RESUMO

The presence of micropollutants, such as caffeine (CAF), has been detected throughout the world, since conventional treatment plants are not able to properly degrade them. CAF is a widely consumed stimulant, and has been demanding the development of efficient methodologies for its removal. Aiming at the agriculture waste valorization, a new hydrochar was developed based on chemical and thermal modification of peach stones (mod-PS) for CAF removal from water and from a synthetic mixture. The morphology, functional groups and surface electrical charge of the adsorbent were characterized by SEM, FTIR and zeta potential, respectively. Regarding CAF adsorption performance, the equilibrium time was reached at 480 min and the pseudo-second-order model presented the best fit for the experimental data. The maximum adsorption capacity was 68.39 mg g-1 (298 K) and the Langmuir model exhibited a better fit for the isothermal data. The thermodynamic properties confirmed that the process was exothermic, spontaneous and reversible. The main adsorption mechanisms were hydrogen bonds and π-interactions. The global removal efficiency was satisfactory in the synthetic mixture simulating real wastewater (67%). Therefore, the proposed new hydrochar has potential application as a low-cost adsorbent for CAF removal.

RESUMO

Triclosan (TCS) is widely used in the production of antibacterial products, being often found in wastewater. Therefore, this study developed new materials via soybean hulls (SBHF) and açaí seeds (AÇSF) functionalization with iron oxide nanoparticles to be applied in the TCS adsorption. The characterization confirmed the functionalization of the materials. The adsorption results indicated that the equilibrium of the process occurred after 480 and 960 min for SBHF and AÇSF, respectively. The maximum adsorptive capacity values were 158.35 and 155.09 mg g-1 for SBHF and AÇSF, respectively, at 318 K. The kinetic and isothermal data better fitted to the pseudo-second-order and Langmuir models. Thermodynamics indicated that the processes had an endothermic, spontaneous, and reversible character. The main adsorption mechanisms were H-bond and π-interactions. The pH and ionic strength studies indicated that the adsorption efficiency has not been reduced pronouncedly. The biosorbents reuse was effective for five cycles. In the synthetic mixture, the removal rate was satisfactory (92.53% and 57.02%, respectively for SBHF and AÇSF). These results demonstrate the biosorbents high potential for large-scale application.

Assuntos

RESUMO

Abstract Polyelectrolyte complexes (PECs) as drug delivery systems are widely explored since they are easily obtained by coacervation and biopolymers can be associated. However, particle distribution is a challenging critical parameter that has been infrequently focused. This work evaluated the effect of NaCl concentration on the physicochemical properties of PECs based on chitosan and hypromellose loaded with methotrexate. The particle size, zeta potential and polydispersity index (PdI) were determined by DLS, besides of drug entrapment efficiency (EE) and in vitro drug release profile determination. Particle size decreased while NaCl concentration rised, achieving a narrower size distribution of (345±79 nm) and PdI (0.285±0.067) with 200 mmol/L NaCl. The higher the NaCl concentration, the lower the zeta potential at acid pH. The EE was kept similar ((28.2±4.5) %) from 0 to 300 mmol/L NaCl, while 400 mmol/L NaCl impaired the drug entrapment. The addition of (200 and 300) mmol/L NaCl did not affect the drug release profile, but it was faster with (100 or 400) mmol/L. In conclusion, the addition of 200 mmol/L NaCl reduced particle size and PdI with no changes in the EE and drug release. Therefore, the ionic strength plays an important role on PECs development.

RESUMO

In this study, a background electrolyte capable to separate and quantify inorganic cations in high ionic strength samples by UV-absorption indirect detection was designed. In this regard, the four most abundant monovalent and divalent cations in earth crust (K+, Na+, Ca+2, Mg+2) were selected as model compounds. A group of small carboxylic acids and, several toluidines and pyridines were evaluated as mild strength complexing agents and chromophoric probes, respectively. The optimized background electrolyte was composed of 200 mM 2,4,6-trimethylpyridine as the chromophoric probe, 250 mM lactic acid as the weak complexing agent and pH buffering reagent (adjusted to pH 4.5), and 5% v/v methanol as organic solvent modifier. Based on a minimum number of components, it provided outstanding separation performance in less than 4 min in a wide linear dynamic range (10 - 2500 µg·mL-1). Performances were contrasted against a reference method based on conductometric detection. Furthermore, studies of separation efficiency and peak shape were carried out at different analyte concentrations in high electric conductivity solutions. The herein developed method demonstrated exceptional features in terms of limits of detection (~10 µg·mL-1), resolution, speed of analysis, sensitivity and peak capacity in high electric conductivity samples. Moreover, the method was successfully applied to high ionic strength samples such as rock digest, sea water, soy sauce and isotonic drinks.

Assuntos

RESUMO

The effect of pH and ionic strength (µ) on the extraction capacity of myofibrillar proteins from Jumbo squid mantle muscle along with the addition of isoascorbic acid (IA) in its gel-forming ability (GFA) were evaluated. The results indicate that µ had a greater impact (p < 0.05) than pH on the extraction of muscle myofibrillar proteins. The effectiveness of IA, as the precursor of dehydro-isoascorbic acid (DIA), on the oxidation of sulfhydryl groups (-SH) to disulfide bonds (-SS-) of extracted proteins at 0.6 µ was also evaluated. During the sol-gel transition the -SH groups initially present in the protein system decreased (p < 0.05) due to the combined effect of heat treatment (90 °C/30 min) and the addition of IA; however, the oxidative effect of IA reduced (p < 0.05) the GFA of Jumbo squid muscle proteins. Results also indicated that NaCl at 2.8% rather than at 2.5% during gel preparation significantly (p < 0.05) improves its GFA.

Assuntos

RESUMO

In this work, we describe a hydrodynamic flow-focusing microfluidic process to produce stealth cationic liposomes (SCL), stabilized with poly(ethylene glycol) (PEG), with uniform and reproducible features. Through cryogenic transmission electron microscopy (cryo-TEM) characterization and real-time monitoring, we verified the formation of multi-sized lipid self-aggregates, which can be attributed to micelles formation. These structures tend to undergo deposition within the PDMS/glass microchannels through intermolecular interactions with the glass walls, hindering not only the process reproducibility but also the final biological application of the SCL products. In view of this, we propose the modulation of ionic strength of the side streams aiming to ionically shield the glass surface, decrease the intermolecular interactions of the lipid polar heads, and, essentially, to promote the bilayer-driven self-assembly of SCL with 1% of DSPE-PEG2000 lipid. Herein, we applied phosphate-buffered saline (PBS) from 10 to 50 mM concentration as side streams, and evaluated its effects on SCL final physicochemical properties in terms of size distribution, mean diameter, zeta potential and polydispersity index (PDI). We present evidences indicating that the ionic strength can be used as a microfluidic process parameter to modulate the lipids self-assembly kinetics whilst preventing micelles formation. Finally, the proposed diffusion-based microfluidic system with high ionic strength enables the formation of monodisperse (PDI < 0.2) SCL of around 140 nm with monomodal size distributions and enhanced properties when compared to usual bulk mixing.

Assuntos

RESUMO

In the present work, we analyzed how external factors can modulate the efficiency of epigallocatechin­3­O­gallate (EGCG) inhibition of a membrane-bound isoform of the acetylcholinesterase. Increasing the ionic strength but not the osmolarity of the bulk medium proved to be an important factor. In addition, we verified a clear correlation between the inhibitory activity with the order degree of the membranes by using cholesterol-partially depleted red blood cell ghosts. These two factors i.e. high salt concentration in the bulk medium and less viscous membranes, allow a deeper insertion of the EGCG into the lipid bilayer, thus leading to a greater inhibition of AChE. As a corollary, we propose that any treatment or process that leads to a slight decrease in cholesterol content in the membranes can efficiently enhance the inhibitory activity of EGCG, which can have important consequences in all the pathologies where the inhibition of AChE is recommended.

Assuntos

RESUMO

Zein, a protein extracted from maize, can be employed to easily produce nanoscale particles suitable for use as carrier systems. This review investigates the main methods for obtaining zein nanoparticles, as well as the problems and options available in the development of stable colloidal suspensions. Considerable gaps were identified in the literature concerning this topic, with studies being unclear about the factors that affect the stability of zein particles. In the vast majority of cases, no data are presented in relation to the stability of the formulations over time. It could be concluded that in order to produce a high quality system, detailed evaluation is required, considering factors including the zein concentration, pH, ionic strength, thermal treatment of the protein prior to preparation of the nanoparticles, strategies employing other materials as coatings, and the storage conditions. It is extremely important that these aspects should be considered during product development, prior to commercial-scale manufacture.

RESUMO

In this work we study the effect of solution ionic strength on the structural evolution of amidated amyloid beta peptide Aß (1-40) oligomers at the early stages of fibril formation. By light scattering, we follow the time evolution of the structure and short-time dynamics of peptide structures at low ionic strengths. Our results allow identifying initial oligomer structures as the effective building blocks in the amyloid fibrils formation and indicate that the oligomers growth pathway, from compact structures to flexible chain-like structures, becomes faster as the solution ionic strength is increased. Furthermore, we find no evidence of structural branching what suggests that elongation of amyloid fibrils is dominated by linear association. To describe our results we adapt a phenomenological model based on population balance equations and linear polymer growth, where the parameters required are obtained from the experiments. Model calculations are in good agreement with experimentally-obtained estimates for the radius of gyration of Aß (1-40) oligomers, thus further supporting our findings. Additionally, we introduce a model for the effective interaction among initial Aß structures that captures the dependence of the effective association rates on solution ionic strength.

Assuntos

RESUMO

ABSTRACT The present study evaluated the purification of inulinase by changing the ionic strength of the medium by addition of NaCl and CaCl2 followed by precipitation with n-propyl alcohol or iso-propyl alcohol. The effects of the concentration of alcohols and the rate of addition of alcohols in the crude extract on the purification yield and purification factor were evaluated. Precipitation caused an activation of enzyme and allowed purification factors up to 2.4-fold for both alcohols. The purification factor was affected positively by the modification of the ionic strength of the medium to 0.5 mol.L-1 NaCl before precipitation with the alcohol (n-propyl or iso-propyl). A purification factor of 4.8-fold and an enzyme yield of 78.1 % could be achieved by the addition of 0.5 mol.L-1 of NaCl to the crude extract, followed by the precipitation with 50 % (v/v) of n-propyl alcohol, added at a flow rate of 19.9 mL/min.

Assuntos

RESUMO

Release of low-molecular aromatic hydrocarbons (HC) into natural waters brings severe consequences to our environment. Unfortunately very limited information is available regarding the treatment of these pollutants. This work evaluated the use of brown, green and red macroalgae biomass as biosorbents of benzene and toluene, two of the most soluble HC. Raw seaweed biomasses were completely characterized, then evaluated under different temperatures and ionic strengths to assess their potential as biosorbents and to elucidate the biosorption mechanisms involved. Brown macroalgae registered the highest removal capacities for benzene and toluene (112 and 28 mg·g-1, respectively), and these were not affected at ionic strength < 0.6 M. Langmuir and Sips isotherm equations well described biosorption data, and the pseudo-second order model provided the best fit to the kinetics rate. Hydrocarbons are adsorbed onto the diverse chemical components of the cell wall by London forces and hydrophobic interactions.

Assuntos

RESUMO

Nowadays, petrochemical operations involve risks to the environment and one of the biggest is oil spills. Low molecular aromatics like benzene, toluene, and naphthalene dissolve in water, and because of their toxicological characteristics, these produce severe consequences to the environment. The oil spill cleanup strategies are mainly designed to deal with the heavy fractions accumulated on the water surface. Unfortunately, very limited information is available regarding the treatment of dissolved fractions.A commercial (Filtrasorb 400) and modified activated carbons were evaluated to remove benzene, toluene, and naphthalene from water, which are the most soluble aromatic hydrocarbons, at different ionic strengths (I) and temperatures (0-0.76 M and 4-25 °C, respectively). This allowed simulating the conditions of fresh and saline waters when assessing the performance of these adsorbents. It was found that the hydrocarbons adsorption affinity increased 12 % at a I of 0.5 M, due to the less negative charge of the adsorbent, while at a high I (≃0.76 M) in a synthetic seawater, the adsorption capacity decreased 21 % that was attributed to the adsorbent's pores occlusion by water clusters. Approximately, 40 h were needed to reach equilibrium; however, the maximum adsorption rate occurred within the first hour in all the cases. Moreover, the hydrocarbons adsorption and desorption capacities increased when the temperature augmented from 4 to 25 °C. On the other hand, thermally and chemically modified materials showed that the interactions between adsorbent-contaminant increased with the basification degree of the adsorbent surface.

Assuntos

RESUMO

This study analyses venom from the elapid krait snake Bungarus sindanus, which contains a high level of acetylcholinesterase (AChE) activity. The enzyme showed optimum activity at alkaline pH (8.5) and 45ºC. Krait venom AChE was inhibited by substrate. Inhibition was significantly reduced by using a high ionic strength buffer; low ionic strength buffer (10 mM PO4 pH 7.5) inhibited the enzyme by 1. 5mM AcSCh, while high ionic strength buffer (62 mM PO4 pH 7.5) inhibited it by 1 mM AcSCh. Venom acetylcholinesterase was also found to be thermally stable at 45ºC; it only lost 5% of its activity after incubation at 45ºC for 40 minutes. The Michaelis-Menten constant (Km) for acetylthiocholine iodide hydrolysis was found to be 0.068 mM. Krait venom acetylcholinesterase was also inhibited by ZnCl2, CdCl2, and HgCl2 in a concentrationdependent manner. Due to the elevated levels of AChE with high catalytic activity and because it is more stable than any other sources, Bungarus sindanus venom is highly valuable for biochemical studies of this enzyme.(AU)

Assuntos

RESUMO

This study analyses venom from the elapid krait snake Bungarus sindanus, which contains a high level of acetylcholinesterase (AChE) activity. The enzyme showed optimum activity at alkaline pH (8.5) and 45ºC. Krait venom AChE was inhibited by substrate. Inhibition was significantly reduced by using a high ionic strength buffer; low ionic strength buffer (10 mM PO4 pH 7.5) inhibited the enzyme by 1. 5mM AcSCh, while high ionic strength buffer (62 mM PO4 pH 7.5) inhibited it by 1 mM AcSCh. Venom acetylcholinesterase was also found to be thermally stable at 45ºC; it only lost 5% of its activity after incubation at 45ºC for 40 minutes. The Michaelis-Menten constant (Km) for acetylthiocholine iodide hydrolysis was found to be 0.068 mM. Krait venom acetylcholinesterase was also inhibited by ZnCl2, CdCl2, and HgCl2 in a concentrationdependent manner. Due to the elevated levels of AChE with high catalytic activity and because it is more stable than any other sources, Bungarus sindanus venom is highly valuable for biochemical studies of this enzyme.(AU)

Assuntos

RESUMO

The effects of pH and ionic strength (I) on Ni adsorption in variable charge soils were evaluated by laboratory batch experiments. Experimental results fitted the Langmuir model. Maximum adsorption (Ads max) ranged from 260-2818 mg kg-1 (topsoil) to 532-1541 mg kg-1 (subsoil). Nickel affinity (K L) was higher in the subsoil samples (0.022-0.236 L kg-1) than in topsoil (0.003-0.049 L kg-1). Adsorption envelopes showed sharp increase in Ni adsorption (20-90 percent) in the 4.0-6.0 pH range. Nickel adsorption was affected by I and specific adsorption predominated in the 3.0-5.0 pH range, while above pH 5.0, it was adsorbed by electrostatic mechanisms. Negative values of free energy variation (ΔG) and the separation factor K R<1 indicated that Ni adsorption reaction was favorable and occurred spontaneously, especially when pH increase. Chemical and mineralogical soil attributes should be considered as criteria for selecting the areas for disposal of residues containing Ni to minimize the impact on the environment.

RESUMO

Adsorption processes of heavy metals in soils have been more extensively studied than desorption, in spite of this latter process being related to nutrient bioavailability in the soil solution. Copper desorption from surface (0-0.2 m) and subsurface (1.0 - 1.2 m) samples of an Anionic Acrudox was studied at two pH values (4.5 and 7.5). Soil samples were incubated with Cu rates varying from 0 to 400 mg kg-1, during 4 and 12 weeks, in the presence of CaCl2 as support electrolyte at concentrations of 0.01 and 0.001 mol L-1. Complete soil adsorption of added Cu was observed at pH 7.5 in all incubation periods, indicating that a 24h-shaking period was enough to reach equilibrium and maximum adsorption. Copper adsorption varied with the incubation period and was much lower at pH 4.5 than at pH 7.5, after the 24 hour-incubation period. After 4 and 12 weeks, Cu adsorption values were higher and similar for all soil samples, irrespective of pH or depth of sampling. The effect of the incubation period on soil Cu adsorption surpassed the pH effect for all Cu rates. The hysteresis was expressive, suggesting that Cu enhances high-energy bonds with the soil colloids. Calcium chloride was not efficient in promoting native soil Cu desorption in the studied concentrations.

A adsorção de metais pesados aos solos é mais estudada do que sua dessorção. No entanto, o processo de dessorção está diretamente relacionado à disponibilidade dos elementos às plantas. A dessorção de cobre em amostras superficiais (0-0,2 m) e subsuperficiais (1,0-1,2 m) de um Latossolo Vermelho acriférrico foi estudada em dois valores de pH (4,5 e 7,5). Foram adicionados até 400 mg kg-1 de Cu em amostras incubadas por 4 e 12 semanas, tendo o CaCl2 como eletrólito suporte nas concentrações de 0,01 e 0,001 mol L-1. No pH mais elevado (7,5), em todos os períodos de incubação, as amostras adsorveram praticamente todo o cobre adicionado, indicando que o tempo de 24 h de agitação para se atingir o equilíbrio foi suficiente para atingir a adsorção máxima. A adsorção de Cu variou com o tempo de incubação do elemento com o solo. No pH mais baixo (4,5), a adsorção foi bem menor após 24 h de incubação. Após 4 e 12 semanas, as adsorções foram elevadas e semelhantes para todas as amostras, independentemente da profundidade e do pH. Para todas as doses estudadas, o efeito do tempo de incubação na adsorção de cobre pelo solo sobrepujou o efeito do pH. O fenômeno de histerese foi expressivo, sugerindo que o Cu forma ligações de alta energia com os colóides do solo. O cloreto de cálcio não foi eficiente para dessorver cobre nativo do solo.

RESUMO

Adsorption processes of heavy metals in soils have been more extensively studied than desorption, in spite of this latter process being related to nutrient bioavailability in the soil solution. Copper desorption from surface (0-0.2 m) and subsurface (1.0 - 1.2 m) samples of an Anionic Acrudox was studied at two pH values (4.5 and 7.5). Soil samples were incubated with Cu rates varying from 0 to 400 mg kg-1, during 4 and 12 weeks, in the presence of CaCl2 as support electrolyte at concentrations of 0.01 and 0.001 mol L-1. Complete soil adsorption of added Cu was observed at pH 7.5 in all incubation periods, indicating that a 24h-shaking period was enough to reach equilibrium and maximum adsorption. Copper adsorption varied with the incubation period and was much lower at pH 4.5 than at pH 7.5, after the 24 hour-incubation period. After 4 and 12 weeks, Cu adsorption values were higher and similar for all soil samples, irrespective of pH or depth of sampling. The effect of the incubation period on soil Cu adsorption surpassed the pH effect for all Cu rates. The hysteresis was expressive, suggesting that Cu enhances high-energy bonds with the soil colloids. Calcium chloride was not efficient in promoting native soil Cu desorption in the studied concentrations.

A adsorção de metais pesados aos solos é mais estudada do que sua dessorção. No entanto, o processo de dessorção está diretamente relacionado à disponibilidade dos elementos às plantas. A dessorção de cobre em amostras superficiais (0-0,2 m) e subsuperficiais (1,0-1,2 m) de um Latossolo Vermelho acriférrico foi estudada em dois valores de pH (4,5 e 7,5). Foram adicionados até 400 mg kg-1 de Cu em amostras incubadas por 4 e 12 semanas, tendo o CaCl2 como eletrólito suporte nas concentrações de 0,01 e 0,001 mol L-1. No pH mais elevado (7,5), em todos os períodos de incubação, as amostras adsorveram praticamente todo o cobre adicionado, indicando que o tempo de 24 h de agitação para se atingir o equilíbrio foi suficiente para atingir a adsorção máxima. A adsorção de Cu variou com o tempo de incubação do elemento com o solo. No pH mais baixo (4,5), a adsorção foi bem menor após 24 h de incubação. Após 4 e 12 semanas, as adsorções foram elevadas e semelhantes para todas as amostras, independentemente da profundidade e do pH. Para todas as doses estudadas, o efeito do tempo de incubação na adsorção de cobre pelo solo sobrepujou o efeito do pH. O fenômeno de histerese foi expressivo, sugerindo que o Cu forma ligações de alta energia com os colóides do solo. O cloreto de cálcio não foi eficiente para dessorver cobre nativo do solo.

RESUMO

Concentration and identity of cations and anions in the soil solution may affect soil P reactions and thus P availability. The magnitude of these reactions was evaluated in this research after application of various salts to a highly weathered low pH soil. Chloride, nitrate, and sulfate salts of Na, NH4, K, Ca, Mg, Sr, or Cu were added to the soil after addition of 360mg P/kg trying to simulate ion concentrations around granules of fertilizers in the soil. Thirty days later, P was determined in the soil solution (Pli) and on the solid phase (Psi). The soil samples of some treatments were leached with water and three days later a new soil solution was displaced. Separate addition of all salts increased Pli, except NaCl at the lowest rate. The increase of Pli was highly associatcd with amount of native cations displaced to the soil solution by the applied salts. Salt solubility, concentration, and sometimes identity of cation and anion also influenced Pli. Some salts decreased Psi, but this was not correlated with any soil property measured. The effects caused by salts on Pli and Psi disappeared after leaching the soil samples.

A concentração eletrolítica e o tipo de cations e anions da solução do solo podem afetar as reações do fósforo com possíveis reflexos na disponibilidade de P aos vegetais. Nessa pesquisa quantificou-se o efeito de vários sais nos valores das determinações analíticas que afetam a disponibilidade de fósforo. Sais de nitrato, cloreto e sulfato foram aplicados a amostras de um alfisol ácido após a aplicação de 360mg P/kg, simulando concentrações que ocorrem no solo ao redor de grânulos de fertilizantes. Fósforo lábil (Psi) e P na solução do solo (Pli) foram determinados após 30 dias de incubação, antes e depois de percolar água pelo solo. Todos os sais aumentaram a concentração de P na solução do solo, exceto a menor dose de NaCl. O aumento do Pli foi correlacionado com a quantidade de cations originalmente no solo deslocados para a solução do solo. Solubilidade, concentração, e a espécie dos cations e anions aplicados também exerceram efeito no Pli. Alguns sais diminuíram o Psi porém esse decréscimo não se correlacionou com nenhuma determinação efetuada. A percolação de água eliminou os efeitos ocasionados pelos sais nos valores de fósforo.

RESUMO

Concentration and identity of cations and anions in the soil solution may affect soil P reactions and thus P availability. The magnitude of these reactions was evaluated in this research after application of various salts to a highly weathered low pH soil. Chloride, nitrate, and sulfate salts of Na, NH4, K, Ca, Mg, Sr, or Cu were added to the soil after addition of 360mg P/kg trying to simulate ion concentrations around granules of fertilizers in the soil. Thirty days later, P was determined in the soil solution (Pli) and on the solid phase (Psi). The soil samples of some treatments were leached with water and three days later a new soil solution was displaced. Separate addition of all salts increased Pli, except NaCl at the lowest rate. The increase of Pli was highly associatcd with amount of native cations displaced to the soil solution by the applied salts. Salt solubility, concentration, and sometimes identity of cation and anion also influenced Pli. Some salts decreased Psi, but this was not correlated with any soil property measured. The effects caused by salts on Pli and Psi disappeared after leaching the soil samples.

A concentração eletrolítica e o tipo de cations e anions da solução do solo podem afetar as reações do fósforo com possíveis reflexos na disponibilidade de P aos vegetais. Nessa pesquisa quantificou-se o efeito de vários sais nos valores das determinações analíticas que afetam a disponibilidade de fósforo. Sais de nitrato, cloreto e sulfato foram aplicados a amostras de um alfisol ácido após a aplicação de 360mg P/kg, simulando concentrações que ocorrem no solo ao redor de grânulos de fertilizantes. Fósforo lábil (Psi) e P na solução do solo (Pli) foram determinados após 30 dias de incubação, antes e depois de percolar água pelo solo. Todos os sais aumentaram a concentração de P na solução do solo, exceto a menor dose de NaCl. O aumento do Pli foi correlacionado com a quantidade de cations originalmente no solo deslocados para a solução do solo. Solubilidade, concentração, e a espécie dos cations e anions aplicados também exerceram efeito no Pli. Alguns sais diminuíram o Psi porém esse decréscimo não se correlacionou com nenhuma determinação efetuada. A percolação de água eliminou os efeitos ocasionados pelos sais nos valores de fósforo.

RESUMO

Concentration and identity of cations and anions in the soil solution may affect soil P reactions and thus P availability. The magnitude of these reactions was evaluated in this research after application of various salts to a highly weathered low pH soil. Chloride, nitrate, and sulfate salts of Na, NH4, K, Ca, Mg, Sr, or Cu were added to the soil after addition of 360mg P/kg trying to simulate ion concentrations around granules of fertilizers in the soil. Thirty days later, P was determined in the soil solution (Pli) and on the solid phase (Psi). The soil samples of some treatments were leached with water and three days later a new soil solution was displaced. Separate addition of all salts increased Pli, except NaCl at the lowest rate. The increase of Pli was highly associatcd with amount of native cations displaced to the soil solution by the applied salts. Salt solubility, concentration, and sometimes identity of cation and anion also influenced Pli. Some salts decreased Psi, but this was not correlated with any soil property measured. The effects caused by salts on Pli and Psi disappeared after leaching the soil samples.

A concentração eletrolítica e o tipo de cations e anions da solução do solo podem afetar as reações do fósforo com possíveis reflexos na disponibilidade de P aos vegetais. Nessa pesquisa quantificou-se o efeito de vários sais nos valores das determinações analíticas que afetam a disponibilidade de fósforo. Sais de nitrato, cloreto e sulfato foram aplicados a amostras de um alfisol ácido após a aplicação de 360mg P/kg, simulando concentrações que ocorrem no solo ao redor de grânulos de fertilizantes. Fósforo lábil (Psi) e P na solução do solo (Pli) foram determinados após 30 dias de incubação, antes e depois de percolar água pelo solo. Todos os sais aumentaram a concentração de P na solução do solo, exceto a menor dose de NaCl. O aumento do Pli foi correlacionado com a quantidade de cations originalmente no solo deslocados para a solução do solo. Solubilidade, concentração, e a espécie dos cations e anions aplicados também exerceram efeito no Pli. Alguns sais diminuíram o Psi porém esse decréscimo não se correlacionou com nenhuma determinação efetuada. A percolação de água eliminou os efeitos ocasionados pelos sais nos valores de fósforo.