首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 15 毫秒
1.
Formation and properties of amorphous clay constituents in soils of the temperate-humid climate region A review of literature and of some own work was given on formation and properties of amorphous clay constituents which occur along with crystalline clay minerals in soils. By that the importance of soil amorphous material with respect to pedologic-agricultural and social-environmental problems was tried to emphasize. At the beginning some clarification of the different terms used for inorganic amorphous clay constituents and a sort of difinition of the different kinds of amorphous materials seemed to be evident. Then, the occurence and the formation of amorphous material in soils of the temperate-humid climate region was commentated. As a result of this it was stated that amorphous clay constituents occur mainly as coatings on negatively charged surfaces of crystalline layer silicates. From the grouping of amorphous substances around negatively charged cores (layer silicates or AlIV-cores in allophanic soils, respectively) it was deduced that the organisation of amorphous clay constituents and allophanes as well as synthetic aluminosilicates might be due to an unique structural principle, which was tried to explain more detailed. The methods used for determination of amorphous materials, especially allophanes, were discussed. Since the determination of amorphous clay constituents by chemical dissolution techniques is ambiguous with respect to soils containing different weathering stages of crystalline layer silicates as well, some suggestions were made for characterizing amorphous substances in soils by cation exchange and anion adsorption properties. Finally the importance of exchange-reactions caused by specific adsorption of ions and molecules (e.g. nutrients and pesticides) was indicated. Furthermore, the possibility was mentioned that harmful environmental substances might be bound (neutralized) and waste nutrients might be recycled by specific adsorption on amorphous soil constituents.  相似文献   

2.
Abstract

Characteristics of Brown Forest soils developed under different bio-climatic conditions from low to high eleyations in the Kinki District were studied with special reference to their pedogenetic processes. The Brown Forest soils at high elevations were characterized by a lower bulk density, higher capacities to adsorb organic matter, phosphate, and moisture, which were correlated with the ratio of the amorphous content to the clay content (the value of the ratio of (Feo + Alo)/clay), as compared to those at low elevations. Considering the fact that the value of the (Feo + Alo)/clay ratio was not correlated with the volcanic glass index, the formation of an amorphous fraction at high elevations was considered to proceed according to the following mechanism.

Low temperature at high elevations (above 700 m) may retard the crystallization of oxide minerals. The amorphous oxides with variable positive charge thus formed may adsorb organic matter, confering a darker color and high moisture and high phosphate retention capacities to the subsoil. Adsorbed organic matter stabilizes these amorphous oxides, thus enhancing the amorphous properties and inhibiting crystallization. A1 translocation due to the weak podzolization may contribute to the increase of the content of amorphous materials.

Characterization of the B horizons in forest soils in Japan, in terms of the values of the ratios of (Feo + Alo)/clay, (Fed-Feo)/Fet, and Alo/Ald, (CEC -ECEQ/CEC and STPT-ZPC, suggested that forest soils might be classified into four groups.  相似文献   

3.
Towada Ando soils consisted of five soils—Towada-a (1,000 years old), Towada-b (2,000 years old), Chuseri (4,000 years old), Nanbu (8,600 years old), and Ninokura soils (10,000 years Amorphous clay materials of these soils taken at different localities were studied by the combined use of selective dissolution and differential infrared spectroscopy, X-ray analysis, electron microscopy, etc.

The main clay minerals of Towada-a soils, present-day soils, were montmorillonite-vermic-ulite chloritic intergrades and opaline silica, or these minerals and allophane in the humus horizons, and allophane in the non-humus ones. Towada-b soils overlain by the Towada-a soils showed the clay mineralogical constituents similar to those of Towada-a soils. However, allophane was one of the main clay minerals in all the humus horizons as well as non-humus ones. The main clay minerals of Chuseri soils were allophane and layer silicates consisting chiefly of chloritic intergrades and chlorite in the humus horizons, and allophane in the non-humus ones. Opaline silica was present in minor amounts in the humus horizons of Chuseri soils, but nearly absent in Nanbu and Ninokura soils.

There were remarkable differences in the clay mineralogical composition of Nanbu and Ninokura soils with differences of their environmental conditions. Allophane and imogolite Were dominant in the clay fractions of both humus and non-humus horizons of very shallowly buried Nanbu soil which was subjected to the strong leaching process. Allophane was the main clay mineral of deeply buried Nanbu and Ninokura soils which showed the absence of notable accumulation of bases and silica. On the contrary, halloysite with a small amount of siliceous amorphous material appeared in very deeply buried Nanbu and Ninokura soils where bases and silica were distinctly accumulated. The amounts of halloysite in the clay fractions were larger in the humus horizons than non-humus ones, and in Ninokura soil than Nanbu soil.

Soil age, soil organic matter, and depositional overburden of tephras were observed to be conspicuous among various factors relating to the weathering of amorphous clay materials in Towada Ando soils.  相似文献   

4.
Chemical and mineralogical properties of brown podzolic soils, brown earths, a podzol, and an Andept have been studied with particular reference to the kinds and distribution of amorphous materials. In addition to pyrophosphate extractable (Fe + Al)/per cent clay, brown podzolic soils can be distinguished from brown earths by Fe-oxalate/Fe-dithionite and Fe-pyrophosphate/Fe-dithionite ratios, fluoride reactivity, and the presence of intergrade 2:1-2:2 and smectite-like clay minerals in surface horizons. Significant amounts of amorphous alumino-silicates resembling allophane were found in the Bs horizons of the brown podzolic soils, particularly those on igneous rocks. These amounts are sufficiently large to suggest the recognition of an Andic sub-group of brown podzolic soils in England and Wales.  相似文献   

5.
Physical, chemical and mineralogical properties were determined for six profiles in and west of the Great Rift Valley in Kenya. Data include morphology, information on gross composition of horizons (organic carbon, cation exchange capacities, extractable cations, etc.), and detailed characterization of the clay fractions by means of transmission electron microscopy, X-ray diffraction, infrared spectroscopy and additional techniques.The three least weathered profiles (Nos. 1–3 of Table I) have morphologies typical of Andepts but lack certain other characteristics common to such soils. Their clay fractions were largely amorphous to X-rays and consisted mainly of poorly ordered siliceous Feoxides with virtually no allophane. All of the clays contained halloysite. The peralkaline nature of the ash parent-material seems responsible for the clay mineralogy of the soils which differs from that generally found in Andepts. The high proportions of iron in the amorphous materials depart from the composition widely reported for such soils. One distinctive feature was the presence of pantelleritic trachyte, found in ash from a number of sites in addition to those of the profiles.How the six profiles may best be classified is an open question. None of the profiles qualifies as Andept. Nor would they be included in the proposed order of Andisols as presently defined. Modifications of the definition of Andisols so as to include some of these soils would seem desirable.  相似文献   

6.
Permafrost-affected palevye (pale) soils of Central Yakutia are developed from mantle calcareous deposits of different textures and are characterized by the common mica-chloritic association of clay minerals with a higher content of chlorite in comparison with the soils developed from mantle loams and loess-like loams in the European part of Russia. In the pale soils, the distribution of clay minerals in the profile has an even pattern in the loamy variants and a differentiated pattern typical of podzols in the loamy sandy variants. Data on the chemical extracts and Mössbauer spectroscopy indicate that the iron in the pale soils is mainly fixed in silicate minerals. The content of nonsilicate iron represented by the amorphous and weakly crystallized compounds in the pale soils is relatively low. The humus-accumulative horizon in these soils is close to the gray-humus (soddy) AY horizon according to its acid-base characteristics (the soil pH and the degree of base saturation) despite the presence of exchangeable sodium and the shallow occurrence of the calcareous horizon.  相似文献   

7.
The role of the mineralogy of the clay fraction and the physicochemical properties of alluvial soils in the floodplain of the Iput River and its tributary the Buldynka River (in the region of the settlement of Starye Bobovichi in Bryansk oblast) in the distribution and immobilization of radioactive isotope 137Cs from the atmospheric fallout after the Chernobyl accident was studied. The soils had a sandy texture; a significant variation in the content of amorphous iron oxides (0.1–0.77%) and labile manganese (11.2–193 mg/kg), the cation exchange capacity (6.1–54.2 meq/100 g soil), and the base saturation (29–100%) was common; an appreciable content of X-ray amorphous mineral substances in the clay fraction (<1 μm) enriched with organic carbon (7.7–13.1%); the predominance of trioctahedral hydromicas (Me=50%) in the clay fraction; and the presence of fine-disperse quartz and lepidocrocite. The specific activity of the 137Cs in the clay fraction of the moderately and strongly contaminated layers increased with the increasing portion of smectite formations and (or) hydromicas. On the whole, the presence of the clay fraction favored a decrease in the 137Cs mobility (the correlation between its content and that of exchangeable cesium was r=?0.608, n=17). However, the portion of exchangeable radiocesium (extracted with 1 M CH3COONH4, 1:10) had a tendency toward an increase with increasing content of hydromicas in the clay fraction. Thus, the minerals of this group were a potential source of exchangeable 137Cs in the soils. The significant role of amorphous and mobile iron forms in the immobilization and migration of radiocesium in the secondary contaminated horizons of the alluvial soils was revealed.  相似文献   

8.
Quantitative mineralogical composition of the clay fractions of two red soil (Alfisol) profiles developed on gneissic rocks in Mysore, India, is discussed in relation to the genesis of these soils. Data on the mineralogy of their silt and sand fractions are also presented. Both the silt and clay fractions are kaolinitic and contain considerable amorphous material. A possible weathering sequence of transformation of the minerals, with probable mechanisms involved, is suggested.  相似文献   

9.
The mineralogy of the clay fraction from basaltic soils in the Galilee, Israel, has been studied by X-ray and differential thermal analysis techniques, supplemented by electron-micrographs and chemical determinations. The mineralogical composition of the clay was greatly influenced by the amount of rainfall. In SE Galilee, where rainfall is 400–550 mm/annum, the dominant clay mineral is montmorillonite, with kaolinite as the second most important component. With increasing rainfall the amount of montmorillonite in the clay falls, and the amount of amorphous oxides of Fe and Al increases. In N and NE Galilee, rainfall is 550–700 mm/annum and the major part of the clay is composed of kaolinite or halloysite, quartz, and amorphous oxides of Fe and Al. The decrease in the amount of montmorillonite with increasing rainfall is explained by decomposition to kaolinite and amorphous oxides.  相似文献   

10.
Zhu  Meng  Hu  Xuefeng  Tu  Chen  Luo  Yongming  Yang  Ruyi  Zhou  Shoubiao  Cheng  Nannan  Rylott  Elizabeth L. 《Journal of Soils and Sediments》2020,20(2):763-774
Purpose

The mobility of arsenic (As) in soils is fundamentally affected by the clay mineral fraction and its composition. Diphenylarsinic acid (DPAA) is an organoarsenic contaminant derived from chemical warfare agents. Understanding how DPAA interacts with soil clay mineral fractions will enhance understanding of the mobility and transformation of DPAA in the soil-water environment. The objective of this study was to investigate the speciation and sorption structure of DPAA in the clay mineral fractions.

Materials and methods

Twelve soils were collected from nine Chinese cities which known as chemical weapons burial sites and artificially contaminated with DPAA. A sequential extraction procedure (SEP) was employed to elucidate the speciation of DPAA in the clay mineral fractions of soils. Pearson’s correlation analysis was used to derive the relationship between DPAA sorption and the selected physicochemical properties of the clay mineral fractions. Extended X-ray absorption fine structure (EXAFS) LIII-edge As was measured using the beamline BL14W1 at Shanghai Synchrotron Radiation Facility (SSRF) to identify the coordination environment of DPAA in clay mineral fractions.

Results and discussion

The SEP results showed that DPAA predominantly existed as specifically fraction (18.3–52.8%). A considerable amount of DPAA was also released from non-specifically fraction (8.2–46.7%) and the dissolution of amorphous, poorly crystalline, and well-crystallized Fe/Al (hydr)oxides (20.1–46.2%). A combination of Pearson’s correlation analysis and SEP study demonstrated that amorphous and poorly crystalline Fe (hydr)oxides contributed most to DPAA sorption in the clay mineral fractions of soils. The EXAFS results further demonstrated that DPAA formed inner-sphere complexes on Fe (hydr)oxides, with As-Fe distances of 3.18–3.25 Å. It is likely that the steric hindrance caused by phenyl substitution and hence the instability of DPAA/Fe complexes explain why a substantial amount of DPAA presented as weakly bound forms.

Conclusions

DPAA in clay mineral fractions predominantly existed as specifically, amorphous, poorly crystalline, and crystallized Fe/Al (hydr)oxides associated fractions. Amorphous/poorly crystalline Fe rather than total Fe contributed more to DPAA sorption and DPAA formed inner-sphere complexes on Fe (hydr)oxides.

  相似文献   

11.
刘智杰  董雪  张志毅  黄丽 《土壤》2017,49(4):795-802
以湖北省九宫山的4种垂直地带性土壤为对象,研究其剖面层次的黏土矿物组合和铁、铝氧化物的特征,揭示山地土壤中黏土矿物的变化特点。结果表明,随海拔升高,土壤中黏土矿物类型从以高岭石为主,逐渐变为以14.0?矿物、伊利石及三水铝石为主,有从1︰1型向2︰1型矿物过渡的趋势;不同层次的土壤中黏土矿物类型和相对含量变化明显;土壤随垂直高程的升高,其中游离态铁、铝减小,非晶形和络合态铁、铝增加,各种形态铁、铝氧化物的总量也增加。  相似文献   

12.
《CATENA》1987,14(4):359-368
Clay formation in soils was studied in four landscapes of different ages in Lanzarote (Canary Islands). Landscape IVB is about 250 years old, IVA subrecent, III early young pleistocene, and landscape I, late tertiary. The soils have developed from basic to ultrabasic pyroclastic fall deposits or basalt.Clay formation in soils of landscape IVB is in an initial stage having a clay content of 1–2 kg/m2, whereas in landscape IVA 30–40 kg/m2 and in landscape III 100–200 kg clay/m2 are accumulated. In polygenetic soils of landscape I more than 3000 kg clay/m2 can be found. In the youngest soils IVB, smectite is the most prominent clay mineral, whereas IVA-soils are dominated by “amorphous” clay. The clay fraction in older soils contains illite, smectite as well as kaolinite in smaller quantities.The chemical composition of the clay fraction of soils with different ages changes significantly according to the mineral composition.  相似文献   

13.
Robert Brinkman 《Geoderma》1977,17(2):111-144
Extensive areas of periodically wet, acid soils in Bangladesh have a seasonally fluctuating pH of the surface horizon and evidence for net clay loss. Morphological, chemical, mineralogical and other data mainly on a typical profile of these surface-water gley soils indicate a clay loss of some 1.5 kg/dm' ; alteration of smectite to a soil chlorite, interlayered material with trapped ferrous iron; the consequent drop in C.E.C. of the clay fraction; and the presence of amorphous silica. The data were used to reconstruct a sequence of three soil forming processes: Vertisol formation, then argilluviation, followed by ferrolysis.Ferrolysis involves, in the wet season: reduction producing ferrous iron, which displaces part of the exchangeable basic cations and aluminium; leaching of bases and part of the aluminium; and interlayer formation by the remaining aluminium while some exchangeable ferrous iron is trapped in the interlayers. In the dry season, oxidation of exchangeable ferrous iron produces exchangeable hydrogen, part of which attacks the clay minerals and is neutralized by liberation of Al, Mg and other ions from the clay structure. Part of the silica remaining from the clay structure is leached out in the next wet season, part accumulates in amorphous form. In soils long used for paddy cultivation, man has concentrated the ferrolysis process in the ploughed layer by the formation of a slowly permeable ploughpan causing strong reduction only in the surface horizon.The hydromorphic albic horizon over more clayey material is indicative of the dominant process in surface-water gley soils. This sequum could usefully have a more important place in soil classification than it has at present, e.g. at great group level.  相似文献   

14.
The clay mineral association,oxides of clay fraction and surface charge properties of 7 soils,which are developed from granite,located at different altitudesof the Tianbao Mountains were studied.Results indicate that with the increase in altitude,1) the weathering process and desilicification of soil clay minerals became weaker,whereas the leaching depotassication and the formation process of hydroxy-aluminum interlayer got stronger;2)the contents of amorphous and complex aluminum and iron,and the activity of aluminum and iron oxides for soil clay fraction increased;and 3) the amount of variable negarive charge,anion exchange capacity and the values of PZC and PZNC also increased.The activity of aluminum and iron oxides,the accumulation of aluminum,and surface charge characteristics and their relation to clay oxides of the vertical zone soils were observed and recorded.  相似文献   

15.
The effects of urea concentration, soil moisture content, period of storage of soil samples, temperature and toluene on the urease activity of fifteen Trinidad soils were investigated. From the multiple regression analysis of clay content, organic carbon, CEC and amorphous Fe and Al and the urease activity of the soils, it was found that the urease activity in the presence of toluene was largely associated with the clay-organic matter complex whereas in the absence of toluene it was associated with the organic matter of the soils.  相似文献   

16.
Abstract

In nineteen surface horizons of red Mediterranean soils from various locations of Greece, phosphorus (P) sorption experiments were conducted and the sorption characteristics were studied in relation to soil properties. Phosphate sorption data were fitted both to the Langmuir and Freundlich equations. From these equations, the following P sorption parameters were determined from the Freundlich equation, X = ACn, the parameters A (the phosphate sorbed at C = 1 mg P/L), n (the P sorption intensity), the P sorption index (PS = X/log C) and maximum P sorption (Xmfr). From the Langmuir equation, C/X = 1/KXm + C/Xm, the parameters K (showing the bonding energy), maximum P sorption (Xmla), the quantity of P adsorbed at a standard concentration of 0.2 mg P/L (P0.2), and P maximum buffering capacity (PMBC). The Freundlich parameter A was strongly correlated to the clay and sesquioxides ("free”; iron and aluminum oxides and amorphous iron oxides) content. Seventy‐four percent of the variance of this parameter was explained by clay and “free”; iron (Fe) content. The Freundlich parameter n was significantly correlated with pH and amorphous iron oxides content, while 52% of its variance was explained by amorphous Fe and dithionite extrac‐table aluminum (Al). The P sorption maxima calculated from the Freundlich equation were in general lower than those calculated by the Langmuir equation. Both these parameters were strongly correlated with clay and more slightly with sesquioxides content. About 50% of their variance was explained by clay content of the soils. The P sorption index was strongly correlated with the clay content and less strongly with dithionite‐extractable Fe and Al. The P‐buffering capacity calculated from the data of Langmuir equation was also strongly correlated with these two parameters. In addition, clay content and dithionite‐extractable Fe and Al were well correlated to the amounts of P required to obtain an equilibrium concentration of 0.2 mg P/L while 61% of the variation of this parameter was explained by the clay and the dithionite‐extractable Fe content. From these findings, it seems that for the red Mediterranean soils from Greece, P sorption is affected by clay content and iron and aluminum oxide contents.  相似文献   

17.
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   

18.
FLUORIDE ADSORPTION BY ILLINOIS SOILS   总被引：8，自引：0，他引：8  
Fourteen surface and 6 subsurface horizons of Illinois soils adsorbed significant amounts of F? with release of OH?. At low concentrations, adsorption was described by both Langmuir and Freundlich isotherms. The calculated Langmuir adsorption capacities were related to pH, clay, organic carbon, and amorphous aluminum contents. Two soils with different gross chemical properties behaved in essentially the same manner, with adsorption maxima occuring between pH 5.5 and 6.5. The similarity between adsorption at different pH values for the soils and those for bauxite, allophane and synthesized ‘soil chlorite’, and the lack of adsorption maxima between pH 5.5 and 6.5 for pure kaolinite and montmorillonite, suggest that F? adsorption in the soils is due primarily to the presence of amorphous aluminum oxyhydroxides which are common weathering products in these soils.  相似文献   

19.
许冀泉  杨德涌 《土壤学报》1964,12(3):275-285
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。  相似文献   

20.
土壤组分对广东省酸性水稻土磷吸附参数的影响   总被引：9，自引：2，他引：7  
Soil components affecting phosphate sorption parameters were studied using acid paddy soils derived from basalt, granite, sand-shale and the Pearl River Delta sediments, respectively, in Guangdong Province.For each soil, seven 2.50 g subsamples were equilibrated with 50 mL 0.02 mol L-1 (pH=7.0) of KCl containing 0, 5, 10, 15, 25, 50 and 100 ng P kg-1, respectively, in order to derive P sorption parameters (P sorption maximum, P sorption intensity factor and maximum buffer capacity) by Langmuir isotherm equation. It was shown that the main soil components influencing phosphate sorption maximum (Xm) included soil clay, pH,amorphous iron oxide (Feo) and amorphous aluminum oxide (Alo), with their effects in the order of Alo ＞Feo ＞ pH ＞ clay. Among these components, pH had a negative effect, and the others had a positive effect.Organic matter (OM) was the only soil component influencing P sorption intensity factor (K). The main components influencing maximum phosphate buffer capacity (MBC) consisted of soil clay, OM, pH, Feo and Alo, with their effects in the order of Alo ＞ OM ＞ pH ＞ Feo ＞ clay. Path analysis indicated that among the components with positive effects on maximum phosphate buffer capacity (MBC), the effect was in the order of Alo ＞ Feo ＞ Clay, while among the components with negative effects, OM ＞ pH. OM played an important role in mobilizing phosphate in acid paddy soils mainly through decreasing the sorption intensity of phosphate by soil particles.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号