FTIR spectroscopy of NH3 on acidic and ionotropic alginate aerogels

The acidity of alginate aerogel films has been investigated by infrared spectroscopy of adsorbed NH(3). Supercritical drying of the alginate provided samples with a surface area of several hundred square meters per gram, in which the probe molecule could reach all acidic sites. Free carboxylic groups were studied on acid-gelled alginates and were found to behave as effective Br?nsted acid sites. Ionotropic alginate gels formed by alkaline earth cations presented only the Lewis acidity of the cations. Ionotropic gels formed by transition metal cations presented both Lewis and Br?nsted sites, because of the presence of a fraction of free carboxylic groups. The incomplete salification was correlated to the pH of the gelling solutions.     

Slow vapor‐phase desorption of toluene from several ion‐exchanged montmorillonites

The sorption and desorption of volatile compounds from soils and clays exhibit a wide range of kinetics. While much of the sorptive interaction is very rapid, a certain fraction of volatile compounds that enter soil and clays are only slowly desorbed. It is generally believed that the formation of this recalcitrant or slowly desorbing fraction of volatile organic compounds (VOCs) in soils is due to the diffusion of compounds to poorly accessible sorption sites. However, the exact nature of these sites is in doubt. In montmorillonite, there are two likely possibilities for formation of the recalcitrant fraction: sites between the clay lamella and sites within clay particle aggregates. Because montmorillonite may be an important fraction of many soils, we have explored the formation of slowly desorbing toluene on a montmorillonite clay that was ion exchanged with five different ions (K⁺, Na⁺, Ca²⁺, Mg²⁺, and Fe³⁺) to form mineralogically similar clays with varying interlamellar spacing. The recalcitrant fraction was quantified for varying sorption and desorption times. The type of ion exchanged into the clay appears to have an important influence on the formation of a recalcitrant fraction.     

Adsorption of Adenine, Cytosine, Thymine, and Uracil on Sulfide-Modified Montmorillonite: FT-IR, M?ssbauer and EPR Spectroscopy and X-Ray Diffractometry Studies

In the present work the interactions of nucleic acid bases with and adsorption on clays were studied at two pHs (2.00, 7.00) using different techniques. As shown by Mössbauer and EPR spectroscopies and X-ray diffractometry, the most important finding of this work is that nucleic acid bases penetrate into the interlayer of the clays and oxidize Fe²⁺ to Fe³⁺, thus, this interaction cannot be regarded as a simple physical adsorption. For the two pHs the order of the adsorption of nucleic acid bases on the clays was: adenine????cytosine?>?thymine?>?uracil. The adsorption of adenine and cytosine on clays increased with decreasing of the pH. For unaltered montmorillonite this result could be explained by electrostatic forces between adenine/cytosine positively charged and clay negatively charged. However for montmorillonite modified with Na₂S, probably van der Waals forces also play an important role since both adenine/cytosine and clay were positively charged. FT-IR spectra showed that the interaction between nucleic acid bases and clays was through NH⁺ or NH ₂ ⁺ groups. X-ray diffractograms showed that nucleic acid bases adsorbed on clays were distributed into the interlayer surface, edge sites and external surface functional groups (aluminol, silanol) EPR spectra showed that the intensity of the line g????2 increased probably because the oxidation of Fe²⁺ to Fe³⁺ by nucleic acid bases and intensity of the line g?=?4.1 increased due to the interaction of Fe³⁺ with nucleic acid bases. Mössbauer spectra showed a large decreased on the Fe²⁺ doublet area of the clays due to the reaction of nucleic acid bases with Fe²⁺.     

DIATOM COMMUNITY DYNAMICS IN STREAMS OF CHRONIC AND EPISODIC ACIDIFICATION: THE ROLES OF ENVIRONMENT AND TIME1

Community dynamics of epiphytic diatoms were studied for 3 years in a chronically and an episodically acidified tributary of Buck Creek, Adirondacks. Both streams experienced pulses of acidity during hydrologic events but these pulses were more pronounced in the episodically acidified stream, where pH decreased over two units (between 4.53 and 6.62) and the acid‐neutralizing capacity (ANC) became negative. In the chronically acidified stream, pH was below 4.9 and the ANC was negative 94% of the time. In this stream, high inorganic acidity following SO₄^2? enrichment from snowmelt or rainstorms alternated with high organic acidity derived from a headwaters wetland during base flow. The fluctuating water chemistry generated shifts in diatom community composition: from exclusive dominance of Eunotia bilunaris (Ehrenberg) Mills during periods of high inorganic acidity to proliferation of several subdominant species during periods of high organic acidity. In the episodically acidified stream, the pulses of acidity were associated with high NO₃^? concentrations and the corresponding high ratios of inorganic monomeric Al (Al_im) to organic monomeric Al (Al_om). Diatom communities there were dominated exclusively by E. exigua (Brébisson) Rabenhorst year round; however, this species peaked during periods of low acidity. Periods of high acidity and Al_im:Al_om ratios were marked by a decline in E. exigua and a concomitant increase in the subdominant species. Variance partitioning into terms of environmental and temporal variance, and their covariance, suggested that diatom communities in the chronically acidic stream were governed primarily by environmental factors while in the episodically acidic stream environmental and temporal factors had equal contributions.     

Evaluation of Slurry Wall Construction Using Paper Clay for Containment of Contaminated Groundwater

Slurry walls have been used widely as passive vertical barriers to control the horizontal flow of groundwater and contaminants and therefore limit the migration of contaminants through the subsurface. The material used as slurry to reduce contaminant transport is expected to form a filter cake with low permeability along the sides of the trench wall/excavation face. In this article, paper mill sludge (hereafter referred to as paper clay) is investigated as a possible slurry. Previous research by Moo Young et al. (2000) has shown that paper clay has several properties that make its use in vertical barriers very promising. It can be compacted to low permeability values (10^?7?cm/s to 10^?9?cm/s) and has a high organic content that may act as a potential carbon source for microbial growth and sorption sites for heavy metal attenuation. To determine the feasibility of paper clay in a slurry, column testing to determine the dispersion coefficient for transport modeling, slump testing, and filter cake formation tests were performed. It is shown that the coefficient of hydrodynamic dispersion within paper clay is in the order of 10^?7?cm²/ s. It is also shown that paper clay can achieve the required slump of between 5.08 and 15.24?cm (2 and 6 in) similar to that of a workable soil-bentonite backfill. Furthermore, it is shown that the filter cakes that are formed have permeability values similar to those of soil-bentonite filter cakes.     

Reaction of labelled65ZnCl2,65ZnEDTA and65ZnDTPA with different clay-systems and some alluvial Egyptian soils

Summary The clay fraction separated from an alluvial Egyptian soil and montmorillonite clay mineral were equilibrated with CaCl₂ or NaCl solution then treated with humic acid isolated from composted clover straw to obtain different clay systems: Ca-clay, Ca-clay-HA, Na-clay, Na-clay-HA, Ca-mont and Ca-mont-HA. These clays as well as seven soil samples were reacted with different amounts of labelled⁶⁵ZnCl₂,⁶⁵ZnEDTA and⁶⁵ZnDTPA. The effectiveness of these Zn-sources for maintaining soluble Zn²⁺ ions in the equilibrium solution was the greatest for ZnDTPA and the lowest for ZnCl₂. Ca-clay provided greater Zn sorption capacity than Na-clay, and complexing the clay with humic acid depressed its capacity for Zn sorption. At the pH of the clay-systems (pH=6.5), the possibilities of Zn(OH)₂ formation were reduced especially in the presence of Zn-chelates. Reactions of⁶⁵ZnE DTA and⁶⁵ZnDTPA with the seven soils produced higher levels of soluble Zn²⁺ ions in the equilibrium solution rather than⁶⁵ZnCl₂ meanwhile ZnDTPA was more effective than ZnEDTA. The calculated Zn(OH)₂ ion product in the solution of ZnCl₂-soil systems indicated the precipitation of Zn as Zn(OH)₂. However, this was not valid in the Zn-chelates-soil systems. The results also revealed the role of soil carbonate, organic matter and soil texture as soil variables affecting Zn sorption by natural soils.     

Effects of long-term soil acidification due to nitrogen fertilizer inputs in Wisconsin

Agroecosystems are domesticated ecosystems intermediate between natural ecosystems and fabricated ecosystems, and occupy nearly one-third of the land areas of the earth. Chemical perturbations as a result of human activity are particularly likely in agroecosystems because of the intensity of that activity, which include nutrient inputs intended to supplement native nutrient pools and to support greater biomass production and removal. At a long-term fertility trial in South-Central Wisconsin, USA, significant increases in exchangeable acidity were accompanied by decreases in cation exchange capacity (CEC), base saturation, and exchangeable Ca²⁺ and Mg²⁺ with application of ammoniacal N fertilizer. Plant analysis shows that a considerable portion of the alkalinity generated by assimilation of N (and to a lesser extent by S) is sequestered in the above-ground plant parts as organic anions and is not returned to the soil if harvested. Elemental analysis of Ca-saturated soil clays indicates an loss of 16% of the CEC of the soil clay and minor increases in Fe and Al. The reversibility of these changes due to prolonged acidification is doubtful if the changes are due to soil weathering.     

Experimental charge measurement at leaving oxygen in the bovine ribonuclease A catalyzed cyclization of uridine 3'-phosphate aryl esters

The title esters are demonstrated to be specific substrates of bovine pancreatic ribonuclease A (EC 3.1.27.5). The Br?nsted dependence of kcat/Km at pH 7.50 for the enzyme-catalyzed cyclization versus the pKa of the leaving phenol exhibits two regression lines of almost identical slope for respectively 2-chlorophenols and 2,6-unsubstituted phenols: log kcat/Km = -0.20 pKa ArOH + 5.47 (n = 5, r = 0.957); log kcat/Km = -0.17 pKa ArOH + 5.79 (n = 4, r = 0.965). Comparison of the Br?nsted beta 1g's with that for the standard reaction where imidazole catalyzes the cyclization (beta 1g = -0.59) indicates considerably less development of negative charge on the leaving oxygen in the enzyme case, providing experimental evidence for the hypothesis that electrophilic assistance is involved in catalysis. The existence of two essentially parallel Br?nsted correlations is not reflected in the standard reaction of substrate with imidazole. Modeling studies indicate that the phenyl ring of the substrate can take up a range of positions away from the active site; the presence of ortho chloro substituents considerably restricts the motion of the phenyl leaving group.     

Molecular Modelling of The Mechanism of Action of Organic Clay-Swelling Inhibitors

Abstract

It is well known that the sodium smectite class of clays swells macroscopically in contact with water, whereas under normal conditions the potassium form does not. In recent work using molecular simulation methods, we have provided a quantitative explanation both for the swelling behaviour of sodium smectite clays and the lack of swelling of potassium smectites [1]. In the present paper, we apply similar modelling methods to study the mechanism of inhibition of clay-swelling by a range of organic molecules.

Experimentally, it is known that polyalkylene glycols (polyethers) of intermediate to high relative molecular mass are effective inhibitors of smectite clay swelling. We use a range of atomistic simulation techniques, including Monte Carlo and molecular dynamics, to investigate the interactions between a selection of these compounds, water, and a model smectite clay mineral. These interactions occur by means of organised intercalation of water and organic molecules within the galleries between individual clay layers.

The atomic interaction potentials deployed in this work are not as highly optimised as those used in our clay-cation-water work [1]. Nevertheless, our simulations yield trends and results that are in qualitative and sometimes semi-quantitative agreement with experimental findings on similiar (but not identical) systems. The internal energy of adsorption of simple polyethers per unit mass on the model clay is not significantly different from that for water adsorption; our Monte Carlo studies indicate that entropy is the driving force for the sorption of the simpler organic molecules inside the clay layers: a single long chain polyethylene glycol can displace a large number of water molecules, each of whose translational entropy is greatly enhanced when outside the clay. Hydrophobically modified polyalkylene glycols also enjoy significant van der Waals interactions within the layers which they form within the clay galleries.

In conjunction with experimental studies, our work furnishes valuable insights into the relative effectiveness of the compounds considered and reveals the generic features that high performance clay-swelling inhibitors should possess. For optimal inhibitory activity, these compounds should be reasonably long chain linear organic molecules with localised hydrophobic and hydrophilic regions along the chain. On intercalation of these molecules within the clay layers, the hydrophobic regions provide an effective seal against ingress of water, while the hydrophilic ones enhance the binding of the sodium cations to the clay surface, preventing their hydration and the ensuing clay swelling.     

Specific activation of a tyrosine----glycine mutant of delta 5-3-ketosteroid isomerase by phenols.

A key unknown still to be explored concerning the mechanism of delta 5-3-ketosteroid isomerase from Pseudomonas testosteroni is the extent of the proton transfer between tyrosine-14 of the enzyme and the C-3 carbonyl oxygen of the steroid substrate. This report is a preliminary study of a system we are developing to allow us eventually to use a Br?nsted analysis to measure this transfer. We describe the construction of an expression vector and tyrosine-14----glycine-14 mutant of the enzyme and its specific activation, in the manner of chemical rescue, by a variety of phenolic compounds. We suggest that the binding region of phenol is very tight and that the level of activation may be a result of steric constraints as well as of differences in the pKa' of the phenol.     

Factors Affecting the Ascorbate- and Phenolic-dependent Generation of Hydrogen Peroxide in Dulbecco's Modified Eagles Medium

Ascorbate and several polyphenolic compounds have been reported to undergo oxidation in cell culture media to generate hydrogen peroxide (H?0?), but the mechanism underlying this has not been established. We therefore investigated the parameters affecting H?0? production. H?0? gene ration from ascorbate, gallic acid and other phenolic compounds in Dulbecco's Modified Eagles' Medium (DMEM) at 37°C under 95% air - 5% C0? was not significantly inhibited by high (5-10 mM) concentration of EGTA, o-phenanthroline or desferrioxamine, but partial inhibition by EDTA and diethylenetriaminepentaacetic acid (DTPA) was observed. Incubation of DMEM alone at 37°C led to an upward drift of pH, even under an atmosphere of 95% air - 5% C0?. Prevention of this pH rise by increasing the concentration of N-[2-hydroxyethyl]piperazine-N'-[2-ethanesulfonic acid] (Hepes) buffer lowered the levels of H?0? generated by ascorbate and phenolic compounds, but there was still substantial H?0? generated at pH 7.4. Mixtures of ascorbate and phenolic compounds led to less H?0? generation than would be expected from the rates observed with ascorbate or phenolic compounds alone. Ascorbate prevented the loss of gallic acid incubated in DMEM. The role of metal ions and other constituents of the culture medium in promoting H?0? generation is discussed.     

A field comparison of lime requirement indices for maize

Due, in part, to the relative paucity of published comparisons based on field generated data, there is still poor agreement regarding the relative merits of lime requirement indices based on exchangeable Al and those based on pH. The objective of this study was to compare such indices using results obtained from long-term field experiments. Data were obtained over 22 site-years from lime trials conducted on clay (Typic Haplorthox) and sandy loam (Plinthic Paleudult) soils differing widely in organic carbon content. Relative maize (Zea mays L.) yields were used to compare the prognostic value of soil pH with indices obtained using exchangeable Al and exchangeable acidity (Al+H). Both within and across soils, pH proved to be markedly inferior to Al based indices. Exchangeable acid saturation of the effective cation exchange capacity, a readily obtained and popular index of lime requirement in some countries, proved as effective as less easily acquired indices based on exchangeable Al per se. The findings reported are consistent with those of many glasshouse studies and support the viewpoint that indices based on Al or acid saturation should replace pH as a measure of lime requirement.     

Preparation and antioxidant property of extract and semipurified fractions of Caulerpa racemosa

A microwave-assisted extraction method has been developed for the extraction of phenolic compounds from the green alga, Caulerpa racemosa. An L₁₈(3)⁵ orthogonal experimental array was designed to optimize the extraction conditions. Total phenolic content was determined by Folin–Ciocalteu method. Under the optimized conditions (microwave power, 200?W; ethanol concentration, 60%; extraction time, 40?min; extraction temperature, 50°C; solvent-to-material ratio, 40?mL?g^?1), the maximum total phenolic content reached 67.89?±?3.88?mg 100?g^?1 dried sample. The crude ethanolic extract was further purified by liquid–liquid partition to afford two fractions, of which the ethyl acetate-soluble fraction (EAF) exhibited the strongest antioxidant activity in the hydroxyl and 2,2-diphenyl-1-picrylhydrazyl radical scavenging assays and reducing power. EAF was further divided into four subfractions, designated as EAF1 to EAF4, by silica gel vacuum liquid chromatography. The antioxidant capacity of the subfractions was in the following order: EAF1>EAF2>EAF4>EAF3. The results of IR spectral and HPLC analysis, including the research on the correlation between antioxidant capacity and total phenolic content, suggested that phenolic compounds of medium polarity were the major contributors to the antioxidative activity of C. racemosa. The present findings might contribute to a rational basis for the use of phenolic-rich fractions and subfractions as natural antioxidants in different food/pharmaceutical products.     

Siderophore sorption to clays

Siderophores are low molecular weight organic ligands exuded by some aerobic organisms and plants to acquire Fe under Fe-limited conditions. The hydroxamate siderophores may sorb to aluminosilicate clays through a variety of mechanisms depending upon the nature of the clay and of the siderophore along with solution conditions such as pH, ionic strength, and presence of metal cations. They may also affect metal binding to clays. Here, we review previous studies of siderophore sorption to aluminosilicate clays; briefly discuss how the techniques of X-ray diffractometry, Fourier-transform infrared spectroscopy, and X-ray absorption spectroscopy may be applied to such studies; review effects of siderophores on metal sorption to clays; and highlight some areas for future research.     

The interpretation of site-directed mutagenesis experiments by linear free energy relations

Fersht and co-workers have applied a linear free energy relation (Br?nsted equation) to analyze site-directed mutagenesis experiments involving the enzyme tyrosyl-tRNA synthetase and have suggested that the Br?nsted exponent is linearly correlated with the value of the reaction coordinate at the transition state. We point out that when the mutants differ solely through the formation or deletion of a hydrogen bond away from the reaction center, a linear free energy relation is expected only in limiting cases for which the Br?nsted relation exponent is 0, 1 or infinity. The results may be correlated with a conformational coordinate but not with the development of the reaction coordinate per se.     

Utilization of iron sulfides for wastewater treatment: a critical review

Acid mine drainage due to weathering of iron sulfide minerals is one of the biggest global environmental issues. However, due to the unique physicochemical properties of natural and synthesized iron sulfides (i.e. pyrite, pyrrhotite, and mackinawite), they can be effectively used for wastewater treatment. These properties, such as ≡SH functional groups as Lewis bases, reducibility of surface Fe and S species, dissolved Fe²⁺ as a catalyst, and dissolved S^2? as an electron donor, are extensively reviewed in this article. The target water pollutants include toxic metals (i.e. lead, mercury, cadmium, and hexavalent chromium) and metalloid (i.e. arsenic), radionuclides (i.e. uranium and selenium), organic contaminants (i.e. chlorinated organic pollutants, benzene and polycyclic aromatic hydrocarbons), and nutrients (i.e. nitrogen and phosphorus). The dominant interaction mechanisms between iron sulfides and these contaminants, and the removal efficiencies are elucidated. This article focuses on the role of iron sulfides as functional materials for wastewater treatment. A recent development of nanostructured pyrrhotite with a high specific surface area for wastewater treatment is also highlighted.     

Phenolic compounds and antioxidants from Eucalyptus camaldulensis as affected by some extraction conditions,a preparative optimization for GC-MS analysis

Abstract

Four organic solvents along with water were applied for the conventional extraction of Eucalyptus camaldulensis (Myrtaceae), phenolic contents and antioxidant activities were investigated through variable protocols and correlation coefficients were considered, the phenolic composition was also characterized by Gas chromatography-mass spectrometry (GC-MS). Using solvents with dissimilar polarities affected the phenolic yields extracted from E. camaldulensis and their related antioxidant activities varied significantly among the four investigated plant organs. The leaf extract of acetone 70% contained the highest amount of phenolic compounds (46.56?mg/g dry weight); while the bud-water boiled extract maintained the maximum value of tannins (45.68?mg/g dry weight). Correlation coefficients indicated that phenolic compounds were mostly accountable for the phosphomolybednum antioxidant potentials (0.520), followed by tannins (0.460). Also, both the reducing power activities and hydrogen peroxide scavenging of E. camaldulensis extracts positively correlated with tannins, but at different significance degrees. However, the GC-MS analysis revealed that most of the detected phenolic constituents were more abundant in the plant seed. So, the existence of some other compounds such as organic acids, along with phenolics, may have increased the antioxidant potentials of leaf and bud. Undeniably, the optimization of extraction conditions could stimulate the antioxidant capabilities of the plant extracts of E. camaldulensis.     

Sorption of hydrophobic organic contaminants and trace metals on phytoplankton and implications for toxicity assessment

The partitioning of trace metals and hydrophobic organic contaminants to phytoplankton determines their toxicity as well as their fate and transport in aquatic ecosystems. Accurate impact assessments, therefore, depend on a good understanding of the factors regulating the sorption of these compounds to biotic particles. The accumulation of chlorinated organic compounds in phytoplankton is generally considered as being due solely to physical sorption, described by reversible equilibrium models based on Langmuir or Freundlich isotherms. On the other hand, the uptake of trace metals is a two phase process: a fast sorption component viewed as an ionexchange or a covalent bonding process with cell surface ligands, followed by an intracellular transport phase that is dependent on cellular metabolic activity. The uptake of inorganic and hydrophobic organic pollutants and their bioaccumulation are influenced in a complex manner by duration of exposure and cell density, by environmental factors such as pH, the concentration of cations and of dissolved and colloidal organic matter, as well as by phytoplankton physiological condition. High concentrations of H⁺, Ca²⁺, and Mg²⁺ ions will reduce trace metal sorption by directly competing for uptake sites on the cell's surface, whereas the presence of dissolved organic carbon such as natural and synthetic chelators and phytoplankton exudates will reduce the bioavailability of both trace metals and hydrophobic organic contaminants. Thus, the impact of toxic contaminants on phytoplankton may be determined as much by the factors influencing uptake and partitioning as by the potency of the toxicants and interspecies differences in sensitivity. Recommendations for improving toxicity assessments are presented.     

Quantification of nitrophenols,chlorophenols, and hexachlorocyclohexanes in agricultural soils in the vicinity of industrial area for the assessment of human health hazard and risk

In this study, quantification of nitrophenol (NP), chlorophenol (CP), and hexachlorocyclohexane (HCH) compounds in agricultural soils in the vicinity of the industrial region in northern Uttar Pradesh, India was carried out for the assessment of human health hazard. The concentration of ∑NP, ∑CP, and ∑HCH compounds ranged 0.33–3.64 mg kg^?1, 0.06–3.18 μg kg^?1, and 1.23–17.24 mg kg^?1, respectively, and were within the soil quality guidelines for the protection of human and environment health. Human health hazard index and cancer risk, on the basis of average daily intake of these compounds through soil for human adults and children, was lower than the acceptable limit. This study suggested low health hazard and risk due to phenolic and HCH compounds to human population.     

Responses of maize grain yield to changes in acid soil characteristics after soil amendments

An experiment was conducted from 1997 to 2000 on an acid soil in Cameroon to assess the effectiveness of cultivating acid tolerant maize (Zea mays L.) cultivar and the use of organic and inorganic fertilizers as options for the management of soil acidity. The factors investigated were: phosphorus (0 and 60 kg ha^?1), dolomitic lime (0 and 2 t ha^?1), organic manure (no manure, 4 t ha^?1 poultry manure, and 4 t ha^?1 of leaves of Senna spectabilis), and maize cultivars (ATP-SR-Y – an acid soil-tolerant, and Tuxpeño sequia – an acid susceptible). On acid soil, maize grain yield of ATP-SR-Y was 61% higher than the grain yield of Tuxpeño sequia. Continuous maize cultivation on acid soil further increased soil acidity, which was manifested by a decrease in pH (0.23 unit), exchangeable Ca (31%) and Mg (36%) and by an increase in exchangeable Al (20%). Yearly application of 60 kg ha^?1 of P for 3 years increased soil acidity through increases in exchangeable Al (8%) and H (16%) and a decrease in exchangeable Ca (30%), Mg (11%) and pH (0.07 unit). Lime application increased grain yield of the tolerant (82%) and susceptible (208%) cultivars. The grain yield increases were associated with a mean decrease of 43% in exchangeable Al, and 51% in H, a mean increase of 0.27 unit in pH, 5% in CEC, 154% in exchangeable Ca, and 481% in Mg contents of the soil. Poultry manure was more efficient than leaves of Senna producing 38% higher grain yield. This yield was associated with increases in pH, Ca, Mg and P, and a decrease in Al. The highest mean grain yields were obtained with lime added to poultry manure (4.70 t ha^?1) or leaves of Senna (4.72 t ha^?1). Grain yield increase was more related to the decrease in exchangeable Al (r = ?0.86 to ?0.95, P<0.01) and increase in Ca (r = 0.78–0.94, P<0.01), than to pH (r = ?0.57 (non-significant) to ?0.58 (P<0.05)). Exchangeable Al was the main factor determining pH (r = ?0.88 to ?0.92, P<0.01). The yield advantage of the acid tolerant cultivar was evident even after correcting for soil acidity. Acid soil-tolerant cultivars are capable of bringing unproductive acid soils into cultivation on the short run. The integration of soil amendments together with acid soil-tolerant cultivar offers a sustainable and comprehensive strategy for the management of acid soils in the tropics.