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1.
Phosphate sorption and desorption in soils are markedly influenced by iron oxides, although little is known on how the common iron oxides differ in their behaviour towards added phosphate. In this study, we investigated phosphate sorption and desorption in the clay fractions of 12 Terre Rosse that ranged widely in Fe oxide content, had very low contents of oxalate-extractable Fe oxides and different hematite/goethite ratios. Phosphate sorption at an equilibrium concentration of 1 mg P 1?1 was correlated with the goethite but not with the hematite content of the clay fractions. When phosphate was desorbed by electro-ultrafiltration, the difference in desorption half-time between untreated and deferrified clays was positively correlated with the goethite but not with the hematite content. These results suggest that goethite is more active than hematite in phosphate sorption and retention by soils. 相似文献
2.
华中南部某些土壤针铁矿的形态 总被引:3,自引:0,他引:3
The morphologies of goethites in latosol, red soils, yellow-brown soil and the paddy soils developed from red soils were studied in comparison with the morphology of synthetic goethite by means of the X-ray diffraction, transmission electron microscopy and energy dispersive X-ray analysis. The synthetic goethite displayed acicular particles elongated in the c-direction. The goethites in the latosol, red soils and yellow-brown soil were platy particles stretched in two directions or isodimensional particles, and those in the paddy soils from red soils were acicular, short columnar, platy or isodimensional particles. Various morphologies of the goethites probably suggested their different dominant crystal faces, surface charge distribution and surface adsorption characteristics. 相似文献
3.
The morphologies of goethites in latosol,red soils,yellow-brown soil and the paddy soils developed from red soils were studied in comparison with the morphology of synthetic goethite by means of the X-ray diffration,transmission electron microscopy and energy dispersive X-ray analysis.The synthetic goethite displayed acicular particles elongated in the c-direction.The goethites in the latosol,red soils and yellowbrown soil were platy particles stretched in two directions or isodimensional particles,and those in the paddy soils from red soils were acicular,short columnar,palty or isodimensional particles,Various morphologies of the goethites probably suggested their different dominant crystal faces,surface charge distribution and surface adsorption characteristics. 相似文献
4.
The iron oxides of soils of two river terrace sequences in Spain which show an increasing degree of redness with age were studied. Clay fractions contained only small amounts of oxalate-extractable Fe. Goethite and hematite, the only crystalline Fe-oxides identified, were determined quantitatively by X-ray diffraction (XRD) after concentrating the Fe-oxides by boiling in NaOH and subtracting the step-counted diffractogram of the deferrated clay from that of the non-deferrated clay, obtaining thus a “pure” Fe-oxide diffractogram. EDTA extracted hematite preferentially to goethite as is seen by loss of red colour and by XRD. A good correlation was found between the content of hematite in the fine earth and a redness rating based on Munsell notations.In the Guadalquivir River sequence, Fed and Fed/Fet increased with age. The amount of both goethite and hematite formed from silicate-Fe increased with soil age but hematite increased more than goethite, possibly due to the xeric soil environment. Also, goethite increased in crystallinity as indicated by a decrease in XRD line broadening and Feo/Fed ratios. No such trends were found in the Esla River sequence, possibly because the initial alluvium was already highly weathered as shown by high Fed/Fet values (0.8) irrespective of terrace level.Al substitution in goethite calculated from XRD increased with soil age, reflecting the increasing acidity of the soils. Al substitution in hematite was markedly lower. 相似文献
5.
《Communications in Soil Science and Plant Analysis》2012,43(17-18):2367-2381
Abstract The extractant Mehlich‐1 is routinely used in Brazil for determination of soil nutrients, whereas Mehlich‐3 has been suggested as a promising extractor for soil fertility evaluation. Both were used for extraction of molybdenum (Mo) in Brazilian soils with Mo dosage by the KI+H2O2 method. The Langmuir and Freundlich isotherms were used to study soil Mo adsorption. Mehlich‐1 extracted more Mo than Mehlich‐3 in soils with high contents of organic matter, clay, and iron (Fe) oxides. Mehlich‐3 and Mehlich‐1 extractions correlated positively and significantly with amorphous Fe oxides, crystalline Fe oxides, and organic matter. Molybdenum recovering rates correlated to crystalline Fe oxides and clay contents but not to organic matter, pH, and Mo adsorption capacity. Amorphous and crystalline Fe oxides, clay, and organic matter were responsible for most of the Mo adsorption. The Langmuir isotherm described better the Mo adsorption to soil amorphous Fe oxides and organic matter than the Freundlich isotherm. 相似文献
6.
三种铁氧化物的磷吸附解吸特性以及与磷吸附饱和度的关系 总被引:17,自引:0,他引:17
采用三种人工合成铁氧化物(针铁矿、赤铁矿和水铁矿)比较了结晶态和无定形铁氧化物对磷的吸附—解吸特性以及与磷吸附饱和度的关系。结果表明,三种铁氧化物的磷吸附特性均可用Langumir方程来描述,相关系数均大于0.9,达到极显著水平。从磷最大吸附量(Qm)、吸附反应常数(K)和最大缓冲容量(MBC)三项吸附参数综合考虑,水铁矿(无定形)对磷的吸附无论在容量还是强度方面均比结晶态铁氧化物针铁矿和赤铁矿大得多。水铁矿吸附的磷比针铁矿和赤铁矿所吸附的磷更难解吸;水铁矿的大量活性表面并没有表现出增加磷释放的作用。磷吸附饱和度有望作为评价土壤或铁氧化物磷吸附—解吸的强度和容量因子的一个综合指标。 相似文献
7.
浙江省三种红、紫色砂页岩发育土壤的矿物学研究 总被引:6,自引:1,他引:5
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。 相似文献
8.
Juscimar Silva Jaime Wilson Vargas de Mello Massimo Gasparon Walter Ant?nio Pereira Abrah?o 《Water, air, and soil pollution》2012,223(9):5707-5717
Dissimilatory iron-reducing bacteria play a fundamental role in catalysing the redox transformations that ultimately control the mobility of As in anoxic environments, a process also controlled by the presence of competing anions. In this study, we investigated the decoupling of As from loaded Al and Fe (hydr)oxides by competing anions in the presence of iron-reducing bacteria. Hematite, goethite, ferrihydrite, gibbsite and three aluminium-substituted goethites (AlGts) were synthesised and loaded with arsenate, followed by anaerobic incubation with different phosphate or carbonate-containing media in the presence of catalytic iron-reducing bacteria. Soluble Al, As, Fe and P contents were measured in aliquots by inductively coupled plasma optical emission spectrometry following periodical sampling. Shewanella putrefaciens cells were able to utilise both non-crystalline and crystalline Fe (hydr)oxides as electron acceptors, releasing Fe and As into solution. Phosphate and carbonate affected the Fe bioreduction, probably due to the precipitation of metastable mineral phases and also to phosphate-induced stabilisation on the hydroxide surfaces. Phosphate precipitation acted as a sink for As, thus limiting its mobilisation. The highest fraction of desorbed As by phosphate was observed for gibbsite, followed by AlGts. Similarly, gibbsite showed significant amounts of arsenate displaced by carbonate. In spite of its low crystallinity, ferrihydrite was the most efficient compound in retaining arsenate, possibly due to As co-precipitation. This study provides new insight into the management of As-contaminated soils and sediments containing Al-goethites and gibbsite, where the Fe activity may be too low to co-precipitate As-bearing vivianite. Thus, the dynamics of As(V) in flooded soils are significant in agriculture and environmental management. 相似文献
9.
海南岛北部玄武岩上土壤发生研究Ⅱ.铁氧化物特征 总被引:2,自引:5,他引:2
研究了海南岛北部玄武岩上发育的不同风化成土年代土壤系列的铁氧化物特征。研究表明,随风化成土时间增加,土壤发生过程中形成的游离铁(Fed)以及铁游离度(Fed/Fet)增大,铁活化度(Feo/Fed)降低。穆斯堡尔谱分析显示风化成土时间从9×104a、64×104a至 181× 104a,土壤黏粒中形成的赤铁矿含量占铁氧化物的比例从16%、25%增至 48%。风化成土时间越短,土壤中针铁矿结晶程度越差。X-射线衍射结果表明土壤细土和黏粒中赤铁矿含量与风化成土时间呈正比增加。同时,土壤有磁铁矿含量减少、磁赤铁矿增加的趋势。 相似文献
10.
Phosphate sorption isotherms for samples of the A- and upper B-horizons of Alfisols situated on a sequence of terraces of the River Guadalquivir, southern Spain, showed that phosphate sorbed at an equilibrium concentration of 0.3 μg P ml?1 was correlated with several soil properties. Crystalline Fe-oxides (goethite and hematite) appeared to be the most important P-sorbing components of the soil samples. Sorption was highly correlated with percent clay and with dithionite soluble Fe. This last property was as good a property to predict sorption as the specific surface of crystalline Fe-oxides (which was estimated by line profile analysis of the X-ray diffractograms), probably because the range of surface areas for goethite and hematite was relatively narrow in the samples and because of the limited accuracy of the method of line profile analysis.Well drained and imperfectly drained soils differed little in sorption properties. In imperfectly drained, hematite-free soils, chroma was correlated with sorption. This is promising for it would allow rapid field estimation of sorption.The sorption maximum, calculated from the fitted Langmuir isotherm, was about 1.7 μmol P m?2 of Fe-oxides, a value similar to those reported in the literature for natural and synthetic oxides. 相似文献
11.
Properties and distribution of iron oxides and their association with minor elements in the soils of south-western Australia 总被引:4,自引:0,他引:4
Iron oxides from 39 soils derived from various parent materials in south-western Australia have been studied using a variety of techniques. Goethite and hematite were the only two Fe oxides present. The goethite/(goethite+hematite) ratio ranged from 0.18 to 1.0, and was highest in soils on acidic igneous rocks, decreasing for soils on alluvial and mafic parent materials. In a few soils derived from acid rocks only goethite was present. The redness rating of soils increased linearly with increasing amount of hematite. Al substitution in goethite ranged from 13 to 35 mol%, with higher values for soils on acid igneous rocks (median value = 26 mol%) than for soils on mafic (19 mol%) and alluvial (17 mol%) parent materials. Substitution of A1 in hematite ranged from 4 to 23 mol%, and was greatest in soils on mafic parent materials (median value = 12 mol% A1). A1 substitution in hematite was about half of that in associated goethite. The dehydroxylation temperature for goethite increased linearly with increasing A1 substitution. Goethite and hematite had similar crystal sizes (c. 20 nm), and both were in the form of irregular plates. Dissolution with 1 M HCl of iron oxides concentrated from the soils by 5 M NaOH digestion could be described both by the Cube Root Law and by Kabai's equation. Only one straight line was obtained for the dissolution data using Kabai's equation for samples containing both goethite and hematite, in contrast to the results of other workers. Major proportions of the Co, Cr, Cu, Mn, Ni and Zn in the soils were concentrated with the iron oxides, and the dissolution kinetics of these elements indicate that some may be present in the structure of the iron oxides. 相似文献
12.
We studied the spatial distribution of the amount and types of Fe oxides in a Ferric Acrisol having a red-yellow mottled horizon. Red mottles contain hematite and goethite; yellow mottles have goethite but in amounts markedly smaller than those of the contiguous red mottles. We think that reductive dissolution caused the disappearance of the hematite and part of the goethite in the yellow mottles. This is supported by the experimental dissolution of the iron oxides of the clay fractions: hematite dissolved, on the average, at a rate twice of that of goethite. 相似文献
13.
柠檬酸对三种人工合成氧化铁磷吸附特性的影响 总被引:1,自引:0,他引:1
试验采用了3种人工合成的氧化铁为材料,研究了氧化铁对磷的吸附以及柠檬酸对氧化铁磷吸附特性的影响。结果表明:3种人工合成的氧化铁对磷的吸附特性及柠檬酸对氧化铁吸附磷的影响都可用Langumir方程来描述,都达到了极显著水平。从磷的最大吸附量(Sm)、吸附反应常数(K)和最大缓冲容量(MBC)来看,未加入柠檬酸时,水铁矿对磷的吸附在容量和强度方面均为最高;而在加入柠檬酸时,3种人工合成的氧化铁对磷的吸附能力的顺序并无差别,水铁矿和针铁矿的磷Sm和MBC要比赤铁矿大很多。 相似文献
14.
15.
16.
R. L. PARFITT 《European Journal of Soil Science》1989,40(2):359-369
The reactions of phosphate with natural samples of allophane, ferrihydrite, hematite and goethite were measured for up to 30 d. The amount of phosphate sorbed on allophane showed the biggest increase with time whereas the amount sorbed on goethite showed the least increase with time. The total amount of phosphate sorbed either at high levels of phosphate addition or after 10 d followed the order hematite < goethite < ferrihydrite < allophane and was probably related to the specific surface. Si was desorbed as phosphate was adsorbed on the minerals.
The reactions of phosphate on allophane involved rapid, strong adsorption, probably at defect sites, followed by weaker adsorption, followed, probably, by disruption of the allophane structure together with precipitation of aluminium phosphates. Previous suggestions either of diffusive penetration of phosphate into surfaces or about the formation of aluminium phosphate coatings, are unlikely to hold for allophane, if all the Al is at the surface and if the structure can be ruptured.
The reactions of phosphate with iron oxides involved a rapid, strong ligand exchange, followed by weaker ligand exchange, and, probably, by a relatively slow penetration at defect sites and pores. Highly crystalline goethite has virtually no slow reaction and therefore solid-state diffusion of phosphate does not readily occur. The extent of phosphate uptake during the slow penetration reactions probably depends on the degree of crystallinity or porosity of iron oxides.
The most reactive adsorbents, such as allophane, ferrihydrite and Al-humus complexes do not have planar surfaces, and this needs to be considered when modelling phosphate reactions. 相似文献
The reactions of phosphate on allophane involved rapid, strong adsorption, probably at defect sites, followed by weaker adsorption, followed, probably, by disruption of the allophane structure together with precipitation of aluminium phosphates. Previous suggestions either of diffusive penetration of phosphate into surfaces or about the formation of aluminium phosphate coatings, are unlikely to hold for allophane, if all the Al is at the surface and if the structure can be ruptured.
The reactions of phosphate with iron oxides involved a rapid, strong ligand exchange, followed by weaker ligand exchange, and, probably, by a relatively slow penetration at defect sites and pores. Highly crystalline goethite has virtually no slow reaction and therefore solid-state diffusion of phosphate does not readily occur. The extent of phosphate uptake during the slow penetration reactions probably depends on the degree of crystallinity or porosity of iron oxides.
The most reactive adsorbents, such as allophane, ferrihydrite and Al-humus complexes do not have planar surfaces, and this needs to be considered when modelling phosphate reactions. 相似文献
17.
海南岛土壤粘粒矿物特征与土壤系统分类 总被引:6,自引:0,他引:6
研究了海南岛不同母质土壤的粘粒矿物特征:都含有较多的高岭石,其中玄武岩发育土壤粘粒中高岭石最多,但其结晶最差。片岩和紫色砂岩发育土壤含相当多的水云母,粘粒部分水云母含量高达40%~45%,石灰岩发育土壤水云母含量亦较高,达20%~37%,此类水云母属二八面体型的水化白云母。玄武岩和花岗岩发育的“湿润”土壤粘粒中针铁矿与赤铁矿的含量之比为(3~4):1,而花岗岩发育的“常湿”土壤粘粒中只有针铁矿,不见赤铁矿存在,证明土壤中氧化铁矿物的类型是土壤湿润状况的反应,在中国土壤系统分类中可以用来区分“湿润”和“常湿”土壤的一个指标。 相似文献
18.
Soil organic carbon (SOC) storage and turnover is influenced by interactions between organic matter and the mineral soil fraction. However, the influence of clay content and type on SOC turnover rates remains unclear, particularly in tropical soils under natural vegetation. We examined the lability of SOC in tropical soils with contrasting clay mineralogy (kaolinite, smectite, allophane and Al-rich chlorite). Soil was sampled from A horizons at six sites in humid tropical areas of Ghana, Malaysian Borneo and the Solomon Islands and separated into fractions above and below 250 μm by wet sieving. Basal soil respiration rates were determined from bulk soils and soil fractions. Substrate induced respiration rates were determined from soil fractions. SOC lability was significantly influenced by clay mineralogy, but not by clay content when compared across contrasting clay minerals. The lability of SOC was lowest in the allophanic and chloritic soil, higher in the kaolinitic soils and highest in the smectitic soil. Our results contrast with conventional concepts of the greater capacity of smectite than of kaolinite to stabilize SOC. Contents of dithionite-citrate-bicarbonate extractable Fe and Al were inversely related to SOC lability when compared across soil types. A stronger inverse correlation between content of ammonium-oxalate extractable Fe and SOC lability was found when considering the kaolinitic soils only and we conclude that the content of active Fe (hydr-) oxides controls SOC stabilization in the kaolinitic soils. Our results suggest that the validity of predictive models of SOC turnover in tropical soils would be improved by the inclusion of soil types and contents of Fe and Al (hydr-) oxides. 相似文献
19.
Phosphorus adsorption and desorption in undisturbed samples from subtropical soils under conventional tillage or no‐tillage
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Jessé R. Fink Alberto V. Inda Jovana Bavaresco Vidal Barrón José Torrent Cimélio Bayer 《植物养料与土壤学杂志》2016,179(2):198-205
The dynamics of P in soil is greatly influenced by the adsorption of phosphate onto Fe‐oxides. Access of phosphate to the surface of these minerals depends on the degree of soil aggregation, which in turn is influenced by soil management system. The primary purpose of this work was to investigate P adsorption and desorption in undisturbed and disturbed soil samples from an Ultisol (Rhodic Paleudult) and an Oxisol (Humic Hapludox) under conventional tillage (CT) or no‐tillage (NT). Phosphorus adsorption and desorption in undisturbed soil was studied by using a continuous flux system containing a P solution for adsorption measurements or deionized water and Mehlich‐I solution for desorption measurements. The Oxisol, which had higher clay, hematite, and goethite contents than the Ultisol, exhibited the highest maximum P adsorption capacity (Pmax) values in disturbed samples. Also, the disturbed Ultisol samples had lower Pmax values under NT than under CT. The undisturbed soil samples exhibited no significant differences in P adsorption between soil management systems, but P desorption was more marked under NT than under CT. The samples of Oxisol under NT exhibited lower P adsorption rates and higher P desorption rates than the CT samples of the same soil. The decreased P adsorption in undisturbed samples relative to disturbed samples suggests that P adsorption is influenced by physical properties of soil. 相似文献
20.
The purpose of the study was to determine the effect of boron (B)-permeated goethite on soil B fractionation and the availability of this B fraction to rape seedlings (Brassica napus L.). For this purpose, goethite and two kinds of B-permeated goethite were synthesized and their processes in soil were simulated. Plant availability of B adsorbed or occluded on goethite was investigated with rape seedling. Results found that both ad-B-goethite and oc-B-goethite significantly increased the water soluble B (WS-B), specifically adsorbed B (SPA-B), B occluded in amorphous iron (Fe) and aluminum (A1) oxides (AMO-B) and crystalline Fe and Al oxides (CRO-B) content in the soil, compared with ordinary goethite. Also the B-permeated goethites improved B content of the rape seedling and therefore enhanced the rape shoot and root dry weight. Correlation analysis demonstrated that water soluble B (WS-B) plays the most important role in rape B uptake and accumulation, moreover the specifically adsorbed B (SPA-B), nonspecifically adsorbed B (NSA-B), amorphous Fe and A1 oxides (AMO-B) was also significant correlated with the B content or B accumulation of the rape. 相似文献