Acid Neutralizing Capacity Research Articles

Wet deposition of sulfur and nitrogen in the Jiuzhaigou World Heritage Site, China: Spatial variations, 2010–2022 trends, and implications for karst ecosystem conservation

Excessive sulfur and nitrogen deposition is a threat to natural ecosystems. This study investigated the spatio-temporal changes of wet sulfur and nitrogen deposition in Jiuzhaigou to understand the responses of wet deposition chemistry to local and national air pollutant emission changes and to assess relevant ecological risks. The results show that local emission sources (e.g., tourism, post-earthquake reconstruction, and vegetation damages) largely elevated the concentrations of SO42−, NO3−, NH4+, and Ca2+ at the non-background sites during 2021–2022; However, the gaps of annual sulfur and nitrogen wet deposition fluxes among the background, semi-background, and non-background sites were reduced by annual precipitation. The pH was also higher at the non-background sites due to stronger acid neutralization capacities from crustal dust there, and acid precipitation (pH < 5.6) was not detected at all the sites. During the 2010 to 2022 period, the wet deposition of SO42− and TIN (i.e. total inorganic nitrogen) and the equivalent ratio of SO42−: NO3− generally presented a declining trend at the background and semi-background sites, as a result of regional and national emission reductions. The TIN reduction from 2015 to 2016 to 2021–2022 at the background site was more from wet NH4+ deposition and the site's NO3− concentrations and fluxes were relatively stable. Compared to the critical loads (CLs) of sulfur and nitrogen for acidification and eutrophication, the annual wet and wet+dry deposition fluxes of sulfur and nitrogen were lower in almost the entire watershed, except for the CLmin of nitrogen for acidification in considerable areas. However, all the wet deposition samples were calcite-unsaturated and had annual TIN concentrations higher than the national environmental standard of total nitrogen for surface water. More field investigations are needed to better assess the ecological risks.

Leaching tests reveal fast aluminum fluoride release from ashfall accumulated in La Palma (Canary Islands, Spain) after the 2021 Tajogaite eruption

Leaching tests conducted on fresh ashfall samples taken soon after the onset of the 2021 Tajogaite eruption occurred at the Northwest flank of the Cumbre Vieja Volcanic Ridge in La Palma (Canary Islands) have revealed relevant geochemical trends which have important environmental significance and practical implications. The ashfall deposited on most of the island during the eruptive episode (9/19/2021–12/13/2021) contains, in addition to common constituents in volcanic tephra (e.g. volcanic glass, silicates like olivine, amphibole or pyroxene, magnetite, etc.) a significant amount of very fine-grained (diameter range of 10–500 μm) crystals of highly soluble salts like AlF3, NaCl, KCl or CaSO4. These salts likely crystallized at high temperature by interaction of acid volatile phases (e.g., HF, HCl, SO2) with volcanic glass and silicate minerals during the ascending flow of the eruptive plume, though some adsorption of marine aerosols on ash surfaces during the subsequent descending flow and transport to more distal areas could have also taken place. The dissolution of these salts in the leaching tests (conducted with ultrapure distilled water during 90 min) reveals a fast release of important amounts of F−, Cl− and SO42− as major anions, and Al3+, Na+, K+, Ca2+, Mg2+ and Si4+ as major cations, in addition to minor amounts of trace metals like Mn2+, Zn2+, Ba2+ or Sr2+. The release of F− and Al3+, both potentially toxic and travelling together as aluminum fluoride species (AlF3, AlF2+, AlF4−) is particularly noteworthy and represents a potential threat for the environment (including soils, surface waters or groundwater existing beneath the ashfall layers covering the island) as well as for food safety (e.g. banana plantations) and/or human health (exposure to F- or Al-contaminated water). On the other hand, the tephra does not represent an environmental hazard as regards to other toxic elements traditionally reported for ashfall released in other volcanic eruptions, such as As, Pb, Hg or Se, which were always close to or below the limit of quantification. Besides, the Tajogaite 2021 ashfall shows a significant acid-neutralizing capacity as a result of the partial dissolution of volcanic glass in the F-rich solutions. This study presents a discussion of geochemical and mineralogical controls on element mobility during ashfall/water interaction in the environment which may be worth considering in any future restoration or land management plans for the island.

A comparative study of the dissolution rate and Acid-Neutralizing capacity of Aceproxyvon with other marketed drugs

A comparative study of the dissolution rate and Acid-Neutralizing capacity of Aceproxyvon with other marketed drugs

Assessment of dissolution, disintegration time, and acid-neutralizing capacity of Butaproxyvon capsules (Paracetamol 325mg and diclofenac potassium 50mg)

This study was carried out to assess the in vitro dissolution of Butaproxyvon Capsule (Paracetamol 325mg and Diclofenac 50mg) by calculating the percentage mean drug dissolved and disintegration time, as well as acid neutralizing time. The capsules were tested using three different types of dissolution medium, including pH6.8 phosphate buffer, pH7.5 phosphate buffer, and pH4.5 acetate buffer. The disintegration apparatus was used to calculate the disintegration time, and the acid neutralizing capacity was determined by titrating the capsule content mix with hydrochloric acid with 0.5N sodium hydroxide. Acid neutralizing capacity was found 12.33 mEq/g. Disintegration time was found in the range of 4.40 to 10.00 minutes. % Mean Paracetamol release was found to be almost similar after 60 minutes in all media. % Mean Diclofenac Potassium release was to be found almost similar after 60 minutes by using pH 6.8 and pH 7.5 phosphate media. % Mean drug released for Diclofenac Potassium was found 13% in 4.5 Acetate media, and the released pattern was not uniform. This may be attributed to the low solubility of Diclofenac potassium in 4.5 Acetate media.

Biogenic acid resistance of calcium sulfoaluminate cement: Revelations from a field study

Biogenic acid attack of concrete is prevalent in sewers, posing a serious durability concern and financial burden. There are very limited number of field studies on durability of concrete under biogenic acid attack. Field study poses challenges with respect to the variation in climatic conditions and limited accessibility in sewers. Such a biogenic acid attack study in Indian conditions has not been performed. In this study, the biogenic acid resistance of Portland cement (PC) and calcium sulfoaluminate (CSA) cement-based binders under an in-situ sewer exposure is reported. The results show that the CSA-based binder used in this study outperformed PC in the biogenic acid resistance. The superior performance of CSA-based binder could be attributed to its acid neutralisation capacity offered by the aluminum hydroxide phase and bactericidal properties. For the first time, the bacteriostatic effect of CSA cement was demonstrated by analyzing the field exposed specimens.

Assessing acidity impacts in Nordic lakes and streams: Development of a macroinvertebrate-based multimetric index to quantify degradation and recovery

1)Emissions of acidifying compounds have decreased over several decades, nevertheless acidification impacts on aquatic ecosystems remains as a regionally important environmental driver resulting in biodiversity loss and impaired function in many lakes and streams.2)Many metrics based on macroinvertebrates are currently used to assess the biological impacts of acidification. However, few include measures of community composition, abundance, diversity, and the presence/absence of tolerant/sensitive taxa, and fewer still are calibrated simultaneously for both lentic and lotic waters and across large geographic regions.3)Data on water chemistry and benthic macroinvertebrates was extracted from a database compiled by representatives from Norway, Sweden and Finland. Using lake- and stream data on water chemistry and macroinvertebrates from Norway and Sweden, we developed a Nordic macroinvertebrate-based multimetric index (MMI) for acidity (NAMI) to assess impacts of and recovery from acidity using information on measures of community structure and traits.4)Lake and stream datasets were explored together and independently for correlation between measures of community structure and traits to acid neutralizing capacity (ANC), modified ANC regarding 1/3 of the organic acids as strong (ANCo1) and pH. Significantly correlated candidate metrics with highest correlations were chosen using forward stepwise linear regression models against ANC, ANCo1 and pH. Results showed that the combined lake and stream MMI had the highest correlation (r-squared) with ANCo1.5)Seven metrics were included in NAMI: one measure of composition (sum of the combined relative abundance of Gastropoda, Bivalvia and Crustacea), two measures of diversity (the number of Ephemeroptera taxa excluding leptophlebiids and the number of Bivalvia taxa), one effect trait (taxa with life cycle duration > 1 year), two response traits (taxa with resistance forms: eggs and plastron respiration) and one tolerance trait (preference > 5 pH < 5.5).6)The NAMI is a promising metric to standardize lake and stream macroinvertebrate assessments of acidity impacts and recovery across the Nordic countries, and to harmonize chemical and biological classifications of water quality, including progress towards achieving international objectives.

A comparative Study of Structural Properties and Antacid activity of some commercial samples of Shauktika bhasma

Backgroud: Shauktika Bhasma is a traditional ayurvedic medicine which is an excellent remedy for a number of stomach disorders, hyper acidity and ulcers. It is prepared from mother pearl by subjecting the powder of mother pearl to traditional ayurvedic processes. To get a worldwide recognition to such supreme ancient medicine, it is necessary to reinvestigate it on the basis of modern analytical techniques.In the present work a comparative study of some commercial samples of Shauktika bhasma is undertaken to understand the current status of this bhasma and to explore its acid neutralization capacity using back titration method. Materials and Methods: Samples from renowned pharmacies are collected and subjected to chemical and structural investigations using analytical techniques like XRD, IR and UV. Back titration method is applied to find acid neutralizing capacity of these bhasma samples. Conclusion:The study reveals that Shauktika bhasma is chemically calcite form of calcium carbonate. Antacid activity of the samples is reported for these samples using simple titration method which is useful to estimate number of moles neutralized for a quick comparison. The antacid activity of the samples is found to be inversely proportional to the crystallite size of the bhasma.

Biopharmaceutical properties of polyvalent bacteriophage capsules

Scientific relevance. Rational phage therapy is a highly effective way to combat bacterial infections, especially in conditions of steadily increasing antibiotic resistance. Most bacteriophage preparations are formulated as oral and topical solutions. However, oral administration of liquid phage preparations results in significant inactivation in the stomach. To shield active ingredients from the acidic environment, Sextaphag® Pyobacteriophage, polyvalent, has been formulated into capsules.Aim. This study evaluated the polyvalent bacteriophage preparation in capsules in terms of its potency and biopharmaceutical properties.Materials and methods. The study compared the polyvalent bacteriophage preparation formulated as capsules with the polyvalent bacteriophage preparation formulated as a solution. The potency was evaluated by the Appelmans method, and phage particles were quantified by the Gratia method. To evaluate the acid-neutralising capacity, the authors placed test samples of the bacteriophage preparation in 0.1 M hydrochloric acid and analysed their potency by the Appelmans method. Chinchilla rabbits were used to analyse anti-phage immune responses, and their antibody levels were measured using an enzyme immunoassay test system developed by the authors. The pharmacokinetic parameters were studied in outbred white mice after oral dosing.Results. The polyvalent bacteriophage preparation exhibited high lytic activity towards Escherichia coli, Klebsiella pneumoniae, Proteus mirabilis, Proteus vulgaris, Pseudomonas aegidinosa, Staphylococcus aureus, and Streptococcus pneumoniae, which accounted for a dilution factor of 10-6. Following oral administration of the polyvalent bacteriophage preparation in capsules to mice, the level of absorption was 3.1–3.7 times higher than that observed with the solution. Repeated oral administration of therapeutic doses did not induce anti-phage antibodies in rabbits. The stability study showed that the polyvalent bacteriophage preparation retained high lytic activity for 18 months.Conclusions. According to the study results, the polyvalent bacteriophage preparation in capsules exerts significant antibacterial activity against the studied microorganisms, has a high level of absorption, retains its lytic activity for a long time, and does not induce anti-phage antibodies after oral dosing, which confirms its safety and efficacy.

In vitro anti-inflammatory and anti-ulcer activities of aqueous extract of Emilia sonchifolia

Emilia sonchifolia, an annual herb belonging to the Asteraceae family, has long been recognized for its potential in treating cutaneous infections, inflammation, and wounds. This study aimed to assess the anti-inflammatory and anti-ulcer effects of Emilia sonchifolia using protein denaturation assay and Acid Neutralizing Capacity (ANC) methods. The acid neutralizing capacity method revealed that the extract significantly reduced acidity to 8.35 at a concentration of 1000 mg/ml, outperforming the standard Aluminum hydroxide + Magnesium hydroxide combination which achieved a value of 13.2 at 500 mg/ml. Furthermore, the results from the protein denaturation assay demonstrated a positive correlation between increased concentration and percentage inhibition of inflammation. The extract exhibited the highest inhibition percentage of 44.99 at a concentration of 200 µg/ml, and the standard diclofenac sodium achieved 84.120 at 100 µg/ml. These findings underscore the remarkable medicinal potential of aqueous extract of Emilia sonchifolia, particularly in its applications as an anti-inflammatory and anti-ulcer agent. In summary, the aqueous extract of Emilia sonchifolia demonstrated significant anti-inflammatory activity across various concentrations, when compared to the effectiveness of the standard drug diclofenac sodium. Additionally, the extract displayed anti-ulcer activity when compared to the standard Aluminum hydroxide + Magnesium hydroxide combination. Phytochemical analysis unveiled the presence of alkaloids, glycosides, saponins, flavonoids, terpenoids, phenolic compounds, steroids, and carbohydrates in Emilia sonchifolia. These phytochemical constituents likely contribute to the extract's protective properties against protein denaturation and its anti-ulcer effects.

PH-Dependent Leaching Characteristics of Steel Slag Mitigated with Water Treatment Residual

Abstract Steel slag (S) is a by-product of the steel industry with an annual global production of 280 MMT. A significant amount of the S is landfilled, causing economic loss and waste of valuable land space. S is deemed to have great potential as an aggregate because of its mechanical properties; however, the high swelling potential and alkalinity caused by large amounts of free calcium, hence the risk for metal leaching, limit its utilization; thus, a pretreatment process is needed. Amending the S with alum-based water treatment residual (WTR), which may form insoluble complexes with the free calcium, is expected to yield successful results, yet the leaching behavior and controlling mechanisms need to be determined. This study aims to evaluate the pH-dependent leaching characteristics of the pure and WTR-treated S as well as determine the dominant oxidation states of the trace metals and the controlling mechanisms. Acid neutralization capacity and pHstat leaching tests were performed on S–WTR mixtures with WTR contents varying from 0 to 100 % at a pH range of 2 to 14. The tests showed that leaching of all metals is significantly affected by pH and WTR content. Aluminum and copper exhibit an amphoteric behavior in which minimum leaching is observed at the neutral pH values and the metal concentrations are elevated at extreme acidic and alkaline pHs. On the other hand, cadmium, magnesium, calcium, and barium show a cationic leaching pattern. Furthermore, geochemical analyses were undertaken via Visual MINTEQ to determine predominant oxidation states of the metals with a redox potential and the speciation within the aqueous solutions, which showed that most of the releases from the elements were solubility controlled.

Comparative Characterization of Marketed Antacid Granules

Before inhibitors of the proton pump and antagonists of the H2 receptor, the mainstay of therapy was antacids for acid-peptic diseases. In this work different tests for characterization of different brands of antacid granules were carried out. This study set out to compare the quality of five antacid brands. Angle of repose, Bulk density, Tapped density, Carr's index, Hausner's ratio, Effervescent duration, Preliminary Antacid Test, Acid Neutralizing Capacity, Reheis Test, and Rosette Rice Test were used to compare the antacid granules. In the examination of several antacid granules available in the market, the values of bulk density, tapped density, angle of repose, carr's index, and hausner's ratio reveal that Brands A, B, and D have good flow property, Brand C has fair property, and Brand E has passable flow property. Brand A has a shorter effervescent time than other brands, while Brand D has a longer one. Because the antacid-acid (HCl) solution's pH for each brand is found to be greater than pH 3.5, all of the brands are considered to be antacids. The acid neutralizing capacity (ANC) test reveals that none of the antacid products meet the US FDA's requirement that they have an acid neutralizing capacity of at least 5 mEq. The Reheis test revealed that Brand B needed more time than other brands to neutralize, but Brand D needed less time. Brand A required less time than other brands to maintain the pH level between 3 and 5, while Brand D required more time, according to the Rosette rice test.

Lupeol: A Triterpenoid Isolated from the Stem Bark of Hymenocardia Acida (tul.) Exhibits a van der Waal Antagonism on the Alpha Subunit of Gastric H+K+Atpase - A Promising Antiulcer Principle.

Hymenocardia acida (HA) is one of the numerous medicinal plants in Nigeria with ethnomedicinal history of usage in the treatment of ulcer. The study aimed at isolating antiulcer principle(s) from the stem bark of HA as well as the mechanism of action determination. Antiulcer screenings of the crude extract, aqueous fraction, and bulked VLC fractions were performed using in vivo and in vitro models. Docking was carried out by using PyRx. Crude extract (HA; 1 mg/mL) and the aqueous fraction of H. acida (HAA; 1 mg/mL) showed an acid neutralizing capacity (MEq) of 0.3948 and 0.4035, respectively which is significantly different from 0.431 MEq showed by negative control (distilled water) at p<0.05. BVLC 3 (1 mg/mL) showed a significant value of 0.4049 MEq. However, HA showed a dose-dependent decrease in activity across doses examined, with 100 mg/kg showing an ulcer index of 10.00±2.89 (61.50%) and cimetidine (positive control; 100 mg/kg), also showed the highest ulcer index of 3.67±0.88 (85.9%), which is significantly different from ulcer index of 26.00±6.35 (0.00%) p<0.05 observed in the negative control (5% dimethylsulphoxide). The highest ulcer index of 8.00±1.32 (65.10%) was noted in BVLC 3. Bioactive BVLC 3, resulted in an isolated compound (BF3B2A). The compound was suggested to be lupeol, with a docking score of -7.7. It showed a van der Waal interaction with some key amino acid residues in the vonoprazan binding site. The experimental studies justify the ethnomedicinal claim of usage among locals.

The recovery of crustacean zooplankton from acidification depends on lake type.

Acidification has harmed freshwater ecosystems in Northern Europe since the early 1900s. Stricter regulations aimed at decreasing acidic emissions have improved surface-water chemistry since the late 1980s but the recovery of biotic communities has not been consistent. Generally, the recovery of flora and fauna has been documented only for a few lakes or regions and large-scale assessments of long-term dynamics of biotic communities due to improved water quality are still lacking. This study investigates a large biomonitoring dataset of pelagic and littoral crustacean zooplankton (Cladocera and Copepoda) from 142 acid-sensitive lakes in Norway spanning 24 years (1997-2020). The aims were to assess the changes in zooplankton communities through time, compare patterns of changes across lake types (defined based on calcium and humic content), and identify correlations between abiotic and biological variables. Our results indicate chemical and biological recovery after acidification, as shown by a general increase in pH, acid neutralizing capacity, changes in community composition and increases in the total number of species, number of acid-sensitive species and functional richness through time. However, the zooplankton responses differ across lake types. This indicates that the concentration of calcium (or alkalinity) and total organic carbon (or humic substances) are important factors for the recovery. Therefore, assessment methods and management tools should be adapted to the diverse lake types. Long-term monitoring of freshwater ecosystems is needed to fully comprehend the recovery dynamics of biotic communities from acidification.

Uniformly valid inference based on the Lasso in linear mixed models

Linear mixed models (LMMs) are suitable for clustered data and are common in biometrics, medicine, survey statistics, and many other fields. In those applications, it is essential to carry out valid inference after selecting a subset of the available variables. We construct confidence sets for the fixed effects in Gaussian LMMs that are based on Lasso-type estimators. Aside from providing confidence regions, this also allows for quantification of the joint uncertainty of both variable selection and parameter estimation in the procedure. To show that the resulting confidence sets for the fixed effects are uniformly valid over the parameter spaces of both the regression coefficients and the covariance parameters, we also prove the novel result on uniform Cramér consistency of the restricted maximum likelihood (REML) estimators of the covariance parameters. The superiority of the constructed confidence sets to naïve post-selection procedures is validated in simulations and illustrated with a study of the acid-neutralization capacity of lakes in the United States.

FORMULATION AND EVALUATION OF POLYHERBAL ANTACID TABLET

With ever increasing issue of hyperactivity both idiopathic and drug induced, the available allopathic antacids on chronic use are source of many side effects which can cause great discomfort to the patient. Hence, ayurveda approved herbs with antacid property used daily in one way or the other by the population can prove to be the best alternative to the issue of acidity. Hence, we developed a Polyherbal antacid tablet for the concerned issue along with expectation of great safety profile. KEYWORD: - Polyherbal antacid, Hyperacidity, acid neutralizing capacity

Acidity of Soil and Water Decreases in Acid-Sensitive Forests of Tropical China.

Acid deposition in China has been declining since the 2000s. While this may help mitigate acidification in forest soils and water, little is known about the recovery of soils and water from previous severe acidification in tropical China. Here, we assessed the chemistry of mineral soils, water, and acid gases (SO2 and NOx) from three successional forest types in tropical China from 2000 to 2022. Our results showed that soil pH increased synchronously from 3.9 (2000-2015) to 4.2 (2016-2022) across all three forest types, with exchangeable acid initially decreasing and thereafter stabilizing. Surface and ground water pH also gradually increased throughout the monitoring period. Soil pH recovery was stronger in the primary than in the planted forest. However, soil pH recovery lagged behind the increase in rainfall pH by approximately a decade. The recovery of soil pH was likely related to the positive effects of the dissolution of Al/Fe-hydroxysulfate mineral and subsequent sulfur desorption on soil acid-neutralizing capacity, increased soil organic matter, and climate warming, but was likely moderated by increased exchangeable aluminum and potentially proton-producing hydroxysulfate mineral dissolution that caused the lagged soil pH recovery. Surface and ground water pH recovery was attributed to increased water acid-neutralizing capacity. Our study reports the potential for the recovery of acidified soil and water following decreased acid deposition and provides new insights into the functional recovery of acid-sensitive forests.

Exploring the acid neutralizing effect in rainwater collected at a tropical urban area: Central Valley, Costa Rica

We report on the chemical and the carbon isotopic composition of dissolved inorganic carbon (DIC) of rainwater collected between May and October 2020 in the Central Valley, Costa Rica. Precipitation samples were collected daily (N = 55) and analyzed for major ions, DIC, and δ13CDIC. Significant correlation (p < 0.05) between main acidic (SO42− and NO3−) and major alkaline (Ca2+ and NH4+) species confirmed a very effective acid neutralization effect in rainwater (average pH: 5.90 ± 0.74). Significant temporal variations (p < 0.05) of δ13CDIC indicated the contribution of carbonate salts in rainwater from May to October but also CO2 dissolution at the beginning of the wet season (May), probably due to increased CO2 emissions from soil degassing. Temporal changes of Ca2+ neutralization factors followed the observed changes in δ13CDIC, which confirmed the high buffer capacity of precipitation in our study. HYSPLIT analysis also revealed long-range contributions of pedogenetic carbonates (e.g., Saharan dust) responsible for the acid neutralization capacity of rainwater (e.g., from July to September). Principal component analysis showed that four main factors explain 65% of the variance are: i) acid neutralization processes (Ca2+ neutralization factor), ii) marine salts (Cl−, Na+), iii) fossil fuels (SO42−, NO3−), and iv) agriculture/fertilizers (NO3−, NH4+, K+). Our study demonstrated that a combined approach of chemical, isotope, and statistical analysis techniques can help unravel the mechanism of acid neutralization of rainwater in tropical urban areas. This information has strong implications for future studies related with the impact of acid deposition on ecosystem functioning, water quality, and infrastructure degradation.

Utilization of municipal solid waste incineration fly ash as construction materials based on geopolymerization

Incineration has been widely used to dispose municipal solid wastes (MSWs) with heat recovery. The generation of fly ash (FA, around 3∼5 wt% of the fed amount) that is normally defined as hazardous wastes remains a serious problem. It is ideal to work out a way to reutilize FA for valuable use instead of landfilling. As a novel utilization technology for municipal solid waste incineration (MSWI) fly ash, geopolymerization can produce geopolymer as construction materials with the advantages of low energy consumption, low pollution and high utilization rate. In this paper, metakaolin (MK) and washed fly ash (WFA) were used to prepare MSWI fly ash-based geopolymer (FAG) with alkali activator. Besides, the strength, heavy metals immobilization and acid resistance of FAG were in detail studied. Under the proper formulation, all the prepared FAGs exhibited strength higher than MU15 level (≥15 MPa) and the maximized one reached MU30 (≥30 MPa). Heavy metals including Cr, Mn, Cu, As, Pb, Zn and Cd had a immobilization rate of more than 92%, and others like As, Pb and Zn were nearly fully immobilized. As for the simulated testing for acid rain scenario, FAG could still fix up the heavy metals well indicating a controllable risk for the environment, which could be ascribed be its high acid neutralization capacity. In a word, this work reports a feasible method for treatment and resource reutilization of MSWI fly ash.

Use of limekiln dust in the stabilization of heavy metals in Ghanaian gold oxide ore mine tailings.

Remedial action for heavy metal-contaminated soils is imperative for preventing heavy metal leachability and minimizing environmental risks. This study evaluated the use of limekiln dust (LKD) as a heavy metal stabilization agent for Ghanaian gold mine oxide ore tailing material. Heavy metal-laden tailing material (Fe, Ni, Cu, Cd, and Hg) was collected from a tailing dam site in Ghana. Stabilization was done using acid neutralization capacity (ANC) and citric acid test (CAT) while all chemical characterization was done using X-ray fluorescence (XRF) spectroscopy. Various physicochemical parameters including pH, EC, and temperature were also measured. The contaminated soils were amended with LKD in doses of 5, 10, 15, and 20 wt.%. The results revealed that the contaminated soils had concentrations of heavy metals above FAO/WHO stipulated limits of 350, 35, 36, 0.8, and 0.3mg/kg for Fe, Ni, Cu, Cd, and Hg, respectively. After 28days of curing, 20 wt.% of LKD was found to be appropriate for the remediation of the mine tailings of all the heavy metals studied except Cd. Ten percent of the LKD was noticed to be enough in remedying soil contaminated with Cd since the Cd's concentration reduced from 9.1 to 0.0mg/kg with a stabilizing efficiency of 100% and a leaching factor of 0.0. Therefore, remediation of contaminated soils of Fe, Cu, Ni, Cd, and Hg with LKD is safe and environmentally friendly.

Assessing impacts of sulfur deposition on aquatic ecosystems: A decision support system for the Southern Appalachians

AbstractWith climate change and ongoing impacts from human development and resource extraction, US federal land management agencies are acutely concerned with managing for healthy aquatic ecosystems in the Southern Appalachian Mountain (SAM) Region. Here, we describe development of a spatial decision support application to assess the biological and ecological impacts of atmospheric S and N deposition on aquatic ecosystems of the region. We first summarize foundational published work to predict continuous maps of surface water acid neutralizing capacity (ANC) and soil base cation weathering (BCw). We use the predicted ANC and BCw maps to estimate steady‐state critical loads (CLs) of atmospheric S and N deposition. We included estimated CLs of atmospheric N to get a complete picture of CLs and potential exceedances. We then present a logic‐based decision support model for assessing effects of S and N deposition based on statistically modeled stream ANC and CL exceedance. The model is easily modified for continuous monitoring of CL exceedance patterns as new S and N deposition and ANC data become available. We present mapped model results for the SAM study area and an important subset of the region, the Great Smoky Mountains National Park. ANC modeling results revealed that predicted acid sensitivity was spatially variable, with areas of relatively low stream ANC (&lt;50 μeq · L−1) and soil BCw (&lt;50 meq · m−2 · year−1) predominantly found in certain critical areas. Within the Great Smoky Mountains National Park, evidence for S CL exceedance based on an ANC criterion of 50 μeq · L−1 was strong at locations where ambient S deposition was at least two times the CL. We also predicted likely impacts of CL exceedances on aquatic insect species richness and native fish abundance. Responses for insect species richness and fish impact showed variability similar to CL exceedance, with increasing impact positively correlated with elevation. Finally, we discuss ways that the decision support system can be used to prioritize management across the region.