Low pH Solution Research Articles

Preconcentration and determination of the Yb(III) using transcarpathian clinoptilolite

The sorption properties of Transcarpathian clinoptilolite towards trace amounts of Yb(III) under dynamic conditions have been studied. It is shown that the most effective sorption of this REE occurs from low alkaline solution (pH 10.0). The buffer solution has been used to maintain the constant value of pH, which permits to improve metrological characteristics of the preconcentration methods of Yb. Moreover, in this case the constant ionic strength minimizes influence of other water components on the sorption process of Yb(III) ions. The trace amounts of Yb(III) are sorbed most effectively with borate buffer solution. The final concentration of the borate buffer in the sample solution is 2.1·10 –4 М. It is known that such rare elements as Nd(III), Ce(III), Eu(III) and Gd(III) practically are not sorbed on Transcarpathian clinoptilolite from the solutions at pH 11.0. The differences in the sorption mechanisms of these REE give an opportunity to selectively preconcentrate Yb(ІІІ) from the solutions (рН 11.0) containing Nd(III), Ce(III), Eu(III) and Gd(III). Ytterbium is sorbed with the best efficiency on the uncalcined clinoptilolite samples. The calculation of the distribution of different forms of Yb(III) in aqueous solutions depending on pH at various values of the total concentration has been carried out. The sorption capacity of clinoptilolite under optimal conditions (diameter grains of sorbent – 0.200–0.315 mm; pH 10.0; low rate of the solution of Yb(III) with the concentration of 0.5 μg·mL –1 through the sorbent – 5 mL·min –1 ) is 13.2 μg·g –1 . The influence of the most common water ions on the preconcentration of Yb(III) on Transcarpathian clinoptilolite has been established. The most effective desorbent of Yb(III) from the clinoptilolite is1 М solution of NaCl, acidified with hydrochloric acid to рH 2.5, which provides a 100 % withdrawal of Yb from the zeolite matrix. The solid-phase extraction procedure with natural Transcarpathian clinoptilolite has been proposed for the preconcentration of trace amounts of Yb(III) ions from aqueous solutions for a final spectrophotometric determination using arsenazo III. Keywords: sorption, ytterbium, solid phase extraction, clinoptilolite.

PH-shift stress on antibodies.

Antibody unfolding and aggregation have been gaining increasing concern as the need for pharmaceutical antibodies with high quality has increased. Assays for continuous application of severe stress to antibodies, which are typically employed to evaluate tolerance to aggregation or to understand the mechanism of aggregation, induce both unfolding and aggregation simultaneously. In this chapter, we describe the pH-shift stress on antibodies that uses a low pH solution to unfold the antibody and a neutralizing solution to induce folding and the aggregation. This pH-shift technique with light scattering analysis will be a useful assay to evaluate antibody aggregation at a neutral pH and ambient temperature without generation of unfolded molecules during aggregation.

Synthesis of Graphene β-Cyclodextrin Nano-Composite for Removal of Dyes from Waste Water

Graphene oxide & its nano composite was synthesized using the Hummer’s method. Synthesized novel graphene oxide-beta-cyclodextrin (GO-CD) composites is applied as adsorbent for adsorption and elimination of hazardous endocrine disrupting compounds, such as Methylene Blue from the solvent phase of an aqueous solution. Methylene Blue from aqueous solutions by batch adsorption technique under varying conditions such as contact time, pH and temperature. Lower solution pH (3 to 5) favoured the adsorption of reactive dye onto graphene oxide-beta-cyclodextrin composites. Endocrine disrupting compounds are highly toxic substances that cannot be removed from treated waste water through conventional methods. The optimized values of effective parameters were 20 minute (contact time), 20mg (adsorbent dosage), and 7.5(pH) and 0.00001 (initial concentration) these values were optimized using batch adsorption study. Hence, the developed adsorbent could be efficiently used for rapid adsorption and removal of noxious impurities. The results indicated that graphene oxide-beta-cyclodextrin composites have shown reduction in colour of waste water by 60-80% and also have shown reduction in other polluting parameters.

Preparation, optimization and swelling study of carboxymethyl sago starch (CMSS)\u2013acid hydrogel

In this study, sago starch was modified in order to enhance its physicochemical properties. Carboxymethylation was used to introduce a carboxymethyl group into a starch compound. The carboxymethyl sago starch (CMSS) was used to prepare smart hydrogel by adding acetic acid into the CMSS powder as the crosslinking agent. The degree of substitution of the CMSS obtained was 0.6410. The optimization was based on the gel content and degree of swelling of the hydrogel. In this research, four parameters were studied in order to optimize the formation of CMSS–acid hydrogel. The parameters were; CMSS concentration, acetic acid concentration, reaction time and reaction temperature. From the data analyzed, 76.69% of optimum gel content was obtained with 33.77 g/g of degree of swelling. Other than that, the swelling properties of CMSS–acid hydrogel in different media such as salt solution, different pH of phosphate buffer saline solution as well as acidic and alkaline solution were also investigated. The results showed that the CMSS–acid hydrogel swelled in both alkaline and salt solution, while in acidic or low pH solution, it tended to shrink and deswell. The production of the hydrogel as a smart material offers a lot of auspicious benefits in the future especially related to swelling behaviour and properties of the hydrogel in different types of media.

1,4-β-d-Glucomannan from Dendrobium officinale Activates NF-кB via TLR4 to Regulate the Immune Response.

2,3-O-acetylated-1,4-β-d-glucomannan (DOP-1-1) is a polysaccharide isolated from the stem of Dendrobium officinale. DOP-1-1 has been demonstrated to have remarkable immunomodulatory properties, but little is known about the influence of its structural diversity on bioactivity (and even less about the exact mechanism underlying its immune responses). First, DOP-1-1 was stabilized at different temperatures and pH conditions based on differential scanning calorimetry and size exclusion-chromatography–high-performance liquid chromatography. Then, a detailed study on the effects of DOP-1-1 on a human leukemia monocytic cell line (THP-1) under normal conditions was undertaken. DOP-1-1 promoted the translocation of nuclear factor-kappa B (NF-κB) and degradation of IκB proteins. The expression of genes and proteins closely associated with the immune, survival and apoptotic functions of NF-κB were analyzed by quantitative real-time RT-PCR. Furthermore, CCL4 and IP10 were confirmed to be the novel targets of the immune response stimulated by DOP-1-1. The phosphorylation of NF-кB was inhibited by treatment with a toll-like receptor 4 (TLR4) antagonist (TAK-242) and myeloid differentiation factor 88 (MyD88) inhibitor (ST2825). These data suggested: (i) the O-acetylated glucomannan DOP-1-1 is present in the steady state in low-pH solutions; (ii) DOP-1-1 can induce an immune response through NF-кB mediated by a TLR4 signaling pathway; and (iii) CCL4 and IP10 could be the novel targets of the immune response stimulated by O-acetylated glucomannan.

Mechanical and surface properties analysis of restorative materials submitted to erosive challenges in situ.

Objective:This study aims to evaluate the effect of acidic solutions (AS) on surface roughness (Ra) and microhardness of restorative materials (RM).Materials and Methods:Eight volunteers wore intraoral palatal devices (IPD) containing samples of RM: Ketac Nano (KN); Ketac Nano + Biscover LV (KN-B); Esthet-X (EX); Esthet-X + Biscover LV (EX-B); Supreme XT (SXT); Supreme XT + Biscover LV (SXT-B); and bovine enamel. The samples were submitted to three phases: (1) immersion in 0.01M hydrochloric acid (HCl) – 10 min, three times/day (14 days); (2) immersion in soft drink (Sprite®) – 10 min, three times/day (14 days); and (3) keeping in saliva (14 days). Changes in Ra/microhardness were measured before/after the three phases.Statistical Analysis:ANOVA (α = 0.05) and Fisher's test.Results:Materials sealed with Biscover LV (B) presented lowest values in all periods. KN glass ionomer cement showed highest Ra values after exposure in AS. Application of B did not reduce the Ra for the composites studied, except for EX after immersion in HCl. AS promoted changes in Ra/microhardness of RM, except for sealed materials.Conclusions:The acids used were able to change the Ra and microhardness of RM, except of the sealed materials. The resin-modified GIC showed the most significant changes after immersion in AS; and the composites sealed with B, even after immersion in acidic solutions (AS), showed the lowest Ra values and the least degradation in microhardness, especially when subjected to low pH solutions.

Adsorption and Photocatalytic Degradation of Anionic and Cationic Surfactants on Nitrogen‐Modified TiO2

AbstractAdsorption and photocatalytic decomposition of anionic and cationic surfactants are presented. Two different types of photocatalysts were studied, commercial TiO2‐P25 (Evonik) with pHpzc = 5.65 and nitrogen‐modified TiO2/N pHpzc = 6.7 (point of zero charge). Two different types of surfactants were used: anionic surfactant NaDBS (sodium dodecylbenzene sulfonate) and cationic surfactant BtCl (benzethonium chloride). Obtained adsorption isotherms of NaDBS and BtCl comply with the conditions of monolayer Langmuir model isotherms. The maximal anionic surfactant adsorption took place at acidic pH and it was higher for TiO2/N (196 mg g−1) than for commercial TiO2‐P25 (140 mg g−1). There was the opposite situation in the case of cationic surfactants, higher adsorption took place at alkaline condition and it was higher for TiO2/N (100 mg g−1) than for commercial TiO2‐P25 (85 mg g−1). Photocatalytic degradation has been found to be more effective in neutral and high than in low pH solutions for both surfactants. It is mainly the difference between charges of the surface of photocatalysts and ionic parts of individual surfactants that determined the effectiveness for each of them.

Thermodynamics, crystal chemistry and structural complexity of the Fe(SO4)(OH)(H2O) x phases: Fe(SO4)(OH), metahohmannite, butlerite, parabutlerite, amarantite, hohmannite, and fibroferrite

Using combination of acid-solution, high-temperature oxide-melt, relaxation, and differential scanning calorimetry, we have determined the thermodynamic properties of all phases in the system Fe(SO 4 )(OH)–H 2 O (estimated values in parentheses): Using these data, phase diagrams for low-temperature (25 °C) systems in contact with aqueous solutions predict that these phases should precipitate from extremely concentrated, low-pH solutions. In a relative humidity–temperature space, only Fe(SO 4 )(OH), parabutlerite, and amarantite have stability fields; the higher hydrates would require unrealistically high air humidities to form as stable phases. High-temperature high-pressure phase diagrams produce reasonable topologies, although the details of the phase relations between Fe(SO 4 )(OH), Fe 2 (SO 4 ) 3 , and hydronium jarosite deserve more work. We also present a new structural model for amarantite, including the positions of the H atoms, and an analysis of the hydrogen bonding network in this mineral. Using the concept of information density in minerals, the Fe(SO 4 )(OH)(H 2 O) x phases were analyzed. This analysis lends some validity to the premise that more complex structures are also the more stable ones, but other systems should be investigated to test these trends.

Influence of morphology on electrical and optical properties of graphene/Al-doped ZnO-nanorod composites

The development of future 3D-printed electronics relies on the access to highly conductive inexpensive materials that are printable at low temperatures (<100 ◦C). The implementation of available materials for these applications are, however, still limited by issues related to cost and printing quality. Here, we report on the simple hydrothermal growth of novel nanocomposites that are well suited for conductive printing applications. The nanocomposites comprise highly Al-doped ZnO nanorods grown on graphene nanoplatelets (GNPs). The ZnO nanorods play the two major roles of (i) preventing GNPs from agglomerating and (ii) promoting electrical conduction paths between the graphene platelets. The effect of two different ZnO-nanorod morphologies with varying Al-doping concentration on the nanocomposite conductivity and the graphene dispersity are investigated. Time-dependent absorption, photoluminescence and photoconductivity measurements show that growth in high pH solutions promotes a better graphene dispersity, higher doping levels and enhanced bonding between the graphene and the ZnO nanorods. Growth in low pH solutions yields samples characterized by a higher conductivity and a reduced number of surface defects. These samples also exhibit a large persistent photoconductivity attributed to an effective charge separation and transfer from the nanorods to the graphene platelets. Our findings can be used to tailor the conductivity of novel printable composites, or for fabrication of large volumes of inexpensive porous conjugated graphene-semiconductor composites.

Co3O4 nanocrystals/3D nitrogen-doped graphene aerogel: A synergistic hybrid for peroxymonosulfate activation toward the degradation of organic pollutants

3D porous Co3O4/nitrogen-doped graphene aerogel (NGA) hybrid for heterogeneous activation of peroxymonosulfate (PMS) was prepared by feasible hydrothermal and freeze-drying methods. The morphology, crystal structure and chemical composition of the catalyst were investigated by scanning electron microscopy, X-ray diffractometer, X-ray photoelectron spectroscopy, Raman spectra and Fourier transform infrared spectroscopy. Co3O4/NGA at a high N doping level of 7.6% (in atomic percentage) exhibited excellent catalytic performance for acid orange 7 (AO7) degradation, with almost complete removal within 30 min. Moderate PMS content, higher temperature and lower solution pH conditions would facilitate the decomposition of AO7. The catalyst possesses excellent long-term stability and recycling performance with simple separation and post-treatment approaches. Kinetic model was developed to simulate the transformation of main active radical species and the AO7 oxidation profiles, considering effects of coexisting ions (Cl− and HCO3−). Based on results of electron spin resonance, typical quenching tests and kinetic calculation, sulfate radicals play dominate role in AO7 degradation. Co3O4 nanocrystals and the new active sites created by nitrogen doping into graphene honeycomb network should synergistically contribute to the high degradation efficiency. This work has expanded the possibility of recyclable catalysts design for heterogeneous activation of PMS, with a dual catalytically active center and desirable stability.

A new continuous flow-through structured reactor for the photodegradation of aqueous contaminants

A flow-through photo reactor with a stainless steel mesh-supported ZnO catalytic disc has been designed in this work. The preparation method of the catalyst includes the use of Triton™ X-100 and methylene blue (MB) in order to enhance the homogeneity of the ZnO and its adhesion to the mesh. The catalysts exhibit a high surface area (∼100 m2/g). The photocatalytic reaction is restricted to the most external non-polar edges of the ZnO nanosheets due to the low pH of the MB solution and to the fact that the polar surfaces are hydrophobic. Despite this, the performance of the flowthrough reactor is superior to that of other micro fluidic systems. The catalyst undergoes a slight deactivation during the reaction, though the activity can be restored, without causing any structural changes, by passing water through the catalyst under UV irradiation. The loss of ZnO through photocorrosion is low, especially when compared to the loss experienced by the same catalyst prepared without using methylene blue.

Recovery of V(V) from complex vanadium solution using capacitive deionization (CDI) with resin/carbon composite electrode

The resin-activated carbon composite (RAC) electrodes were fabricated and applied in capacitive deionization for recovery of V(V) from complex vanadium solution. The adsorption capacity of the RAC electrode for V(V) is extremely low and the reduction of V(V) is significant in low pH solution, but the adsorbed V(V) on the electrode increases obviously and the reduction of V(V) gradually diminishes with the rise of pH. However, as the pH is increased to 10, the adsorbed V(V) on the RAC electrode declines. The higher applied potential is beneficial to the adsorption of V(V) and 1.0 V is appropriate for the adsorption. The impurities ions (Al, P and Si) are mainly adsorbed in the electric double layers on the RAC electrode and V(V) is dominantly adsorbed by the resins in the electrode. The adsorbed impurity ions can be easily removed by diluted H2SO4 and V(V) can be effectively eluted by 10% NaOH solution. The vanadium-bearing eluent can be recycled to recover and enrich vanadium from the complex solution. The performance of the RAC electrode keeps stable during the cyclic operation. This study may provide a promising and novel method for the recovery and separation of metals from aqueous solution.

Adsorption of Remazol Brillant Green 6B (RBG 6B) on chitin: process optimization using response surface methodology

In the present study, the adsorption of Remazol Brillant Green 6B (RBG 6B) on chitin which characterized by BET, FTIR, XRD and SEM analysis was studied. Response surface methodology (RSM) was applied to determine interaction between solution pH, initial RBG 6B concentration and chitin dosage being individual variables and to optimize operating conditions. According to results of variance analysis (ANOVA), the second order polynomial model was statistically significant (P&lt;0.0001) and coefficient of determination value (R2=0.98) was high. It was determined that dye removal efficiency increased when low solution pH and initial RBG 6B dye concentration and high chitin dosage were used. The maximum dye removal efficiency was obtained as 88% at solution pH of 3.0, initial RBG 6B concentration of 75 mg L-1 and chitin dosage of 5.0 g L-1. The isotherms and kinetics studies showed that Freundlich isotherm and pseudo-second-order kinetics model fitted well to the RBG 6B adsorption data.

Incorporation of nanoscale zero-valent iron particles in monodisperse mesoporous silica nanospheres: Characterization, reactivity, transport in porous media

In this study, nanoscale zerovalent iron (nZVI) was incorporated inside the channels of monodisperse mesoporous silica nanospheres (MSN). The techniques of TEM, XRD, FTIR, N2 adsorption-desorption and XPS were conducted to characterize the composition and structure of the composite materials. Results revealed that nZVI was well dispersed in the channels of MSN, and the synthesized Fe/Si composite materials (nZVI@MSN) remained monodisperse nanospheres with the size of 100 nm which was in the optimal size range for transport through porous media. The loading of Fe (wt %) in nZVI@MSN was 4.3% and the BET surface area of nZVI@MSN was 743.49 m2/g. Batch experiment results revealed that the removal efficiency of nitrobenzene (NB) by nZVI@MSN was 42.9% higher than that of bare nZVI. Lower initial solution pH could favour the removal of NB. Most of the common ions including Na+, K+, Cl−, NO3− and SO42- presented no obvious effect on NB removal. While, Ca2+, Mg2+ and HCO3− showed promoted inhibitory effect on NB degradation with the increased of ion concentration. After seven cycles of reduction, the removal efficiency of NB by nZVI@MSN was higher than 86%, indicating its high stability and durability. Transport experiments showed that nZVI@MSN performed better mobility in porous aquifer media than bare nZVI.

A novel process for the separation and recovery of value-added metals from manganese–silver ores by EDTA/EDTA–2Na and thiosulfate

A novel process for the recovery of manganese by EDTA/EDTA–2Na leaching and the recovery of silver by thiosulfate leaching with resultant EDTA–Mn as the catalyst from manganese–silver ores was developed in this study. Initially, insoluble manganese(IV) was reductively leached by EDTA/EDTA–2Na in an aqueous medium, and then silver was extracted by thiosulfate with EDTA–Mn(II/III) as the catalyst that was produced in situ in the manganese leaching stage, instead of a copper(II) and ammonia catalytic system. The EDTA–S2O32− leaching system gave higher manganese and silver leaching efficiencies with lower solution pH of 5–6. And the EDTA–2Na–S2O32− leaching system, a relatively moderate solution with pH of 7–8, presented less consumption of thiosulfate in the leaching of silver. In total, 97.5% of manganese and 92.6% of silver were leached in the EDTA–S2O32− leaching system, and 93.7% of manganese and 91.2% of silver were leached in the EDTA–2Na–S2O32− leaching system under the most suitable conditions. Moreover, most of EDTA/EDTA–2Na can be recovered by acidification, and the consumption of S2O32− can be reduced in the presence of EDTA complex. This new process can be used to recover manganese and silver from manganese–silver ores effectively and interoperably.

Adsorption of polysorbate 20 and proteins on hydrophobic polystyrene surfaces studied by neutron reflectometry.

Understanding the adsorption of protein and surfactant molecules on hydrophobic surfaces is very important for storage stability and delivery of pharmaceutical liquid formulations as many commonly-used devices, such as drug containers and syringes, have hydrophobic surfaces. Neutron reflectometry is used here to investigate the structure information of the adsorption process of non-ionic surfactant (polysorbate 20) and proteins (monoclonal antibody (mAb) and lysozyme) on polystyrene surfaces. Thickness of adsorbed polysorbate 20 thin film is observed to be ≈21 Å, comparable to the radius of gyration of polysorbate 20 micelles in solution. Although no lysozyme adsorption is observed on the polystyrene surface in low solution pH condition, the mAb can be strongly absorbed on the polystyrene surface with a layer thickness of ≈145 Å. The mAb concentration near the surface is about 135 mg/ml significantly larger than the bulk protein concentration. The differences in adsorption behavior are attributed to different protein interactions with a hydrophobic surface. Further, both surfactants and proteins adsorbed on the polystyrene surfaces can not be rinsed off using pure water.

Activation of rat masticatory muscle afferent fibres by acidic pH

Previous research findings have suggested an important role for acid sensing ion channels (ASICs) in muscle pain mechanisms. This study was conducted to determine if masticatory muscle afferent fibres express ASICs, if there are sex differences in this expression, and to compare the effects of low pH and hypertonic saline on afferent fibres that innervate the masticatory muscle in vivo. Immunohistochemistry methods were applied to examine the expression of ASICs in trigeminal ganglion neurons, while in vivo electrophysiology techniques were employed to examine changes in masticatory muscle afferent fibre excitability. Both ASIC1 and ASIC3 were expressed by predominantly larger masticatory muscle ganglion neurons, but the frequency of ASIC3 expression (56%) was significantly greater than ASIC1 (35%). No sex-related differences in expression were identified. Injection of pH 5.8, but not pH 6.8, phosphate buffered saline evoked afferent discharges that were significantly greater than those evoked by pH 7.4 buffer (control). Since ASIC3 channels are not activated until the pH is around 6, these results indicate that activation of both channels contributes to excitation of masticatory muscle afferent fibres. The results further show that many masticatory muscle afferent fibres, which respond to low pH, are low threshold mechanoreceptors. These findings may explain why injection of low pH solutions into the masticatory muscles of healthy humans is not associated with significant muscle pain.

Unusual Isothermal Hysteresis in DNA i-Motif pH Transitions: A Study of the RAD17 Promoter Sequence

We have interrogated the isothermal folding behavior of the DNA i-motif of the human telomere, dC19, and a high-stability i-motif-forming sequence in the promoter of the human DNA repair gene RAD17 using human physiological solution and temperature conditions. We developed a circular-dichroism-spectroscopy-based pH titration method that is followed by analysis of titration curves in the derivative domain and found that the observed pH-dependent folding behavior can be significantly different and, in some cases, multiphasic, with a dependence on how rapidly i-motif folding is induced. Interestingly, the human telomere sequence exhibits unusual isothermal hysteresis in which the unfolding process always occurs at a higher pH than the folding process. For the RAD17 i-motif, rapid folding by injection into a low-pH solution results in triphasic unfolding behavior that is completely diminished when samples are slowly folded in a stepwise manner via pH titration. Chemical footprinting of the RAD17 sequence and pH titrations of dT-substituted mutants of the RAD17 sequence were used to develop a model of RAD17 folding and unfolding. These results may provide valuable information pertinent to i-motif use in sensors and materials, as well as insight into the potential biological activity of i-motif-forming sequences under stepwise or instantaneous changes in pH.

Gadolinum-gold core-shell nanocrystals: Potential contrast agents for molecular MRI with high T1 relaxivity

Gold-coated gadolinium nanocrystals have been synthesized and their relaxivities, R1 and R2, found to be 19.7 and 21.7 s−1 mM−1 respectively at a 9.4 T applied field. R1 is more than 3 times higher than commercial Gd3+ chelate contrast agents on a per Gd atom basis and over 3000 times higher on a per nanocrystal (molecule) basis. Furthermore, the R2/R1 ratio, 1.1, is near ideal for a T1 contrast agent. Colloids of the PVP coated Gd@Au nanocrystals are stable in solution at physiological pH for more than a week. The Au shell protects the Gd from reaction over even in low pH solution. These results indicate that Gd@Au is an exceptionally promising candidate for development as an MRI T1 contrast agent for molecular imaging.

Effect of original vegetation on nutrient loss patterns from Oxisol cropland in forests and adjacent savannas of Cameroon

Forest-savanna mosaic is widespread in tropical Africa mainly occurring on nutrient-poor Oxisols. Though sustainable agriculture is a major concern in this region, little is known about the effects of original vegetation (i.e., forest vs savanna) on nutrient losses from cropland. Hence, we evaluated basic cation losses and nutrient balance of Oxisol cropland cultivated over two years in the Cameroonian forest-savanna mosaic. Solute fluxes at 30-cm depth in maize croplands derived from forest (CRFR) and savanna (CRSV) were compared with those in adjacent forest (FR) and savanna (SV) ecosystems. Nutrient inputs by rainfall, outputs from solute leaching and cropland grain removal, and soil nutrient stocks measured at depths between 0 and 30 cm were investigated. The main anion present in FR soil solutions was NO3− (0.16–0.19 mmolc L−1), while it was present in negligible amounts in SV. The 2-year NO3− flux in CRFR (156 kg N ha−1) was double that in CRSV (78 kg N ha−1), leading to greater 2-year K+ leaching in CRFR (118 kg K ha−1) than in CRSV (37 kg K ha−1). The ratio of 2-year nutrient losses to total soil stocks was the greatest for Ca both in CRFR (5%) and CRSV (4%), while K loss also reached 5% in combination with lower solution pH in CRFR. In conclusion, cultivation of former forest land substantially increased NO3− leaching, resulting in depletion of both K and Ca; whereas, cultivation of former savanna results in mainly Ca depletion.