Composition of iron-manganese concretions from some New Zealand soils

A selection of iron-manganese concretions from five reference soil profiles and a buried loess deposit in New Zealand have been studied. Concretions appear to have developed by the precipitation of amorphous iron and manganese oxides among soil particles. X-ray fluorescence analysis shows that the concentrations of Fe, Mn, Co and Ba in the concretions are generally higher, and those of K, Ca, Si, and Al are generally lower, than in the soil materials surrounding the concretions, whereas Ti, Zn, S, and P show little variation. Other approximate analyses indicate that Cu, Ni, Mo, V, and Pb tend to be concentrated in concretions but for Ga, Zr, Sr, Li, and Rb there was no discernible trend. Electron probe microanalyses of some concretions show that Co and Ba are concentrated in Mn-rich phases rather than Fe-rich phases.Comparison with published results for concretions (Mn nodules) from the ocean floor and the floor of Lake Ontario indicates that, on average, marine concretions have higher Mn, and lower Si and Al concentrations than soil concretions, and that marine concretions have lower Fe concentrations than either Ontario or soil concretions.     

植稻年限对土壤铁锰氧化物的影响

以浙江不同耕作年限水田和旱地为研究对象,探讨了植稻年限对土壤铁锰氧化物的影响,并揭示了水稻土发育过程中铁锰氧化物的剖面运移规律和诊断意义。结果表明:①土壤剖面中,全Fe、游离Fe及全Mn的变异随着种稻时间的延长而增大。种植达到一定年限时,全Fe、全Mn以及游离Fe在土壤剖面下层出现淀积。在各种铁锰氧化物中,对水稻土最具诊断意义的是游离Fe和全Fe。②无定形Fe以及络合态Fe、Mn与有机质呈显著正相关。植稻年限对它们的影响是通过对有机质的影响达到的。     

铁氧化物与土壤表面电荷性质的关系

The relationship between iron oxides and surface charge characteristics in variable charge soils (latosol and red earth) was studied in following three ways.(1)Remove free iron oxides (Fed) and amorphous iron oxides (Feo) from the soils with sodium dithionite and acid ammonium oxalate solution respectively.(2) Add 2% glucose (on the basis of air-dry soil weight) to soils and incubate under submerged condition to activate iron oxides,and then the mixtures are dehydrated and air-dried to age iron oxides.(3) Precipitate various crystalline forms of iron oxides onto kaolinite.The results showed that free iron oxides (Fed) were the chief carrier of variable positive charges.Of which crystalline iron oxides (Fed-Feo) presented mainly as discrete particles in the soils and could only play a role of the carrier of positive charges,and did little influence on negative charges.Whereas the amorphous iron oxides (Feo),which presented mainly fas a coating with a large specific surface area,not only had positive charges,but also blocked the negative charge sites in soils.Submerged incubation activated iron oxides in the soils,and increased the amount of amorphous iron oxides and the degree of activation of iron oxide,which resulted in the increase of positive and negative charges of soils.Dehydration and air-dry aged iron oxides in soils and decreased the amount of amorphous iron oxides and the degree of activation of iron oxide,and also led to the decrease of positive and negative charges.Both the submerged incubation and the dehydration and air-dry had no significant influence on net charges.Precipitation of iron oxides onto kaolinite markedly increased positive charges and decreased negative charges.Amorphous iron oxide having a larger surface area contributed more positive charge sites and blocked more negative charge sites in kaolinite than crystalline goethite.     

波兰喀尔巴阡山麓漂白淋溶土中铁锰结核的分布、形态和化学组成研究

Iron and manganese oxides are common components of soils. They frequently occur in nodules constituting important soil sorbents and play a crucial role in a number of chemical reactions in the soil environment. In addition, the oxides are very sensitive to environmental changes (moisture, pH, Eh) constituting important indicators of soil-forming processes and water movement in the landscape. The objectives of the study were: i) to examine the distribution and size of Fe-Mn nodules in Albeluvisols containing a fragipan horizon; ii) to determine the morphology and chemical composition of the nodules, and iii) to estimate the effect of the fragipan horizon on water movement within the soil profile. An investigation was carried out on five soil profiles containing a fragipan horizon and classified as Fragic Albeluvisols within the Carpathian Foothills in Poland. In the Albeluvisols studied, the maximum concentration of Fe-Mn nodules occurred in the horizon lying directly on the fragipan horizon. This suggests that the pan acts as a natural barrier restricting water infiltration and leads to the seasonal development of a perched water table promoting redox processes. The most common are coarse (1--0.5 mm) and medium (0.5--0.25 mm) irregular Fe-Mn nodules showing a gradual boundary and undifferentiated internal fabric. Eluvial horizons contained also larger amounts of round and dense nodules with a sharp boundary, suggesting frequent oxidation and reduction. The fragipan horizon contained mainly irregular and soft nodules, suggesting longer saturation with water during the year. Concentrations of trace elements (Cu, Zn) and P were higher within Fe-Mn nodules than in the surrounding soil materials, showing that iron and manganese oxides adsorbed and immobilised these elements.     

浙江省三种红、紫色砂页岩发育土壤的矿物学研究

本文用Ｘ射线衍射分析,红外光谱分析、透射电镜及Ｘ射线荧光分析对浙江省三种红、紫色砂页岩发育的红砂土、紫砂土和红紫砂土的矿物进行了分析。     

Influence of iron oxides on cobalt adsorption by soils

Eleven soils from Denmark and Tanzania were extracted with ammonium acetate (controls), EDTA, and dithionite-EDTA (DE) to fractionate iron (and manganese) oxides. The amounts of cobalt adsorbed and acidity desorbed by the extracted soils as well as by two synthetic iron oxides were determined, using 0.85 mM cobalt in 0.2 m NaNO₃.
No significant correlations were found between cobalt adsorption and the contents of extractable manganese or organic matter, presumably because of their low contents. The major part of the cobalt adsorption (by DE-extracted samples) was due to the clay fraction and was associated with the release of approximately one proton per adsorbed Co. The remaining cobalt adsorption was attributed to the iron oxides. This portion of adsorbed cobalt was well described by considering soil iron oxides composed of only two fractions, an EDTA-extractable fraction of high reactivity and a less reactive fraction corresponding to the difference between DE-extractable iron and EDTA-extractable iron. Approximately 1.7 protons were released per Co adsorbed by these iron oxide fractions and by the synthetic iron oxides.
The amounts of cobalt adsorbed by the soil iron oxides were well predicted from the contents and specific surfaces of the two iron oxide fractions together with the specific cobalt adsorption of synthetic iron oxides.     

Ferromanganese concretionary neoformations: A review

Based on the original and published data, the results of studying the properties, composition, genesis, and information significance of ferromanganese concretions in the soils of the taiga, broadleaved forest, and forest-steppe zones are summarized. The role of these neoformations in the field and analytical diagnostics of soils is analyzed. Some regularities of the changes in the chemical composition of ferromanganese concretions as related to the degree of the soil bogging or profile drainage were revealed. Under the regular increase in hydromorphism of the soils, the content of iron increases and that of manganese decreases. In this case, the ratio between the iron and manganese contents extracted by 1 N H₂SO₄ also increases. This ratio was named the coefficient of bogging. This coefficient is used in practice to assess the expediency of drainage of mineral soils. The participation of ferromanganic concretions in the accumulation of macro- and micro-elements is shown. A model experiment has revealed that ferromanganese nodules can be formed during a rather short time (1–2 years).     

Adsorption of cobalt by soil iron oxides at low solution concentration

Abstract

Eleven selected soils from Denmark and Tanzania were treated with ammonium acetate (controls), EDTA, and dithionite‐EDTA (DE) to fractionate iron and (manganese) oxides. The amounts of cobalt adsorbed were determined from a 3 μM equilibrium cobalt solution, corresponding to the cobalt level in natural soil solutions using sodium nitrate (0.2 M) to suppress non‐specific adsorption, by the extracted soils as well as by two synthetic iron oxides.

No significant correlations were found between cobalt adsorption and the contents of organic matter and extractable manganese, presumably due to their low contents in the soils investigated. Close correlations were, however, found between the amounts of cobalt adsorbed, especially fractions thereof, and the contents of iron oxides.

The amounts of cobalt adsorbed by the DE‐ex‐tracted soils, void of iron (and manganese) oxides, were attributed to the clay silicates. The remaining cobalt adsorption, i.e. the difference between cobalt adsorbed by acetate‐extracted and DE‐extracted samples, was attributed to the iron oxides. This portion of adsorbed cobalt was well described by considering soil iron oxides composed of only two fractions, an EDTA‐extractable fraction of high reactivity and a less reactive fraction corresponding to the difference between DE‐extractable iron and EDTA‐extractable iron.

The amounts of cobalt adsorbed by the soil iron oxides were well predicted from the contents and specific surface of the two iron oxide fractions in soil together with the amount of cobalt adsorbed by the synthetic iron oxides.     

江西低丘红壤性水稻土的主要化学特性研究

三个红壤性水稻土的有机质和腐殖质的含量由淹育型水稻土→潴育型水稻土→潜育型水稻土依次逐渐增加,其C/N和H/P比值也顺次增大。它们的粘土矿物组成无明显差异。铁、锰物质在潴育型水稻土剖面中分异最明显,其次为淹育型水稻土;而无定形氧化铁在剖面中变幅最大却是潜育型水稻土;结晶态铁在土壤剖面中分异亦有一定规律,其中潴育型水稻土的指示性土层(W层)的晶胶率(结晶铁/无定形铁)远较其它土层为高,这种变化特性的差异,对区分不同水分作用的水稻土发育类型有一定的特殊意义;土壤络合态铁与土壤有机质含量有关。土壤氧化锰与土壤氧化铁相比虽然含量低,但对土壤氧化还原条件反应更加敏感,所以在土壤剖面中淋移趋势更加明显。     

Formation of bound residues of 8-hydroxybentazon by oxidoreductive catalysts in soil

This study was performed to determine which oxidoreductive catalysts were most efficient in catalyzing the binding of 8-hydroxybentazon to soil humic substances. 8-Hydroxybentazon was completely transformed by an oxidoreductive enzyme, laccase of Myceliophthora thermophila, at pH 3.0-7.0 within 30 min. When abiotic catalysts, manganese(IV), iron(III), and aluminum oxides were used in the same pH range, 8-hydroxybentazon was completely transformed only by manganese(IV) oxide (delta-MnO2), but a relatively small amount of 8-hydroxybentazon was transformed by iron(III) oxide and aluminum oxide. The adsorption of 8-hydroxybentazon in the soil showed an H-type and coincided well with the Langmuir isotherm. To better understand the factors involved in the rapid and strong binding of 8-hydroxybentazon with soil humic substances, 8-hydroxybentazon transformation by oxidoreductive catalysts was studied in various soil conditions: air-dried, preincubated, sterilized, and iron(III) oxide and manganese(IV) oxide free. 8-Hydroxybentazon was completely transformed within 24 h in the decreasing order of preincubated, air-dried, and sterilized soils. However, little transformation was observed in the iron(III) oxide and manganese(IV) oxide free soils. These results suggest that the major catalyst responsible for the rapid and strong binding of 8-hydroxybentazon to soil humic substances is a metal oxide, manganese(IV) oxide, not a soil oxidoreductive enzyme.     

磷的吸附和表面电荷特征及其与华南地区某些土壤矿物的关系

The phosphate adsorption and surface charge characteristics of the tropical and subtropical soils derived from different parent materials in China were determined, and their relations to soil mineralogy were analysed. The results showed that all soil phosphate adsorption curves were well fitted by Freundlich equation and Langmuir equation. The maximum buffering capacity of P ranged from 66 to 9 880 mg kg^-1, with an increasing order of purple soil, skeletal soil, red soil, lateritic red soil, yellow soil and latosol; and the highest value was 149 times the lowest value, which indicated great differences among these soils in phosphate adsorption and supplying characteristics. The pH₀ (zero point of charge) values obtained by salt titration-potential titration varied from 3.03 to 5.49, and the highest value was found in the latosol derived from basalt whereas the lowest value was found in the purple soil. The correlation analysis indicated that the main minerals responsible for phosphate adsorption in the soils were gibbsite, amorphous iron oxide and kaolinite; and the pH₀ was mainly controlled by kaolinite, gibbsite and oxides.     

The association of cobalt with easily reducible manganese in some acidic permanent grassland soils

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.     

Contribution of Iron and Aluminum Oxides to Electrokinetic Characteristics of Variable Charge Soils in Relation to Surface Charge

The contribution of iron and aluminum oxides to electrokinetic characteristics of variable charge soils was studied through determination of electrophoretic mobilities of the red soils treated with either removal of iron oxides or coating of aluminum oxides,and of those deferrated under natural conditions.After removal of the iron oxides,zeta potentials of the latosol and the red earth decreased obviously with a shift of IEP to a lower pH,from 6.4 to 5.3 and 4.1 to 2.4 for the former and the latter,respectively,and the electrokinetic change for the latosol was greater than for the red earth.Zeta potentials of the kaolinite sample increased markedly after coated with iron oxides.The striking effect of iron oxides on electrokinetix properties of the soils was also demonstrated by the electrokinetic differences between the samples from the red and white zones of a plinthitic horizon formed naturally,and between the samples from the gley and bottom horizons of a paddy soil derived from a red earth.The coatings of aluminum oxides on the latosol and the yellow earth made their zeta potentials rise pronouncedly and their IEFs move toward higher pHs,from 6.2 to 6.8 and 4.3 to 5.3 for the former and the latter,respectively.The samples with different particle sizes also exhibited some electrokinetic variation.The experiment showed that the effects of iron and aluminum oxides were closely related to the pH and type of the soils.     

无定形锰氧化物在氮素损失中的作用

Studies have been made,by ^15N-tracer technique on nitrogen loss resulting from adding amorphous manganese oxide to NH4^ -N medium under anaerobic conditions.The fact that the total nitrogen recovery was decreased and that ^15NO2,^15N2O,^15N^14NO,^15NO,^15N2 and ^15N^14N were emitted has proved that,like amorphous iron oxide,amorphous manganese oxide can also act as an electron acceptor in the oxidation of NH4^ -N under anaerobic conditions and give rise to nitrogen loss.This once again illustrates another mechanism by which the loss of ammonium nitrogen in paddy soils is brought about by amorphous iron and manganese oxides.The quantity of nitrogen loss by amorphous manganese oxide increased with an increase in the amount of amorphous manganese oxide added and lessened with time of its aging.The nitrogen loss resulting from amorphous manganese oxide was less than that from amorphous iron oxide.And the nitrogen loss resulting from amorphous manganese oxide was less than that from amorphous iron oxide.And the nitrogen loss by cooperation of amorphous manganese oxide and microorganisms (soil suspension) was larger than that by amorphous manganese oxide alone.In the system,nitrogen loss was associated with the specific surface ares and oxidation-reduction of amorphous manganese oxide.However,their quantitative relationship and the exact reaction processes of nitrogen loss induced by amorphous manganese oxide remain to be further studied.     

Iron oxide and clay minerals and their relation to colours of red and yellow podzolic soils near Sydney,Australia

The iron oxide and clay minerals in some typical red and yellow podzolic soils from New South Wales have been investigated by X-ray diffraction and infra-red spectroscopy. The dominant iron oxide mineral is goethite containing about 13–14 mol % AlOOH, this being the mineral which gives the yellow soils their characteristic colour. The red soils also contain finely divided hematite which masks the colour of the goethite. Lepidocrocite was not detected in any of the soils examined. The dominant clay minerals are kaolinite and dioctahedral interstratified illite-smectite, the latter being more concentrated in the finer clay fractions, especially in soils developed on calcareous greywacke. In the red podzolic soil developed on Ashfield shale, illite-smectite is strongly interlayered with well-ordered aluminous material. Dickite occurs in this soil.     

Distribution of iron and manganese oxides in Haploxeralfs and Rhodoxeralfs and their relation to the degree of soil development and soil colour

The status and the distribution of iron and manganese oxides were studied in six soil profiles from Thrace region (Greece), classified as Rhodoxeralfs and Haploxeralfs. The acid ammonium oxalate and the dithionite-citrate-bicarbonate methods were used to extract the free iron and manganese oxides from the soils. In both great groups the Fed and Mnd values are higher than Feo and Mno values, respectively, indicating that a considerable fraction is present in crystalline form. Both Feo/Fed and Fed-Feo values suggest that, in the study area, Haploxeralfs are less developed soils than Rhodoxeralfs. The manganese oxides present in crystalline forms (Mnd-Mno) were more in Rhodoxeralfs than in Haploxeralfs, suggesting that the crystallinity of manganese oxides increases, with the degree of soil development. Significant correlations were found of Redness Rating to Fed-Feo and to Feo/Fed ratio, positive and negative respectively, leading to the conclusion that soil red colouration increases with the degree of soil development.     

Concretions in typical chernozem,gleyed chernozem-like,and solonetzic chernozem-like soils of the southern Tambov Lowland

A system for the diagnostics of chernozemic soils of the Tambov Lowland based on concretions is proposed for agricultural and reclamation purposes. The relationships between the structure and composition of the carbonate concretions, the long-term water regime of the soils, and the productivity of the crops have been established. The dense concretions in the typical chernozem testify to the depth of the seasonal wetting; the angular-rounded concretions in the deeply gleyed chernozem-like soil, to the upper boundary of the capillary fringe; and the angular concretions with sharp edges and cavities in the gleyic chernozem-like soils, to the groundwater table. In the chernozem-like soils that were waterlogged with bicarbonate-sodium water, the black angular concretions were formed in the solonetzic horizons, while the weakly compacted light-colored ones, in the zone of the capillary fringe. Humic acids were responsible for the color of the dark neoformations, and fulvic acids predominated in the light-colored ones. The appearance of black fine nodules indicated periodic surface water stagnation. Manganese predominantly accumulates in these nodules. The structure of the Mn-Fe concretions in the plow horizon observed at a magnification of 40–50 times has a diagnostic importance. The short-term (2–3 weeks) water stagnation leads to the formation of fine-stratified concretions, and the long-term (up to 1.5 months) stagnation promotes the formation of uniform porous ones. The solonetzic process induced by the bicarbonate-sodium water results in the appearance of mottled concretions.     

中国土壤胶体研究 Ⅵ.西藏高原几种主要土壤的粘土矿物组成和演变

西藏高原突起于我国西南,绝大部分地面的海拔高度在4000米以上,为世界上最高的大高原。它大致在第三纪开始形成,后来曾受第四纪冰川的深刻作用,高山顶部至今仍是冰川的活动场所^[1,2]。高原为昆仑山、唐古拉山、喜马拉雅山和横断山等大山脉所盘踞。     

A NanoSIMS study on the distribution of soil organic matter,iron and manganese in a nodule from a Stagnosol

The development of Stagnosols is the consequence of perched water tables, which induce periodic oxidizing and reducing conditions. These cause the spatial distribution of iron (Fe) and manganese (Mn) between the soil matrix and ferromanganese concretions or nodules. Since oxides of these metals may interact with organic matter, we studied their spatial distribution in bulk material from the Bg horizon of a Stagnosol and in a nodule separated from the horizon. We used wet‐chemical analyses and X‐ray diffractometry together with microscopic techniques and nano‐scale secondary ion mass spectrometry (NanoSIMS), the latter allowing for a submicrometre‐scale spatial resolution. X‐ray diffractometry revealed the presence of quartz, clay minerals, micas and feldspars as the dominant minerals and indicated the presence of lepidocrocite. Relative to the bulk horizon material, the nodule was strongly enriched in organic C (by a factor of 31) and pedogenic (dithionite‐extractable) Fe and Mn (by factors of 2.2 and 62). We selected two regions on a thin section of the nodule for NanoSIMS investigations after studying the element distribution by scanning‐electron microscopy (SEM): one was located in an almost closed pore, the other one along an elongated pore. The NanoSIMS measurements allowed a clearer distinction of Fe‐ and Mn‐accumulation zones than SEM‐EDS. The evaluation of the NanoSIMS measurements by unsupervised classification revealed that zones containing silicates and Mn oxides and the transitional zones between Fe and Mn oxides were particularly enriched in soil organic matter, while, with one exception, the pure Fe‐accumulation zones did not indicate the presence of soil organic matter.