Sequential Chemical Extraction Research Articles

Effect of Land Use Change on Molecular Composition and Concentration of Organic Matter in an Oxisol.

Land use change from native vegetation to cropping can significantly affect the quantity and quality of soil organic matter (SOM). However, it remains unclear how the chemical composition of SOM is affected by such changes. This study employed a sequential chemical extraction to partition SOM from an Oxisol into several distinct fractions: water-soluble fractions (ultrapure water (W)), organometal complexes (sodium pyrophosphate (PP)), short-range ordered (SRO) oxides (hydroxylamine-HCl (HH)), and well-crystalline oxides (dithionite-HCl (DH)). Coupled with Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS), the impact of land use change on the molecular composition of different OM fractions was investigated. Greater amounts of OM were observed in the PP and HH fractions compared to other fractions, highlighting their importance in SOM stabilization. The composition of different OM fractions varied based on extracted phases, with lignin-like and tannin-like compounds being prevalent in the PP and HH fractions, while aliphatic-like compounds dominated in the DH fraction. Despite changes in the concentration of each OM fraction from native vegetation to cropping, there was little influence of land use change on the molecular composition of OM associated with different mineral phases. No significant selective loss or preservation of organic carbon compounds was observed, indicating the composition of SOM remained unchanged.

Geochemical fractionation, bioavailability, and ascertaining ecological risk of phosphorus in surface and core sediments of mangroves, western coast of India.

Phosphorus (P), a crucial macronutrient, is essential in the maintenance of ecosystem productivity and the biogeochemical processes of other biogenic substances found in marine settings. The aim of the present study is to quantify the different geochemical fractions, bioavailability, and ecological risk of phosphorus in surface and core sediment of mangroves, Gulf of Kachchh (GoK). To better understand the P dynamics, sequential chemical extraction techniques were used to study sediment P pool distribution such as exchangeable P; Fe-bound P; authigenic P; detrital P; and organic P. The total sedimentary P ranged from 539.51 to 7217.24mg/kg in pre-monsoon and 487.04 to 7180.26mg/kg in post-monsoon, and was primarily composed of inorganic P. Authigenic P and Fe-bound P were the dominant fractions of P in surface and core sediments, exhibiting a significant long-term P reservoir. Sources such as riverine inputs, industrial and sewage discharge, aquaculture farms, and seaport operations all have an impact on the P dynamics in GoK. Furthermore, organic matter, pH, ORP, and diagenetic processes in sedimentary environment have influenced P retention and release. FeBD:Fe-P ratio indicates the presence of Fe matrices, having strong adsorption potential for P, with the availability of a surplus of Fe(III) (oxy)hydroxides serving as a significant P pool, governing the P dynamics. The P enrichment index (PEI) showed that sediments were highly impacted by anthropogenic P and could cause a high ecological risk. Bioavailable phosphorus (BAP) suggests the availability of an ample amount of bioavailable P fractions (average of 49.70% post-monsoon and 44.64% post-monsoon) in surface sediments. Sites 3, 13, 14, 20, 21, and 26 exhibited considerably higher BAP. Core 1 comprised significantly higher BAP (60.52%). Thus, sediments of GoK could act as a source of P to the overlying water if released from sediments.

Experimental Investigation on Gallium and Germanium Migration in Coal Gangue Combustion

Gallium (Ga) and germanium (Ge) critical elements have a wide range of applications and market value. Extracting critical elements from coal gangue and combustion products can alleviate pressures on primary mining resources. Understanding the transformation behavior of Ga and Ge during coal gangue combustion processes is significant for resource utilization and environmental protection. Coal gangue from Xing’an League, Inner Mongolia, was chosen to explore how combustion temperatures (600 °C to 1000 °C) and particle sizes (50, 80, 10, 140, and 200 mesh) influence Ga and Ge migration during combustion. Techniques such as ICP-MS, XRD, XRF, SEM, TG-DSC, and sequential chemical extraction were employed to analyze the transformation of minerals and to quantify the contents and occurrence forms of Ga and Ge. Smaller gangue particle sizes were associated with higher concentrations of Ga and Ge. Approximately 99.19% of Ga and Ge in coal gangue were found in the residual, organic/sulfide-bound, and metal-oxide-bound modes. High temperatures promoted element volatilization and changed the reactions and interactions between elements and minerals. As combustion temperatures rose from 600 °C to 1000 °C, Ga and Ge contents in the products declined progressively. Under high temperatures, minerals like kaolinite, illite, and pyrite in gangue converted to silicate glass phases, mullite, and hematite. Minerals like kaolinite, calcite, and pyrite melted, leading to increased cohesion and agglomeration in the products. Over 90% of Ga and Ge in the combustion products existed in the residual, organic/sulfide-bound, and metal-oxide-bound forms. Moreover, Ga was enriched in combustion products, with its content exceeding critical extraction levels. The results may provide a useful reference for developing critical elements enrichment, extraction, and separation technologies from coal gangue.

Bioleaching ion-unexchangeable rare earth in ion-adsorption type rare earth waste tailing

Ion-adsorption type rare earth ores (IREO) in China serve as the primary source of medium and heavy rare earth globally. With the rapidly growing demand for rare earth elements (REEs) and the dwindling supply of premium IREO, enhancing the recovery of REEs, especially the ion-unexchangeable REEs with ultra-low content and ambiguous speciation from IREO or its tailing, has become a critical trend and challenge. This study identified the occurrences of ion-unexchangeable REEs, primarily detected in Fe-enriched minerals, xenotime, and monazite of IREO using TESCAN integrated mineral analyzer (TIMA) and laser ablation inductively coupled plasma mass spectrometer (LA-ICP-MS) analysis. To extract these elusive REEs, a bioleaching technique utilizing Aspergillus niger (A. niger) metabolites was proposed, achieving a leaching yield of 31.4 wt%. Complementary sequential chemical extraction methods (SCEM), X-ray photoelectron spectroscopy (XPS), and density functional theory (DFT) calculations further elucidate the underlying mechanism, involving the carboxylic acid produced by the metabolic process of microbes that dissolves goethite by disrupting FeO bonds and liberating REEs, which complexed with carboxylate (RCOO), to promote further dissolution. This work offers insight into enhancing the recovery of ion-unexchangeable REEs from IREO or its tailing, paving the way for sustainable and efficient rare earth mining practices.

Performance of an integrated sediment interceptor in removing phosphorus from agricultural drainage water

Reducing phosphorus (P) loss from agricultural drainage water is challenging. In this study, we aimed to remove P from agricultural drainage water by developing an integrated sediment interceptor with adsorbent modules filled with Zr/Zn nanocomposite-modified ceramsite (ZMC-interceptor). The results of sequential chemical extraction and 31P NMR showed that the contents of H2O-P (1.15 % of total P), NaHCO3-Pi (10.48 % of total P), and ortho-P (orthophosphate, 90.6 % of total P) in the sediments of the ZMC-interceptors were higher than those in nearby field soils. The average enrichment ratios of particulate P (PP, >450 nm), medium-colloidal P (MCP, 220–450 nm), fine-colloidal P (FCP, 1–220 nm), and truly dissolved P (Truly DP, <1 nm) in the sediment over the field soil were 1.37, 1.21, 1.70, and 3.01, respectively. No significant differences were found in the sediment P-trapping function with and without ZMC integrated sediment interceptors. However, the ZMC-interceptors remarkably reduced total P (39.7 % for influent concentrations of 0.19–0.68 mg L−1) from agricultural drainage water compared to those unmodified ceramsite-interceptors (21.7 % for influent concentrations of 0.17–0.66 mg L−1) during the drainage ‘window period’ (June–August 2022). This was mainly due to the higher removal efficacies of MCP (19.7 %), FCP (23.3 %), and Truly DP (34.8 %) of the ZMC-interceptors. This study highlighted that the ZMC-interceptor not only trapped P in the sediment but also facilitated the removal of different-sized P fractionated from agricultural drainage water.

Study on modes of occurrence and selective leaching of lithium in coal gangue via grinding-thermal activation

Lithium (Li), an important strategic metal, has been paid attention to by researchers, entrepreneurs, and political circles, especially its recovery from coal-based solid waste. In this paper, the occurrence modes of Li in coal gangue (CG) have been studied through sequential chemical extraction, distribution correlation, and intercalation-leaching test. The CG was pretreated via grinding-thermal activation to selectively leach Li. The correlation between Li and magnesium (Mg) during the leaching process was also investigated. Finally, the migration mechanism of Li during the grinding-thermal activation process was analyzed using solid-state nuclear magnetic resonance for the first time. The results of the first three experiments demonstrated that Li primarily exists within the kaolinite. The extraction of Li from CG after grinding-thermal activation is 44.82 % using 0.2 M (NH4)2SO4 (pH = 4.0), while aluminum (Al) was almost insoluble, exhibiting the selective leaching of Li. 84.76 % of Li and 17.63 % of Al are obtained at pH = 1.0. The correlation analysis result suggests that lithium ions (Li+) exist in the octahedron of the lattice as charge compensation. The migration mechanism is explained by the chemical shift of Li+, which moves from −0.196 ppm (raw, in the octahedron) to −0.319 ppm (ground, octahedral destruction) and further to −0.564 ppm (thermal activation, out of the octahedron). This paper can provide a theoretical basis for the occurrence of Li and a new method for selective extraction of Li from CG.

Fractionation and Lability of Phosphorus Species in Cottonseed Meal-Derived Biochars as Influenced by Pyrolysis Temperature.

Defatted cottonseed meal (CSM), the residue of cottonseeds after oil extraction, is a major byproduct of the cotton industry. Converting CSM to biochar and utilizing the goods in agricultural and environmental applications may be a value-added, sustainable approach to recycling this byproduct. In this study, raw CSM was transformed into biochar via complete batch slow pyrolysis at 300, 350, 400, 450, 500, 550, and 600 °C. Thermochemical transformation of phosphorus (P) in CSM during pyrolysis was explored. Fractionation, lability, and potential bioavailability of total P (TP) in CSM-derived biochars were evaluated using sequential and batch chemical extraction techniques. The recovery of feed P in biochar was nearly 100% at ≤550 °C and was reduced to <88% at 600 °C. During pyrolysis, the organic P (OP) molecules predominant in CSM were transformed into inorganic P (IP) forms, first to polyphosphates and subsequently to orthophosphates as promoted by a higher pyrolysis temperature. Conversion to biochar greatly reduced the mobility, lability, and bioavailability of TP in CSM. The biochar TP consisted of 9.3-17.9% of readily labile (water-extractable) P, 10.3-24.1% of generally labile (sequentially NaHCO3-extractable) P, 0.5-2.8% of moderately labile (sequentially NaOH-extractable) P, 17.0-53.8% of low labile (sequentially HCl-extractable) P, and 17.8-47.5% of residual (unextractable) P. Mehlich-3 and 1 M HCl were effective batch extraction reagents for estimating the "readily to mid-term" available and the "overall" available P pools of CSM-derived biochars, respectively. The biochar generated at 450 °C exhibited the lowest proportions of readily labile P and residual P compounds, suggesting 450 °C as the optimal pyrolysis temperature to convert CSM to biochar with maximal P bioavailability and minimal runoff risk.

Extraction of valuable critical metals from coal gangue by roasting activation-sulfuric acid leaching

ABSTRACT Coal gangue is a bulk industrial solid waste produced in the process of coal mining and washing, with the dual attributes of resourcefulness and hazardousness. It can be used as a reserve resource for valuable critical metals such as aluminum (Al), lithium (Li), gallium (Ga), and rare earth elements (REEs). In this paper, the occurrence modes of Li, Ga, and REEs in coal gangue were studied by sequential chemical extraction method. The extraction of valuable critical metals from the coal gangue was systematically studied by roasting activation-sulfuric acid leaching process, and the activation mechanism was elucidated. The results showed that roasting can destroy the inert kaolinite structure in coal gangue and significantly improve the leaching rate of valuable critical metals. Under the optimum conditions, the leaching rates of Al, Li, Ga, and REEs reached 86.51%, 74.46%, 95.45%, and 77.14%, respectively, and the leaching behaviors of Al, Li, and Ga were highly similar. In addition, the characterization of the leaching residue revealed 83.96% silicon oxide content with a loose and porous surface, which could be used to prepare silicon-based products. This study provides the theoretical basis and technical support for the utilization of valuable metals in coal gangue.

Speciation of Sedimentary Phosphorus in an Urban Wetland: The Case of El Oulfa Pound. Casablanca, Morocco

Eutrophication remains a major concern for the quality of surface waters worldwide. This phenomenon significantly restricts water usage. The El Oulfa pond, located in Casablanca, is experiencing advanced eutrophication primarily caused by domestic wastewater discharge. Despite the cessation of these discharges and the implementation of an aeration system coupled with biological treatment, physicochemical analyses of the water body have shown an increase in phosphorus levels. This situation suggests a sedimentary origin for this nutrient, considered a limiting factor in eutrophication. This study aims to determine the various fractions of sedimentary phosphorus and their involvement in the eutrophication of the pond, using sequential chemical extraction according to Golterman. This sequential extraction revealed that the bioavailable phosphorus bound to organic matter (ASOP) represents 60.45% of the total phosphorus. Regarding mineral phosphorus, the fraction bound to calcium (CaCO3-P) is the most dominant, while the bioavailable fraction bound to iron (P-Fe) accounts for only 1.63% of the total phosphorus.

Mineralogical fingerprint and human health risk from potentially toxic elements of Fe mining tailings from the Fundão dam

In 2015, >50 million cubic meters of Fe mining tailings were released into the Doce River basin from the Fundão dam, raising the question of its consequences on the affected ecosystems. This study aimed to establish a mineralogical-(geo)chemical association of potentially toxic elements (PTEs) from Fe mining tailings from the Fundão dam, collected seven days after the failure, through a multidisciplinary approach combining assessment of the risk to human health, environmental geochemistry, and mineralogy. Thus, eleven tailings samples were collected with the support of the Brazilian Military Police Fire Department. Granulometry, magnetic measurements, optical microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, and sequential chemical extraction of PTEs analyses were performed. Contamination indexes, assessment of risk to human health, and Pearson correlation were calculated using the results of sequential chemical extraction of PTEs. The predominance of goethite in Fe oxyhydroxide concentrates from the mud indicates that the major source of hematite may not be from tailings, but from pre-existing soils and sediments, and/or preferential dissolution of hematite in deep flooded zones of the tailings column of the Fundão dam. Moreover, the high correlation of most carcinogenic PTEs with their crystallographic variables indicates that goethite is the primary source of contaminants. Goethites from Fe mining tailings showed high specific surface area and Al-substitution, and due to their greater stability and reactivity, the impacts on PTE sorption phenomena and bioavailability may be maintained for long periods. However, their lower dissolution rate, and the consequent release of heavy metals would promote greater resilience for affected ecosystems, preventing significant PTE inputs under periodic reduction conditions. More specific studies, involving the crystallographic characteristics of Fe oxyhydroxides should be developed since they may provide another critical component of this set of complex and dynamic variables that interfere with the bioavailability of metals in ecosystems.

Phosphorus-enriched biochar from biogas residue of Eichhornia crassipes: transformation and release of phosphorus

Pyrolysis is an effective technology for treating and utilizing biogas residue. To explore the phosphorus (P) supply capacity of the biochar generated from biogas residue of Eichhornia Crassipes, the P speciation of E. crassipes biogas residue and biomass during pyrolysis (300–700 °C) was analyzed by combining sequential chemical extraction, 31P nuclear magnetic resonance (NMR) and P K-edge X-ray absorption near edge structure (XANES) spectroscopy. Pyrolysis treatment promoted the conversion of amorphous Ca-P phases in biogas residue and biomass into crystalline hydroxyapatite (HAP) phase, which matched the formation of stable HCl-P pools in the biochar derived from biogas residue (AEBs, 22.65–82.04%) and biomass (EBs, 13.08–33.52%) in the process of pyrolysis. Moreover, the total P contents in AEBs (19.43–28.92 mg g−1) were higher than that of EBs (3.41–5.26 mg g−1), indicating that AEBs had a great P reclamation potential. The P release kinetics from AEBs and EBs in water were evaluated via an incubation experiment for 360 h. The P release from both AEBs and EBs conformed to the pseudo-second order kinetics model (R2 > 0.93), but their P release behaviors were different. The P release of AEBs conformed to the diffusion-re-adsorption model, while that of EBs accorded with the diffusion-dissolution model. The diffusive gradients in thin-films (DGT) analysis showed that AEBs could significantly increase soil available P content as compared with EBs. Hence, the biochar produced from biogas residue of E. crassipes via pyrolysis has a good application potential as a P fertilizer.Graphical

Fate of fluorine in stratified samples from BGL gasifier at Hailar Chemical Plant, Inner Mongolia: An intermediate process perspective

This study investigated the fate of Fluorine (F) during the super high temperature (2000 °C) gasification process by analyzing 23 stratified samples inside the British Gas Lurgi (BGL) gasifier in production. Through sequential chemical extraction (SCEP), ion selective electrode (ISE), scanning electron microscope with energy dispersive spectrometer (SEM-EDS), high-resolution transmission electron microscope with energy dispersive spectrometer (HRTEM-EDS) and X-ray diffraction (XRD), this article complements the intermediate forms of transformation of F, in addition to the methods of deduction of the fate of F through input and output.Overall, the concentration of fluorine gradually decreases with increasing temperature and ≈1200 °C (14th layer) is the key temperature for its volatilisation. This may be related not only to the volatility of organic matter, but also to the significant contribution from the melting of a large amount of silicate and aluminosilicate minerals in the sample.In addition, the fluorine concentration remained stable from layer 14 to layer 27 (≈2000 °C), rather than continuing to evaporate, due to the formation of a new, stable mode of fluorine occurrence: Ca-P-F-Si minerals have been identified. The free and active SiO2, possibly derived from the melting of quartz and kaolinite, played a key role in preventing the melting of fluorapatite. The mechanism of formation of the new refractory materials (Ca-P-F-Si minerals) needs to be further validated by laboratory and computer simulations.

Effect of biomass-coal blending combustion on Pb transformation

Biomass-coal blending combustion is an effective method for utilizing biomass; however, its pollutant emission requires attention. Herein, the effect of biomass-coal blending combustion on lead (Pb) transformation was explored. Combustion experiments were conducted in a fixed-bed reactor, using coal, corn stalk, rice stalk, bamboo flour and their mixtures as fuels, at 1000, 1100, 1200 and 1300 °C. The Pb release ratios were determined by measuring its content in the fuels and solid-phase combustion products. The distribution of Pb forms was analyzed using sequential chemical extraction. The results indicate that blending combustion significantly enhanced the release of Pb. At blending ratio 1:1, the release ratios increased by 1.54–27.2%, 5.30–15.6%, and 2.31–7.76% at 1000, 1100, and 1200 °C, respectively. The potassium (K) components in biomass, mainly KCl and K2CO3, had a significant promoting effect on Pb release. K compounds facilitated the release of residual Pb through reactions with aluminosilicates. The promotion effect weakened as the temperature increased due to the faster evaporation rate of K. When the mass fractions of K in the fuels were equal, K2CO3 exhibited a stronger promoting effect. HCl had minimal impact on the transformation of Pb. The results are helpful for optimizing the combination of biomass and coal to control Pb emission from the blending combustion source.

Mixed nitrate and metal contamination influences operational speciation of toxic and essential elements

Environmental contamination constrains microbial communities impacting diversity and total metabolic activity. The former S-3 Ponds contamination site at Oak Ridge Reservation (ORR), TN, has elevated concentrations of nitric acid and multiple metals from decades of processing nuclear material. To determine the nature of the metal contamination in the sediment, a three-step sequential chemical extraction (BCR) was performed on sediment segments from a core located upgradient (EB271, non-contaminated) and one downgradient (EB106, contaminated) of the S-3 Ponds. The resulting exchangeable, reducing, and oxidizing fractions were analyzed for 18 different elements. Comparison of the two cores revealed changes in operational speciation for several elements caused by the contamination. Those present from the S-3 Ponds, including Al, U, Co, Cu, Ni, and Cd, were not only elevated in concentration in the EB106 core but were also operationally more available with increased mobility in the acidic environment. Other elements, including Mg, Ca, P, V, As, and Mo, were less operationally available in EB106 having decreased concentrations in the exchangeable fraction. The bioavailability of essential macro nutrients Mg, Ca, and P from the two types of sediment was determined using three metal-tolerant bacteria previously isolated from ORR. Mg and Ca were available from both sediments for all three strains; however, P was not bioavailable from either sediment for any strain. The decreased operational speciation of P in contaminated ORR sediment may increase the dependence of the microbial community on other pools of P or select for microorganisms with increased P scavenging capabilities. Hence, the microbial community at the former S-3 Ponds contamination site may be constrained not only by increased toxic metal concentrations but also by the availability of essential elements, including P.

A new method for pre-enrichment of gallium and lithium based on mode of occurrence in coal gangue from Antaibao surface mine, Shanxi Province, China

The presence of a notable concentrations of gallium (Ga) and lithium (Li) in coal gangue, an industrial solid waste, has attracted widespread attention. However, utilization of these resources remains an economic challenge. This study entailed an investigation of the potential of the pre-enrichment of Ga and Li in coal gangue so as to effectively utilize coal gangue resources. The modes of occurrence of Ga and Li in coal gangue were studied using a sequential chemical extraction procedure (SCEP), mineral phase composition, time-of-flight secondary ion mass spectrometry (TOF-SIMS), and elemental content composition. The results indicate that the main mineral components of the coal gangue are mica, quartz, pyrite, and clay. Ga and Li are mainly associated with Al-containing minerals, such as mica and clay. Further, the main noncarrier minerals are quartz and pyrite. Ga and Al exhibit a high degree of correlation, whereas Li exhibits a predominant association with Al and Ti. Ga and Li are also negatively correlated with Fe and Sr. Moreover, sorting experiments demonstrated that the separation of Ga and Li from pre-enriched coal gangue is an effective and environmentally friendly method. This allowed for the discarding of 31.25% of the waste rock, with an Fe content of 32.69%. The concentrate products can potentially be high-quality raw materials for Ga and Li refining facilities, whereas the tailing products can serve as an effective source of iron ore raw materials.

Transformation of phosphorus forms and its regulation on phosphorus availability across differently degraded marsh soils

AbstractSoil phosphorus (P) is a vital nutrient that controls wetland productivity and ecological functions. However, the effects of soil P forms on P availability during wetland degradation are relatively unknown. We selected differently degraded marshes, including non‐degraded marsh (NDM), lightly degraded marsh (LDM), moderately degraded marsh (MDM), and heavily degraded marsh (HDM), to research the changes in soil P forms by sequential chemical extraction and its regulation on P availability in the Zoige Plateau, China. The results showed that compared with the 0–30 cm soil layers of NDM, the main changes in total P concentration were a significant increase of 31.6%–44.2% in LDM and MDM, and the available P concentration increased by 28.7%–76.2% in LDM and MDM but decreased by 4.0%–47.5% in HDM with a lower P activation coefficient. Marsh degradation increased the concentration of soil dicalcium phosphates, P occluded in iron hydroxides, and organic P from the entire profile by 46.7%–137.7%, 31.7%–49.3%, and 78.1%–82.1%, respectively, while it decreased that of iron oxide surface adsorbed P and apatite P by 17.2%–32.2% and 15.3%–27.8%, respectively. Soil available P was mainly related to organic P and P non‐occluded in iron oxide minerals, which might also be a non‐negligible direct source of available P. The transformation from apatite P to organic P was an important regulatory mechanism of P availability in soils during marsh degradation. This study revealed the transformation trajectory of soil P forms owing to soil desiccation accompanied by plant community changes and overgrazing during alpine marsh degradation, and the risk of P limitation in HDMs with low soil available P. For degraded marsh restoration, some measures for improving P availability should be implemented in the future, such as grazing exclusion and the application of organic fertilizer.

Spatial variation of soil phosphorus in the water level fluctuation zone of the Three Gorges Reservoir: Coupling effects of elevation and artificial restoration

The water level fluctuation zone (WLFZ) is a distinctive and important component of the reservoir ecosystem. Due to periodic inundation, the fraction, spatial distribution, and chemical reactivity of soil phosphorus (P) within the WLFZ can potentially impact the loading of P into reservoir waters. However, a detailed study of this subject is lacking. In this study, the soil P in the WLFZ of the Three Gorges Reservoir, China, was examined using a combination of chemical sequential extraction, 31P NMR, and adsorption experiments. The results of chemical sequential extraction showed that HCl-Pi constituted the largest P pool among all P forms, with a mean concentration of 338 mg/kg. The content of HCl-Pi decreased significantly toward the dam, while the content of Res-P decreased in the opposite direction. The highest contents of most P forms and total P were observed at an elevation of 160 m. 31P NMR measurements showed that NaOH-EDTA Pi detectable in WLFZ soils at 145 m, 160 m, and 175 m elevation consisted mainly of orthophosphate and pyrophosphate, while NaOH-EDTA Po contained phosphate monoesters and phosphate diesters, accounting for 1.4 % to 46.2 % of NaOH-EDTA TP. Adsorption experiments showed that soil P in the WLFZ was a potential P source for reservoir waters, with chemisorption being the dominant mechanism of P sequestration. The adsorption equilibrium concentration of WLFZ soil was lower at higher elevations (>170 m) compared to lower elevations (<150 m), exhibiting a decrease in the average maximum adsorption from 271 mg/kg to 192 mg/kg. Statistical analysis suggested that Ca and Fe content, particle size, elevation, and artificial restoration were key factors affecting the fraction and content of soil P in the WLFZ. Our findings contribute to an improved understanding of the behavior of soil P in the WLFZ of large reservoirs and its potential contribution to the reservoir waters.

Phosphorus availability and corn (Zea mays L.) response to application of P‐based commercial organic fertilizers to a calcareous soil

AbstractRecycling of organic wastes for agricultural production has been recommended as a sustainable way to close the phosphorus (P) cycle. This study seeks to characterize the P forms in organic fertilizers derived from agricultural and nonagricultural source materials to understand how these organic fertilizers will affect corn growth and soil available P. Organic fertilizers including turkey litter compost (TLC), biosolid pellets (BSP), and source separated organic compost (SSO) were applied to a sandy loam soil and compared to controls that received no nutrients or chemical fertilizer. Results from sequential chemical extractions and X‐ray absorption near edge structure spectroscopy revealed that most of the P species are inorganic, with SSO and TLC containing primarily Ca‐P and Mg‐P forms, while the P in the BSP treatments was mostly associated with aluminium (Al). The two chemical fertilizer treatments had the greatest impact on corn height at the initial growth stage; however, after 42 days, corn height was similar for the organic fertilizers and chemical treatment. This initial slow response from the organic fertilizer treatments reduced the grain yield compared to chemical treatment. The results of this study suggest that priority should be given to sufficient P availability at the initial growth stage. Overall, organic fertilizer is a promising P source for grain crop production, but calibration and correlation studies are needed to ensure optimum supply of P for the initial growth stage.

New data on mobility of transuranium elements in sediments of the Yenisei River

The inflow of transuranium elements to the Yenisei River was previously associated with the production of weapons-grade plutonium at the Mining-and-Chemical Combine (MCC, Zheleznogorsk, Russia), but the source of transuranium elements in the River today is fabrication of MOX fuel that started recently at the MCC. The current study presents results of sequential chemical extraction of radionuclides from sediment samples collected in 2014 and 2020 in two areas near the MCC discharge site and compares these results with the data obtained previously by sequential extraction of sediments collected during 1999–2007. Over the study period, the strength of binding of 137Cs and 60Co in the Yenisei River sediments was high (up to 100%) and remained so, while the percentages of 241Am and 152Eu in residual solids after sequential extraction increased considerably and the percentage of 239,240Pu in residual solids decreased in samples from all study areas. In samples collected at the position located close to the MCC discharge site, the percentages of the strongly bound 241Am and 152Eu as well as 239,240Pu were lower than in the samples from the other positions. The study demonstrated an enormous increase in 239,240Pu activity concentration in the top sediment layers collected at all positions in 2020 relative to 2014. In the same period, as literature data suggest, 239,240Pu activity concentrations also increased in aquatic organisms of the Yenisei River, which can be indicative of the growing potential bioavailability of plutonium in the aquatic ecosystem, which could be caused by the presence of the mobile form of plutonium in the routine discharges from the MCC.

Lithium isotopic composition of two high‑lithium coals and their fractions with different lithium occurrence modes, Shanxi Province, China

Coal and coal-bearing strata have been considered as potential economic sources of lithium, and, as such have attracted significant attention. Significantly high concentration of lithium has been found in the coals from Shanxi Province, North China. This study examined the lithium isotopic composition of two high-Li coals of different ranks (XJ-8 anthracite and DLT-11 bituminous coal) and their fractions (such as organic-, silicate-) obtained through sequential chemical extraction. Lithium was found to be predominantly associated with silicates. Lithium isotopic compositions in DLT-11 are more positive (δ7Li > 0‰) than those in XJ-8 coal (δ7Li < 0‰) irrespective of which are bulk coals or leachates. Specifically, the carbonate fraction in DLT-11 had the most positive lithium isotopic composition among all fractions. Carbonate fluid hosting positive lithium isotopic composition seems to have had an effect on the lithium isotopic composition of DLT-11 coal. Lithium isotopic composition of XJ-8 anthracite may be a result of lithium re-distribution between organic and inorganic components during coalification, and this was also responsible for lithium isotopic homogeneity in the coal seam.