Sulfate Formation Research Articles

20 Trace metal homeostasis in growing cattle

Abstract Apparent trace metal absorption and tissue retention upon incremental levels of supplemental Zn, Cu, and Mn were studied in growing cattle. A total of 60 Holstein bulls were enrolled for the study and fed for 28 d a diet consisting of barley straw (15%), molasses (10%) and pelleted concentrate (75%; Zn = 78 ppm, Cu = 15 ppm, Mn = 91 ppm). Thereafter, 20 bulls were randomly selected and slaughtered for determination of baseline tissue trace metal composition. The remaining 40 bulls [body weight (BW) = 394 ± 20 kg] were then blocked based on BW in 8 blocks of 5 bulls each. Bulls within a block were randomly assigned one of the diets differing in supplemental levels of Zn, Cu, and Mn (all from sulfate form) with the following dietary contents of Zn, Cu and Mn, respectively: No supplement (38, 7, and 47 ppm), Dose 1 (61, 11, and 68 ppm), Dose 2 (78, 15 and 91 ppm), Dose 3 (123, 26, 136 ppm) or Dose 4 (195, 43, and 214 ppm). These diets were fed for 12 wk, and complete collection of feces and urine were performed on wk 4, 8 and 12 for assessment of trace metals balance and apparent absorption. Gastrointestinal tissues, whole organs (heart, liver, spleen, and kidney), bile, cervical vertebra, and tibia were collected at slaughterhouse from all bulls. All samples were dried, ground, and analyzed for minerals. Data were processed using dietary treatment as a continuous variable and also as categorial variable. Both approaches adjusted for the fixed effect of block (Proc Mixed, SAS 9.4). Whole-body Zn, Cu and Mn balance quadratically increased (P < 0.05) with supplementation, with a significantly higher values for Dose 4 compared with all other dietary treatment (Figure 1, P < 0.05). Dose 4 also led to a 2-fold increase in urinary Zn and Cu excretions (P < 0.05), and a 4-fold increase in urinary Mn excretion (P < 0.01). Although magnitudes of change were moderate (8 to 15%), increasing dietary Zn supply linearly increased spleen Zn content (P = 0.03), and tended to increase ruminal and hepatic Zn content (P < 0.10). Hepatic Cu linearly increased from 264 to 667 mg/kg DM with increasing dietary Cu supply (P < 0.01), whereas Cu concentration in bile only increased at Doses 4 and 5 (P < 0.01). Increasing Mn supply resulted in quadratic increase of ruminal and biliary Mn content from 340 to 1140 mg/kg DM, and from 0.32 to 1.38 mg/L, respectively. Small intestine and cecum Mn concentrations linearly and quadratically increased (about 2-fold increase, P < 0.05) with incremental supply of Mn. Homeostatic regulation mechanisms were apparently overwhelmed at the greatest Zn, Cu and Mn supplementation levels evaluated in this study.

Transformation and control of organic sulfur during pyrolysis of sludge under conditions relevant to smoldering combustion: Role of oxygen and CaO

This study focused on the effect of oxygen (0–15 %) and 5 % CaO addition on the organic-S control and transformation behavior during pyrolysis (400–600 °C) of sludge under the conditions relevant to smoldering combustion. The results show that oxygen inhibits the total emission of gaseous sulfur (decreased by 25.6–36.9 %). At low temperatures (<500 °C), oxygen enhances the oxidation of aliphatic-S, aromatic-S/thiophene-S, and sulfide-S, leading more sulfur retains in the form of sulfone-S and sulfate-S in char products, also migrates to water-soluble products (especially sulfone-S). At high temperatures (>500 °C), the formed sulfur species in char products mainly further decompose into water-soluble sulfone-S, and partially generate SO2. After the addition of CaO during oxidative pyrolysis, the synergistic promotion effect on the sulfur fixation in char products is found, mainly due to the generation of more amount of stable sulfone-S and sulfate-S in char products. This leads to a decrease in gaseous sulfur by 12.4–14.6 % and an increase in sulfur content of char products by 31.3–202.9 %.

Morphology and chemical composition of mineral particles in a special dust storm with high relative humidity in North China

A special dust storm characterized by high PM10 mass concentrations (921.9 ± 632.3 μg m−3) and high relative humidity (RH; 60.1 % ± 11.1 %) was observed on March 22–24, 2023 at a coastal city of North China. Aerosol particles of PM10 were analyzed by a scanning electron microscope coupled with energy dispersive X-ray and an ion chromatograph. The results showed that individual mineral particles were dominated by clay minerals, followed by quartz, feldspar, and carbonate. Bulk water-soluble inorganic ions analysis showed that SO42- mass concentrations varied from 3.7 μg m−3 to 23.3 μg m−3 with an average value of 12.4 μg m−3. However, their mass ratios to PM10 were relatively stable, being 1.15–2.01 % with an average value of 1.49 % ± 0.25 %, similar to the value near the dust sources (Tengger Desert). Although S-containing individual mineral dust varied from 5.2 % to 70.7 %, the average weight ratio of S on individual mineral dust was 2.1 %, much lower than that of non-dust periods (11.0 %). The results suggested limited sulfate formation on mineral dust surfaces even under high RH. In contrast, NO3-, which was very limited in dust sources, varied from 0.21 % to 4.11 % of the total PM10 with an average value of 1.61 % ± 1.07 %. The research highlighted that nitrate formation has exceeded sulfate formation during severe dust storm episodes, which might because the atmospheric compositions in China have changed significantly with a high mass ratio of NO2/SO2 after the implementation of the strict emission control measures.

Microwave digestion method for sulfide analysis of Çanakkale region coal

ABSTRACT Quantitative analysis of sulfide content in coal is a necessary step for complete analysis. Conventional analysis methods take several days, whereas it takes a few hours in microwave digestion method. In the present study, a new wet chemical analysis technique was developed and applied to quantify the sulfide content in Turkish coal samples. In the initial step, 5 M HCl solution is employed to dissolve the sulfate phases present in the coal. Subsequently, pyrite is separated from the residue obtained in stage 1 through the utilization of 2 M HNO3 solution. The final stage involves the determination of organic sulfur, wherein concentrated HNO3, HCl, HF, and boric acid are utilized to completely decompose the remaining residue from stage 2. The extracted solutions from each stage are promptly analyzed for sulfur content using ICP-OES. The cumulative values of the three sulfur forms consistently correspond with certified total sulfur data for the majority of the examined coals. Among several advantages, the analysis duration is the most distinctive feature. Chemical analysis of sulfide in coal with microwave analysis method completed three times rapid than with conventional analysis.

Application of X-ray Spectroscopic Techniques to Determine the Inorganic Composition and Sulfur Chemical Speciation of the Amazonian Plant Bixa orellana

Bixa orellana is a plant that has a variety of uses, such as applications in the food and cosmetic industries, as well as culinary uses, and body painting for Indigenous people. Despite its versatility, few studies have explored its inorganic composition, and its sulfur chemical speciation has only been assessed from the point of view of sulfurous amino acids. Here, we report on the inorganic composition of Bixa orellana fruits, pericarps, and seeds obtained using Wavelength Dispersive X-ray Fluorescence (WD-XRF) and sulfur chemical speciation using X-ray Absorption Near-Edge Structure (XANES). Our results show that the seed is a source of potassium, calcium, magnesium, and phosphorous. But also, the pericarp, which is considered waste, contains a high amount of nutrients. From the XANES measurements, the distribution of the oxidation state of the sulfur atom was obtained, and it was shown that although several oxidation states of sulfur are present, oxidized sulfur (sulfate) is the dominant form of sulfur in all samples.

Jarosite formation in Permian-Triassic strata at Xiakou (South China): Implications for jarosite precipitation from H2S upwelling on Mars

Abstract The source of sulfuric acid and associated aqueous alteration of ancient martian sedimentary rocks remain under debate in the context of divergent models of jarosite formation. Here, we report the formation of sulfates, including jarosite in K-bentonites within shallow-water facies of the Permian-Triassic (P-T) transition at Xiakou in South China. In these strata, jarosite is dispersed in the clay matrix or forms aggregates in pore spaces, has a euhedral morphology, and coexists with variably 34S-depleted paragenetic gypsum and bassanite (δ34S = –37.23‰ to +3.20‰ VCDT). Subaqueous alteration of volcanic tuffs concurrently with oxidation of upwelled, biogenically sourced H2S is the process of jarosite formation in the Xiakou K-bentonites. This mechanism of jarosite precipitation and stability over geological time challenges the long-held view of acidic, water-limited conditions leading to iron(III) sulfate precipitation and would be consistent with possible microbial or nanobial life on early Mars.

Reduced sulfur compound formation from a leachate-saturated zone under changing temperature conditions

In the leachate-saturation zone of landfills, sulfate reduction is influenced by temperature and electron donors. This study assessed sulfate reduction behaviors under varied electron donor conditions by establishing multiple temperature variation scenarios based on stable temperature fields within the leachate-saturation zone. The results showed that temperature variations altered the microbial community structure and significantly influenced the sulfate reduction process. A more pronounced effect was observed with a temperature difference of 30 °C compared to one of 10 °C. In addition, sulfate reduction was influenced by the presence of electron donors and acceptors. In the middle and low-temperature regions (35 °C and 25 °C), sulfate reduction reaction of acidic organic matter was more significant, while alcohol and saccharide organic substances were more effective in promoting sulfate reduction at high-temperature regions (55 °C). Notably, a 30 °C temperature difference within the leachate-saturation zone significantly altered the microbial community structure, which influenced the sulfate reduction behavior. In particular, Firmicutes and Synergistota played essential roles in mediating the variance in sulfate reduction efficiency with a 30 °C decrease and 30 °C increase, respectively. The results also revealed that temperature changes within landfills were influenced by leachate migration, therefore, controlling leachate recharge can help prevent secondary risks associated with sulfate reduction processes.

Carbon nitride nanosheets induce pulmonary surfactant deposition via dysfunction of alveolar secretion and clearance

Graphitic carbon nitride is a new type of carbon-based nanomaterial with superior properties and great potential for application, which raised great concerns about their environmental and occupational exposure. Graphitic carbon nitride has been reported to accumulate in the lung potentially, however, the respiratory hazard effect of graphitic carbon nitride is still unknown. In the present study, we reported that graphitic carbon nitride (g-CN) and its doped variant sulfur doped graphitic carbon nitride (S-g-CN) nanosheets inhalation induced pulmonary inflammation, increased the production of pulmonary surfactant in alveolar type II epithelial cells, accompanied by the upregulation of lipids transporter expression levels in alveolar macrophages to clear excessive pulmonary surfactant in the alveolar. Further investigation found that the internalization of g-CN and S-g-CN prevented lipid phagocytosis and metabolic processes in alveolar macrophages, ultimately leading to the deposition of proteins and phospholipids in the lung. Furthermore, we found that g-CN was more robust in inhalation toxicity compared to sulfur doped form, which meant the doping of sulfur in graphitic carbon nitride reduced hazardous effects on the respiratory system. In summary, our study demonstrated that inhalation of graphitic carbon nitride nanosheets caused the deposition of pulmonary surfactants in lung, providing an insightful reference for pulmonary toxicity assessment of graphitic carbon nitride.

Response Enhancement in High-Temperature H2S-Treated Metal Oxide Gas Sensors.

Metal oxide gas sensors (MOGS), crucial components in monitoring air quality and detecting hazardous gases, are well known for their poisoning effects when exposed to certain gas molecules, such as hydrogen sulfide. Surprisingly, our research reveals that high-temperature H2S treatment leads to an enhancement effect rather than response decay. This study investigates the time-decaying response enhancement, being attributed to the formation of metal sulfide and metal sulfate on the metal oxide's surface, enhancing the electronic sensitization. Such an enhancement effect is demonstrated for various gases, including CO, CH3CH2OH, CH4, HCHO, and NH3. Additionally, the impacts of H2S treatment on the response and recovery time are also observed. Surface compositional analysis are conducted with X-ray photoelectron spectroscopy. A proposed mechanism for the enhancement effect is elaborated, highlighting the role of electronic sensitization and the sulfide-sulfate component. This research offers valuable insights into the potential applications of metal oxide sensors in sulfide-presented harsh environments in gas sensing, encouraging future exploration of optimized sensor materials, operation temperature, and the development of hydrogen sulfide poisoning-resistant and higher sensitivity MOGS.

Impact on the incorporation of metals in physicochemical and antimicrobial properties in films based on arrowroot starcha

New biodegradable packaging has been developed from renewable sources, mainly of vegetable origin. Arrowroot starch has been recently used to produce high-quality biodegradable films capable of behaving well when incorporating oils, extracts, metal, and metal nanocomposites. The study aimed to verify the impact of incorporating metals in the sulfate and chloride forms in a biopolymeric matrix from arrowroot starch in terms of biodegradability, physicochemical and microbiological parameters. Different arrowroot films were produced to incorporate solutions with a concentration of 1 Mol L-1 of sulfate and chloride metals. The action of biodegradability in soil, UV transmittance, and visible light were observed in UV-Vis spectrophotometry and antimicrobial action on Escherichia coli, Staphylococcus aureus, Salmonella serovar Typhimurium, and Salmonella serovar Enteritidis. Good results were obtained, such as biodegradability time between 81.70 to 100 % (30 days), a low transmission rate of UV radiation and visible light between 250 to 890 nm, high capacity for bacterial inhibition between 22.08 to 10.05 mm for E. coli, among 25.59 to 11.10 mm for S. aureus, between 22.14 to 11.66 mm for S. serovar Typhimurium and between 21.11 to 8.26 mm for S. serovar Enteritidis. It is concluded that the biodegradable films of arrowroot starch incorporated with metals showed potential in all the evaluated tests, thus characterizing possible new products for different uses, such as low time available in the environment, preservation of the characteristics of special products, and antimicrobial capacity.

Extraction of arsenic from fine dust of copper smelters by reduction roasting with natural gas

One of the current trends in the complex processing of fine dust from copper smelters is their direct leaching with sulfuric acid. As practical results show, high reliable technological parameters are not achieved due to the high content of arsenic in dust. During sulfuric acid leaching of dust, arsenic is distributed between the lead cake and the solution at a ratio of 40 and 60%, respectively. The redistribution of arsenic between leaching products significantly reduces the technological performance and leads to the accumulation of arsenic in the technological scheme. The paper presents the results of comprehensive studies of the elemental and phase composition of fine dust from one of the copper smelters in Kazakhstan. In the initial dust, along with the main phases presented in the form of lead and zinc sulfate, the following typical components were found: oxides of copper, lead, zinc and copper and zinc ferrites. Arsenic is found in two forms—As(III) and As(V). The laboratory installation and technique for conducting reduction roasting of dust with natural gas are presented. The influence of roasting duration, temperature and natural gas consumption on the extraction of arsenic from dust was studied. It has been established that almost complete, up to 99%, extraction of arsenic from dust is achieved with optimal technological roasting parameters: duration τ = 40 min.; natural gas consumption is 1.5 times higher than the stoichiometrically required amount for the reduction of As2O5, and temperature 500 °C.

Hydrothermal carbonization of sewage sludge for hydrochar valorization: Role of feedwater pH on sulfur removal and transformation

Adjusting the pH value is a useful method to improve the hydrochar properties during hydrothermal carbonization (HTC). The distribution of various sulfur species in hydrochar is considered as an important parameter affecting its further utilization. Nevertheless, the detailed effects of pH on the redistribution of different sulfur forms are still unknown. This study investigated the sulfur transformation pathways during HTC of sewage sludge with different feedwater pH (0–14) at 220 °C. Both acidic and alkaline feedwater facilitate the conversion of organic sulfur from the hydrochar into the stable species in aqueous products (i.e., sulfate-S). The latter especially leads to a decreased sulfur retention ratio of 31.97 % at pH=0 and 60.13 % at pH=14. Under acidic conditions, organic sulfur species such as sulfone-S and aliphatic-S undergo enhanced cyclization to form aromatic-S/thiophene-S in aqueous and hydrochar products; additionally, the oxidation of sulfone-S predominates the generation of sulfate-S in aqueous products at pH < 1. Under alkaline conditions, the aromatic-S/thiophene-S can be further oxidized into sulfate-S in aqueous products at pH>13. Furthermore, the interaction between water-soluble sulfate-S and hydrolytic intermediates (i.e., glucose, heterocyclic compounds) is intensified at pH=14, resulting in increased formation of sulfone-S and sulfite-S in aqueous products. The insights gained from this study can offer guidance for controlling sulfur distribution during HTC by adjusting the feedwater pH.

Water–Rock reactions in the acid leaching of Uranium: Hydrochemical characteristics and reaction mechanisms

Acid in–situ leaching (AISL) mining is used to recover uranium from sandstone using sulphuric acid. However, the evolution of groundwater hydrochemistry, the water–rock reaction mechanisms, and their relationship remain elusive. To effectively address these issues, ore samples were obtained from a sandstone uranium deposit in Inner Mongolia in this work. Soaking tests at different sulphuric acid concentrations were performed to quantify the mining aquifer’s water–rock reaction processes (sulphuric acid and minerals) according to the hydrogeochemical composition analysis and inverse modelling. From our results, it was demonstrated that the water–rock interactions between the sulphuric acid and gangue minerals primarily affect the leachate’s chemical composition. The introduction of sulphuric acid efficiently facilitates the gangue mineral dissolution and the groundwater total dissolved solids (TDS) increases and enhances the formation of uranyl sulphate (predominantly UO2SO4 and UO2(SO4)22– and UO22+, thus stimulating uranium mobility. Mineral precipitation (mirabilite) is primarily responsible for the elevated TDS in the leachate. The leachate’s oxygenation mainly depends on the sulphuric acid concentration and Fe3+ concentration produced by hematite dissolution. During the AISL process, the dissolution of dolomite, calcite, FeO, hematite, pyrite, K–feldspar, anorthite, chlorite, and alunite take place in the groundwater system. In parallel, the precipitation of kaolinite, illite, Ca–Montmorillonite and mirabilite, accompanied by Na–K exchange and Na–Mg exchange occur. The dissolution of dolomite, calcite and illite and Na–Mg exchange mostly affects the hydrochemical evolution, as well as the leachate of Fe mainly from dissolved chlorite. The predominant precipitates were kaolinite and mirabilite, with their precipitation ability increasing with acidity. These findings highlight the importance of clarifying the relationship between the hydrochemical characteristics and the water–rock reaction mechanisms in AISL geochemical processes to elucidate the hydrochemical evolution and mineral corrosion characteristics of ore–bearing aquifers. Finally, K–feldspar, alunite, chlorite, anorthite and dolomite were obtained as the major acid–consuming minerals. Our work provides a novel evaluation method for the prediction of acid consumption that can be used for actual production.

Rock-forming feldspathoids of the sodalite–sapozhnikovite series from the Lovozero alkaline complex (Kola peninsula, Russia): isomorphism, thermal and radiation-induced transformations and genetic mineralogy

Sulfur-enriched sodalite-group feldspathoids from the Lovozero alkaline complex (Kola peninsula, Russia) and products of their laboratory, anthropogene, and natural thermal and radiation-induced transformations were studied using EMPA, single-crystal XRD, and Raman, IR, ESR and optical spectroscopy. Sodalite Na8[Al6Si6O24]Cl2 and sapozhnikovite Na8[Al6Si6O24](HS)2 form a continuous isomorphous series [with the Cl:HS ratio variation (in mol.%) from Cl100(HS)0 to Cl12(HS)88] in highly agpaitic feldspathoid syenites and their pegmatites. In Lovozero, hydrosulfide anion HS— turned out the major form of sulfidic sulfur occurrence in minerals of this group including sodalite-hackmanite. It is found that sapozhnikovite and HS-rich sodalite are important rock-forming minerals of some Lovozero rocks; a new rock, poikilitic nepheline-sapozhnikovite syenite was discovered. Sapozhnikovite and intermediate members of the sodalite–sapozhnikovite series are the sensitive geochemical indicator, an oxymeter which indicates reducing conditions of mineral formation. Under heating, HS− anion in sodalite-sapozhnikovite series minerals destroys and sulfur forms polysulfide groups: radical anion S2●− (500–600 °C) and further radical anion S3●− (700 °C and above). The S3●− groups also appear in the result of radiation-induced transformation of these minerals. Under natural radioactive irradiation at the contact with Th-enriched steenstrupine, an intermediate member of the sodalite-sapozhnikovite series transformed to an earlier unknown in nature S3●−-rich variety of sodalite with the simplified formula Na8[Al6Si6O24][Cl,(S3)].

(Invited) Probing the Reaction Microenvironment during Electrochemical Nitrate Reduction to Ammonia

Nitrate pollution of wastewater from agricultural runoff and industrial waste streams is common around the globe. Nitrate negatively impacts the environment through harmful algal blooms and can be dangerous for human consumption. Strict limits have been set on nitrate discharge and the concentration in drinking water (< 50 ppm). Nitrate is currently removed from water by conversion to nitrogen through a biological process that requires chemical inputs (e.g., methanol) and post-treatment to remove biomass and organics.Electrochemical reduction of nitrate (NO3RR) to ammonia can remove nitrate from water and is an alternative to Haber-Bosch (HB) ammonia production, a significant source of global CO2 emissions. Ammonia is an important chemical precursor with potential applications in sustainable energy as a fuel or H2 carrier, or can be used as a fertilizer in the form of ammonium sulfate. This research addresses the water–energy nexus by converting nitrate to a valuable product, off-setting the cost of water treatment, and reducing demand for HB.NO3RR can be done from small to large scales, use renewable electricity, and eliminate the need for expensive and hazardous chemicals. However, NO3RR processes must exhibit selectivity toward ammonia to avoid the formation of other undesired products and occur at a low overpotential to minimize operating costs from electricity. To address these challenges, we must understand the reaction environment at the electrode–electrolyte interface, where heterogeneous electrochemical reactions occur. We use in situ attenuated total reflectance–surface-enhanced infrared adsorption spectroscopy (ATR–SEIRAS) to investigate the adsorbed reactants, intermediates, and interfacial pH. We studied the repeatability of the technique for in situ interfacial pH measurement and recommend controls to the community when using this method. The ATR–SEIRAS results are correlated with electrochemical experiments measuring NO3RR selectivity, activity, and efficiency. NO3RR products are measured by ion chromatography and gas chromatography. Our results relate bulk electrolyte properties with interfacial properties, and interfacial properties with reaction activity and selectivity. This understanding could lead to the development of electrolyte engineering strategies to optimize ammonia production in electrochemical NO3RR.

Formation of Inorganic Sulfate and Volatile Nonsulfated Products from Heterogeneous Hydroxyl Radical Oxidation of 2-Methyltetrol Sulfate Aerosols: Mechanisms and Atmospheric Implications.

Chemical transformation of 2-methyltetrol sulfates (2-MTS), key isoprene-derived secondary organic aerosol (SOA) constituents, through heterogeneous hydroxyl radical (•OH) oxidation can result in the formation of previously unidentified atmospheric organosulfates (OSs). However, detected OSs cannot fully account for the sulfur content released from reacted 2-MTS, indicating the existence of sulfur in forms other than OSs such as inorganic sulfates. This work investigated the formation of inorganic sulfates through heterogeneous •OH oxidation of 2-MTS aerosols. Remarkably, high yields of inorganic sulfates, defined as the moles of inorganic sulfates produced per mole of reacted 2-MTS, were observed in the range from 0.48 ± 0.07 to 0.68 ± 0.07. These could be explained by the production of sulfate (SO4 •-) and sulfite (SO3 •-) radicals through the cleavage of C-O(S) and (C)O-S bonds, followed by aerosol-phase reactions. Additionally, nonsulfated products resulting from bond cleavage were likely volatile and evaporated into the gas phase, as evidenced by the observed aerosol mass loss (≤25%) and concurrent size reduction upon oxidation. This investigation highlights the significant transformation of sulfur from its organic to inorganic forms during the heterogeneous oxidation of 2-MTS aerosols, potentially influencing the physicochemical properties and environmental impacts of isoprene-derived SOAs.

Fertility and ecotoxicological condition of light gray forest soils of the Ivanovo region

The results oflong-term monitoring of light gray forest soil for agricultural purposesin theIvanovo region are presented, which was carried outto establish the level of fertility according to the mainagrochemical indicators, the content of mobile forms of trace elementsand sulfur, the ecotoxicological state according to the content ofgross and mobile forms of heavy metals, arsenic, caesium-137 andstrontium-90.The average values of the indicators, their levels ofchange and trends in changes in the metabolic and hydrolyticacidity of the soil, availability of organic matter, mobile formsof nitrogen, phosphorus, potassium, exchangeable calcium, magnesium and other bases,mobile forms of boron, copper, zinc, molybdenum, cobalt, manganese andsulfur have been established.According to the content of traceelements in the soil, the needs for the use ofmicronutrients are determined.Changes, concentrations and trends in the mobileforms of cadmium, lead, copper, zinc, nickel, chromium, mercury andarsenic in the soil have been determined.The study establishedbackground values, changes and trends in the specific activities ofcaesium-137 and strontium-90, the density of their contamination of thesoil of the site and the power of the exposuredose of gamma radiation.According to thePearson–Spearman correlation coefficients,the peculiarities of the influence of the content of organicmatter, the level of acidity and the capacity of cationexchange on the content of mobile forms of trace elements,sulfur, gross and mobile forms of metals and radionuclides wereestablished.

Constraining sulfur incorporation in calcite using inorganic precipitation experiments

The sulfur over calcium ratio (S/Ca) in foraminiferal shells was recently proposed as a new and independent proxy for reconstructing marine inorganic carbon chemistry. This new approach assumes that sulfur is incorporated into CaCO3 predominantly in the form of sulfate (SO42−) through lattice substitution for carbonate ions (CO32–), and that S/Ca thus reflects seawater [CO32–]. Although foraminiferal growth experiments validated this approach, field studies showed controversial results suggesting that the potential impact of [CO32–] may be overwritten by one or more parameters. Hence, to better understand the inorganic processes involved, we here investigate S/Ca values in inorganically precipitated CaCO3 (S/Ca(cc)) grown in solutions of CaCl2 − Na2CO3 − Na2SO4 − B(OH)3 − MgCl2. Experimental results indicate the dependence of sulfate partitioning in CaCO3 on the carbon chemistry via changing pH and suggest that faster precipitation rates increase the partition coefficient for sulfur. The S/Ca ratios of our inorganic calcite samples show positive correlation with modelled [CaSO40](aq), but not with the concentration of free SO42− ions. This challenges the traditional model for sulfate incorporation in calcite and implies that the uptake of sulfate potentially occurs via ion-ion pairs rather than being incorporated as single anions. Based on the [Ca2+] dependence via speciation, we here suggest a critical evaluation of this potential proxy. As sulfate complexation seems to control sulfate uptake in inorganic calcite, application as a proxy using foraminiferal calcite may be limited to periods for which seawater chemistry is well-constrained. As foraminiferal calcite growth is modulated by inward Ca2+ flow to the site of calcification coupled to outward H+ pumping, sulfate incorporation as CaSO40 ion-pair in the foraminifer’s shell also provides a mechanistic link for the observed relationship between S/Ca(cc) and [CO32–].

In-situ inhibition mechanism of SO3 formation over MoS2 modified V2O5/TiO2 catalyst within selective catalytic reduction process

The utilization of commercial vanadium-titanium based catalysts (V2O5/TiO2) within the selective catalytic reduction (SCR) process is a prominent contributor to the emergence of sulfur trioxide (SO3) in coal-fired boiler environments. The direct modification of vanadium-titanium based catalysts has big potential to be an efficacious strategy for in-situ inhibiting SO3 formation. This research evaluates the effectiveness of MoS2 modified V2O5/TiO2 catalyst on SO2 oxidation under diverse conditions, using controlled condensation for SO3 collection. The results showed that V2O5-MoS2/TiO2 catalysts outperformed conventional V2O5/TiO2 catalysts in inhibiting the oxidation from SO2 to SO3 between 200 and 400 °C, with optimal performance at 350 °C. No significant effect was observed on the catalytic oxidation of SO2 when the O2 concentration was lower than that of SO2, whereas the introduction of appropriate quantities of NO promoted the generation of SO3. The excessive inclusion of NH3 nearly doubled the SO3 generation rate, increasing it from 0.284 % to 0.434 %. The NO and NH3 mixture markedly reduced SO3 generation to 0.085 % at a 62 mL/min mixture concentration, just 30 % of the rate without the mixture. Following the reaction of SO2 and O2, the reacted catalyst exhibited reduced pore volume, enhanced thermochemical stability, and lower susceptibility to SO2 catalytic oxidation. The addition of low-valence sulfur improves catalyst reducibility, reduces V5+–OH reactions in various atmospheres, and decreases the formation of sulphate and gaseous SO3. The Mo-S-Mo group also effectively prevents the formation of HSO4− intermediates. Additionally, MoS2 reacts with SO3 via a reduction reaction, significantly lowering the SO3 levels. Finally, in diverse atmospheric conditions, the catalysts maintained their V5+ content and catalytic efficiency, thus improving SCR performance stability.

Can we reach consensus on the dominant sulfate formation pathway in China's haze?

Atmospheric sulfate aerosols contribute significantly to air pollution and climate change. Sulfate formation mechanisms during winter haze events in northern China have recently received considerable attention, with more than 10 studies published in high-impact journals. However, the conclusions from in-field measurements, laboratory studies, and numerical simulations are inconsistent and even contradictory. Here, we propose a physically based yet simple method to clarify the debate on the dominant sulfate formation pathway. Based on the hazes evolving in the synoptic scale, first, a characteristic sulfate formation rate is derived using the Eulerian mass conservation equation constrained by in situ observations. Then, this characteristic value is treated as a guideline to determine the dominant sulfate formation pathway with a 0D chemical box model. Our observation-derived results establish a linkage between studies from laboratory experiments and chemical transport model simulations. A convergent understanding could therefore be reached on sulfate formation mechanisms in China's wintertime haze. This method is universal and can be applied to various haze conditions and different secondary products.