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1.
We studied the relative influences of Mn2+, Al3+ NO3? and SO42? on the K-Ca relationship, as expressed by a pK-0.5pCa value, in a Mn oxide suspension system using a double indicator electrode technique. With an increase in the quantity of solution Mn2+ and Al3+ in the system, Mn2+ ions showed a stronger effect than Al3+ on increasing pK-0.5pCa values, though this was not the case when the amount of the cations added was low. The stronger effect of Mn2+ on the K-Ca relationship was attributed to stronger specific adsorption of the Mn2+ ion on the Mn oxide as compared with Al3+. When K+ and Ca2+ were added after the addition of Mn2+ and Al3+, activities of K and Ca in equilibrium solution were higher than those when K+ and Ca2+ were added first, indicating that the exchange reaction of the cations on the Mn oxide was not fully reversible. Compared to NO3? added systems, the pK-0.5pCa values for SO42? added systems were lower when the initial K/Ca molar ratios were 0.5 and 2. This effect of SO42? on the pK-0.5pCa values was also related to the quantity of Ca ions in the system since no significant difference in pK-0.5pCa values was observed between the SO42? and NO3? added systems when the K/Ca molar ratio was 8. The present results revealed that both cationic and anionic environments had a profound influence on the adsorption of K and Ca and, thus, the pK-0.5pCa values in a Mn oxide system. The findings of this study help attain a better understanding of the chemistry of K in soils, particularly those with variable charge.  相似文献   

2.
Concentrated Animal Feeding Operation activities lead to soil degradation in vicinity with the livestock breeding facilities, mainly due to ammonia emissions from the various stages of the process. In this research, the soil degradation effects of an intensive hog farming operation (IHFO) located at a Mediterranean limestone soil coastal area, have been investigated. Soil samples of the upper mineral soil were taken in various distances (10?C1,500?m) and directions from the IHFO boundaries. Thirteen experimental cycles were carried out in the duration of 1.5?years starting in March 2009 until October 2010. The soil samples were analysed on total, exchangeable and water-soluble Al, Fe and Mn. Significantly higher concentrations of the exchangeable and water-soluble Al, Fe and Mn were observed on soil samples at increasing proximity downwind from the farm (south). Southern soil average concentrations of exchangeable Al3+, Fe3+ and Mn2+ ranged between 3.56 and 7.45?mmol Al3+ kg?1 soil, 5.85 and 7.11?mmol Fe3+ kg?1 soil and 2.36 and 5.03?mmol Mn2+ kg?1 soil, respectively. Southern soil average concentrations of water-soluble Al, Fe and Mn forms ranged between 1.1 and 4.6?ppm Al, 0.5 and 0.8?ppm Fe and 0.4 and 1?ppm Mn, respectively.  相似文献   

3.
The fate of the radioisotopes of caesium (134Cs, 135Cs and 137Cs) in the environment depends largely on the extent and reversibility of its adsorption on soil, but there is still debate as to the underlying mechanisms and the best experimental approach to study the processes. The aim of this study was to elucidate the variation of the interaction of a trace amount of 137Cs with soil and to find the best methodology to monitor these changes. The loss of 137Cs from solution has been monitored over 4 months in soil microcosms at 20°C under both flooded and aerated conditions, and with or without organic amendments (leaf compost or lucerne straw). These treatments were chosen to vary concentrations of potassium and ammonium that compete with Cs for adsorption. We distinguished between spatial heterogeneity within soil aggregates leading to diffusion limitation of adsorption, adsorption kinetics at the soil‐solution interface and changes in soil affinity caused by the dynamics of competing cations. The extractability of 137Cs by stable Cs was used to probe the degree of fixation. Adsorption was initially under‐estimated, caused by equilibration of 137Cs within soil aggregates at a sub‐millimetre scale. Ammonium produced under reducing conditions in flooded samples and potassium released by lucerne straw inhibited 137Cs adsorption by up to a factor of 2. Important differences between samples were masked when soil was suspended in a simple electrolyte solution, thus diluting the competing cations, potassium and ammonium. There was evidence of increased fixation both during incubation and by air‐drying leading to up to a two‐fold decrease in extraction. Monitoring of dynamics of Cs and competing cations in soil solution provided useful information that was lost when soil was suspended in solution or air‐dried.  相似文献   

4.
The main objective of this study was to examine the effectiveness of vermiculite for removing heavy metals from water. Vermiculite components were analyzed by X-ray fluorescence, and the concentrations of metal ions were measured by inductively coupled plasma spectrometry. Serial batch kinetic tests and batch sorption tests were conducted to determine the removal characteristics for heavy metals in aqueous solutions. Solution pH values of tests with the inflated vermiculites generally increased and then stabilized. Equilibrium pH was generally established within 5?h. Removal rates of inflated vermiculite were tested at the initial concentration of 3?mg/L. At equilibrium concentrations, except for chromium (36.23%), most heavy metals were effectively removed (96.08?C98.54%). Finally, sorption data were correlated with both Langmuir and Freundlich isotherms. For each metal, the Q max obtained using the Langmuir isotherm was as follows: lead, 725.4?mg?kg?1; cadmium, 568.8?mg?kg?1; zinc, 540.2?mg?kg?1; copper, 457.2?mg?kg?1; and chromium, 0.9?mg?kg?1. The study results indicate that inflated vermiculite has outstanding removal rates and therefore can be used as an adsorbent for various heavy metals.  相似文献   

5.
Humic acid (HA) extracted from a Eustis loamy sand (Psammentic Paleudult, Red Yellow Podzolic soil) was flocculated by titration with Al3+-, Fe3+-, Cu2+-, Zn2+-, Mn2+-, Ba2+-, Ca2+-, and Mn2+-chloride solutions, respectively, to determine possible development of metal-HA complexes, as reported by Flaig et al. (1975), and Tiurin and Kononova (1962). Titration was conducted with HA solutions with an initial pH 11.5 or 7.0. The results indicated that the cations used, except Mg2+, yielded insoluble complexes with HA, irrespective of initial pH. After titration, the pH of the metal-HA flocs was 6.0–7.0, which was expected in view of the presence of cation exchange and buffering capacity of HA compounds. More complex formation through electrovalent and covalent bonding by COO? and phenolic OH groups of the HA molecule was only attained by the use of HA solutions with pH 11.5. On the other hand, less complex formation occurred by the use of HA solutions with an initial pH 7.0, through electrovalent bonding by COO? groups. Differential thermal analysis (d.t.a.) curves of HA showed shifts in temperatures of the main decomposition peak as a result of flocculation with the different metals. Based on the type of the cations involved, the metal-humic acid flocs could be listed in the following decreasing order of thermal stability: Al3+ = Zn2+ = Mg2+ ≥ HA > Ca2+ > Ba2+ > Fe3+ > Cu2+ > Mn2+. A systematic relationship could not be found indicating that trivalent ions resulted in the formation of thermally less stable metal-humic acid flocs than divalent ions, as has been reported for HA-metal complexes. Physical mixtures of HA and metal hydroxides exhibited d.t.a. features resembling those of original (nontreated) HA, but not those of the HA-metal flocs.Infrared spectroscopy revealed increased absorption for COO? vibrations at 1620 and 1400cm?1 in spectrograms of metal-HA flocs compared to that of original humic acid, a phenomenon explained by many authors to be caused by bonding of the metal ions in hydrated form to the carboxyl or phenolic hydroxyl groups or both of the humic acid molecule. HA-flocs formed from solutions with an initial pH 11.5 had identical i.r. spectra compared with those formed from solutions with an initial pH 7.0.  相似文献   

6.
In the present study, soil samples collected from 20-year (1993?2013) long-term tobacco plantation and perennial fallow were analyzed to study the influence of soil acidification on soil physicochemical and mineralogical properties. Results showed a significant decrease of soil pH, Ca2+, Mg2+, Na+ and total exchangeable cations, except K+, under tobacco plantation than under fallow land. Further X-ray diffraction (XRD) analysis for 1 mm soil size demonstrated an increase of vermiculite and kaolinite, but an obvious decrease of original potassium-bearing mica and potassium feldspar, under tobacco plantation than under fallow. For the <2 μm soil clay fraction, the XRD patterns showed an obvious desilication and accumulation of Al and Fe under tobacco plantation than under fallow. Other potassium-bearing minerals, such as illite and chlorite, had also visibly weathered and slaked under tobacco plantation than under fallow, resulting in an increase of vermiculite and hydroxy-Al-vermiculite, and an accelerated decomposition of 2:1 minerals and formation of 1:1 minerals. These results demonstrated that long-term continuous tobacco plantation has exerted negative effects on soil acidification and maintenance of soil potassium-bearing minerals.  相似文献   

7.
Seven different samples of goethite with differing crystallinity were prepared and the rate of reaction of six metal ions was measured for up to 4 weeks. The ions used were: Cu2+, Pb2+, Cd2+, Mn2+, Ni2+ and Cr3+. For Cu, decreasing goethite crystallinity, and therefore increasing porosity, increased the rate of reaction. In contrast, for Pb there was no effect. Hydrothermal treatment, which was used to induce ‘healing’ in one of the goethites, did not prevent the continuing reaction. It decreased the rate of reaction for Cu, Mn and Cd, but had no effect on Ni and Cr. This suggests that the main route for Ni and Cr is not via pores, but by lattice diffusion. The presence of silicate in the goethite decreased the reaction of Mn and Cd. We suggest that silicate decreased the spaces between goethite domains and that these spaces are the pathways largely used by these two ions. These observations show that metallic cations differ amongst themselves, and differ from anions such as phosphate, in the pathways they follow when they penetrate materials such as goethite subsequent to an initial adsorption reaction.  相似文献   

8.
Heavy metal ions such as Cr, Ni, Cu, Cd and Zn have been removed from the electroplating waste using Fe(III) hydroxide as adsorbent. The maximum removal of these metal ions (>90%) occurred at pH 8 to 9. Removal of SO 4 2? (98%) occurred at pH 4. Anions were found to play a negative role in the adsorption phenomenon. Metal ion Sorption has been found to decrease with increasing anionic concentrations. The methodology proposed might provide an inexpensive and economical procedure for removal and recovery of toxic metals from electroplating wastes.  相似文献   

9.
Abstract

Previously published results on exchange capacities for Ca2+, Mg2+, Mn2+, and K+ in the Donnan free space of roots of two ryegrass cultivars (Lolium multiflorum Lam. cv. Marshall and Wilo) grown at two Al levels in the nutrient solution (0 and 74 μM) were correlated with the average net uptakes of the same cations. For Al‐treated plants regressed separately, significant correlations r=0.906 and r=0.963 were found for Mn2+ and Ca2+/Mg2+, respectively. No significant correlations were observed for these cations in control plants. In contrast, when data of control and Al‐treated plants were combined, significant linear correlations r=0.805, r=0.924, and r=0.968 were found for Ca2+, K+, and K+/(Ca2++Mg2+)1/2, respectively. The influence of cations adsorbed onto the root exchange sites and the effect of Al on the cation uptake processes were discussed.  相似文献   

10.
The mineral mobilisation in ground water due to rock water interaction largely depends on the localized subsurface geo-chemical environment. During this work, traces of uranium were measured by adsorptive stripping voltametry (AdSV) in groundwater having various level of dissolved minerals. Experimental solutions were prepared in the laboratory by spiking natural groundwater with standard solutions of major cations (Ca2+, Mg2+, K+), anions (Cl?1, F?1, and $ {\text{PO}}^{{3 - }}_{4} $ ), trace metal ions (Cu and Pb) and DOC (Dissolved Organic Carbon). The concentrations of these anions, cations and DOC in subsurface water changes due to changes in the geo-chemical environment at different locations. Experimental results show that major anions do not have any pronounced impact on the analysis of uranium. In the case of cations, only Cu2+ shows strong interferences. However addition of 2% Ethylene Diammine Tetra-acetic Acid (EDTA) solution in the ratio of 1:25 removes interference due to copper upto a concentration of <0.2 ppm. Interference with copper was also studied by varying the accumulation potential, pH and concentration of chloroanilic acid. Though no interferences were observed in ground water having dissolved organic carbon (DOC) in the range of 0.01–15 ppm, between 15–16 ppm of DOC, the ability to detect uranium by AdSV decreases sharply. Further, if DOC exceeded 16 ppm it was not possible to do the analysis of uranium by AdSV without destruction of DOC, as DOC is a surface active organic compound and accumulates on Hg electrode preferentially over uranium-chloroanilic complex.  相似文献   

11.
Inorganic pyrophosphatase activity in three soils decreased when exchangeable and soluble metals were removed by leaching with in NH4OAc (pH 8). The effect of added metal ions at various concentrations in the leached soils showed that, at certain concentrations, Ba2+, Ca2+, Co2+, Mg2+, Mn2+, Ni2+ and Zn2+ promoted, K+ and Na+ had no effect, and Fc2+ and Cu2+ decreased pyrophosphatase activity. At high concentrations (>50 mM). Co2+, Mn2+, Ni2+ and Zn2+ inhibited pyrophosphatase activity in two soils. The concentration of metal ion needed for optimum activity of pyrophosphatase varied among the soils. The efficiency of the metal ions at optimum concentrations (average percentage increase for three soils in parentheses) in promoting pyrophosphatase was Ca2+ (47) > Mg2+ (42) > Ba2+ = Co2+ (29) > Ni2+ (27) > Zn2+ (20) > Mn2+(16). Pyrophosphatase activity in two leached soils adjusted to 50, 75, 100 or 150 mM PPi and Ca2+ or Mg2+ concentrations from 0 to 250 mM was at an optimum when the metal ion: PPi ratio was 1:1. Soil pyrophosphatase in the presence of 200 mM CaCl2 or MgCl2 was protected against inactivation by heat (90 C for up to 30 min).  相似文献   

12.
Equilibrium studies on soil require reliable estimates of ion concentrations in the soil solution under field conditions. We evaluated the previously described iterative method to approximate the equilibrium soil solution (ESS) with four acid forest soils. We examined for which ions the ESS is suitable, making use of the fact that concentrations in water extracts are functions of the soil: solution ratio. The electric conductivity, pH, and the concentrations of base cations, Mn2+, NO?3, SO42+, and dissolved organic carbon (DOC) were usually linear with the soil:solution ratio in water extracts, whereas no relation was observed for Al (with one exception) and Fe. Assuming that the ESS can be attributed the soil solution ratio of the field moist soil at the time of sampling, concentrations appeared as the continuation of the linear relation with the soil: solution ratio for base cations, pH, and the electric conductivity. This indicates that the ESS actually represents field conditions for these solution properties. For Al water extracts allowed no evaluation of the ESS result. The ESS underestimated SO42? concentrations under field conditions, presumably because the lack of DOC in the solutions added distorts the balance amongst anions.  相似文献   

13.
Roots of rice (Oryza sativa L.) exposed to 25, 50, and 100 ppm concentrations of manganese (Mn2+) in solution culture at pH 4.0, 5.0, 6.0, 7.0, and 8.0 for 48 hours developed visible brown coatings (plaque) of oxidized Mn. Most plaque was deposited on a region of the root 1–6 cm long above the root tip. Manganese in root plaque was removed by dithionite‐bicarbonate‐citrate extraction and internal root Mn released by pressure digestion. Concentrations of Mn were determined by atomic absorption spectrometry. Mean concentrations of Mn in plaque exceeded concentrations of Mn remaining in roots after the DCB wash in all treatment conditions. Concentrations of plaque and internal Mn increased with increasing pH and Mn2+ concentration in the treatment solution. Significant positive correlations existed between plaque and internal Mn concentrations at high pH. A larger percentage of total root metal remains in Mn plaqued roots after DCB treatment than has been previously observed in similarly treated iron (Fe) plaqued roots.  相似文献   

14.
The phenomenon of decline of take‐all [a disease on wheat caused by Gaeumannomyces graminis var. tritici (Ggt)] is poorly understood. In this study, the capacity of Ggt strains, isolated from wheat roots grown in the field plots exhibiting various levels of take‐all decline, to oxidize Mn2+ ions was tested. Growth of all Ggt isolates on agar was increased by an addition of up to 100 mg'L‐1 Mn2+ and was decreased by greater concentrations. The Ggt isolates oxidized Mn2+ to Mn3+ and/or Mn4+. There was a negative relationship (r=‐0.69) between the Mn2+ oxidation ranking and the extent of take‐all decline. A decreased capacity to oxidize Mn2+ causes a decrease in Ggt virulence and may result in decline in take‐all. This mechanism of take‐all decline is expected to act additively with other factors.  相似文献   

15.
The increased magnesium (Mg) concentration in vegetables may be reduced due to inter-ionic inhibition caused by the concentration of other water-soluble cations that are mainly associated to low molecular weight organic anions. However, it is not known whether the levels of these compounds in crop residues are modified by increasing the Mg soil application. This study aimed to assess the effects of the Mg application on the contents of water soluble cations [potassium (K+), calcium (Ca2+), magnesium (Mg2+), cooper (Cu2+), iron (Fe2+), manganese (Mn2+), and zinc (Zn2+)] on common bean plant residues. The experiment was conducted under greenhouse conditions with Ustoxix Quatzipsamment in completely randomized design in 4×5 factorial scheme, with three replicates. The treatments consisted of four rates of Mg [0, 50, 100 and 200 mg kg?1, source magnesium chloride (MgCl2)] and five varieties of common bean of the carioca group [BRS Estilo, BRS Ametista, IPR Campos Gerais (CG), IPR Tangará and IAPAR 81]. The Mg rates affected the contents of water soluble Ca2+, Mg2+, Cu2+, Fe2+ and Mn2+ in the extracts of bean residue. The soluble Mg2+ showed a significant correlation with foliar Mg content, indicating the need for further research on the method used to assess nutrient availability in vegetables. The bean varieties showed different responses regarding balance of ions in cation exchange capacity (CEC) and in the Ca/Mg, Ca/K and Mg/K ratios in the soil.  相似文献   

16.
This study compared the tolerance limits of selected bacterial (Bacillus licheniformis, Brevibacillus lactosporus and Pseudomonas putida) and protozoan (Aspidisca, Trachelophyllum and Peranema) species to V5+ in wastewater systems. The isolates were exposed to various concentrations of V5+ (from 10 to 240?ppm), and their tolerance limits to this heavy metal were assessed at different temperatures (25, 30, 35 and 40°C) and pHs (4, 6, 7, 8 and 10) for 5?days. Chemical oxygen demand (COD), dissolved oxygen (DO) and die-off rate of the isolates were measured using standard methods. The results indicated that test isolates were tolerant to V5+, with a gradual decrease in their colony/cell counts when V5+ concentration gradually increased. Bacterial species were found to be more significantly tolerant (MIC: 110?C230?ppm?V5+) to V5+ than protozoan species which showed an earlier total inhibition/die-off rate (100%) at 60?C100?ppm?V5+ (MIC) (p?<?0.001). P. putida was the most tolerant bacterial species (MIC: 230?ppm?V5+) and Aspidisca sp. the most sensitive protozoan species (MIC: 60?ppm?V5+). An increase in COD and DO removal was observed throughout the experimental period. The highest COD increase (up to 237.11%) and DO removal (almost 100%) were observed in mixed liquor inoculated with P. putida after exposure to 10?ppm?V5+. Changes in pH and temperature affected the tolerance limits of all isolates. This study suggests the use of these tolerant bacterial and protozoan species in the bioremediation of V5+ from domestic and industrial wastewater under the control of pH and temperature.  相似文献   

17.
The intracellular inorganic pyrophosphatases obtained from mixed cultures of soil microorganisms were characterised in terms of the activating cation and pH-activity profile. Microorganisms were grown in an initial culture 10 mm in tetrasodium pyrophosphate, a nutritionally non-specific aqueous medium, buffered at pH 7.0 with an organic buffer and inoculated with soil. The intracellular pyrophosphatases in a desalted, cell-free enzyme preparation were examined for activity in assays using 1 mM tetrasodium pyrophosphate and nine cations (Mg2+, Zn2+, Co2+, Mn2+, Fe2+, Ca2+, Cu2+, Al3+ and Fe3+) over the pH range 2–10, with appropriate buffers. Only the first 5 cations activated the enzymes. The pH-activity profiles for each cation were different and each displayed only one pH optimum. The pH optima were not greatly affected by cation concentration or kind of buffer. The specific activities at the optimum pH and cation concentration for each culture decreased in order Mg2+ > Zn2+ > Co2+ > Mn2+ > Fe2+. The results indicate the production of functionally similar enzymes by diverse microorganisms.  相似文献   

18.
The effects of a series of divalent, first row transition elements, i.e. Mn2+, Co2+, Ni2+, Cu2+ and Zn2+ on the crystallization of ferrihydrite have been compared. With the exception of Mn2+, the metal ions considered, stabilized ferrihydrite and enhanced the amount of haematite in the reaction product. The stabilizing ability of these ions could be related to the increase in covalency of these metals along the series. With more than 15 mole% divalent metal ion present, ferrihydrite transformed to a spinel phase by a dissolution/reprecipitation mechanism. These metals can replace some Fe3+ in the structures of the crystallization products. Factors that influence the extent of isomorphous substitution are the match between the radii and charges of Fe3+ and the substituent ions and also, the congruency of dissolution of the M/ferrihydrite coprecipitate.  相似文献   

19.
The uptake of micronutrient cations in relation to varying activities of Mn2+ was studied for barley (Hordeum vulgare L. var. Thule) and oat (Avena sativa L. var. Biri) grown in chelator buffered nutrient solution. Free activities of Mn2+ were calculated by using the chemical speciation programme GEOCHEM-PC. Manganese deficient conditions induced elevated concentrations of Zn and Fe in shoots of both species. The corresponding antagonistic relationship between Mn and Cu could only be seen in barley. The observed antagonistic relationships were only valid as long as the plant growth was limited by Mn deficiency. The Mn concentration in both plant species increased significantly with increasing Mn2+ activity in the nutrient solution. The concentration of Mn in the shoots of oat was higher than for barley except under severe Mn deficiency where it was found equal for both species. Manganese was accumulated in the roots of barley at high Mn2+ activity. The different shoot concentrations of Mn between barley and oat are therefore attributed to the extent of Mn translocation from roots to shoots. Manganese deficiency induced a significant increase in the shoot to root ratio in both species.  相似文献   

20.
Cesium-137 (137Cs) is strongly adsorbed on clay minerals, especially on illite. The adsorption of Cs+ on reference clay minerals, however, has not been fully investigated in relation to the presence of illite. The objective of this study was to clarify the effect of impurities (i.e., illite and vermiculite), present in reference smectite group minerals and kaolin minerals, on the retention of Cs+. The clay mineralogy of the reference minerals was characterized by X-ray diffraction (XRD). The radiocesium interception potential (RIP) was measured as an index of the Cs+ retention ability of clays. The content of illite in clay was represented by the total potassium (K) content given that illite is a major source of K in the clay fraction. The content of vermiculite in clay was represented by the Cs fixation capacity induced by Cs saturation followed by heating of samples at 110°C. Metabentonite and beidellite gave extremely high RIP values compared with other smectite group minerals, although a peak for illite (at 1.0 nm) was not observed in XRD analysis. The reference smectite and kaolin minerals showed a range of RIP values, even though their RIP values are theoretically zero. The RIP values had a significant positive correlation with the total K content of all the reference clay minerals (rs = 0.621*). This indicated that the retention ability for 137Cs depended more on the content of illite, as impurity, rather than the type of bulk mineral. Hence, the contribution of illite to the magnitude of the RIP was elucidated by the combination of measurement of total K content and XRD analysis.  相似文献   

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