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1.
This study evaluated the effects of iron oxide (Fe2O3) and zinc oxide (ZnO) on two wheat genotypes (Kavir and Tajan) at three levels (0, 75, and 150 mM sodium chloride (NaCl)) of salinity. Spray treatments included two forms of normal and nanoparticles of Fe2O3 and ZnO, a mixture of nanoparticles of Fe2O3 and ZnO (2 g L?1) and a non-spray treatment. The pot experiment was arranged as factorial in a randomized complete block design with four replications. Two forms of Fe2O3 and ZnO significantly accelerated plant height, leaf area, shoot dry weight, and the concentration of iron (Fe) and zinc (Zn) in comparison with non-spray treatment. The highest plant height and leaf Fe concentration belonged to Fe2O3 nanoparticles; however, it seems that the spray of nanoparticles may not be superior compared with normal forms in alleviation of salinity impacts.  相似文献   

2.
Barrado  E.  Prieto  F.  Lozano  B.  Arenas  F. J.  Medina  J. 《Water, air, and soil pollution》2001,131(1-4):367-381
Waste water polluted with heavy metals can besuccessfully purified by precipitation of the metals from analkaline solution containing iron (II), giving rise to aferrite sludge. The solid metal ferrites obtained in thismanner can be used to remove hydrogen sulphide from a gasstream. Based on a Taguchi experimental design, ferrite solidparticle and pore size, and the temperature resulting inmaximum retention of H2S by the solid were optimised.Under the optimum conditions, predicted by the method, eachgram of ferrite was able to retain 0.274 g H2S.In addition, a ferrite containing a known lead concentration,obtained by the precipitation method under optimal conditionsof pH, temperature and Fe/Pb ratio, was used to study theexothermic H2S retention reaction. The chemical reactionoccurring between the ferrite and the H2S wasinvestigated by characterisation of the compounds before(Pb0.04FeII 0.96 FeIII 2O4·nH2O solids composed ofPbxFe3-xO4, magnetite Fe3O4 andhydrated lead oxide PbOn·H2O) and after (PbS, PbSO4, S, FeS2 and α-FeO(OH)) the retention process.  相似文献   

3.
Nanofertilizers, which supply nutrients to the plant, are used to replace conventional fertilizers. Iron (Fe) is one of the essential elements for plant growth and plays an important role in the photosynthetic reactions. To study the effects of nano-iron fertilizer on Catharanthus roseus, plants were treated with different concentrations (0, 5 10 20, 30, and 40 mM) of iron oxide nanoparticles (Fe2O3) for 70 days. Fe2O3 nanoparticles increased growth parameters, photosynthetic pigments, and total protein contents in the treated plants significantly. The maximum amounts of growth parameters, photosynthetic pigments, and protein contents were obtained with 30 µM Fe2O3 and minimum values of these parameters were found with 0 µM Fe2O3. The highest value of total alkaloid content was obtained in 0 µM Fe2O3 and the lowest value was observed in control plants. Iron oxide nanoparticles increased potassium, phosphorus, and iron absorption but did not show a significant effect on sodium content.  相似文献   

4.
A stable and efficient Fe2O3/expanded perlite (Fe2O3-Ep) composite catalyst was synthesized by a simple hydrothermal method for degradation of refractory contaminants in heterogeneous photo-Fenton system. X-ray diffraction and FT-IR analyses confirmed the presence of the Fe2O3 in the synthesized catalyst. The catalytic activity of the Fe2O3-Ep catalyst was evaluated by the degradation of rhodamine B (RhB, 5 mg/L) and metronidazole (MET, 5 mg/L) in the presence of H2O2 under visible light irradiation. The Fe2O3-Ep catalyst exhibited high efficiency for degradation of RhB at a wide pH range from 2 to 10 and showed excellent catalytic property for decomposition of MET as well. The degradation ratio of RhB was achieved 99%, and the removal ratio of COD was 62% within 90 min at the best experimental conditions (0.5 g/L of Fe2O3-Ep catalyst, 2 mL/L of H2O2). Furthermore, iron leaching of the Fe2O3-Ep catalyst during the catalytic degradation reaction was negligible and the catalyst still exhibited high catalytic activity and stability after five cycles. These results show that the catalyst can be used as a highly efficient heterogeneous photo-Fenton catalyst for the degradation of non-biodegradable refractory pollutants in water.  相似文献   

5.
A pot experiment was conducted to evaluate the effects of zinc oxide (ZnO) and iron oxide (Fe2O3) nanoparticles on the growth of two maize cultivars under the saline condition. Salt stress induced decreases of shoot, root dry weight, leaf area and leaf gas exchange of S.C. 704 more than Bulk. The increase of salinity level, chlorophyll a, b and total chlorophyll content and iron (Fe) and zinc (Zn) concentrations under all spray treatments declined. Application of ZnO and Fe2O3 significantly enhanced the root growth (17%), net carbon dioxide (CO2), assimilation rate (8%) and sub-stomatal CO2 concentration (5%) of maize compared to control. Nanoparticles of Fe2O3 and ZnO caused an increase in leaf Fe (22%) and Zn (11%) concentrations, respectively, compared with normal forms. According to the results, although the alleviation effects of Zn and Fe have been demonstrated under stress conditions, nanoparticles were more effective than normal forms, which may be due to their shape, size, distribution and characteristics.  相似文献   

6.

Purpose

Soil temperature is a fundamental parameter affecting not only microbial activity but also manganese (MnIII,IV) and iron (FeIII) oxide reduction rates. The relationship between MnIII,IV oxide removal from oxide-coated redox bars is missing at present. This study investigated the effect of variable soil temperatures on oxide removal by MnIII,IV and FeIII oxide-coated redox bars in water-saturated soil columns in the laboratory.

Materials and methods

The Mn coatings contained the mineral birnessite, whereas the Fe coatings contained a mixture of ferrihydrite and goethite. Additionally, platinum (Pt) electrodes designed to measure the redox potential (EH) were installed in the soil columns, which were filled with either a humic topsoil with an organic carbon (Corg) content of 85 g kg?1 (pH 5.8) or a subsoil containing 2 g Corg kg?1 (pH 7.5). Experiments were performed at 5, 15, and 25 °C.

Results and discussion

Although elevated soil temperatures accelerated the decrease in EH after water saturation in the topsoil, no EH decreases regardless of soil temperature occurred in the subsoil. Besides soil temperature, the importance of soil organic matter as an electron donor is highlighted in this case. Complete removal of the MnIII,IV oxide coating was observed after 28, 14, and 7 days in the soil columns filled with topsoil at 5, 15, and 25 °C, respectively. Along the Fe redox bars, FeIII reducing conditions first appeared at 15 °C and oxide removal was enhanced at 25 °C because of lower EH, with the preferential dissolution of ferrihydrite over goethite as revealed by visual differences in the FeIII oxide coating. Oxide removal along redox bars followed the thermodynamics of the applied minerals in the order birnessite > ferrihydrite > goethite.

Conclusions

In line with Van’t Hoff’s rule, turnover rates of MnIII,IV and FeIII oxide reduction increased as a result of increased soil temperatures. Taking into account the stability lines of the designated minerals, EH-pH conditions were in accordance with oxide removal. Soil temperature must therefore be considered a master variable when evaluating the oxide removal of redox bars employed for the monitoring of soil redox status.
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7.
G. Brümmer 《Geoderma》1974,12(3):207-222
Results of laboratory experiments with soil material saturated with sea water indicate that, as predicted by thermodynamics, manganese (III, IV)-oxides are first reduced to Mn2+-ions (beginning at about +450 mV at pH 6.1.; E7 ≈ +400 mV), next amorphous iron (III)-oxides are reduced to Fe2+-ions (beginning at about +220 mV at pH 6.0; E7 ≈ +160 mV), and finally sulphates are reduced to sulphides (beginning at about +10 mV at pH 6.0; E7 ≈ -50 mV). Direct quantitative relations between redox potentials, pH-values and Mn2+- (or Fe2+-) contents of water-saturated soils and sediments and calculated redox reactions of known manganese and iron systems could not be established.The influence of organic redox systems produced by microbial fermentation processes on the measured potentials and on the reduction of manganese and iron oxides is discussed.A reduction of the oxides by microbially formed sulphides, which themselves are oxidized by this process, seems also to be possible. Therefore, sulphides do not occur as stable sulphur phase in higher amounts before all available Fe-oxides are reduced to Fe2+-ions. Then formation of iron monosulphides takes place by precipitation of Fe2+- ions by sulphides (H2S, HS). In a sulphide-stabilized environment redox reactions of sulphur — especially the reaction H2Saq = S0 + 2 H+ + 2 e? — may determined the measured potentials.The results show that the dynamics and morphology of hydromorphic soils and sediments are strongly dependent on microbial processes.  相似文献   

8.
Autotrophic microbial sulfate reduction was tested in a fixed-bed bench-scale column experiment to lower sulfate and iron loads in acid-mine-drainage-influenced groundwater. The microbial process was enhanced by injecting H2 gas as electron donor into the silicate bed. The experiments were performed at 2.5 atm and 10°C. Complete iron removal (3.8?±?0.3 mM) and partial sulfate removal from 17 to 9 mM were achieved at rates of about 0.004–0.019 mmol SO4 per liter per hour and at hydraulic retention times of 51.5–19.8 days. The tests showed that most microbial activity took place in immobile zones. These zones create stable environmental conditions for the microorganisms leading to constant reduction rate despite possibly unfavorable conditions prevailing in the mobile phase. Diffusion between mobile and the immobile zones was not found to be the limiting factor for sulfate reduction. Rather, low H2(aq) concentrations due to low H2 solubility combined with the inhomogeneous distribution of H2 gas in the pore space limited sulfate reduction. H2(aq) concentrations in some parts of the sediment body were insufficient to maintain H2(aq) concentrations in the immobile zones above the level of substrate limitation. Fe and S precipitated mostly as iron monosulfide and accumulated in regions with high H2(aq) availability. Calculations showed that the deposition of iron sulfide in the pore space does not affect the pore volume significantly.  相似文献   

9.
To study the factors that influence the release of free H2S, flooded soils were incubated with plant material and either sodium sulphate or elemental sulphur. Residual sulphate, FeS and H2S were measured throughout the reaction. Less free H2S was evolved from a periodically waterlogged soil than from a well-drained soil of comparable HC1- and dithionite-soluble Fe content. With a readily soluble synthetic Fe2O3 as the source of Fe, a slight excess of Fe over the SO42– equivalent sufficed to prevent loss of H2S. The native organic matter in the well-drained Rothamsted top-soil seemed to have no effect in promoting loss of H2S, but the FeS:H2S ratio was strongly influenced by the nature of the plant material used as the source of energy. With either Na2SO4 or S, considerably more free H2S was evolved with lucerne than with rice blade. With S, the pH of the incubated mixtures was close to that of the nominally S-free system, whereas with Na2SO4 the mixture became quite alkaline. More free H2S was evolved under the more alkaline conditions obtained with Na2SO4, which suggests that it is the initial mobilization of Fe that governs the distribution of the reduced S, rather than the pH-solubility relations of FeS. An oxidized surface layer is very effective in retaining sulphur in the soil.  相似文献   

10.
Most drugs are synthesized by human medicine both for the treatment of men and animals and are also produced to maintain their physical and chemical properties for a time sufficient to serve a therapeutic purpose in treatments of some kind of illness. Ciprofloxacin is an antibiotic synthetically obtained in 1987 and belongs to the family of fluoroquinolones and is currently prescribed in certain treatments. This work was developed with the objective of evaluating the adsorption of the ciprofloxacin antibiotic in solution on zinc oxide (ZnO) supported on SBA-15-type mesoporous silica. The results showed that the post-synthesis method is effective in impregnating zinc oxide in SBA-15 and its structure has not been damaged and has not lost its organization in the hexagonal 2D planes. The ZnO-SBA-15 (10%) sample adsorbed 69.10% of ciprofloxacin (25 mg/L) in 180 min. Freundlich adsorption model was observed with the correlation factor of R2?=?0.9999, for the adsorbent ZnO-SBA-15 (10%), which showed the best sample. The kinetics was classified as pseudo-second order, as well as the thermodynamic parameters were determined, showing that the process has a spontaneous nature and a value of ΔH°?=?4.677 kJ/mol, evidencing that the process has the nature of physiosorption.  相似文献   

11.
Abstract

To evaluate the relationship between the amount of available Silicon (Si) in paddy soils and their mineral properties on the Shounai Plain in Japan, which is formed from several parent materials, we evaluated the amount of available Si, the particle size distribution, the oxide composition of crystalline minerals and the amount of oxalate-extractable Si (Sio), iron (Feo) and aluminum (Alo) in the soil. The amount of available Si in the soil and the oxide content of the crystalline minerals differed among four soil groups that were distinguished by their clay mineral composition. There was no difference in the particle size distribution among the soil groups. The amount of available Si was positively related to the SiO2/Al2O3 ratio of clay, the CaO concentration of silt and fine sand, and the amounts of Sio, Feo and Alo in the soil. The amount of available Si in the soils was negative correlated with the Na2O and K2O concentrations of silt, the K2O concentration of fine sand, and the coarse sand content. These results suggest that the amount of available Si in soils is affected by the weathering resistivity of their minerals and that the particle size distribution and mineral composition are related to the available Si of the soils. Mineralogical properties, including the particle size distribution and mineral composition such as the SiO2/Al2O3 ratio × clay fraction content and the amounts of CaO and MgO in silt-sized particles, were positively correlated with the amount of available Si in the soil, but these correlations were not found for fine sand-sized particles. The Sio, Feo and SiO2/Al2O3 ratio × clay fraction contents contributed approximately 50% to the amount of available Si in the soils. The amount of available Si in the soil was divided into two groups according to the location of the paddy field. The amount of soil-available Si in the alluvial plain was affected by the geology upstream through the mineral composition.  相似文献   

12.
Effect of iron oxide on phosphate sorption by calcite and calcareous soils   总被引：3，自引：0，他引：3  
Pure calcite (AR grade CaCO3) was treated with ferrous perchlorate solution to give a surface coating of iron (Fe) oxide. Maximum sorption (xm) of phosphate (P) by the calcite increased from 18.2 to 160 mg P kg?1 as the amount of coating increased from 0.00 to 16.0 g Fe2O3, kg?1 CaCO3. Evidence for Fe oxide coatings on carbonate minerals in two Sudanese soils was obtained by optical microscopy and electron-probe microanalysis. The relative contributions of carbonate and Fe oxide minerals, and Fe oxide coatings to P sorption in these soils were calculated, based on an assumed model of oxide distribution. Separate-phase Fe oxide was the major contributor (30–40%) to P sorption in the soils; the Fe oxide coatings on carbonate minerals were only minor contributors (< 6%), and the contribution of uncoated carbonate minerals was found to be negligible (<1 %). These results suggest a very minor role for carbonate minerals, even when coated with Fe oxide, in the sorption of P by these calcareous, Sudanese soils.  相似文献   

13.
The changes of Eh and pH in soil suspension (Ah-horizon of a Mollic Gleysol) and Mn2+ or Fe2+ concentrations in the equilibrium soil solution at different levels of glucose (0%, 0.5% and 1%) and MnO2 (0%, 0.025%, 0.05% and 0.1%) or Fe2O3 (0%, 0.025%, 0.05% and 0.1%) were examined. It was found that the degree of Mn- and Fe-reduction in soil depends mainly on the presence and the amount of an easily decomposable carbon source and to a minor degree on the content of native or added forms of MnOO2 or Fe2O3 in the soil. Theoretical relationships between the water soluble manganese and iron and the Eh and pH values have been verified, when the observed initial drop of Eh was eliminated. It was found that the water soluble manganese content was described best by the Mn2O3/Mn2+ redox system, and that of iron by the Fe3 (OH)3/Fe2+ system.  相似文献   

14.
Studies were conducted to examine factors which might influence the status and distribution of S in some surface horizons and typical profiles of soils derived from Xiashu loess on the upper slope (US), middle slope (MS) and lower slope (LS) of Nanjing-Zhenjiang-Yangzhou hilly zone. The total S contents varied from 70.30 to 350.21 mg/kg, and the average for all surface soils was 218.3 mg/kg. The average S contents in the profiles followed the sequence: USo) and the ratio of amorphous iron oxide to free iron oxide (Feo/Fea), but no significant relationship was found between total S and the ratio of free iron oxide to total iron (Fed/Fet). Inorganic sulphate in paddy soils (MS and LS) was nearly higher in surface soil than in subsurface soil and subsoil, it, however, remained relatively unchanged with increasing depth for the original soil profile (US). The average organic S accounted for 94% of the total S in the surface soils, but the percentage decreased with depth in the profiles. Like the total S, the organic and inorganic S contents were highly significantly correlated with organic matter, total N, Feo and Feo/Fed ratio, but they were insignificantly related to Fed/Fet ratio. The C/S and N/S ratios in this study were somewhat lower than the results reported by others. The C/N/S ratios varied considerably within the same profile and among different soils but they fell within the range of values reported worldwide.  相似文献   

15.
陈怀满 《土壤学报》1988,25(1):66-74
采用选择溶解法研究了有机质、游离铁、无定型硅、铝等土壤组份对青黑土、黄棕壤、红壤和砖红壤胶体吸附和解吸Cd的影响。结果表明,去除有机质后胶体吸附Cd减少,这可能是由于交换吸附的减少所致;游离铁的去除使得黄棕壤、红壤和砖红壤的吸附量显著减少,显示了在这些土壤中游离氧化铁专性吸附的重要性;随着无定形铝含量的上升,吸附量下降,这是因为铝离子占据了高能量的吸附位。经不同处理后的土壤胶体,其Cd的解吸顺序(解吸%)大致为:去无定型硅、铝者>去游离铁者>去有机质者>原胶体,但在不同土壤和不同pH条件下该顺序略有差别。研究结果为控制和改造土壤Cd污染提供了理论依据。  相似文献   

16.
Abstract

The capacity of 36 Western Australian soils to adsorb phosphorus (P) was measured by three different methods: P retention index (PRI), P buffering capacity (PBC), and P adsorption (PA). The P adsorption values measured by all three methods varied markedly with soil type. When the P adsorption values were correlated with several soil properties, using simple and multiple linear regressions, PRI, PBC, or PA values were found to be significantly correlated with the aluminium oxide content of the soils. In addition, PBC and PRI was correlated with organic carbon content. The role of aluminium oxide (Al2O3) in the soil was apparently more important in determining the P adsorption capacity of the soils than that of iron (Fe), even though the iron oxide (Fe2O3)content of all the soils studied was consistently higher than the aluminium oxide content. The relationship between P adsorption and the selected soil properties, as determined by multiple linear regression, explained 45–59% of the variation: arabic PRI = ‐10.87 + 9.94 organic C (%) + 160.02 Al2O3 (%), r2 = 0.45.

arabic PBC = ‐0.004 + 1.532 organic C (%) + 22.26 Al2O3 (%), r2 = 0.57.

arabic PA = 3.52 + 248.75 Al2O3 (%), r2 = 0.59.

  相似文献   

17.
Technogenically contaminated urban soils contain a substantial amount of magnetite Fe3O4, whereas another ferrimagnetic, i.e., maghemite αFe2O3, more often prevails in unpolluted soils. The content of magnetite may exceed the content of another iron oxide, hematite, in contaminated soils. In the town of Chusovoi, where emissions from a single enterprise, a metallurgical plant, predominate among pollutants, the upper soil horizons are contaminated with magnetite of one type. In the much larger city of Perm, the polluting sources are diverse, which results in a wide variation of magnetic susceptibility of technogenic magnetite. The difference in magnetite properties may depend on the composition and the content of heavy metals associated with this mineral. A considerable amount of oxalate-soluble magnetite in technogenically contaminated soils produces two important consequences. Schwertmann’s criterion Feox: Fedit as a gleying index turns out to be overestimated and, therefore, does not work in technogenically contaminated soils. The second consequence is that Tamm’s reagent is inapplicable to extracting heavy metals bound to amorphous iron compounds from contaminated soils. On the other hand, a high solubility (30–60%) of technogenic magnetite by oxalate favors the use of Tamm’s reagent for the complete extraction of iron (hydr)oxides and heavy metals bound to them.  相似文献   

18.
In this study, photocatalytic degradation of bisphenol A (BPA) was investigated using two types of catalysts (TiO2 and ZnO) with various metal ion concentrations and amounts of added H2O2. A kinetic test was performed to observe the changes of BPA over time under UV irradiation in a photocatalytic reactor. Experimental results demonstrated that degradation efficiency of ZnO was higher than that of TiO2. The degradation rate increased as catalyst dosage increased until reaching optimum dosage, after which degradation rate decreased. The addition of H2O2 improved the degradation efficiency of BPA, with the degradation efficiency increasing with the amount of H2O2. All metal ions, including Fe2+, Ni2+, and Cu2+, inhibited the degradation of BPA by ZnO at natural pH, whereas Fe2+ and Ni2+ enhanced degradation efficiency of BPA at acidic pH. Comparison of BPA degradation with H2O2 only, ZnO/H2O2, Fe2+/H2O2, and ZnO/Fe2+/H2O2 revealed that Fe2+/H2O2 was more efficient than other processes at lower pH (pH?=?3.44), whereas ZnO/H2O2 the most efficient at higher pH (pH?=?6.44). These results indicate that ZnO/H2O2 process was observed to be the most efficient of all processes. Degradation efficiency of BPA by ZnO was also influenced by additional parameters, including H2O2 concentration, metal ions, and solution pH.  相似文献   

19.
A method for the simultaneous determination of aluminum (Al), arsenic (As), calcium (Ca), cadmium (Cd), chromium (Cr), copper (Cu), iron (Fe), magnesium (Mg), manganese (Mn), phosphorus (P), lead (Pb), sulfur (S), selenium (Se), vanadium (V), and zinc (Zn) in organic soil amendments using microwave-assisted acid digestion and inductively coupled plasma optical emission spectroscopy (ICP OES) is proposed. Concentrated or diluted acids mixtures (HNO3, HF, HBF4, and H3BO3) combined or not with H2O2 were systematically evaluated in order to achieve the best digestion procedure for masses of around 150 mg of samples. Principal component analysis (PCA) was applied in order to choose the best acid mixture for digestion (3 mL HNO3 + 1 mL HBF4 + 2 mL H2O). The determined concentrations were in accordance with certified values of CRM 029 at the 95% confidence level, according to the Student-t test. This acid mixture was successfully applied for the digestion of four organic soil amendment samples (organic fertilizers, substrates, and soil conditioners) and element determination.  相似文献   

20.
The study of the color in the CIE-L * a * b * system proved that, among the soils developed on the recent and ancient alluvium in the Perm Cis-Urals region, there are no soils composed of only brown horizons: the low-redness topsoils occur even in the automorphic soils. The color of the bulk of the soils does not depend on the total content of Fe-(hydr)oxide particles. The soils developed on the two-layered deposits are an exception, since the color of the lower layer of the heavy loam is affected by hematite-containing clay particles. In the upper horizons of other automorphic soils, red pigment is produced rather by Fe-containing hydroxides (feroxyhyte δFeOOH and Fe-vernadite Fe-δMnO2) than by hematite αFe2O3. The gleyed horizons are rich in free iron compounds (up to 3.2% (Fe2O3)d) that exert a weak effect on the redness. An identification procedure of the horizons showing hydromorphic features is developed, including the color control both in the untreated samples and in the samples in which the organic substance has been oxidized with H2O2. The soil becoming green after the organic matter oxidation appears to be a distinctive feature of the hydromorphic horizons, while reddening is a property of the automorphic horizons.  相似文献   

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