Fraction Of Potassium Research Articles

Solid-to-gas phase transition kinetics of diverse potassium occurrence forms during biomass pellet combustion: Time-resolved detection and multi-step modeling

The solid-to-gas phase transition of potassium during biomass combustion significantly impacts ash-related issues in bioenergy systems, affecting operational efficiency and equipment longevity. However, the specific mechanisms and kinetics of this transition process remain inadequately understood. This work investigates the time-resolved transition of solid-phase potassium to the gas phase during the combustion of rice husk and wheat straw pellets, combining experimental measurements with theoretical modeling. Tunable diode laser absorption spectroscopy (TDLAS) was employed to measure atomic potassium concentrations 15 mm above burning pellets tray, where gas-phase equilibrium is approached. Key combustion characteristics including thermogravimetric profiles, spectral radiation, and temperature were simultaneously monitored. A novel multi-step model was developed to describe the transition of different forms of solid-phase potassium (organic, exchangeable, and inorganic) to the gas phase. This model integrates TDLAS measurements, observed combustion characteristics, and biomass physicochemical properties. Thermodynamic equilibrium calculations were used to estimate the atomic potassium fraction from total gaseous potassium. The results showed that the solid-to-gas phase transition of organic potassium synchronizes with volatiles release. In contrast, the maximum emission rates of inorganic and exchangeable potassium occurred at the onset of char combustion. The developed model agrees well with the online detection experiments and were further validated by offline ICP analysis of residual ash. While not directly simulating gas-solid interface reactions near the particle surface, this work lays groundwork for future multi-scale modeling of particle-laden flows and reactor-scale phenomena in biomass combustion systems.

Effect of Potassium and Zinc on Soil Properties and Fraction of Potassium and Zinc in Soil

A field experiment was carried out on Agronomy Farm, B. A. College of Agriculture, Anand Agricultural University, Anand during rabi season of the year 2020-21. The experiment comprising nine treatment combinations consisted of three levels of potassium (0, 20 and 40 kg/ha) and three levels of zinc (0, 2.5 and 5.0 kg/ha). These treatments were evaluated in Randomized Block Design (factorial) with four replications. The soil of the experimental plot was loamy sand in texture, alkaline in reaction, low in organic carbon and available nitrogen, medium in available phosphorus, potassium and zinc. Results of the experiment revealed that the available K2O in soil was significantly increased due to application of 40 kg K2O/ha (K2) and was found to be at par with application of 20 kg K2O/ha (K1). All other chemical properties of soil (pH, EC, organic carbon, available N, P2O5, S, Fe, Mn, Zn and Cu) were not differ significantly due to application of different levels of potassium. Levels of zinc also failed to produce its significant effect on chemical properties of soil except available Zn in soil as it was significantly increased with the treatment of Z2 (5.0 kg Zn/ha) than control but was found to be at par with treatment Z1 (2.5 kg Zn/ha). Moreover, no any chemical property of soil differ due to the interaction of different levels of potassium and zinc. The water soluble K and exchangeable K fractions in soil significantly increased with the treatment of K2 (40 kg K2O/ha) otherwise non-exchangeable K, total K and different zinc fractions in soil did not differ significantly by the different levels of potassium. Different potassium fractions and total Zn fraction in soil were found to be non-significant under the different zinc levels but all the zinc fractions in soil (water soluble plus exchangeable Zn, carbonate bound Zn, Fe/Mn oxide bound Zn, organically bound Zn and residual Zn) significantly increased with the treatment of Z2 (5.0 kg Zn/ha) and was remained at par with treatment Z1 (2.5 kg Zn/ha). The interaction between potassium and zinc failed to influence significantly on potassium and zinc factions in soil.

Characterization of Peat Water Electrocoagulation Flocs from Sarawak Southern Region

Sarawak located in Borneo is endowed with the vast availability of peat water sources, particularly for the state southern region. Several investigations have shown that electrocoagulation treatment with aluminium electrodes is feasible to treat peat water in which the quality is comparable to the National Water Quality Standard (NWQS). Even though electrocoagulation treatment is feasible to treat peat water, the characteristics of peat water electrocoagulation flocs have not been reported. As such, this study aims to investigate the characteristics of the electrocoagulation flocs from peat water derived from the Sarawak southern region by using batch electrocoagulation treatment. The objectives of this study are to conduct an experimental study analysis of and identify the minerals on the electrocoagulation flocs along with operating energy cost analysis of peat water batch electrocoagulation treatment. Consequently, this study has found that reaction time and current density affect the production of flocs in which the amount of flocs increases with the increasing reaction time and current density. The flocs produced are found to consist of a large fraction of oxygen (O), carbon (C), iron (Fe), and aluminium (Al) along with a small fraction of potassium (K), magnesium (Mg), calcium (Ca) and Silicon (Si). The presence of Al observed in the flocs is due to the aluminium hydroxide generated during the electrocoagulation process. The total operating cost for peat electrocoagulation with a current density of 5A and reaction time of 20 minutes is about RM0.31 per m3. As a result, the electrocoagulation of peat water process is able to treat peat water as well as produce flocs in which earth elements and heavy metals could be recovered.

Impact of conservation agriculture on potassium fractions under maize based cropping systems in a Typic Haplustept

Intensive conventional tillage practice has deteriorated soil quality and decreased potassium (K) availability in soil under maize-based growing areas in Indo-Gangetic Plain of India. Consequently, maize productivity has declined over the years demonstrating the need for sustainable alternatives. A present study was carried out in 2018-2019 in the eleventh year of an on-going long-term experiment initiated in the year 2008 to understand the impact of different tillage practices on K dynamics under maize-based cropping systems in Inceptisols of Indo-Gangetic Plain of India. The experiment was laid out in split plot design with three levels of tillage practice as main plots: permanent raised bed (PB), zero tillage-flat (ZT-flat) and conventional tillage (CT-flat) and in subplots four different cropping systems viz. maize-wheat-mungbean (MWMb), maize-chickpea-sesbania (MCS), maize-mustard-mungbean (MMuMb), and maize-maize-sesbania (MMS). The result showed that the higher content of water-soluble K, exchangeable K, and nonexchangeable K were recorded in PB and ZT-flat tillage and MCS and MWMb as compared to CT tillage practice and cropping systems. Therefore, PB and ZT-flat tillage and MCS as well as MWMb could be better practices over the CT tillage practice and cropping systems for improving K availability in soil.

The Effect of Local Fertilizers, Mineral Fertilizers and Biopreparations on the Agrophysical Properties of the Soil and the Phosphorus and Potassium Fractions in the Cultivation of White Cabbage

In this article, a description of cabbage with a delicious taste, rich in vitamins and biological substances, which is currently grown as a vegetable crop in the Republic of Uzbekistan. White cabbage is consumed fresh and processed throughout the year. It has dietary and therapeutic properties. It is consumed by people with heart disease, obese people, and those who are sick. Its juice is used in the treatment of inflammation of the stomach. and it is stated that it has a good effect on cabbage yield and product quality when it is fed with the method of fertilization Biopreparation 30 l/hа + N-150, Р-150, K-100 in its cultivation.

Role of clay cation exchange capacity, location of charge, and clay mineralogy on potassium availability in Indian Vertisols

Abstract Precise information on the location of charge in clay minerals and their charge density in smectite-dominant soils is rare. The present study was undertaken with three benchmark Vertisols to establish the relationship between the clay cation exchange capacity (CEC), charge density, as well as the location of charge in smectitic soil clay minerals and their relationship with potassium (K) fixation and release. Potassium fractions and their threshold levels in the Vertisols were determined by standard methods. Soils were segregated into silt, total clay and fine clay fractions for X-ray diffraction analysis and fine clay fractions were used to determine the CEC using standard methods. The Hofmann-Klemen effect (HK) and modified Greene-Kelly test was done with the fine clay to determine the CEC of the tetrahedral sheet. Subsequently, the CEC of the octahedral sheet was calculated as the difference between total CEC and the tetrahedral CEC. The results showed that ~60–64% of the total CEC is attributed to the tetrahedral layers. The tetrahedral CEC that is proportional to the tetrahedral charge density was significant and negatively correlated with K release threshold values and all fractions of K. The tetrahedral CEC contributed more toward the K fixation and release than the octahedral CEC. The study shows that the dominant presence of high-charge smectites in the fine clay fractions of these Vertisols contributed to the tetrahedral CEC and consequently to the charge density of these soils, which implied a tendency to fix K easily and release it with greater difficulty compared to soils with low-charge smectites.

Effect of Long-Term Application of Inorganic Fertilizers, Organic Manure, and Lime on Different Forms of Potassium in Soil under Maize-Wheat Cropping System

The field study was undertaken with the major emphasis on potassium fractionation and its contribution in acid alfisol soils as affected by adoption of continuous cropping, fertilization, and manuring under maize-wheat cropping system in same field over 62 years of crop cycles. The experiment consisted of fourteen treatments, replicated thrice times in a randomized block design, out of which nine treatments were selected for the present study. The selected treatments were as follows - control, T2-100% N, T3- FYM, T4-100% NP, T5-100% NPK, T6- 1/2(N+FYM) + P(A-X/2) + K(B-Y/2) (INM), T7-100% NPK + Lime where the lime application in LR once in 4 years, T8-Lime+ FYM+ P(A-X) + K(B-Y), T9-Lime+N. Surface soil (0-15cm) and subsurface soil (16-30 cm) samples were collected after the harvest of wheat in 2017-18 to observe the initial Physico-chemical properties. Different fractions of potassium, viz., water-soluble K, exchangeable K, available K, 1NHNO3K, non-exchangeable K, Lattice K, and Total K were analyzed for the study. There was a significant difference among the different treatments with respect to potassium fractions in 0-15 cm, and 16-30 cm layers. Moreover, K fractions were significantly decreased with increasing depth of soil. Results showed that the percentage contribution of different forms of K with regard to the total K in surface soil and subsurface soil followed as: Lattice K (68.75-78.11%) > Non – Exchangeable K (19.15-25.49%) > Exchangeable K (1.65-2.45%) >Water soluble K (0.18-0.62%). Application of N and P without K caused depletion of soil, water-soluble K, available K, exchangeable K, non-exchangeable K, and lattice K because of continuous omission of potassium content during the all crop growing stages or the simultaneous leaching nature of residual potassium under same field of the experiment. Therefore, the present investigation stresses the vital importance of the inclusion of organic manure and lime in the fertilizer schedule to maintain soil K dynamics over the long run under the maize-wheat cropping system.

Studies on Potassium Fractions in Central and Southern Dry Zones of Coconut Growing Areas of Hassan District of Karnataka, India

The experiment was conducted in an order to get an insight about the potassium (K) fractions in Central and Southern dry zone of coconut growing areas of Hassan district, Karnataka during 2022-23. The soil samples from surface (0-30 cm) and sub-surface (30-60 cm) were collected from the soils of selected coconut gardens of Central and Southern dry zones of Hassan district for the study. Results revealed that the average water soluble K, hot water soluble K, exchangeable K, non-exchangeable K, lattice K and total K in surface soils of coconut gardens of Central dry zone of Hassan district registered was 2.76, 9.25, 54.65, 555.35, 5896.00 and 6509.00 mg kg-1, respectively. Whereas the above potassium fractions in sub-surface soil recorded were 2.67, 7.70, 47.36, 699.66, 7282.00 and 8032.00 mg kg-1, respectively. The various forms of potassium in surface soils of Southern dry zone revealed that water soluble K, hot water-soluble K, exchangeable K, non-exchangeable K, lattice K and total K was 2.87, 8.85, 53.51, 546.61, 5603.00 and 6206.00 mg kg-1, respectively. Whereas the above potassium fractions in sub-surface soil recorded were 2.21, 7.20, 45.21, 709.20, 7431.00 and 8188.00 mg kg-1, respectively. The trend of decrease in water soluble K and exchangeable K from surface to sub-surface layers was noticed in soils of Central and Southern dry zone whereas non-exchangeable K, lattice K and total K exhibited an increasing trend with depth. The contribution of each form of potassium to total potassium was in the order of water soluble < hot water-soluble K< exchangeable < non-exchangeable < lattice K. Knowledge of different forms of potassium in soil together with their distribution has greater relevance in assessing the long-term K supplying power of soil to coconut palm and is important in formulating a sound fertilizer program for a given set of soil.

Effect of Long-term Application of Organic, Inorganic and Integrated Nutrients on Soil Potassium Fractions in a Vertisol of Central India

The present study was conducted at the experimental field of College of Agriculture, Indore during 2018-2019.Soybean (cv. JS-9305), was grown with 80 kg ha-1 seed rate with row to row and plant to plant spacing of 40 cm X 5 cm. Soybean crop was grown as per standard cultural practices. The experiment was conducted with nine treatments viz., T1- unfertilized control, T2- 20 kg N + 13 kg P ha-1, T3- 30 kg N + 20 kg P ha-1, T4- 40 kg N + 26 kg P ha-1, T5- 60 kg N + 35 kg P ha-1, T6- 6 t ha-1 FYM + 20 kg N + 13 kg P, T7- 5 t ha-1 crop residues + 20 kg N + 13 kg P, T8- 6 t ha-1 FYM and T9- 5 t ha-1 crop residues (CR) laid out in a randomized block design (RBD) having three replications. Different K fractions in soil sample viz., water soluble-K, available-K, exchangeable-K, non-exchangeable-K, lattice-K and total-K were determined following standard methods. The mean values were grouped for comparisons and the least significant differences among them were calculated at p<0.05 confidence level using ANOVA statistics. The results of present study revealed that to sustain K status in Vertisol there is a need of K application along with organic manure/crop residue. The application of organics with and without N and P application can sustain the Lattice-K availability in long run under soybean based cropping system of Vertisols. The rate of chemical fertilizer can be reduced up to 50% due to long term application of 6 t ha-1 FYM or 5 t ha-1 crop residues are added to soil.

Experimental and modelling study of the interaction of bentonite with alkaline water

Compacted bentonite is planned to be used as buffer and backfill materials for the containment of radioactive waste in underground repositories. The performance of these barriers depends on the swelling capacity of bentonite upon hydration. Prolonged interaction between bentonite and alkaline fluids from neighbouring concrete structures can impair the swelling capacity due to profound changes in the chemical composition of bentonite. The coupled hydro-chemo-mechanical behaviour of bentonite under such conditions is at present not well understood. This paper presents for the first time a combined experimental and modelling study that addresses this coupled behaviour with the aim of understanding the key mechanisms leading to swelling pressure loss. Two experiments are presented in which compacted Wyoming bentonite was saturated with either clay or cementitious water, leading to different initial swelling capacities. The samples were subsequently subject to a flow of a KOH-rich cementitious water leading to a slow but sustained decrease in swelling pressure in both tests. The main novelty is the application of a recently developed hydro-chemo-mechanical model for bentonite for interpretation of the experiments. The model accounts for the impact of montmorillonite dissolution, cation exchange reactions, and changes in salinity on the swelling capacity of bentonite. The model results show a relatively good agreement with experimental measurements and suggest that the decrease in swelling capacity of bentonite is driven primarily by an increase in potassium fraction in the interlayer water and by montmorillonite dissolution.

Interventions to Improve Potassium Availability in Light Textured Alfisols Supporting FCV Tobacco

Aim: To investigate the effect of soil inversion in conjugation with combined application of SOP with cheaper potassium supplements like tobacco stalk biochar (TS biochar) and barn wood ash (BWA) on potassium fractions in light textured sandy loam soils supporting FCV tobacco.
 Study Design: Split plot design
 Place and Duration of Study: ICAR-CTRI RS, Jeelugumilli, Andhra Pradesh, India.
 Methodology: A field experiment was conducted with two main plots and seven sub-plots which are replicated thrice. The two main plots are consisting of soil inversion practices i.e., (i) soil inversion with MB plough (ii) without soil inversion and seven sub plot treatments viz., one without potassium, two sulphate of potash treatments at the rate of 100 % and 75 % of recommended dose of fertilizer (RDF), two TS Biochar treatments along with SOP and two BWA treatments along with SOP at the rate of 100 % and 75 % RDK each. Soil Samples were collected at 60 DAP to study various potassium fractions in the soil.
 Results: Results indicated that mean water-soluble potassium has been increased from 17.90 mg kg-1 in without soil inversion to 27.61 mg kg-1 in with soil inversion respectively and among the potassium input management practices highest mean water-soluble potassium of 26.60 mg kg-1 was observed in S4 [100% K through SOP + Tobacco Stalk Biochar (1:1)] treated plots which is on par with S2 [100% K through SOP]. An increase in soil mean exchangeable potassium from 40.07 mg kg-1 without soil inversion to 58.79 mg kg-1 with soil inversion was observed and among the potassium input management practices the highest available potassium was observed in S4 [100% K through SOP + Tobacco Stalk Biochar (1:1)] treated plots with a mean value of 60.14 mg kg-1 which was on par with S6 [100% K through SOP + Barn wood ash (1:1)].
 Conclusion: Both soil inversion and potassium input management has improved the water soluble, exhangeable K in soil while no much influence on non-exchangeable and total K were observed.

Potassium fractions in black soil mediated by integrated nutrient management modules under maize-chickpea cropping sequence.

A field experiment was conducted at the Research Farm of the ICAR-Indian Institute of Soil Science, Bhopal (India) to study influence of different integrated nutrient management (INM) modules on soil potassium (K) fractions. The experiment comprised with twelve treatments laid out in randomized block design (RBD) with three replications under maize-chickpea cropping sequence. The treatments included general recommended dose (GRD), soil test crop response (STCR) dose; combinations of inorganic and organic inputs and only organic modules. The soil samples were collected at crop harvest and analyzed for various K fractions viz., water soluble-K, available-K, exchangeable-K, HNO3-K, lattice-K and total-K. The results indicated that potassium fractions were significantly (p = 0.05) affected by different treatments. Different INM modules significantly enhanced significantly K availability in soil. Among various INM modules studied, treatment 11 (application of 20 t ha-1 FYM in maize with 5 t ha-1 FYM every year in chickpea) proved most beneficial for improving the soil K fractions. Findings of this type are important for K fertilizer management during crop production in areas with low soil fertility.

Spatio-Temporal Distributions of the Natural Non-Sea-Salt Aerosol Over the Southern Ocean and Coastal Antarctica and Its Potential Source Regions

More than 40 years of aerosol data including concentrations of particle number and of nine major ions collected over the Southern Ocean and coastal stations have been aggregated and filtered with back trajectories to reduce the risk of influence from adjacent continents. That provided a rich dataset including latitudinal distribution and seasonality of physical and chemical aerosol parameters that allow insights into aerosol sources over the Southern Ocean. These data together with statistics of back trajectory paths of high (75% percentile) and low (25% percentile) concentrations of the studied aerosol parameters were used to identify potential source regions of the respective compounds. For particle number concentrations, MSA, and the non-sea-salt fractions of Ca and potassium the most prominent source regions were found in high DMS-areas close to Antarctica, whereas the potential source regions of NH4 and the non-sea-salt fraction of Mg were located in part further north over the Southern Ocean. These geographical differences would reflect differences in the marine biota.

What Fraction of Potassium in the Earth Does the Borexino Experiment Allow?

What Fraction of Potassium in the Earth Does the Borexino Experiment Allow?

Soil microbiocoenosis in the agricultural environment as a dynamic system: primary results of the assessment of changes

Soil biota is characterized by high structural, taxonomic and functional diversity and determines the leading trends in the process of soil formation, while the microorganisms content in the soil varies widely depending on its chemical composition, humidity, temperature, pH and other properties. On the other hand, the soil microbiome has a significant impact on soil fertility, participating in the conversion of nutrients inaccessible to plants into usable forms. Soil microbiota can promote or inhibit plant growth. The purpose of this work is to conduct a comparative analysis of the leading representatives of the microbiome for soil samples from the territory of the model field of the peasant (farm) economy Tsirulev E.P. (Privolzhsky District of the Samara Region). Soil sampling was carried out in accordance with the methods of sampling and sample preparation for chemical, bacteriological, helminthological analysis. For comparison, 15 samples were taken from the same points of the field in different years 2019 and 2020. Soil suspensions were prepared according to the serial dilution method. Sowing dilutions was carried out on potato-glucose agar. Microorganisms were identified by microscopic method. The test result was calculated separately for fungi and bacteria. The ratio of fungi and bacteria in % to their total number was determined by calculating the number (N) of microorganisms present in the sample. Chemical analysis of soil samples was carried out according to the following parameters: water pH, salt pH, mass fraction of organic matter, mobile potassium and mobile phosphorus, exchangeable calcium and exchangeable magnesium. Laboratory study of soil samples taken on a model field from the territory of a peasant (farm) economy Tsirulev E.P. showed a fairly stable level of water and salt pH values, moderate variability in the content of organic matter, mobile potassium, magnesium and calcium, with a high heterogeneity of the spatial distribution of mobile phosphorus in the soil. Identification of the presence and abundance in soil samples of typical representatives of soil microbiocoenosis (12 broad-spectrum phytopathogens and 2 phytopathogen antagonists) made it possible to detect microorganisms: common in this soil environment in both years of research (causative agents of phomosis, yellow mucous bacteriosis); found for samples of one year in the minimum number of samples, not detected in another year (causative agent of verticillium, gray mold) or significantly increased their presence (causative agents of rhizoctoniosis, anthracnose, cladosporiosis). The presence in a significant proportion of soil samples, from 20 to 5080% of the samples, was noted for a significant group of objects (Alternaria, Fusarium, Aspergillus, Penicillium, Rhisopus), in both years of research, the presence of the phytopathogen antagonist Trichoderma was detected in all samples. The question of the connection between the revealed changes in the composition of the soil microbiome and the species of plants that were cultivated in this field during a given growing season requires additional data to be clarified, which we will do in subsequent years. Nevertheless, the primary data obtained confirm the existing ideas about the lability of soil microbiocoenosis as a dynamic system that changes its state in response to the impact of abiotic (temperature, humidity) and biotic factors.

Tillage, green manuring and crop residue management impacts on crop productivity, potassium use efficiency and potassium fractions under rice-wheat system

The conventional crop production practices including intensive tillage and open field crop residue burning in world’ largest rice-wheat system (RWS) are adversely affecting crop productivity besides deteriorating natural resources and ecosystems’ sustainability. In order to improve system productivity, potassium (K) use efficiency and apparent K balance, adoption of conservation tillage in a RWS with residue management is considered highly effective. We therefore, studied the effect of wheat straw retention and green manure (GM) in rice (main plot treatment), and tillage and rice residue management in subsequent wheat (sub-plot treatments) on crop productivity, K use efficiency and its transformation amongst different fractions of variable solubility. These results revealed that rice straw retention along with GM significantly (p < 0.05) increased the rice yields by ∼5.3–6.7% and wheat yields by ∼10.2–16.9%, compared to the conventional tillage (CT) without GM. Green manuring during the intervening period (CTRW0+GM) significantly increased the rice grain K uptake by ∼36.2% than in plots with no-GM (CTRW0). However, it increased by ∼29.8% under CTRW25+GM, compared with CTRW25-GM treatment. As compared with CTRW0, CTRW0+GM significantly increased the reciprocal internal use efficiency of K of rice by 3.8 kg Mg−1 grain yield (∼29.5%). However, CTRW25+GM increased the RIUEK of rice by 3.3 kg Mg−1 grain yield (∼22.4%), compared with no-GM (CTRW25). Although, apparent K balance was net negative for CTRW25, ZTWR100 treatments, yet there was decreased K mining of 56–262 kg K ha−1 (∼11.9–61.2%) for CTRW25 and ZTWR100 over CTRW0 and ZTWR0. The increased crop yield, K uptake and K use efficiency were significantly related to K enrichment in water soluble K, exchangeable K, non-exchangeable-K, hydrochloric acid extractable-K, lattice-K and total K fractions by ∼1.3, 3.4, 18.6, 11.0 and 34.1%, respectively due to residue retention, compared with no residue. Therefore, conventional tillage with puddled transplanted rice (CTR) with wheat residue and green manure during intervening period (CTRW25+GM), and zero tillage wheat with rice residue retention (ZTWR100) were emerged as highly valuable technological options for mitigating soil degradation effects under intensive RWS for food grains in north-western India.

Isotopic fractionation of chlorine and potassium during chloride sublimation under lunar conditions

The Moon is depleted in volatile elements and compounds, and lunar samples exhibit a wide range of Cl isotopic compositions, which is believed to result from the volatilization of metal chlorides (e.g., NaCl, KCl, and FeCl2). However, the Cl isotopic fractionation behavior during volatilization is not well constrained, particularly for metal chlorides. Furthermore, the effect of metal chloride evaporation on metal isotopes is poorly known. In the present study, we performed NaCl and KCl sublimation experiments to study Cl and K isotopic fractionations at temperatures ranging from 923 K to 1061 K and at pressures of 7×10–5 bar to 1 bar in an N2 atmosphere. The isotope fractionation factors of 37/35Cl(αgas–solid) from NaCl sublimation experiments are 0.9985±0.0002, 0.9958±0.0004, and 0.99807±0.00004 at 1, 10–2, and 7×10–5 bar, respectively. Those of 41/39K(αgas–solid) and 37/35Cl(αgas–solid) from KCl sublimation experiments are 0.99884±0.00004 and 0.9988±0.0003 at 1 bar, 0.9977±0.0002 and 0.9972±0.0003 at 10–2 bar, and 0.9989±0.0002 and 0.9989±0.0001 at 7×10–5 bar, respectively. Chlorine and K isotopes fractionate more at 10–2 bar than at 7×10–5 bar and 1 bar. The saturation index in all the sublimation experiments was >95%, which resulted in near-equilibrium isotopic fractionation at the sublimation interface. Therefore, the isotopic fractionation was controlled by mass transfer processes in the gas and solid phases. The isotopic fractionation at 10–2 bar was controlled by the chemical diffusion of sublimated gas in an N2 atmosphere with almost no convection effect, (i.e., Pe number close to zero), whereas the isotopic fractionation at 1 bar was suppressed by atmospheric convection with a turbulence factor of 0.4±0.1 (i.e., Pe number >1). The extremely high sublimation rate and the very slow diffusion in the sublimating solid at 7×10–5 bar suppressed isotopic fractionations. Based on our experimental results, calculations using Cl/K and Na/K in lunar materials reveal that degassing of KCl contributed very little (<0.2‰) to the K isotopic fractionation (>0.58‰) during lunar magma ocean degassing. The Cl isotopic fractionation factor from lunar samples is similar to our results at 10–2 bar. This similarity of Cl isotope fractionation indicates that there may have been a transient atmosphere above the lunar magma ocean.

Chemical fractionation and bioavailability of potassium as affected by digestate in a degraded Ultisol under maize cultivation

ABSTRACT Application of soil amendment enhances redistribution of potassium (K) forms which affects K availability. Information on the effect of soil amendment on soil K dynamics is vital for management of soil K. The effects of digestate on dynamics of water soluble (WS), exchangeable K (Exch), non-exchangeable (Non-Ex) and mineral (Min) K fractions as well as maize growth and potassium uptake were investigated under a factorial experiment arranged in a completely randomized design of 5 (0, 5, 10, 15, 20 t ha−1 digestate) × 3 (2, 4, 6 weeks after planting (WAP) ×2 (two growth cycles of maize). During incubation experiment, digestate application increased K fractions and altered the order of distribution of K fractions from Min > Exch > non-Ex > WS in the control soil to Min > WS > Non-Ex > Exch in the amended soil. Potassium availability increased with WAP in first cycle but decreased with WAP in second cycle due to crop uptake. Potassium uptake and dry matter yield were better in first cycle relative to second cycle. Complementing digestate with mineral fertilizer would improve K uptake and maize growth.

Ash aerosol particle size distribution, composition, and deposition behavior while co-firing coal and steam-exploded biomass in a 1.5 MWth combustor

Five different blends of Utah bituminous coal and steam-exploded pine (100/0, 75/25, 50/50, 25/75, 0/100 by mass) were fired in a 1.5 MWth combustor. Primary objectives were to understand mineral matter behavior by analyzing aerosol size distribution, aerosol size-segregated composition, ash deposition mass, and ash composition. For particle size <0.1 μm, pure coal had the lowest aerosol concentration and pure biomass showed the highest (higher nucleation of potassium salts), a trend which reversed for particles >0.1 μm. During pure biomass combustion, aerosol particles >15 μm contained higher mass fractions of potassium (+126%), calcium (+132%), and iron (+115%) and lower fractions of aluminum (−49%) and silicon (−29%) than pure coal. Ash deposition mass decreased with increasing biomass blends. Downstream ash deposits contained −3% to 55% higher sodium and potassium than the upstream ash, which highlights the dilution effect of the condensation layer by inertial impaction on the upstream side. Submicron ash load and deposited mass for 30-min and 90-min tests showed R2 values of 0.974 and 0.966, indicating that smaller particles' concentration determines the final mass. The results suggest that plant operators should not face any difficulties while co-firing these blends with respect to ash deposition by fouling.

Gamma-ray spectroscopy for the characterization of uranium contamination in nuclear decommissioning

Decommissioning is the last step in the life cycle of a nuclear facility. After the evacuation of the facility components, the remaining structures such as concrete walls and floors must be surveyed to ensure that no residual contamination remains. It is a costly and time consuming activity, for which CEA develops fast alpha and beta detection methods allowing a full scanning of very large areas (hundreds of thousands of square meters) in legacy uranium enrichment plants. To support these developments, we present here complementary high-resolution gamma-ray spectroscopy analyses of a contaminated area at the gaseous diffusion uranium enrichment facility UDG, currently under decommissioning at Pierrelatte nuclear plant, France. Long measurements are performed with a High-Purity Germanium (HPGe) detector on the contaminated surface, and in a clean area to assess the natural gamma background of the concrete ground. The surface activity of uranium is 16.6 ± 6.0 Bq.cm-2, mainly due to 234U and 238U, most of the uncertainty coming from the non-uniform distribution of the contamination on the ground. This measurements also allowed us estimating the uranium enrichment of the contamination, which amounts to (0.80 ± 0.13) % of 235U mass fraction, consistently with the range of the Low Enrichment Plant where this measure was performed. Eventually, the background spectrum allowed us to determine the mass fractions of natural uranium, thorium and potassium in the concrete ground, which respectively amount to 3.8 ± 0.2. ppmU (i.e. 3.8 mg of uranium per kg of concrete), 7.4 ± 0.7 ppmTh, and (2.6 ± 0.1) %K of potassium.