Increasing Sulfate Concentration Research Articles

Effects of sulfate on survival, osmoregulation and immune inflammation of mud crab(Scylla paramamosain) under low salt conditions

Sulfate is an important chemical component in seawater, which has a profound influence on the survival, growth, physiology and biochemistry of aquaculture species. The aim of this experiment was to study the effects of sulfate concentration on survival, osmotic regulation, oxidative stress and immune inflammation of mud crab(Scylla paramamosain). The results showed that the 72-h semi-lethal concentration of the crab was 3.373 g/L (1.353–8.589 g/L). After 28 days of cultivation, the contents of Na+-K+-2Cl− cotransporter (NKCC) and Na+-K+ ATPase (NKA) in the gill tissue of the S1 group (0 g/L Na2SO4) were significantly higher than those in the other three groups, and the sulfate content increased and the SOD activity decreased.Aspartate aminotransferase (AST) and alanine aminotransferase (ALT) were affected by sulfate content, and the content levels in the S3 group (1 g/L Na2SO4) were significantly lower than those in the other three groups. The activities of ACP and AKP first increased and then decreased with the increase of sulfate content in prepare solution, and the activities of ACP and AKP in the S3 group (1 g/L Na2SO4) were significantly higher than those in the other three groups. The absence of sulfate or high concentration of sulfate will affect the survival rate of mud crabs, and have a stressful effect on the osmotic regulation of mud crabs, inhibit oxidative stress ability, and promote inflammatory response. The purpose of this study was to explore the feasibility of sulfate-type saline-alkali water aquaculture of mud crab by studying the effect of sulfate on the mud crab under low salt conditions, and to provide theoretical basis and technical guidance for the promotion of saline-alkali water aquaculture.

Characterization of Surfactant Adsorption Profile in Carbonates Under Severe Reservoir Conditions With Geochemical Modeling Approach

Abstract Chemical flooding has gained ample popularity as an effective technique to increase oil displacement and sweep efficiencies. However, very limited numerical applications of chemical flooding (surfactant and polymer) in carbonates are reported in the literature. Therefore, a geochemical-based surface complexation model is developed to characterize the adsorption profile of surfactants for the first time across the length of a core/reservoir. The proposed model is validated with various zeta-potential measurements and also with a recently conducted chemical flooding study. Additionally, sensitivity analysis of various parameters is performed, and it is found that surfactant effluent concentration decreases with the increase in flood temperature. It is observed that salinity reduction decreases the surfactant adsorption, increases the ionic repulsion amid the rock surface charge and the chemical species polarity. Similarly, when the concentration of surfactant is increased, the adsorption of surfactant concentration increases. However, the increase in surfactant adsorption is insignificant. The effect of sulfate spiking in chemical flooding is also investigated and it is found that an increase in sulfate concentration reduces the adsorption of surfactant across the reservoir. Moreover, the lowermost surfactant adsorption level is achieved through the injection of diluted water (<0.1 mg/g).

Effects of Ultrafine Fly Ash against Sulphate Reaction in Concrete Structures.

In this study, Afşin Elbistan C-type fly ash (FA) was used, which protects against the sulphate reaction that damages concrete. The detrimental effects of post-reaction decrease with increasing fly ash fineness. The study used 10%, 30%, and 50% weight substitutes of cement. The fly ash was ground in a ball mill for 0, 10, 20, 30, 45, and 60 min, and Blaine fineness values of 1555, 1632, 2347, 2589, 2766, and 3433 cm2/g were obtained, respectively. The effect of the samples on the sulphate resistance was investigated by exposing the samples to 5% or 10% added sulphate solutions, and the compressive strength and ultrasonic pulse velocity of the concrete were tested. The compressive strength values obtained decreased with the increase in sulphate content, and the increase in the grinding time and the amount of substituted FA increased the compressive strength values. It was observed that weight loss increased with increasing sulphate content and decreased with the addition of FA with a high Blaine fineness. It was determined that as the Blaine fineness value increased, the sulphate content, FA substitution amount, and ultrasonic pulse speed decreased. This study was carried out to determine the effects of fly ash used at different fineness and replacement ratios on the performance and strength of concrete after exposure to external influences such as sulphate. The use of fly ash instead of cement will reduce the use of waste materials and natural resources and prevent environmental pollution. The cost of cement and concrete will be reduced.

Sulfur and nitrogen co-metabolism during composting: A role of sodium sulfide in regulating microbial communities and functional genes

Aerobic composting is an effective method for treating livestock and poultry manure. However, traditional aerobic composting often results in nitrogen loss and excessive N2O gas pollution in the atmosphere. In this study, metagenomics technology was used to investigate the co-metabolism of sulfur and nitrogen in composting with Na2S as an additive. The results showed that the content of nitrate and sulfate in the experimental group (T) was 19% and 34% higher, respectively, than that in the control group (CK) after composting maturation. The denitrification genes (narG, narH, nirK, and norB) and sulfur reduction gene (sat) in T were significantly inhibited, particularly on the fourth day. Actinobacteria and Proteobacteria were the dominant bacteria involved in sulfur and nitrogen co-metabolism. These findings indicated that the addition of Na2S effectively inhibits denitrification in composting, reducing N2O emissions and nitrogen loss, while increasing sulfate content and improving the quality of composting.

Electrolyte Effect on Photoetching of Gallium Nitride

The limited material removal rate of conventional chemical mechanical polishing (CMP) significantly hinders the fabrication efficiency and surface quality, thereby preventing the development of gallium nitride (GaN)-based devices. Moreover, the incorporation of photoelectrochemistry in CMP has garnered increasing attention because of its potential to enhance the quality and efficiency of the GaN process. However, a considerable gap still exists in the comprehensive understanding of the specific photoelectrochemical (PEC) behavior of GaN. Here, we report the influence of the electrolyte on the PEC etching of GaN. Various acids and bases were tested, with their pH being carefully adjusted. The concentrations of the cations and anions were also examined. The results showed that photocorrosion/photoetching was more pronounced in sulfuric acid, phosphoric acid, and nitric acid environments than in alkaline environments, but it was less pronounced in hydrochloric acid. Furthermore, the effects of pH and anion concentration on photoetching were investigated, and the results revealed that photoetching in acidic environments weakened with increasing pH levels and diminished with increasing sulfate concentration. The underlying reasons contributing to this observation were explored. These findings provide ideas for improving the photoetching efficiency of GaN, thereby enriching the photoelectrochemical mechanical polishing (PECMP) technology of GaN.

Crystallization Cycles in Masonry Walls: Experimental Technique to Develop Accelerated Aging on a Real Scale

Moisture in historic built heritage is one of the main degenerative agents, because it supports or manifests itself through multiple pathologies. Current knowledge allows for the diagnosis and assessment of the problem, but there are deficiencies in the evaluation of corrective systems due to the time it takes for moisture to become significant. In response, this study proposes an experimental methodology that aims to reproduce the accelerated aging of real scale specimens under laboratory conditions. Thereby improving the understanding of the impact of moisture related deterioration on masonry structures. To achive this, eight masonry walls were constructed and subjected to eight cycles of sulfate crystallization. They were saturated with different sulfate concentrations (5% or 10%) and exposed to different drying conditions (outdoor or solar dehydrator) in order to identify the factors favoring sulfate crystallization and the resulting deterioration. The progress of the experiments was monitored using a hygrometer, a thermographic camera and photogrammetry. The results indicate that it is possible to induce efflorescence in real scale specimens. Temperature and moisture monitoring helped identify the solar dehydrator as a more effective drying treatment. While digital photogrammetry was considered inefficient for quantifying volumetric damage, since this technique can present errors greater than 2%, a value exceeding the observed wear. Reason why the weight of material detached at the end of the experiment was recorded and a positive correlation between the increase in sulfate concentration and the use of the dehydrator was observed. Finally, pertinent considerations are made to improve the experimental conditions.

Reconfiguring oxygenation at ∼1.4 Ga: New constraints as informed by the ancient oceanic sulfur cycle

The extent of atmospheric and oceanic oxygenation during the Mesoproterozoic remains an area of active debate. Here, we report major and trace elements, organic sulfur (OS) speciation, sulfur isotopes in multiple phases [pyrite (py), OS, and carbonate-associated sulfate (CAS)], and a numerical model of sulfate concentrations from one of the Mesoproterozoic's best-preserved geochemical archives, the Xiamaling Formation (ca. 1.4 Ga) in the Yanliao Basin. These data reveal a previously unrecognized ocean-atmosphere oxygenation process. Starting with Unit 3, intense sulfurization increased organic carbon burial and thus oxygen release, resulting in a deep-water oxidation event within the Yanliao Basin that could be regarded as a transient restricted oxygen oasis based on low pyrite content, elevated kerogen S:C ratios, higher δ34Spy than δ34SOS (Δδ34SOS-py < 0), and a low calculated sulfate concentration of ∼0.07–0.14 mM. During Unit 2, the basin was reconnected to the open ocean with the deposition of organic-rich shale across northern China and northern Australia, accompanied by a shift in Δδ34SOS-py to 5.0‰ and a calculated seawater sulfate concentration of ∼0.1–1.14 mM. Such large-scale burial of organic matter released oxygen into the atmosphere, accompanied by significant sulfate delivery to the basin and euxinic conditions characterized by Mo concentrations and 34S-depleted pyrite at the topmost of Unit 2. A subsequent globally synchronized atmospheric and deep ocean oxygenation event may have occurred during Unit 1. This event was recorded by a progressive increase in Δδ34SOS-py (up to +9.6‰), increased oxidized OS species, and positive Ce anomalies (attributed to the reductive dissolution of the Ce-enriched Mn oxides), all of which were caused by increased sulfate concentrations (calculated to be ∼1.15–2.31 mM) and a spatial descent of the redox interface. The combination of these lines of evidence illustrates the sensitivity of the oceanic sulfur cycle to the ocean-atmosphere system and provides novel constraints on oxygenation at ∼1.4 Ga.

Solubility of neodymium and dysprosium sulfates at different pH and temperature and the effect of yttrium sulfate, sodium sulfate, and ammonium sulfate mixtures: Strengthening the predictive capacities of the OLI software

This study focuses on investigating the solubilities of two rare earth element (REE) sulfate salts, Nd2(SO4)3 (representing light REEs) and Dy2(SO4)3 (representing heavy REEs), under various conditions. Four different systems are studied: 1) binary REE2(SO4)3–H2O system at natural pH and temperatures of 25, 46, 65, and 80 °C, 2) ternary REE2(SO4)3–NaOH–H2O system, covering a pH range from 7 down to neutral, at temperatures of 25, 46, 65, and 80 °C, 3) ternary REE2(SO4)3–Y2(SO4)3–H2O system, involving Y2(SO4)3 concentrations ranging from 0 to 20 g/L, pH values of 3 and 7, all at 25 °C, and 4) quaternary REE2(SO4)3–Na2SO4–(NH4)2SO4–H2O system, encompassing Na2SO4 and (NH4)2SO4 concentrations varying from 0 to 20 g/L, pH values of 3 and 7, and at 25 °C. Solubilities of Nd2(SO4)3 and Dy2(SO4)3 decrease as temperature rises, attributed to the exothermic dissolution reactions. Within pH 2 to 5, solubilities remain relatively constant, but at higher pH, they decrease due to the formation of REE2(SO4)(OH)4(H2O)2 (rare earth sulfate hydroxide hydrate). Addition of Y2(SO4)3 does not significantly affect solubilities because of the relatively low Y2(SO4)3 concentration range (below 0.03 mol/kg of water), but solubilities are lower at pH 7 due to REE2SO4OH4H2O2 formation. For Nd2(SO4)3, solubility decreases with increasing Na2SO4 and (NH4)2SO4 concentrations, especially at pH 3 due to the formation of NaNd(SO4)2(H2O) (sodium neodymium bis(sulfate) hydrate) which is also confirmed by the decrease in Na2SO4 concentration compared with the target value. However, at pH 7, the concentration of Na2SO4 is much closer to the target range. This suggests that the formation of NaNd(SO4)2(H2O) is less significant at pH 7 and most of Nd precipitates as Nd2SO4OH4H2O2. For Dy2(SO4)3, solubility increases with increasing sulfate concentrations again due to the to the formation of REESO4+ and REE(SO4)2− complexes but the solubility is lower at pH 7 due to Dy2SO4OH4H2O2 and DySO4OH formation. The outcomes of this investigation represent a notable augmentation to the existing repository of solubility data for Nd2(SO4)3 and Dy2(SO4)3. These particular systems were deliberately chosen to emulate the process of extracting rare earth elements (REEs) from ion-adsorbed clays. Nonetheless, the implications of this research extend beyond this context and hold relevance for various procedures that involve the handling of REEs in sulfate-based environments. One prominent application of these findings lies in the augmentation of thermodynamic models, notably the MSE model integrated into the OLI software. Through the incorporation of this new dataset, the OLI software is poised to become a more potent tool for forecasting and simulating the chemistry of rare earth sulfate systems. This advancement bears significant promise for forthcoming research endeavors and industrial applications where precise modeling of REE behavior is of paramount importance.

Effect of sulfate on arsenic migration and transformation in micro-cosmic experiments simulating mangrove sediment environment

Fragile mangrove wetlands are threatened by sea level rise, which results in the introduction of increased sulfate concentrations into mangrove sediment. Mangroves are also susceptible to heavy metal contamination, such as arsenic (As) contamination. However, little is known about whether sulfate affects the bioavailability of As in mangrove sediment. This study focuses on the effects of sulfate on arsenic mobilization and transformation in As-contaminated mangrove sediment, and modeled changes in sulfate concentration, As contamination levels, and pH conditions. The As release from sediment treated with sulfate (30 mM) significantly decreased (P < 0.05). In the moderate arsenic-contaminated sediment, the mean arsenic release was 181.95 ± 33.05 μg kg−1 without sulfate and 157.55 ± 40.98 μg kg−1 with sulfate. In addition, the release of As was affected by both pH and sulfate when pH conditions were changed. Arsenic release was promoted at pH 11 (P < 0.05), but sulfate still mitigating As release at this pH value (P < 0.001). Furthermore, the release of As after sulfate input was always accompanied by the release of iron (Fe) and aluminum (Al). Sulfate altered the distribution of forms of As in the sediment, with a significant increase in the proportion of strongly adsorbed As and silicate-bound states of As. Overall, sulfate intrusion mitigates As release, but it also increases the bioavailability of As in the sediment. This fact makes the toxic element most susceptible to long-term mobilization via biological processes. Therefore, the effect of persistent sulfate intrusion caused by sea level rise on toxic elements in mangrove sediment deserves long-term attention. The significance of this study is that it contributes to understanding the behavior of heavy metals in coastal wetland ecosystems affected by sea level rise.

Progressive damage process and destabilization precursor recognition of sulfate tailing-cemented paste backfill based on acoustic emission

Sulfate-rich tailings are commonly used as aggregate materials for mine filling, and the sulfate retained within them significantly affects the structural characteristics of cemented paste backfill (CPB). A series of microstructure tests, uniaxial compressive strength (UCS) tests, and acoustic emission (AE) monitoring were carried out on CPB and sulfate tailing-cemented paste backfill (ST-CPB) to investigate the progressive damage pattern and identify the destabilization precursor information of the backfill. The results showed that the UCS of the backfill increased and then decreased with the increase in sulfate content, and 1.5% was the optimal content. The AE counts, energy, amplitude, and peak frequency time series corresponded to each other, exhibited the stage characteristics of a stress curve and were significantly affected by sulfate content. CPB and 0.5% ST-CPB displayed more active AE counts and energy during the initial loading stage, with high amplitude and low-frequency signals. However, the 1.5% ST-CPB exhibited active AE events and medium-high amplitude and medium-low frequency signals only during the plastic yielding and damage stages. 2.5% ST-CPB exhibited more active AE signals during the entire loading process. RA-AF values indicate that CPB and 2.5% ST-CPB reached 93.12 and 96.62% of tensile cracks at final failure, respectively. Meanwhile, the percentages of tensile cracks at the final failure of 0.5 and 1.5% ST-CPB were 76.65 and 76.86%, respectively. The sudden increase in the variance curve and the rapid decrease in the b value of AE in the critical slowdown theory were identified as the precursor characteristics of the backfill instability. This investigation can provide technical and theoretical support for the progressive damage characteristic and stability assessment of ST-CPB.

Hydrogeochemical evolution of groundwater impacted by acid mine drainage (AMD) from polymetallic mining areas (South China)

Mining activities have long-term impacts on the groundwater of surrounding areas and deserve in-depth analysis and study. Herein, the geochemical mechanisms of acid mine drainage (AMD)-affected groundwaters were examined, and groundwater quality was assessed through water quality indices. 15 water samples from 7 domestic and 4 groundwater monitoring wells were tested for physical and chemical parameters in 2022, and multivariate statistical analysis was carried out with monitoring data from 21 domestic wells in 2010. The groundwater chemical composition varied from a predominantly Ca-HCO3 type in 2010 to a Ca-SO4 type in 2022. The isotopic values of δ18O and δD indicate that groundwater has not been significantly affected by evaporation. Changes in groundwater sulfate and total dissolved solids (TDS) levels over the twelve-year period confirmed the AMD infiltration impact on groundwater quality. The groundwater chemical properties changed more slowly than those of surface waters affected by AMD based on a cumulative increase in sulfate concentration of 29.94 mg/L. Changes in groundwater quality were investigated, namely, the spatiotemporal distribution of potentially toxic elements (PTEs), including Fe, Mn, Cd, Pb, and As. Mn concentrations in upstream groundwater areas near the mine decreased by 61.8% between 2010 and 2022. Conversely, groundwater in midstream areas had Mn concentrations of 2.25 mg/L and arsenic concentrations of 11.8 μg/L, both exceeding the WHO, 2022 standard. According to multivariate statistical analysis, Mn, Cd, and Pb originated from polymetallic minerals, whereas As was likely derived from the reduction of Fe/Mn hydroxyl oxides. AMD remediation improved contaminated upstream groundwater quality over 12 years, with a 36.8% improvement in WQI values. PTE distribution determined water quality changes; therefore, PTE contamination should be treated in mid- and downstream regions while contaminated groundwater should be treated upstream.

Effects of sulfate concentration and external voltage on operation efficiency, sludge characteristics, and microbial community of a bioelectrochemical system

In this study, a coupled anaerobic baffled reactor-microbial electrolysis cell (ABR-MEC) was constructed for treatment sulfate wastewater, with an external power supply. The concentration of sulfate and the external power supply intensity were changed to explore the variations in the operation efficiency and sludge characteristics of the system. When the sulfate concentration was 1000 mg/L, COD/SO42-= 2:1, and the voltage was adjusted to 1 V (the stage Ⅰ), the average sulfate removal rate was 73% and the COD removal rate was above 80%. At the conditions of sulfate concentration of 1300 mg/L, COD/SO42- = 1.5:1, and a voltage of 1 V (the stage Ⅱ), the activities of coenzyme F420 and 6-phosphofructokinase increased by 23.8% and 26%, respectively. However, the sulfate removal rate of the system reduced to 69.3% with voltage adjusted to 2 V (the stage Ⅲ). The dominant microbial community in the system were Proteobacteria, Euryarchaeota, and Thermotogae at sulfate concentration 1000 mg/L. With sulfate concentration in the influent increased to 1300 mg/L, the abundance of Thermodesulfobacteria increased to 10.55%. After increasing the external voltage, the relative abundance of Firmicutes increased by 4.51%. Metagenomic analysis illustrated that with the increase in sulfate concentration and external voltage, the glycolysis and sulfate metabolic pathway modules showed a downward trend, and the conversion efficiency decreased.

Experimental study on evolutive fracture behavior and properties of sulfate-rich fiber-reinforced cemented paste backfill under pure mode-I, mode-II, and mode-III loadings

Tensile and shear fracture behaviors of fiber-reinforced cemented paste backfill (FRCPB) play critical roles in the safe and cost-effective engineering design of underground mine backfill structures. Sulfate pore solution is a key factor affecting the time-dependent evolution of fracture behavior and properties of FRCPB. However, no studies have been carried out to systematically investigate its effects on the fracture behavior and properties of mine backfill used in underground mines. The objective of this study is to discover the effect of sulfate concentration (0, 5000, 15,000, and 25,000 ppm) on FRCPB's fracture behavior and properties at different curing times (3, 7, 28, and 90 days) and under pure mode-I, mode-II, and mode-III loadings. The results show that, except for the 3-day FRCPB, the increase in sulfate concentration can continuously improve pre-peak stiffness and peak fracture resistance force and significantly enhance the post-peak residual resistance, especially under mode-III loading. Moreover, fracture energy shows a higher sensitivity to the sulfate concentration with respect to fracture toughness and stiffness. Furthermore, sulfate concentration has a very limited effect on tensile crack trajectory under mode I loading, while a transition of shear cracks from a curved crack pattern to a sharp and straight one is detected under mode II and III loadings. In addition, the fracture toughness possesses a stronger correlation with material stiffness and thus is recommended for the design of FRCPB to offer a more effective immediate support to surrounding rock. The obtained results provide an in-depth insight into the sulfate-induced evolution of fracture behavior and properties of FRCPB under various loading conditions and thereby promote the safe implementation of mine backfill technology.

Enhancing the aluminate reaction during OPC hydration by combining increased sulfate content, triethanolamine and tartaric acid

Possibilities for enhancing the aluminate reaction were studied in a mix of OPC blended with 7.9 % hemihydrate (HH) or 7.4 % anhydrite (AH) in combination with different triethanolamine (TEA) dosages. Heat flow calorimetry and quantitative X-ray diffraction (XRD) were performed to study the hydration process. Using anhydrite as an additional sulfate carrier allowed a lower TEA dosage compared to hemihydrate systems to enhance the degree of hydration of C3A. High TEA dosages in hemihydrate systems were found to hinder C3S hydration. Nevertheless, it was possible to push the aluminate reaction ahead of the silicate reaction, thereby enhancing the degree of hydration of C3A. Additionally, the degree of hydration of C3S was not strongly affected when anhydrite and a well-balanced TEA dosage were used. The addition of tartaric acid to OPC-anhydrite-TEA systems retarded the subsequent aluminate reaction.

Influence of Wetting-Drying Cycles on Strength Behaviour of Cured Lime Treated Soil Contaminated with Monovalent and Divalent Sulphatic Solutions

Exposure of lime treated expansive soil to sulphatic compounds are known to develop distresses due to the formation of ettringite or thaumasite, causing excess swell and alteration in strength behaviour. However, effect of wetting–drying (W-D) cycles caused due to seasonal variations on the behavior of lime treated soil exposed to sulphate contamination has not been addressed properly. Hence, present work investigates the impact of varying W-D cycles (0–4) on unconfined compressive strength (UCS) behaviour of lime treated soil in presence of two different sulphatic [i.e., monovalent sodium sulphate (Na2SO4) and divalent gypsum (CaSO4·2H2O)] contaminations. Lime treated soil samples are, firstly, cured for 7, 14 and 28 days and then used for further process of W-D cycles after completion of each curing periods. Varying sulphate concentrations (i.e., 3000, 10000, 16000, 20,000 and 30000 ppm) as prepared by using Na2SO4 and CaSO4·2H2O using distilled water have been used as contaminating solutions in W-D cycles process for lime treated soil. Strength behaviour of samples subjected to W-D cycles are determined at both wet and dry sides of each cycle. The results revealed that strength of lime treated soil is influenced highly by sulphatic concentration, types of sulphatic compound (monovalent or, divalent cations), curing periods as well as number of W-D cycles. Adverse impacts on strength are pronounced with an increase in sulphate concentration and number of W-D cycles. However, significant adverse effect on strength and durability are pronounced in the samples subjected to sulphate concentration more than 16000 ppm. Further, study is extended to elucidate the experimental results with physicochemical behaviour and microanalyses [XRD, FESEM, EDAX, FTIR and TGA-DTA]. It is confirmed that progression of number of W-D cycles with the increase in sulphatic concentration has influenced significantly to the microstructure of lime treated soil.

Study of early-age performance of cementitious backfills with alkali activated slag under internal sulfate attack

The vulnerability to internal sulfate attack of calcium-rich ordinary Portland cement (OPC) and its relative high cost force mines to explore technically effective and low cost alternative binders to solidify sulfate-containing tailings. Alkali activated slag (AAS) has been established to be a promising substitute for OPC due to its superior strength, good resistance to chemical attack and low cost. This study shows results of a laboratory research dealing the characteristics of cemented paste backfill (CPB) with AAS under internal sulfate attack. A blend of two alkali activators (SS: sodium silicate, SH: sodium hydroxide) was considered. To assess the behavior of CPB materials subjected to diverse conditions, a total of 4 different SS/SH ratio (e.g., 0.5, 0.75, 1, and 1.25) were used within CPB. Results shows that initial/final setting times tend to drop with growing sulfate content up to 5000 ppm, followed by gradual increases. Increasing sulfate content leads to higher yield stresses and viscosities and the degree of this negative impact is much severer in samples having the high SS/SH ratio. The presence of sulfate can enhance or deteriorate the strength of AAS-CPB depending on activator type, cure age and initial sulfate content. CPB with high SS/SH ratio reveals weaker resistance to internal sulfate attack due to their lower pH values. The key outcome of this work will be beneficial to optimally design of sulfate bearing CPB-AAS structures.

Unravelling the role of sulphate in reed development in urban freshwater lakes

Many European lakes have suffered from reed die-back since the 1950s. Previous studies have concluded that this is due to a combination of several interacting factors, but possibly also a single threat with high impact might be responsible for the phenomenon. In this study, we investigated 14 lakes in the Berlin area differing in reed development and sulphate concentration from 2000 to 2020. To unravel the decline of reed beds in some of the lakes with coal mining activities in the upper watershed, we compiled a comprehensive data set. Thus, the littoral zone of the lakes was divided into 1302 segments considering the reed ratio relative to segment area, water quality parameters, littoral characteristics and bank usage of the lakes which all have been monitored for 20 years. We ran two-way panel regressions with a within estimator to consider the spatial variation between and within the segments over time. The regression results revealed a strong negative relationship between reed ratio and sulphate concentrations (p<0.001) as well as tree shading (p<0.001) and a strong positive relationship with brushwood fascines (p<0.001). Taking only sulphate into account, reeds would have covered an additional area of 5.5 ha or 22.6% in 2020 (total reed area: 24.3 ha) in the absence of increased sulphate concentrations. In conclusion, changes in water quality upstream the catchment cannot be ignored in the development of management plans for downstream lakes.

Residence Time Distribution Analysis of Drip-Irrigated Beds—The Effect of Material and Fluid Properties with Implications for Heap Leaching Practice

The quantitative effect of particle shape, porosity, wettability, particle size, and solution viscosity on the residence time distribution (RTD) profiles of non-reactive, steady-state, drip-irrigated ore beds characteristic of heap leaching systems is presented. Results were obtained using step-up tracer tests and allowed for the analysis of preferential flow behaviour within the systems. The key findings were as follows. Increased particle sphericity enhanced channelling in beds of smaller particles, but not for larger particle sizes. Higher particle wettability caused greater liquid dispersion during both initial wetting studies and at steady-state fluid flux. Higher porosity levels and the inclusion of fines in mixed sized beds resulted in longer average solute residence times, higher liquid hold-up, longer solution and tracer breakthrough times, and increases in drain-down moisture percentages. Increasing the irrigation fluid’s viscosity, reflective of the increase in ionic concentrations in leach solutions, reduced both the solution and tracer breakthrough times and increased dispersion with signs of more discontinuous or isolated fluid volumes at steady-state. These results highlighted the importance of the inclusion of fines in agglomerated beds to improve uniform wetting especially those with low to moderate particle porosities (&lt;2.5 m2/g specific surface area). The viscosity results suggest that there may be changes in preferential flow extent, due to variations in viscosity owing to the increasing sulphate concentration within the liquid phase in heaps and with time.

The characteristics of ultraviolet absorption and electronic excitation of sulfate at high concentrations

The variation of spectra and the characteristics of electronic excitation are critical for establishing a model for quantifying sulfate at high concentrations. The absorption characteristics of sulfate are affected by the optical pathlength and sulfate concentration. The absorption coefficient declines by approximately 86.09–96.20% with an increasing concentration (0–130 g/L) at different optical pathlengths (1–100 mm). Moreover, a high sensitivity and accuracy can be achieved at weak absorption wavelengths or at lower optical pathlengths when high concentrations of sulfate are detected. In addition, the maximum absorption wavelength of sulfate redshifts by approximately 0–10 nm with an increasing concentration and optical pathlength, which is significantly affected by the optical pathlength. The (H2SO4)n‧(H2O)4-n models were established at the PBEPBE/6–311++G(d, p) level of theory. There absorption spectra were calculated by the time-dependent density functional theory (TD-DFT) method. As a result, the maximum absorption wavelength redshifted from 180.16 nm to 192.71 nm with an increasing sulfate concentration, and the corresponding absorption coefficient demonstrated a declining trend. Furthermore, the electron-hole and natural bond orbital (NBO) analysis indicate that the type of electronic excitation changes from a n(O) → σ*(S-O) localized excitation to n → σ* charge-transfer excitation as the sulfate concentration increases. This study provides a theoretical foundation for understanding the spectral behavior of sulfates and constructing the quantification models or methods that can also be applied to analyze the spectroscopy of other chemicals.

Microbial sensitivity to temperature and sulfate deposition modulates greenhouse gas emissions from peat soils.

Peatlands are among the largest natural sources of atmospheric methane (CH4 ) worldwide. Microbial processes play a key role in regulating CH4 emissions from peatland ecosystems, yet the complex interplay between soil substrates and microbial communities in controlling CH4 emissions as a function of global change remains unclear. Herein, we performed an integrated analysis of multi-omics data sets to provide a comprehensive understanding of the molecular processes driving changes in greenhouse gas (GHG) emissions in peatland ecosystems with increasing temperature and sulfate deposition in a laboratory incubation study. We sought to first investigate how increasing temperatures (4, 21, and 35°C) impact soil microbiome-metabolome interactions; then explore the competition between methanogens and sulfate-reducing bacteria (SRBs) with increasing sulfate concentrations at the optimum temperature for methanogenesis. Our results revealed that peat soil organic matter degradation, mediated by biotic and potentially abiotic processes, is the main driver of the increase in CO2 production with temperature. In contrast, the decrease in CH4 production at 35°C was linked to the absence of syntrophic communities and the potential inhibitory effect of phenols on methanogens. Elevated temperatures further induced the microbial communities to develop high growth yield and stress tolerator trait-based strategies leading to a shift in their composition and function. On the other hand, SRBs were able to outcompete methanogens in the presence of non-limiting sulfate concentrations at 21°C, thereby reducing CH4 emissions. At higher sulfate concentrations, however, the prevalence of communities capable of producing sufficient low-molecular-weight carbon substrates for the coexistence of SRBs and methanogens was translated into elevated CH4 emissions. The use of omics in this study enhanced our understanding of the structure and interactions among microbes with the abiotic components of the system that can be useful for mitigating GHG emissions from peatland ecosystems in the face of global change.