Acid Neutralizing Capacity Research Articles

High elevation watersheds in the southern Appalachians: Indicators of sensitivity to acidic deposition and the potential for restoration through liming

Southern Appalachian high elevation watersheds have deep rocky soils with high organic matter content, different vegetation communities, and receive greater inputs of acidic deposition compared to low elevation sites within the region. Since the implementation of the Clean Air Act Amendment in the 1990s, concentrations of acidic anions in rainfall have declined. However, some high elevation streams continue to show signs of chronic to episodic acidity, where acid neutralizing capacity (ANC) ranges from 0 to 20μeqL−1. We studied three 3rd order watersheds (North River in Cherokee National Forest, Santeetlah Creek in Nantahala National Forest, and North Fork of the French Broad in Pisgah National Forest) and selected four to six 1st order catchments within each watershed to represent a gradient in elevation (849–1526m) and a range in acidic stream ANC values (11–50μeqL−1). Our objectives were to (1) identify biotic, physical and chemical catchment parameters that could be used as indices of stream ANC, pH and Ca:Al molar ratios and (2) estimate the lime required to restore catchments from the effects of excess acidity and increase base cation availability. We quantified each catchment’s biotic, physical, and chemical characteristics and collected stream, O-horizon, and mineral soil samples for chemical analysis seasonally for one year. Using repeated measures analysis, we examined variability in stream chemistry and catchment characteristics; we used a nested split-plot design to identify catchment characteristics that were correlated with stream chemistry. Watersheds differed significantly and the catchments sampled provided a wide range of stream chemical, biotic, physical and chemical characteristics. Variability in stream ANC, pH, and Ca:Al molar ratio were significantly correlated with catchment vegetation characteristics (basal area, tree height, and tree diameter) as well as O-horizon nitrogen and aluminum concentrations. Total soil carbon and calcium (an indicator of parent material), were significant covariates for stream ANC, pH and Ca:Al molar ratios. Lime requirement estimates did not differ among watersheds but this data will help select catchments for future restoration and lime application studies. Not surprisingly, this work found many vegetation and chemical characteristics that were useful indicators of stream acidity. However, some expected relationships such as concentrations of mineral soil extractable Ca and SO4 were not significant. This suggests that an extensive test of these indicators across the southern Appalachians will be required to identify high elevation forested catchments that would benefit from restoration activities.

Recovery of young brown trout (Salmo trutta) in acidified streams: What are the critical values for acid-neutralizing capacity?

The recovery of young allopatric brown trout (Salmo trutta) grouped into YoY (age 0+) and older parr (age ≥1+) fish, was studied in acid-sensitive streams in a Norwegian watershed during a 24-year-period (1987–2010). Their abundance was assessed by electrofishing. Most sites typically had 5.0–5.5 in pH, 0.4–0.7 mg L−1 Ca, 10–20 μg L−1 inorganic toxic aluminum (Ali) and acid-neutralizing capacity adjusted for organic acids (ANCOAA) of - 15 to +25 μeq L−1. Densities of both YoY and older parr increased significantly during the study period. Water quality also improved in recent years with respect to pH (5.8–6.0), Ali (5–15 μg L−1) and ANCOAA (10–20 μeq L−1). However, some negative trends in both fish density and water chemistry were found during both the first (1987–1993) and last years (2004–2008) of the study. Initially, YoY densities remained at about 16–20 specimens 100 m−2 (1987–1990), declined to 10–15 specimens 100 m−2 in the early/mid 1990s, and rosed to 30–50 specimens 100 m−2 in recent years (1997–2010). Their densities correlated significantly with ANCOAA, and at least three stages in the recovery process were recognised: (i) Low density with 10–20 specimens 100 m−2 at −18 to −5 μeq L−1, (ii) medium and unstable density with 20–30 specimens 100 m−2 at −5 to 10 μeq L−1, and (iii) increasing density to 40–50 specimens 100 m−2 at 10–25 μeq L−1. The decline in brown trout density in the early-mid 1990s coincided with high sea salt depositions, which caused increased acidification. Component 1 in a PCA explained 51% of the variation in fish densities, including conductivity, Mg, Ca, Na, alkalinity and TOC. Component 2 explained an additional 31% of the variation, including pH, Ali and ANCOAA. Multiple regression analysis coefficients showed that the two components explained 41% of the variance in total fish density. Young brown trout suffered a high mortality during the initial phase of the study in spite of relative low levels of Ali. This is probabaly because the study streams have very diluted water. The densities of young brown trout have levelled off in recent years, indicating a development towards reaching carrying capacity and hence full recovery. However, still some annual fluctuations in density are recorded, which may be related to an unstable water chemistry.

Acid rain mitigation experiment shifts a forested watershed from a net sink to a net source of nitrogen

Decades of acid rain have acidified forest soils and freshwaters throughout montane forests of the northeastern United States; the resulting loss of soil base cations is hypothesized to be responsible for limiting rates of forest growth throughout the region. In 1999, an experiment was conducted that reversed the long-term trend of soil base cation depletion and tested the hypothesis that calcium limits forest growth in acidified soils. Researchers added 1,189 kg Ca(2+) ha(-1) as the pelletized mineral wollastonite (CaSiO3) to a 12-ha forested watershed within the Hubbard Brook Experimental Forest in the White Mountains of New Hampshire. Significant increases in the pH and acid-neutralizing capacity of soils and streamwater resulted, and the predicted increase in forest growth occurred. An unanticipated consequence of this acidification mitigation experiment began to emerge a decade later, with marked increases in dissolved inorganic nitrogen (DIN) exports in streamwater from the treated watershed. By 2013, 30-times greater DIN was exported from this base-treated watershed than from adjacent reference watersheds, and DIN exports resulting from this experiment match or exceed earlier reports of inorganic N losses after severe ice-storm damage within the study watershed. The discovery that CaSiO3 enrichment can convert a watershed from a sink to a source of N suggests that numerous potential mechanisms drive watershed N dynamics and provides new insights into the influence of acid deposition mitigation strategies for both carbon cycling and watershed N export.

Response of fish assemblages to declining acidic deposition in Adirondack Mountain lakes, 1984–2012

Adverse effects of acidic deposition on the chemistry and fish communities were evident in Adirondack Mountain lakes during the 1980s and 1990s. Fish assemblages and water chemistry in 43 Adirondack Long-Term Monitoring (ALTM) lakes were sampled by the Adirondack Lakes Survey Corporation and the New York State Department of Environmental Conservation during three periods (1984–87, 1994–2005, and 2008–12) to document regional impacts and potential biological recovery associated with the 1990 amendments to the 1963 Clean Air Act (CAA). We assessed standardized data from 43 lakes sampled during the three periods to quantify the response of fish-community richness, total fish abundance, and brook trout (Salvelinus fontinalis) abundance to declining acidity that resulted from changes in U.S. air-quality management between 1984 and 2012. During the 28-year period, mean acid neutralizing capacity (ANC) increased significantly from 3 to 30 μeq/L and mean inorganic monomeric Al concentrations decreased significantly from 2.22 to 0.66 μmol/L, yet mean species richness, all species or total catch per net night (CPNN), and brook trout CPNN did not change significantly in the 43 lakes. Regression analyses indicate that fishery metrics were not directly related to the degree of chemical recovery and that brook trout CPNN may actually have declined with increasing ANC. While the richness of fish communities increased with increasing ANC as anticipated in several Adirondack lakes, observed improvements in water quality associated with the CAA have generally failed to produce detectable shifts in fish assemblages within a large number of ALTM lakes. Additional time may simply be needed for biological recovery to progress, or else more proactive efforts may be necessary to restore natural fish assemblages in Adirondack lakes in which water chemistry is steadily recovering from acidification.

Changes in heavy metal extractability from contaminated soils remediated with organic waste or biochar

The effect of the addition of organic waste or biochar on the extractability of heavy metals (Cd, Cu, Ni, Pb and Zn) was assessed in five heavy metal-contaminated soils. The amendments studied were: municipal organic waste compost (MOW), green waste (GW), biochar derived from tree bark (BF) and biochar derived from vine shoots (BS). The amendments were added to the soil at 10% dose. A pHstat leaching test was applied to the soils and soil+amendment mixtures to assess the effects of the amendments on the extractable metal concentration at the initial pH and in the 2–12pH range. MOW increased the DOC content in the mixtures for most soils, whereas the rest of amendments only increased the DOC content for the soil with the lowest DOC value. Moreover, in the mixtures obtained from soils with a low buffering capacity, the amendments increased pH (up to 3units) and the acid neutralization capacity, thus decreasing the extractability of heavy metals at the initial pH of the mixtures. In a few cases, the amendments further decreased the concentrations of extractable metal due to an increase in the sorption capacity of the mixture, even though the soil had high initial pH and ANC values. MOW and GW generally led to larger decreases in metal extractability in the resulting mixtures than biochar, due to their higher sorption and acid neutralization capacities.

Long-term predictions of ecosystem acidification and recovery

This paper considers the long-term (500year) consequences of continued acid deposition, using a small forested catchment in S. England as an example. The MAGIC acidification model was calibrated to the catchment using data for the year 2000, and run backwards in time for 200years, and forwards for 500. Validation data for model predictions were provided by various stream and soil measurements made between 1977 and 2013. The model hindcast suggests that pre-industrial stream conditions were very different from those measured in 2000. Acid Neutralising Capacity (ANC) was +150μeqL−1 and pH7.1: there was little nitrate (NO3). By the year 2000, acid deposition had reduced the pH to 4.2 and ANC to c. −100μeqL−1, and NO3 was increasing in the stream. The future state of the catchment was modelled using actual deposition reductions up to 2013, and then based on current emission reduction commitments. This leads to substantial recovery, to pH6.1, ANC +43μeqL−1, though it takes c. 250years. Then, however, steady acidification resumes, due to continued N accumulation in the catchment and leaching of NO3. Soil data collected using identical methods in 1978 and 2013 show that MAGIC correctly predicts the direction of change, but the observed data show more extreme changes – reasons for this are discussed. Three cycles of forest growth were modelled – this reduces NO3 output substantially during the active growth phase, and increases stream pH and ANC, but acidifies the soil which continues to accumulate nitrogen. The assumptions behind these results are discussed, and it is concluded that unmanaged ecosystems will not return to a pre-industrial state in the foreseeable future.

Responses of soil buffering capacity to acid treatment in three typical subtropical forests

Elevated anthropogenic acid deposition can significantly affect forest ecosystem functioning by changing soil pH, nutrient balance, and chemical leaching and so on. These effects generally differ among different forests, and the dominant mechanisms for those observed responses often vary, depending on climate, soil conditions and vegetation types. Using soil monoliths (0–40cm) from pine forest (pioneer), coniferous and broadleaved mixed forest (transitional) and broadleaved forest (mature) in southern China, we conducted a leaching experiment with acid treatments at different pH levels (control: pH≈4.5; pH=3.5; pH=2.5). We found that pH3.5 treatment significantly reduced dissolved organic carbon (DOC) concentrations in leachate from the pioneer forest soil. pH2.5 treatment significantly increased concentrations of NO3−, SO42−, Ca2+, Mg2+, Al3+, Fe3+ and DOC in leachate from the pioneer forest soil, and also concentrations of NO3−, SO42−, Mg2+, Al3+, Fe3+ and DOC in leachate from the transitional forest soil. All acid treatments had no significant effects on concentrations of these chemicals in leachate from the mature forest soil. The responses can be explained by the changes in soil pH, acid neutralizing capacity (ANC) and concentrations of Al and Fe. Our results showed that acid buffering capacity of the pioneer or transitional forest soil was lower than that of the mature forest soil. Therefore preserving mature forests in southern China is important for reducing the adverse impacts of high acid deposition on stream water quality at present and into the future.

A modified approach for estimating the aquatic critical load of acid deposition in northern Saskatchewan, Canada

Acid-sensitive ecosystems are found in northern Saskatchewan, which lies downwind of major sulphur (S) and nitrogen (N) emissions sources associated with the oil sands extraction industry. In order to protect these ecosystems against acidification, tolerance to acid deposition must be quantified. The suitability of the central empirical relationship used in the Steady-State Water Chemistry (SSWC) model to predict historical sulphate (SO4) concentrations was investigated, and an alternate approach for determining aquatic critical loads of acidity (CL(A)) was employed for the study lakes (n = 260). Critical loads of acidity were often low, with median values of 12–16 mmolc m−2 yr−1, with the lower value reflecting a region-specific limit for acid-neutralizing capacity identified in this study. Uncertain levels of atmospheric deposition in the region, however, are problematic for characterizing acidification risk. Accurate S and chloride (Cl) deposition are needed to identify catchment sources (and sinks) of these elements in the new approach for CL(A) calculation. Likewise, accurate depiction of atmospheric deposition levels can prove useful for evaluation of lake runoff estimates on which estimates of CL(A) are contingent. While CL(A) are low and exceedance may occur according to projected increases in S deposition in the near-term, S retention appears to be an important feature in many catchments and risk of acidification may be overstated should long-term S retention be occurring in peatlands.

Biomimetic Acid Soil Amelioration using Indigenous Soil Isolates in Comparison to other Potential Microorganism

ABSTRACTIn the present study, four different soil isolates were screened and evaluated for their acid neutralization capacity in liquid culture and soil column tests with either artificial soil or real acid soil. Miniaturized artificial soil column tests using Aspergillus fumigatus, Aureobasidium pullulans, and Myxococcus xanthus were also included. In the liquid-phase experiment, two isolates (designated ‘A’ and ‘B’) effectively increased the medium pH from 4 to 6.74 and 6.53, respectively, during the 6 d, and the ammonium-nitrogen (NH4+-N) concentration increased from 400 ppm to 1000 ppm (isolate A). The isolates A and B were identified as Enterococcus hirae and Clostridium sp. in 16S ribosomal ribonucleic acid (rRNA) analysis. Artificial soil pH increased more quickly with soil isolates than in comparison to A. fumigatus or A. pullulans. In real acid soil pH increased from 4.2 to about pH 6.5 within 4 d. This suggests that biomimetic approaches could be valuable for acid soil amelioration.

Revegetation of extremely acid mine soils based on aided phytostabilization: A case study from southern China

Acidification is a major constraint for revegetation of sulphidic metal-contaminated soils, as exemplified by the limited literature reporting the successful phytostabilization of mine soils associated with pH<3 and high acidification potential. In this study, a combination of ameliorants (lime and chicken manure) and five acid-tolerant plant species has been employed in order to establish a self-sustaining vegetation cover on an extremely acid (pH<3) polymetallic pyritic mine waste heap in southern China exhibiting high acidification potential. The results from the first two-year data showed that the addition of the amendments and the establishment of a plant cover were effective in preventing soil acidification. Net acid-generating potential of the mine soil decreased steadily, whilst pH and acid neutralization capacity increased over time. All the five acid-tolerant plants colonized successfully in the acidic metal-contaminated soil and developed a good vegetation cover within six months, and subsequent vegetation development enhanced organic matter accumulation and nutrient element status in the mine soil. The two-year remediation program performed on this extremely acid metalliferous soil indicated that aided phytostabilization can be a practical and effective restoration strategy for such extremely acid mine soils.

Acid mine drainage analysis for the Reddale Coal Mine, Reefton, New Zealand

ABSTRACTThe Reddale Coal Mine is located within the Brunner Coal Measures, which are often assumed to be potentially acid-forming rocks that will release acidity when disturbed by mining. The pre-mining assessment of the site acid mine drainage (AMD) potential assumed overburden acid-neutralising capacity was negligible, similar to Brunner Coal Measures in other areas, and that AMD would occur almost immediately. Column trials using poorly stored and partially oxidised drill core indicated potentially acid-forming (PAF) overburden readily produced acidity with no lag period. Based on the pre-mining assessment, a Ca(OH)2 dosing plant was constructed for AMD management. Once mining commenced, tiphead samples collected during construction of the Ferndale engineered landform showed that the net acid-producing potential of the potentially acid-forming overburden was overestimated by about one-third when acid-neutralising capacity and non-sulphide forms of sulphur were accounted for. When coupled with material properties which resulted in good compaction of waste rock, construction of the engineered landform in 4 m lifts to minimise convective oxygen flux and aglime (<2.5 mm CaCO3) amendments to each lift, acidity loads from the Ferndale engineered landform were negligible. Compliance monitoring downstream of the mine site at Red4 shows that, to date, site discharge pH has remained circum-neutral. Pre-mining AMD management decisions, primarily construction of a Ca(OH)2 dosing plant that was never commissioned, therefore proved overly conservative. The timing and expense of AMD management has the potential to influence project feasibility and needs to be well understood.

Evaluation of Hemidesmus indicus root as an antacid by In vitro

Medicinal plants are being widely used, either as single drug or in combination in health care delivery system. Indian Sarsaparilla, Hemidesmus indicus (Family: Asclepiadaceae) is a commonly known Indian Medicinal Plant, which is widely recognized in traditional systems of Medicine. It contains various phytoconstituents belonging to the category glycosides, flavonoids, tannins, sterols and volatile oils. It has been reported as useful in biliousness, blood diseases, dysentery, diarrhea, respiratory disorders, skin diseases, syphilis, fever, leprosy, leucoderma, leucorrhoea, itching, bronchitis, asthma, eye diseases, epileptic fits in children, kidney and urinary disorders, loss of appetite, burning sensation, dyspepsia, nutritional disorders, ulcer and rheumatism. Several studies are being carried towards its activities like analgesic, anti-inflammatory, antiulcer, hepatoprotective, antioxidant and helicobactericidal properties. In our study we have evaluated antacid activity of sariva (Anantmool) by using In-Vitro method, i.e. ANC (Acid Neutralizing Capacity). This evaluation was done by comparing the ANC of sariva macerated &amp; powdered drug with water as blank &amp; standard drug i.e. NaHCO3. Based on this In-Vitro experiment, we can conclude that, the macerated &amp; powdered drug of sariva (Anantmool) evaluated in this study, varied in potency as measured in terms of their ANC. These results having ** i.e. P &lt; 0.01 &amp; Passed the normality test. However, the present study being in-vitro, the effects of antacid may vary In-Vitro; individual variations also contribute to the ultimate effectiveness of as antacid.

A Water Framework Directive-compatible metric for assessing acidification in UK and Irish rivers using diatoms

Freshwater acidification continues to be a major problem affecting large areas of Europe, and while there is evidence for chemical recovery, similar evidence for biological recovery of freshwaters is sparse. The need for a methodology to identify waterbodies impacted acidification and to assess the extent of biological recovery is relevant to the EU Water Framework Directive, which requires methods to quantify differences in biology between impacted and unimpacted or reference sites. This study presents a new WFD-compliant metric based on diatoms (Diatom Acidification Metric: DAM) for assessing the acidification status of rivers. A database of 558 benthic diatom samples and associated water chemistry data was assembled. Diatom taxa were assigned to one of 5 indicator classes on the basis of their pH optimum, assessed using Gaussian logistic regression, and these indicator values used to calculate a DAM score for each site using weighted averaging. Reference sites were selected on the basis of their acid neutralising capacity (ANC) and calcium concentration, and a regression model developed to predict expected DAM for each site using pH and total organic carbon (TOC) concentration. Site-specific DAM scores were used to calculate ecological quality ratios ranging from ≥1, where the diatom assemblage showed no impact, to (theoretically) 0, when the diatom assemblage was indicative of major anthropogenic activities. The boundary between ‘high’ and ‘good’ status was defined as the 25th percentile of Ecological Quality Ratios (EQRs) of all reference sites. The boundary between ‘good’ and ‘moderate’ status was set at the point at which nutrient-sensitive and nutrient-tolerant taxa were present in equal relative abundance. The methodology was evaluated using long-term data from 11 sites from the UK Uplands Waters Monitoring Network and is shown to perform well in discriminating naturally acid from acidified sites.

Geochemical characterization of engineered coal-combustion byproducts (CCBs): Occurrence and mobility of trace elements, implications for interactions with acidic and ambient groundwater

Fixed scrubber sludge (FSS), is a coal-combustion byproduct composed of flue gas desulphurization sludge, fly ash, and quick lime. FSS has potential usages as structural fill and capping materials in mine land reclamation because of its low permeability and acid-neutralization capacity. Sediment cores extracted from an abandoned mine land reclamation site where FSS was used as a hydrologic barrier to groundwater recharge were analyzed in an effort to quantify the chemical phases (both primary and secondary) that constitute the FSS, and to evaluate any evidence of weathering that has occurred during the 18years since emplacement. The primary solid phase is amorphous spheroids. Four different types were identified and their quantitative compositions were obtained, with SiO2, Al2O3, and FeO being the primary components. Of special concern was the occurrence and mobility of trace elements within the solid phases. Sequential extractions using different chemical reagents were conducted to analyze the concentrations of As, B, Ba, Cd, Cr, Cu, Ni, Pb, and Zn in different fractions as indications of mobility. The highest concentration of the trace elements was contained in the residual fraction, which is consistent with the amorphous spheroids being very resistant to chemical weathering. The results also suggest that the mobility of the trace elements decrease in the following order: B, Cu>Cd, Zn, Pb, Cr>Ba>Ni>As. Comparison of samples collected from the weathered edges and unweathered portions of the FSS layer reveal that a more aggressive weathering environment exists at the upper boundary of the FSS, where it is in contact with oxygenated soil water. The quantitative chemical compositions, distribution of trace elements, as well as evidence of how trace elements are released provide background data for the development a reactive transport model to simulate long-term effects of placing FSS in the natural environment; and particularly in areas that are being subjected to abandoned mine land reclamation.

Долговременная динамика гидрохимических показателей низкоминерализованного субарктического озера при снижении кислотной нагрузки

The results of long-term studies (1990–2013) of dynamics of the main hydrochemical indices of the subarctic Shuonijavr Lake located in the zone of airborne pollution from a metallurgical plant have been considered. The following facts have been revealed: significant increase of alkalinity and acid neutralizing capacity (ANC) of the lake water; reduction in the range of seasonal fluctuations of ph and alkalinity; reduction of 2 4 SO − in the lake water during the observation period as a result of reducing the acid load due to the decrease of SO2 emission. Despite the stabilization of the lake water ANC the pollution indicators in six elements of polluters foreground for the region remain high values. Ключевые слова: Субарктика, озеро, закисление, кислотонейтрализующая способность, тяжелые металлы, формы металлов, восстановление.

Leaching Behavior of Heavy Metals from Cement Pastes Using a Modified Toxicity Characteristic Leaching Procedure (TCLP).

As the standard toxicity characteristic leaching procedure (TCLP) can not exhaust the acid neutralizing capacity of the cement rotary kiln co-processing solid wastes products which is particularly important for the assessment of the leaching concentrations of heavy metals. A modified TCLP was proposed. The extent of leaching of heavy metals is low using the TCLP and the leaching performance of the different metals can not be differentiated. Using the modified TCLP, however, Zn leaching was negligible during the first 180h and then sharply increased (2.86±0.18 to 3.54±0.26mg/L) as the acidity increased (pH<6.0). Thus, Zn leaching is enhanced using the modified TCLP. While Pb leached readily during the first 126h and then leachate concentrations decreased to below the analytical detection limit. To conclude, this modified TCLP is a more suitable method for these cement rotary kiln co-processing products.

The leaching characteristics and changes in the leached layer of antimony-bearing ores from China

China has the most abundant antimony (Sb) resources of any country in the world. Large quantities of Sb have been released from mining and smelting processes, causing serious Sb contamination in the mine or nearby areas. To understand the leaching characteristics of hazardous Sb, As, Pb and Cr from antimony minerals, 12 samples of antimony-bearing ores from eight large mines from China distributed in Hunan, Yunnan, Guizhou and Guangxi provinces were studied. The main compositions of these minerals are Sb2S3, SiO2 or CaCO3. The pH changes during the leaching indicated that some minerals themselves are alkaline, providing sufficient acid neutralizing capacity during leaching. However, some alkaline minerals release much more Sb, As, Pb and Cr than others. Inconsistencies between totals amounts and the released content of Sb, As, Pb and Cr were also found. The surface topography of an antimony sulfide mineral and the species changes of Sb and sulfur (S) on its leached surface were also characterized by scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS), respectively. It is the oxidation dissolution of Sb2S3 that releases Sb. Sb(III) and S2− on the surface of the fresh mineral were oxidized to Sb(V) and S2O32− and SO42−, respectively, and finally, an equilibrium of dissolution was reached over time. The release of Sb, As, Pb and Cr from typical antimony ores is a source of Sb, As, Pb and Cr in the weathering zone; with this in mind, it is easier to understand the geochemical processes and the pollution accidents involving Sb and As within the mining areas and their surroundings.

Evaluation of heavy metal leaching from coal ash-versus conventional concrete monoliths and debris

Application of coal ash in construction materials is constrained by the potential risk of heavy metal leaching. Limited information is available on the comparative heavy metal leaching from coal ash-versus conventional concrete. The current study compared total and leached heavy metal concentrations in unbound coal ash, cement and sand; and investigated the effect of initial leachant pH on heavy metal leaching from coal-ash versus conventional concrete monoliths and their debris. Total Pb, Mn and Zn in coal ash were lower than or similar to that of other materials, while Cu and Fe showed the opposite trend. Leached concentrations of Zn, Pb, Mn, Cu and Fe in unbound coal ash, its concrete and debris were comparable and in some cases even lower than that for conventional concrete. In all cases, leached concentrations accounted for just <1% of the total concentrations. Log–log plots of concentration and cumulative release of Fe versus time based on tank leaching data showed that leaching was dominated by diffusion. Overall, the risk of Zn, Pb, Mn, Cu and Fe leaching from coal ash and its concrete was minimal and comparable to that of conventional concrete, a finding in contrast to widely held public perceptions and earlier results reported in other regions such as India. In the current study the coal ash, and its concrete and debris had highly alkaline pH indicative of high acid neutralizing and pH buffering capacity, which account for the stabilization of Zn, Pb, Mn, Cu and Fe. Based on the low risk of Zn, Pb, Mn, Cu and Fe leaching from the coal ash imply that such coal ash can be incorporated in construction materials such as concrete without adverse impacts on public and environmental health from these constituents.

Acid neutralization capacity and cost-effectiveness of antacids sold in various retail pharmacies in the United Arab Emirates

The objective of this research was to determine the acid neutralization capacity (ANC) at 37°C±2°C (as per United States Pharmacopeia 30 and the National Formulary 25) of antacid preparations sold in various retail pharmacies in the United Arab Emirates. Another important objective was to quantify the sodium and calorific content of antacids, as well as overall monthly consumption, and cost of therapy of different antacids from different manufacturers. The tablet and liquid antacids fall into four statistically different ANC groups. Three of the tablet antacids have an ANC similar to that of liquid antacid medications described as being in the high-ANC class. Of the five liquid antacids tested, only two were found to have a high ANC between four production lots at 5% level of significance. The ANC of the most effective liquid antacid was twice that of the lowest. However, this variation in capacity for neutralization is not observed in the product description of antacid brands. A standard dose is one to two teaspoons: one teaspoon will neutralize 20.2–35.92mEq and two teaspoons will neutralize 40.44–71.84mEq depending on the antacid selected. It is apparent from the results of quantification that maximum ANC combined with a minimum dosage volume–weight ratio is achieved by antacids from the high- or intermediate/high-ANC group. Consumption of these categories of antacids is beneficial as they contain less sodium and fewer calories and they are less expensive for pharmacists and/or the public. The monthly cost of daily high-dose therapy is much lower for high-ANC tablet antacids than for low-ANC tablet antacids. In conclusion, if antacids are to be used optimally, it is imperative that the ANC is specified on the product label.

Solidification characteristics and mechanisms of cement treated Pb/Zn contaminated soils from a mining site in Hunan Province, China

This paper presents a study on the stabilisation of mine soils from a mining site contaminated with heavy metals through the use of ordinary Portland cement (OPC). The aim of this study was to explore the effects of binder content (%), and the curing age of contaminated soils on the toxicity and strength properties of the contaminated soils using toxicity characteristic leaching procedure (TCLP), acid-neutralising capacity (ANC) test. Sequential extraction procedure (BCR), unconfined compression test (UCT), X-ray diffraction (XRD) and scanning electron microscopy (SEM) procedures were carried out to analyse the solidification mechanisms. The results showed that as the curing time was increased from 0 d to 28 d, OPC stabilised contaminated soil underwent several changes: 1) leaching of Zn and Pb decreased; 2) ANC (β) increased; 3) exchangeable Zn and Pb decreased; 4) residual contents increased; 5) strength improved.