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Thermal exposure in street canyons has an essential impact on individual outdoor activities and overall health. Street view images (SVIs) have demonstrated significant value in investigating thermal exposure within street canyons. However, current SVIs-based studies cannot explicitly reflect daily thermal exposure, as their focus has been primarily on the spatial distribution of thermal exposure indicators. Few studies explored the relationship between thermal exposure and walking accessibility. In response to this situation, this study proposed a human-scale approach to quantify daily thermal exposure by integrating street thermal environment with walking accessibility. Hemispherical images generated from Baidu Street View panoramas were utilized to estimate the solar duration reaching street canyons, thereby reflecting the thermal exposure for each street canyon. Street networks were analyzed using the spatial syntax method to quantify walking accessibility for each road. By combining street-level solar duration and walking accessibility, this study measured daily thermal exposure from the human-scale perspective and identified priority areas for thermal exposure interventions. Furthermore, a comparison was performed between daily thermal exposure and land surface temperature derived from remote sensing. The results indicated that thermal exposure interventions need to be prioritized in new development areas near the Third Ring Road. Additionally, top-down thermal exposure measurements may not accurately represent the daily thermal exposure experienced by pedestrians. Incorporating human-scale thermal exposure as another essential indicator can contribute to a more comprehensive analysis of thermal exposure in urban planning practice. In summary, the combined approach of spatial syntax and SVIs provides a promising paradigm for fine-grained thermal exposure assessment, which is an initial exploration of human-centered urban planning. • Solar duration is estimated by overlaying the solar path with hemispherical images. • Space syntax is utilized to measure walking accessibility. • A human-scale method is proposed to explore pedestrian daily thermal exposure. • Priority streets are determined by overlaying solar duration and accessibility. • Relying solely on land surface temperatures may cause bias. [ABSTRACT FROM AUTHOR]

P2-P3 series-parallel hybrid electric vehicles (HEVs) feature intricate topologies with multiple power sources and multiple working modes, posing a challenge for developing effective energy management strategies (EMSs). This paper introduces a framework that combines deep reinforcement learning (DRL) with pre-optimized energy management to address this challenge. Considering the characteristics of HEVs, the framework incorporates the pre-optimized equivalent motor and pre-optimized mode selection rule into a deep deterministic policy gradient (DDPG) loop. The pre-optimization of the equivalent motor aims to reduce the energy management task's dimensionality by equating two motors as the equivalent motor, while the pre-optimized mode selection rule systematically integrates mode selection and energy allocation into the EMS. The study assumes HEVs operate in connected urban environments and incorporates middle-horizon traffic information to enhance EMS performance. Additionally, the study integrates the frequent engine start-stop characteristics of HEVs into EMS design. Simulation results demonstrate that the fuel economy of the proposed EMSs in this study ranges from 87.2% to 90.7% of the DP-based EMS. The inclusion of an engine start-stop penalty significantly reduces the number of engine start-stops without compromising fuel economy. [Display omitted] • A pre-optimization-assisted DDPG-based EMS is designed for series-parallel HEVs. • Equivalent method regards two motors as one and reduces dimensionality of optimization. • Dynamic programming guides the pre-optimization of mode selection rule design. • Traffic information and engine start-stop events are considered in energy management. [ABSTRACT FROM AUTHOR]

In modern clinical medical practice, middle-ear infection is a frequently reported condition. If untreated, persistent inflammation caused by infection may lead to perforation of the mastoid process or other portions of the temporal bone. When the middle-ear abscess penetrates the surrounding bone and invades the mastoid process, it causes mastoiditis. Abnormal osseous fistulae were observed on the temporal bones of individuals M137 and M199, which were unearthed in Qufu Olympic Sports Center Cemetery in Qufu City, Shandong Province, and date to the Warring States to the Han Dynasty (475 BCE–220 CE). Microscopic observation and CBCT were used to examine the lesions. A differential diagnosis suggests that the lesions were related to mastoiditis, and based on reference studies, burial information, and paleopathological observation, pollution in the living environment and poor living conditions may be potential factors that caused individuals M137 and M199 to suffer from mastoiditis. The two examples from Qufu are the earliest reported cases of mastoiditis from China; however, infections in the middle ear often go unnoticed in archaeological samples. [ABSTRACT FROM AUTHOR]

Nanocomposite microparticle (nCmP) systems exhibit promising potential in the application of therapeutics for pulmonary drug delivery. This work aimed at identifying the optimal spray-drying condition(s) to prepare nCmP with specific drug delivery properties including small aerodynamic diameter, effective nanoparticle (NP) redispersion upon nCmP exposure to an aqueous solution, high drug loading, and low water content. Acetalated dextran (Ac-Dex) was used to form NPs, curcumin was used as a model drug, and mannitol was the excipient in the nCmP formulation. Box-Behnken design was applied using Design-Expert software for nCmP parameter optimization. NP ratio (NP%) and feed concentration (Fc) are significant parameters that affect the aerodynamic diameters of nCmP systems. NP% is also a significant parameter that affects the drug loading. Fc is the only parameter that influenced the water content of the particles significantly. All nCmP systems could be completely redispersed into the parent NPs, indicating that none of the factors have an influence on this property within the design range. The optimal spray-drying condition to prepare nCmP with a small aerodynamic diameter, redispersion of the NPs, low water content, and high drug loading is 80% NP%, 0.5% Fc, and an inlet temperature lower than 130°C. [ABSTRACT FROM AUTHOR]

Biocompatible, biodegradable polymers are commonly used as excipients to improve the drug delivery properties of aerosol formulations, in which acetalated dextran (Ac-Dex) exhibits promising potential as a polymer in various therapeutic applications. Despite this promise, there is no comprehensive study on the use of Ac-Dex as an excipient for dry powder aerosol formulations. In this study, we developed and characterized pulmonary drug delivery aerosol microparticle systems based on spray-dried Ac-Dex with capabilities of (1) delivering therapeutics to the deep lung, (2) targeting the particles to a desired location within the lungs, and (3) releasing the therapeutics in a controlled fashion. Two types of Ac-Dex, with either rapid or slow degradation rates, were synthesized. Nanocomposite microparticle (nCmP) and microparticle (MP) systems were successfully formulated using both kinds of Ac-Dex as excipients and curcumin as a model drug. The resulting MP were collapsed spheres approximately 1 μm in diameter, while the nCmP were similar in size with wrinkled surfaces, and these systems dissociated into 200 nm nanoparticles upon reconstitution in water. The drug release rates of the Ac-Dex particles were tuned by modifying the particle size and ratio of fast to slow degrading Ac-Dex. The pH of the environment was also a significant factor that influenced the drug release rate. All nCmP and MP systems exhibited desirable aerodynamic diameters that are suitable for deep lung delivery (e.g. below 5 μm). Overall, the engineered Ac-Dex aerosol particle systems have the potential to provide targeted and effective delivery of therapeutics into the deep lung. [ABSTRACT FROM AUTHOR]

Sulfate and phosphate, oxoanions common in natural systems, affect iron oxide growth and dissolution processes, the adsorption behavior of divalent cations, and iron oxide phase transformations. These oxoanions may thus influence Fe(II) adsorption behavior and subsequently alter the mechanisms and products of Fe(II)-catalyzed Fe(III) oxide recrystallization processes, such as trace metal repartitioning. In this study, the macroscopic and molecular-scale effects of the coadsorption of Fe(II) and sulfate or phosphate onto Fe(III) oxide surfaces were investigated. Macroscopic adsorption edges show that both sulfate and phosphate increase Fe(II) adsorption and that Fe(II) increases sulfate and phosphate adsorption. Attenuated total reflectance Fourier transform infrared spectroscopy shows that the cooperative adsorption behavior of oxoanions and aqueous Fe(II) likely results from a combination of ternary complexation and electrostatic interactions. Surface complexation modeling requires the inclusion of ternary complexes to simulate all conditions of the macroscopic data, further suggesting that these oxoanions and Fe(II) form ternary complexes on Fe(III) oxide surfaces. Despite clear evidence in previous research for Fe(II) oxidation upon adsorption on iron oxide surfaces, this work shows that Fe(II) also displays macroscopic and molecular-scale behaviors associated with divalent (i.e., non-oxidative) cation adsorption. Prior work has shown that metal release from iron oxides caused by ET-AE reactions is directly proportional to the macroscopically-determined Fe(II) surface coverage. Predicting the effects of sulfate and phosphate on processes controlled by ET-AE reactions at redox interfaces, such as mineral phase transformations and trace element repartitioning, may thus not require the explicit consideration of electron transfer processes. [ABSTRACT FROM AUTHOR]

Abstract: The longevity of subsurface U(IV) produced by reduction of U(VI) during in situ bioremediation can be limited by reoxidation to more mobile U(VI) species. Coupling of the biogeochemical cycles of U and Mn may affect the fate and transport of uranium. Manganese oxides can act as a powerful oxidant that accelerates the oxidative dissolution of UO2. This study investigated the physical and chemical factors controlling the interaction between UO2 and MnO2, which are both poorly soluble minerals. A multi-chamber reactor with a permeable membrane was used to eliminate direct contact of the two minerals while still allowing transport of aqueous species. The oxidation of UO2 was not significantly enhanced by MnO2 if the two solids were physically separated. Complete mixing of MnO2 with UO2 led to a much greater extent and rate of U oxidation. When direct contact is not possible, the reaction slowly progresses through release of soluble U(IV) with its adsorption and oxidation on MnO2. Continuously-stirred tank reactors (CSTRs) were used to quantify the steady-state rates of UO2 dissolution induced by MnO2. MnO2 dramatically promoted UO2 dissolution, but the degree of promotion leveled off once the MnO2:UO2 ratio exceeded a critical value. Substantial amounts of U(VI) and Mn(II) were retained on MnO2 surfaces. The total production of Mn(II) was less than that of U(VI), indicating that the fate of Mn products and their impact on UO2–MnO2 reaction kinetics were complicated and may involve formation of Mn(III) phases. At higher dissolved inorganic carbon concentrations, UO2 oxidation by MnO2 was faster and less U(VI) was adsorbed to MnO2. Such an inverse relationship suggested that U(VI) may passivate MnO2 surfaces. A conceptual model was developed to describe the oxidation rate of UO2 by MnO2. This model is potentially applicable to a broad range of water chemistry conditions and is relevant to other environmental redox processes involving two poorly soluble minerals. [Copyright &y& Elsevier]

Capillary gel electrophoresis is widely applied for determination of sequence and size of DNA, in which the sieving gel plays an unignorable role. Herein, a pore-size controllable hydrogel was synthesized in the capillary with two symmetrical tetrahedron-like macromonomers consisting of pentaerythritoltetra (succinimidylcarboxypentyl) polyoxyethylene (PS) and pentaerythritoltetra (aminopropyl) polyoxyethylene) (PA). By capillary electrophoresis of the DNA fragments with this hydrogel, it is found that a homogenous structure of hydrogel which is more suitable for the DNA separation can be achieved when the molecular weight of PA is approximate to that of PS. DNA fragments smaller than 1500 bp can be well resolved in this hydrogel within 13 min. More than 100 consecutive runs can be carried out in such a dynamically coated capillary before performance begins to degrade. Notably, such hydrogel can realize separation of dsDNA up to single base pair resolution and same length of dsDNA with 1 bp difference. [Display omitted] • A pore-size controllable hydrogel was synthesized in the capillary. • The DNA markers were well separated in the hydrogel. • Single base pair resolution was realized in capillary filled with this hydrogel. [ABSTRACT FROM AUTHOR]

The formation of carcinogenic N -nitrosamines from reactions between solvent amines and flue gas NO x is an important concern for the application of amine-based processes to capture CO 2 post-combustion. Using an advanced test rig with interconnected absorber and desorber units, we evaluated the importance for N -nitrosamine formation of the desorber relative to the absorber, and any synergism between the two units. Variations in desorber temperature and in flue gas composition indicated that N -nitrosamine formation from fresh monoethanolamine (MEA) occurred predominantly in the absorber. N -nitrosamine formation was driven by high NO 2 and O 2 flue gas concentrations, although NO also contributed. In contrast, N -nitrosamine formation from piperazine (PZ) was driven by reactions with nitrite in the heated desorber, and accelerated concurrent with nitrite accumulation. A complementary experiment simulating aged MEA solvent (high nitrite, 1.5% sarcosine as a proxy of secondary amine degradation products) suggested the desorber becomes an order of magnitude more important than the absorber for N -nitrosamine formation. For fresh MEA solvent, increasing the desorber temperature from 110 °C to 130 °C promoted thermal decomposition of N -nitrosamines, reducing N -nitrosamine accumulation rates two-fold. Compared to the test rig, the prevailing practice of using separate absorber columns and autoclave-like treatments to mimic desorber units predicted the direction, but underestimated the magnitude of N -nitrosamine formation. Because N -nitrosamine accumulation rates are the net result of competing formation and thermal decomposition processes, use of continuously cycling test rigs may be necessary to understand the impacts of different operating conditions. Image 1 • A test rig with absorber-desorber cycling evaluated nitrosamine formation. • Nitrosamine formation from fresh MEA was driven by NO x /O 2 in the absorber. • Nitrosamine formation from PZ and simulated aged MEA was driven by the desorber. • Using autoclaves to mimic desorber units underestimated nitrosamine formation. [ABSTRACT FROM AUTHOR]

Dry and wet deposition of sulfur and nitrogen contained air pollutants lead to increase of sulfur and nitrogen to the surface, causing acidification of surface water bodies and subsequent damage to aquatic and terrestrial ecosystems. Louisiana has abundant water resources and it is important to protect water resources from excessive atmospheric deposition of sulfur and nitrogen. However, the information for understanding sulfur and nitrogen deposition and adverse effects in Louisiana is limited. In this study, a source-oriented version of the Community Multi-scale Air Quality (CMAQ) model was used to simulate emission, formation, transport, and deposition of sulfur and nitrogen species in Louisiana in August 2011 to understand the forms and quantities of sulfur and nitrogen deposition due to wet and dry processes in Louisiana, to show the spatial and temporal variations of deposition fluxes, and to quantify the contributions of different sources to sulfur and nitrogen deposition. Aerosol phase sulfate (AeroSO 4 ) has the highest monthly total flux of 6 kg S/ha in wet deposition of sulfur. Major forms of sulfur dry depositions are AeroSO 4 (~1 kg S/ha) and SO 2 (~3 kg S/ha). Nitrogen deposition is mainly in forms of NO 2 , HNO 3 , NH 3 , and aerosol phase nitrate (AeroNO 3 ). Electric generating utilities (EGU) are the largest contributor to sulfur depositions with monthly total flux of 1.6 kg S/ha, followed by industry (1 kg S/ha) and upwind sources. On-road vehicles and industry are important to nitrogen (except ammonia) depositions with maximum contributions of 0.6 kg N/ha and 0.8 kg N/ha, respectively. The dominate source of ammonia is “Other” implicit sector including agricultural activities. [ABSTRACT FROM AUTHOR]

• The research history of dissolved Mn(III) in diverse research fields was discussed. • Review of the formation, speciation, and detection methods of dissolved Mn(III). • The coupled redox reactions involving dissolved Mn(III) need further investigation. The cycling processes of elemental manganese (Mn), including the redox reactions of dissolved Mn(III) (dMn(III)), directly and indirectly influences the biogeochemical processes of many elements. Though increasing evidence indicates the widespread presence of dMn(III) mediates the fate of many elements, its role may be currently underestimated. There is both a lack of clear understanding of the historical research framework of dMn(III) and a systematic overview of its geochemical properties and detection methods. Therefore, the primary aim of this review is to outline the understanding of dMn(III) in multiple fields, including soil science, analytical chemistry, biochemistry, geochemistry, and water treatment, and summarize the formation pathways, species forms, and detection methods of dMn(III) in aquatic systems. This review considers how the characteristics of dMn(III), the intermediate formed in the single-electron reaction processes of Mn(II) oxidation and Mn(IV) reduction, determines its participation in environmental geochemical processes. Its widespread presence in diverse water systems and active redox properties coupling with various elements confirm its significant role in natural elemental geochemistry cycle and artificial water treatment processes. Therefore, further investigation into the role of dissolved Mn(III) in aquatic systems is warranted to unravel unexplored coupled elemental redox reaction processes mediated by dissolved Mn(III), filling in the gaps in our understanding of manganese environmental geochemistry, and providing a theoretical basis for recognizing the role of dMn(III) role in water treatment technologies. [Display omitted] [ABSTRACT FROM AUTHOR]

A thorough understanding of the complex redox coupling among manganese, arsenic, sulfur and oxygen in subsurface environments is still obscured by their metastable intermediate valances and speciation. Arsenic sulfide minerals may be disturbed by natural or anthropogenic activities, and encounter oxidants such as oxygen and reactive trivalent Mn species, and how these abiotic interactions impact the mineral dissolution and transformation of arsenic and sulfur species, remains unknown. In this study, we investigated the effects of dissolved Mn(III) and manganite (γ-MnIIIOOH) on the dissolution behaviors of orpiment (As 2 S 3) and realgar (AsS) under anoxic and oxic conditions. Complementary control experiments were also performed with dissolved arsenite without reduced sulfur. Oxygen, dissolved Mn(III) or manganite did not induce the oxidation of dissolved arsenite within several weeks. Orpiment's initial dissolution is a non-redox process releasing of arsenite and sulfide, and the three above oxidants promoted the dissolution of orpiment by rapid oxidation of dissolved sulfide. However, only when both dissolved Mn(III) and dissolved oxygen were present, substantial accumulation of arsenate and sulfate were observed. These results suggested the critical role of sulfur species in abiotic arsenic transformation and a synergetic effect of Mn and oxygen on sulfur oxidation. In contrast to orpiment, the dissolution of realgar was a redox reaction that involved the oxidation of As(II) to As(III) and the direct releasing of sulfide, which could be promoted by both dissolved oxygen and manganite. The effect of dissolved Mn(III) and oxygen on the formation of arsenate and sulfate was also clearly observed during the dissolution of realgar. Despite of the slow abiotic oxidation of dissolved arsenite to arsenate in the presence dissolved Mn(III) and oxygen, the coexistence of sulfide could enable rapid accumulation of arsenate, accompanied by substantial transformation to sulfate. The evidence of thioarsenic species in these experiments provided a plausible explanation as an alternative pathway for the oxidation of the two elements by dissolved Mn(III). These results provide new insights for the Mn-As-S cycling in redox transition environments. [ABSTRACT FROM AUTHOR]

Cellulose nanocrystals (CNCs) foams have recently gained research interests because they are renewable, abundant, biodegradable and exhibit high surface area. However, the application of CNCs-based foams is still challenging, which is attributed to its lack of effective entanglements between the CNCs particles, thus lowering foam properties. In this study, a synergistic enhancement strategy was proposed, based on the in situ mineralization with hydroxyapatite (HAP) layer onto the CNCs surface, followed by a chemical crosslinking reaction. The physical and chemical structures of the composites were analyzed with SEM, STEM, XRD, FTIR, and TGA. By controlling the amount of coated HAP and the crosslinker, it is possible to manufacture a series of CNCs-based foams that are lightweight (50–75 mg/cm3), highly porous (~90%) with high water absorption (>1300%) and outstanding mechanical strength properties (as high as 1.37 MPa). Moreover, our study further indicated that these CNCs/HAP materials could increase the proliferation of rat osteoblast cells. The method developed in this study presents a novel approach to design improved networked CNCs foam, which has the potential to be used in thermal-retardant material, wastewater treatment, tissue engineering, and personal care applications. • Organic/inorganic composite was fabricated by in situ coating HAP onto CNCs surface. • Water stable CNCs/HAP foams were obtained using PMVEMA/PEG as crosslinking agent. • Mechanical, thermal and biological properties were enhanced with the proposed method. [ABSTRACT FROM AUTHOR]

Predicting the kinetics of heavy metal adsorption and desorption in soil requires consideration of multiple heterogeneous soil binding sites and variations of reaction chemistry conditions. Although chemical speciation models have been developed for predicting the equilibrium of metal adsorption on soil organic matter (SOM) and important mineral phases (e.g. Fe and Al (hydr)oxides), there is still a lack of modeling tools for predicting the kinetics of metal adsorption and desorption reactions in soil. In this study, we developed a unified model for the kinetics of heavy metal adsorption and desorption in soil based on the equilibrium models WHAM 7 and CD-MUSIC, which specifically consider metal kinetic reactions with multiple binding sites of SOM and soil minerals simultaneously. For each specific binding site, metal adsorption and desorption rate coefficients were constrained by the local equilibrium partition coefficients predicted by WHAM 7 or CD-MUSIC, and, for each metal, the desorption rate coefficients of various binding sites were constrained by their metal binding constants with those sites. The model had only one fitting parameter for each soil binding phase, and all other parameters were derived from WHAM 7 and CD-MUSIC. A stirred-flow method was used to study the kinetics of Cd, Cu, Ni, Pb, and Zn adsorption and desorption in multiple soils under various pH and metal concentrations, and the model successfully reproduced most of the kinetic data. We quantitatively elucidated the significance of different soil components and important soil binding sites during the adsorption and desorption kinetic processes. Our model has provided a theoretical framework to predict metal adsorption and desorption kinetics, which can be further used to predict the dynamic behavior of heavy metals in soil under various natural conditions by coupling other important soil processes. [ABSTRACT FROM AUTHOR]

High-input, modern rice farming (MRF) has caused severe soil degradation worldwide, necessitating a transition towards more sustainable practices. The traditional rice–fish coculture (RFC) and manure fertilization (Manure) may provide valuable insights to this transition. However, it remains elusive how long-term agricultural conversion influences microbial community structure, soil fertility, and food supply. Here, we performed six-year conversions of MRF to either RFC or Manure in a hilly area of Sichuan (China). We found that agricultural conversions exerted a greater impact than rice growing stages on bacterial community structure. The RFC bacterial network exhibited the highest modularity and robustness, but also harbored the most diverse keystone taxa, followed by Manure. In contrast, MRF displayed network properties that are characteristic of unstable communities. Importantly, RFC also exhibited the greatest capability in improving the preservation of soil organic carbon, nitrogen, and phosphorus, and has significantly increased soil pH (> 1.5 units). Yet, adopting traditional practices, particularly Manure, decreased rice yields, but fish harvested in RFC could offset the decrease in rice yield. Our field study highlights bacterial network structure and keystone taxa diversity as possible indicators for agriculture sustainability, but also incentivizes the integration of traditional RFC in developing novel sustainable agricultural practices. ● Rice–fish coculture (RFC) changes soil bacterial community and network structure. ● RFC increases bacterial network modularity and keystone taxa diversity. ● RFC is conducive to soil fertility recovery and soil organic matter preservation. [ABSTRACT FROM AUTHOR]

• Pyrophosphate increase the dissolution of arsenopyrite by the ligand-promoted effect. • The significant formation of •OH induced by pyrophosphate contribute to the oxidation of arsenite. • Dissolved Mn(III) consumes •OH and decrease the oxidation of arsenite. The oxidative dissolution of As from arsenopyrite, one important arsenic mineral in reducing conditions, poses an environmental hazard to natural aquatic systems. The dissolution of arsenopyrite occurs slowly due to the surface precipitates of iron oxides in circumneutral oxic environments. However, the presence of natural ligands and coexisting metals may change the release of Fe species, which would be of critical importance to the dissolution of arsenopyrite. Here, we investigated the oxidative dissolution of arsenopyrite induced by pyrophosphate (PP) and dissolved Mn(III) species as a natural occurring Mn species with strong complexation affinity to PP. With the presence of PP, the formation of Fe(II)-PP complexes and its rapid oxidation to dissolved Fe(III)-PP species resulted in a substantial increase in the generation of hydroxyl radicals (•OH) under ambient dark conditions, contributing to faster dissolution of arsenopyrite and higher percentage of As(V) in the dissolved products. Dissolved Mn(III), though considered as an extra oxidant besides oxygen, unexpectedly acted as a radical scavenger for •OH and inhibited the production of As(V). Moreover, the oxidation of sulfur species differed in the two systems as significant formation of thiosulfate was observed with the presence of PP, which did not occur in the system with dissolved Mn(III). Overall, the effects of dissolved Mn(III) and PP on the dissolution of arsenopyrite and the subsequent transformation of Fe, As and S species have important implications for disentangling the interactions among these metastable elements, and for assessing their transport and environmental impacts in aquatic systems. [Display omitted] [ABSTRACT FROM AUTHOR]

Phosphate addition is a potential treatment method to lower the solubility of U(VI) in soil and groundwater systems by causing U(VI) phosphate precipitation as well as enhancing adsorption. Previous work has shown that iron oxide surfaces may facilitate the nucleation of U(VI) phosphate minerals and, that under weakly acidic conditions, phosphate also enhances U(VI) adsorption to such phases. Like iron oxides, clays are important reactive phases in the subsurface but little is known about the interaction of U(VI) and phosphate with these minerals. The effect of aqueous phosphate on U(VI) binding to Wyoming montmorillonite (SWy-2) in air-equilibrated systems was investigated. Equilibrium U(VI) uptake to montmorillonite was determined at pH 4, 6 and 8 at discrete initial phosphate concentrations between 0 and 100 μM. The observed behavior of U(VI) indicates a transition from adsorption to precipitation with increasing total uranium and phosphate concentrations at all pH values. At the highest phosphate concentration examined at each pH value, a barrier to U(VI) phosphate nucleation is observed. At lower concentrations, phosphate has no effect on macroscopic U(VI) adsorption. To assess the mechanisms of U(VI)-phosphate interactions on smectite surfaces, U(VI) speciation was investigated under selected conditions using laser-induced fluorescence spectroscopy (LIFS) and extended X-ray absorption fine-structure (EXAFS) spectroscopy. Samples above the precipitation threshold display EXAFS and LIFS spectral signatures consistent with the autunite family of U(VI) phosphate minerals. However, at lower U(VI) concentrations, changes in LIFS spectra upon phosphate addition suggest that U(VI)-phosphate ternary surface complexes form on the montmorillonite surface at pH 4 and 6 despite the lack of a macroscopic effect on adsorption. The speciation of solid-associated U(VI) below the precipitation threshold at pH 8 is dominated by U(VI)-carbonate surface complexes. This work reveals that ternary complexation may occur without a macroscopic signature, which is attributed to phosphate not appreciably binding to smectite in the absence of U(VI), with U(VI) surface complexes serving as the sole reactive surface sites for phosphate. This study shows that phosphate does not enhance U(VI) adsorption to smectite clay minerals, unlike oxide phases, and that a barrier to homogeneous nucleation of U(VI) phosphates was not affected by the presence of the smectite surface. [ABSTRACT FROM AUTHOR]

• Oxidative dissolution of Sb 2 O 3 was promoted in the presence of Mn(II) at pH 9. • Amorphous MnO x was formed through the surface-catalytic Mn(II) oxidation by DO. • Generation of Mn(III) is a critical step in MnO x formation. • Valentinite and senarmontite showed distinct facet-dependent dissolution patterns. • Sb(V) was partially retained on MnO x through bidentate–binuclear complexes. Antimony trioxide (Sb 2 O 3) is one of the primary forms of Sb in the environment, and its dissolution significantly impacts the migration and bioavailability of Sb. However, the dissolution of Sb 2 O 3 coupled with abiotic redox of Mn processes is unclear. Here, we investigated the kinetics of Sb 2 O 3 dissolution in the presence of the ubiquitous Mn(II) by kinetic experiments, spectroscopies, density functional theory calculations and the chemical kinetic modeling. The oxidative dissolution of Sb 2 O 3 was catalyzed by Mn(II) through the in-situ generated amorphous Mn oxides (MnO x) under oxic conditions, during which the generation of Mn(III) is a critical step in Sb(V) release. The released Sb(V) was partially retained on MnO x through bidentate-binuclear (corner-sharing) complexes as revealed by extended X-ray absorption fine structure analysis. The coexistent morphological forms of Sb 2 O 3 , i.e., senarmontite and valentinite exhibited distinct dissolution patterns. Valentinite showed higher activity in catalyzing Mn(II) oxidation and faster oxidative dissolution than senarmontite, due to its higher surface energy and lower conduction band minimum of its exposed facets. These abiotic processes can extrapolate to other metal(loid)s (hydr)oxides, further supplying for the comprehensive understanding of the redox transformation of Mn [Display omitted] [ABSTRACT FROM AUTHOR]