ΔpH Values Research Articles

Surface charge characteristics of Inceptisols ameliorated with biochar from young coconut waste

The colloidal surface of the soil contains an electric charge and various surface characteristics. The application of amelioration technology can increase the availability of nutrients and overcome contamination such as pesticides in the soils. This research aimed to study the surface charge characteristics of Inceptisols ameliorated with biochar from young coconut waste (YCW). The experiment was carried out using a completely randomized design with three replications each. The treatment was carried out in a pot with dose equivalent to biochar YCW: A = 0 (0.0g); B = 10 (2.5g); C = 20 (5.0g); D = 30 (7.5g), and (E) 40 t ha-1 (10g 500g-1 soil). The results showed amelioration technology with biochar from young coconut waste, at the application of 40 t ha-1 on Inceptisols, an increased soil surface charge through changes in chemical characteristics by increasing the pH (H2O), EC, CEC, and SOM. The reduction in transmittance in the H-O-H bending band of water and C=C alkene (aromatic) (from 88.95 to 88,83 %) and minerals (from 50.50 to 50.42 %), increased the adsorption capacity of Inceptisols. The relationship of surface charge with chemical properties of Inceptisols ameliorated with biochar from young coconut waste occurred at a correlation value of ΔpH with pH H2O > pH PZC > CEC > Mineral = SOM > EC > pH KCl.

Biophysical indicators of the mucous membrane of the oral cavity, the microcirculatory channel and the oral fluid in patients with lichen ruber planus

Annotation. The work aims to conduct a biophysical assessment of the charge state of the buccal epithelium cells (BEC), the microcirculatory channel of the oral mucosa and oral fluid in patients with the erosive-ulcerative form of lichen planus. The problem is relevant due to the increasing number of lichen planus patients, the uncertain etiology of the disease, and the ongoing struggle to find treatment solutions. 11 patients aged 50-60 years with lichen planus (erosive-ulcerative form) were examined. All patients underwent a study of the charge state of the buccal epithelium cells. Buccal cell samples were collected on an empty stomach after rinsing the oral cavity with water, applying a gentle swabbing technique. A spectrocolorimeter of type “Pulsar” was used to assess the condition of the microcapillary channel of the oral mucosa. In addition, in patients with lichen planus, the stability of the pH of the oral fluid (ΔpH) was evaluated as one of the indicators of the level of non-specific resistance in the body and the oral cavity in particular. Five 1ml samples of oral fluid were taken from each patient to calculate the value of ΔpH, where pH value was determined using an ionometer immediately after sampling. An average value of ΔрН and the confidence interval of deviations (ΔрН) from the average value were calculated, taking into account the Student coefficient for five measurements and a confidence probability of 0.95. The results obtained from biophysical studies show a significant decrease in all studied indicators. The percentage of mobile nuclei in patients with the erosive-ulcerative form of lichen planus of the oral mucosa is two times lower than in healthy people of the same age. At the same time, the plasmalemma and nuclei displacement amplitudes, as well as their ratio, were reduced compared to the norm, which indicates a decrease in their charge and deterioration of the physiological state of cells and the body as a whole. We found that individuals with lichen planus exhibit a decreased efficiency of functional reactions in the oral cavity tissues, which requires the development and implementation of effective treatment and prevention measures.

Terrestrial and aquatic ecotoxicity of iron ore tailings after the failure of VALE S.A mining dam in Brumadinho (Brazil)

This study consists of an ecotoxicological assessment related to one the most important environmental Brazilian disasters: the failure of an iron mining dam of the Vale S.A. in Brumadinho (Minas Gerais State, Brazil). Tailing samples (mixed with many other materials) were collected in three areas: (i) Zona Quente (n = 9) – close to the dam collapse; (ii) Parque das Cachoeiras (n = 3) – downstream of the Zona Quente; and (iii) Alberto Flores (n = 3), closer to Paraopeba river (an important tributary of one of the most important Brazilian watersheds). Acute ecotoxicological tests with Eisenia andrei and Daphnia similis and chronic reproduction tests with Folsomia candida and Chlorella vulgaris were performed. The bioassays with aquatic organisms were carried out with elutriates of the samples. Metal concentrations and physical, chemical and mineralogical properties of the samples were determined to support the interpretation of the ecotoxicological data. The increase of the particle density values (significantly correlated to an anomalous iron-enrichment and positive ΔpH values) seem to play a relevant role in the toxicity. As a result of iron-enrichment, the reduction of organic matter contents and water holding capacity were also crucial in the toxicity. Metal-enrichment factors showed abnormally high values, especially for Fe, Mn and Ni, while toxic metals concentrations exceeded the limits established by Brazilian law. Reproduction chronic effects were more intense than the acute ones, for both aquatic and soil organisms. Such extremely low reproduction levels of F. candida and C. vulgaris should be highlighted, since such organisms have a key ecological relevance. The samples collected in the Zona Quente were significantly different from the samples collected in downstream areas — fact that might be related to a high energy and turbulent flux of tailings in zones closer to dam, and the reduction of its energy in downstream areas.

The voltage sensor is responsible for ΔpH dependence in Hv1 channels

The dissipation of acute acid loads by the voltage-gated proton channel (Hv1) relies on regulating the channel's open probability by the voltage and the ΔpH across the membrane (ΔpH = pHex - pHin). Using monomeric Ciona-Hv1, we asked whether ΔpH-dependent gating is produced during the voltage sensor activation or permeation pathway opening. A leftward shift of the conductance-voltage (G-V) curve was produced at higher ΔpH values in the monomeric channel. Next, we measured the voltage sensor pH dependence in the absence of a functional permeation pathway by recording gating currents in the monomeric nonconducting D160N mutant. Increasing the ΔpH leftward shifted the gating charge-voltage (Q-V) curve, demonstrating that the ΔpH-dependent gating in Hv1 arises by modulating its voltage sensor. We fitted our data to a model that explicitly supposes the Hv1 voltage sensor free energy is a function of both the proton chemical and the electrical potential. The parameters obtained showed that around 60% of the free energy stored in the ΔpH is coupled to the Hv1 voltage sensor activation. Our results suggest that the molecular mechanism underlying the Hv1 ΔpH dependence is produced by protons, which alter the free-energy landscape around the voltage sensor domain. We propose that this alteration is produced by accessibility changes of the protons in the Hv1 voltage sensor during activation.

Effect of Cocultivation on Lactobacillus plantarum Strains Growth and Antagonistic Activity

The use of bacterial starters for the production of fermented foods has several advantages over traditional spontaneous fermentation, as it provides a rapid and controlled decrease of pH, improves the microbiological quality of the product, and prolongs the shelf-life. Fermented foods are typically produced using mixed cultures of lactic acid bacteria (LAB) due to the synergism between their constituent bacterial cultures. So, the compatibility of the LAB strains decides the efficacy of a multi-strain starter. The purpose of this study was to investigate the effect of the cocultivation of Lactobacillus plantarum strains on the growth, acidification, and antagonistic activity to determine suitable strain combinations for fermented vegetable production. Methods. The effect of cocultivation on growth characteristics of four L. plantarum strains was determined in MRS medium and cabbage-based medium with 2.5% NaCl. After 8 h of cultivation at 30°C and 37°C, the number of viable cells (CFU/ml) and the pH of the medium were determined. The antagonistic activity of monocultures of L. plantarum and their six compositions against opportunistic pathogenic microorganisms was determined by the method of delayed antagonism. Results. During growth in MRS broth at 30°C cocultivation of L. plantarum 47SM with L. plantarum 691T or L. plantarum 1047K strains led to enhanced rates of growth compared to the monocultures, suggesting some degree of symbiosis between these strains. Viable cell counts of L. plantarum 47SM, 1047K and 691T strains and ΔpH values of L. plantarum 952K, 1047K, and 691T strains were higher after 8 h growth in the cabbage-based medium at 30°C compared to MRS broth. Despite the intensive growth of L. plantarum monocultures in cabbage-based medium, a significant decrease of viable cell counts and ΔpH values during cocultivation at 30°C were found. Cocultivation did not affect the average size of the growth inhibition zones of most of the indicator strains used. However, growth inhibition zones of Shigella flexneri, Escherichia coli, and Proteus vulgaris decreased in some L. plantarum mixed cultures compared to monocultures. Thus, the growth inhibition zones of E. coli and S. flexneri by mixed culture L. plantarum 47 SM+1047K were significantly smaller compared to the growth inhibition zones of L. plantarum monocultures. Conclusions. Thus, based on the data obtained in present work, we can assume that some of these L. plantarum strains used in the work may be bactericinogenic. Although the four L. plantarum strains studied are compatible when cocultivated in a standard rich MRS medium, the results of cocultivation in a cabbage-based medium with 2.5% NaCl does not allow to recommend the use of these L. plantarum strains simultaneously in the starter for vegetable fermentation. Further investigation of bacteriocinogenic properties and mechanisms of growth inhibition under cocultivation in vegetable-like conditions are needed, which will allow combining of some of these L. plantarum strains with LAB strains of other species or genera to create multi-starters for vegetable fermentation.

Decomposing monthly declines in subsurface-water pH and aragonite saturation state from spring to autumn in the North Yellow Sea

The North Yellow Sea (NYS) is a western North Pacific marginal sea of major ecological and economic importance, where seasonal thermocline and subsurface cold water mass are well developed from spring to autumn. Earlier researchers have shown monthly/bimonthly declines of pH (ΔpH) and aragonite saturation state (ΔΩarag) in the NYS cold water mass. To quantify the biogeochemical processes controlling these variations, we applied a systematic decomposition methodology to ΔΩarag and ΔpH values, using the Redfield ratio and published data sets of NYS carbonate and ancillary parameters for 2011 and 2013. Results show that the contributions of the NYS cold water mass community respiration (ΔΩResp), calcification (ΔΩCalc) and temperature changes (ΔΩΔT) to the monthly ΔΩarag from spring to summer were 84 ± 9%, 30 ± 16%, and − 13 ± 10%, while the ΔΩResp, ΔΩΔT and contributions of CaCO3 dissolution (ΔΩDiss) to the bimonthly ΔΩarag from late summer to autumn were 103%, 1% and − 5%. Meanwhile, the contributions of the NYS cold water mass community respiration (ΔpHResp), temperature changes (ΔpHΔT) and calcification (ΔpHCalc) to the monthly ΔpH from spring to summer were 50 ± 23%, 39 ± 23%, and 13 ± 4%, while the ΔpHResp, ΔpHΔT and contributions of CaCO3 dissolution (ΔpHDiss) to the bimonthly ΔpH from late summer to autumn were 110%, − 5%, and − 5%. Our results suggest that the NYS cold water mass net calcification rate declines to nearly zero when Ωarag reaches a critical level of 1.5 − 1.6. Using a future scenario to predict the impacts of rising atmospheric CO2 levels on seasonal variations of Ωarag and pH values, we show that very low Ωarag values of < 1.5 may exist all year round in the NYS subsurface waters by the 2050 s, while aragonite undersaturated water (Ωarag <1) may appear in autumn months, causing great stress to its benthic faunal community.

Surface charge is a function of organic carbon content and mineralogical compositions of soil

A study of the distribution of the electric charges in the surface horizons of two highly weathered soils Fluvaquent and Haplaquept of West Bengal, India was made by direct measurement of adsorption of ions in the presence of varying concentration of electrolyte. The objective of this study was to evaluate charge properties of two highly weathered soil of India. The results show that pH 0 varies with soil according to the variation in organic carbon and sesquioxide/allophone content. Organic carbon strongly affects the variation of negative charge with pH, but sesquioxide/allophone is responsible for positive charge variation. Results used the difference between the soil pH values measured in 1M KCl and in water for estimating the point zero charge of the soil and ΔpH values estimating the net surface charge character. Surface charges is a function of organic carbon, clay content, composition of clay and amount of Fe, Al and there oxides.

Intermittent hypoxic training improves anaerobic performance in competitive swimmers when implemented into a direct competition mesocycle.

The main objective of this research was to evaluate the efficacy of intermittent hypoxic training (IHT) on anaerobic and aerobic capacity and swimming performance in well-trained swimmers. Sixteen male swimmers were randomly divided into a hypoxia (H) group (n = 8), which trained in a normobaric hypoxia environment, and a control (C) group (n = 8), which exercised under normoxic conditions. However, one participant left the study without explanation. During the experiment group H trained on land twice per week in simulated hypoxia (FiO2 = 15.5%, corresponding to 2,500 m a.s.l); however, they conducted swim training in normoxic conditions. Group C performed the same training program under normoxic conditions. The training program included four weekly microcyles, followed by three days of recovery. During practice sessions on land, the swimmers performed 30 second sprints on an arm-ergometer, alternating with two minute high intensity intervals on a lower limb cycle ergometer. The results showed that the training on land caused a significant (p<0.05) increase in absolute maximal workload (WRmax) by 7.4% in group H and by 3.2% in group C and relative values of VO2max by 6.9% in group H and 3.7% in group C. However, absolute values of VO2max were not significantly changed. Additionally, a significant (p<0.05) increase in mean power (Pmean) during the first (11.7%) and second (11.9%) Wingate tests was only observed in group H. The delta values of lactate concentration (ΔLA) after both Wingate tests were significantly (p<0.05) higher in comparison to baseline levels by 28.8% in group H. Opposite changes were observed in delta values of blood pH (ΔpH) after both Wingate tests in group H, with a significant decrease in values of ΔpH by 33.3%. The IHT caused a significant (p<0.05) improvement in 100m and 200m swimming performance, by 2.1% and 1.8%, respectively in group H. Training in normoxia (group C), resulted in a significant (p<0.05) improvement of swimming performance at 100m and 200m, by 1.1% and 0.8%, respectively. In conclusion, the most important finding of this study includes a significant improvement in anaerobic capacity and swimming performance after high-intensity IHT. However, this training protocol had no effect on absolute values of VO2max and hematological variables.

PH CHANGE IN ELECTROCHEMICAL OXIDATION OF IMIDACLOPRID PESTICIDE USING BORON-DOPED DIAMOND ELECTRODES

In this study, pH and ΔpH change in the electrochemical oxidation of imidacloprid (IMD) pesticide using boron-doped diamond (BDD) electrodes was investigated in the presence of Na2SO4 electrolyte. The process parameters were operated as imidacloprid concentration (40-200 mg/L), electrolyte concentration (2-10 g/L), current density (4-20 mA/cm2) and reaction temperature (20-60°C). pH and ΔpH values increased with increasing Na2SO4 concentration, current density, and reaction temperature, and decreasing the imidacloprid concentration at 120 min reaction time. The results of this study showed that the pH of the wastewater solution maintained the local pH discharge limits between 6 and 9 after the electrochemical oxidation.

Application of magnetic isothiouronium polyurethane sorbent for the removal of acidic and basic dyes from wastewater

Commercial polyurethane foam (PUF) was coupled with magnetite nanoparticles (MNPs) through isothiouronium groups (IT) to prepare a new porous sorbent (PUF@IT@MNPs) with improved ionic character and better sorption affinity towards ionic molecules. PUF@IT@MNPs was characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), thermal analysis (TGA), Brunauer-Emmett-Teller (BET) and FT-IR studies. PUF@IT@MNPs had an electrical conductivity (σ) value of 1.0 × 10−5 Ω−1m−1 and maximum ΔpH values of +0.3 and −3.5 at pH 1.4 and 9.7, pointing to the acidic character of the sorbent. FT-IR and TGA studies demonstrated that PUF@IT@MNPs contained different surface-active groups and had a composition of 40.90 wt % of Fe3O4. PUF@IT@MNPs had an improved stability in both acidic and alkaline solutions and high sorption efficiency for anionic (brilliant yellow, BY) and cationic (brilliant green, BG) dyes. The sorption capacities of PUF@IT@MNPs were 330, 328, 225 and 221 mg/g for I2, BY, BG, and MB. The average pore radius values of PUF@IT@MNPs were found to be 1.5 and 8.0 nm and the particle size was 21.4 nm. The sorption of BY was an exothermic process (ΔH = −15.51 kJ mol−1) while that of BG was endothermic (ΔH = 59.19 kJ mol−1).

A new fluorescence-based method to monitor the pH in the thylakoid lumen using GFP variants

The ΔpH-dependent/Tat pathway is unique for using only the proton motive force for driving proteins transport across the thylakoid membrane in chloroplasts. 9-aminoacridine fluorescence quenching is widely used to monitor the ΔpH developed across the thylakoid membrane in the light. However, this method suffers from limited sensitivity to low ΔpH values and to spurious fluorescence signals due to membrane binding. In order to develop a more sensitive method for monitoring the real pH of the thylakoid lumen without these problems we transformed Arabidopsis thaliana with a ratiometric pH-sensitive GFP variant (termed pHluorin) targeted to the lumen by the prOE17 transit peptide. Positive transgenic plants displayed localization of pHluorin in the chloroplast by confocal microscopy, and fractionation experiments revealed that it is in the lumen. The pHluorin signal was the strongest in very young plants and diminished as the plants matured. The pHluorin released from the lumen displayed the expected fluorescence intensity changes in response to pH titration. The fluorescence signal in isolated chloroplasts responded to illumination in a manner consistent with light-dependent lumen acidification. Future experiments will exploit the use of this new pH-indicating probe of the thylakoid lumen to examine the influence of the thylakoid ΔpH on ATP synthesis and protein transport.

Lateral heterogeneity of the proton potential along the thylakoid membranes of chloroplasts

This work is devoted to critical analysis and reexamination of the problem of lateral heterogeneity of the trans-thylakoid pH difference (ΔpH=pHout−pHin) in thylakoid membranes of chloroplasts. Correct measurements of ΔpH may be complicated by nonuniform partitioning of the protons pumped into the lumen of granal (stacked) and stroma-exposed thylakoids. We have compared results of ΔpH estimations in isolated bean chloroplasts by two different methods. One of the methods is based on the use of pH-sensitive spin-probes. Another approach relies on the analysis of pH-dependent post-illumination reduction of P700+ - oxidized reaction center of photosystem I (PSI). Both methods lead to virtually the same values of ΔpH, as measured in the state of photosynthetic control when the ATP synthase complexes are inactive (ΔpH~2.3–2.5 at pHout~8). Under the photophosphorylation conditions (metabolic state 3), ΔpH decreases due to the proton drain from the lumen to stroma via active ATP synthases (ΔpH~1–2 at pHout~8). In this state, ΔpH values derived from kinetic data are smaller than ΔpH measured with the pH-probing amines. Such a discrepancy can be explained by the coexistence of thylakoids with different pHin established in granal and stromal thylakoids. The kinetic method is equivalent to the use of a “local pH-meter”, which is sensitive to less significant decrease in pHin inside the stroma-exposed thylakoids. Otherwise, pH-indicating probes give information on pHin values averaged out at both granal and stromal thylakoids. Experimental results have been analyzed within the framework of our mathematical model developed for simulation of electron and proton transport processes in laterally heterogeneous thylakoids. The model provides a reasonable description of experimental data, supporting the notion that the long-range diffusion of protons within the lumen and obstructed diffusion of mobile electron carriers (PQH2 and Pc) influence the lateral profiles of pH along the thylakoid membranes. The model predicts significant alkalization of the inter-thylakoid gap and the establishment of nonuniform lateral profiles of ΔpH under the photophosphorylation conditions. These results are discussed in the context of the problem of energy coupling in laterally heterogeneous lamellar system of chloroplasts.

Difference in the pH values of hydromorphic soils in field and laboratory analyses

There are marked differences in the pH values determined in water suspension under laboratory conditions and in soil solution under field conditions in hydromorphic soils (gleysols and stagnosols). The value δpH = pHsusp–pHsol can be either positive or negative. Among the main factors that affect the value of δpH are the laboratory preparation of soil samples and the suspension effect. The sign of the pH effect (value of δpH) depends on the participation of humus, carbonate, and exchange bases in the formation of aggregates destructed in the laboratory. The value of δpH is negative in noncalcareous soils with low content of exchangeable bases and fulvate composition of humus and positive in calcareous soils or soils enriched with exchangeable bases and humate composition of humus. In cases of a significant δpH effect, the value of pHsusp cannot be regarded as an adequate measure of soil acidity.

Longitudinal meta-analysis of NIST pH Standard Reference Materials(®): a complement to pH key comparisons.

This meta-analysis assesses the long-term (up to 70years) within-laboratory variation of the NIST pH Standard Reference Material® (SRM) tetroxalate, phthalate, phosphate, borate, and carbonate buffers. Values of ΔpH(S), the difference between the certified pH value, pH(S), of each SRM issue and the mean of all pH(S) values for the given SRM at that Celsius temperature, t, are graphed as a function of the SRM issue and t. In most cases, |ΔpH(S)| < 0.004. Deviations from the nominal base:acid amount (mole) ratio of a buffer yield t-independent, constant shifts in ΔpH(S). The mean ΔpH(S) characterizes such deviations. The corresponding mole fraction of impurity in the conjugate buffer component is generally <0.3%. Changes in the equipment, personnel, materials, and methodology of the pH(S) measurement yield t-dependent variations. The standard deviation of ΔpH(S) characterizes such changes. Standard deviations of ΔpH(S) are generally 0.0015 or less. The results provide a long-term, single-institution complement to the time-specific, multi-institution results of pH key comparisons administered by the Consultative Committee for Metrology in Chemistryand Biology (CCQM).

Investigation of strength mis-match effect on elastic plastic fracture parameters in laser beam welded aluminium alloy joints using the finite element method

In this study, elastic plastic fracture toughness parameters of laser-welded 6013 aluminium alloy are investigated. For this purpose, compact tension specimens used in the experimental study are modelled using the finite element software. In the analyses, crack tip opening displacement ( δ5) and J-integral values are determined and crack tip opening displacement, δ5 and J-integral resistance curves (R-curves) are generated. Crack tip opening displacement, δ5 resistance curves are compared with those obtained from the experimental work, and J-resistance curves are compared with those obtained from formulation. Effect of weld strength undermatching on crack tip opening displacement, δ5 and J-resistance curves is discussed. δph values obtained by the plastic hinge method are compared with the crack tip opening displacement, δ5 values. Fracture toughness parameters obtained from the finite element analysis showed a good agreement with those obtained from the experimental work and formulation. It is observed that the resistance curves obtained using the crack tip opening displacement, δ5 and J-integral characterize the resistance of the material against crack growth in a similar manner, and strength undermatching decreases the fracture resistance. The relationship between δph and crack tip opening displacement, δ5 is nonlinear, and as crack tip opening displacement increases, crack tip opening displacement, δ5 becomes larger than δph.

Humus Characterization of Humid Tropical Forest, Tea Garden, and Field Crop Soils of West Bengal, India: Chemical, Potentiometric, and Spectroscopic Methods

Humic acids (HA) and fulvic acids (FA) were extracted from tropical humid forest, tea garden, and field crop soils, and their chemical, potentiometric, and spectrophotometric properties were measured. There was less HA than FA in the cultivated soils. The HAs contained more carbon (C) and nitrogen (N) and had greater C/H ratios but lower O (oxygen)/H (hydrogen) ratios than FAs. Cultivated soils had greater total acidity than the forest soil generally because of both —COOH and phenolic-OH. Molecular weights of HA an FA, estimated from intrinsic viscosities, revealed that cultivation had reasonably reduced the molecular weights. The difference in pH (ΔpH) values, corresponding to three-fourths and one-fourth of the pH at final inflexion point showed that they were polyprotic. The longer time required for stability of greater pH of HAs was related to greater degree of stable coiling. The (E4/E6), in general, revealed a greater amount of aliphatic moiety rather than aromatic moiety.

Chemical characterisation and source apportionment of PM2.5 and PM10 at rural, urban and traffic sites in Navarra (North of Spain)

PM10 and PM2.5 levels, concentrations of major components, trace elements, pH, conductivity and source apportionment were evaluated from samples collected during 2009 at three different locations (rural, urban and urban-traffic) in Navarra (North of Spain). Mean particulate matter concentrations were below the annual limit value for PM10 and annual target value for PM2.5 established by the European Directive 2008/50/EC and similar to those recorded at other locations in the North of Spain. The major components of PM10 in the three sampling stations were, by order of importance, OC + EC, NO3- and non-marine sulphate (nmSO42-), whereas the major components of PM2.5 were OC + EC, nmSO42- and NO3-. ΔpH values indicated that PM2.5 samples were more acidic than PM10 ones. The 90–96% of total trace elements contribution in PM2.5 and PM10 were described by P, Ti, Cr, Mn, Ni, Cu, Zn, Sr, Sn, Ba and Pb. Concentrations of those elements were lower than values obtained in Pamplona in 2002–2004 and similar to those found in other sub-urban and urban Spanish cities. PMF model identified 5 principle sources for PM10 and PM2.5 in Iturrama and Plaza de la Cruz (crustal, secondary sulphate, secondary nitrate, traffic and sea-salt aerosols) and 4 sources for PM10 in Bertiz (crustal, secondary sulphate, secondary nitrate and sea-salt).

Interpretation of experimental data based on the piecewise linear approximation measurement model

Methods for estimating the input signal of a measuring device are considered. Information about the device is contained in the measurement results of a set of known test signals and the measurements were obtained in natural or in computational experiments. A method is proposed for the approximation of the measurement model by means of a piecewise linear model that is consistent with the results of measurements and the method of evaluation of the input signal and its accuracy. An example is given of the solution of a problem of the interpretation of measurements based on the approximation of a model of the photosynthetic system, in which the measured parameters are the values of saturation ΔpH and the rate of ATP synthesis and the estimated parameters are the concentration of photosystem-2 and light intensity.

Spin-probes designed for measuring the intrathylakoid pH in chloroplasts

Nitroxide radicals are widely used as molecular probes in different fields of chemistry and biology. In this work, we describe pH-sensitive imidazoline- and imidazolidine-based nitroxides with p K values in the range 4.7–7.6 (2,2,3,4,5,5-hexamethylperhydroimidazol-1-oxyl, 4-amino-2,2,5,5-tetramethyl-2,5-dihydro-1 H-imidazol-1-oxyl, 4-dimethylamino-2,2-diethyl-5,5-dimethyl-2,5-dihydro-1 H-imidazol-1-oxyl, and 2,2-diethyl-5,5-dimethyl-4-pyrrolidyline-1-yl-2,5-dihydro-1 H-imidazol-1-oxyl), which allow the pH-monitoring inside chloroplasts. We have demonstrated that EPR spectra of these spin-probes localized in the thylakoid lumen markedly change with the light-induced acidification of the thylakoid lumen in chloroplasts. Comparing EPR spectrum parameters of intrathylakoid spin-probes with relevant calibrating curves, we could estimate steady-state values of lumen pH in established during illumination of chloroplasts with continuous light. For isolated bean ( Vicia faba) chloroplasts suspended in a medium with pH out = 7.8, we found that pH in ≈ 5.4–5.7 in the state of photosynthetic control, and pH in ≈ 5.7–6.0 under photophosphorylation conditions. Thus, ATP synthesis occurs at a moderate acidification of the thylakoid lumen, corresponding to transthylakoid pH difference ΔpH ≈ 1.8–2.1. These values of ΔpH are consistent with a point of view that under steady-state conditions the proton gradient ΔpH is the main contributor to the proton motive force driving the operation of ATP synthesis, provided that stoichiometric ratio H +/ATP is n ≥ 4–4.7.

Changes of chemical properties in an oxisol after clearing of native Cerrado vegetation for agricultural use in Vilhena, Rondonia State, Brazil

Native vegetation clearing in the Amazon Cerrado region for agricultural purposes may be modifying soil chemical characteristics. The extent of change depends on the management practices used. We evaluated changes in chemical properties of a clayey oxisol (dystrophic red yellow latosol) under no-tillage (NT) and conventional tillage (CT). Soil samples were taken randomly ( n = 5) in July 2004 at 0–5 cm, 5–10 cm, 10–20 cm and 20–30 cm depths at six treatments: Cerrado with native vegetation, CT cultivated with rice for 1 year (1CT) and 2 years (2CT), and NT cultivated with soybean for 1 year (1NT), 2 years (2NT) and 3 years (3NT) in each case after a 2-year period of rice under CT. Soil pH (CaCl 2, KCl and water), ΔpH, total acidity (H + + Al 3+), total organic carbon (TOC), available P, exchangeable K, Ca, Mg, potential cation exchange capacity (CEC) and base saturation (V) were determined. The highest pH values were determined in topsoil layers at the older NT adoption. Under Cerrado pH was lower than under cultivation at all depths due to absence of lime application. Generally, negative values of ΔpH were observed at all sites in all layers indicating predominant presence of negative charges in the soil. Although not statistically significant it seems that the amount of negative charges was higher in deeper layers. Total acidity displayed the highest values throughout the soil profile under Cerrado and low pH and low concentrations of exchangeable bases. Cultivated systems with fertilizer generated considerable increases of P, K, Ca, and Mg compared to Cerrado. Soil macronutrient content and base saturation under NT gradually increased throughout the profile with time. Highest CEC values were calculated for the 0–5 cm and 5–10 cm layers under Cerrado and NT systems. For the 0–5 cm layer CEC was lower at the CT system compared to the Cerrado and the oldest year under NT system. Alteration of TOC was more pronounced in the top 10 cm layer at all sites. The highest content was measured in the topsoil layer under Cerrado. Considering the future land use in Cerrado areas the NT system, if properly managed, appears to be the favourable management option of the existing croplands established after Cerrado clearing.