Acid Neutralizing Capacity Research Articles

Land cover influence on catchment scale subsurface water storage investigated by multiple methods: Implications for UK Natural Flood Management

Study regionUnited Kingdom (UK). Study Focus‘Natural flood management’ (NFM) schemes manipulating land use and other catchment features to control runoff are increasingly promoted across the UK. Catchment water storage and mixing processes influence runoff, but our understanding of the effects of land cover change on these processes is still limited. This study combined hydrometric, isotopic and geochemical measurements to investigate land cover versus potential topographic, soil and geological controls. It compared storage-discharge dynamics in nine nested catchments within a 67 km2 managed upland catchment in southern Scotland. Storage and mixing dynamics were characterised from hydrometric data using recession analysis and from isotopic data using mean transit time and young water fraction estimates. To give information on water sources, groundwater fraction was estimated from end member mixing analysis based on acid neutralising capacity. New hydrological insightsThe analysis showed low but variable sub-catchment scale dynamic storage (16–200 mm), mean transit times (134–370 days) and groundwater fractions (0.20–0.52 of annual stream runoff). Soil hydraulic conductivity was most significantly positively correlated with storage and mixing measures, whilst percentage forest cover was inversely correlated. Any effects of forest cover on increasing catchment infiltration and storage are masked by soil hydraulic properties even in the most responsive catchments. This highlights the importance of understanding dominant controls on catchment storage when using tree planting as a flood management strategy.

Electrolytic Seawater Mineralization and the Mass Balances That Demonstrate Carbon Dioxide Removal.

We present the mass balances associated with carbon dioxide (CO2) removal (CDR) using seawater as both the source of reactants and as the reaction medium via electrolysis following the "Equatic" (formerly known as "SeaChange") process. This process, extensively detailed in La Plante E.C.; ACS Sustain. Chem. Eng.2021, 9, ( (3), ), 1073-1089, involves the application of an electric overpotential that splits water to form H+ and OH- ions, producing acidity and alkalinity, i.e., in addition to gaseous coproducts, at the anode and cathode, respectively. The alkalinity that results, i.e., via the "continuous electrolytic pH pump" results in the instantaneous precipitation of calcium carbonate (CaCO3), hydrated magnesium carbonates (e.g., nesquehonite: MgCO3·3H2O, hydromagnesite: Mg5(CO3)4(OH)2·4H2O, etc.), and/or magnesium hydroxide (Mg(OH)2) depending on the CO32- ion-activity in solution. This results in the trapping and, hence, durable and permanent (at least ∼10 000-100 000 years) immobilization of CO2 that was originally dissolved in water, and that is additionally drawn down from the atmosphere within: (a) mineral carbonates, and/or (b) as solvated bicarbonate (HCO3-) and carbonate (CO32-) ions (i.e., due to the absorption of atmospheric CO2 into seawater having enhanced alkalinity). Taken together, these actions result in the net removal of ∼4.6 kg of CO2 per m3 of seawater catholyte processed. Geochemical simulations quantify the extents of net CO2 removal including the dependencies on the process configuration. It is furthermore indicated that the efficiency of realkalinization of the acidic anolyte using alkaline solids depends on their acid neutralization capacity and dissolution reactivity. We also assess changes in seawater chemistry resulting from Mg(OH)2 dissolution with emphasis on the change in seawater alkalinity and saturation state. Overall, this analysis provides direct quantifications of the ability of the Equatic process to serve as a means for technological CDR to mitigate the worst effects of accelerating climate change.

Evaluation of the acid-neutralizing and cytotoxicity properties of novel plant mucilage used as an alternative treatment for peptic ulcers and as antacids in Namibia

Hypersecretion of gastric acid damages the stomach lining, causing the formation of peptic ulcers. Mucilage from medicinal plants offers a relaxing and soothing effect to the endodermal lining of the gut and has antacid properties, which can protect the mucosal lining from gastric acidity. This is the first report aimed to evaluate the physicochemical characteristics, acid-neutralizing, and cytotoxicity properties of traditionally used aqueous mucilage from Asparagus exuvialis and Sesamum capense. The physicochemical properties were determined by biochemical methods. Acid neutralizing and buffering capacities were determined by titration methods. Normal mouse embryonic fibroblast cells were used for cytotoxicity evaluation by MTT assay. The physicochemical characterization confirmed the presence of carbohydrates, alkaloids, saponins, proteins, tannins, flavonoids, and glycosides. Sesamum capense mucilage exhibited the most potent artificial gastric juice neutralizing capacity pH of 4.62±0.01, 8.0±0.00 acid neutralization capacity per gram of acid, and 30 minutes duration of acid neutralization. The aqueous mucilage from S. capense did not cause any significant cytotoxicity to 3T3 cell lines showing an IC50 value of 91.5 ± 0.06 μg mL-1, confirming the safe nature of the mucilage. These findings revealed that S. capense has the potential to neutralize gastric acid responsible for ulceration and can be safely consumed.

Formulation Studies to Develop Low-Cost, Orally-Delivered Secretory IgA Monoclonal Antibodies for Passive Immunization Against Enterotoxigenic Escherichia coli

Enterotoxigenic Escherichia coli (ETEC) is a common cause for diarrheal infections in children in low- and middle-income countries (LMICs). To date, no ETEC vaccine candidates have been approved. Passive immunization with low-cost, oral formulations of secretory IgA (sIgA) against ETEC is an alternative approach to protect high-risk populations in LMICs. Using a model sIgA monoclonal antibody (anti-LT sIgA2-mAb), the stability profiles of different formulations were assessed during storage and in in vitro digestion models (mimicking in vivo oral delivery). First, by employing various physicochemical techniques and a LT-antigen binding assay, three formulations with varying acid-neutralizing capacity (ANC) were evaluated to stabilize sIgA2-mAb during stress studies (freeze-thaw, agitation, elevated temperature) and during exposure to gastric phase digestion. Next, a low-volume, in vitro intestinal digestion model was developed to screen various additives to stabilize sIgA2-mAb in the intestinal phase. Finally, combinations of high ANC buffers and decoy proteins were assessed to collectively protect sIgA2-mAb during in vitro sequential (stomach to intestine) digestion. Based on the results, we demonstrate the feasibility of low-cost, ‘single-vial’, liquid formulations of sIgA-mAbs delivered orally after infant feeding for passive immunization, and we suggest future work based on a combination of in vitro and in vivo stability considerations.

Chemical characteristics of long-term acid rain and its impact on lake water chemistry: A case study in Southwest China

The chemical composition of acid rain and its impact on lake water chemistry in Chongqing, China, from 2000 to 2020 were studied in this study. The regional acid rain intensity is affected jointly by the acid gas emissions and the neutralization of alkaline substances. The pH of precipitation experienced three stages of fluctuating decline, continuous improvement, and a slight correction. Precipitation pH showed inflection points in 2010, mainly due to the total control actions of SO2 and NOx implemented in 2011. The total ion concentrations in rural areas and urban areas were 489.08 µeq/L and 618.57 µeq/L, respectively. The top four ions were SO42−, Ca2+, NH4+ and NO3−, which accounted for more than 90% of the total ion concentration, indicating the anthropogenic effects. Before 2010, SO42− fluctuated greatly while NO3− continued to rise; however, after 2010, both SO42− and NO3− began to decline rapidly, with the rates of -12.03 µeq/(L·year) and -4.11 µeq/(L·year). Because the decline rate of SO42− was 2.91 times that of NO3−, the regional acid rain has changed from sulfuric acid rain to mixed sulfuric and nitric acid rain. The lake water is weakly acidic, with an average pH of 5.86, and the acidification frequency is 30.00%. Acidification of lake water is jointly affected by acid deposition and acid neutralization capacity of lake water. Acid deposition has a profound impact on water acidification, and nitrogen (N) deposition, especially reduced N deposition, should be the focus of future research.

Assessment of the Acid Neutralizing Capacity and Other Properties of Antacid Formulations Marketed in the Gaza Strip

Background: Antacids are frequently used as over-the-counter (OTC) medications to reduce symptoms of dyspepsia and to neutralize stomach acidity. Evaluation of antacids efficacy depends on in vitro testing like acid neutralizing capacity (ANC) and acid neutralization potential (ANP). The purpose of this study was to examine ANC, ANP, and other characteristics of commercially available antacid formulations (both liquid and solid formulations) in the Gaza Strip. Methods: Both liquid (n=2) and solid (n=4) antacid formulations were acquired from the Gaza Strip’s central community pharmacies. Preliminary antacid test (PAT) was carried out to determine if the tested formulation is classified as antacid. The general monograph <301> in USP34/NF29 was used for the estimation of ANC, while ANP was investigated using Rossett Rice procedure. Both tests were conducted to evaluate the efficacy of antacid. In addition, cost effectiveness per formulation and statistical analysis test of data were calculated. Results: All formulations were classified as antacids because they all passed the PAT test (pH of antacid-HCl over 3.5). The ANC of antacids (n=6) varied from 8.74±0.37 to 29.14±0.84 mEq per minimum labeled dose (MLD). The ANC/MLD ratios for solid formulations were higher than those of liquid formulations. No statistically significant difference in ANC/MLD between the two groups was estimated (P˃.0.05). ANP test - the time duration during which an antacid formulation maintains pH above 3.5 - ranged from 43 to 90 minutes. According to this study liquids were inefficient in acid neutralization and expensive as a result. Conclusions: The ANC and ANP results indicated the better neutralizing efficacy and duration of solid antacids in comparison to liquids. A1 and A2 formulations– calcium and magnesium salt based solid antacids had the most appropriate properties in terms of efficacy, onset and duration of neutralizing activity. Antacids in the form of chewable tablets were the most cost-effective formulations. It is recommended to examine more batches of the same antacids and to add ANC data on the label of antacids.

Factors Influencing the Distribution of Freshwater Mollusks in the Lakes of the Pyrenees: Implications in a Shifting Climate Scenario

Climate warming is expected to drive an upward altitudinal shift of species distributions in mountain areas. In this study, we consider how environmental variables constrain the distribution of freshwater mollusks across elevations based on an extensive survey of the entire Pyrenean range. Results show that several altitude-related variables are significantly relevant for the distribution of all mollusks (i.e., temperature, sediment organic content). Others respond more precisely to some variables: fine substrate proportion increases the probability of finding Pisidium sensu lato (mostly Euglesa species), and the latter, the macrophyte presence, and Ampullaceana balthica. Despite the low acid-neutralizing capacity in many of the lakes, only the distribution of A. balthica was significantly constrained by this factor, independent from elevation. The results confirm a likely altitudinal expansion of the distributions of all species, particularly toward lakes with a summer surface temperature increasing above 12 °C. The pace of change is expected to differ among species according to different nonlinear thresholds in thermal response, which temperature value increases from Pisidium s.l. to Ampullaceana to Ancylus, and the taxon-specific sensitivity to substrates and chemical conditions.

Application of a novel Ca-Fe-Si-S composite for the synchronous stabilization of As, Zn, Cu, and Cd in acidic arsenic slag.

The control of multipleheavy metals (HMs) pollution in solid wastes, especially the co-contamination of As and other heavy metal cations, is of great importance to ecological and environmental health. To address this problem, the preparation and application of multifunctional materials have attracted wide attention. In this work, a novel Ca-Fe-Si-S composite (CFSS) was applied to stabilize As, Zn, Cu, and Cd in acid arsenic slag (ASS). The CFSS exhibited synchronous stabilization ability for As, Zn, Cu, Cd and owned strong acid neutralization capacity. Under simulated field conditions, the acid rain extracted HMs in ASSsuccessfully decreased below the emission standard (GB 3838-2002-IV category in China) after incubated by 5% CFSS for 90days. Meanwhile, the application of CFSS promoted the transformation of leachable HMs into less accessible forms, which was conductive to the long-term stabilization for HMs. There was competitive relation among the three heavy metal cations, following the stabilization sequence of Cu > Zn > Cd during incubation. And the stabilization mechanisms of HMs by CFSS were proposed as chemical precipitation, surface complexation, and ion/anion exchange. The research will be greatly conducive to the remediation and governance of field multipleHMs contaminated sites.

Comparative evaluation of Polygel Dual and commonly used alginate-antacid formulations (ACIDUAL Study)

Purpose: To compare Polygel Dual (PD) and four marketed alginate-antacid combination products, with respect to raft formation and antacid properties.
 Methods: The pharmacopeial tests used were selected based on demonstrable performance of raft-forming potential, including speed and thickness, for all selected products. Evidence-based methods were used to determine the antacid effects in terms of acid-neutralizing capacity and increase in pH.
 Results: Raft-forming ability was demonstrated by three products, with AF-4 and PD outperforming in speed and thickness. PD, AF-1 and AF-2 exhibited superior antacid properties. However, PD was the only product that demonstrated superior performance with respect to raft-formation and antacid potential. Raft-forming capacity was exhibited by 3 out of 5 products, viz, PD, AF-1 and AF-4. Raft formation was faster in AF-4 (15 s), followed by in PD (25 s). Similarly, raft thickness (14.79 mm) was highest in AF-4, followed by (4.39 mm) in PD. Preliminary antacid test results showed that AF-4 failed to raise pH above 3.5, but PD raised pH to 5.86, while AF-1 raised pH to 5.88. Similarly, periodic test analysis revealed that PD maintained pH above 7 for the entire test duration of 210 min, whereas AF-4 failed to raise pH to 7 during the test period.
 Conclusion: Polygel dual (PD) demonstrates desirable raft-forming potential and antacid properties. Moreover, it effectively raises pH and maintains it for longer duration than any of the other antacid products. Thus, PD may be considered a potentially effective treatment for acid-reflux problems. However, this claim should be validated in suitable clinical trials.

Effect of Carbide Slag Combined with Biochar on Improving Acidic Soil of Copper Sulfide Mines

Heavy metal-rich acidic soils of copper sulfide mines can easily cause harm to the surrounding environment and ecosystem safety if not treated properly. Currently, the most common method of mine ecological remediation is to improve acidic soils of copper sulfide mines by adding different types of amendments. In this paper, different dosages of biochar and carbide slag applied singly and in combination were designed to investigate the changes of physicochemical properties and ryegrass growth in the acidic soil of copper sulfide mines. Through soil incubation experiments and potting tests, different treatments explored the improvement effect of carbide slag combined with biochar on the acidic soil of copper sulfide mines. Then, it was found that 2% (w/w) carbide slag in combination with 10% (w/w) biochar had the best effect on the improvement of copper-sulfide mine acidic soil. Among them, carbide slag significantly increased the pH, cation exchange capacity (CEC) and acid neutralization capacity (ANC), and reduced the electrical conductivity (EC), net acid generation (NAG) and sulfate ion (SO42−) concentrations in the acidic soil of copper sulfide mines; biochar obviously reduced the bio-effectiveness of heavy metals Cu, Pb and Zn, and DPTA-Cu, Pb and Zn decreased by 8~80%, 7~76% and 17~79%, respectively. Apart from that, there was a positive cooperativity between carbide slag and biochar, and their application effectively controlled the acidification process and heavy metal toxicity in the acidic soil of copper sulfide mines. In summary, the results will provide a theoretical basis for the large-scale reclamation of carbide slag and biochar in improving acidic soils of copper sulfide mines, filling the gap of calcium carbide slag and biochar in soil remediation.

Remediation of Acid Mine Drainage (AMD) Using Steel Slag: Mechanism of the Alkalinity Decayed Process.

Steel slag has been proven to be an effective environment remediation media for acid neutralization, and a potential aid to mitigate acid mine drainage (AMD). Yet its acid neutralization capacity (ANC) is frequently inhibited by precipitate after a period of time, while the characteristics of the precipitate formation process are unclear yet. In this study, ANC for basic oxygen steel slag was conducted by neutralization experiments with dilute sulfuric acid (0.1 M) and real AMD. Some partially neutralized steel slag samples were determined by X-ray diffraction (XRD), scanning electron microscopy combined with an energy dispersive spectrometer (SEM-EDS), and N2 adsorption tests to investigate the potential formation process of the precipitate. The results indicated that Ca-bearing constitutes leaching and sulfate formation were two main reactions throughout the neutralization process. A prominent transition turning point from leaching to precipitate was at about 40% of the neutralization process. Tricalcium silicate (Ca3SiO5) played a dominant role in the alkalinity-releasing stage among Ca-bearing components, while the new-formed well crystalline CaSO4 changed the microstructure of steel slag and further hindered alkaline components releasing. For steel slag of 200 mesh size, the ANC value for the steel slag sample was 8.23 mmol H+/g when dilute sulfate acid was used. Neutralization experiments conducted by real AMD confirmed that the steel slag ANC was also influenced by the high contaminants, such as Fe2+, due to the hydroxides precipitate reactions except for sulfate formation reactions.

Accelerated carbonation of ball-milling modified MSWI fly ash: Migration and stabilization of heavy metals

Mechanical ball-milling is an effective technique to reduce particle size, increase lattice defects, and enhance the activity of materials. After mechanical ball-milling modification, an accelerated carbonation technology of municipal solid waste incineration fly ash (FA) was proposed. The effects of ball-milling on carbonation efficiency, heavy metals stabilization, and heavy metals leaching characteristics were investigated. The results showed that the initial carbonation efficiency of ball-milled FA (MFA) was higher than that of the original FA (OFA) because of the in-situ carbonation reaction and the stability of Pb, Cu, and Cd in MFA was improved. The carbonation reaction of MFA was conducted thoroughly by the elevated ionic strength and mass transfer efficiency. The surface of carbonated OFA (COFA) and carbonated MFA (CMFA) stacked calcium carbonation in loose strips and compact spherical respectively, relating to the initial morphology. The dechlorination of CMFA was superior to COFA because the more in-depth carbonation eluted the chlorine from Friedel’s salt. The leaching concentrations of heavy metals in CMFA were lower than those in COFA, especially the immobilization efficiency of Pb and Zn reached 99.8 % and 98.5 %, respectively, contributed by the conversion of the Pb and Zn from ionic hydroxides to stable carbonates. Due to the low acid neutralization capacity of CMFA, when the pH dropped from 7 to 5, the heavy metals carbonate chemical precipitation dissolved, and the effect of calcium carbonation on heavy metals wrapping and adsorption disappeared, therefore the subsequent disposal of CMFA should avoid an acidic environment.

Biomass ash-based soil improvers: Impact of formulation and stabilization conditions on materials’ properties

Biomass ash and sludge from pulp and paper industry have enormous potential to be recycled and used as components in soil improvers. Those materials can supply large amounts of nutrients and organic matter and its recycling avoids the need of landfilling. However, these wastes cannot be directly applied to soils. Some form of processing is required to ensure efficient soil pH correction, fertilization, guarantee soil protection, and reduce potential sanitary and environmental risks.In this study, different ash formulations (with or without addition of organic wastes) and stabilization conditions (indoors vs. outdoors) were tested to optimize physico-chemical properties of ash-based granules to be used as soil improvers. Biomass fly ash (BFA) was granulated in combination with different binding agents: distilled water, biological sludge (BS), biological sludge effluent (BSE), or composted biological sludge (CBS). All granulated materials were alkaline, ranging from pH 7.9 to 12.1. Their acid-neutralizing capacity ranged from 45 to 51 equiv. CaCO3, rendering them suitable as liming materials. Incorporation of organic materials (BS and CBS) enhanced water holding capacity (up to 38 %) and bulk porosity (up to 20 %). Stabilization outdoors resulted in a faster carbonation and consequent reduction of the granules pH. It also yielded a lower electrical conductivity and lower soluble salts content (Ca, Cl, K, and Na) than materials stabilized indoors. After processing and stabilization, some of these ash formulations fulfilled the criteria to be used as component for inorganic macronutrient fertilizers, liming materials or inorganic soil improvers under the EU Fertilizing Products Regulation.

Activating soil nitrification by co-application of peanut straw biochar and organic fertilizer in a rare earth mining soil

The intensive mining activities to extract rare earth elements from ion-adsorption rare earth deposits have introduced massive amounts of ammonium into the tailing soils in southern China. Compared to the ubiquitous soil nitrification in cropland, forest, and grassland soils, however, there is no feasible strategy to alleviate the ammonium contamination in tailing soil. Herein, the feasibility to remove ammonium by adding ammonium adsorbents (e.g., biochar, activated carbon, and zeolite), alkaline materials, and organic fertilizer to the rare earth mining soil was explored. The amendment of rice straw biochar, activated carbon, or zeolite in combination with CaCO3 and organic fertilizer showed no significant effect on ammonium removal due to their limited capacity to elevate soil pH. However, the co-application of peanut straw biochar (PSBC), CaCO3, and organic fertilizer activated both the ammonia volatilization and soil nitrification processes. Specifically, the three components functioned as follows: organic fertilizer supplied active ammonia-oxidizing bacteria (AOB); PSBC stimulated AOB proliferation by elevating soil pH above 7.75; CaCO3 ameliorated soil acidity and reduced the lag time for activating soil nitrification. The soil ammonium removal and nitrate accumulation rates were positively correlated to the acid neutralization capacity of PSBC prepared at 400 °C–800 °C. The qPCR and microbial community analysis results indicated that Nitrosomonas europaea was the dominant AOB that was responsible for enhanced soil nitrification. Our findings pave the way for developing cost-effective strategies to remediate ammonium contamination in rare earth mining soils.

Herbal Combination 'HAGE-101912' Ameliorates Gastroesophageal Reflux Disease in Rats.

Gastroesophageal reflux disease (GERD) is a chronic, relapsing disorder. In this era of modern and fast-track lifestyle and food habits, the incidence of GERD is rapidly increasing. Currently, proton pump inhibitors (PPIs) are the primary choice of treatment. However, the associated side effects and a high relapse rate give rise to the need to explore alternative therapies. The study aimed to evaluate HAGE-101912, an herbal combination, in different experimental models of GERD. Antacid activity was assessed based on H+/K+ATPase inhibitory activity of parietal cells using artificial gastric juice. Tonic contraction of the lower esophageal sphincter (LES) was evaluated using an AD Instrument. A GERD model of the pylorus and fundus ligation (preventive and curative models) in rats was selected to assess the efficacy of HAGE-101912 at a dose of 250 mg/kg body weight, and various parameters such as the gastric pH, gastric volume, total acidity, gross esophageal ulcer index, and histopathological changes were evaluated. The prokinetic activity was assessed using the phenol red method. HAGE-101912 increased the acid-neutralizing capacity (P < 0.001), decreased H+/K+ATPase activity (P < 0.01), and increased the contraction of the LES. In the preventive model, HAGE-101912 significantly reduced the gastric acid volume (P < 0.01), total acidity (P < 0.001), and gross esophageal ulcer index (P < 0.01); increased the gastric acid pH (P < 0.01); and protected the esophageal epithelium. In addition, HAGE-101912 increased gastric emptying and gastrointestinal transit through its prokinetic activity (P < 0.05). HAGE-101912 has a beneficial effect in GERD as it effectively inhibits the H+/K+ATPase, increases the gastric pH, restores the LES function, protects the esophageal epithelium, and increases gastric emptying and transit.

EFFECT OF POLYHERBAL FORMULATION OF Boerhavia diffusa, Sesbania grandiflora, Moringa olifera, AND Solanum nigrum AGAINST GASTROENTERITIS AND ITS VALIDATION USING In silico APPROACH

Boerhavia diffusa, Sesbania grandiflora, Moringa olifera, and Solanum nigrum are indigenous plants that have been used in traditional medicine for treating various gastroenteritis. The present study aimed to demonstrate the Acid-neutralizing capacity, invitro anti-urease, anti-oxidant, inhibition of lipid peroxidation ability, anti- Inflammatory, and H+/K+ ATPase inhibition activity of hydroalcoholic extract of the polyherbal formulation. The phytochemicals present in the polyherbal formulation (PHF) were identified by GC – MS analysis. The total Phenolic Content and total Flavonoid content of phytochemicals were quantified. Phytochemical interactions with the active sites of urease were supported by Molecular docking analysis. The results revealed that 0.02 mg of phenolic content and 0.013 mg of flavonoids per gram of plant extract were observed, PHF had acid- neutralizing capacity better than the standard antacid tablet, 38% of anti-urease activity towards urease enzyme, 64% of inhibition of lipid peroxidation against oxidation of lipid bilayer, 59% of inhibition of protein denaturation, 37% of haemolysis inhibition, 80% of H+/K+ ATPase inhibition activity in the goat parietal cells. There were 14 functional compounds tend to interact with the enzyme urease. But two compounds directly interacted with the active site of ureases.

Magnesium Silicate Binding Materials Formed from Heat-Treated Serpentine-Group Minerals and Aqueous Solutions: Structural Features, Acid-Neutralizing Capacity, and Strength Properties.

The influence of structural features of three serpentine-group minerals (antigorite, chrysotile, and lizardite) on the hydration of heat-treated materials and the formation of magnesium silicate binder has been studied. Initial serpentine samples have been fired in the interval 550-800 °C with a step of 50 °C; acid neutralization capacity (ANC) values have been determined for all samples. Antigorite samples (SAP) have exhibited a maximum reactivity at a temperature of 700 °C (ANC 7.7 meq/g). We have established that the acid-neutralizing capacity of chrysotile and lizardite samples in the temperature range of 650-700 °C differ slightly; the capacity varied in the interval of 19.6-19.7 meq/g and 19.6-19.7 meq/g, respectively. The samples obtained at optimal temperatures (antigorite-700 °C, lizardite, and chrysotile-650 °C) have been studied. Heat-treated serpentines have interacted with water vapor for a year; serpentine hydration has been investigated. The strength characteristics of the resulting binder agents were studied after 7, 28, 180, and 360 days. Upon hardening within 7 days, the strengths of the SAP and SCH samples have been almost the same (2.2 MPa), whereas this indicator for the SLH and SLK samples has been significantly lower (0.5 MPa). After hardening for over a year, the chrysotile sample SCH had the highest strength (about 8 MPa), whereas the strength of antigorite SAP was 3 MPa. The samples of initial, heat-treated, and hydrated heat-treated serpentines have been studied using XRD, differential scanning calorimetry, and surface texture analysis. The serpentine structure is crucial in destroying the mineral crystal lattice during heat treatment. In contrast to heat-treated chrysotile and lizardite, antigorite did not adsorb water. Structural features of chrysotile provided the highest compressive strength of the binding agent compared with antigorite and lizardite. The acid-neutralizing ability of lizardite was noticeably higher than antigorite, whereas its compressive strength was lower due to the layered mineral structure and impurities. We have established that the minerals' structural features are crucial for the hydration of heat-treated serpentines; the structure determines material utilization in various environmental technologies.

Valorization of South African Coal Wastes through Dense Medium Separation

Sustainable management of coal waste is one of the major environmental concerns for coal mining, whether active or legacy, worldwide. Coal dump deposits demand a large physical area or footprint for disposal of solid waste, change the topography, and generate both pyritic dust and acid rock drainage (ARD) where pyritic coal waste is deposited. The beneficiation of dump deposits or, preferably, of coal waste prior to its dumping can reduce or even eliminate the liabilities related to coal waste management. In this work, dense medium separation studies of coal discards, using heavy liquids, resulted in three pooled fractions from typical South African coal waste discards from the Mpumalanga region for future use: (a) a fraction of low density with increased calorific value; (b) a fraction of intermediate density, rich in ash and acid neutralizing minerals and lower in sulfur; and (c) a fraction of high density, rich in sulfidic minerals including pyrite. The fractions were characterized using particle size analysis, sink-float studies, static tests to predict ARD potential, proximateand ultimate analysis, and gross calorific value. The results showed that approximately 70% of this discard coal is composed of a material of sufficient quality for energy generation in conventional power stations. A pyrite-rich concentrate made up 2% of the total discard mass; comprising more than 45% of the sulfidic mineral present in the feed and displaying no acid neutralizing capacity (ANC). The remaining discard fraction, with intermediate density, presented potential to be used for several ends including soil fabrication, co-disposal or as aggregate material in civil engineering; additional testing to ensure applicability for the selected re-purposing option should be chosen based on proposed use.

Wet depositions of cations in forests across NADP, EMEP, and EANET monitoring networks over the last two decades

Studies focused on emissions and acid deposition of sulfur (S) and nitrogen (N) and the consequent precipitation acidity have a long history. However, atmospheric depositions of cations play a critical role in buffering precipitation acidity, and providing cationic nutrients for vegetation growth lacks sufficient studies equally. The spatiotemporal patterns of cation depositions and their neutralization potential across broad scales remain unclear. Through synthesizing the long-term data in forest sites (n = 128) derived from three monitoring networks (NADP in Northern America, EMEP in Europe, and EANET in East Asia) on wet deposition of cations (Na+, NH4-N, K+, Mg2+, and Ca2+), this study assesses the temporal changes and spatial patterns of cation depositions and their neutralization potential over the last two decades. The results showed that the depositions of cationic nutrients were considerably higher in EANET compared to NADP and EMEP. The depositions of sea salt-associated sodium exhibited a significant transition from marine (> 15 kg ha−1 year−1) to inland (< 3.0 kg ha−1 year−1) forest sites attributable to the precipitation quantity and influences of sea spray. The higher emissions of NH3 and particulate matter in East Asia explained the higher cation depositions in EANET than NADP and EMEP. The annual trends of cations revealed that only 20–30% of the forest sites showed significant changing trends and the sites widely spread across the three networks. Possibly, base cation (BC) deposition has reached a low and stable condition in NADP and EMEP, while it has high spatial heterogeneity in the temporal change in EANET. The difference in BC deposition among the three networks reflects their distinct development of economy. Our synthesis indicates that the annual trends of neutralization factor (NF) in NADP can be explained by the declining of acid potential (AP), not by neutralization potential (NP) as BC deposition has been stably low over the past two decades. Whereas, the concurrent decreases of AP and NP in EMEP or plateau period of both AP and NP in EANET have come to a standstill of acid neutralizing capacity.

Development of Lake from Acidification to Eutrophication in the Arctic Region under Reduced Acid Deposition and Climate Warming

Small lakes are potentially effective environmental sensors; they react quickly to anthropogenic stressors. We studied the long-term response of water chemistry to reduced acid deposition and climate warming in the Kola Arctic region of Russia based on monitoring data from 75 lakes. Monitoring was carried out once every 4–5 years in 1990–2018, with analysis for major anions and cations, dissolved organic carbon (DOC), and heavy metals (Ni and Cu). Analysis of archive data on the weather allowed us to reliably identify trends toward a systematic temperature increase over the past 28 years. The population of the lakes under study was proven to generally show a decrease in the concentrations of anthropogenic sulfates and the strengthening of the acid-neutralizing capacity (ANC) of the waters during this period. The concentrations of both DOC and nutrients (Ptot and Ntot) in the lake waters were determined to increase. This phenomenon can be explained by the following two mechanisms: a decrease in the deposition of strong acids and climate warming. We suggest that the effects of multiple factors on the surface waters result in an irreversible evolution of the lakes; hence, the term recovery does not adequately reflect the processes occurring in this industrially well-developed part of the Arctic.