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几种土壤铁锰结核对Cr(Ⅲ)的氧化特性Ⅱ.pH、离子强度、温度等因素的影响 总被引：2，自引：1，他引：2
以我国几种土壤中铁锰结核为材料 ,研究了不同pH、离子强度和温度条件下氧化锰矿物对Cr(Ⅲ )的氧化。结果表明 :随着体系pH的降低、离子强度的增加以及温度的升高 ,供试铁锰结核对Cr(Ⅲ )的氧化量增加 ,这除了与其氧化还原反应本身消耗H 有关外 ,还与氧化锰矿物表面电荷性质和电位变化、共存的氧化铁矿物有关。而上述因素的变化导致N2 1、N4 1号样氧化Cr(Ⅲ )的增幅比N5 1号样的大 ,则可能与氧化锰矿物的结晶程度、晶体构造和铁锰结核中Mn(Ⅳ )的含量等有关 相似文献
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研究探讨了土壤锰还原和溶解的动力学特征,为土壤锰的植物有效性提供科学依据。以无机酸和酸化还原剂(HCl、NH2OH.HCl-HNO3、NH2OH.HCl-HAc)处理为对照,用连续液流法研究柠檬酸和葡萄糖对土壤锰溶解的影响。结果表明,柠檬酸、葡萄糖可通过在土壤固相表面的吸附使其中的锰还原溶解,几种化合物对土壤锰的相对溶解能力强弱顺序为:0.04 mol.L-1NH2OH.HCl(25%HAc)>0.1 mol.L-1NH2OH.HCl-0.001 mol.L-1HNO3>1%柠檬酸>0.5%柠檬酸>0.1 mol.L-1HCl>1%葡萄糖>0.5%葡萄糖>0.01 mol.L-1HCl。用不同数学模型模拟化合物对土壤锰溶解动态过程,5种方程拟合的相关系数均达到极显著水平(P<0.01),并且以指数方程、Elovich方程和权函数方程拟合所得的标准差较小,抛物线扩散方程拟合的标准差最大。表明几种化合物对土壤锰氧化物的溶解速率受控于表面化学反应,而不是由扩散来控制。 相似文献
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利用高效液相色谱仪及田间试验方法,建立了乙嘧酚在黄瓜和土壤中的残留分析方法,研究了乙嘧酚在黄瓜和土壤中的残留消解动态,对影响残留分析方法的主要参数进行了优化。黄瓜和土壤样品分别用乙腈和丙酮提取,硅胶柱净化,高效液相色谱仪二极管阵列检测器检测,外标法定量。结果表明,该方法的最小检出量为3.5×10^-10 g,在黄瓜和土壤中的最低检测浓度分别为0.010和0.005 mg.kg^-1。乙嘧酚的平均添加回收率为80.5%～103.1%,变异系数为2.10%～3.74%。消解动态试验表明,乙嘧酚的残留量随时间延长而降低,消解动态曲线符合一级动力学方程,在黄瓜和土壤中的半衰期分别为3.5和9.9 d,属于易降解性农药化合物。乙嘧酚在黄瓜中消解速率高于其在土壤中的消解速率,这可能是由于黄瓜生长稀释作用导致的。 相似文献
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五氯硝基苯在土壤中的降解 总被引：10，自引：1，他引：9
研究了在控制条件下,ＰＣＮＢ在土壤中的降解规律及影响因素。结果表明,土壤中ＰＣＮＢ降解符合一级反应动力学关系。土壤中微生物对ＰＣＮＢ降解过程有强化作用,使未灭菌土壤中ＰＣＮＢ降解反应表观活化能降低,反映了生物降解的特点;在４℃－３０℃范围内,随着温度升高对微生物激活作用的增强,从而使ＰＣＮＢ降解速率加快。 相似文献
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为明确磁铁矿（Fe3O4）与生物炭对厌氧土壤中六氯苯（HCB）还原脱氯降解的影响及其机理,首先制备并表征了纳米Fe3O4、生物炭及纳米Fe3O4/生物炭复合材料,采用红壤性水稻土的泥浆进行厌氧培养试验,分析反应体系的pH、Eh、吸附态和溶解态Fe(II)与HCB脱氯降解过程之间的内在关系。结果发现,灭菌对照处理的HCB脱氯降解作用很弱,表明HCB还原脱氯主要在微生物的作用下进行;添加生物炭可通过降低土壤的酸性、增强反应体系的还原性且促进生成吸附态Fe(II)而加速HCB还原脱氯降解;纳米Fe3O4促进HCB还原脱氯的效果较生物炭更强,主要归因于添加纳米Fe3O4使反应体系中生成更多的吸附态Fe(II);纳米Fe3O4/生物炭复合材料促进HCB还原脱氯的效果较纳米Fe3O4更强,是因为Fe3O4/生物炭复合材料的比表面积更大且纳米Fe3O4的分散性更好,更有利于反应体系中的电子传递过程。因此,与纳米Fe3O4和生物炭相比,纳米Fe3O4/生物炭复合材料是一种更加理想的HCB污染土壤的修复剂。 相似文献
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(一)红壤性水稻土中铁、锰的含量以淀积层最高,潜育层最低。铁、锰在土层中的分化程度,随土壤发育的程度而增加;锰的分化趋势,较铁更为明显。(二)能被氢醌还原的锰量,占全锰中的很大百分数,最高者可达70%,而能被氢醌还原的铁量,不超过全铁量的0.5%。能与EDTA形成络合物的锰量,也较铁量为高。(三)土壤经交互干湿处理以后,酸溶性和易于还原的铁、锰数量都大大降低,说明脱水作用可使铁、锰的活动性减低。(四)作者根据试验结果而认为,锰对氧化还原条件的感应较为灵敏,而铁则对酸碱条件较为敏感,这对于水稻土剖面中铁、锰的移动和分化具有一定意义。铁、锰的移动程度,在一定程度上可作为水稻土发育程度的一个指标。 相似文献
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The association of cobalt with easily reducible manganese in some acidic permanent grassland soils 总被引：2，自引：0，他引：2
S. C. JARVIS 《European Journal of Soil Science》1984,35(3):431-438
The association of cobalt with manganese oxides was examined in some surface and sub-soils from areas of permanent grassland in England. Hydroquinone (0.2% in ammonium acetate at pH 7.0) was used to extract easily reducible Mn oxides from the soils. Two sequential extractions with this reagent removed significant proportions of the total Co along with the Mn; no significant amounts of iron were extracted. Mn-rich iron concretions were isolated from two of the soils and these contained from 230 to 880 μg g?1 Co. Approximately 30% of the Co in the concretions was dissolved by two sequential extractions with hydroquinone with concurrent release of considerable amounts of Mn, but, as with the soils, not of Fe. The concretions contained 20–41 mg g?1 Mn and 62–171 mg g?1 Fe that were soluble in acidified H2O2. It was concluded that significant proportions of the Co in soils is associated with Mn oxides, and will show the same sensitivity to changes in acidity and redox potential as Mn. 相似文献
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Guohong Qiu Qian Li Ying Yu Xionghan Feng Wenfeng Tan Fan Liu 《Journal of Soils and Sediments》2011,11(8):1323-1333
Purpose
Sulfur is distributed widely in soils and sediments. Sulfide oxidation causes acid mine wastewater, toxicity, and corrosion. Manganese oxide minerals usually affect the migration, transformation, and fate of sulfur. To understand the oxidation behaviors of S2− and influence factors, reaction process and kinetics were investigated by using different manganese oxides. 相似文献13.
W. R. Fischer 《植物养料与土壤学杂志》1983,146(5):611-622
Theoretical Considerations of the reductive dissolution of iron(III) oxides At the case of equilibrium, the extent of reductive dissolution of iron(III) oxides can be obtained by the Nernst equation. At a given pH, the maximum Fe2+ concentration depends on the standard potential Eo of the system, which decreases with increasing stability of the oxide. Crystal imperfections as well as increasing surface area lead to an increase of the equilibrium Fe2+ concentration, whereas the influence of ionic replacement cannot be determined in general. The formation of stable Fe2+ complexes or of solid Fe2+ compounds results in a higher extent of reduction. From theoretical calculations it is concluded, that, for the bacterial reduction of iron oxides, the electron transfer between donor and Fe(III) precedes the protolytic dissolution of the oxide. 相似文献
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黄土高原旱地连续施用锰肥的土壤效应研究 总被引：1，自引：0，他引：1
采用连续浸提形态分级方法，研究了连续施用锰肥17a后锰的土壤化学特性变化。结果表明：经过长期连续施用锰肥，土壤全锰和DTPA—Mn含量增加不多。土壤DTPA—Mn含量随试验时间的延长呈增加趋势，施锰土壤有效锰提高不多，土壤DTPA—Mn含量只增加了0．4～1．7mgkg^-1。土壤中的锰主要以矿物态存在，占土壤全锰含量的比例为87．3％～91.8％。碳酸盐态、氧化锰态和紧结有机态锰占全锰的比例相当，土壤中各形态锰按含量大致呈矿物态〉碳酸盐态〉氧化锰态〉紧结有机态〉松结有机态〉交换态的顺序。施入土壤的锰肥有91．1％～98．6％进入碳酸盐结合态、氧化锰结合态、紧结有机态和矿物态，只有很少一部分仍留在有效态锰库中。交换态和松结有机态锰对土壤锰的有效性起着主要作用，可以反映土壤锰的供给状况，碳酸盐态和紧结有机态锰不能反映土壤锰的有效性。 相似文献
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Yu. N. Vodyanitskii 《Eurasian Soil Science》2009,42(10):1170-1178
The relatively low hydrolyzing capacity of Mn(II) leads to the formation of oxides rather than hydroxides of this element
in soils. The formation of vernadite, birnessite, todorokite, and lithiophorite was recently proved in soils. Vernadite with
an Fe admixture and Mn-containing iron minerals, i.e., ferroxyhyte, ferrihydrite, and magnetite, were also found. Fe-vernadite
and Mn-ferroxyhyte are the most abundant in soils. Manganese oxidogenesis is the most intensely pronounced in the soils of
steppe and forest-steppe zones, in which the assemblage of Mn-containing minerals is wider than in taiga soils. Carbonates
are able to inhibit the development of Mn oxidogenesis. The bulk of Mn compounds are confined to the silt rather than to the
clay fraction, since manganese oxides are negatively charged in the pH interval typical of the bulk of soils. Manganese oxides
are able to retain heavy metals, i.e., Co, Ni, Zn, and others. The active participation of Mn oxides in Cr(III) oxidation
raises its mobility and toxicity. Manganese oxides may favor humus formation by taking part in phenol oxidation. 相似文献
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本文选取江西鹰潭红壤、云南金墩红壤和河南封丘潮土,研究了农田土壤中三氯生(TCS)在有无锰氧化物下的降解过程,考察锰氧化物浓度和有机酸种类及浓度对TCS降解率的影响,并通过高效液相–飞行时间质谱仪分析TCS的降解产物,探讨TCS在土壤中被活性锰氧化物氧化降解的过程。结果表明:锰氧化物在3种不同类型土壤中均具有不同程度的TCS去除能力,水土比4︰1条件下,5 g/L的MnO2在酸性土壤(江西鹰潭红壤)中对TCS的氧化能力最强,云南金墩红壤土壤次之,这说明锰氧化物的氧化能力与土壤pH呈负相关性。同时TCS的降解率随着土壤中锰氧化物的浓度增加而增加,当土壤中锰氧化物的浓度升高到50 g/L时,TCS在8 h内的降解率达到81%,其一级反应动力学常数与锰氧化物浓度之间具有线性相关性。土壤中小分子有机酸能够影响TCS的降解效率,其中高浓度草酸和柠檬酸对TCS的降解具有明显抑制作用;而酒石酸则相反。此外,在反应过程中检测到TCS聚合形成的二聚体产物,并在此基础上提出了氧化转化路径。以上结果为理解TCS在土壤中的衰减和转化提供了新的视野,也为氯酚类污染场地修复提供了理论支撑。 相似文献
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Influence of pH on the redox chemistry of metal (hydr)oxides and organic matter in paddy soils 总被引：1，自引：0，他引：1
Yunyu Pan Gerwin F. Koopmans Luc T. C. Bonten Jing Song Yongming Luo Erwin J. M. Temminghoff Rob N. J. Comans 《Journal of Soils and Sediments》2014,14(10):1713-1726
Purpose
The primary purpose of this study was to determine how flooding and draining cycles affect the redox chemistry of metal (hydr)oxides and organic matter in paddy soils and how the pH influences these processes. Our secondary purpose was to determine to what extent a geochemical thermodynamic equilibrium model can be used to predict the solubility of Mn and Fe during flooding and draining cycles in paddy soils.Material and methods
We performed a carefully designed column experiment with two paddy soils with similar soil properties but contrasting pH. We monitored the redox potential (Eh) continuously and took soil solution samples regularly at four depths along the soil profile during two successive flooding and drainage cycles. To determine dominant mineral phases of Mn and Fe under equilibrium conditions, stability diagrams of Mn and Fe were constructed as a function of Eh and pH. Geochemical equilibrium model calculations were performed to identify Mn and Fe solubility-controlling minerals and to compare predicted total dissolved concentrations with their measured values.Results and discussion
Flooding led to strong Eh gradients in the columns of both soils. In the acidic soil, pH increased with decreasing Eh and vice versa, whereas pH in the alkaline soil was buffered by CaCO3. In the acidic soil, Mn and Fe solubility increased during flooding due to reductive dissolution of their (hydr)oxides and decreased during drainage because of re-oxidation. In the alkaline soil, Mn and Fe solubility did not increase during flooding due to Mn(II) and Fe(II) precipitation as MnCO3, FeCO3, and FeS. The predicted levels of soluble Mn and Fe in the acidic soil were much higher than their measured values, but predictions and measurements were rather similar in the alkaline soil. This difference is likely due to kinetically limited reductive dissolution of Mn and Fe (hydr)oxides in the acidic soil. During flooding, the solubility of dissolved organic matter increased in both soils, probably because of reductive dissolution of Fe (hydr)oxides and the observed increase in pH.Conclusions
Under alternating flooding and draining conditions, the pH greatly affected Mn and Fe solubility via influencing either reductive dissolution or carbonate formation. Comparison between measurements and geochemical equilibrium model predictions revealed that reductive dissolution of Mn and Fe (hydr)oxides was kinetically limited in the acidic soil. Therefore, when applying such models to systems with changing redox conditions, such rate-limiting reactions should be parameterized and implemented to enable more accurate predictions of Mn and Fe solubility. 相似文献18.
Theodor Weichelt 《植物养料与土壤学杂志》1981,144(6):557-564
Oxidation of ?unalterated”?, methylated and hydrogenated lignin in the presence of SiO2 and hydroquinone (1,4-dihydroxybenzene) Under the conditions choosen, which were similar to those in soils, peats and composts, the oxidation by hydroquinone and its (aut-) oxidation products was generelly greater on the methylable than on the hydrogenable structures of lignin. Especially phenolic and enolic hydroxy as well as aldehyde groups, but also single aliphatic double bonds in propene side chains, phenyl cumarone systems, stilbenoide structures as well as such conjugated to aldehyde and ceto groups forced the O2-absorption on lignin. 相似文献
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Haojie Cui Fan Liu Xionghan Feng Wenfeng Tan Ming Kuang Wang 《Journal of Soils and Sediments》2010,10(8):1540-1547
Purpose
Todorokite is one common manganese oxide in soils and sediments and is commonly formed from layered Na-buserite. Aging processes can alter the physicochemical properties of freshly formed Na-buserite in natural environments. However, it is not clear whether and how aging affects the formation of todorokites. In the present paper, Na-buserite with aging treatment was employed to prepare todorokite at atmospheric pressure to investigate the effects of aging treatment of Na-buserite on the formation of todorokite.Materials and methods
Four aged Na-buserite samples, which are produced through oxidation of Mn2+ in concentrated NaOH medium by O2 with aging for 3, 6, 9, and 12 months, were employed to investigate the effects of aging processes on the transformation from Na-buserite to todorokite by Mg2+-templating reaction at atmospheric pressure. The manganese oxides were examined using X-ray diffraction (XRD), elemental analysis, determinations of the average manganese oxidation number, infrared spectroscopy (IR), and transmission electron microscopy (TEM).Results and discussion
The XRD, IR, and elemental analyses indicate that aging treatment can alter the substructure of the freshly synthesized Na-buserite. During the aging process, some of the Mn(III) may migrate into the interlayer region or disproportionate to form Mn2+ and Mn4+ from the layer of Na-buserite and the concomitant formation of layer vacancies. The interlayer Mn3+ or Mn2+ occupied above or below the layer vacancy sites and become corner-sharing octahedral. XRD analyses and TEM clearly show that the transformation from Na-buserite to todorokite was promoted by aging treatments. The alterations of substructure of aged Na-buserites can promote the rearrangement of manganese to construct a tunnel structure during the transformation from layered manganese oxides to tunnel-structure todorokite at atmospheric pressure.Conclusions
The transformation from Na-buserite to todorokite was promoted by aging treatments at atmospheric pressure, and it is more suitable to explore the origination of natural todorokite in Earth surface environments using aged layered manganese oxides. 相似文献20.
STUDIES ON SOIL COPPER 总被引：11，自引：0，他引：11
Adsorption isotherms were determined for the specific adsorption of copper by soils and soil constituents. Adsorption was found to conform to the Langmuir equation. The Langmuir constants, a (adsorption maximum) and b (bonding term), were calculated. Soils were found to have specific adsorption maxima at pH 5.5 of between 340 and 5780 μg g?1, and a multiple regression analysis revealed that organic matter and free manganese oxides were the dominant constituents contributing towards specific adsorption. Adsorption maxima for soil constituents followed the order manganese oxides > organic matter > iron oxides > clay minerals, which supported the findings for whole soils. The cation exchange capacities (non-specific adsorption) of the test soils were found to be far greater than the specific adsorption maxima. However, evidence suggests that, for the relatively small amounts of copper normally present in soils, specific adsorption is the more important process in controlling the concentration of copper in the soil solution. 相似文献