship with water C, N and P contents, which was the key factor affecting nutrient allocation in the watershed. Seasonal variations of total organic carbon and dissolved organic carbon were highest in spring and lowest in winter in Wubu River Basin. Total nitrogen and nitrate nitrogen in the dry season (winter and spring) were significantly higher than those in the wet season (summer and autumn), and other nutrient forms had no obvious seasonal pattern. Rainfall dilution, algal reproduction, microbial decomposition and re-release were the main processes leading to the seasonal variation of nutrients. The eutrophication risk also presented an increasing trend from upstream to downstream because of the dam. There was also a good linear relationship between hydraulic retention time and eutrophication risk. Combining the analysis of N:P ratio characteristics, it was suggested that exogenous P control and optimal allocation of hydraulic retention time are effective approaches for eutrophication control in the Wubu River Basin.

Effect of different carbon allotropes on optical properties of CoCuMnOx solar selective coating

This study investigates the inclusion of different forms of carbon in CoCuMnOx solar selective coating via the low-energy consumption method “sol-gel technique”. The usage of carbon as an additive in CoCuMnOx was an attempt to enhance the spectral selectivity. Four allotropes of carbon (graphene nanoplatelets (GNP), carbon nanotubes (CNT), graphite, and charcoal) were embedded in the selective coating with different concentrations and then were deposited on smooth and roughened stainless-steel sheets. In an additional attempt to improve CoCuMnOx selectivity, three different coatings (silica, charcoal@silica, and CNT@silica) were individually applied on top of it. Each carbon allotrope showed distinct structural and optical properties of the coating. Using charcoal as an additive achieved a solar absorptance of 0.964 and a thermal emittance of 0.095, thus providing superior optical properties compared to the other allotropes. The characteristics of the coatings were detected by X-ray diffraction, Energy Dispersive X-Ray analysis, and Scanning Electron Microscope.

Different forms of carbon, nitrogen, and phosphorus influence ecosystem stoichiometry in a north temperate river across seasons and land uses

AbstractNatural and human features on land result in differential loadings of carbon (C), nitrogen (N), and phosphorus (P) to rivers that influence within ecosystem processing. However, little is known about how land use, together with seasonal changes in climate and hydrology, influence the relative proportions of C, N, and P in rivers. To evaluate the spatial and temporal patterns in ecosystem‐level C: N: P stoichiometry, we sampled 13 sites once per season for 3 yr along the main stem of a north temperate river with winter ice‐cover that flows across a gradient of forested, urban, and agricultural landscapes. We found that C concentrations were rather stable along the continuum, whereas N and P rapidly increased downstream due to urban and agricultural land uses. The flow‐weighted C: N: P ecosystem stoichiometry ranged from 2319: 119: 1 in the most upstream site to 368: 60: 1 at the outlet. The dominant form of N generally shifted from dissolved organic nitrogen in upstream forested reaches to nitrate in more impacted, downstream reaches, and winter stoichiometry was enriched in inorganic N and dissolved P forms. Concentrations of all three elements were generally lower in spring during year‐high flow due to dilution. The spatial and temporal variation in stoichiometry in this north temperate river covered much of the range previously observed between litter ratios and the Redfield ratio. This suggests that even moderate human impacts can have profound effects on riverine ecosystem stoichiometry, and that these effects are modulated by seasonal trends in temperature and hydrology.

Effect of different forms of carbon on the reduction behaviour of iron ore-carbonaceous material composite pellets in multi-layer bed rotary hearth furnace (RHF)

ABSTRACT The present study investigates the effect of different forms of carbon in various coal and char-based composite pellets on reduction kinetics in a laboratory-scale multi-layer bed rotary hearth furnace at 1250°C. A novel plot showing the variation of DOM (degree of metallization) against DOR (degree of reduction) demonstrated the role of heat and mass transfer in the reduction process irrespective of layers and type of pellets. Char-based composite pellets exhibited higher reduction efficiency than coal-based pellets, even at comparable fixed carbon levels, attributed to micro-porous morphological features, and less fayalite formation in the char-based pellets. Top layer registered the maximum extent of reduction, and middle layer registered the minimum. Bottom layer also showed comparable reduction to the top layer due to more active volatile contribution at the bottom layer. Formation of fayalite at the top layer restricted the maximum extent of reduction beyond 80%.

The Role of Pyrolysis and Gasification in a Carbon Negative Economy

The International Panel on Climate Change and the 2015 Climate Summit in Paris have recommended that efforts to reduce carbon emissions be coupled with carbon removal from the atmosphere. Carbon negative energy combines net carbon removal with the production of energy products or other revenue-generating products beyond sequestered carbon. Even though both biochemical and thermochemical approaches to carbon negative energy can be envisioned, this paper considers the prospects for the latter including pyrolysis and gasification. The fundamentals of these two processes are described to better understand how they would be integrated with carbon removal. Characteristics of pyrolysis and gasification are related to the kinds of sequestration agents they would produce, the scale of their deployment, the fraction of biomass carbon that could ultimately sequestered, the challenges of effectively sequestering these different forms of carbon and the economics of thermochemical carbon negative energy.

Dissimilatory iron reduction and potential methane production in Chagan Lake wetland soils with carbon addition

Dissimilatory iron reduction is increasingly becoming recognized as an influential process in freshwater sediments, coupling with carbon cycling. To evaluate the influence of organic matter addition on the reduction rates and dynamics of Fe(III) in wetland soils in Chagan Lake, soil slurry and microbial anaerobic incubation studies were conducted by adding a soluble and redox-active quinone (anthraquinone-2,6-disulphonate, AQDS), glucose and sodium pyruvate. In soil slurry experiment, glucose was added as a single doze and a pulsed input over time. Pulsed glucose addition promoted DIR, particularly in the later incubation stage. The addition of different forms of carbon significantly affected DIR in the inoculation experiment, and the addition of pyruvate increased DIR more than that of glucose in the wetland soil. The AQDS dramatically stimulated the potential DIR by 480-fold. A negative relationship was observed between pH and DIR. Besides, potential methane production was inhibited by the addition of ferrihydrite. These findings provide insight into the connection between iron and carbon input and emission.

A state of art review on the graphene and carbon nanotube reinforced nanocomposites: A molecular dynamics approach

In the present time, need of high-performance composites have been increased greatly due to their high-performance mechanical, electrical and electronic properties, low weight, reduced cost. Presently, composites are used in various industries such as aerospace, automobiles, space, defence, sports and medicals. Various properties of the composites such as strength, stiffness, fatigue, thermal conductivity, glass transition temperature, thermal stiffness, corrosion and wear resistance may be improved by reinforcing the materials which have superior properties than the composite base material. In this context, graphene (Gr) and carbon nanotube (CNT) are the two different forms of carbon which have exceptional mechanical and electrical electronics properties. Both Gr and CNT are known to have superior electrical conductivity, tensile strength and excellent molecular arrangement. In last couple of decades numerous researchers from different research areas have tried to exploit the exceptional properties of Gr and CNT by reinforcing them into different base materials such as polymer, metals glass etc. to improve their mechanical, thermal and electrical properties. In the present work, the authors have attempted to present a state of art literature review on the reinforcement of Gr and CNT into different materials such as polymer, ceramics & metals using the molecular dynamics and investigated the different properties such as strength, stiffness, fatigue, thermal conductivity, glass transition temperature, thermal stiffness, corrosion and wear resistance.

Spatial variation in major water quality types and its relationships with land cover in the middle and lower reaches of Aral Sea Basin

Water resources and environmental issues in the Aral Sea Basin of Central Asia are global concerns. In this study, the water quality variables (i.e., basic physical and chemical attributes, different forms of nutrients, other elements, cations, and anions) from 21 sampling sites in the middle and lower reaches of Aral Sea Basin were measured in 2019 to explore water environmental variations and their causes. Spatial variation in 20 water quality variables was investigated, and the representative water quality types, spatial differences, and their causes were identified via multivariate analysis methods (i.e., principal component analysis and cluster analysis). Furthermore, the effects of land cover on the spatial variation in water quality types were explored. The results showed that: 1) the values of electronic conductivity (EC) and total dissolved solids (TDS) increased from the middle to the lower reaches, and the highest values were in the Aral Sea. This indicates that the concentrations of anions and cations increased from the middle to the lower reaches. For the nutrient variables, high phosphorous concentrations were in the middle reaches of Amu Darya, and high nitrate-nitrogen concentrations were in the Syr Darya. For the different forms of carbon, the highest concentrations were in the Amu Darya, particularly in the delta area of lower reaches. 2) The water quality at all sampling sites can be divided into three water quality types according to the similarity classification of water quality variables. The first type had low concentrations for most water quality variables, which were distributed in the middle reaches of Syr Darya and the Aral Sea. The second type had high concentrations of different forms of nitrogen and phosphorus, which were distributed in the middle and lower reaches of Amu Darya. The third type had high concentrations of carbon, anions, and cations, which were distributed in the Aral Sea. The water quality concentrations of the first and second types were mainly due to rock weathering processes on bare land, and the anions and cations were mainly derived from the weathering of silicates and evaporites. The concentrations of the third type were mainly due to the evaporation and crystallization processes of a dry climate, and the anions and cations were mainly derived from the weathering of silicates and evaporites, which may also be affected by carbonate weathering. 3) With an increase in the buffer zone radius for each sampling point (0.5 km to 10 km), the significant land cover changed from bare land to water, shrubland, grassland, mixed farmland, and vegetation for the first water quality type; the most significant land cover was water. There were no significant relationships between the second water quality type and land cover. For the third water quality type, the significant land cover changed from water to water, mixed farmland, and vegetation - the most significant land cover was water. Therefore, spatial variation in the water quality variables was mainly affected by the local climate conditions (i.e., climatic drought and intensive evapotranspiration) and the mainland cover types (i.e., bare land, water, farmland, grassland, and urban). To improve the water environmental conditions in the middle and lower reaches of Aral Sea Basin, stream flow should be increased to recharge the Aral Sea and weaken the evaporation and crystallization processes in the lower reaches of Aral Sea. Vegetation restoration and a return of farmland to forest and grassland should also be strengthened in the riparian zone, particularly in the middle and lower reaches of Amu Darya and Syr Darya and the Aral Sea.

High Voltage Carbon‐Based Cathodes for Non‐Aqueous Aluminium‐Ion Batteries**

AbstractFour different forms of carbon: activated carbon (AC) from human hair, AC from hemp fibers, a carbon fullerene extract consisting of C60 and C70 fullerene (CFEx) and Super‐P carbon black were tested and compared as cathodes for non‐aqueous aluminium‐ion batteries (AIBs). These materials differ in their general structure, porosity and morphology. Fullerenes display a crystalline structure, whereas hemp fibers, Super‐P and hair are amorphous in nature. Of all materials, AC obtained from hair recorded the highest specific capacity after 50 cycles at 103 mAh g−1 with a Coulombic efficiency of ∼90 % at a current rate of 50 mA g−1. Both hemp fibers and Super‐P achieved their highest specific capacities at 56 mAh g−1 and 84 mAh g−1 respectively. CFEx recorded its highest capacity at 78 mAh g−1 and maintained it for 50 cycles. The cells were charged and discharged to 2.45 V and 0.2 V respectively.

ZrB2[sbnd]SiCw composites with different carbonaceous additives

Various carbonaceous phases have different impacts on the qualifications of ZrB2-SiCw based ceramics. In this research, 5 wt% of different forms of carbon, namely carbon nanoparticles, carbon fibers, graphite, and graphene, were added to ZrB2-25 vol% SiCw composites sintered by spark plasma under 40 MPa at 1900 °C external pressure for 7 min. All samples approached their theoretical density regardless of the addition of carbon and its morphology. The microstructural and XRD evaluations revealed the in-situ synthesis of ZrC and B4C phases in carbon-doped specimens. The addition of carbonaceous reinforcements resulted in refined microstructure, as the finest texture was related to the sample doped with graphene. The highest Vickers hardness (21.9 GPa) was measured for the ceramic having no carbonaceous additive, while the lowest hardness (17.3 GPa) belonged to the composite doped with carbon nanoparticles. In contrary, adding carbon nanoparticles increased the fracture toughness, yielding an outstanding value of 7.1 MPa.m1/2.

Microwave Plasma Formation of Nanographene and Graphitic Carbon Black

Aerosol formation of novel carbons offers potential for scale and purity unmatched by condensed phase processes. A microwave driven plasma drives decarbonization of methane to form solid carbon as an aerosol. Dependent upon gas mixture, different forms of carbon are produced: 2D nanographene and a 3D graphitic carbon black analogue. TEM reveals the morphological differences and nanostructure. The ability to tune the dominant form is demonstrated by control of the CH4/Ar ratio. TGA plots reveal the change in products with feed gas composition and quality by oxidation temperature shift. Corresponding Raman analysis illustrates control of graphene content and lamellae quality by peak ratios. To test the origins of the graphitic particles and nanographene, a commercial carbon black was seeded into the microwave reactor, demonstrating a path for graphitic nanostructure evolution and confirming the molecular growth origins for the nanographene.

Full Spectrum Raman Excitation Mapping Spectroscopy

A generalization of the Raman scattering (RS) spectrum, the Raman excitation map (REM) is a hyperspectral two-dimensional (2D) data set encoding vibrational spectra, electronic spectra and their coupling. Despite the great potential of REM for optical sensing and characterization with remarkable sensitivity and selectivity, the difficulty of obtaining maps and the length of time required to acquire them has been practically limiting. Here we show, with a simple setup using current optical equipment, that maps can be obtained much more rapidly than before (~ms to ~100 s now vs. ~1000 s to hours before) over a broad excitation range (here ~100 nm is demonstrated, with larger ranges straightforward to obtain), thus taking better advantage of scattering resonance. We obtain maps from different forms of carbon: graphite, graphene, purified single walled carbon nanotubes (SWCNTs) and chirality enriched SWCNTs. The relative speed and simplicity of the technique make REM a practical and sensitive tool for chemical analysis and materials characterization.