Exchangeable Cations Research Articles

Gliricidia intercropping supports soil organic matter stabilization at Makoka Research Station, Malawi

Intercropping agriculture with legume trees is a promising strategy to improve soils with low soil organic matter (SOM) and nitrogen (N) contents, which is a common problem in many Southern African regions. Objective of this research was to explore long-term effects of legume-intercropping on SOM pools and soil fertility. We examined a maize-based cropping system with gliricidia (Gliricidia sepium) as intercropping legume tree on a Ferric Lixisol in Southern Malawi. The experimental trial at Makoka Research Station was in its 29th year of management with leaf biomass incorporated into the soil regularly. We determined concentrations of organic carbon (C) and N, exchangeable cations, and available phosphorus (P) of topsoil samples (0–20 cm). We used density fractionation of SOM to gain fractions that roughly approximate SOM pools with fast turnover (not associated to soil minerals), intermediate turnover (occluded within soil aggregates) and slow turnover (mineral associated SOM). We further determined water dispersible clay (WDC) and pedogenic oxides, as these are often involved in the C-stabilization process in tropical soils. Maize-gliricidia intercropping plots showed higher soil pH-values, and higher concentrations of exchangeable Mg and Ca than plots with maize monoculture. In addition, significantly higher contents of C (17.3 vs. 7.03 g kg−1) and N (1.51 vs. 0.7 g kg−1) were found at intercropping plots indicating a C-sequestration rate of 0.3 g C kg−1 a−1, while monoculture induced the loss of SOM with a rate of −0.1 g C kg−1 a−1. C and N contents doubled in pools with fast and with slow turnover and increased by >300% in SOM pool where C and N is bound in soil aggregates. Concomitantly, WDC was significantly lower in intercropping plots than in monoculture plots. Our data emphasize the fast turnover of SOM in subtropical soils and indicate that SOM in arable soils decreases continuously without suitable C-input strategy. Maize-gliricidia intercropping had positive effects on biomass production and C-input at Makoka Research Station and improved soil fertility. In addition, aggregate formation was enhanced and storage of SOM within aggregates and at mineral surfaces increased. Our results indicate a great potential of maize-gliricidia intercropping for improved C management in subtropical Lixisols. Intensive monitoring seems to be promising to validate and quantify the impacts of this measure.

Boosting methylene blue adsorption capacity of an industrial waste-based geopolymer by depositing graphitic carbon nitride onto its surface: Towards sustainable materials for wastewater treatment

Surface characteristics of a geopolymer (GP) from an industrial waste, red mud (RM), and metakaolin (MK), were tuned by depositing urea-derived graphitic carbon nitride (g-C3N4) onto its surface. Methylene blue (MB) adsorption measurements demonstrated that the resulting g-C3N4/RM-MK-GP offers an excellent MB uptake capacity of 170.9 mg g−1, much higher than those of either the GP or the g-C3N4. Kinetics measurements revealed that chemisorption has an important effect on adsorption. The regenerability of g-C3N4/RM-MK-GP was studied for up to four consecutive cycles. Differences between the adsorption capacities of g-C3N4 and g-C3N4/RM-MK-GP were investigated by combining the power of various characterization tools. Results pointed out that surface functional groups associated with g-C3N4, surface hydroxyl and silanol groups of RM-MK-GP, together with exchangeable charge balancing cations of geopolymeric framework provide a unique structure for g-C3N4/RM-MK-GP. This study presents a versatile route to produce a sustainable, efficient, and cheap adsorbent for wastewater treatment.

Intraspecific variation in fruit production of African mahogany (Khaya anthotheca) in a semi‐deciduous East African rainforest

AbstractRestoring valuable timber trees is a necessary part of regaining many ecosystem services and products provided by degraded tropical forests. However, knowledge of seed production, a regeneration prerequisite, is limited for many tropical timber tree species. We studied the fruit production of African mahogany (Khaya anthotheca) in a semi‐deciduous rainforest in East Africa, to provide information for ecological restoration programs. First, we quantified population variability and synchrony in fruit production. Then, we assessed how reproductive status and output were influenced by tree size, neighbourhood crowding, exchangeable cations, liana presence, and crown exposure. We found fruit production at the population level was weakly synchronised, with high interannual variability at the population and individual levels. Tree size determined reproductive status. Individual quantity of fruit produced increased with tree size but decreased with neighbourhood crowding. Our results indicate that K. anthotheca does not meet the criteria for mast fruiting. Our findings suggest that reproductive output in mahogany is regulated by tree size and competition. In addition to active protection, thinning to reduce competition around seed trees may boost fruit production at the individual tree level to provide seed for forest enrichment.

Revitalizing the Biochemical Soil Properties of Degraded Coastal Soil Using Prosopis juliflora Biochar.

Biochar is an effective soil amendment with capabilities of boosting carbon sequestration and enhancing soil fertility, thus enhancing plant growth and productivity. While numerous studies have documented the positive effects of biochar on improving soil properties, a number of studies have reported conflicting results. Therefore, the current study was conducted to evaluate the impact of Prosopis juliflora biochar (0, 2.5, 5.0, and 7.5 t ha-1) on soil biochemical properties in Coastal Kenya to ascertain biochar's potential for soil fertility improvement. A randomized complete block design was used for setting up the experiment with three replicates, while Casuarina equisetifolia L. was planted as the test crop. Soil sampling for nutrient analysis was conducted quarterly for 12 months to assess nutrient dynamics under different biochar rates in the current study. Compared to soil untreated with Prosopis juliflora biochar, the results showed that there was a significant increase in soil pH by 21% following biochar utilization at the rate of 7.5 t ha-1. Total nitrogen was increased by 32% after the biochar application, whereas the total organic carbon was increased by four folds in comparison to biochar-untreated soil. Available phosphorus was increased by 264% following biochar application in comparison to the control treatment. In addition, the application of biochar resulted in an increment in the soil exchangeable cations (Ca2+, K+, Mg2+) across the assessment periods. Soil cation exchange capacity (CEC), bacteria and fungi were enhanced by 95, 33 and 48%, respectively, following biochar application at 7.5 t ha-1 in comparison to untreated soil. In conclusion, these results strongly suggest improvement of soil biochemical properties following Prosopis juliflora biochar application, thus providing potential for soil fertility improvement in regions such as the one in the study.

Synthesis of a novel polysiloxane as an inhibitor in water-based drilling fluids and an assessment of the inhibition mechanism

In oil and gas well engineering, shale wellbore stability poses significant challenges. Developing shale inhibitors with high inhibition and resistance to elevated temperatures is crucial to address wellbore stability in deep wells. In this study, an amphoteric polysiloxane known as SC-POTD was synthesized as a heat-resistant shale inhibitor for water-based drilling fluid. The inhibition properties were evaluated using linear swelling, rolling recovery, and rheological tests, and the results were compared with the properties of potassium chloride and commercial polyamines. Various analysis methods were conducted to understand the interaction mechanism between the clay particles and polymer molecules, including X-ray diffraction test, Zeta potential determination, particle size analysis, contact angle measurement, and scanning electron microscope observation. SC-POTD with an amphoteric structure can effectively adsorb on the clay surface through electrostatic force, compressing the electric double layer of clay and forming a hydrophobic layer. Furthermore, SC-POTD can embed in the crystal interlayer, exchange cations and discharge interlayer water, effectively inhibiting hydration. With the flexibility of the Si-O backbone and the small steric hindrance of methyl side groups, SC-POTD may have a better affinity with bentonite containing siloxane tetrahedrons, and cooperate with the quaternary ammonium group to enhance clay interlayer interaction. In addition, the temperature resistance of SC-POTD can be improved by the siloxane backbone with larger bond energy. The results indicated that modified polysiloxane may find a promising application as heat-resistant drilling fluid additives.

The nutritional status and root development of silver fir (Abies alba Mill.) seedlings growing on decaying deadwood in temperate forest ecosystem

The study aimed to compare two substrates, soil and deadwood, for the regeneration of silver fir (Abies alba Mill.) seedlings. Three-year-old fir seedlings growing both on deadwood and in the soil were collected. The examination involved determining the physical, chemical, and biochemical properties of soil and deadwood, as well as assessing the morphology of the roots and the nutrition of seedlings growing on the soil and deadwood. The examined substrates differed in physical, chemical and biochemical properties. It was shown that strongly decomposed fir logs are a good substrate for the growth of fir seedlings, mainly due to the high content of exchangeable cations (especially calcium, magnesium and potassium) and high phosphorus and nitrogen content. The type of substrate had a significant impact on the root morphology of fir seedlings. In our study, the most responsive root traits to differences in growing substrates were specific root area (SRA) and specific root length (SRL). Our analyses did not confirm significant differences in the stoichiometry of C, N and P in the roots and needles of seedlings grown on different substrates. The stoichiometry of roots and needles suggests no limitations in the uptake of nutrients by seedlings growing on deadwood. This study validated that heavily decomposed wood can provide favourable microhabitats for the growth of the young generation of fir.

Biochar Functions in Soil Depending on Feedstock and Pyrolyzation Properties with Particular Emphasis on Biological Properties

Biochar effects are strongly dependent on its properties. Biochar improves physical soil properties by decreasing bulk density and increasing medium and large aggregates, leading to faster and deeper water infiltration and root growth. Improvement of the chemical properties of soil is connected with pH neutralization of acidic soils, increase of cation exchange capacity and base saturation, providing a larger surface for sorption of toxicants and exchange of cations. Biochar increases the stocks of macro- and micronutrients in soil and remains sufficient for decades. Biochar effects on (micro)biological properties are mainly indirect, based on the improvements of habitat conditions for organisms, deeper root growth providing available C for larger soil volume, higher crop yield leading to more residues on and in the topsoil, better and deeper soil moisture, supply of all nutrients, and better aeration. Along with positive, negative effects of biochar while used as a soil conditioner are discussed in the review: presence of PAH, excessive amounts of K, Ca and Mg, declination of soil pH. In conclusion, despite the removal of C from the biological cycle by feedstock pyrolysis, the subsequent application of biochar into soil increases fertility and improves physical and chemical properties for root and microbial growth is a good amendment for low fertility soils. Proper use of biochar leads not only to an increase in crop yield but also to effective sequestration of carbon in the soil, which is important to consider when economically assessing its production. Further research should be aimed at assessing and developing methods for increasing the sequestration potential of biochar as fertilizer.

Thermally Induced Domain Migration and Interfacial Restructuring in Cation Exchanged ZnS-Cu1.8S Heterostructured Nanorods.

Partial cation exchange reactions can be used to rationally design and synthesize heterostructured nanoparticles that are useful targets for applications in photocatalysis, nanophotonics, thermoelectrics, and medicine. Such reactions introduce intraparticle frameworks that define the spatial arrangements of different materials within a heterostructured nanoparticle, as well as the orientations and locations of their interfaces. Here, we show that upon heating to temperatures relevant to their synthesis and applications, the ZnS regions and Cu1.8S/ZnS interfaces of heterostructured ZnS-Cu1.8S nanorods migrate and restructure. We first use partial cation exchange reactions to synthesize a library of seven distinct samples containing various patches, bands, and tips of ZnS embedded within Cu1.8S nanorods. Upon annealing in solution or in air, ex situ TEM analysis shows evidence that the ZnS domains migrate in different ways, depending upon their sizes and locations. Using differential scanning calorimetry, we correlate the threshold temperature for ZnS migration to the superionic transition temperature of Cu1.8S, which facilitates rapid diffusion throughout the nanorods. We then use in situ thermal TEM to study the evolution of individual ZnS-Cu1.8S nanorods upon heating. We find that ZnS domain migration occurs through a ripening process that minimizes small patches with higher-energy interfaces in favor of larger bands and tips having lower-energy interfaces, as well as through restructuring of higher-energy Cu1.8S/ZnS interfaces. Notably, Cu1.8S nanorods containing multiple patches of ZnS thermally transform into ZnS-Cu1.8S heterostructured nanorods having ZnS tips and/or central bands, which provides mechanistic insights into how these commonly observed products form during synthesis.

Assessing the impact of anthropogenic influences on the sediment quality of Owalla Reservoir, Southwest, Nigeria

The study aims to investigate the impact of anthropogenic influences within the catchment areas on the sediment physico-chemical quality of Owalla Reservoir in Osun State, Nigeria with the primary aim of creating baseline information on the aspect of limnology. Twenty sampling stations were established along the reservoir representing, its three different sections and two zones. The sampling was conducted for a period of two years to cover both seasons of the year in the area. The sediment samples were collected using a Van-Veen grab of 0.04 m2 area (0.2m × 0.2m) from the waterbed at each sampling locations; labelled, kept in cooler at 4°C and transported to the laboratory for the analysis. The reservoir sediment was mainly clayey-sand in texture, while the particle size distribution was in this order: sand (73.1%) > clay (17.4%) > silt (9.4%). The exchangeable cations order of dominance was in this order: Mg2+ > Ca2+ > H+ > Al3+ > K+ >Na+ and anions in this order: PO34- > SO42- > NO3-> Cl-. The highest mean values for water depth, transparency, air temperature, water temperature and sediment temperature (5.28 ± 0.40 m, 1.60 ± 0.05 m, 31.90 ± 0.29°C, 30.6 ± 0.18°C and 27.6 ± 0.23°C) were recorded during the dry season compared with the rainy season. The results obtained from this study, shows that Owalla Reservoir is fairly clean and not contaminated with toxic pollutants. The sediment pH is within acidic range, and enriched with nutrients due to the anthropogenic activities around this reservoir catchment areas. However, if the organic enrichments and siltation in this reservoir is not controlled, it could lead to the future eutrophication of this waterbody, which can cause water quality degradation, alter the aquatic biota and natural ageing process of this reservoir making it unsuitable for its purposes.

Diagnostic and Therapeutic Strategies to Severe Hyponatremia in the Intensive Care Unit.

Hyponatremia is the most common electrolyte abnormality encountered in critically ill patients and is linked to heightened morbidity, mortality, and healthcare resource utilization. However, its causal role in these poor outcomes and the impact of treatment remain unclear. Plasma sodium is the main determinant of plasma tonicity; consequently, hyponatremia commonly indicates hypotonicity but can also occur in conjunction with isotonicity and hypertonicity. Plasma sodium is a function of total body exchangeable sodium and potassium and total body water. Hypotonic hyponatremia arises when total body water is proportionally greater than the sum of total body exchangeable cations, that is, electrolyte-free water excess; the latter is the result of increased intake or decreased (kidney) excretion. Hypotonic hyponatremia leads to water movement into brain cells resulting in cerebral edema. Brain cells adapt by eliminating solutes, a process that is largely completed by 48 h. Clinical manifestations of hyponatremia depend on its biochemical severity and duration. Symptoms of hyponatremia are more pronounced with acute hyponatremia where brain adaptation is incomplete while they are less prominent in chronic hyponatremia. The authors recommend a physiological approach to determine if hyponatremia is hypotonic, if it is mediated by arginine vasopressin, and if arginine vasopressin secretion is physiologically appropriate. The treatment of hyponatremia depends on the presence and severity of symptoms. Brain herniation is a concern when severe symptoms are present, and current guidelines recommend immediate treatment with hypertonic saline. In the absence of significant symptoms, the concern is neurologic sequelae resulting from rapid correction of hyponatremia which is usually the result of a large water diuresis. Some studies have found desmopressin useful to effectively curtail the water diuresis responsible for rapid correction.

Investigation into the Chemical Characteristics of Soils near Sinkholes Situated in Anambra State, Nigeria

In this comprehensive study, we delve into the chemical properties of soil in the proximity of sinkholes located in Anambra state of Nigeria. Three distinct sinkhole sites were selected for examination: Awka site 1 (6.2232°N and 7.0824°E), Awka site 2 (6.2220°N and 7.0819°E), and Agulu (6.0941°N and 7.0203°E). For a comprehensive analysis, 24 soil samples were meticulously collected and subjected to thorough analysis. These samples comprised of 15 specimens obtained from the immediate vicinity of the sinkholes, while 9 samples were procured from locations situated at least 2 kilometers away from the sinkhole sites. The study focused on investigating various parameters, namely pH levels, Organic Carbon (OC) content, Organic Matter (OM) content, Aluminum (Al) levels, Hydrogen (H) levels, Total Nitrogen (TN) content, Magnesium (Mg) levels, Potassium (K) levels, Sodium (Na) levels, Calcium (Ca) levels, Effective Cation Exchange Capacity (ECEC), Base Saturation, and soil texture. The obtained results revealed that the study areas predominantly exhibited a sandy composition with a notably low clay content. Furthermore, the analysis indicated low hydrogen values, while sodium levels were observed to be relatively high. Consequently, certain areas, particularly those situated farther away from the sinkhole site, exhibited a reduced amount of exchangeable bases and effective cation exchange capacity. This phenomenon potentially resulted in leaching and dispersion within the soil, leading to inadequate water infiltration and subsequent run-off. Notably, this process may have contributed to the formation of tunnel erosion, ultimately resulting in the emergence of sinkholes.

Experimental investigation on infiltration behavior of sodium ion in compacted bentonite

Because of its high swelling capacity and low hydraulic conductivity, bentonite has been selected as the candidate buffer material in deep geological disposal project for handling high-level radioactive waste. In Japan, seawater infiltration is an important issue in the evaluation of buffer material, as disposal facilities are under discussion for siting in coastal areas [1]. Sodium ion, which is the main ion in seawater, has profound effects on the properties of bentonite, such as hydraulic conductivity and swelling behaviours etc. [2][3]. These changes may be closely related to the infiltration behavior of sodium ion in bentonite. T In this study, for observing the infiltration behavior of sodium ion in compacted bentonite, infiltration tests were conducted on compacted bentonite specimens with thickness of 2 mm, where the specimens were wetted by NaCl solutions with a concentration range of 0 to 1 mol/L. In the testing program, wetting time, specimen dry densities and initial water contents were varied to investigate their effects on sodium ion infiltration. After the infiltration test, final water contents of specimens were measured and leached cations were obtained using benzyltrimethylammonium chloride (BTM) method [4].
 Figure 1 shows the results of leached cations and final water content of specimens with 1.5g/cm3 initial dry density for different wetting time. It is found that under the 0.1mol/L NaCl solution case, there is almost no sodium ion infiltration in compacted bentonite with a dry density of 1.5g/cm3 as shown in Figure 1(a). For the case of 0.5mol/L and 1mol/L NaCl solution, the leached sodium cation from specimens increases with the increase of concentration of supplied NaCl solution under the same wetting time. For other exchangeable cations (i.e., Mg+, Ca2+ and K+), there is no appreciable difference among the varieties of NaCl solutions and wetting time. For the final water content measurement results, it is found from Figure 1(b) that the water content increasing speeds in 0.5mol/L and 1mol/L NaCl solutions are significantly faster than that in 0.1mol/L NaCl solution.

From Coupling Second-Order Stresses to Understanding and Predicting the Structural Response of a Dioctahedral Smectite

AbstractThe employment of clay minerals in the transport of water, nutrients, and contaminants depends on a few factors, including permeability, hydration behavior, ion-exchange efficiency, and more. With the application of external stress, it is still difficult to understand how clay particles swell and collapse, how water is retained, how hydration heterogeneities are formed within crystallites, and how interlamellar space is organized. The present work studied the link between geochemical, thermal, kinetic constraints (established at the laboratory scale), and intrinsic clay features by exchanging Na-rich montmorillonite (SWy2) with Ni2+, Mg2+, or Zn2+ cations. By comparing the experimental 00l reflections with the calculated reflections obtained from the structural models, quantitative X-ray diffraction (XRD) analysis has enabled the building of a theoretical profile describing the layer stacking mode (LSM) and allowed the description of interlayer space (IS) configuration along the c* axis. Regardless of the type of the exchangeable cations (EC), XRD modeling revealed that all samples exhibited interstratified hydration behavior within the crystallite size, which probably indicates partial or incomplete saturation of the IS. This theoretical result was defined by the appearance of two hydration states (1W and 2W), which were unrelated to the strain strength creating a higher degree of structural heterogeneity. Using the theoretical decomposition of the observed XRD patterns, the identification of all distinct layer populations and their stacking mode was achieved. The segregated LSM are, therefore, obviously superior as a function of stress strength.

In Ukrainian

The adsorption and direct calorimetric studies of the binary exchange of Ca2+ and Sr2+ cations on the Na-form of low-silica type natural clinoptilolite (Sokyrnytsya, Ukraine) were performed. The ion exchange of Ca2+ and Sr2+ cations on the Na-form of natural clinoptilolite was studied under static conditions at a solid to liquid phase ratio of 1 : 100 and a constant ionic strength of the solution of 0.1. The integral heats of ion exchange for these systems were measured using a highly sensitive Tian-Calve microcalorimeter in a special lab-made cell. Also, the ion exchange isotherms and Kielland curves were plotted, and the corrected selectivity coefficients and ion exchange constants were calculated. Changes in the integrated Gibbs free energies, enthalpies, and entropies of the ion exchange of Ca2+ and Sr2+ cations on the Na-form of clinoptilolite were calculated in entire range of the substitutions of the exchange complex. The thermodynamic parameters of incomplete ion exchange were analyzed in terms of the crystal structure of the zeolite. In addition, the state of exchangeable cations in the channels of clinoptilolite was described in detail. It is shown that structural heterogeneities of cation-substituted forms of clinoptilolite are clearly reflected in the dependence of thermodynamic functions on the degree of exchange, and significant differences are observed between the exchange of Ca2+ and Sr2+ cations that could not be described by standard thermodynamic values. Although the isotherms of ion exchange have a convex shape, the Na-form of clinoptilolite does not show any thermodynamic affinity to Ca2+ cations. This ion exchange reaction is accompanied by positive enthalpy changes in all range of substitutions of the exchange complex. At the same time, thermodynamic selectivity toward Sr2+ cations was observed for 40 % of the zeolite exchange centers, and the exchange is accompanied by minor exothermic effects in the range of small substitutions, and the ion exchange isotherm has σ-like form. In general, the thermodynamic affinity of the Na-form of clinoptilolite to the studied metal ions under conditions of incomplete exchange is ordered as following hydration energy trends in the case of the lyotropic properties among alkaline earth metals. Thus, the experimental thermodynamic characteristics of ion exchange equilibria could be a reliable support for the practical using of natural clinoptilolite.

Effects of the age of raised beds on the physicochemical characteristics of fruit orchard soil in the Vietnamese Mekong Delta.

To grow fruit plants, farmers in the Vietnamese Mekong Delta (VMD) must use raised bed constructions to avoid waterlogging during the rainy season. This study aimed to evaluate the effects of the age of the raised beds on the soil physicochemical properties of longan orchards located in the VMD. Two raised bed systems were evaluated: a young bed constructed 10 years ago and an old bed constructed 42 years ago. Soil samples were collected from five different soil layers (0-20, 20-40, 40-60, 60-80, and 80-100 cm) with four replicates per layer. Soil samples were tested for pH, electrical conductivity (EC), available phosphorus (AP), total nitrogen (TN), soil organic matter (SOM), exchangeable cations (Ca2+, K+, Mg2+, and Na+), cation exchange capacity (CEC), bulk density (BD), soil porosity, available water-holding capacity (AWC), particle composition (sand, silt, and clay), and size. The soil pH was approximately 1.0 units lower in the old bed compared to the young bed at depths of 0-20 and 20-40 cm. The BD was higher in the old bed (0.15 g cm-3) than in the young bed at a soil depth of 0.4 m. SOM, AP, exchangeable cations (Ca2+, Na+, and Mg2+), AWC, and soil porosity were significantly lower in both the topsoil (0-20 cm) and subsoil (20-40 cm) layers in the old bed than in the young bed. In particular, the SOM, AP, AWC, and soil porosity contents in the old bed decreased by 18%, 20%, 15%, and 17%, respectively, compared with those in the young bed at soil depths of 0-40 cm. Therefore, cultivating raised bed soil for a longer period significantly reduced the soil exchangeable cations, porosity, and fertility of the surface and subsurface soils. Based on these results, farmers should use soil conservation practices, such as cover crops, rice straw mulching, and soil amendments in their orchards to mitigate topsoil degradation.

The effective monitoring of eleven crucial parameters that describe the condition of cultivated Haplic Luvisol soils using fourier-transformed near-infrared spectroscopy

The study aimed to develop a cost-effective and rapid approach for monitoring eleven crucial parameters that describe the health of cultivated Haplic Luvisol soils. To achieve this, the diffuse reflectance spectra in the NIR spectral region, between 1100 and 2500 nm, were registered, and partial least-squares (PLS) models to predict the concentrations of the critical parameters, including organic carbon, total nitrogen, the available soil nutrients (phosphorus, potassium and magnesium), the exchangeable cations (calcium, magnesium and potassium), the pH levels (determined in deionized water or KCl solution and hydrolytic acidity), were built. The validation results, which are expressed as RMSE and R2val that were obtained for validation the samples, demonstrate that the proposed approach is a reliable and efficient way to monitor the health of Haplic Luvisol soils. Specifically, excellent predictions were obtained for the total nitrogen, organic carbon and pH, which was determined in KCl solution with R2val values equal to 0.9696, 0.9573 and 0.9176, respectively. Additionally, very good PLS models were constructed to estimate the pH levels determined in deionized water, exchangeable magnesium, and potassium, which achieved R2val values of 0.8650, 0.8383, and 0.8329, respectively. For the remaining parameters, the corresponding R2val values were above 0.7294.

Extreme Monovalent Ion Selectivity Via Capacitive Ion Exchange

Capacitive deionization (CDI) is an emerging technology applied to brackish water desalination and ion selective separations. A typical CDI cell consists of two microporous carbon electrodes, where ions are stored in charged micropore via electrosorption into electric double layers. For typical feed waters containing mixtures of several cations and anions, some of which are polluting, models are needed to guide cell design for a target separation, given the complex electrosorption dynamics of each species. An emerging application for CDI is brackish water treatment for direct agricultural use, for which it is often important to selectively electrosorb monovalent Na+ cations over divalent Ca2+ and Mg2+ cations. Recently, it was demonstrated that utilizing constant-voltage CDI cell charging with sulfonated cathodes and short charging times enabled monovalent-selective separations. Here, we utilize a one-dimensional transient CDI model for a flow-through electrode CDI cell to elucidate the mechanisms enabling such separations. We report the discovery that an asymmetric CDI cell with a chemically functionalized cathode induces electric charges in the pristine anode at 0 V cell voltage, which has important implications for monovalent cation selectivity. Leveraging our mechanistic understanding, with our model we uncover a novel operational regime we term “capacitive ion exchange”, where the concentration of one ion species increases while competing species concentration decreases. This regime enables resin-less exchange of monovalent cations for divalent cations, with chemical-free electrical regeneration.

Low-density polyethylene microplastics alter chemical properties and microbial communities in agricultural soil

Microplastic (MP) pollution in agricultural soils, resulting from the use of plastic mulch, compost, and sewage sludge, jeopardizes the soil microbial populations. However, the effects of MPs on soil chemical properties and microbial communities remain largely unknown. Here, we investigated the effects of different concentration levels (0, 0.1, 1, 3, 5, and 7%; w:w) of low-density polyethylene (LDPE) MPs on the chemical properties and bacterial communities of agricultural soil in an incubation study. The addition of LDPE MPs did not drastically change soil pH (ranging from 8.22 to 8.42). Electrical conductivity increased significantly when the LDPE MP concentrations were between 1 and 7%, whereas the total exchangeable cations (Na+, K+, Mg2+, and Ca2+) decreased significantly at higher LDPE MP concentrations (3–7%). The highest available phosphorus content (2.13 mg kg−1) was observed in 0.1% LDPE MP. Bacterial richness (Chao1 and Ace indices) was the lowest at 0.1% LDPE MP, and diversity indices (Shannon and Invsimpson) were higher at 0 and 1% LDPE MP than at other concentrations. The effect of LDPE MP concentrations on bacterial phyla remained unchanged, but the bacterial abundance varied. The relative abundance of Proteobacteria (25.8–33.0%) was the highest in all treatments. The abundance of Acidobacteria (15.8–17.2%) was also high, particularly in the 0, 0.1, and 1% LDPE MPs. With the increase in LDPE MP concentration, the abundance of Actinobacteria gradually increased from 7.80 to 31.8%. Our findings suggest that different MP concentration levels considerably alter soil chemical properties and microbial composition, which may potentially change the ecological functions of soil ecosystems.

Affected of Ameliorated Alkaline Water and Soil Amendments on Exchangeable Cation, Macro and Micronutrients in Sodic Soil under Drip Irrigation

The Field experiment was carried out at Anbil Dharmalingam Agricultural College and Research Institute, Tiruchirappalli using cotton (RCH- 20) as a test crop to examine the effect of ameliorated alkali water and soil amendments on soil properties, growth, and yield of hybrid cotton in sodic soil under drip irrigation. In this experiment, Drip irrigation with gypsum treatment water and drip irrigation with spent wash treatment water were used as main-plots treatments. Soil application of gypsum @ 50 % GR (5.2 t ha-1) and one time soil application of distillery spent wash @ 5 lakh litter ha-1 were imposed as sub-plot treatments. The treatment without amendments both under main plot and sub plots were used as control. The experiment was carried out using a strip-plot design with four replications. The application of additives through irrigation water (or) soil considerably decreased the pH of post-harvest soil. The soil exchangeable Ca and Mg were found significant due to soil application of amendments only and value ranged from 8.51 to 9.35 and 5.03 to 5.20 Cmol (p+) kg -1 respectively. The soil available nutrients N, P and K were found significant, and value range from 167 to 311, 15.4 to 21.5, 158 to 928 kg ha-1 respectively. The application distillery spent wash (DSW) and gypsum slightly increased the micronutrient cations range which from 4.80 to 6.85 mg kg-1 of Fe, 8.60 to 10.43 mg kg-1 of Mn, 0.64 to 0.88 of mg kg-1 of Zn, 1.10 to 1.42 mg kg-1 of Cu. The results of the field experiment revealed that application of amended alkali water and amended soil significantly increased all the growth and yield parameters of cotton. An increase in seed cotton yield of 701 and 544 kg ha-1 was recorded due to the application of gypsum treated water and DSW treated water respectively over control. Similarly, an increase of 773 and 973 kg ha-1 of seed cotton yield was recorded due to soil application of gypsum and DSW respectively over control. While considering the interaction effect, soil application of DSW along with gypsum bed treated water found to be the best for getting higher seed cotton yield (3015 kg ha-1) when compared to other treatment combination.

Investigation of the structural and electrical conductivity properties in pure and cation exchanged rectorite

Clay minerals, as biofriendly and low-cost materials, are highly essential for the modern industrial applications including the production of clean energy, its storage and conversion. Here, the capabilities of pure and cation exchanged rectorite, a regularly interstratified phyllosilicate from Beatrix Mine (South Africa) were explored and discussed. A comprehensive characterization was performed by means of high resolution solid-state NMR, electrochemical impedance spectroscopy and powder X-ray diffraction. 23Na MAS and 3QMAS NMR spectroscopy was used to characterize accessibility of interlayer space in rectorite for exchangeable cations. Three Na sites attributed to easily exchangeable Na+ on the surface or in large pores, Na+ in dehydrated micaceous interlayers and Na+ in hydrated smectite interlayers were identified. Differences in hydration states in smectitic interlayers depending on the type of intercalation were detected using 1H MAS NMR. A higher amount of hydrating water molecules in pure and Mg-exchanged rectorites was attributed to the higher hydration energy of Ca2+ and Mg2+. The temperature dependences of electrical conductivity in this work were best described using the empirical Vogel-Tammann-Fulcher equation with the temperature-dependent effective activation energy parameter. Significantly stronger change of activation energy in Mg2+ exchanged rectorite in the temperature range of 10 °C to 50 °C as compared to pure rectorite and its Na+, Li+ and NH4+ modifications was related to an extensive H-bond network in the interlayers, which facilitated an effective proton transfer responsible for electric conductivity. The obtained resutls suggested a greater potential for the use of Mg-exchanged rectorite as ionic conductor at enhanced temperatures.