Carbon Depletion Research Articles

Modelling spatial and temporal soil organic carbon dynamics under climate and land management change scenarios, northern Ethiopia

AbstractSoil organic carbon (SOC) depletion is a threat for the present and future agricultural production in Ethiopia. Hence, investigation of the influence of land management and climate change on SOC is required to facilitate climate change mitigation practices. For this study, croplands of the Atsela‐Sesat and Ayba sites from the Alaje district and the Tsigea site from the Raya Azebo district in northern Ethiopia were selected. The RothC model was used to predict future SOC trends and evaluate impacts of climate and land‐management change scenarios on SOC stocks. The RothC model was run for two scenarios, (i) business as usual (scenario 1) and (ii) improved crop residue and manure management (scenario 2), to predict SOC stock changes in the cropland under current and future climate change. The current SOC content and SOC stock of the croplands are 14.4 g kg−1 and 26.7 t ha−1 in Atsela‐Sesat, 14.8 g kg−1 and 27.9 t ha−1 in Ayba and 14.8 g kg−1 and 26.9 t ha−1 in Tsigea, respectively. The RothC model‐predicted SOC accumulation for this century in scenario 1 was 0.26 t C ha−1 in Alaje and 0.18 t C ha−1 in Raya Azebo, whereas in scenario 2 it was 0.52 t C ha−1 in Alaje and 0.36 t C ha−1 in Raya Azebo. Although the predicted SOC accumulation in scenario 2 is higher than in scenario 1 and the baseline scenario, it still has a decreasing trend due to climate change. However, the organic carbon return into the soil is generally small and thus it will not be possible to improve soil productivity and attain food security. Therefore, future soil fertility strategies need to include both organic and inorganic fertilizer application. These findings will help to assist land managers to make informed decisions during land‐management practices to mitigate the impacts of climate change.Highlights Land management and climate changes influence cropland SOC stocks in northern Ethiopia RothC model predicts future SOC trends and dynamics Appropriate land management increased SOC accumulation and reduced impacts of climate change Findings help to assist land managers to make informed decisions to mitigate climate change impacts

Eta carinae and the homunculus: far infrared/submillimetre spectral lines detected with the Herschel Space Observatory

ABSTRACT The evolved massive binary star η Carinae underwent eruptive mass-loss events that formed the complex bi-polar ‘Homunculus’ nebula harbouring tens of solar masses of unusually nitrogen-rich gas and dust. Despite expectations for the presence of a significant molecular component to the gas, detections have been observationally challenged by limited access to the far-infrared and the intense thermal continuum. A spectral survey of the atomic and rotational molecular transitions was carried out with the Herschel Space Observatory, revealing a rich spectrum of broad emission lines originating in the ejecta. Velocity profiles of selected PACS lines correlate well with known substructures: H i in the central core; NH and weak [C ii] within the Homunculus; and [N ii] emissions in fast-moving structures external to the Homunculus. We have identified transitions from [O i], H i, and 18 separate light C- and O-bearing molecules including CO, CH, CH+, and OH, and a wide set of N-bearing molecules: NH, NH+, N2H+, NH2, NH3, HCN, HNC, CN, and N2H+. Half of these are new detections unprecedented for any early-type massive star environment. A very low ratio [12C/13C] ≤ 4 is estimated from five molecules and their isotopologues. We demonstrate that non-LTE effects due to the strong continuum are significant. Abundance patterns are consistent with line formation in regions of carbon and oxygen depletions with nitrogen enhancements, reflecting an evolved state of the erupting star with efficient transport of CNO-processed material to the outer layers. The results offer many opportunities for further observational and theoretical investigations of the molecular chemistry under extreme physical and chemical conditions around massive stars in their final stages of evolution.

Efficacy of chemical factors on production and extraction of biodiesel by microalgae

Environmental concerning factors responsible for carbon dioxide emissions and depletion of petroleum based fuel are the driving factors for the search of alternative fuels like biodiesel. The growth of microalgal cells and their metabolic activity toward lipid production could be controlled by the nutrient factors employed in production media. The lipid accumulation ability of the microalgal strains could be influenced by the deprivation of vital chemicals like carbon, nitrogen, calcium and magnesium. In the part of commercializing microalgal based biodiesel, cost effective measures in oil extraction and downstream processes have to be considered. Huge varieties of microalgal cellular pretreatment methods are employed to enhance cellular disintegration so as to facilitate oil extraction by structural modification of carbohydrates present in cell wall. The diversified methods used for microalgal pretreatment encompass chemical, thermal, biological, mechanical or combinatorial approaches. Among all the pretreatment methods chemical methods are greatly advantageous while concerning the feasibility in energy and time consumption. Combinatorial approaches like thermochemical pretreatment or microwave assisted extraction methods are very successful in terms of feasible energy production under limited time consumption. Above all, genetic engineered microbes which could be able to withstand suitable pretreatment methods were developed. This present review tried to explore the activity of chemical parameters and also delineate the nutrient deprivation factors involving in the cellular metabolism of microalgal biomass for lipid production.

Fuel-cladding chemical interaction of a prototype annular U-10Zr fuel with Fe-12Cr ferritic/martensitic HT-9 cladding

As an alternative fuel form, the annular metallic fuel design eliminates the liquid sodium bond between the fuel and the cladding, providing back-end fuel cycle and other benefits. The fuel-cladding chemical interaction (FCCI) of annular fuel also presents new features. Here, state-of-the-art electron microscopy and spectroscopy techniques were used to study the FCCI of a prototype annular U-10wt%Zr (U-10Zr) fuel with ferritic/martensitic HT-9 cladding irradiated to 3.3% fission per initial heavy atom. Compared with sodium-bonded solid fuels, negligible amounts of lanthanides were found in the FCCI layer in the investigated helium-bonded annular fuel. Instead, most lanthanides were retained in the newly formed UZr2 phase in the fuel center region. The interdiffusion of iron and uranium resulted in tetragonal (U,Zr)6Fe phase (space group I4/mcm) and cubic (U,Zr)(Fe,Cr)2 phase (space group Fd3¯m). The (U,Zr)(Fe,Cr)2phase contains a high density of voids and intergranular uranium monocarbides of NaCl-type crystal structure (space group Fm3¯m). At the interdiffusion zone and inner cladding interface, a porous lamellar structure composed of alternating Cr-rich layers and U-rich layers was observed. Next to the lamellar region, the unexpected phase transformation from body-centered cubic ferrite (α-Fe) to tetragonal binary Fe-Cr σ phase (space group P42/mnm) occurred, and tetragonal Fe-Cr-U-Si phase (space group I4/mmm) was identified. Due to the diffusion of carbon into the interdiffusion zone, carbon depletion inside the HT-9 led to the disappearance of the martensite lath structure, and intergranular U-rich carbides formed as a result of the diffusion of uranium into the cladding. These detailed new findings reveal the unique features of the FCCI behavior of annular U-Zr fuels, which could be a promising alternative fuel form for high burnup fast reactor applications.

Optimising the strength-ductility-toughness combination in ultra-high strength quenching and partitioning steels by tailoring martensite matrix and retained austenite

Undesirable fracture resistance has led to critical safety concerns in ultra-high strength quenching and partitioning (Q&P) steels. The present work proposes a new heat treatment method of tailoring simultaneously martensite matrix and retained austenite to enhance the fracture resistance of ultra-high strength Q&P steels, while keeping the good strength-ductility combination. To this end, both conventional and pre-cracked tensile tests are conducted on different Q&P steels with various microstructures consisting of different martensite matrix and retained austenite. Microstructure is analysed by neutron diffraction, atom probe tomography, transmission electron microscopy and dilatometry. For the optimum microstructure, the volume fraction of retained austenite play an important role in enhancing the strength-ductility combination, with an ultimate tensile strength reaching 1500 MPa and uniform elongation over 10%. In addition, the dislocation mobility in the martensite matrix of the optimum microstructure is enhanced due to the dislocation recovery, solute carbon depletion, and the transformation of transition carbides into cementite. The enhanced dislocation mobility reduces the flow stress and results in an improvement of intrinsic toughness of the martensite matrix. Furthermore, the size of cementite at grain boundaries of the optimum microstructure is so small (tens of nanometres) that brittle intergranular fracture is prevented. In summary, the new heat treatment method suggests that the optimal treatment should tailor simultaneously the martensite matrix and the retained austenite to optimise the strength, ductility and fracture resistance combination of ultra-high strength Q&P steels.

Assessing the potential of soil cyanobacteria for simultaneous wastewater treatment and carbohydrate-enriched biomass production

In this study, a mixed nitrogen-fixing soil cyanobacterial culture was tested to treat municipal wastewater and produce total carbohydrates in a one-stage operation. Four photobioreactors were operated in semi-continuous mode for 30 days, evaluating the effect of different hydraulic retention times and nutrients and carbon loads on nutrients and organic matter removal, biomass composition, and carbohydrate production. One photobioreactor operated at a hydraulic retention time of 10 d with diluted 2:1 wastewater with distilled water, and other photobioreactors worked at 10 d, 8 d, and 6 d of hydraulic retention times with undiluted sewage. The results evidenced that high hydraulic retention time and low nutrients load achieved the highest removal efficiencies in total nitrogen >95%, total phosphorus 35–78%, total organic carbon >93%, and total inorganic carbon >82%. These high removals led to nitrogen limitation that stimulated a continuous carbohydrate accumulation of up to 48%. Also, a biomass production of 0.05–0.07 mg L−1 d−1 dominated by easy-settling flocs of filamentous nitrogen-fixing cyanobacteria was achieved. Otherwise, lower hydraulic retention time and thus high nutrients load promoted carbon depletion, which led to lower nitrogen and phosphorus removals, low biomass production and contamination of green algae species. The results of this study highlight the nutritional and operational mechanisms of soil microorganisms and strategies to simultaneously clean waste streams and produce valuable by-products.

The influence of carbide formation in ferrite on the bainitic type transformation

The effect of carbide formation on the development of the bainitic type transformation was studied using phase field modeling. The phase field model incorporated the displacive structural transformation producing a misfitting product phase, long range elastic interactions, carbon partitioning from austenite and ferrite and the formation of carbides in ferrite modelled as carbon sinks. The results of the simulations performed for the systems with different carbide nucleation sequences demonstrate that initially, due to a slow nucleation of carbides and fast carbon partitioning, carbon diffusion to austenite was the dominant process leading to the decrease in the transformation rate. However, after some period of time, the effect of carbon depletion in the solid solution by carbides became more significant, which led to the reduction of the average concentration of carbon in the whole system and the acceleration of the structural transformation. The rate of carbide nucleation and the number of nucleated carbides controlled both the transformation rate and the period of time before the transformation acceleration.

External α-carbonic anhydrase and solute carrier 4 are required for bicarbonate uptake in a freshwater angiosperm.

The freshwater monocot Ottelia alismoides is the only known species to operate three CO2-concentrating mechanisms (CCMs): constitutive bicarbonate (HCO3-) use, C4 photosynthesis, and facultative Crassulacean acid metabolism, but the mechanism of HCO3- use is unknown. We found that the inhibitor of an anion exchange protein, 4,4'-diisothio-cyanatostilbene-2,2'-disulfonate (DIDS), prevented HCO3- use but also had a small effect on CO2 uptake. An inhibitor of external carbonic anhydrase (CA), acetazolamide (AZ), reduced the affinity for CO2 uptake but also prevented HCO3- use via an effect on the anion exchange protein. Analysis of mRNA transcripts identified a homologue of solute carrier 4 (SLC4) responsible for HCO3- transport, likely to be the target of DIDS, and a periplasmic α-carbonic anhydrase 1 (α-CA1). A model to quantify the contribution of the three different pathways involved in inorganic carbon uptake showed that passive CO2 diffusion dominates inorganic carbon uptake at high CO2 concentrations. However, as CO2 concentrations fall, two other pathways become predominant: conversion of HCO3- to CO2 at the plasmalemma by α-CA1 and transport of HCO3- across the plasmalemma by SLC4. These mechanisms allow access to a much larger proportion of the inorganic carbon pool and continued photosynthesis during periods of strong carbon depletion in productive ecosystems.

Precipitation Versus Partitioning Kinetics during the Quenching of Low-Carbon Martensitic Steels

Low-carbon, low-alloy steels undergo auto-tempering and carbon partitioning to austenite during quenching to martensite. The microstructures of two such steels quenched at two cooling rates have been evaluated using electron microscopy to characterise lath and carbide precipitate morphologies, and the results have been compared with theoretical predictions based on the Thermo-Calc modules DICTRA and TC-Prisma. The modelling tools predicted the carbon depletion rates due to diffusion from the bcc martensite laths into austenite and the precipitation of cementite in the ferrite matrix. The predictions showed a satisfactory agreement with the metallographic results, indicating that the Thermo-Calc based software can aid in the design of new low-carbon martensitic steels.

Tailoring dielectric properties of PDCs-SiCN with bimodal pore-structure by annealing combined with oxidation

This paper developed a novel strategy, i.e., annealing combined with oxidation to realize high εr′ (> 7.5) and low tanδ (< 0.2) in PDC-SiCN. The as-pyrolyzed SiCN prepared by powder consolidation was an amorphous ceramic composed of Si-C-N matrix and free carbon with a bimodal pore-structure. Dielectric properties and pore size distributions can be adjusted by annealing. Oxidation of materials featured an oxide scale on the surface and non-uniform erosion of phases in which additional loss of free carbon occurred. Dielectric properties and their response to oxidation were different under various annealing temperature. When annealing temperature reached 1500℃, sharp rise in εr′, εr′′ and tanδ with increasing temperature happened due to enhanced polarization and electrical conduction. Oxidation at 600℃lowered the εr′′ since depletion of free carbon broke the percolating conducting path. εr′ maintained at a high level because SiC and most of the heterogeneous interface contributed to εr′ were preserved.

Magnesium Oxychloride Cement Composites with Silica Filler and Coal Fly Ash Admixture.

Worldwide, Portland cement-based materials are the most commonly used construction materials. As the Portland cement industry negatively affects the environment due to the excessive emission of carbon dioxide and depletion of natural resources, new alternative materials are being searched. Therefore, the goal of the paper was to design and develop eco-friendly, low-cost, and sustainable magnesium oxychloride cement (MOC)-based building material with a low carbon footprint, which is characterized by reduced porosity, high mechanical resistance, and durability in terms of water damage. To make new material eco-efficient and functional, silica sand which was used in the composition of the control composite mixture was partially replaced with coal fly ash (FA), a byproduct of coal combustion. The chemical and mineralogical composition, morphology, and particle morphology of FA were characterized. For silica sand, FA, and MgO, specific density, loose bulk density, and particle size distribution were measured. Additionally, Blaine specific surface was for FA and MgO powder assessed. The workability of fresh mixtures was characterized by spread diameter. For the hardened MOC composites, basic structural, mechanical, hygric, and thermal properties were measured. Moreover, the phase composition of precipitated MOC phases and their thermal stability were investigated for MOC-FA pastes. The use of FA led to the great decrease in porosity and pore size compared to the control material with silica sand as only filler which was in agreement with the workability of fresh composite mixtures. The compressive strength increased with the replacement of silica sand with FA. On the contrary, the flexural strength slightly decreased with silica sand substitution ratio. It clearly proved the assumption of the filler function of FA, whereas its assumed reactivity with MOC cement components was not proven. The water transport and storage were significantly reduced by the use of FA in composites, which greatly improved their resistance against moisture damage. The heat transport and storage parameters were only slightly affected by FA incorporation in composite mixtures.

Influence of Niobium Content on the Mechanical Properties and Abrasion Wear Resistance of Heat-Treated High-Chromium Cast Iron

The effect of niobium addition up to 3.4 wt% on the microstructure and mechanical properties of heat-treated high-Cr cast iron containing 13.5 wt% Cr was investigated. Niobium addition caused small hard NbC particles to precipitate within the proeutectic austenite which impede the development of austenite dendrite growth resulting in structure refinement. This austenitic matrix upon heat treatment changed to mainly martensitic one with some retained austenite and reinforced with small amounts of secondary carbides of M7C3 type. It was found that the hardness increased with increasing Nb content due to structure refinement and precipitation of hard NbC particles. These particles caused a depletion of carbon in the austenite matrix and thus most of the austenite was transformed to martensite upon heat treatment. The highest impact value was obtained for the base alloy without Nb addition which could be attributed to the high amount of retained austenite. The high-Cr cast iron alloyed with Nb in the range of 1.55–3.4 wt% showed an increase in hardness without any deterioration in toughness. The wear resistance was significantly enhanced by the presence of hard NbC particles up to 2.52 wt% Nb. Exceeding this optimum amount of addition leads to agglomeration of NbC particles and hence deterioration of the wear resistance through three body abrasion wear mechanism.

Genomewide Stabilization of mRNA during a "Feast-to-Famine" Growth Transition in Escherichia coli.

Bacteria have to continuously adjust to nutrient fluctuations from favorable to less-favorable conditions and in response to carbon starvation. The glucose-acetate transition followed by carbon starvation is representative of such carbon fluctuations observed in Escherichia coli in many environments. Regulation of gene expression through fine-tuning of mRNA pools constitutes one of the regulation levels required for such a metabolic adaptation. It results from both mRNA transcription and degradation controls. However, the contribution of transcript stability regulation in gene expression is poorly characterized. Using combined transcriptome and mRNA decay analyses, we investigated (i) how transcript stability changes in E. coli during the glucose-acetate-starvation transition and (ii) if these changes contribute to gene expression changes. Our work highlights that transcript stability increases with carbon depletion. Most of the stabilization occurs at the glucose-acetate transition when glucose is exhausted, and then stabilized mRNAs remain stable during acetate consumption and carbon starvation. Meanwhile, expression of most genes is downregulated and we observed three times less gene expression upregulation. Using control analysis theory on 375 genes, we show that most of gene expression regulation is driven by changes in transcription. Although mRNA stabilization is not the controlling phenomenon, it contributes to the emphasis or attenuation of transcriptional regulation. Moreover, upregulation of 18 genes (33% of our studied upregulated set) is governed mainly by transcript stabilization. Because these genes are associated with responses to nutrient changes and stress, this underscores a potentially important role of posttranscriptional regulation in bacterial responses to nutrient starvation.IMPORTANCE The ability to rapidly respond to changing nutrients is crucial for E. coli to survive in many environments, including the gut. Reorganization of gene expression is the first step used by bacteria to adjust their metabolism accordingly. It involves fine-tuning of both transcription (transcriptional regulation) and mRNA stability (posttranscriptional regulation). While the forms of transcriptional regulation have been extensively studied, the role of mRNA stability during a metabolic switch is poorly understood. Investigating E. coli genomewide transcriptome and mRNA stability during metabolic transitions representative of the carbon source fluctuations in many environments, we have documented the role of mRNA stability in the response to nutrient changes. mRNAs are globally stabilized during carbon depletion. For a few genes, this leads directly to expression upregulation. As these genes are regulators of stress responses and metabolism, our work sheds new light on the likely importance of posttranscriptional regulations in response to environmental stress.

PECVD of Hexamethyldisiloxane Coatings Using Extremely Asymmetric Capacitive RF Discharge.

An extremely asymmetric low-pressure discharge was used to study the composition of thin films prepared by PECVD using HMDSO as a precursor. The metallic chamber was grounded, while the powered electrode was connected to an RF generator. The ratio between the surface area of the powered and grounded electrode was about 0.03. Plasma and thin films were characterised by optical spectroscopy and XPS depth profiling, respectively. Dense luminous plasma expanded about 1 cm from the powered electrode while a visually uniform diffusing plasma of low luminosity occupied the entire volume of the discharge chamber. Experiments were performed at HMDSO partial pressure of 10 Pa and various oxygen partial pressures. At low discharge power and small oxygen concentration, a rather uniform film was deposited at different treatment times up to a minute. In these conditions, the film composition depended on both parameters. At high powers and oxygen partial pressures, the films exhibited rather unusual behaviour since the depletion of carbon was observed at prolonged deposition times. The results were explained by spontaneous changing of plasma parameters, which was in turn explained by the formation of dust in the gas phase and corresponding interaction of plasma radicals with dust particles.

Fuel-Cladding Chemical Interaction of a Prototype Annular U-10Zr Fuel with Fe-12Cr Ferritic/Martensitic Cladding

As an alternative fuel form, annular metallic fuel design eliminated the liquid sodium bond between the fuel and the cladding, providing back-end fuel cycle and other benefits. The fuel-cladding chemical interaction (FCCI) of annular fuel also presents new features. Here, state-of-the-art electron microscopy and spectroscopy techniques were used to study the FCCI of a prototype annular U-10wt%Zr (U-10Zr) fuel with ferritic/martensitic HT-9 cladding irradiated to 3.3% fission per initial heavy atom (FIMA). Compared to sodium-bonded solid fuels, negligible amounts of lanthanides were found in the FCCI layer in the investigated helium bonded annular fuel. Instead, most of the lanthanides were retained in the newly formed UZr2 phase at the fuel center region. The interdiffusion of iron and uranium resulted in tetragonal (U,Zr)6Fe phase (space group I4/mcm) and cubic (U,Mo)(Fe,Cr)2 phase (space group Fd3 m). The (U,Mo)(Fe,Cr)2 phase contains a high density of voids and intergranular uranium monocarbides of NaCl-type crystal structure (space group Fm3 m). At the interface of the interdiffusion zone and inner cladding, a porous lamellar structure composed of alternating Cr-rich layers and U-rich layers was observed. Next to the lamellar region, the unexpected phase transformation from body centered cubic (BCC) ferrite (α-Fe) to tetragonal binary Fe-Cr σ phase (space group P42/mnm) occurred and tetragonal Fe-Cr-U-Si phase (space group I4/mmm) was identified. Due to the diffusion of carbon into the interdiffusion zone, carbon depletion inside the HT-9 led to the disappearance of the martensite lath structure, and intergranular U-rich carbides formed as a result of the diffusion of uranium into the cladding. These detailed new findings reveal the unique features of the FCCI behavior of annular U-Zr fuels, which could be a promising alternative fuel form for high burnup fast reactor applications.

A generalized kinetic model for electro-assisted catalytic wet air oxidation of triclosan on Ni@NiO/graphite electrode

Electro-assisted catalytic wet air oxidation (ECWAO) is an efficient technique for wastewater treatment under ambient condition. In this work, the mineralization kinetics of triclosan (TCS) in an ECWAO process with Ni@NiO/graphite-felt (GF) electrode is studied. The TCS mineralization follows a pseudo-first order kinetics in the ECWAO process. A general kinetic model, based on the depletion of total organic carbon (TOC) as a lumped parameter, is developed. Such a kinetic model suggests the optimized ECWAO operating conditions of initial concentration of TOC at 40 mg L−1, applied current at 25 mA, and temperature at 308 K. In addition, the ECWAO is also effective for the treatment of biosphenol A (BPA) and sulfamethoxazole (SMX). Under the optimal conditions, TCS, BPA and SMX are mineralized by 92.9 ± 1.5, 90.8 ± 1.7 and 90.6 ± 1.0% within 120 min, with specific energy consumptions (SECs) of 2.2 ± 0.3, 1.4 ± 0.5, and 2.8 ± 0.6 kW h kg-TOC−1, respectively.

Depletion of soil carbon and aggregation after strong warming of a subarctic Andosol under forest and grassland cover

Abstract. The net loss of soil organic carbon (SOC) from terrestrial ecosystems is a likely consequence of global warming and may affect key soil functions. The strongest changes in temperature are expected to occur at high northern latitudes, with forest and tundra as prevailing land cover types. However, specific soil responses to warming in different ecosystems are currently understudied. In this study, we used a natural geothermal soil warming gradient (0–17.5 ∘C warming intensity) in an Icelandic spruce forest on Andosol to assess changes in the SOC content between 0 and 10 cm (topsoil) and between 20 and 30 cm (subsoil) after 10 years of soil warming. Five different SOC fractions were isolated, and their redistribution and the amount of stable aggregates were assessed to link SOC to changes in the soil structure. The results were compared to an adjacent, previously investigated warmed grassland. Soil warming depleted the SOC content in the forest soil by −2.7 g kg−1 ∘C−1 (−3.6 % ∘C−1) in the topsoil and −1.6 g kg−1 ∘C−1 (−4.5 % ∘C−1) in the subsoil. The distribution of SOC in different fractions was significantly altered, with particulate organic matter and SOC in sand and stable aggregates being relatively depleted and SOC attached to silt and clay being relatively enriched in warmed soils. The major reason for this shift was aggregate breakdown: the topsoil aggregate mass proportion was reduced from 60.7±2.2 % in the unwarmed reference to 28.9±4.6 % in the most warmed soil. Across both depths, the loss of one unit of SOC caused a depletion of 4.5 units of aggregated soil, which strongly affected the bulk density (an R2 value of 0.91 and p&lt;0.001 when correlated with SOC, and an R2 value of 0.51 and p&lt;0.001 when correlated with soil mass in stable aggregates). The proportion of water-extractable carbon increased with decreasing aggregation, which might indicate an indirect protective effect of aggregates larger than 63 µm on SOC. Topsoil changes in the total SOC content and fraction distribution were more pronounced in the forest than in the adjacent warmed grassland soils, due to higher and more labile initial SOC. However, no ecosystem effect was observed on the warming response of the subsoil SOC content and fraction distribution. Thus, whole profile differences across ecosystems might be small. Changes in the soil structure upon warming should be studied more deeply and taken into consideration when interpreting or modelling biotic responses to warming.

Optimal placement of electric vehicle charging station for unbalanced radial distribution systems

ABSTRACTTransportation is one of the dominant applications where abundant fossil fuel usage can be experienced across the world. To save the earth from carbon emission and depletion of conventional energy resources, alternate energy sources are to be introduced in transportation which will lead to Electric Vehicles (EV) and Hybrid Electric Vehicles (HEV). The infrastructure of the power system is also adaptable to the changes of electrified transportation. In this research work, a methodology is proposed to find the optimal placement of Electric Vehicle Charging Station (EVCS) along with the optimal capacity of charging stations for Unbalanced Radial Distribution System (URDS) by using Particle Swarm Optimization (PSO). This paper also explains the effect of EVCS placement in RDS w.r.t voltage profile and real power losses. Also, the insertion of EVCS to the power system draws additional power from the electrical grid. To make the system more self-sustainable and reliable, this research work proposes additional distributed generators (DGs) at optimal locations to reduce the impact of EVCS on the system by incorporating it. The proposed methodology is validated with two standard unbalanced IEEE test cases such as IEEE 19 bus and IEEE 25 bus URDS.

Silicon Dynamics During 2 Million Years of Soil Development in a Coastal Dune Chronosequence Under a Mediterranean Climate

Silicon (Si) in plants confers a number of benefits, including resistance to herbivores and water or nutrient stress. However, the dynamics of Si during long-term ecosystem development remain poorly documented, especially the changes in soils in terms of plant availability. We studied a 2-million-year soil chronosequence to examine how long-term changes in soil properties influence soil Si pools. The chronosequence exhibits extreme mineralogical changes—from carbonate-rich to quartz-rich soils—where a carbonate weathering domain is succeeded by a silicate weathering domain. Plant-available Si concentrations were lowest in young soils (Holocene, < 6.5 ka), increased in intermediate soils (Middle Pleistocene, 120 ka), and finally decreased toward the oldest, quartz-rich soil (Early Pleistocene, 2 Ma). Silicon availability is likely low and relatively constant in the young soils because (1) carbonate weathering consumes protons and therefore reduces weathering of silicate minerals and (2) Si adsorption by secondary minerals is high in alkaline soils. In the middle-aged sites, Si availability rises with the loss of carbonates and the formation of kaolinite that appears to drive its concentration, and then falls in the oldest sites with quartz enrichment. The increasing accumulation of biogenic silica following carbonate depletion indicates stronger soil–plant Si cycling as ecosystem development proceeds. A literature analysis confirms the shift in processes controlling Si availability between the carbonate and silicate weathering domains. Overall, our results show a nonlinear response of plant-available Si to long-term pedogenesis, with likely important implications for the Si-related functioning of terrestrial ecosystems.

Alteration of local and systemic amino acids metabolism for the inducible defense in tea plant (Camellia sinensis) in response to leaf herbivory by Ectropis oblique

Leaf herbivory on tea plants (Camellia sinensis) by tea geometrids (Ectropis oblique) can cause severe yield loss and quality damage for tea. In previous work, we discovered that leaf herbivory triggered systemic carbon depletion in undamaged roots to enhance resource investment for local defense induced in damaged leaves. Here, we investigated the dynamics of amino acids in the local and systemic responses and the roles of nitrogen resource reallocation for the inducible defense in tea plants in response to leaf herbivory. The comparative analysis of the dynamics of flavonoids, caffeine, theanine and basic amino acids at metabolic and transcriptome levels revealed that leaf herbivory triggered the differential reconfiguration of these amino acid-derived defensive metabolites and nitrogenous primary metabolism between the local and systemic responses. The tight association of the metabolism and reallocation of amino acids with the activation of defensive secondary metabolism indicated that the systemic nitrogen reallocation played a potentially important role for the resource investment in tea plant resistance against leaf herbivory. This study provided an extended understanding of the role of systemic nitrogen reallocation for the interaction of tea plants and geometrids and the root-mediated resource-based resistance strategy employed by tea plants in response to leaf herbivory.