High Alkalinity Research Articles

Highly alkaline electrokinetic extraction: Characteristics of chromium mobilization, conversion and transport in high alkalinity soil

In site chromium (Cr) contaminated soil characterized by high alkalinity and carbonate content, protons are not effectively targeted for Cr(III) mobilization but rather accelerate the reduction of easily transportable Cr(VI) within the acidification electrokinetic (EK) system. As an alternative, the highly alkaline extraction conditions (HAECs) maintained by anolyte regulation are explored owing to the ability to desorb strong binding Cr(VI) and form anionic Cr(III)-hydroxides (Cr(OH)4−, Cr(OH)52−). The results demonstrate that HAECs were more efficient in mobilizing ions in severe alkalinity and electrical conductivity soil compared to organic acid acidifying extraction conditions (OAECs). Simultaneously, a limited amount of soluble Cr(III) was produced; however, its transportation was hindered and more noticeable in the case of Cr(VI), displaying a distinct retention phase within the intermediate soil chamber. The antagonistic interplay between electromigration and electroosmotic flow was considered the main responsible factor. The conversion intensity of Cr(VI) to Cr(III) was inhibited at HAECs. The promising mobilization and low conversion intensity contributed to total Cr removal. At HAECs, enhanced electromigration and electroosmotic flow combined with a favorable oxidation environment may facilitate in situ delivery of oxidants, offering practical implications for the EK detoxification of high alkalinity site soil contaminated with Cr. The practicability of HAECs is likely to be enhanced when the cost-benefit balance of providing a simultaneous energy supply during site treatment is resolved.

Direct Electrooxidation of Ammonia-Enriched Wastewater Using a Bipolar Membrane-Integrated Electrolytic Cell

The treatment of reject water containing concentrated ammonia and non-biodegradable organics is a challenging task in wastewater treatment plants. To address this problem, we propose a novel process consisting of a selective ammonium-exchange resin and an ammonia electrooxidation reaction (AmER-AOR). Because an alkaline condition is essential for direct ammonia oxidation, the use of a bipolar membrane (BPM) was helpful. Nonetheless, an initial pH of 13 and KOH addition were required to maintain a high alkalinity for the complete elimination of ammonia. The linear sweep voltammogram elucidated the high pH requirement and ammonia oxidation promotion. When the current density varied from 30 to 80 mA cm−2, 60 mA cm−2 showed the highest current efficiency (30.39%) and the lowest specific energy demand (95.3 kWh/kg-N), indicating the most energy-effective condition. Increasing the initial concentration of ammonia from 0.1 M to 0.5 M improved the current efficiency (51.57%), demonstrating an additional energy-effective strategy for the AmER-AOR. The energy efficiency of pure H2 production in the cathodic chamber was 30%. To estimate the viability for practical applications, reject water collected from a local wastewater treatment plant was applied in the AmER-AOR. Notably, no significant difference in the ammonia removal rate was observed with synthetic wastewater. To the best of our knowledge, this is the first study that employs a BPM as a separator and OH− supplier for direct ammonia oxidation. Our findings reveal that the AmER-AOR with a BPM has promising practical applicability in the treatment of reject water and energy production.

Leaching Kinetics of Cu from Low-Grade Oxidized Copper Ore with High Alkalinity Gangue Using Edta·2na Solution

Leaching Kinetics of Cu from Low-Grade Oxidized Copper Ore with High Alkalinity Gangue Using Edta·2na Solution

Screening for alkaliphilic microalgae for carbon capture from ambient air and food production

SummaryThe production of alkaliphilic microalgae can contribute to address the challenging cost of using pure carbon dioxide in large reactors. At high pH values, carbon dioxide is rapidly scavenged and the supply rates of dissolved inorganic carbon from the atmosphere to alkaline media are high. The present study aimed to identify microalgal strains that can cope with high alkalinity and aeration rates. Eight strains were studied and the microalgae Chlorella vulgaris, Scenedesmus almeriensis and Nannochloropsis gaditana were the only ones that were able to grow under these conditions. Their biomass productivities using laboratory‐scale bubble columns with no pH control and high aeration flow were 0.20 ± 0.03, 0.24 ± 0.03 and 0.08 ± 0.01 g·L−1·day−1, respectively. The production of the two former was scaled up to pilot‐scale bubble columns. Overall, the amount of atmospheric carbon dioxide that was transformed into biomass was in the range of 10%–30%, depending on the strain used and the photobioreactor setup. The biomass was rich in proteins and β‐carotene, both valuable products, highlighting the potential production of food ingredients while capturing carbon dioxide from the atmosphere.

Green Fabrication of Superhydrophilic/Underwater Superoleophobic Composite Membrane for High-Efficiency Oil/Water Separation in Harsh Environments.

Due to the high oil spill incidence and industrial wastewater discharge including oil and emulsified oil, designing and synthesizing oil-water separation materials which can maintain stability under harsh environmental conditions with high separation efficiencies remains a great challenge. The present work developed an easy, green, cost-effective, and easily scaled-up approach for fabricating cellulose-based membranes. First, we coated polydopamine (PDA) onto fibers of filter membrane (FM). Then, the PDA-FM membrane was immersed into the mixed solution of poly(vinyl alcohol)/poly(acrylic acid) (PVA/PAA) and further thermally cross-linked at 150 °C to create a superhydrophilic/underwater superoleophobic membrane (PVA/PAA@PDA-FM) to separate oil/water mixtures. The simple thermally cross-linking process promotes multiple covalent chemical bonds generation between cellulose filter membrane, PAA, PDA, and PVA, endowing membranes with excellent stability and resistance to acidity, alkalinity, and salinity. The PVA/PAA@PDA-FM membrane not only demonstrates great separation performance (>99.8%) and great flux (>1000 L m-2 h-1) in oil-water immiscible mixtures but also maintains high separation efficiency under conditions of high acidity, alkalinity, and salinity. Additionally, the PVA/PAA@PDA-FM membrane exhibits excellent separation capacity in oil-water emulsions, which can maintain the >99.6% separation efficiency even after 40 cycles in harsh environments, showing outstanding reusability. Thus, due to the multiple cross-linked networks in the membrane, the excellent performance makes the PVA/PAA@PDA-FM membrane a good application prospect in water purification and oily wastewater treatment.

Salt distribution and alkalinity characterization in bauxite residue disposal areas from the spatial scale range

Bauxite residue (red mud) has high alkalinity and salinity, which seriously restricts its reuse. It is crucial to understand the salt distribution pattern and alkalinity characteristics in the bauxite residue disposal area (BRDA), which can provide a theoretical basis for realizing the salinity and alkalinity regulation and reuse of bauxite residue. In this paper, samples from different locations and depths of the BRDA were used for the determination of soluble salts content, pH, and electrical conductivity (EC), and the correlation between the indicators was analyzed. The results show that bauxite residue has a high content of soluble salts, and the spatial distribution of soluble salts in the BRDA is relatively complex, with moderate variability, but does not show an obvious regularity. The major cations are Na+, K+ and the major anions are CO32−, HCO3−. Through cluster analysis, the soluble ions in bauxite residue can be divided into two main groups, one is Na+, CO32−, HCO3−, and the other is Ca2+, Mg2+, K+, Cl− and SO42−. PH has a significant positive correlation with Na+, K+, CO32− and HCO3−, and a negative correlation with Ca2+. And its alkalinity depends to a large extent on carbonate and bicarbonate, and the Na+ content can be predicted from EC, thus reflecting the concentration of alkaline residues in the bauxite residue.

Improved comprehensive adhesion performance of aggregate- recycled asphalt interface via incorporating steel slag

Steel slag, a typical industrial waste, reveals high alkalinity and abundant texture, endowing its excellent adhesion performance with asphalt and facilitating its implementation in recycled asphalt mixture. While few studies focused on the interaction mechanism and comprehensive adhesion performance of steel slag- recycled asphalt interface. Hence, this topic merits further exploration. In this study, the interface models of steel slag-asphalt were established and their interface parameters also were surveyed. And the comprehensive evaluation index of adhesion performance was explored by the improved radar chart. The experimental results elaborate that steel slag exhibits the larger surface energy of 46.69 mJ/m2 and higher percentage of dispersion component of 76.6 %. Recycled asphalt-steel slag demonstrates the greater adhesion work, the smaller exfoliated work and the larger adhesive destructive force than recycled asphalt-basalt, indicating its superior adhesion ability. Steel slag-asphalt molecule behaves the lower radial distribution function and larger interfacial bonding energy due to the dual provision of van der Waals force and electrostatic adsorption force. The exfoliated work in experiment and adhesion work in simulation presents a Pearson correlation coefficient of −0.683, resulting in their strong negative correlation. Steel slag-recycled asphalt interface with the higher comprehensive evaluation index of 0.9155 reveals the superior comprehensive adhesion performance than basalt- recycled asphalt.

Physicochemical characteristics and discolouration potentials of Pulpine mineral® and Pulpine NE®

ABSTRACT Aim: To compare the physicochemical properties (solubility, pH, radiopacity and crown discoloration) of Pulpine mineral (PMIN) and Pulpine NE (PNE) with the conventional material, mineral trioxide aggregate (MTA). Methodology: Specimens of the tested materials were prepared according to the manufacturer’s instructions using split Teflon ring molds. Solubility was evaluated by the percentage of material mass loss over 24 h and one week. The alkalinity was measured after each evaluation period using a pH meter. Other specimens were digitally radiographed on a size 2 sensor plate along with an aluminum step wedge to analyze the radiopacity by the Image J software. Finally, crown discoloration was assessed after applying the tested materials in the pulp chamber of sound human premolars using spectrophotometer. All data were statistically analyzed. Results: Compared to MTA, both materials had significantly higher solubility and lower radiopacity (P<0.05). The alkalinity of PMIN was higher than that of MTA and PNE. Unlike PMIN, PNE and MTA caused crown discoloration. Conclusions: PMIN exhibits promising results related to high alkalinity and adequate color stability but it needs modifications for radiopacity and solubility.

Amine-free synthesis of high-silica ZSM-5 assisted with calcined silicalite-1 and ethanol with the investigation of mechanism

Amine-free synthesis of high silica ZSM-5 with high crystallinity and well-defined morphology was challenging. In this work, ZSM-5 with the fed silica-alumina ratio (SAR) of 100 was rapidly synthesized with the assistance of the calcined silicalite-1 seed and ethanol, and their crystal structures, morphology and microporous properties were characterized by XRD, SEM, FT-IR, ICP and N2 adsorption-desorption and so on. Firstly, the crystallization temperature was optimized between 140 and 180 °C at a certain alkalinity and ethanol content, and 160 °C was selected to not only provide high crystallization rate but also ensure the stability of high-silica skeleton. Secondly, the influences of the EtOH/SiO2 ratio, Na2O/SiO2 ratio and crystallization time on the crystallization of high-silica ZSM-5 were investigated at 160 °C. The results showed well-crystalline high-silica ZSM-5 could be synthesized within a wide range of the EtOH/SiO2 ratios (0.5–2.0) and the increase of ethanol content slightly inhibited the growth of ZSM-5 along b-axial of hexagonal prisms due to the preferential adsorption of excess ethanol on the {010} crystal plane and the formation of Si–O–C2H5; high alkalinity was favorable for the preparation of a small-sized and well-crystalline ZSM-5 due to the rapid depolymerization of calcined seed and the contribution of mass nucleation sites; meanwhile, excellent micropore characteristic of high-silica ZSM-5 further proved that the synthetic strategy of seed + ethanol was feasible. Finally, the synergistic action mechanism of calcined seed and ethanol for the synthesis of high-silica ZSM-5 was revealed that silicalite-1 with MFI structure unit combined with Na+(H2O/EtOH) with larger radius were very important for rapidly assembly of a large number of silica species into MFI framework.

The utility of freshwater dinoflagellate cyst assemblages as a paleoecological proxy: An assessment from boreal lakes (northwest Ontario, Canada)

Aquatic palynomorphs have the potential to provide valuable insights into past environments but little has been done to assess the utility of freshwater dinoflagellate cysts as palaeoecological proxies of lacustrine environments. This study is the first to compare the distribution of freshwater dinoflagellate cysts found in surface sediments from 32 boreal lakes with varying physical and chemical characteristics. Cysts of Fusiperidinium wisconsinense, Parvodinium umbonatum, and Peridinium willei were nearly ubiquitous, but of the remaining cyst taxa, only Parvodinium inconspicuum, Peridinium limbatum, and Peridinium volzii were abundant but present in a smaller number of lakes. Assemblage composition broadly clustered into three groups: 1) an assemblage (primarily Peridinium spp.) associated with relatively shallow, mesotrophic lakes; 2) an assemblage dominated by F. wisconsinense in mesotrophic lakes with intermediate depth and relatively high pH and alkalinity; and 3) an assemblage dominated by P. umbonatum in deeper oligotrophic lakes. Moreover, changes in dinoflagellate cyst assemblage were assessed in a sediment core spanning the Holocene from nearby Gall Lake and interpreted alongside other previously published paleoecological proxies from this core. High abundances of many dinoflagellate cysts including P. limbatum, P. willei, F. wisconsinense, and P. inconspicuum were observed when lake production was high at a time when lake-levels were low and climate was more arid than today. This study suggests that dinoflagellate cysts in lacustrine sediments are, when abundant, promising both in modern and core samples, and the relationships between assemblages today and in the past can contribution additional information in understanding past ecological conditions.

A feasibility study of using low-alkalinity seawater sea sand concrete to improve the long-term bond performance of the BFRP bar in the seawater environment

BFRP bar has been recognized as one of the most promising alternative reinforcements to address the chloride-induced corrosion of steel bar-reinforced concrete structures in the marine environment. However, the high alkalinity of normal concrete is aggressive to BFRP bars, affecting their long-term bond performance. To address this issue, the bond durability performance of BFRP bar-reinforced low-alkalinity seawater sea sand concrete (SWSSC) after aging in seawater was investigated using the central pull-out test. Scanning electron microscopy (SEM) was also used to characterize the microstructure of BFRP bar-SWSSC interfaces. The findings revealed that since the corrosion of BFRP bars in low-alkalinity SWSSC is substantially lower, the bonding durability performance of BFRP bar-reinforced low-alkalinity SWSSC is significantly higher than that of ordinary SWSSC pull-out specimens. After 270 days of accelerated aging in seawater at 55 °C, bond strength retention in normal SWSSC specimens reduces to about 73 %, whereas that of low-alkalinity SWSSC specimens improves to about 107–110 %. The energy consumption and carbon emissions of low-alkalinity SWSSC are less than half of those of normal SWSSC.

The pH test technology suitable to evaluate content of hazardous electric arc furnace oxidizing slag in fine aggregate

In this study, a standard pH test procedure, based on the high alkalinity of electric arc furnace oxidizing slag, was developed for rapid content evaluation of potentially hazardous slag in the fine aggregate and recommended standards are further proposed. The advantages of the developed procedure include easy equipment acquisition, simple test method, short time, and high accuracy. This study found that sample size, water source, and filtrate process were the factors affecting the pH test accuracy. In the test, the pH increased with a decrease in the aggregate size when the proportion of electric arc furnace oxidizing slag in aggregate was fixed, especially when the aggregate size was less than 0.225 mm. Upon comparison of the results of autoclaved mortar bar expansion tests, a good logarithmic relationship was observed between pH and electric arc furnace oxidizing slag content. It is suggested that pH 9.0 could be used as the standard to determine excessive electric arc furnace oxidizing slag in fine aggregate.

Alkalinity Regulation and Optimization of Cementitious Materials Used in Ecological Porous Concrete.

Ecological porous concrete (EPC) is one of the novel formulations of concrete with unique phytogenic properties. However, achieving both low alkalinity and high strength in EPC proves challenging due to the inherently high alkalinity of the pore environment, which hinders the growth of the plant and affects its ecological benefits significantly. This research investigated the utilization of 15 types of chemical admixtures and diatomaceous earth as alkali-reducing agents to optimize the properties of silicate cementitious materials for the applications of EPC. To identify the most effective agents, the pH value and compressive strength of the cement paste were adopted as the screening criteria for the selection of the essential alkali-reducing ingredients. Subsequently, a composite approach combining chemical admixtures and DE was employed to explore the synergistic effects on the pH and strength of silicate cementitious materials. The results revealed that a combination of 8% DE, 5% oxalic acid, and 5% iron sulfate functioned effectively and resulted in desirable performance for the concrete. This synergistic blend effectively consumed a large amount of Ca(OH)2, reducing the pH of cement paste to 10.48 within 3 days. Furthermore, the hydration reaction generated C-S-H with a low Ca/Si ratio, leading to a remarkable increase in the compressive strength of the concrete, reaching 89.7 MPa after 56 days. This composite approach ensured both low alkalinity and high strength in silicate cementitious materials, providing a theoretical basis for the application and promotion of EPC in the ecological field.

Identification of prevalent leachate percolation of municipal solid waste landfill: a case study in India

Landfill leachate forms when waste-inherent water and percolated rainfall transfer are highly toxic, corrosive, acidic, and full of environmental pollutants. The release of leachate from municipal solid waste (MSW) landfill sites poses a severe hazard to human health and aquatic life. This study examined the impact of leachate from Delhi’s Ghazipur landfill on the nearby groundwater quality. Analysis of leachate samples was done to determine various parameters such as total dissolved solids (TDS), hardness, alkalinity, electrical conductivity, pH, BOD5, COD, nitrate, sulphate, chloride and iron, and presence of coliform bacteria. Significant dissolved elements (22,690–34,525 mg/L) were observed in the samples, indicated by the high conductivity value (1156–1405 mho/cm). However, a stable pH range (6.90–7.80) of leachate samples was observed due to high alkalinity concentrations between 2123 and 3256 mg/L. The inverse distance weighing (IDW) interpolation tool from QGIS 3.22.7 developed spatial interpolated models for each parameter across the Ghazipur area. The IDW interpolated graphs of various parameters over the whole study area confirmed these contaminations. In addition, leachate and groundwater samples were physio-chemically analyzed, and temporal fluctuation in landfill waste has also been studied. The temporal fluctuation results showed that when heat is produced, transmitted, and lost throughout the waste system, the maximum temperature position fluctuates over time. The findings of this study highlight the critical importance of landfill management in reducing groundwater contamination from MSW leachate.

Accelerated chloride-induced corrosion of hot-dipped galvanized reinforcements and its influence on bond strength to concrete

This work studies the behavior of hot-dipped galvanized steel against chloride corrosion and its effect on its bond strength to concrete. Chloride-induced corrosion was accelerated using an electrical field. Two steel diameters were adopted and bond strength was assessed using a standardized pull-out test, followed by measuring different degrees of reinforcement corrosion. Results show that the initial corrosion of hot-dipped galvanized steel, due to the high alkalinity of fresh concrete, does not affect the performance of reinforced concrete and that galvanized steel has superior bond strength to concrete than non-galvanized steel. The relationship between the degree of corrosion of galvanized reinforcement and its bond strength to concrete occurs according to a regular pattern, independently of the diameters of the reinforcements. The pattern shows an initial increase in bond strength, followed by a stabilization region and then a region where the bond strength decreases with the increase in degree of corrosion. Experimental results also show that the corrosion process of galvanized steel may be represented by an adaptation of Tuutti’s model that shows all the phases of the corrosion process: zinc passivation period, initiation period, depassivation of zinc layer, corrosion propagation of zinc, simultaneous depassivation of steel, and corrosion propagation of steel.

Chemical, biochemical, and bioactivity studies on some soda lakes, Wadi El-Natrun, Egypt

Wadi El-Natrun is one of the most observable geomorphological features in the North-Western Desert of Egypt; it contains several old saline and saline soda lakes. This study investigates physicochemical and biochemical characteristics and estimates the total phenolic content (TPC), total flavonoid content (TVC), and bioactivities of sediment, cyanobacteria, and brine shrimp (Artemia salina) in soda lakes, i.e., El-Hamra Lake 1 (H1) and El-Hamra Lake 2 (H2). These soda lakes are unique extreme ecosystems characterized by high pH (> 9.3), high alkalinity, and salinity. Some extremophilic microorganisms are hosted in this ecosystem. The results revealed that the chemical water type of studied lakes is soda-saline lakes according to the calculated percentage sequence of major cations and anions. Sodium ranked first among major cations with an abundance ratio of e% 58, while chloride came first among anions with an abundance ratio of e% 71, and bicarbonate and carbonate occupied the last rank with an abundance of 6%. The biochemical investigations showed that TPC and TVC are present in concern contents of sediment, cyanobacteria, and brine shrimp (A. salina) which contribute 89% of antioxidant capacity and antimicrobial activities. Thus, this study helps better understand the chemical and biochemical adaptations in soda lake ecosystems and explores natural sources with potential applications in antioxidant-rich products and environmental conservation efforts.

Interpretation by literature review of the use of calcium hydroxide as an intra-ductal medication

The effectiveness of calcium hydroxide as an antiseptic agent in endodontics has recently gained relevance, being crucial to ensure optimal results in endodontic treatments. The aim of the study was to interpret the use of calcium hydroxide as an intra-endodontic medication by means of a literature review. A narrative review of the updated literature was performed, with the aim of describing the effects of CaOH and exposing the different clinical procedures in which it is used, as well as the results of its application in endodontic therapy. Clinical trials, meta-analyses and original and published articles from 2018 to 2023, in English or Spanish, were included. It was found that calcium hydroxide plays a key role in endodontics due to its dissociation into calcium and hydroxyl ions, which contributes to its antimicrobial and biological efficacy. Its clinical application is extensive, including preventive endodontics, direct and indirect pulp capping, pulp curettage and pulpotomies, especially in teeth with incomplete apical development. The mechanism behind its antimicrobial action lies in the diffusion of calcium ions and the increase in pH, which limit the rate and enhance the antimicrobial effect in root canals. It was concluded that, for an effective endodontic treatment, it is necessary to eliminate all microorganisms from the root canal. In addition, the microorganism such as E. faecalis has a high resistance to endodontic treatment, which is due to its ability to penetrate into the dentinal tubules, tolerate high alkalinity, and form biofilms

Formation of dolomites from the newly discovered ancient cold seep in the Middle Dongsha area of the South China Sea

Remotely operated vehicle (ROV) observations have recently revealed seep dolomite deposits covering the seafloor on Middle Dongsha of the South China Sea (SCS). Spurred by these findings, we studied the mineralogical and geochemical properties to examine the seep dolomite’s origin, precipitation mechanism, and formation environment. These carbonates mainly comprise dolomite (from 64 to 84 wt%), followed by small amounts of calcite (from 1 to 3 wt%), locally containing magnesite (∼4 wt%), and goethite (∼14 wt%). Extensively developed mineralized cells containing high Mg and Ca contents found in chimneys imply that microbially-mediated processes probably participated in the reactivation of dolomite precipitation. The moderate and concentrated δ13C values (from −36.64 to −39.16‰, V-PDB) indicated that the carbon in carbonates was mainly derived from thermogenic methane. The methane fluids most likely ascended beneath the volcaniclastic unit and inherited enriched positive Eu anomalies due to fluid–rock interactions during their seepage along tectonic faults to the seafloor. The δ18O values (4.2–4.8‰, V-PDB) of carbonate suggested that an 18O-depleted fluid was involved in carbonate precipitation. The high total Rare-Earth Element contents (ΣREE) of seep carbonates varied from 61 ppm to 92 ppm, reflecting the chemical composition of surrounding pore waters at the time of carbonate precipitation, exhibiting less mixing with seawater. It may also indicate higher alkalinity and pH of the pore water. Although the sea-like REE patterns (HREE-enriched, negative Ce anomalies) are not caused by seawater, they may be due to the complexation competition between humic acid (HA) and carbonate for REE at high pore-water alkalinity and high CO32− concentrations. This is consistent with the dolomite chimney pointing toward a formation environment in relatively deep sediments, in particular, close to the sulfate-methane interface in sediments, where the bicarbonate concentration reaches its maximum due to AOM. Moderate Mo and no U enrichments appeared in the carbonates, suggesting a relatively lower intensity of methane seepages with relatively reduced AOM rates. The wide range of (Mo/U)EF values and U–Mo covariation indicates the very dynamic AOM rate (slow to moderate) and redox conditions (mostly suboxic–anoxic, occasionally sulfidic conditions) during carbonate formation due to episodically changing seepage activity.

Comparison of Land Suitability Methods for Estimating Quantity of Maize Yield in Calcareous Soils

ABSTRACT The modeling and assessment of land suitability is a prerequisite for land development and is one of the necessary needs to prevent land degradation. Maize is considered to be the most important crop, covering significant areas of agricultural lands in widely different regions across the world. However, not all available lands are equally suitable for maize cultivation. The main objective of this study was focused on identifying the potentials as well as the limitations of studied calcareous soils for maize cultivation in north Khuzestan province, Iran. Furthermore, some parametric models and multi-criteria land suitability evaluation methods for physical, chemical, fertility, and climatic factors (MC-LSE) were compared in estimating the maize yield. The required samples were taken from 23 land units by excavating control pedons. The necessary physicochemical parameters were then measured in the laboratory. The land indices were calculated by using different methods. The maize potential production of the investigated area was then obtained based on the climatic conditions. Finally, using land indices and the potential production, the estimated yield for each land unit was calculated and compared with the actual yield data. The obtained results indicated that the main limiting factors for maize yield in the region are high soil CaCO3 content, high salinity, high alkalinity and low organic matter. A comparison of predicted and actual yield indicated that the corrected square root method is accurate enough to assess land suitability and to estimate the maize yield with a high coefficient of determination (0.91) and a low RMSE value.

Potentially toxic elements distribution, petrography, and synchrotron characterization in polluted soils around industrial complex, Central Jordan

Industry is the main source of soil pollution in Jordan, where higher concentrations of potentially toxic elements were found in the soil around industrial estates. This study is dealing with an industrial pollution hot spot that is a steel factory in central Jordan that emits various ashes and gases. This area is moderately inhibited, and its soil is increasingly utilized in agricultural activities. High Fe, Cr, Mn, Pb, and V contents were recorded in the soil adjacent to the factory mainly concentrated on the prevailing wind direction. The studied sites bear heavy metalloids concentrations exceeding the permissible limit of WHO/EPA. These concentrations were found in topsoils and they decreased downward because of low mobility due of high soil alkalinity and lower pedogenesis. Moreover, the synchrotron-based XAFS technique was used to understand changes in oxidation states of Fe atom as well as in its structural parameters with depth. EXAFS analysis reveals association of Fe atoms mainly with oxygen (O), which indicates the anthropogenic Fe source. XANES data shows that Fe occurs in divalent (Fe2+) and trivalent (Fe3+) forms, which indicates that magnetite is dominating the topsoil. This Fe-phase is usually formed during oxygenated high thermal manufacturing processes. The topsoils SEM-EDS investigations confirmed the dominance of magnetite spheres, which coincides with the positive correlation between Fe and other elements as indicated from the statistical interpretation of the data.