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1.
The adsorption behaviour of uranyl onto seven different samples of quartz was studied in batch experiments. Sea-sand (0.1–0.3 mm),
Fil-Pro 12/20 (1–2 mm) and five Min-U-Sil samples with smaller particle sizes (5, 10, 15, 30 and 40 μm) were used. The uptake
curves show “pH adsorption edges” in the range of pH 4–5. A good agreement of the new data with literature data was found
when plotting surface-normalised distribution coefficients versus pH. Differences in the adsorption behaviour for pre-treated
and untreated sea-sand samples were detectable resulting in a shift of the pH edge to higher pH values after treatment. A
literature surface complexation model was applied for blind predictions of the experimental results. The simulations described
the experimental observations quite well for the Min-U-Sil samples. For the two coarser quartz samples, the calculated over-predictions
were explained by the larger-than-expected measured specific surface area and measurable amounts of associated minerals, for
Fil-Pro 12/20 and sea-sand, respectively. Dissolution of the samples was studied as a function of pH. After 5 days, the measured
Si concentrations were all higher than equilibrium quartz solubilities, but lower than those of amorphous silica. With increasing
pH, dissolved silica increased. This strongly suggests that formation of dissolved uranyl–silicato complexes have to be considered
based on measured silica concentrations. 相似文献
2.
The charged sites on soil particles are important for the retention/adsorption of metals. Metallic counterions can neutralize
the intrinsic charges on the surfaces of soil particles by forming complexes. In this study, efforts have been made to determine
the effect of surface potential, pH, and ionic strength on the adsorption of four metal ions, hexavalent chromium Cr(VI),
trivalent chromium Cr(III), nickel Ni(II) and cadmium Cd(II), in glacial till soil. Batch tests were performed to determine
the effect of pH (2–12) and ionic strength (0.001–0.1 M KCl) on zeta potential of the glacial till soil. The point of zero
charge (pH
PZC
) of glacial till was found to be 7.0±2.5. Surface charge experiments revealed the high buffering capacity of the glacial
till. Batch adsorption experiments were conducted at natural pH (8.2) using various concentrations of selected metals. The
adsorption data was described by the Freundlich adsorption model. Overall glacial till shows lower adsorption affinity to
Cr(VI) as compared to cationic metals, Cr(III), Ni(II) and Cd(II). 相似文献
3.
This study examined the interaction between Cr(VI) and a Fe-rich soil in the presence of low-molecular-weight organic acids
as a function of pH. Oxalic and tartaric acids were chosen since they existed in soils commonly. Batch experiments showed
that adsorption of Cr(VI) by the soil within the pH range examined was inhibited in the presence of oxalic acid, which was
more pronounced when the initial ratio of [oxalic acid]/[Cr(VI)] was raised from 1:1 to 2:1. With the addition of tartaric
acid, concentration of Cr(VI) in equilibrium solutions was far less than that of single adsorbate system across the pH wide
(2.5–5.5), which was noticeable especially at low pH. The results were attributed to Cr(VI) adsorption and, particularly,
the soil surface catalyzed reduction of Cr(VI) to Cr(III) by tartaric acid. The data reported in this paper suggested that
the mobility, the bioavailability, and the toxicity of Cr(VI) in soil environments might be greatly affected by pH, the presence
and nature of low-weight-molecular organic acids (oxalic and tartaric acids). 相似文献
4.
Si adsorption onto Bacillus subtilis and Fe and Al oxide coated cells of B. subtilis was measured both as a function of pH and of bacterial concentration in suspension in order to gain insight into the mechanism of association between silica and silicate precipitates and bacterial cell walls. All experiments were conducted in undersaturated solutions with respect to silicate mineral phases in order to isolate the important adsorption reactions from precipitation kinetics effects of bacterial surfaces. The experimental results indicate that there is little association between aqueous Si and the bacterial surface, even under low pH conditions where most of the organic acid functional groups that are present on the bacterial surface are fully protonated and neutrally charged. Conversely, Fe and Al oxide coated bacteria, and Fe oxide precipitates only, all bind significant concentrations of aqueous Si over a wide range of pH conditions. Our results are consistent with those of Konhauser et al. [Geology 21 (1993) 1103; Environ. Microbiol. 60 (1994) 49] and Konhauser and Urrutia [Chem. Geol. 161 (1999) 399] in that they suggest that the association between silicate minerals and bacterial surfaces is not caused by direct Si–bacteria interactions. Rather, the association is most likely caused by the adsorption of Si onto Fe and Al oxides which are electrostatically bound to the bacterial surface. Therefore, the role of bacteria in silica and silicate mineralization is to concentrate Fe and Al through adsorption and/or precipitation reactions. Bacteria serve as bases, or perhaps templates, for Fe and Al oxide precipitation, and it is these oxide mineral surfaces (and perhaps other metal oxide surfaces as well) that are reactive with aqueous Si, forming surface complexes that are the precursors to the formation of silica and silicate minerals. 相似文献
5.
Aluminum organic coprecipitates play important roles in the transport of oxyanions in soil environment.A new polynuclear aluminum organomineral precipitate(Al13-oxalate precipitate) was prepared to investigate the adsorption behavior of arsenate and phosphate on noncrystalline aluminum precipitates.Important thermodynamic parameters for adsorption reaction were evaluated using macroscopic adsorption data and equations.The result showed that,the adsorption reaction basically is a diffusion process.FTIR spectroscopic studies have provided evidence for the formation of two different types of complexes in substrate,protonated bidentate and deprotonated bidentate complexes at pH 4 and pH≥6,respectively.The classic competitive adsorption and XPS studies both indicated that phosphate has stronger chemical interaction with substrate than arsenate.The findings of XPS studies revealed that the precipitate substrate can act as Lewis acid when adsorbing oxyanions. 相似文献
6.
The adsorption behavior of chromate on two variable charge soils (Oxisol and Ultisol) was investigated through batch experiments
at different ionic strengths and pH values. The adsorption of chromate on the variable charge soils was found to be strongly
dependent on the pH of the soil solutions. A characteristic pH was observed, which corresponds to the intersection of the
chromate adsorption—pH curves at different ionic strengths. The characteristic pH values are 5.50 for Oxisol and 5.04 for
Ultisol, close to the point of zero salt effect (PZSE) of these soils. The zeta potentials measured for these soils provide
the evidences to support the interpretation of the effect of ionic strength on the adsorption of chromate on these variable
charge soils. The adsorption behavior of chromate was interpreted by a schematic representation of chromate distribution at
increasing ionic strength. The chromate desorption–pH curves were also found to intersect at pH of 5.15 and 4.89 for the Oxisol
and Ultisol, respectively. It is considered that chromate adsorption by the variable charge soils was mainly determined by
the electrostatic potential on the adsorption plane, which was controlled by the ionic strength of the soil solutions. 相似文献
7.
In order to better understand the influence and mechanism of soil-derived humic acid (SHA) on adsorption of P onto particles in soils, the amounts of PO 4 adsorbed by synthetic goethite (α-FeOOH) were determined at different concentrations of SHA, pH, ionic strength and order of addition of adsorbents. Addition of SHA can significantly reduce the amount of PO 4 adsorption as much as 27.8%. Both generated electrostatic field and competition for adsorption sites were responsible for the mechanism by which SHA inhibited adsorption of PO 4 by goethite. This conclusion was supported by measurement of total organic C (TOC), infrared spectral features and Zeta potential. Adsorption of PO 4 onto goethite was inversely proportional to pH. Order of addition of PO 4 and SHA can influence adsorption of PO 4 as follows: prior addition of PO 4 ⩾ simultaneous addition > prior addition of SHA. Iron and SHA apparently form complexes due to prior addition of SHA. Observations made during this study emphasized that PO 4 forms different types of complexes on the surface of goethite at different pH, which dominated the interaction of SHA and PO 4 adsorption on goethite. Based on these observations, the possible modes of SHA inhibition of PO 4 adsorption on goethite were proposed. 相似文献
8.
Arsenate adsorption was studied in three clastic sediments, as a function of solution pH (4.0–9.0) and arsenate concentration.
Using known mineral values, protolytic constants obtained from the literature and K
ads values (obtained by fitting experimental adsorption data with empirical adsorption model), the constant capacitance surface
complexation model was used to explain the adsorption behavior. The experimental and modelling approaches indicate that arsenate
adsorption increases with increased pH, exhibiting a maximum adsorption value before decreasing at higher pH. Per unit mass,
sample S 3 (smectite–quartz/muscovite–illite sample) adsorbs more arsenate in the pH range 5–8.5, with 98% of sites occupied at pH 6.
S 1 and S 2 have less adsorption capacity with maxima adsorption in the pH ranges of 6–8.5 and 4–6, respectively. The calculation of
saturation indices by PHREEQC at different pH reveals that the solution was undersaturated with respect to aluminum arsenate
(AlAsO 42H 2O), scorodite (FeAsO 42H 2O), brucite and silica, and supersaturated with respect to gibbsite, kaolinite, illite and montmorillonite (for S 3 sample). Increased arsenate concentration (in isotherm experiments) may not produce new solid phases, such as AlAsO 42H 2O and/or FeAsO 42H 2O. 相似文献
9.
In this study, magnetite–maghemite nanoparticles were used to treat arsenic-contaminated water. X-ray photoelectron spectroscopy
(XPS) studies showed the presence of arsenic on the surface of magnetite–maghemite nanoparticles. Theoretical multiplet analysis
of the magnetite–maghemite mixture (Fe 3O 4-γFe 2O 3) reported 30.8% of maghemite and 69.2% of magnetite. The results show that redox reaction occurred on magnetite–maghemite
mixture surface when arsenic was introduced. The study showed that, apart from pH, the removal of arsenic from contaminated
water also depends on contact time and initial concentration of arsenic. Equilibrium was achieved in 3 h in the case of 2 mg/L
of As(V) and As(III) concentrations at pH 6.5. The results further suggest that arsenic adsorption involved the formation
of weak arsenic-iron oxide complexes at the magnetite–maghemite surface. In groundwater, arsenic adsorption capacity of magnetite–maghemite
nanoparticles at room temperature, calculated from the Langmuir isotherm, was 80 μmol/g and Gibbs free energy (∆G 0, kJ/mol) for arsenic removal was −35 kJ/mol, indicating the spontaneous nature of adsorption on magnetite–maghemite nanoparticles. 相似文献
10.
We used of a set of mechanistic adsorption models (1-pK TPM, ion exchange and Nica-Donnan) within the framework of the component additive (CA) approach in an attempt to determine the effect of repeated massive application of inorganic P fertilizer on the processes and mechanisms controlling the concentration of dissolved inorganic phosphorus (DIP) in soils. We studied the surface layer of a Luvisol with markedly different total concentrations of inorganic P as the result of different P fertilizer history (i.e. massive or no application for 40 years). Soil pH was made to vary from acid to alkaline. Soil solutions were extracted with water and CaCl 2 (0.01 M). The occurrence of montmorillonite led us to determine the binding properties of P and Ca ions for this clay mineral.Satisfactory results were obtained using generic values for model parameters and soil-specific ones, which were either determined directly by measurements or estimated from the literature. We showed that adsorption largely controlled the variations of DIP concentration and that, because of kinetic constrains, only little Ca-phosphates may be precipitated under alkaline conditions, particularly in the P fertilized treatment. The mineral-P pool initially present in both P treatments did not dissolve significantly during the course of the experiments. The adsorption of Ca ions onto soil minerals also promoted adsorption of P ions through electrostatic interactions. The intensity of the mechanism was high under neutral to alkaline conditions. Changes in DIP concentration as a function of these environmental variables can be related to changes in the contribution of the various soil minerals to P adsorption. The extra P adsorbed in the fertilized treatment compared with the control treatment was mainly adsorbed onto illite. This clay mineral was the major P-fixing constituent from neutral to alkaline pH conditions, because the repulsion interactions between deprotonated hydroxyl surface sites and P ions were sufficiently counterbalanced by Ca ions. The drastic increase of DIP observed at acid pH was due to the effect of the lower concentration of surface sites of Fe oxides and kaolinite.In addition to confirming the validity of our approach to model DIP concentrations in soils, the present investigation showed that adsorption was the predominant geochemical process even in the P fertilized soil, and that Ca ions can have an important promoting effect on P adsorption. However the influence of the dissolution of the mineral-P pool under field conditions remained questionable. 相似文献
11.
A combination of macroscopic experiments and in situ attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy was used to study Cd(II)-sulfate interactions on the goethite-water interface. The presence of SO 4 dramatically promoted Cd adsorption at lower pH (pH 5.5-6.5) and had a smaller effect at higher pH. ATR-FTIR studies indicated sulfate adsorption on goethite occurred via both outer- and inner-sphere complexation. The relative importance of both complexes was a function of pH and sulfate concentration. ATR-FTIR spectra provided direct evidence of the formation of Cd-SO 4 ternary surface complexes on goethite. In addition to ternary complexes, Cd specifically sorbed on goethite promoted SO 4 adsorption via changing the surface charge, and caused additional SO 4 adsorption as both inner- and outer-sphere complexes. The relative importance of ternary complexes versus electrostatic effects depended upon pH values and Cd concentration. Ternary complex formation was promoted by low pH and high Cd levels, whereas electrostatic effects were more pronounced at high pH and low Cd levels. A portion of SO 4 initially sorbed in inner-sphere complexes in the absence of Cd was transformed into Cd-SO 4 ternary complexes with increased Cd concentration. 相似文献
12.
Biosorption is an effective method to remove heavy metals from wastewater. In this work, the biosorption of Cd(II) onto Hydrilla verticillata was examined in aqueous solution with parameters of initial pH, adsorbent dosage, contact time, initial Cd(II) concentration,
temperature, and co-existing ion. Linear Langmuir and Freundlich models were applied to describe the equilibrium isotherms,
and both of the two models were fitted well. The monolayer adsorption capacity of Cd(II) was found to be 50 mg/g at pH 6 and
20°C. Dubinin–Radushkevich isotherm model was also applied to the equilibrium data. The mean free energy of adsorption (11.18 kJ/mol)
indicated that the adsorption of Cd(II) onto H. verticillata might be carried out via chemical ion-exchange mechanism. Thermodynamic parameters, including free energy (∆ G
0), enthalpy (∆ H
0), and entropy (∆ S
0) of adsorption, were also calculated. These results showed that the biosorption of Cd(II) onto H. verticillata was a feasible, spontaneous, and exothermic process in nature. Desorption experiments indicated that 0.01 mol/L EDTA and
HNO 3 were efficient desorbents for the recovery of Cd(II) from biomass. IR spectrum analysis suggested that amido, hydroxyl, C=O
and C–O could combine strongly with Cd(II). EDX spectrum analysis suggested that an ion exchange mechanism might be involved. 相似文献
13.
Simultaneous competitive adsorption behavior of Cd, Cu, Pb and Zn onto nine soils with a wide physical–chemical characteristics
from Eastern China was measured in batch experiments to assess the mobility and retention of these metals in soils. In the
competitive adsorption system, adsorption isotherms for these metals on the soils exhibited significant differences in shape
and in the amount adsorbed. As the applied concentration increased, Cu and Pb adsorption increased, while Cd and Zn adsorption
decreased. Competition among heavy metals is very strong in acid soils with lower capacity to adsorb metal cations. Distribution
coefficients ( K
dmedium) for each metal and soil were calculated. The highest K
dmedium value was found for Pb and followed by Cu. However, low K
dmedium values were shown for Zn and Cd. On the basis of the K
dmedium values, the selectivity sequence of the metal adsorption is Pb > Cu > Zn > Cd and Pb > Cu > Cd > Zn. The adsorption sequence
of nine soils was deduced from the joint distribution coefficients ( K
dΣmedium). This indicated that acid soils with low pH value had lower adsorption capacity for heavy metals, resulting in much higher
risk of heavy metal pollution. The sum of adsorbed heavy metals on the soils could well described using the Langmuir equation.
The maximum adsorption capacity ( Q
m) of soils ranged from 32.57 to 90.09 mmol kg −1. Highly significant positive correlations were found between the K
dΣmedium and Q
m of the metals and pH value and cation exchange capacity (CEC) of soil, suggesting that soil pH and CEC were key factors controlling
the solubility and mobility of the metals in soils. 相似文献
14.
Humic acid adsorption onto the bacterial surface of Bacillus subtilis was measured with and without Cd, as a function of pH and humic–bacteria–Cd ratios. These experiments tested for the existence of ternary interactions in a bacteria–humic–metal system. We determine both the effects of humic acid on the bacterial adsorption of Cd, as well as the effects of the aqueous metal cation on the bacterial adsorption of humic acid. The presence of Cd does not affect the extent of humic acid adsorption onto the bacterial surface, indicating that there is no competition for sorption sites between humic acid and Cd under the experimental conditions, and that changes in the charging properties of the bacterial surface, as a result of the Cd adsorption, are not significant enough to affect humic acid adsorption. The presence of humic acid does diminish Cd adsorption onto the bacterial surface, suggesting the presence of an aqueous Cd–humate complex under mid to high pH conditions. However, we also observe that the solubility of humic acid is unaffected by the presence of aqueous Cd. This apparently inconsistent behavior of an aqueous Cd–humate complex affecting Cd adsorption but not affecting humic acid solubility is not observed with simpler ionizable organic molecules. We propose that the solubility of humic acid is controlled by the solubility of a less soluble fraction of the acid. Cd forms an aqueous complex with the more soluble fraction of humic acid and there is no interdependence between the aqueous activities of the more and less soluble fractions. That is, the solubility of one humic acid fraction is unaffected by the presence of an aqueous Cd–humate complex involving another humic acid fraction. These experimental results constrain the relative importance of surface ternary and aqueous metal–humate complexes on the bacterial adsorption of both humic acid and metal cations. 相似文献
15.
The influence of parent rock and soil material on the corrosion rate of metallic fragments that remained in soil after World
War I in the Soča front area (Slovenia), as well as the corrosion products of these fragments, were studied. The results of
corrosion tests did not indicate appreciable differences in corrosion rates between various corrosion media. Consequently,
the corrosion rates are influenced mostly by soil aeration, soil humidity and also by microstructures of alloys. Soil type
seems to have the most influence on corrosion products. For the pH and Eh ranges that prevail in the studied soils, goethite
is the only stable iron mineral. Lead minerals are not stable, and lead, in a Pb 2+ cation form, is probably adsorbed onto some minerals – especially goethite – or is bound with organic matter. In distric
brown soil, lead stays in the cation form as Pb 2+ because of high soil acidity. Cuprite is stable in rendzina and brown soil on limestone, whereas in distric brown soil copper
stays in solution as Cu 2+.
Received: 7 October 1999 · Accepted: 8 March 2000 相似文献
16.
Siderophore-promoted iron acquisition by microorganisms usually occurs in the presence of other organic molecules, including
biosurfactants. We have investigated the influence of the anionic surfactant sodium dodecyl sulfate (SDS) on the adsorption
of the siderophores DFOB (cationic) and DFOD (neutral) and the ligand EDTA (anionic) onto goethite (α-FeOOH) at pH 6. We also
studied the adsorption of the corresponding 1:1 Fe(III)-ligand complexes, which are products of the dissolution process. Adsorption
of the two free siderophores increased in a similar fashion with increasing SDS concentration, despite their difference in
molecule charge. In contrast, SDS had little effect on the adsorption of EDTA. Adsorption of the Fe-DFOB and Fe-DFOD complexes
also increased with increasing SDS concentrations, while adsorption of Fe-EDTA decreased. Our results suggest that hydrophobic
interactions between adsorbed surfactants and siderophores are more important than electrostatic interactions. However, for
strongly hydrophilic molecules, such as EDTA and its iron complex, the influence of SDS on their adsorption seems to depend
on their tendency to form inner-sphere or outer-sphere surface complexes. Our results demonstrate that surfactants have a
strong influence on the adsorption of siderophores to Fe oxides, which has important implications for siderophore-promoted
dissolution of iron oxides and biological iron acquisition. 相似文献
17.
The adsorption of gold by pyrite, pyrrhotite, and mackinawite from solutions containing up to 40 mg/kg (8 μm) gold as hydrosulphidogold(I) complexes has been measured over the pH range from 2 to 10 at 25°C and at 0.10 m ionic strength (NaCl, NaClO 4). The pH of point of zero charge, pH pzc, has been determined potentiometrically for all three iron sulphides and shown to be 2.4, 2.7, and 2.9 for pyrite, pyrrhotite, and mackinawite, respectively. In solutions containing hydrogen sulphide, the pH pzc is reduced to values below 2. The surface charge for each sulphide is therefore negative over the pH range studied in the adsorption experiments. Adsorption was from 100% in acid solutions having pH < 5.5 (pyrite) and pH < 4 (mackinawite and pyrrhotite). At alkaline pH’s (e.g., pH = 9), the pyrite surface adsorbed 30% of the gold from solution, whereas the pyrrhotite and mackinawite surfaces did not adsorb.The main gold complex adsorbed is AuHS°, as may be deduced from the gold speciation in solution in combination with the surface charge. The adsorption of the negatively charged Au(HS) 2− onto the negatively charged sulphide surfaces is not favoured. The X-ray photoelectron spectroscopic data revealed different surface reactions for pyrite and mackinawite surfaces. While no change in redox state of adsorbent and adsorbate was observed on pyrite, a chemisorption reaction has been determined on mackinawite leading to the reduction of the gold(I) solution complex to gold(0) and to the formation of surface polysulphides. The data indicate that the adsorption of gold complexes onto iron sulphide surfaces such as that of pyrite is an important process in the “deposition” of gold from aqueous solutions over a wide range of temperatures and pressures. 相似文献
18.
The interacting effect of pH, phosphate and time on the release of arsenic (As) from As-rich river bed sediments was studied.
Arsenic release edges and kinetic release experiments (pH range 3–10), in the absence and presence of phosphate, coupled with
sequential extraction procedures, SEM/EDX analyses and geochemical calculations, were carried out to evaluate As remobilisation
and to elucidate the mechanisms involved. The results showed that As release underwent pronounced kinetic effects, which were
strongly influenced by pH and phosphate. Remobilisation of As after 24 h was low (between ~1 and 5%) and varied slightly with
pH, whereas alkaline conditions generally promoted As remobilisation after 168 h, with up to 12–21% of total As released.
The results showed that depending on the pH and sediment considered, the release of As increased dramatically after ~48–72 h,
suggesting that different processes are involved at different reaction periods. The addition of phosphate (1 mM) increased
both the amount of As released (between 2 and 8 times) and the rate of As release from the sediments within the entire pH
range (3–10) and period (168 h) studied. Moreover, in some cases, it also affected the shape of the As release edges and kinetic
profiles. The similarities in the release profiles and the positive correlations between As and some sediment components,
especially Fe and Al hydroxides, and organic matter—which appears to play a key role at high pH—suggest that As release from
the studied sediments may be associated with solid phase dissolution processes under both acid and alkaline pH, whereas desorption
plays a key role in the short term and at natural pH conditions, especially in the presence of phosphate, which acts as an
As-displacing ligand. Evaluation of As mobility based on short-time leaching experiments may seriously underestimate the mobilisation
of As from sediments. 相似文献
19.
Adsorption onto Fe-containing minerals is a well-known remediation method for As-contaminated water and soil. In this study, the use of acid mine drainage sludge (AMDS) to adsorb As was investigated. AMDS is composed of amorphous particles and so has a large surface area (251.2 m 2 g −1). Here, adsorption of both arsenite and arsenate was found to be almost 100%, under various initial AMDS dosages, with the arsenate adsorption rate being faster. The optimum pH for As adsorption onto AMDS was pH 7.0 and the maximum adsorption capacities for arsenite and arsenate were 58.5 mg g −1 and 19.7 mg g −1 AMDS, respectively. In addition, experiments revealed that AMDS dosages decreased As release from contaminated soil. Therefore, the AMDS used in this study was confirmed to be a suitable candidate for immobilizing both arsenite and arsenate in contaminated soils. 相似文献
20.
The acidification of paddy fields was studied in Guizhou Province, China. Affected by acid mine drainage, the pH value of irrigation water was 2.9 with the concentrations of iron and aluminium above 40 mg/L. Based on the pH(H 2O) of topsoil, the paddy fields studied were classified spatially into three zones, the natural zone (pH value from 6.2 to 5.5), the acidified zone (pH value from 5.5 to 4.5), and the seriously acidified zone (pH value from 4.5 to 3.2), respectively. Comparing to the natural zone, the buffering processes for acidification of paddy soil were discussed by considering the changes of calcium, magnesium, potassium and aluminium in soils. The Ca, Mg and K were leached from the soil by the decomposition of carbonate and kaolinite. The leaching of Mg became less with the enrichment of iron in topsoil layer. When the soil pH was below 5.0, aluminium was leached from soil because of the dissolution of alumino silicate minerals. In addition, the hydrolysis of iron and aluminium in soil provided more protons to promote the soil acidification. Furthermore, the buffer capacity of paddy soil was discussed by the results of buffer experiment, based on which the pH buffer curve was drawn and the empirical formula for calculating the acidification rate was developed. Because pH buffer capacity of soil is about 2.78 cmol c/kg pH for the pH(H 2O) value above 5.0, it is estimated that only another 50 years are needed for the pH(H 2O) of the paddy soil decrease to 3.5 in the acidified zone if the acid water is used for irrigation continuously. 相似文献
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