Mineralogical study of weathering products of granodiorite at Shinshiro City (VI)

It was concluded in the previous papers of this series of studies (13, 14) that the principal constituent minerals of the parent granodiorite, that is, plagioclase, biotite and hornblende are, in course of weathering, altered to specific secondary minerals either of layer silicate type or of hydroxide type. Quartz suffers no significant alteration.     

Mineralogical study of weathering products of granodiorite at Shinshiro City (V)

In the foregoing papers (15, 16) of this series of studies, a conspicuous 14 A reflection was found in X-ray diffractograms for the weathered brown and yellow micas, and for the silt and clay fractions. It was thought to be due to “Al-vermiculite”, which has a trioctahedral character but upon chemical and thermal treatments behaves like “dioctahedral analogue of vermiculite” (2). It was also noted that contraction of the reflection to a 10 A sparing is more difficult when the specimen examined is fine in particle size and is taken from a high horizon (16).     

Mineralogical study of weathering products of granodiorite at Shinshiro City (I)

Rock weathering has long been a subject of study for geologists, mineralogists, chemists and soil scientists since the dawn of this century. In methods for investigating rock weathering, three aspects seem to be present. The one is a chemical aspect in which weathering process is considered by comparing chemical composition of fresh parent rock with that of the weathered rock, the difference being attributed to gains or losses of chemica,l elements with respect to a supposed immobile element, usually aluminum. This aspect can elucidate the chemical behaviour of rock, that is, of material as an assemblage of constituent minerals in the environment of weathering. Among many such studies mentioned. PoLYNov's “Cycle of Weathering” (6) is one of the most comprehensive and fruitful acheivements. The second aspect is a mineralogical one, in which interests are directed toward skeletal minerals surviving against severe attacks of weathering. It is commonly observed that some of the original constituent minerals still remain in weathered material after others have been extinguished. The former minerals are more stable than the latter. On the basis of these observations, the sequence of resistantiability or stability to weathering can be determined for many rock forming minerals. GOLDICH's study of rock-weathering (3) is a representative one in this aspect. The third aspect is concerned with clay mineralogy. Primary rock-forming minerals are weathered into very finegrained materials most of which had been believed amorphous until techniques now used in clay mineralogical reserch proved their crystalline state. Besides primary skeletal minerals, weathered materials are now known to consist mainly of both amorphous and crystalline secondary minerals, mostly appearing in minus two micron fraction and being objects of interest in clay mineralogy. Any study of rock weathering hitherto performed stood more or less on the three aspects above mentioned but, all the abovementioned seem to fall into the common tendency of dealing with materials as bulk mass. That is, they were concerned much more with fresh rock versus its weathered end products as a whole rather than with the process or mechanism by which fresh rock changed into weathered material. Thus, in the temperate to subtropical humid region, it is known that, for example, kaolinite minerals, gibbsite, and some of 2: 1 type clay minerals are found in weathered materials of rocks and further that Na, K. Mg. Ca, and Si are leached away, while H, Al, and Fe are concentrated in the weathered products, but it is scarcely understood from what constituent minerals of the parent fresh rock any of the clay minerals now present in the weathered material were derived. Though, a mineralogical or chemical tracing of the courses of decomposing minerals from their initial phases to subsequent modified phases was already pioneered by STEPHEN (8). such a trend is believed, by the author, to be a fourth aspect necessary for further thorough understanding of rock weathering. This way of study may also serve in bridging between experimental data on chemical reactions of specific minerals with reagent solutions on the one hand and observations of mineralogical interrelation of parent minerals to resultant weathering products on the other hand. Granitic rock offers a suitable situation for this fourth aspect because of the ease in picking up mineral grains at various weathering stages due to the coarseness of its constituent minerals and also to its unique mode of physical disintegration.     

Mineralogical study of weathering products of granodiorite at Shinshiro City (II)

In the preceeding paper (1), the general character of the weathering profile of granodiorite indicated that physical weathering was prevailing in the lower two zones and chemical weathering was dominant in the upper zone of the profile. It was also shown that the weathering profile has been developed in a severe chemical environment under oxidizing condition such as that encountered in the subtropical or warm temperate humid climate. The chemical weathering of the constituent minerals of the parent rock and the materials produced from them in such a weathering environment will now be examined. In this paper, the stability or duration of the primary minerals will bestudied.     

Mineralogical variability in weathering microsystems of a granitic outcrop of Galicia (Spain)

Several products of weathering have been studied in a granitic outcrop in Galicia (N.W. Spain). Alteration took place under a humid temperate climate. The various materials and the microsystems in which they occur are: (1) fissures containing gibbsite and/or 1:1 sheet silicates of varying degrees of crystallinity, (2) fissures containing 2:1 sheet silicates of beidellite type, (3) encrustations of siliceous material showing varying degrees of structural order, with or without organic matter, and (4) encrustations of non-crystalline matter composed chiefly of Al, P and Si.The results demonstrate the importance of considering the different microsystems which contribute to the formation of secondary products in a given weathering system.     

老挝南部Antoun地区花岗闪长岩风化壳中常量和稀土元素分布

应用岩石薄片鉴定、X射线粉晶衍射、X射线荧光光谱和ICP-MS等分析方法,研究了热带季风型气候条件下老挝Attapeu省Antoun地区二叠纪花岗闪长岩上发育的砖红土型风化壳矿物组成、常量元素和稀土元素地球化学特征。结果表明,风化产物呈酸性,风化壳表土上形成薄层硅质壳层,表土中石英含量最高、铁氧化物含量低和高岭石含量低,符合典型的灰化土特征。随着风化作用加强,Fe2O3、TiO2和Al2O3出现富集,K2O、Na2O、CaO和MgO出现淋失。石英出现富集原因可能是雨季降水冲刷和酸性水淋溶掉高岭石等黏土矿物,而旱季SiO2含量上升至地表富集形成硅质薄壳缘故。剖面稀土元素分布型式为轻稀土富集型,∑REE在风化壳中部达到最高值318 mg kg-1,剖面上Ce和Eu均呈正异常-负异常-正异常变化趋势,∑REE最高值出现在Ce和Eu负异常和(Fe2+/Fe3+)较高层位,∑REE与Fe2O3显著正相关。REE富集与铁铝氧化物和黏土矿物吸附有关,也与相对还原的酸性环境有关。     

Classifying soils at the ultimate stage of weathering in the tropics

Oxisols cover ≈ 23% of the land surface in the tropics and are utilized extensively for agricultural purposes in the tropical countries. Under the variable input types of agricultural systems practiced locally, some of these soils still appear to have problems in terms of proper soil classification and subsequently hinder attempts to implement sustainable agro‐management protocols. The definition for Oxisols in Soil Survey Staff (1999) indicates that additional input is still required to refine the definition in order to resolve some of the outstanding classification problems. Therefore, the objective of this study is to examine the properties of some Oxisols and closely related soils in order to evaluate the classification of these soils. Soils from Brazil, several countries in Africa, and Malaysia were used in this study. Field observations provided the first indication that some of the presently classified kandi‐Alfisols and kandi‐Ultisols were closer to Oxisols in terms of their properties. Water‐retention differences and apparent CEC of the subsurface horizons also supported this idea. The types of extractable Fe oxides and external specific surface areas of the clay fractions showed that many kandic horizons have surface properties that are similar to the oxic horizons. Micromorphology indicated that the genetic transition from the argillic to the oxic involves a diminishing expression of the argillic. Properties, such as CEC, become dominant. The kandic horizon is therefore inferred as a transition to the oxic horizon. It is proposed that the Oxisols be keyed out based only on the presence of an oxic horizon and an iso–soil temperature regime. The presence of a kandic horizon will be reflected at lower levels in Oxisols. The Oxisols will now be exclusive to the intertropical belt with an iso–soil temperature regime. The geographic extend of the Oxisols would increase and that of kandi‐Alfisols and Ultisols would decrease. A few kandi‐Alfisols and Ultisols in the intertropical area will have low CEC which would fail the weatherable mineral contents. The kandic subgroups of some Alfisols and Ultisols will be transitional between the low (< 16 cmol_c [kg clay]^–1)‐ and high (> 24 cmol_c [kg clay]^–1)‐activity clay soils. The proposed changes to classification will contribute to a better differentiation of the landscape units in the field. Testing of the proposed classification on some Malaysian soils showed that the new definition for Oxisols provides a better basis for the classification of the local soils and the development of meaningful soil‐management groups for plantations.     

Mineralogical changes with depth in a layered Andosol near Bandung, Java (Indonesia)

The mineralogy and some physical and chemical properties of an Andosol developed in four distinct layers of volcanic ash have been investigated. Analytical methods used include X-ray diffraction, transmission electron microscopy, particle-size analyses, infrared spectroscopy, pyrophosphate extracts of C, Al and Fe, and acid-oxalate extracts of Al, Fe and Si. Three buried A horizons in the ash were also dated by the ¹⁴C method. The dates obtained indicate burial of A horizons c. 17700, 14500 and 8600 years B.P., respectively. Halloysite dominates the weathered fraction in the ash older than 17700 B.P., whereas allophane and imogolite with molar A1/Si ratios of 1.7–2.0 are predominant in the younger ash layers. Some kaolinite also occurs in the upper two layers of ash. It is considered possible that the halloysite in the deepest ash layer formed under different climatic conditions from those prevailing at present, rather than due to resilication of allophane under the overburden of ash. The results also demonstrate the mineralogical complexity of soil developed in more than one layer of volcanic ash.     

Diurnal and seasonal water variations of temperature,pH, redox potential and conductivity in gnammas (weathering pits): Implications for chemical weathering

A gnamma or weathering pit is a small-sized cavity sculpted into solid rock which refills with rainwater. This study describes the main hydrological processes in gnammas and the underlying chemical interactions with the environment. Four gnammas developed in a granite tor from central Spain were chosen for monitoring and studying the dynamics of the gnamma–water system. Parameters monitored were air and water temperature, pH, ORP (redox potential), and conductivity. These measurements describe the system dynamics, without the need for special sampling or other potential interferences under low water volumes. Additionally, chemical analyses were carried out to contrast the chemical properties with the chemical composition. As a consequence of water volumes less than 100 L, daily fluctuations tended to cause the largest amplitude changes. Photosynthesis and respiration/putrefaction processes in the gnamma are responsible for daily pH fluctuations up to 4 units, with pH values often greater than 9. ORP generally alternates from positive to negative values as the solution oscillates diurnally between basic and acidic conditions. Conductivity values ∼ 10 μS/cm occur most of the year, with only minor daily oscillations. During dry periods, conductivity increases significantly with maximum values > 400 μS/cm. These high conductivity values reflect atmospheric inputs by summer rainstorms after prolonged dry periods. Therefore, conductivity does not relate directly with chemical species dissolved from the host rock. Silica was the main weathering product of granite dissolution during the year, with highest concentrations (> 200 ppm) in the rainy season. Low Si values measured during the dry season are in accordance with observed precipitation of amorphous silica within the gnamma. Seasonal variations in concentration are also present in Al and Fe as a response to ORP variations and evaporative dynamics, causing mineral dissolution and new mineral precipitation during the year. Relations among the measured parameters are influenced by several factors, including biological processes, temperature effects and water level variations. Factors such as large pH oscillations, basic pH values, acids from biological activity, and alkali cations all increase silicate solubility, thus favoring granite dissolution. Overflow of water during the winter, when the water is chemically enriched, is an effective mechanism to remove weathering products.     

Air oxidation of S(IV) in cloud-water samples

Aerobic oxidation of S(IV) was investigated in cloud-water samples collected at Great Dun Fell,U.K., as part of a wider project into cloud-water chemistry. The rate was found to be first-order in S(IV) concentration, and the reaction rate constant. k_S(IV), was found to vary from 10^–5 to 10^–3 s^–1. The rate constant was highly correlated with H⁺ concentration (pH 3.5 to 6.5) and Fe concentration (<0.02 to=">^–6 mol dm^–3). The aerobic oxidation of S(IV) does not contribute significantly to SO₂ oxidation in clouds at Great Dun Fell, however, the reaction may be of consequence in clouds and fogs at polluted or urban sites with elevated trace metal concentrations. Also, this reaction may be responsible for the oxidation of S(IV) in cloud-water samples during storage.     

Absorption of fission products by plants (Part 5) absorption of gross fission products

Introduction

One of the authors reported in the preceding paper the absorption by plants of unseparated fission products derived from the H-bomb detonated in Spring of 1954 at Bikini-atoll. Since the authors had, thereafter, some amounts of gross fission products which were waste of atomic pile by courtesy of United States Atomic Energy Commission, they began some experiments on the absorption of the gross fission products by plants.     

浙江省县(市)域土地利用效率的时空演变、驱动因素与调控对策

[目的]探究浙江省县(市)域土地利用效率演变与优化机制,为实现土地资源高效优配提供对策和建议.[方法]综合运用SBM-Undesirable模型、熵值法、自然断点法和地理探测器模型,探究2007-2018年浙江省69个县(市)域的土地利用效率演变特征及优化机制.[结果]①浙江省县(市)域土地利用效率演变呈明显的"三阶段...     

花岗岩风化产物中高岭石和埃洛石的粒径分布及其对土壤发生的意义

The kaolins collected from a profile of weathered granite at Yichun County, Jiangxi Province have been subjected to particle size fractionation by the conventional sedimentation method and examined by XRD, SEM and TEM. All of them exhibit a mixture phase of poorly crystallized kaolinites and halloysites (0.7 nm) occurring as the main clay minerals. Electron micrographs reveal that plate kaolinites are the principal constitution in the coarse fraction, and more tubular and curled halloysite (0.7 nm) in the fine fraction. Both of them show normal probability curves in particle size distributions. The ratios of kaolinite and halloysite (0.7 nm) in different size fractions are examined by X-ray diffraction with a series of X-ray patterns characterized by three main peaks at d(001), d(002) and d(020),varying in intensity. Therefore, an index Q_hm expressed as (I_d(001) + I_d(002))/(2×I_d(002)), is designed to indicate relative ratios of the two clay minerals in a number of mixture phases. Because kaolinite and halloysite (0.7 nm) commonly occurred, respectively, in low and medium leaching microenvironment, the index Q_hm, can be used to indicate weathering and pedogenic conditions of a weathering crust.     

Vertical structure of evapotranspiration at a forest site (a case study)

The components of ecosystem evapotranspiration of a Norway spruce forest (Picea abies L.) as well as the vertical structure of canopy evapotranspiration were analyzed with a combination of measurements and models for a case study of 5 days in September 2007. Eddy-covariance and sap flux measurements were performed at several heights within the canopy at the FLUXNET site Waldstein-Weidenbrunnen (DE-Bay) in the Fichtelgebirge mountains in Germany. Within and above canopy fluxes were simulated with two stand-scale models, the 1D multilayer model ACASA that includes a third-order turbulence closure and the 3D model STANDFLUX. The soil and understory evapotranspiration captured with the eddy-covariance system in the trunk space constituted 10% of ecosystem evapotranspiration measured with the eddy-covariance system above the canopy. A comparison of transpiration measured with the sap flux technique and inferred from below and above canopy eddy-covariance systems revealed higher estimates from eddy-covariance measurements than for sap flux measurements. The relative influences of possible sources of this mismatch, such as the assumption of negligible contribution of evaporation from intercepted water, and differences between the eddy-covariance flux footprint and the area used for scaling sap flux measurements, were discussed. Ecosystem evapotranspiration as well as canopy transpiration simulated with the two models captured the dynamics of the measurements well, but slightly underestimated eddy-covariance values. Profile measurements and models also gave us the chance to assess in-canopy profiles of canopy evapotranspiration and the contributions of in-canopy layers. For daytime and a coupled or partly coupled canopy, mean simulated profiles of both models agreed well with eddy-covariance measurements, with a similar performance of the ACASA and the STANDFLUX model. Both models underestimated profiles for nighttime and decoupled conditions. During daytime, the upper half of the canopy contributed approximately 80% to canopy evapotranspiration, whereas during nighttime the contribution shifted to lower parts of the canopy.     

Degradation products of chlomethoxynil (X-52) in soil

The degradation of unlabelled and ^l4C-labelled chlomethoxynil (2,4-dichlorophenyl 3′-methoxy-4′-nitrophenyl ether) in a flooded soil was studied in the laboratory, using thin-layer chromatography (TLC) and combined gas chromatography-mass spectrometry (GC-MS).

Chlomethoxynil was rapidly degraded, and labelled chlomethoxynil was largely transformed into substances which were unextractable with organic solvents. Moreover, most of the radioactive substances extracted with organic solvents were not “free” compounds but complexes. The degradation products identified were the amino derivative (2,4-dichlorophenyl 4′-amino-3-methoxyphenyl ether), the demethyl derivative (2,4-dichlorophenyl 3′-hydroxy-4′-nitrophenyl ether), the formylamino derivative (2,4-dichlorophenyl 4-formylamino-3′-methoxyphenyl ether), the acetylamino derivative (2,4-dichlorophenyl 3-methoxy-4′-acetylaminophenyl ether), thepropionylamino derivative (2,4-dichlorophenyl 4-propionylaminophenyl ether), 2,4-dichlorophenol, and several other minor compounds.     

Effect of pH on interaction between As(III) or As(V) and manganese(IV) oxide

The efficiency of As(III) oxidation by MnO₂, and retention of oxidation products varies with system pH. Maximum retention by hydrous Mn(IV) oxide occurs at pH < 5, declining at higher pH to about half total As at pH 10. The adsorption capacities of pyrolusite and cryptomelane at pH ～6.5 for As(V) species were 10 and 25 mmol kg^?1, respectively. HMO surface saturation (～10 mmol kg^?1) was reached with equilibrium As(V) levels of 5 to 8 × 10^?6 M but this was supplemented at higher levels by an absorption process where uptake increased linearly with concentration (e.g., 68 mmol kg^?1 with 2 × 10^?5 M As(V)). Added As(III) was avidly oxidized and most product retained at pH 3. At higher pH increasing amounts of As(III) remained unoxidized due to initial reactions apparently blocking access to internal pores. Added Na⁺ reduced the amount of As retained by the HMO, with the phosphate salt having a significant effect. Extraction studies confirmed that most As could be released by exposure to reducing agents or chelating agents (EDTA). The environmental significance of the results has been considered.     

Identification of oxidation products of (-)-epigallocatechin gallate and (-)-epigallocatechin with H(2)O(2)

(-)-Epigallocatechin gallate (EGCG) and (-)-epigallocatechin (EGC) are two important antioxidants in tea. They also display some antitumor activities, and these activities are believed to be mainly due to their antioxidative effects. However, the specific mechanisms of antioxidant action of tea catechins remain unclear. In this study are isolated and identified two novel reaction products of EGCG and one product of EGC when they were reacted separately with H(2)O(2). These products are formed by the oxidation and decarboxylation of the A ring in the catechin molecule. This study provides unequivocal proof that the A ring of EGCG and EGC may also be an antioxidant site. This study also indicates an additional reaction pathway for the oxidation chemistry of tea catechins.     

Catalytic synthesis of humic acids from phenolic compounds by Mn(IV) oxide (Birnessite)

Abstract

Extract

Humic acids are natural organic polymers and are important constituents of soils (Kononova 1966). Although the mechanisms of the formation of humic acids are very complicated, the oxidative polymerization of polyphenols is considered to be one of the most important mechanisms (Kononova 1966; Stevenson 1982). The oxidative polymerization can be accelerated by enzymes (e.g., Haider et al. 1975; Flaig et al. 1975) as well as by inorganic components (e.g., Kyuma and Kawaguchi 1964; Shindo and Huang 1982; Kumada 1987). Shindo and Huang (1985) and Shindo and Higashi (1986) compared the relative effectiveness of several oxides, primary minerals, and clay minerals in promoting the synthesis of humic polymers from hydroquinone, and found that the promoting effect of Mn(IV) oxide was most striking among the inorganic components studied. The catalytic power of inorganic components in the synthesis of humic polymers from phenolic compounds may be influenced by the chemical structure of the compounds. However, little information is available on this aspect.