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1.
应用Ｘ射线衍射和化学分析等手段研究了中南地区几种地带性土壤中的氧化铁类型与钼吸附的关系，结果表明：供试土壤粘粒的氧化铁以晶质氧化铁为主，非晶质氧化铁含量低，砖红壤和赤红壤中的晶质氧化铁全为针铁矿；针铁矿的平均晶粒大小一般比赤铁矿的小，而比表面积却比赤铁矿的大；针铁矿型氧化铁全为针铁矿；针铁矿的平均晶粒大小一般比赤铁矿的小，而经表面积却比赤铁矿的大；针铁矿型氧化铁的钼吸附量比针－赤混合型氧化铁的高， 相似文献
2.
Fe(Ⅱ)存在条件下氧化铁-高岭石复合物的形成与转化 总被引：3，自引：1，他引：2
氧化铁-高岭石复合物是我国南方土壤的重要组分,也是影响这些土壤理化性质的主要因子。本文以Fe(Ⅱ)为添加剂,研究了晶质氧化铁-高岭石复合物的形成与转化过程及其影响因素。结果表明,Fe(Ⅱ)可加速晶质氧化铁-高岭石复合物的形成,在一定程度上克服了高岭石对晶质氧化铁形成的抑制作用。当Fe(Ⅱ)/Fe(Ⅲ)摩尔比(R)在0.04~0.06时,Fe(Ⅱ)可加速纤铁矿、针铁矿、赤铁矿-高岭石复合物的形成;当R≥0.1时,可快速形成磁铁矿-高岭石复合物。在温度50~60℃、pH5~6条件下,Fe(Ⅱ)可加速纤铁矿、针铁矿-高岭石复合物的形成;温度80℃及中性附近时,可加速赤铁矿-高岭石复合物的形成;pH9时,则形成了磁铁矿-高岭石复合物。高岭石的存在减弱了Fe(Ⅱ)对晶质氧化铁形成的催化效果,也可影响产物类型和结晶形貌。上述结果可为自然环境中氧化铁以及氧化铁-高岭石复合物的形成转化过程提供重要参考。 相似文献
3.
水稻土中铁氧化物的厌氧还原及其对微生物过程的影响 总被引：20，自引：3，他引：20
采用厌氧泥浆恒温培养实验 ,测定了添加 6种外源氧化铁后土壤中Fe(Ⅱ )和Fe(Ⅲ )浓度的变化 ,探讨了不同氧化铁的还原能力及其对土壤产H2 、产CO2 、产乙酸和产CH4 过程的影响。结果表明 :无定形氧化铁和纤铁矿易于被还原 ,两者的最终还原程度大体相同 ,但无定形氧化铁存在还原滞后现象 ;针铁矿、赤铁矿、Al取代针铁矿和Al取代赤铁矿难以被还原 ,表现出与对照相同的还原特征 ;铁还原能导致土壤中H2 和乙酸稳态浓度的降低 ,有效抑制了甲烷产生 ;添加Fe(OH) 3和纤铁矿后 ,Fe(Ⅲ )还原占总电子传递的贡献率由对照的 1 8.3 0 %增至 63 .3 2 %和 46.90 % ,而形成甲烷的电子传递贡献率由对照的 80 .92 %降至 3 5 .85 %和 5 2 .3 2 % ,Fe(Ⅲ )还原对电子的竞争消耗 ,使土壤产甲烷过程被强烈抑制 相似文献
4.
本文研究了三种土壤(砖红壤、红壤和黄棕壤)、高岭土和两种合成氧化铁(无定形氧化铁和针铁矿)对亚硒酸盐的吸附和解吸,讨论了亚硒酸盐的吸附特征,以及土壤中氧化铁对亚硒酸盐吸附和解吸的影响。 相似文献
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6.
土壤在淹水条件下 ,氧化铁是土壤中主要的电子接受者之一。本文利用抗坏血酸和针铁矿模拟研究了土壤中的有机还原性物质与氧化铁之间的反应。结果表明 :在抗坏血酸与针铁矿作用的过程中 ,由于溶液中质子被消耗 ,溶液的pH上升 ,质子的消耗量随着抗坏血酸加入量的增加而增加。质子消耗的动力学曲线表明 ,抗坏血酸与针铁矿之间的作用属于异相反应 ,达到平衡所需要的时间较长。在反应的初期 ,二价铁的还原溶出速率很慢 ,在较长的时间内溶液中二价铁浓度不发生变化。pH对抗坏血酸与针铁矿之间的反应有影响 ,pH上升 ,反应速率受抑制 ,pH下降 ,反应速率加快。从不同pH条件下的抗坏血酸的峰电位的测定结果推断 ,pH对抗坏血酸与针铁矿反应的影响可能通过影响针铁矿表面化学性质来实现的。 相似文献
7.
本文研究了三种土壤(砖红壤、红壤和黄棕壤)、高岭土和两种合成氧化铁(无定形氧化铁和针铁矿)对亚硒酸盐的吸附和解吸作用。讨论了亚硒酸盐的吸附特征,以及土壤中氧化铁对亚硒酸盐吸附和解吸的影响,根据实验资料与吸附等温方程式的拟合情况,作者认为以Freundlich和Langmuir公式为宜。此外,供试样品对亚硒酸盐的吸附和解吸结果表明,Se的吸附量随Se的添加量的增加而增加,但由于矿物组成各异,吸附量的差异显著。其吸附量的大小顺序为:无定形氧化铁>针铁矿>砖红壤>红壤>黄棕壤>高岭土;而被吸附Se的解吸能力则是高岭土>黄棕壤>红壤>砖红壤>针铁矿>无定形氧化铁。实验结果还表明,在各种矿物组成中,亚硒酸盐的吸附和解吸受氧化铁的影响很明显,三个土壤样品的吸附等温线都表现出氧化铁在初始阶段对亚硒酸盐吸附快而强烈的特征,而在去除氧化铁以后,这一特征也随之消失,硒的吸附量显著降低,而解吸率则明显上升。 相似文献
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9.
本研究选取代表性层状硅酸盐蒙脱石，两种代表性氧化铁(水铁矿、针铁矿)，合成蒙脱石-水铁矿、蒙脱石-针铁矿二元复合体，通过宏观吸附以及光谱学技术探究钨(WO42-)在蒙脱石-氧化铁复合体上的吸附行为和潜在机制。结果表明：氧化铁紧密覆盖在蒙脱石表面，使表面颗粒更加细小；钨的吸附量随pH升高而降低，3种吸附剂对钨吸附量大小顺序为：蒙脱石-水铁矿>蒙脱石-针铁矿>蒙脱石；原位红外光谱实验表明，钨在蒙脱石表面主要以外圈络合物形式存在，而在蒙脱石-氧化铁复合体上形成内圈络合物(Fe-O-W)，且在低pH时，形成聚合态钨；X-射线光电子能谱进一步表明，针铁矿和水铁矿表面铁羟基参与了钨的络合反应。本研究证实，氧化铁覆盖不仅增大蒙脱石对钨的吸附量，而且使钨由外圈络合物形态转变为内圈络合态，进一步生成聚合态钨。研究结果对预测钨在土壤中的迁移转化、生物有效性和归宿有重要指导意义。 相似文献
10.
应用穆斯堡尔谱和X射线法研究红壤性水稻土的氧化铁矿物 总被引：1，自引：1，他引：1
应用穆斯堡尔谱和X射线法分析研究红壤性水稻土的氧化铁矿物,研究结果表明,红壤性水稻土的氧化铁矿物组成、特性及其形成转化与起源土壤具有明显的差异。水稻土的成土条件不利于赤铁矿的形成。红壤的粘粒氧化铁矿物以赤铁矿和高铝替代(>20摩尔%)的针铁矿为主。经淹水种稻后,赤铁矿逐渐被转化为低铝替代的针铁矿或其它形态氧化铁。渗育型水稻土P层的赤铁矿含量比相应的母土低,其针铁矿铝替代量较其它水型的水稻土高。而潴育型水稻土W层和潜育型水稻土G层粘粒氧化铁矿物均以针铁矿为主,其铝同晶替代量低(<15摩尔%),且颗粒细小,结晶度较低。这些结果反映了水稻土的成土条件和发生特点,同时对水稻土发生分类具有重要的意义。 相似文献
11.
Electric charge characteristics of horizons of Ando (B) and Red-Yellow B soils and weathered pumices
The electric charge characteristics of five Ando (B) and two Red-Yellow B horizon soils and two weathered pumices were studied by measuring the retention of NH4+ and Cl? at different pH values and NH4Cl concentrations. The magnitude of their negative charge (CEC; meq/100g) was dependent on pH and NH4Cl concentration (C; m) as represented by a regression equation: log CEC =apH +blog C +c. The values of the coefficient a (0.017 to 0.342), b (0.031 to 0.274) and c (1.41 to ? 1.26) were correlated and depended on the kind of clay minerals present. A similar equation: log AEC =a’ pH +b’ log C+c’ was also found for the positive charge in the Ando soils, but there was little difference in the values of a’(?0.204 to ?0.251), b’(0.181 to 0.253) and c’(2.06 to 2.46) between the soils. It was shown that the equations generally hold for soils with constant and/or variable charges and describe adsorption equilibria in which NH4+ and H+, and Cl? and OH? compete for cation- and anionexchange sites, respectively. The significance and utility of the coefficients is discussed. 相似文献
12.
土壤胶体中氧化物表面性质的初步研究 总被引：1，自引：0，他引：1
我们以蒙脱石为对照,测定了以水合氧化物型表面为主的试样四个方面的表面性质:电荷零点(ZPC)、滴定曲线、羟基释放量及不同pH条件下对NH4+和Cl-的吸附。结果表明,在pH 4—9范围内,氧化物型表面提供可变正电荷1—8 meq/100g,提供可变负电荷3—15meq/100g;三二氧化物使土壤的ZPC升高,而永久负电荷和有机质使土壤的ZPC降低。作为粘土酸,氧化物表面的酸性较弱,其表面质子逐步解离,使滴定曲线不出现突跃。氧化物表面的羟基和水合基密度很高,增加了土壤对离子的专性吸附能力。土壤中常见的氧化物型表面主要来自Fe,Al氧化物及非品质矿物,就它们的化学式而言,主要有Si—OH、Fe—OH及Al—OH,它们可存在于同一土壤中,在土壤常见的pH范围内,具有低ZPC的Si—OH亚表面提供可变负电荷,具有高ZPC的Fe—OH和Al—OH亚表面提供可变正电荷。 相似文献
13.
Experiments were conducted with two typical paddy soils from China and a vermiculite to study the influence of iron oxides on the fixation and release of ammonium. Removing iron oxides, especially amorphous iron oxides, from the soils favoured the release of non-exchangeable NH4-N and stimulated the fixation of NH4-N in the presence of added (NH4)2SO4. Addition of artificial goethite and hematite to the original soils or to the soils free of iron oxides reduced the fixation of NH4+-ions. This effect was also observed with vermiculite. We conclude that the coating of clay minerals with iron oxides has an impact on the diffusion of NH4+-ions into and out of the interlayers of the clay minerals. The reduction and dissolution of iron oxides induced by low redox potential (Eh) after flooding of paddy soils is assumed to be an important mechanism controlling NH4+-fixation in paddy fields. 相似文献
14.
《Communications in Soil Science and Plant Analysis》2012,43(9-10):1417-1430
Abstract Clinoptilolite, a zeolite mineral with a high cation exchange capacity and surface area, has ion‐exchange properties that can be utilized to adsorb NH4 +, protecting it from losses during composting of N‐rich animal manures. Ammonium adsorption by the natural zeolite clinoptilolite was studied to ascertain the effectiveness of the zeolite as an NH4 + adsorbent at pH 4, 5, 6, and 7. The NH4 + adsorption data were fitted to the one‐ and two‐surface Langmuir, Freundlich, and Temkin isotherms. All models described the NH4 +adsorption data successfully (r2≥0.939). The one‐surface Langmuir, Freundlich, and Temkin were converted to pH‐dependent forms. The amount of NH4 + adsorbed increased as pH and initial NH4 +concentration increased. From the one‐surface Langmuir isotherm, the NH4 +adsorption capacity (Xm) of the zeolite increased linearly with pH (r2=0.994), and was estimated to be 9,660 mg N kg‐1 at pH4, 11,220 mg N kg‐1 at pH 5, 12,720 mg N kg‐1 at pH 6, and 13,830 mg N kg‐1 at pH 7. The adsorption of higher amounts of NH4 +with increasing pH and initial NH4 +concentration is an important characteristic of the zeolite that can be beneficial to minimizing N‐losses via NH3volatilization during composting of N‐rich animal manures. 相似文献
15.
The electric charge characteristics of four Ando soils (A1 and μA1) and a Chernozemic soil (Ap) were studied by measuring retention of NH4+ and Cl– at different pH values and NH4Cl concentrations. No positive charge appeared in the Ando soils at pH values 5 to 8.5 except for one containing allophane and imogolite. The magnitude of their negative charge (CEC; meq/l00g soil) was dependent on pH and NH4Cl concentration (C; N) as represented by a regression equation: log CEC =a pH +b log C +c, where the values of a and b were 0.113–0.342 and 0.101–0.315, respectively. Unlike the Chernozemic soil, Ando soils containing allophane, imogolite, and/or 2:1–2:1:1 layer silicate intergrades and humus showed a marked reduction of cation retention as pH decreased from 7 to 5. This was attributed to the charge characteristics of the clay minerals and to the carboxyl groups in humus being blocked by Al and Fe. 相似文献
16.
《Communications in Soil Science and Plant Analysis》2012,43(11-12):2147-2158
Abstract Selenite adsorption by a variety of oxides consisting of iron (Fe), aluminum (Al), titanium (Ti), manganes (Mn), and silicon (Si), and by two humic acids were investigated in order to grasp selenite behavior and fixation mechanisms in soil. It was found that selenite was apparently adsorbed even by the Mn oxides on which surface negative charge was dominant in normal pH range (pH <4). No selenite adsorption was observed in the silicon dioxide (SiO2) and the two humic acids. A sequential extraction of adsorbed selenite with competitive anions showed the differences of binding force or stability of adsorbed selenite among the minerals. While the goethite fixed selenite strongly, selenite adsorbed on the Mn oxide was easily released to the liquid phase with other anions, such as phosphate. Each mineral had its inherent characteristic in ligand exchange reactions accompanied with selenite sorption. Selenite sorption by the Mn and the Ti oxides resulted in large increase of surface negative charge, while only a little increase in the Fe and Al oxides. Proton consumption with selenite sorption was extremely smaller for the Mn oxide than for the others. 相似文献
17.
Abstract The “Four-plane model” is one of the surface complexation models developed for analyzing the electrostatic charge of synthetic oxides. This model which was applied to the B horizon of Andisols, was equilibrated with an electrolyte solution containing KCl, KNO3, K2SO4 in the concentration range of 0.0033, 0.01, 0.033, 0.1 M, and pH range of 2 to 11. The amounts of NO3 -, Cl-, SO4 2-, and K+ adsorbed were determined from the products remaining in the liquid phase. The increase in the pH value results in the increase of K+ adsorption, and decrease of anion adsorption. The increase in the equilibrium concentration increased both K+ and anion adsorption. The parameters of the model were determined by measurements and the iterative method. The model have a good agreement between calculated and measured values of cation and anion adsorption. Among the anion species, the amount of adsorbed anions was in the order of SO4 2-?Cl->NO3 -. The differences in the degree of adsorption were mainly associated with the differences in the equilibrium constants of surface complexation. The surface complexation of the anions produced a negative charge and increased cation adsorption. The degree of surface complexation was most significant in the K2SO4 solution, and the phenomenon was considered to be important not only for anion adsorption but also for cation adsorption on Andisols. 相似文献
18.
Tobacco plants (Nicotiana tabacum L. cv NC82) were supplied with (NH4)2SO4, or NH4Cl at root‐zone pH of 6.0 and 4.5 in hydroponic culture for 28 days. Dry matter accumulation, total N and C content, and leaf area and number were not affected by the NH4 + source or root‐zone pH. Plants supplied with NH4C1 accumulated up to 1.2 mM Cl g DW‐1, but accumulated 37% less inorganic H2PO4 ‐ and 47% less SO4 2‐ than plants supplied with (NH)2SO4. The large Cl‐ accumulation resulted in NH4C1 –supplied plants having a 31% higher inorganic anion (NO3 ‐, H2, PO4 ‐, SO4 2‐, and Cl‐) charge. This higher inorganic anion charge in the NH4C1‐supplied plants was balanced by a similar increase in K+ charge. Plants supplied with NH4Cl accumulated greater concentrations of Cl‐ in leaves (up to 5.1% of DW) than plants supplied with (NH4)2SO4 (less than ‐% DW). Despite the high Cl‐ concentration of leaves in NH4Cl supplied plants, these plants showed no symptoms of Cl‐ toxicity. This demonstrates that toxicity symptoms are not due solely to an interaction between high Cl‐ concentration in tissue and NH4 + nutrition. The increase in root‐zone acidity to pH 4.5 from 6.0 did not induce toxicity symptoms. 相似文献
19.
Potassium (K) and nitrogen (N) are essential nutrients for plants. Adsorption and desorption in soils affect K+ and NH + 4 availabilities to plants and can be affected by the interaction between the electrical double layers on oppositely charged particles because the interaction can decrease the surface charge density of the particles by neutralization of positive and negative charges. We studied the effect of iron (Fe)/aluminum (Al) hydroxides on desorption of K+ and NH + 4 from soils and kaolinite and proposed desorption mechanisms based on the overlapping of diffuse layers between negatively charged soils and mineral particles and the positively charged Fe/Al hydroxide particles. Our results indicated that the overlapping of diffuse layers of electrical double layers between positively charged Fe/Al hydroxides, as amorphous Al(OH) 3 or Fe(OH) 3 , and negatively charged surfaces from an Ultisol, an Alfisol, and a kaolinite standard caused the effective negative surface charge density on the soils and kaolinite to become less negative. Thus the adsorption affinity of these negatively charged surfaces for K+ and NH + 4 declined as a result of the incorporation of the Fe/Al hydroxides. Consequently, the release of exchangeable K+ and NH +4 from the surfaces of the soils and kaolinite increased with the amount of the Fe/Al hydroxides added. The greater the positive charge on the surfaces of Fe/Al hydroxides, the stronger was the interactive effect between the hydroxides and soils or kaolinite, and thus the more release of K+ and NH + 4 . A decrease in pH led to increased positive surface charge on the Fe/Al hydroxides and enhanced interactive effects between the hydroxides and soils/kaolinite. As a result, more K+ and NH + 4 were desorbed from the soils and kaolinite. This study suggests that the interaction between oppositely charged particles of variable charge soils can enhance the mobility of K+ and NH + 4 in the soils and thus increase their leaching loss. 相似文献
20.
Pawel Wójcik 《Journal of plant nutrition》2013,36(7):1025-1035
The availability of various boron (B) fractions in soil to M.26 apple (Malus spp.) rootstock was examined. The study was carried out in a greenhouse on soils with diverse chemical and physical properties. The following B fractions were determined: (i) B in soil solution, (ii) B non‐specifically adsorbed on soil surface, (iii) B specifically adsorbed on soil colloid surfaces, (iv) B occluded in Mn oxyhydroxides, (v) B occluded in noncrystalline aluminum (Al) and iron (Fe) oxides, (vi) B occluded in crystalline Al and Fe oxides, (vii) B fixed with soil silicates, and (viii) total soil B. In the studied soils there were: 0.07–0.17 mg kg‐1 B in soil solution, 0.01–0.03 mg kg‐1 B non‐specifically adsorbed on soil surface, 0.04–0.08 mg kg‐1 B specifically adsorbed on soil colloid surfaces, 0.28–0.67 mg kg‐1 B occluded in manganese (Mn) oxides, 4.03–17.22 mg kg‐1 B occluded in noncrystalline Al and Fe oxides, 8.93–50.62 mg kg‐1 B occluded in crystalline Al and Fe oxides, 12.2–42.5 mg kg‐1 B fixed with soil silicate, and 52.9–82.2 mg kg‐1 total B. Simple correlation analysis showed positive correlation between B contents in M.26 apple rootstocks and amounts of B in soil solution (r=0.77), B non‐specifically adsorbed on soil colloid surfaces (r=0.65), B specifically adsorbed on soil surface (r=0.76) and B occluded in Mn oxyhydroxides (r=0.77). No relation was found between plant B contents and amounts of B occluded in non‐crystalline and crystalline Al and Fe oxides, B fixed with soil silicates and total B. The results indicated that extraction of B by 0.1 M NH2OH HCl solution adequately represented amounts of B in soil solution, B non‐specifically and specifically adsorbed on soil compound surfaces and B occluded in Mn oxyhydroxides to assess availability of B to apple trees. 相似文献