Cumulative Concentration Research Articles

The Mechanism Involved in the Inhibition of Resveratrol and Genistein on the Contractility of Isolated Rat Uterus Smooth Muscle

Purpose: This study aimed to compare the effects of the phytoestrogens resveratrol (RES) and genistein (GEN) on the contractility of isolated uterine smooth muscle from rats, focusing on both spontaneous and stimulated contractions, and to investigate the underlying mechanisms. Methods: Uterine strips were suspended vertically in perfusion chambers containing Kreb’s solution, various concentrations of RES and GEN were added to the ex vivo uterine strips, and contractions were measured before and after incubation with RES or GEN. Results: (1) Both RES and GEN inhibited K+-induced contractions in a dose-dependent manner; the β/β2-adrenoceptor antagonist propranolol (PRO), ICI118551, the ATP-dependent K+ channel blocker glibenclamide (HB-419) and the NO synthase inhibitor N-nitro-L-arginine (L-NNA) diminished the inhibitory effects of RES and GEN on K+-induced contractions. (2) RES and GEN also dose-dependently inhibited PGF2α-induced uterine contractions. (3) The inhibitory effects of RES and GEN were observed in spontaneous contractile activities as well; PRO, ICI118551, HB-419 and L-NNA attenuated the inhibitory effects of RES and GEN on the spontaneous contractions of isolated uterine muscle strips. (4) RES and GEN significantly decreased the cumulative concentration response of Ca2+ and shifted the Ca2+ cumulative concentration–response curves to the right in high-K+ Ca2+-free Kreb’s solution. (5) RES and GEN markedly reduced the first phasic contraction induced by oxytocin, acetylcholine, and prostaglandin F2α but did not alter the second phasic contraction caused by CaCl2 in Ca2+-free Kreb’s solution. Conclusions: RES and GEN can directly inhibit both spontaneous and activated contractions of isolated uterine smooth muscle. The mechanisms underlying the inhibitory effects of RES and GEN likely involve β adrenergic receptor activation, reduced Ca2+ influx and release, the activation of ATP-dependent K+ channels and increased NO production.

Highly efficient electrosynthesis of hydrogen peroxide through reversible transformation between catechol and o-benzoquinone on polydopamine modified carbon black

Carbon-based materials are more promising catalysts for H2O2 electrochemical production. However, the common method for modifying carbon-based materials is surface functionalization with harsh and uncontrollable reaction conditions, hindering the precise regulation of the active sites. Herein, we proposed a carbon-based material modified by polydopamine (CB-PDA) that was easily prepared and used in air diffusion electrode system for H2O2 production. The rapid and reversible transformation between catechol and o-benzoquinone on PDA could improve the H2O2 selectivity from 75.5 % to 97.0 % during the electrocatalytic process. The detection of adsorbed *HOOH and *OOH in oxygen reduction reaction proved the preference of CB-PDA for the two-electron pathway. The H2O2 formation rate constant of CB-PDA increased significantly from 25.85 to 60.82 mM h−1. The highest cumulative H2O2 concentration could reach 10200 mg L−1 in 9 h. Long-term operation tests proved the good operational stability. Furthermore, this system was cost-effective without additional aeration energy consumption and could achieve rapid disinfection in 10 min, which would have great potential to be used in environmental remediation.

Temporal trends of seasonal pollen indexes in a region of Northern Italy (2001–2022)

Increasing trends in allergic respiratory diseases may be linked to climate changes affecting pollen levels. This study aimed to investigate the temporal trends in seasonal indexes of 9 allergenic pollen types in the Veneto Region, Northern Italy. Available daily data from 20 monitoring stations covered 2001–2022 for Corylaceae, Cupressaceae, Poaceae, Oleaceae, and Urticaceae (pollen families), and 2006–2022 for Alnus, Betula, Ambrosia, and Artemisia (pollen genera). The 95-percentage method was used to identify the start/end dates of pollen seasons annually, and the seasonal cumulative pollen concentration (Seasonal Pollen Integral, SPIn) was calculated. The non-parametric Theil-Sen median slope method was used to examine trends in pollen seasons’ start day, duration, and SPIn in the whole region and for climatic areas (alpine, subcontinental eastern, subcontinental western). The results showed a clear upward trend in SPIn for several pollens, with median slopes ranging from 326 (Alnus) to 1089 p/m3 per 10yrs (Corylaceae); exceptions were Artemisia, whose SPIn decreased over time (−26 p/m3 per 10yrs), and Ambrosia, Betula, and Urticaceae, which did not show a clear trend. For families, pollen seasons showed a trend for anticipation (from −4.7, Urticaceae, to −13.5 days/10yrs, Oleaceae) and extended duration (from 8.3, Cupressaceae, to 13.3 days/10yrs, Oleaceae). An evident heterogeneity across the climatic areas was seen for the SPIn, with the subcontinental western area exhibiting the highest loads and most prominent increases over time. In conclusion, increased levels and prolonged seasons for several pollen taxa observed in the Veneto Region, particularly in subcontinental areas, suggest increasing risks for individuals with pollen allergies. Addressing this issue requires measures of mitigation and adaptation to climate-driven changes in pollen exposure.

Quantitative and mechanistic elucidation of the reactive oxygen species for effective sulfamethoxazole removal in heterogeneous peroxymonosulfate activated by MOFs-derived cladding structure CoZn/NC@UiO

In cobalt-based catalyst/peroxymonosulfate (PMS) systems, the key issues are the leaching of metals and the stability of catalysts. In this study, a NH2-UiO-66 cladded CoZn/NC catalyst was synthesized for efficient degradation of sulfamethoxazole (SMX) using activated PMS. The removal efficiency of SMX could achieve 100% within 30 min. The leaching of Co2+ was inhibited to 0.05 ppm and the anti-interference and cyclic stability of the catalyst were enhanced by the NH2-UiO-66 shell. In addition, the quenching experiment, electron paramagnetic resonance (EPR) technique and probe experiment were used to analyze the reactive oxygen species (ROSs) qualitatively and quantitatively. The findings demonstrated that singlet oxygen (1O2) had the highest steady-state and cumulative concentration. However, 1O2 could only participate in the degradation of SMX through single electron transfer or addition reaction, resulting in a lower second-order rate constant of the SMX reaction with 1O2. Sulfate radical (SO4·-) contributed the most to the degradation of SMX due to the high reactivity of the sulfonamide structure in SMX to SO4·-. Finally, possible pathways for SMX degradation were proposed. The two primary mechanisms of SMX degradation were S-N cleavage and amino hydroxylation/oxidation. The toxicity of most of the intermediates was less than that of SMX through ecological structure–activity relationship analysis. Overall, a novel approach to synthesize low leaching and efficient cobalt based catalyst was put forward, and the activation mechanism of PMS was also revealed.

Cardiotoxicity of Iron and Zinc and Their Association with the Mitochondrial Unfolded Protein Response in Humans.

This study was designed to examine the association between myocardial concentrations of the trace elements Cu, Fe, Mn, Mo, and Zn and the expression of mitochondrial unfolded protein response (UPRmt) elements and the age of patients who received heart transplantation or a left-ventricular assist device (ageHTx/LVAD). Inductively coupled plasma mass spectrometry was used to determine the concentration of Cu, Fe, Mn, Mo, and Zn in the myocardium of control subjects and patients undergoing heart transplantation or left-ventricular assist device (LVAD) implantation. We used ELISA to quantify the expression of UPRmt proteins and 4-Hydroxynonenal (4-HNE), which served as a marker of oxidative-stress-induced lipid peroxidation. Concentrations of Cu, Mn, Mo, and Zn were similar in the control and heart failure (HF) myocardium, while Fe showed a significant decrease in the HF group compared to the control. A higher cumulative concentration of Fe and Zn in the myocardium was associated with reduced ageHTx/LVAD, which was not observed for other combinations of trace elements or their individual effects. The trace elements Cu, Mn, and Zn showed positive correlations with several UPRmt proteins, while Fe had a negative correlation with UPRmt effector protease YME1L. None of the trace elements correlated with 4-HNE in the myocardium. The concentrations of the trace elements Mn and Zn were significantly higher in the myocardium of patients with dilated cardiomyopathy than in patients with ischemic cardiomyopathy. A higher cumulative concentration of Fe and Zn in the myocardium was associated with a younger age at which patients received heart transplantation or LVAD, potentially suggesting an acceleration of HF. A positive correlation between myocardial Cu, Mn, and Zn and the expression of UPRmt proteins and a negative correlation between myocardial Fe and YME1L expression suggest that these trace elements exerted their actions on the human heart by interacting with the UPRmt. An altered generation of oxidative stress was not an underlying mechanism of the observed changes.

17β-Estradiol Nanoparticles Increase Endothelial Nitric Oxide Synthase Expression Through Akt Pathway in Rats with Myocardial Infarction

17β-estradiol can effectively slow down progression of myocardial infarction (MI), and is expected to have more curative effects. Therefore, this study investigated the mechanism underlying cardioprotective role of 17β-estradiol NPs in rats with MI. After construction of rat MI model and preparation of 17β-estradiol NPs, the rats were administered with 17β-estradiol alone, 17β-estradiol NPs and Akt agonist or inhibitor. Distribution of 17β-estradiol NPs was observed by fluorescence microscope and release curve was detected. After treatment, echocardiography was conducted to measure the cardiac function indicators. With HE staining to observe myocardial tissue, RT-qPCR and Western blot determined levels of AKT and eNOS. The NPs were relatively uniform in size and round in shape; and cumulative release rate and concentration of 17β-estradiol in rats reached highest level on 30th day. Treatment with 17β-estradiol or 17β-estradiol NPs importantly increased survival rate of MI rats and decreased MI area while improving LVSP, LVDP, and HR. Moreover, the 17β-estradiol NPs had the smallest MI area. The myocardial tissue of rats in the 17β-estradiol NP group was closely arranged, and myocardial collagen was significantly reduced. The 17β-estradiol NPs increased the mRNA level of eNOS and Akt when eNOS expression was related to Akt expression. 17β-estradiol NPs can therefore increase the expression of eNOS by activating Akt signaling pathway, thereby relieving the myocardial injury in rats, hindering progression of MI.

Environmental Geomarker to Assess Impact on Hospitalization.

By linking medical real-world data with geographic information, it is possible to evaluate the impact on hospitalization based on these characteristics, such as patient residence information and disease and medical information. In this study, environmental exposure to air pollutants was reported as a risk factor, and predictive models were used to examine factors affecting health. The importance of the characteristics appeared according to the disease, and overall, the patient profile at the time of admission, such as ADL, was shown to be high, but for respiratory diseases, the cumulative concentration of air pollutants NO2, SPM, and NOx for one year before the onset of admission was the top risk factor for long-term hospitalization, suggesting the influence of exposure due to environmental factors.

Early age accelerated carbonation of cementitious materials surface in low CO2 concentration condition

Accelerated carbonation curing contributes to the carbon sequestration effect of cementitious materials and enhances surface density. However, in large-scale applications, traditional high CO2 concentration conditions (>5 % CO2) are constrained by economic costs. This study traces the early-stage accelerated carbonation process of cement mortar under low CO2 concentration (3 % CO2) condition from the perspectives of the evolution of CaCO3 crystal types, phase transformations, and microstructural changes, and compares the results with those under the 20 % CO2 condition. The results show that the carbonation depth of mortar specimens cured under the 3 % CO2 condition is shallower, but the cumulative concentration of CaCO3 within the surface 3 mm is not significantly lower than that under the 20 % CO2 condition; The carbonation zone generates more low-crystalline forms of CaCO3; The accelerated carbonation process does not affect the formation of CH and ettringite. Microscopic results indicate that under the 3 % CO2 condition, the synergistic effects of hydration and carbonation are better, and appropriately extending the curing time helps to refine the pore structure of the carbonation zone and improve the density of the substrate surface.

Boosting acidic hydrogen peroxide electrosynthesis on 2D metal-organic framework nanosheets based on cobalt porphyrins

The 2-electron electrocatalytic oxygen reduction reaction (2e− ORR) to hydrogen peroxide (H2O2) represents a promising strategy to resolve the high energy consumption and increasing environmental concerns inherent in the traditional anthraquinone process. The acidic 2e− ORR has emerged as an exciting alternative for industrial-level H2O2 production, whereas is hampered by the inferior H2O2 selectivity due to the uncontrollable proton-coupled electron transfer processes in an acidic environment. Herein, an ultrathin 2D metal–organic frameworks (MOFs) nanosheet based on cobalt tetra(4-carboxyphenyl) porphine (Co-TCPP NSs) is designed to promote H2O2 selectivity up to 96.5 %, accompanied with a remarkable H2O2 generation rate of 4677.42 mg·L−1·h−1. Of note, the Co-TCPP NSs also demonstrate its potential for the electro-Fenton process with a cumulative H2O2 concentration of 1.21 wt%, highlighting its practical potential in portable H2O2 generation electrochemical devices for distributed applications. Our findings demonstrated that the efficient H2O2 electrosynthesis could be attributed to the attenuated *OOH adsorption over Co-N4 moiety on the Co-TCPP NSs, which consequently suppresses its further reduction to form H2O. This work highlights the potential of 2D MOF architecture for the 2e− ORR and provides an atomic-level insight into the enhanced H2O2 selectivity.

In situ polymerization of a poly(3,4-ethylenedioxythiophene):poly(sodium–styrennesulfonate) conductive layer for electro-assisted ultrafiltration and fouling mitigation

Electrification can enhance the antifouling performance of ultrafiltration membranes and improve the sustainability of membrane technologies. The design of high-performance conductive membrane materials remains one of the core technologies in electro-assisted ultrafiltration. Here, conductive PVDF/PEDOT:PSS composite membranes were prepared via in situ chemical oxidation polymerization on a PVDF surface. The PVDF/PEDOT:PSS membranes were subsequently used for electro-filtration to study the effect of the applied potential on humic acid fouling. When a voltage of 3 V was applied, the PVDF/PEDOT:PSS20 membrane was continuously polluted for 5 cycles. The results showed that after simple hydraulic cleaning, the membrane flux recovery rate reached 91 %. Compared with that of the PVDF membrane, the irreversible fouling of the PVDF/PEDOT:PSS20 membrane decreased by 65 %. The modified Poisson Boltzmann equation indicates that applying cathodic potential on the surface of PEDOT:PSS conductive layer increases the cumulative concentration of counter ions on the membrane surface and the thickness of the charged layer, thereby promoting the migration of peak forces on the membrane surface to the bulk solution, changing the fouling behaviour of HA from cake filtration to standard blocking.

Evaluation of airborne transmission of respiratory contaminants in a passenger car cabin with window opening

Exhaled aerosols can be suspended in the air for long periods, facilitating the transmission of highly infectious respiratory diseases. The risk of exposure to occupants varies due to different usage conditions and driving scenarios of moving vehicles. Therefore, the present study investigates the airborne transmission of contaminants generated by coughing in a moving vehicle and explores the relationship between aerosol dispersion and fluid exchange between the interior and exterior domains of the car under the influence of window opening configurations, seating layouts and driving speeds. The results show that the cross-opening configurations provide a superior contaminant removal efficiency. The effect of seating layout on removal efficiency is significant, although it has a slight effect on air change rate (ACH). The best removal efficiency can be obtained when the passenger sits in the front seat with the right front window opening. Furthermore, the in-cabin ACH is almost linearly correlated with the driving speed. Higher speeds reduce contaminant concentrations faster. However, the risk of driver exposure does not depend solely on ACH, the peak cumulative contaminant concentration and residence time also need to be considered. This study offers data for the prevention and control of respiratory infectious diseases.

Measurement of inward leakage of full-face masks in EN and ISO standards: comparison of gas and aerosol test agents.

In Europe, respiratory protective devices must be certified before they can be marketed. Among the parameters of interest, inward leakage (IL) characterizes the tightness between the face seal and the face, to verify that the device is well-designed. European standard EN 13274-1 (2001) and International Organization for Standardization (ISO) standard ISO 16900-1 (2019) specify that IL should be measured using sodium chloride (NaCl) aerosol or sulfur hexafluoride (SF6) gas. For reusable masks made of nonporous materials, both test agents are considered equally acceptable. However, the few studies that have compared IL values measured with various aerosols and gases have come to divergent conclusions. This work then aimed to measure IL with the test agents recommended by the standards to determine whether they are really equivalent. Since krypton (Kr) is an interesting candidate for replacing SF6 in standard tests, IL was assessed with SF6 and Kr simultaneously, and with NaCl aerosol using various calculation methods. Tests were carried out on 5 models of full-face masks donned on a headform connected to a breathing machine simulating 3 sinusoidal breathing rates of various intensities. The respirator fit on the headform was evaluated using a controlled negative pressure method to determine a manikin fit factor. Four scenarios were then tested to represent very poor, bad, good, and excellent fit. Gas concentration was measured using a mass spectrometer, and IL was calculated for SF6 and Kr. A combination of 3 devices allowed the determination of the number-based concentration of particles with diameters between 20 nm and 2 µm, and IL was calculated for each of the 33 channels, as well as using a cumulative number concentration. In addition, to comply with standards, a conversion was carried out to calculate IL using a cumulative mass concentration. The results of this work evidenced that the IL values measured with NaCl were systematically lower than those determined with gases. IL was also shown to vary with particle size, with a maximum value exceeding that calculated with cumulative concentrations (in number or mass). As part of the revision of the standards, protocols for measuring inward leakage should be redefined. On the one hand, acceptability thresholds should be re-evaluated according to the nature of the test agent (gas or aerosol), as it is clear that the 2 options do not give the same results for a given configuration. On the other hand, the aerosol leakage measurement protocol needs to be reworked to enable the measurement of a well-defined, robust, and reproducible inward leakage value.

Typical emerging contaminants in sewage treatment plant effluent, and related watersheds in the Pearl River Basin: Ecological risks and source identification

Emerging contaminants pose a potential risk to aquatic ecosystems in the Pearl River Basin, China, owing to the high population density and active industry. This study investigated samples from eight sewage treatment plants, and five surface water bodies of related watersheds. To screen the risk of emerging contaminants (ECs), and clarify their sources, this study calculated the risk quotient of detected chemical and performed source identification/apportionment using the positive matrix factorization method. In total, 149 organic pollutants were identified. Pharmaceuticals showed significant concentrations in sewage treatment plant samples (120.87 ng/L), compared with surface water samples (1.13 ng/L). The ecological risk assessment identified three chemicals with a heightened risk to aquatic organisms: fipronil sulfide, caffeine, and roxithromycin. Four principal sources of contaminants were identified: pharmaceutical wastewater, domestic sewage, medical effluent, and agricultural runoff. Pharmaceutical wastewater was the primary contributor (60.4 %), to the cumulative EC concentration and to ECs in sewage treatment plant effluent. Agricultural drainage was the main source of ECs in surface water. This study provides a strategy to obtain comprehensive information on the aquatic risks and potential sources of EC species in areas affected by artificial activities, which is of substantial importance to pollutant management and control.

Assessment of ozone pollution on rice yield reduction and economic losses in Sichuan province during 2015–2020

In recent years, there has been a significant increase in surface ozone (O3) concentrations in the troposphere. Ozone pollution has significant adverse effects on ecosystems, human health, and climate change, particularly on crop growth and yield. This study utilized the observational hourly O3 data, cumulative O3 concentration over 40 ppb per h (AOT40), and the mean daytime 7-h O3 concentration (M7) to analyze the spatiotemporal distributions of relative yield losses (RYLs) and evaluate the yield reduction and economic losses of rice in Sichuan province from 2015 to 2020. The results indicated that the average O3 concentration during the growing rice season ranged from 55.4 to 69.3 μg/m3, with the highest O3 concentration observed in 2017, and the AOT40 ranged from 4.5 to 8.7 ppm h from 2015 to 2020. At the county level, the O3 concentration, AOT40, and the relative yield loss (RYL) of rice based on AOT40 exhibited clear spatiotemporal differences in Sichuan. The RYLs of AOT40 were 4.9–9.2% from 2015 to 2020. According to AOT40 and M7 metrics, the yield loss and economic losses attributed to O3 pollution amounted to 78.75–150.36 (9.74–21.54) ten thousand tons, and 2079.08–4149.89 (257.25–594.45) million Yuan, respectively. Rice yield and economic losses were relatively large in the Chengdu Plain, southern Sichuan, and northeast Sichuan. These findings will contribute to a deeper understanding of the detrimental effects of elevated surface O3 concentrations on rice crops. It is imperative to implement more stringent O3 reduction measures aimed at lowering O3 concentrations, enhancing rice quality, and safeguarding food security in Sichuan.

Iodide enhances degradation of histidine sidechain and imidazoles and forms new iodinated aromatic disinfection byproducts during chlorination

Peptide-bound histidines and imidazoles are important constituents of dissolved organic matter in water, and understanding the formation of halogenated disinfection byproduct (DBP) formation from these compounds during disinfection is important for ensuring a safe drinking water supply. Previous studies suggested that histidine has low reactivity with chlorine only; this study indicates that iodide substantially enhances histidine reactivity with the disinfectant at a time scale from days to hours. Mono- and di-iodinated histidines were identified as dominant transformation products with cumulative molar yields of 3.3 % at 6 h and they were stable in water over 7 days. These products were formed via electrophilic substitution of iodine to imidazole ring when hypoiodous acid reacted with histidine sidechain. Bromide minimally influenced the formation yields of these iodinated products, and higher pH increased yields up to 12 % for pH in the range 5–9. The cumulative concentration of low-molecular-weight DBPs, such as trihalomethanes and haloacetic acids, was less than 0.3 % under the same conditions. Similar iodinated imidazole analogs were also identified from other imidazoles (i.e., imidazole-carboxylic and phenyl-imidazole-carboxylic acids). This study demonstrated that peptide-bound histidine and imidazoles can serve as important precursors to iodinated aromatic DBPs, facilitating the identification of less-known iodinated DBPs.

A novel pH-stat fed-batch strategy to boost the production of nicotinamide mononucleotide by high cell density fermentation

Nicotinamide mononucleotide (NMN), a naturally occurring nucleotide with various biological activities, has recently attracted significant interest for its potential applications in pharmaceutical and nutraceutical products. In this study, a genetically engineered E. coli via pH-stat fed batch fermentation produced a high concentration of intracellular NMN. The production process involved pH-stat glucose feeding and continuous feeding of nicotinamide (NAM). Various cumulative NAM concentrations of 6.4, 8.4, 10.4, and 14 g/L produced NMN of 16.7, 21.2, 22.5, and 10.7 g/L, respectively. Furthermore, the highest intracellular NMN concentration of 22.5 g/L was produced with 10.4 g/L of total cumulative NAM concentration along with a productivity of 1.13 g/L/h. This is the highest intracellular NMN titer and productivity achieved through optimized fed-batch fermentation to date. This also demonstrates that a high cell density approach through pH-stat feeding offers the potential to produce high quality, substantial NMN at a reasonable cost.

The overlooked reaction of H2O2 decomposition over carbonaceous cathodes

Electrochemical 2-electron oxygen reduction over carbon cathode is an important method to produce H2O2 in situ. Besides the H2O2 generation rate, the H2O2 decomposition rate is also crucial to the cumulative concentration of H2O2. It is generally believed that H2O2 decomposition will produce H2O and O2 by electro-reduction or carbon catalysis. Herein, a new H2O2 decomposition pathway is proved: carbonaceous materials may react with H2O2 spontaneously to release CO2 and CO at room temperature and atmospheric pressure. At low H2O2 concentrations, the reaction produced CO mainly and then CO2. But at high H2O2 concentrations, CO2 was a preponderant product over CO. The reaction was exothermal which causes the rise of solution temperature, promoting H2O2 decomposition to produce O2. The continuous decomposition of H2O2 raised the pH value, while the generated CO2 dissolved in the solution to reduce the pH value. These two effects together determined pH tendency. With the increase of pH value, H2O2 decomposition triggered by alkaline conditions produced H2O and O2. The applied negative voltage accelerated H2O2 decomposition via reacting with charcoal. Furthermore, this reaction showed universality to carbonaceous materials. The above results are of great value for understanding the decomposition mechanism of H2O2 and setting a reasonable target for cumulative H2O2 concentration via electrochemical oxygen reduction.

Investigation on storage stability, H2S emission and rheological properties of modified asphalt with different pretreated waste rubber powder

The use of waste rubber powder (WRP) to produce WRP modified asphalt (WRMA) has been proved to have wide application prospects, however, WRMA has poor storage stability and is prone to release H2S and other toxic fumes. Therefore, the one-step method to ameliorate these two problems through pretreating WRP was proposed, and the microwave activation, waste cooking oil (WCO) swelling and acid or alkali solution soaking were applied to pretreat WRP in this study, respectively. The scanning electron microscope and infrared spectroscopy were selected to analyze the microstructures and functional groups of different pretreated WRP. The fluorescence microscopy and hot tube test were employed to evaluate the compatibility of pretreated WRP with asphalt. The H2S gas detector and gas chromatography-mass spectrometry were introduced to research the flue gas emissions of pretreated WRP and prepared WRMA. The experimental results show that the microstructure and functional groups of the pretreated WRP are greatly changed and its surface activity is increased. The storage stability of WRMA prepared with pretreated WRP is obviously improved, and the optimized result is obtained with the microwave/WCO composite treatment, with a segregation index reduction of 40.91%. Also, the pretreatment of WRP does reduce H2S and flue gas emissions. The cumulative H2S concentration reduction of WRP after NaOH solution soaked reaches 32.14% at 30 min, and the total flue gas concentration reduction of the prepared WRMA reaches 21.54%. The results could offer guidance for the clean utilization of WRP, the efficient storage of WRMA and the effective suppression of its flue gas.

Environmental assessment of phosphogypsum: A comprehensive geochemical modeling and leaching behavior study

Understanding the variations in the geochemical composition of phosphogypsum (PG) destined for storage or valorization is crucial for assessing the safety and operational efficacy of waste management. The present study aimed to investigate the environmental behavior of PG using different leaching tests and to evaluate its geochemical behavior using geochemical modeling. Regarding the chemical characterization, the PG samples were predominantly composed of Ca (23.03–23.35 wt%), S (17.65–17.71 wt%), and Si (0.75–0.82 wt%). Mineralogically, the PG samples were primarily composed of gypsum (94.2–95.9 wt%) and quartz (1.67–1.76 wt%). Moreover, the automated mineralogy revealed the presence of apatite, fluorine and malladrite phases. The overall findings of the leaching tests showed that PG could be considered as non-hazardous material according to US Environmental Protection Agency limitations. However, a high leachability of elements at a L/S of 2 under acidic conditions ([Ca] = 166.52–199.87 mg/L, [S] = 207.9–233.59 mg/L, [F] = 248.62–286.65 mg/L) is observed. The weathering cell test revealed a considerable cumulative concentration over 90 days indicating potential adverse effects on the nearby environment (S: 8000 mg/kg, F: 3000 mg/kg, P: 700 mg/kg). Based on these results, it could be estimated that the surface storage of PG could have a serious impact on the environment. In this context, a simulation model was developed based on weathering cell results showed encouraging results for treating PG leachate using CaO before its disposal. Additionally, PHREEQC was used to analyze the speciation of major elements and calculate mineral phase saturation indices in PG leaching solutions. The findings revealed pH-dependent speciation for Ca, S, P, and F. The study identified gypsum, anhydrite, and bassanite as the key phases governing the dissolution of these elements.

The long-term leaching behavior of heavy metals in geopolymers and Portland cement bricks containing MSWI fly ash: A comparative study

Geopolymers was considered as an ideal alternative to cement solidification/stabilization for municipal solid waste incineration fly ash (MSWI FA). However, the long-term leaching behavior of heavy metals in geopolymers had attracted less attention. In this study, the long-term leaching behavior of heavy metals in geopolymers containing MSWI FA was investigated and compared with Portland cement bricks under various corrosion scenarios. The findings revealed a consistent trend of "slowly increasing - slowly decreasing - gradually stabilizing" in the pH changes in the effluent of all samples and the absence of corrosive risk in the utilization of geopolymers. The maximum pH values of the effluent were G2 (12.00) > G1 (11.90) > G3 (10.83) > C1 (9.67), suggesting that geopolymers were not corrosive in resource utilization. The long-term leaching behavior of heavy metals under different corrosion conditions could be divided into two stages, which included quick release in stage Ⅰ and gradual stabilization in stage Ⅱ. Compared with Portland cement bricks, the cumulative leaching concentration of heavy metals in geopolymers was lower, indicating less environmental risk. Due to the strongest corrosiveness from simulated acid rain (SAR), C2 and G2 exhibited significant compressive strength loss rates of 20.2% and 9.25%, respectively. In the leaching of CO2-saturated water (CSW), the leaching behavior of heavy metals was mainly regulated by the nucleation-dissolution trade-off of carbonates, however the dissolution mechanism of heavy metals in SAR could be summarized as follows: (1) corrosion/replacement of H+, and (2) counter-ion effect. this study will promote the resource utilization of MSWI FA. In a word, this work systematically studied the long-term environmental risk of geopolymers, which was beneficial to the resource utilization of MSWI FA.