Subsequent Precipitation Research Articles

Facile design of the nanofiltration membrane with Cu2+-incorporated aminated polyethylene substrate for highly selective magnesium/lithium separation

Efficient separation of magnesium and lithium ions (Mg2+/Li+) from high Mg2+/Li+ ratio salt-lake brines using nanofiltration (NF) technology is crucial for stabilizing lithium resources in light of the increasing demand for lithium-based products. Although positively charged NF membranes show promise in selectively separating Mg2+ and Li+ ions, the issues of inefficiency and undesirable trade-offs in perm-selectivity remain pressing. In this study, we presented a breakthrough in creating a highly permeable NF membrane tailored for selective Mg2+/Li+ separation using the cost-effective polyethylene (PE) as the substrate for the preparation of the NF supporting layer. Employing a facile and low-cost Cu2+-incorporated amination process, the hydrophilization of PE substrate was accomplished. This innovative Cu2+-incorporated amination technique not only facilitated rapid hydrophilization but also established a positively charged PE surface while simultaneously regulating the formation of a thinner and loose polyethyleneimine (PEI)-based polyamide (PA) skin layer (∼26 nm) through the coordination bonding between the Cu2+ and amine groups. Consequently, the resultant NF membrane achieved simultaneous enhancements in permeability (∼16 L m−2 h−1 bar−1) and selectivity for Li+/Mg2+ (33) during the nanofiltration of the simulated brine, effectively reducing high Mg2+/Li+ ratios in the feed close to 1 in the permeate, and making it suitable for the subsequent precipitation to produce Li2CO3. Furthermore, this membrane demonstrated remarkable long-term stability, with stable NF operation continuously for over 7 days, owing to its robust Cu2+-induced aminated PE supporting layer and PEI-based PA skin layer. Our work underscores the simplicity and cost-effectiveness of the Cu2+-incorporated amination process in achieving superior PE-based NF membranes, specifically targeting lithium extraction from salt-lake brines.

An investigation of the source of calcium carbonate from the carbonated Portland cement: Based on the transformation of hydrates

In this work, two PC pastes were used to carry out accelerated carbonation experiments, and phase assemblages of paste samples collected at different sampling depths were analyzed. The source of CaCO3 originating from the carbonation reaction of hydrates in cement was quantitatively determined by a novel method based on the transformation of hydrates. Experimental results indicated that the phase assemblages in the carbonated zone of two PC pastes showed minor differences. C(A)SH, ettringite, AFm-CO3, and unhydrated cement particles in the complete carbonation zone of two cement pastes were carbonated and transformed into other phases. For the surface of two PC pastes (0–3 mm), calculations showed that the CaCO3 originating from the carbonation of calcium hydroxide and C(A)SH accounted for 75.3% and 72.6% of the total CaCO3, respectively. A concentration of 20% CO2 was not beneficial for the diffusion of CO2 and the subsequent precipitation of CaCO3 at the later period of carbonation.

Mechanism of Opal-CT deposit from the Lam Narai Volcanics in Lop Buri, Thailand by using Petrography

Common opals were discovered in the rhyolite host rock, where various structural features such as cavities, fractures, and veins are observed. These voids served as pathways for the infiltration of silica-rich fluids originating from meteoric water, establishing a hydrothermal connection. The aqueous solution derived from meteoric water actively dissolves silica from the rhyolite host rock, thereby increasing the silica saturation within the fluid. Subsequently, the silica-saturated hydrothermal fluid fills the cavities and veins within the host rock. The margin of the host rock underwent alteration as it interacted with infiltrating hydrothermal fluid in a phenomenon known as hydrothermal fluid-rock interaction. At the periphery of the cavities, quartz crystals begin to form, effectively reducing the concentration of dissolved silica in the solution. As a result, the subsequent precipitation of amorphous opals occurs, predominantly within the inner part or central region of the vein or cavity. The formation of opals associated with Lam Narai volcanic activity occurred at a relatively high temperature of about 105-170 °C through a hydrothermal process.

High-cellulose content of in-situ Miocene fossil tree stumps and trunks from Lusatia lignite mining district, Federal Republic of Germany

Second Miocene Seam Complex (2nd MFK; germ.: 2. Miozäner Flözkomplex) holds many in-situ, not permineralised fossil tree stumps and trunks with high-cellulose contents. The state of preservation of a set of in-situ fossil trees (Taxodioxylon cryptomerioides, Sciadopityoxylon wettsteinii, and Quasisequoioxylon piskowitzense) collected from three open-cast mines (Welzow-Süd, Meuro, and Piskowitz) in Lusatia lignite mining district, Federal Republic of Germany was investigated using a multi-method research schema.Examination of preservation state of thermally immature fossil woods revealed: (1) well-preserved (non-deformed, non-degraded, and non-flattened) textinite, (2) a retained structural integrity represented by multilayered (multi-zoned) cells with primary, secondary cell wall, and middle lamella, (3) microfracturing restricted to secondary walls only, (4) preservation of polyphenolic parenchyma cells (PP cells), (5) excellent preservation of pits in ray tracheids, (6) presence of amorphous silica (opal-A) coating, and (7) crystalline silica (opal-CT) fillings of small-bladed crystals.Thermogravimetric analysis results showed dissimilar gelification status of fossil samples, supporting chlorite holocellulose assay results. The latter indicated anomalously high-cellulose values (15.6–37.6% holocellulose). The micro-FTIR data obtained revealed an excellent preservation of both hemicellulose (bands at 1740 and 1245 cm−1) and cellulose (bands at 1110 and 1040 cm−1). Micro-FTIR spectrometry indicated lack of preferential hydrolytic removal of polysaccharides in examined samples.Biomarker patterns in lignite revealed forested and prevailing reed-mire vegetation. The results indicated lower contribution of Cupressaceae and emergent macrophyta to precursor organic matter of Welzow-Süd in comparison to Piskowitz lignite. Piskowitz lignite formed in permanent mire with stable water table under reducing, mesotrophic conditions. In contrast, more pronounced water level fluctuations (reducing to slightly oxic settings) and/or post-depositional events are postulated for Welzow-Süd samples.Biomarker assemblages obtained from fossil wood show a distinct dominance of diterpenoids and δ13C values (−24.6 ‰ to −20.3 ‰) that clearly confirm gymnosperm sources. Distributions of diteprenoids and sesquiterpenoids, as well as fatty acids indicate the higher amount of saturated diterpenoids (pimarane, abietane) in fossil than in modern wood. This indicates reducing conditions promoting hydrogenation reactions. In addition to low Eh, preservation of cellulose in fossil wood was also favored by acidic conditions, very low degrees of aerobic fungal degradation, and protection of wood by Cupressaceae-derived resins.While δ13C values of fossil wood are generally consistent with stratigraphic trends and chemotaxonomical classification, slightly elevated δ13C values recorded in T. cryptomerioides and S. wettsteinii in Welzow-Süd and Meuro open-cast mines, respectively, compared to published δ13C data of fossil gymnosperm wood are also indicative for good cellulose preservation.Both preservation of in-situ Miocene fossil stumps and trunks and retention of high-cellulose contents are suggested to be related to high-amplitude temporal fluctuations associated with repeated eustatically-controlled wet-dry cycling inducing: (1) weathering of tuff- and rhyolite-dominated acidic volcanics and Lausitz granodiorite, (2) associated erosion of saprolites, and (3) peat-sourced circulation of humic acid- and fulvic acid-rich waters. The latter led to the formation of Middle Miocene kaolinite deposits, as well as to the release of silicic acid and its subsequent precipitation in form of opal-A. The latter influenced preservation of high-cellulose contents in fossil wood.

Possible Role of High-Molecular-Weight Salivary Proteins in Astringency Development.

Since the initial findings that food tannin/salivary protein interaction and subsequent precipitation is the main cause of the astringency development, numerous studies have concentrated on the supramolecular characterization of these bindings. Most of these works have focused on the low-molecular-weight salivary proteins, in particular proline-rich proteins, hardly considering the involvement of the high-molecular-weight salivary proteins (HMWSPs). Herein, different techniques such as fluorescence quenching, Isothermal Titration Calorimetry and HPLC-MS-DAD were employed to determine the occurrence of molecular interactions between three HMWSPs, namely, mucin, α-amylase and albumin, and a complex extract of tannins composed mainly of flavan-3-ols. The obtained results prove the capability of the three HMWSPs to effectively interact with the flavan-3-ol extract, involving different forces and action mechanisms. Flavan-3-ols are capable of interacting with mucins by a mechanism that includes the formation of stable ground-state complexes that led to approximately 90% flavan-3-ol precipitation, while for albumin and α-amylase, the interaction model of a "sphere of action" was established, which represented only 20% flavan-3-ol precipitation. These data highlight the relevance of including HMWSPs in astringency analyses, paying special heed to the role of mucins in the interaction and subsequent precipitation of dietary tannins.

Assessment of the Spraying System Impact at the Preparation Stage of Iron Ore Concentrate Products

Introduction. Harmful components of ore dust, formed during the unloading of products in the preparation of iron ore concentrate (PPIOC) at the mixing stage, cause damage to both workers and equipment. To address this issue, liquid aerosol spraying using nozzles with large diameters (>20 μm) is used. However, this method proves ineffective in capturing fine-dust particles. Therefore, enhancing the efficiency of the dust deposition method through PPIOC dust spraying becomes a pressing challenge. The aim of this study is to investigate the impact of the Dry Fog technology, generating liquid droplets up to 20 μm in size, during the unloading stage of PPIOC at a mining and metallurgical enterprise in the precipitation of suspended fine-dust particles. The primary goal of this research was to assess the effectiveness and potential advantages of applying the Dry Fog technology for dust spraying with subsequent precipitation, as this technology has not been previously applied to PPIOC dust.Materials and Methods. The experiment on the PPIOC dust deposition was conducted in a specially designed laboratory setup. Through physical modeling in the laboratory setup, parameters of the precipitation process were obtained. Subsequently, the results were analyzed to understand the dependence of dust precipitation over time, taking into account the influence of the Dry Fog technology. An experiment program was developed for physical modeling. According to the devised program, dust was uniformly loaded into the interior of the laboratory setup (from the top), distributed in the air stream throughout the volume of the setup by a fan, and an instrument located at the bottom recorded changes in concentration over time. Experiments on dust precipitation were then conducted using liquid spraying (filtered water as the liquid) introduced into the setup through nozzles generating droplets with sizes of 10 and 15 μm, concurrently with the loading of dust into the laboratory setup. The effectiveness of the Dry Fog technology in the deposition of PPIOC dust was determined visually and further analyzed based on a comparison of graphs. The dynamics of changes in the average dust concentrations depending on time was studied both during precipitation without spraying and using the Dry Fog technology. During the experiment, the characteristics of the microclimate inside the laboratory setup (humidity, temperature and air velocity) and the parameters of two nozzles — their operating pressure and the supplied liquid spraying time — were recorded.Results. The comparison of the results showed a reduction in the dust precipitation time by 40 % and 75 % when using nozzles with sizes of 10 μm and 15 μm, respectively.Discussion and Conclusion. The experiment results confirm the effectiveness of the Dry Fog technology for PPIOC dust precipitation during unloading at the mixing stage. Fundamental findings have been obtained, providing a basis for further assessment of the efficiency of dust precipitation with the additional application of pulsating ventilation. In such a combination, an additional 20–25 % increase in precipitation efficiency is anticipated compared to the results presented in this article. The obtained results will support the justification of rational parameters and the implementation of the described method in production to enhance dust precipitation efficiency. Additionally, they will aid in developing a methodology to accelerate the PPIOC dust precipitation using the pulsating ventilation method.

Encapsulating carboxymethyl cellulose stabilized nanoscale ferrous sulfide with layered magnesium hydroxide shell for controlled reactivity release and long-term sequestration of Cr(Ⅵ)

Nanoparticulate iron sulfide (nano-FeS) is a highly effective and environmentally-friendly reducing agent for decontamination. However, challenges such as aggregation, poor mobility, and oxidative aging limit its application of in situ groundwater and soil remediation. Herein, we present a novel approach to enhance the feasibility and effectiveness of nano-FeS for in situ remediation by encapsulating carboxymethyl cellulose stabilized FeS nanoparticles with a layered magnesium hydroxide shell (referred to as CMC-FeS@Mg(OH)2). The novel CMC-FeS@Mg(OH)2 nanoparticles, with a suitable coating ratio (10 %–50 %), demonstrate considerably increased colloidal stability and enhanced mobility in porous media. This is mainly due to steric hindrance, and decreased attachment, blocking, and straining effects. The Mg(OH)2 shell obviously protects the reactivity of FeS nanoparticles and enhances their resistance to oxidation, ensuring their longevity and long-term decontamination effectiveness during practical field applications. The preserved reactivity of FeS core can be progressively released and fully recovered by modulating the Mg(OH)2 coating ration and the extent of dissolution. After the complete dissolution of the Mg(OH)2 shell, CMC-FeS@50 % Mg(OH)2 exhibits enhanced efficiency in Cr(VI) sequestration, increasing from 58 % to 92 % compared to bare FeS. The removal of Cr(VI) by CMC-FeS@Mg(OH)2 is a synergistic process, and the main mechanisms includes adsorption, reduction, ion exchange, and subsequent precipitation. These results demonstrate a promising and effective method to improve the mobility and longevity of FeS and enable the controlled reactivity release for in situ remediation of subsurface contamination.

Effect of Lipid Corona on Phenylalanine-Functionalized Gold Nanoparticles to Develop Stable and Corona-Free Systems.

Conventional gold nanoparticles (Au NPs) have many limitations, such as aggregation and subsequent precipitation in the medium of high ionic strength and protein molecules. Furthermore, when exposed to biological fluids, nanoparticles form a protein corona, which controls different biological processes such as the circulation lifetime, drug release profile, biodistribution, and in vivo cellular distribution. These limitations reduce the functionality of Au NPs in targeted delivery, bioimaging, gene delivery, drug delivery, and other biomedical applications. To circumvent these problems, there are numerous attempts to design corona-free and stable nanoparticles. Here, we report for the first time that lipid corona (coating of lipid) formation on phenylalanine-functionalized Au NPs (AuPhe NPs) imparts excellent stability against the high ionic strength of bivalent metal ions, amino acids, and proteins of different charges as compared to bare nanoparticles. Moreover, this work is focused on the ability of lipid corona formation on AuPhe NPs to prevent protein adsorption in the presence of cell culture medium (CCM), oppositely charged protein (e.g., histone 3), and human serum albumin (HSA). The results demonstrate that the lipid corona successfully protects the AuPhe NPs from protein adsorption, leading to the development of corona-free character. This unique achievement has profound implications for enhancing the biomedical utility and safety of these nanoparticles.

Direct Recycling of β‐Li3PS4‐Based All‐Solid‐State Li‐Ion Batteries: Interactions of Electrode Materials and Electrolyte in a Dissolution‐Based Separation Process

All‐solid‐state batteries (ASSB) are currently developed at high pace and show a strong potential for market introduction within the next years. Though their performance has improved considerably over the last years, investigation of their sustainability and the development of suitable recycling strategies have received less attention. However, their potential for efficient circular processes must be accessed comprehensively. In this article, the separation of the solid electrolyte β‐Li3PS4 from different lithium transition metal oxide electrode materials (LiCoO2, LiMn2O4, LiNi0.8Mn0.1Co0.1O2, LiFePO4, LiNi0.8Co0.15Al0.05O2, and Li4Ti5O12) are investigated via an approach based on the dissolution and subsequent precipitation of the thiophosphate using N‐methylformamide as solvent. A combination of X‐ray diffraction, scanning electron microscopy, energy‐dispersive X‐ray spectroscopy, inductively coupled plasma mass spectrometry, iodometric titration, and X‐ray photoelectron spectroscopy as well as electrochemical impedance spectroscopy and electrochemical characterization is used to characterize the electrolyte and electrode materials before and after separation. Herein, it is found that the presence of electrode materials in the dissolution process can lead to significant chemical reactions. These interactions can (but most not) lead to strong alteration of the electrochemical characteristics of the individual compounds. Thus, it is shown that an efficient recovery of materials likely depends on the precise material combination within an ASSB.

Effect of Microstructure on the Precipitation of β-Mg2Si during Cooling after Homogenisation of Al-Mg-Si Alloys

For Al-Mg-Si alloys, cooling after homogenisation is a crucial step because the precipitation of the equilibrium β-Mg2Si phase determines the processing capabilities in subsequent steps, as well as the subsequent precipitation age hardening potential, and thus, the final properties. It is therefore important to understand how microstructural variations affect the transformation of β-Mg2Si during cooling after homogenisation. In the present work, alloys with similar effective solute contents of Mg and Si, but with different microstructures and a different amount of primary Al-Fe-Si phases, were produced. Characterisation of the precipitation reaction was performed using interrupted quench experiments with cooling rates of 1–6 K/min, monitored by light optical microscopy (LOM), scanning electron microscopy (SEM) and conductivity measurements. Precipitation kinetics for β-Mg2Si was found to increase in microstructures with shorter secondary dendrite arm spacing (DAS). However, despite measuring both a higher density and volume fraction of the primary phases, no effect on the phase transformation from an increased iron content was found in terms of precipitation kinetics or particle count statistics. Furthermore, comparisons with iron-free high-purity-based alloys revealed that the precipitation reaction for β-Mg2Si was identical in the two different microstructures both in terms of onset temperature and overall kinetics. The present results show that nucleation of β-Mg2Si is not dependent on the larger constituent phases and indicates that overall transformation kinetics is governed by bulk diffusion rates.

Phase-field chemo-mechanical modelling of corrosion-induced cracking in reinforced concrete subjected to non-uniform chloride-induced corrosion

A model for corrosion-induced cracking of reinforced concrete subjected to non-uniform chloride-induced corrosion is presented. The gradual corrosion initiation of the steel surface is investigated by simulating chloride transport considering binding. The transport of iron from the steel surface, its subsequent precipitation into rust, and the associated precipitation-induced pressure are explicitly modelled. Model results, obtained through finite element simulations, agree very well with experimental data, showing significantly improved accuracy over uniform corrosion modelling. The results obtained from case studies reveal that crack-facilitated transport of chlorides cannot be neglected, that the size of the anodic region must be considered, and that precipitate accumulation in pores can take years.

Water‐rock interactions drive chemostasis

AbstractThe western U.S. is experiencing shifts in recharge due to climate change, and it is currently unclear how hydrologic shifts will impact geochemical weathering and stream concentration–discharge (C–Q) patterns. Hydrologists often use C–Q analyses to assess feedbacks between stream discharge and geochemistry, given abundant stream discharge and chemistry data. Chemostasis is commonly observed, indicating that geochemical controls, rather than changes in discharge, are shaping stream C–Q patterns. However, few C–Q studies investigate how geochemical reactions evolve along groundwater flowpaths before groundwater contributes to streamflow, resulting in potential omission of important C–Q controls such as coupled mineral dissolution and clay precipitation and subsequent cation exchange. Here, we use field observations—including groundwater age, stream discharge, and stream and groundwater chemistry—to analyse C–Q relations in the Manitou Experimental Forest in the Colorado Front Range, USA, a site where chemostasis is observed. We combine field data with laboratory analyses of whole rock and clay x‐ray diffraction and soil cation‐extraction experiments to investigate the role that clays play in influencing stream chemistry. We use Geochemist's Workbench to identify geochemical reactions driving stream chemistry and subsequently suggest how climate change will impact stream C–Q trends. We show that as groundwater age increases, C–Q slope and stream solute response are not impacted. Instead, primary mineral dissolution and subsequent clay precipitation drive strong chemostasis for silica and aluminium and enable cation exchange that buffers calcium and magnesium concentrations, leading to weak chemostatic behaviour for divalent cations. The influence of clays on stream C–Q highlights the importance of delineating geochemical controls along flowpaths, as upgradient mineral dissolution and clay precipitation enable downgradient cation exchange. Our results suggest that geochemical reactions will not be impacted by future decreasing flows, and thus where chemostasis currently exists, it will continue to persist despite changes in recharge.

Countercurrent preferential precipitation of acidic variants from monoclonal antibody pools

The process of countercurrent multistage precipitation (CnMP) was developed for reduction of the acidic variant (av) content in monoclonal antibody (mAb) pools. The process was performed in polyethylene glycol (PEG) solutions of low ionic strength, at which av was the most prone to precipitate. To design the process, a mathematical model was formulated, which consisted of steady-state mass balance equations and underlying thermodynamic dependencies. The model was solved for different combinations of the process variables, including the protein concentration in the feed material and the PEG concentration in subsequent precipitation stages. The model solution was projected onto two-dimensional planes, where the performance indicators, such as the separation yield and the av reduction level, were correlated with the process variables. CnMP overperformed crosscurrent multistage precipitation (CsMP) and ion exchange chromatography (IEX) used in previous studies; in the comparison with CsMP, the 3-stage CnMP process allowed up to 28% increase in yield and up to 25% increase in the av reduction level, and in the comparison with IEX, up to 37% increase in yield and up 12.5% increase in the av reduction level. The yield benefit of CnMP depended on the composition of the feed material and the demand for the av reduction. The concept was experimentally verified; the 2- and 3-stage CnMP processes were performed using the input process variables provided by the model solution. The performance indicators calculated by the model and experimentally measured were in a good agreement, which indicated both feasibility and predictability of CnMP.

Effect of Temperature and Ageing on Fracture Toughness of Alloy 617M

In recent years, Advanced Ultra Super Critical (AUSC) plants have used Ni-Cr-Co-Mo based alloy 617M for high-temperature components like steam piping and rotors, where material resistance against fracture after prolonged exposure in a hostile environment is a matter of concern to the designers. To this end, fracture toughness characterization of the material in as-received and aged conditions using an elastic-plastic fracture mechanics (J-R curves) approach can provide a significant input towards the component integrity assessments at service conditions. In this study, J-R curves of the alloy 617M have been determined for the as-received and differently aged (up to 20000 h at 710 °C) conditions using compact tension (CT) specimens following ASTM E 1820-13. Repeated tests have been carried out at temperatures 27 °C, 650 °C, 710 °C and 750 °C. The fracture toughness (JIC) thus determined, has shown a declining trend with test temperatures. This attributes to the ease of the crack initiation process owing to the γ′ induced matrix hardening and subsequent ageing-inducing precipitations of M23C6 carbides at the grain boundaries.

Dissolution and recovery of poly(3-hydroxybutyrate) in switchable solvents and the formation of a switchable gel

Poly(3-hydroxybutyrate) (PHB), a bio-produced and biodegradable polymer, has great potential as a replacement for petroleum-based polymers in many applications. However, strategies for the extraction and processing of PHB still require improvement. Switchable solvents, which can be toggled between hydrophobic and hydrophilic forms by the addition or removal of carbon dioxide in the presence of water, are easily recyclable and may improve PHB processing methods. Here, we have shown the ability to dissolve PHB in two switchable solvents (N,N-dimethylbenzylamine and N,N-dimethylcyclohexylamine), precipitate PHB by the addition of water and carbon dioxide, and recycle the solvent for subsequent dissolution and precipitation cycles. We have also demonstrated the ability for N,N-dimethylbenzylamine to form gels with PHB which maintain their water/solvent content as the solvent is switched to a hydrophilic form. These results demonstrate the usefulness of switchable solvents as a recyclable platform for PHB processing and their ability to create unique materials.

Influence of the Southern Indian Ocean Dipole on the following spring climate in China: A synthetic observational and numerical study

The influence of the Southern Indian Ocean Dipole (SIOD) on the following spring climate in China is examined, using a 42-year simulation of the Community Earth System Model, version 1.0.4 (CESM1.0.4) and 42-year observation-based ocean-atmosphere analyses (1979–2021). It is shown that the SIOD, an inverse phase pattern of SST anomalies (SSTAs) in the southwest and northeast of the Southern Indian Ocean (SIO), is the dominant mode of observed interannual variability. Composite analyses based on observational data suggest that when a positive SIOD signal occurs, the surface temperature in the ensuing spring is warmer in southwest China and colder in northeast China, and the precipitation in southeast China decreases significantly. The response phase of the surface temperature and precipitation in China under a negative SIOD signal is the opposite of that under a positive SIOD signal, and the response intensity is also greater under a negative SIOD signal. Numerical experiments with CESM can also well reproduce the distribution of the surface temperature and precipitation the following spring over China under positive and negative SIOD signals, respectively. Analysis of the mechanism by which the SIOD influences the subsequent precipitation in China shows that it may occur through interaction between the mid to high latitudes and low latitudes, as well as upper and lower tropospheric circulations. During negative SIOD years, due to the remote response generated by the boreal winter SSTA in the SIO, a strong positive anomaly at 500 hPa geopotential height extending from northeast China to the northwest Pacific Ocean at mid to high latitudes corresponds to a significant low pressure in south and northwest China, and this low pressure helps southerly winds bring more water vapor to southeast China. Meanwhile, the westward extension and northward elevation of the western Pacific subtropical high lead to the convergence of water vapor in south China. In addition, westerly anomalies over the equatorial Indian Ocean and easterly anomalies over the equatorial western Pacific change the local Walker circulation, which weakens the northwest Pacific anticyclonic circulation and subtropical westerly jet. The abnormally warm SST in the southern equatorial Indian Ocean promotes the formation of the Hadley circulation, enhances the upward movement, and changes the water vapor convergence in south China. These factors together lead to an increase in precipitation in southeast China in the following spring in both observations and CESM numerical experiments. At the same time, during positive SIOD years, both observations and simulations show that the causes affecting precipitation are almost the opposite of those in negative SIOD years. Therefore, the SIOD during boreal winter can be an important predictor of precipitation variability over south and southeast China during the following spring.

An interdecadal change in the relationship between May North Atlantic oscillation and early summer precipitation over the Eastern Tibetan Plateau around the late 1990s

Based on the observational and reanalysis datasets, a dipole pattern of the early summer (June) precipitation over the eastern Tibetan Plateau (TP) is identified through empirical orthogonal function. In contrast to previous researches, this paper introduces the May North Atlantic Oscillation (NAO) as a preceding signal and investigates its connection with subsequent early summer precipitation over the eastern TP during 1980–2019, focusing on predictive aspects. Results reveal that the correlation between NAO and primary eastern TP precipitation pattern (Precip_EOF1) has weakened since 2000. During 1980–2000, an equivalent barotropic Silk Road Pattern (SRP) observed across Eurasia triggers southerly wind anomalies over the TP. This, in turn, leads to the northward shift of the water vapor, which favors the ascending motion over the northern TP (NTP) due to water vapor convergence. Additionally, the SRP-related sensible heating also plays a critical role in vertical motion over the eastern TP by enhancing the TP thermal effect. Consequently, these factors contribute to shaping the dipole pattern of eastern TP precipitation. However, the weakened relationship between NAO and Precip_EOF1 during 2001–2019 is attributed to the absence of NAO-related atmospheric circulation over Eurasia. Further analysis suggests that these circulation anomalies arise from the interdecadal variability of the NAO and its phase shift. Moreover, when the influence of sea surface temperature anomalies over the northern North Atlantic is removed, the correlation of Precip_EOF1 with NAO and Atlantic Multidecadal Oscillation (AMO) both become insignificant. This suggests that the NAO-related dipole pattern of eastern TP precipitation is modulated by preceding northern North Atlantic sea surface temperature rather than AMO on the interdecadal timescale.

Ferric Oxyhydroxylsulfate Precipitation Improves Water Quality in an Acid Mining Lake: A Hydrogeochemical Investigation

Hydrogeochemistry of a lignite pit lake in Lusatia, Germany, was investigated. Anoxic groundwater from the dump aquifer rich in FeII (average ~5911 µmol/L) and SO4 (average ~14,479 µmol/L) contents enter the lake as subsurface inflow; oxidation and subsequent precipitation of poorly crystallized Fe-oxyhydroxysulfate (schwertmannite) occurs and causes acidification (pH~2.8). However, the removal of dissolved loads as solid phases significantly improves the groundwater quality of the downgradient as an outflow. The rainwater isotopic values (δD ~−8.88‰ and δ18O ~−65.86‰) closely matched with the groundwater showing very little isotopic modification, which points to a short residence time of groundwater. The displacement of δD and δ18O values (slope = 5.3) from the meteoric water line reflected the evaporative enrichment of the lake water. The isotopic signature also revealed longer residence times of epilimnion than the hypolimnion waters which are dominated by groundwater. The lake is dimictic and showed abrupt changes in physicochemical parameters along the interface (~0.30 m thick) when separating the epilimnion (upper 4 m) from the hypolimnion (bottom 1.5 m). Lake sediments were found to be dominated by clay size fraction occurring as laminations (thickness: 1~0.5 mm) that reflect seasonal sedimentation. Higher schwertmannite formation in the south as compared to the north (recharge side) also serves as a scavenger of potentially toxic elements which is probably a natural solution to man-made problems. Schwertmannite transformation to goethite releases sulfate which is reduced and fixed as secondary sulfide minerals over time. Overall, waters are of a Ca–SO4 to Ca–Mg–SO4 type with distinct inflow (FeII/FeIII > 2.5) and outflow (FeII/FeIII < 0.5) of groundwater.

The influence of natural aging on the precipitation behavior of the low-alloy content Al-Zn-Mg aluminum alloys during subsequent artificial aging and related mechanisms

The age hardening and precipitation behavior of the low-alloy content and widely used Al-Zn-Mg alloy during artificial aging was studied adopting methods of Vickers hardness testing and transmission electron microscopy. To meet with practical application of the production line conditions, the influence of natural aging (NA, at room temperature) on the precipitation behavior during subsequent artificial aging (AA, at 130 °C∼150 °C) and related mechanisms are discussed based on the classical nucleation theory. The results show that precipitates like solute clusters and GP zones will form during the NA process, which have a significant influence on the subsequent precipitation behavior during AA. These NA precipitates will dissolve at the initial stage of AA resulting in abundant localized supersaturated regions which are the favorable nucleation sites for η′ phase. This positive effect is highly dependent on the temperature adopted during the AA process and the duration of NA. Higher AA temperatures result in a more noticeable increase in hardness compared to the samples without NA but require a longer duration of AA to achieve a relatively high and stable peak-aging hardness. However, an excessive long NA period can lead to a significant drop in hardness in the over-aging status. In the low-alloy content Al-Zn-Mg alloys, the actual nucleation rates of precipitation during the early stages of AA vary significantly with the AA temperature, which serves as the underlying cause of the observed NA effect. These results provide rather an important guidance for the production process of the 7003alloy and other aluminum alloys with similar chemical composition.

Decadal Enhancement in the Effect of El Niño in the Decaying Stage on the Pre–Flood Season Precipitation over Southern China

Abstract The abundant precipitation over Southern China during the pre–flood season (PFS) [i.e., April–June (AMJ)] has important socioeconomic impacts on this densely populated region. Using observational and reanalyzed datasets, this study explores how El Niño affected the subsequent PFS precipitation over Southern China during 1961–2020. The results show that the El Niño–related anomalies in sea surface temperature forced a northwestern Pacific anomalous anticyclone (NPAAC) in the decaying AMJ. This NPAAC featured southwesterly wind anomalies in its northwestern flank, which could transport moisture from the South China Sea, and accompanying the NPAAC there was abnormal descending motion over the tropical western Pacific, resulting in weakened regional Hadley circulation with abnormal ascending motion over subtropical East Asia. Before the 1990s, this abnormal ascending motion was located mainly to the east of Southern China with insignificant impacts on the PFS precipitation there. In contrast, after the early 1990s, El Niño–related warm sea surface temperature anomalies were stronger and longer-lasting with westward extension. This enhanced the NPAAC with a decadal westward extension, and consequently, the anomalous regional Hadley circulation was more evident over Southern China after the early 1990s during the El Niño decaying AMJ, causing strong abnormal upward motion and excessive precipitation there. The present results emphasize an enhancing influence of El Niño on the subsequent PFS precipitation over Southern China since the early 1990s, offering better understanding of the interannual precipitation variability over Southern China and with important implications for regional seasonal climate prediction. Significance Statement The precipitation over Southern China during the pre–flood season (PFS) contributes between 40% and 50% of the local annual precipitation, with severe floods occurring frequently and tremendous socioeconomic impacts on the region, including on its agriculture, water resources, food security, ecosystems, disaster mitigation, infrastructure construction, and human health. This study reveals a decadal enhancement in the effect of El Niño on the subsequent PFS precipitation over Southern China since the early 1990s. This is ascribed to a decadal enhancement of El Niño–related warm sea surface temperature anomalies over the equatorial central Pacific, as a result of El Niño warming occurring more frequently over the central Pacific against the backdrop of global warming. To the extent that the central Pacific El Niño events would occur even more frequently for the projected future warming scenarios, a stronger effect of El Niño on the PFS precipitation over Southern China would be expected, implying potentially enhanced seasonal predictability of the regional climate in the future.