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1.
The acid–base buffering of gleyic gray-humus soils developed in brook floodplains and undisturbed southern-taiga landscapes has been characterized by the continuous potentiometric titration of soil water suspensions. During the interaction with an acid, the major amount of protons (>80%) is consumed for the displacement of exchangeable bases and the dissolution of Ca oxalates. In the O and AY horizons, Mn compounds make the major contribution (2–15%) to the acid buffering. The buffer reactions with the participation of Al compounds make up from 0.5 to 1–2% of the total buffering capacity, and the protonation of the surface OH groups of kaolinite consumes 2–3% of the total buffering capacity. The deprotonation of OH groups on the surface of Fe hydroxides (9–43%), the deprotonation of OH groups on the surface of illite crystals (3–19%), and the dissolution of unidentified aluminosilicates (9–14%) are the most significant buffer reactions whose contributions have been quantified during the interaction with a base. The contribution of the deprotonation of OH groups on the surface of kaolinite particles is lower (1–5%) because of the small specific surface area of this mineral, and that of the dissolution of Fe compounds is insignificant. In the AY horizon, the acid and base buffering of soil in the rhizosphere is higher than beyond the rhizosphere because of the higher contents of organic matter and nonsilicate Fe and Al compounds.  相似文献   

2.
Neutralization is the necessary operation to ensure the Fenton effluent pH. In situ coagulation can be induced during neutralization. In this study, three types of alkaline neutralizers (Ca(OH)2, NaOH, and Ca(OH)2?+?NaOH) were added into the Fenton oxidized PSE to control the effluent pH of 6 to 9. The coagulation behavior, floc structure, and properties were investigated. The results indicated that the coagulation with the adding of three neutralizers can remove 9.68 to 24.02% of the TOC. Ca(OH)2 exhibited the highest TOC removal efficiency at the dosage of 0.4 g/L. Charge neutralization ability was in the following order: Ca(OH)2?>?Ca(OH)2?+?NaOH?>?NaOH. Ca(OH)2 and Ca(OH)2?+?NaOH showed the increase of floc growth rate with the increase of agent dosage, especially for Ca(OH)2?+?NaOH. Moreover, Df of NaOH flocs was higher than that of Ca(OH)2 and Ca(OH)2?+?NaOH, indicating the floc formed by NaOH was more compact than that of Ca(OH)2. The main coagulation process of three neutralizers was different, and it was also affected by the agent dosage (or pH). When the dosage was 0.35 g/L (pH 6–7.5), the complexation, adsorption, and bridging were the predominant processes while charge neutralization gradually became the main coagulation process for Ca(OH)2 and Ca(OH)2?+?NaOH with the increase of dosage (pH 7.5–9).  相似文献   

3.
石灰性土壤交换性盐基组成的测定,通行的方法是采用70%乙醇溶液反复洗盐,再经pH 8.50.1 mol L-1氯化铵-70%乙醇(CH3CH2OH)溶液进行多次交换处理,测定交换液中的K+、Na+、Ca2+、Mg2+浓度。但此方法常常受操作步骤繁琐,以及土壤中碳酸盐的溶解量因多次浸提而增加的困扰,最终导致测定结果偏高。基于上述原因,选择不同浓度、不同pH的NH4OAc和NH4Cl 10种交换剂,对比分析10种交换剂中的碳酸盐溶解度和土壤交换性钙镁含量。结果表明,pH=8.5 1 mol L-1氯化铵-70%乙醇(CH3CH2OH)溶液较适合石灰性土壤交换性盐基的测定。此新方法是先经70%乙醇(CH3CH2OH)溶液洗盐,再用pH8.5 1 mol L-1氯化铵(NH4Cl)-70%乙醇(CH3CH2OH)溶液进行一次性交换处理,然后测定交换液的K+、Na+、Ca2+、Mg2+浓度,简化了操作程序的同时有效抑制了土壤碳酸盐的溶解,降低了测定结果的偏差。  相似文献   

4.
Phosphate (P) sorption and the concomitant release of sulphate (SO,), silicate (Si) and hydroxyl ion (OH) were determined on three allophanic soils from Spain, at different P concentrations. P effectively replaced SO4, Si and OH. However, at every stage of P sorption, the molar ratios of the total amounts of anions released (SO4+ Si + OH) to that of the sorbed P were low. The amount of added P affected the relative proportions of SO4, Si and OH exchanged. At low concentrations of P, phosphate sorption was accompanied mostly by release of the adsorbed SO4 with some Si. As more P was sorbed an increasing displacement of OH was also observed.  相似文献   

5.
T. Eschena  A. Violante 《Geoderma》1974,11(4):313-321
H-Al-clays and Al-clays with adsorbed Al3+ were obtained by treating H-clay with basic aluminum chlorides at different concentrations and OH/AL < 2 ratios. HAl(OH)n-clays and Al(OH)n-clays, on the contrary, were obtained by treating H-clay with basic aluminum chlorides with OH/Al > 2 ratios; further, the more concentrated the exchanging solution of basic aluminum chlorides, the more hydroxylated were the aluminum ions bound to the exchanger.The system HAl(OH)n-clay is unstable and tends to convert into a more stable aluminum clay system by neutralization between adsorbed basic aluminum and hydrogen ions.  相似文献   

6.
研究菜籽多酚、Vc、菜籽多酚与Vc混合物在化学模拟体系中清除超氧阴离子自由基OH.O2.与羟自由基.OH自由基的能力。用邻苯三酚自氧化法测定抗氧化剂清除OH.O2.的能力,用铁氧化邻二氮菲-Fe2+法测定抗氧化剂清除.OH的能力。结果表明:菜籽多酚、Vc、菜籽多酚与Vc的混合物清除OH.O2.、.OH都不呈剂量-效应关系。菜籽多酚在0.25mg/ml浓度时对OH.O2.与.OH的清除率均最高,分别达51.40%和84.82%。Vc在0.80mg/ml时对OH.O2.的清除率最高,达80.39%;在0.40mg/ml时对.OH的清除率最高,达91.35%。当总浓度为0.25mg/ml时,菜籽多酚与Vc的混合物没有协同增加清除OH.O2.的作用;菜籽多酚与Vc按7∶3、8∶2两种比例混合,在清除.OH时有协同增效作用,协同增效的最佳比例为7∶3,最大清除率达78.78%。  相似文献   

7.
Land development has caused runoff of red soil into the ocean on the north side of Okinawa Island, Japan. In an attempt to clarify the impacts of this “red soil pollution” on the oxidizing power of seawater, we studied the formation of hydroxyl radical (?OH), the most potent oxidant in the environment, in red soil-polluted waters using a 313-nm monochromatic light. ?OH was photochemically formed in the red soil-polluted water samples, and the formation rates of ?OH decreased as salinity increased, i.e., as red soil-polluted river water gets mixed with seawater. The photo-formation rates of ?OH showed good correlations with dissolved Fe concentrations (R 2?=?0.96) and [NO2 ?]?+?[NO3 ?] concentrations (R 2?=?0.87), while a negative and weak correlation was found with dissolved organic carbon concentrations (R?=??0.78). Theoretical calculation showed that direct photolysis of NO3 ?, Fe(OH)2+, and hydrogen peroxide all together accounted for less than 10% of the observed ?OH formation in the red soil-polluted waters. Comparison between filtered and unfiltered samples showed that red soil particles were not the main sources of ?OH, and the photolysis of NO2 ? could account for at most 78% of the observed ?OH formation rates. We found that the Fenton’s reaction (a reaction between Fe(II) and H2O2) could possibly account for the observed formation of ?OH in the red soil-polluted waters.  相似文献   

8.
The effects of several factors on the settling rate of aluminiumhydroxide were investigated during chemical coagulation using aluminium salts. Experimental variables were pH, aluminium (III) concentration and the order of addition of reagents. Experiments were carried out at pH 5–8 and rapid settling was achieved when aluminium (III) solutions were added to Na2CO3 solutions near neutral pH, close to the minimumsolubility pH of Al(OH)3. For a narrow range of total Al concentration where Al(III) species were supersaturated with respect to the solid phase, Al(III)-added-to-carbonate type mixtures yielded a higher settling rate than mixtures obtainedby the reverse order of reagent addition. The results were interpreted by comparing the rates of formation of polymer andsolid (amorphous Al(OH)3) phases. It was concluded that Al(III) coagulants should be added to water containing natural or artificially incorporated carbonate alkalinity for rapid settling of Al(OH)3 flocs.  相似文献   

9.
Abstract

Soil degradation caused by excessive land use is presently one of the major constraints on sustainable agriculture in the mountainous area of northern Thailand. In order to obtain basic information about soil fertility problems involved in the transition from traditional shifting cultivation to more intensive upland farming, the dynamics of K, Mg, and Ca, and soil acidity in the farming systems of both Karen and Hmong/Thai peoples were investigated. In the fields that lay fallow for more than 5 y, the soils were highly acidic and poor in exchangeable bases, mainly due to the fact that the fallow vegetation rapidly absorbed inorganic bases (K, Mg, and Ca) in the soils. In the fields both under fallow and cropping within 3 y after the slash and burn practice, the high acidity observed in the soils at the fallow stage seemed to be alleviated by ash input with high alkalinity. The aboveground biomass ranged from 9 to 10 t ha?1 in the 8 y fallow field and the sum of inorganic bases and alkalinity, which were expected to be added to the soils with ash input, ranged from 3 to 4 kmol( + ) ha?1 or kmol(-) ha?1 , respectively. In the fields under continuous cultivation for more than 4 y after the slash and burn practice, the subsoils showed a more acidic nature than in the fields immediately after burning. Judging from the high concentrations of inorganic bases in the soil solution from the subsoils, the decrease of the content of exchangeable bases and resulting soil acidification might have proceeded through leaching loss of these bases. Among the exchangeable bases in the soils, Ca and Mg were generally predominant and K occurred as trace. Comparison of the total contents of the bases with the contents of exchangeable ones showed that most of Ca occurred in an exchangeable form while most of K and Mg occurred in the nonexchangeable forms in the soils. Therefore, Ca was likely to be readily depleted along with soil acidification in continuous cultivation.  相似文献   

10.
玉米花生混作对花生根系还原力和花生铁营养的影响   总被引：5，自引：1，他引：4  
采用自行设计的立培一营养液联合体系培养装置．研究了混作对花生根系还原力和铁营养状况的影响。向营养液中供给难溶性的氢氧化铁后,在不同的时间内测定花生根系的还原力及新叶中铁的含量。结果表明,在3～9天中单作花生还原力明显高于混作花生,12～15天期间单作花生还原力迅速下降并低于相应的混作花生;而混作花生在6～15无中缓慢上升,并在较长时间内维持了较高的还原力。花生新叶活性铁含量测定结果表明,在加入难溶性氢氧化铁后第3天,单作、混作花生新叶活性铁含量无明显的差异,而至第9天、第15天时,单作花生活性铁含量低于混作花生。玉米与花生混作对改善花生营养状况具有重要的作用。  相似文献   

11.
Liming-induced changes in cation exchangeability were studied in six samples from acid sulphate soils (pH 3.9-4.7) incubated with water or with equivalent quantities of Ca(OH)2 or KOH. The extractability of acid cation species susceptible to hydrolysis was shown to be affected not only by increased pH but also by the kind of the cation and related electrochemical properties of the base used. Both liming treatments practically eliminated the exchangeable Al. In the virgin soils, however, the polynuclear Al-complexes formed by Ca(OH)2 treatment seemed to have been hydrolyzed further. The superiority of Ca(OH)2 was assumed to be due to the higher valency of its cation and its act of provoking a higher increase in ionic strength. The liming agents affected to varying extents also the extractability of base cations. Exchangeable soil K seemed to decrease by the KOH treatment and the soil Ca by the Ca(OH)2 treatment, whereas K and Ca were only slightly, if any, affected by the Ca(OH)2 and KOH treatments, respectively. Thus, the reductions were assumed to be attributable to other factors than increased pH. A fixation of K and a possible precipitation of Ca as CaSO4 were discussed. Ca(OH)2 decreased in all soil samples the exchangeability of Mg more than did KOH. The depression was not related to the Al polymerization and, thus, cannot entirely be ascribed to specific sorption on Al gel. The results imply that liming may affect base cation exchange reactions by neutralizing exchangeable Al of high bonding strength and by replacing it by cations of the liming agent.  相似文献   

12.
Proton consumption with phosphate adsorption on amorphous Fe (III) hydroxide (am-Fe(OH)3) was compared between two different pH-controlled conditions in a 0.1 mol dm-3 NaClO4 solution at initial pH values of 5.50 and 4.50, at 298±0.005 K.

The number of protons caused by phosphate dissociation was subtracted from the total number of protons consumed, then the amount of surface OH groups released by the ligand exchange reaction were determined. When a sequential acid titration by a pH-stat maintained pH values of the systems at initial pH values, the percentage of OH groups released during the ligand exchange reaction was almost constant, 29–37%. When the pH values of the systems increased with phosphate adsorption, the percentage of OH groups released by the ligand exchange reaction varied from -4.3 to 33%. The difference in the proton migration between the two pH-controlled conditions not only depended on the phosphate dissociation, but on the difference in the adsorption mechanism, i.e. the ratio of ligand exchange with OH groups to total phosphate adsorption.  相似文献   

13.
J.B. Harsh  H.E. Doner 《Geoderma》1985,36(1):45-56
A freeze—fracture technique was used to prepare replicas of interlayer surfaces of a hydroxy-aluminum montmorillonite (OH-Al-SWy-1), synthesized by titrating an Al-clay with NaOH. Aqueous suspensions containing 0.01 M NaClO4 and 4% OH-Al-SWy-1 were frozen rapidly with Freon 22 to vitrify the solution phase and stored in liquid N2. The frozen samples were fractured at 10?6 Torr and 158K and C-Pt replicas were made of the exposed surface. Transmission electron microscopy (TEM) of the replicas showed a randomly distributed surface precipitate. The precipitate was flat and angular, resembling gibbsite morphologically. Gibbsite crystals were observed outside the interlayer when the suspension was air-dried on microscope grids, underscoring the value of the freeze—fracture technique in minimizing alteration of the OH-Al-SWy-1 complex. Using the mass of Al(OH)3 fixed by the clay and the average particle perimeter observed by TEM (49.3 nm), we estimated the maximum Al(OH)3 surface charge density and site density available for phosphate adsorption. The range of surface charge density for the Al(OH)3, estimated from crystallographic data, was very close to the range of surface charge density for montmorillonite, suggesting that the latter may influence the maximum particle size of the precipitate. The total charge and edge [-Al(OH)(H2O)] site density were less than the observed CEC reduction on SWy-1 and maximum phosphate retention on OH-Al-SWy-1 at pH 5.3, respectively. Interlayer Al(OH)3 is known to be unstable with respect to gibbsite and it is possible that a relatively high specific surface area was responsible for the high solubility.  相似文献   

14.
低钾配施纳米氢氧化镁对白菜的营养效应研究   总被引：4，自引：2，他引：2  
【目的】 探讨低量施钾条件下配施纳米氢氧化镁对白菜营养效应的影响和提高钾素利用效率的作用。【方法】 采用酸性紫色土在西南大学进行了大白菜盆栽试验。在所有处理均施N 200 mg/kg和P2O5 100 mg/kg的基础上,试验设不施钾,低钾量（K2O 75 mg/kg土）,适量钾（K2O 105 mg/kg土）,低量钾配施纳米氢氧化镁1.13、1.88 mg/kg土,共5个处理。在大白菜生长68天后收获,测定了白菜产量、叶绿素含量、抗氧化能力、养分吸收量及钾素利用效率、营养品质等指标。【结果】 低量钾配施纳米氢氧化镁对白菜增产作用极显著,配施氮磷钾肥总量的0.3%（1.13mg/kg土）时白菜产量增加21.5%;配施纳米氢氧化镁使白菜叶绿素a含量、叶绿素b含量、叶绿素总量和叶绿素a/b值分别提高5.3%~10.3%、4.0%~6.1%、4.8%~8.9%和4.3%~8.7%。提高白菜抗氧化能力,使白菜胡萝卜素、总酚和类黄酮等非酶类抗氧化物质含量分别提高7.6%、6.2%和6.8%~20.0%,超氧化物歧化酶（SOD）、过氧化物酶（POD）和过氧化氢酶（CAT）等酶类抗氧化物质含量分别提高9.8%~18.8%、10.7%~11.2%和7.4%~9.9%。配施纳米氢氧化镁促进白菜养分吸收,白菜磷、镁含量分别提高3.8%~16.9%、11.1%~24.9%,氮、磷、钾和镁吸收量分别提高9.1%~10.2%、13.2%~32.3%、8.4%~14.4%、26.6%~39.7%,钾素偏生产力、钾素农学效率、钾素生理效率和钾素利用率分别提高20.6%~23.7%、74.5%~77.6%、27.4%~36.5%和14.6%~25.0%。低钾与纳米氢氧化镁配施的效果以配施氮磷钾肥总量的0.3%好于配施0.5%（1.88 mg/kg土）。配施纳米氢氧化镁对白菜可溶性糖含量影响不大,对氨基酸含量有一定的降低作用,但显著降低硝酸盐含量11.5%~12.9%,有利于改善白菜卫生品质。【结论】 综合白菜产量、叶绿素含量、抗氧化能力、养分含量和吸收量、钾素利用效率和营养品质,以配施氮磷钾肥总量0.3%的纳米氢氧化镁处理综合效应最佳。  相似文献   

15.
Phosphogypsum (PG) was mixed with calcium hydroxide [Ca(OH)2], ranging from 0 to 5%, to determine the optimal amount of Ca(OH)2 required to alkalize the acidity of PG. The alkalized PG by 4% of Ca(OH)2 addition was selected for field tests to evaluate the effects of alkalized PG on soil microbial, chemical properties, and yield of Chinese cabbage. Soil pH increased with increasing application rate of the alkalized PG and decreased with the unmodified PG application. Available phosphorus (P), water‐soluble sulfate (SO4 2?), and exchangeable potassium (K), calcium (Ca), and magnesium (Mg) increased significantly with increasing application rate of alkalized and unmodified PG. Microbial biomass carbon (C) and nitrogen (N) concentrations, soil enzyme activities, and the yield of Chinese cabbage in the alkalized PG application were greater than those of unmodified PG application. We concluded that alkalizing PG by mixing it with an alkaline material such as Ca(OH)2 can turn it into a useful material for agricultural utilization.  相似文献   

16.
Cadmium is both readily available and highly toxic to plants and animals. Our objectives were to evaluate the effect of oyster shell as a liming material on reducing plant cadmium (Cd) uptake and to compare oyster shell and Ca(OH)2, a common liming material in Korea. Ground oyster shell and Ca(OH)2 were applied at 0, 2, 4, and 8 Mg Ca per hectare to an upland soil contaminated manually with CdSO4 (total Cd 8.96 mg kg?1). Radish (Raphanus sativa L.) was sown on the contaminated soil. Oyster shell was less effective at increasing soil pH and net negative charge than Ca(OH)2, but more effective at suppressing radish Cd uptake in both roots and shoots. The portion of Cd that is strongly bound to soil (fraction 5) increased more with oyster shell than with Ca(OH)2. Radish plant Cd concentration was positively correlated with 0.1 N HCl-extractable Cd and negatively correlated with the residual Cd fraction (F5), indicating that an increase in the strongly bound Cd fraction played an important role in reducing radish Cd uptake in soil to which oyster shell was applied. The greater potential of oyster shell to decrease Cd extractability in soil and plant Cd uptake compared to Ca(OH)2 might be attributed to the layered morphology of oyster shells. Based on these results, oyster shell could be a very good alternative liming material to reduce Cd phytoavailability in Cd-contaminated soil.  相似文献   

17.
Photochemical formation rates and sources of the hydroxyl (OH) radical were determined in dew water formed on the surface of Japanese red pine (Pinus densiflora) needles of declining (NO2 polluted area) and healthy pine stands at Mt. Gokurakuji located west of Hiroshima city in western Japan. The measured OH radical photoformation rates in dew water (n=10), which were normalized to the rate at midday on May 1 at 34°N, ranged from 0.67 to 5.18 µM h?1 (1M=1mol L?1). The mean value (2.69 µM h?1) was higher than that in dew water collected on a Teflon board and higher than the mean value in rain water published previously. Of the total OH radical formation rate observed in dew water on the pine needles, 16.4 % was estimated to originate from N (III) (NO2 ? and HNO2) and 24.6 % was estimated to originate from NO3 ?. There were other sources of OH radical photochemical formation in dew water on the pine needles besides photolysis of NO2 ? and NO3 ?.  相似文献   

18.
Conductimetric titrations, with NaOH, of solutions containing Al ion detect two OH-ions of Al in the acid range, with OH/Al ratios of ions such as Al(OH)2+ and A16(OH)3+15; in the alkaline range aluminate Al(OH)?14 is formed. Similar titrations of an Al-kaolin, prepared by acid washing, give results that can be adequately interpreted in terms of these three ions, i.e. by the reaction with alkali of Al3+ ions balancing the permanent isomorphous replacement charge. If there are reactions with alkali at the edge-faces of the kaolin, e.g. the neutralization of residual positive edge-charge, these edge-charges must be small in comparison with the permanent charge. Bonding by the complex ion Al6(OH)3+15, formed on the surfaces of clay particles, explains why the viscosity of Al clays is greatest at the five-sixths stage of neutralization, because the formation of the hydroxide Al(OH)3 is theoretically equivalent to the measurement of the permanent charge.  相似文献   

19.
Abstract

Phosphorus (P) determination by the phosphomolybdate‐blue (Mo‐blue) and phosphomolybdate‐vanadate‐yellow (vandate‐yellow) color methods using NH4OH to neutralize excessive acidity were unaffected by increasing manganese (Mn) content in standard P solutions and rice plant acid digests. The vanadate‐yellow color method using sodum hydroxide (NaOH) to neutralize excessive acidity over estimated P when the Mn content exceeded 0.16 Hg/ Mn/mL in the final dilution of standard P solution and 247 fig Mn/g in rice plant tissue. Phosphorus determination by the vanadate‐yellow color method using ammonium hydroxide (NH4OH) was linearily related with P estimated by the Mo‐blue color and vanadate‐yellow color methods using NaOH for acid neutralization. Phosphorus estimated by the vanadate‐yellow color method using NH4OH could be calculated from the a regression between both methods of neutralizing the excessive acidity.  相似文献   

20.
Abstract

The effect of alternating waterlogged and drying conditions on phosphorus (P) availability and sorption was studied in three soils of contrasting chemical and physical properties. Soils were treated with two levels of P (0 and 50 mg kg‐1; P0 and P50), waterlogged for 21 days, then allowed to dry at room temperature for 14 days. The availability of P, iron (Fe), and manganese (Mn) over the waterlogged and drying periods was determined by shaking samples of each soil with 1M NaOAc (pH 3). Increasing concentrations of 1M NaOAc (pH 3) extractable P (Pac) over the waterlogged period was attributed to solubilization of Fe(OH)3 materials under reducing conditions with the release of sorbed and occluded P. The released P appeared to be resorbed by freshly precipitated amorphous Fe(OH)2 material since earlier studies showed that water soluble P concentrations in these soils were reduced to negligible levels under waterlogged conditions. The Fe(OH)2 material remained readily extractable with 1M NaOAc (pH 3) since Feac increased dramatically with waterlogging. Drying the waterlogged soils caused a rapid decrease in Pac, Feac and Mnac suggesting the Fe(OH)2 may have been transformed into more stable forms [e.g., Fe(OH)3]. Much of the changes in Pac appeared to be due to changes in Feac, with limited influence from Mnac. and mineralization of organic P. Phosphate sorption isotherms were determined using the standard batch technique for air‐dry, waterlogged (with and without ponded water), and waterlogged/dried conditions. Sorption isotherms were not affected by waterlogging and subsequent drying. Most soils sorbed all of the added phosphate irrespective of moisture treatment.  相似文献   

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