生物结皮发育对风沙土盐基离子释放和矿物风化的影响

为探明生物结皮发育对风沙土盐基离子释放和矿物风化的影响,以进一步明确生物结皮的风化成土作用。以典型风沙土上发育的生物结皮为对象,通过模拟淋溶试验比较不同类型生物结皮(藻结皮、藻—藓混生结皮和藓结皮)覆盖土壤的盐基离子释放规律,探究盐基离子释放量随淋溶液pH的变化趋势,以及量化生物结皮覆盖土壤的矿物风化速率。结果表明:矿物风化反应阶段不同种类盐基离子的淋出量均较为平缓,生物结皮覆盖土壤的各盐基离子总淋出量表现为Ca²⁺＞K⁺＞Mg²⁺＞Na⁺,其中藻结皮覆盖土壤的盐基离子总淋出量最高,比无结皮、混生结皮和藓结皮分别增加了112.0%,31.2%,27.1%。淋溶液pH显著影响盐基离子的淋溶释放,且其作用程度因离子种类和结皮类型而异。生物结皮覆盖提升了土壤的易风化矿物含量、风化程度和速率,藻结皮、混生结皮和藓结皮覆盖土壤的风化速率相比无结皮分别提升了61.2%,27.1%,152.6%,并且风化速率随淋溶液pH降低而提升。综上,生物结皮能显著促进风沙土矿物风化,其对风沙土改良和修复具有积极意义。     

Effect of north and south exposure on weathering rates and clay mineral formation in Alpine soils

A comparison was made between two soil climosequences on north- and south-facing slopes in northern Italy to determine the influence of slope aspect on soil processes. The climosequences span an elevational gradient ranging from moderate (1200 m a.s.l.) to high alpine (2420 m a.s.l.) climate zones on surfaces having an age of about 15 000 years. The soils were investigated with respect to organic C, oxalate and dithionite extractable Fe, Al and Si, elemental losses (Ca, Mg, K, Na, Fe, Al, Si, Mn) and clay minerals. The stocks of soil org. C as well as of oxalate-extractable Fe and Al was greatest in the subalpine zone near the timberline. There are no clear differences in organic C content between the soils on north- and south-facing sites. Fe-oxalate and to a lesser extent Al_o-stocks were, however, greater on north-facing sites, indicating that weathering is greater there. Eluviation and illuviation of Al and Fe within the soil profile, typical for podzolisation, was more distinctly expressed on the N slopes. The probability of ITM (Imogolite-type-material) formation in the soil seemed to be greater on south-facing sites. On the north-facing sites, element leaching was most intense in the subalpine zone close to the timberline while on the south-facing sites this was only the case for the base cations. The N slopes exhibited higher leaching of elements which generally indicates a higher weathering intensity. On south-facing sites, typical podzolisation processes were measurable only above 2000 m a.s.l. The development of smectites is also a reflection of the weathering intensity; smectite was discernible in the surface horizon at all sites on N slopes but the highest amount was detected in the sub-alpine climate zone. For the south-facing sites only in the alpine climate zone could smectite be detected. Higher temperatures and an increased number of freeze-thaw cycles on south-facing slopes should theoretically enhance rates of chemical weathering. This could, however, not be confirmed with our measurements. The degree of chemical weathering increases from the south- to the north-facing sites that are characterised by lower temperatures, lower evapotranspiration and consequently by a higher humidity. Although precipitation in Alpine regions is abundant, the availability and flux of water through the soil is the prime factor in weathering intensity.     

Pyrite oxidation in a sediment sample of an open-cut brown coal mine: mineral formation,buffering of acidity and modeling of cations and sulfate

Secondary reactions occurring in pyrite‒containing sediments under aerobic conditions are complex and are not fully understood. Objectives were to (i) study the formation of secondary minerals using x‒ray diffraction (XRD) and ion activity product (IAP) calculations; (ii) to obtain a budget of acidity producing and consuming processes; and (iii) to study the performance of a chemical equilibrium model (including kinetic reactions) using sequential batch experiments with varying input solutions on samples of different pyrite oxidation states. A sediment sample from the open pit coal mine Garzweiler, Germany, was oxidised in the laboratory to obtain four different pyrite oxidation states. Sequential batch experiments were carried out using H₂O, 100 mM CaCl₂ and 10 mM NaOH as input solutions. A coupled equilibria model was used to describe the experiments. The model (PHREEQC) included inorganic complexation, redox reactions, precipitation/dissolution of sparingly soluble salts, multiple cation exchange and pyrite oxidation using a simple input function. IAP calculations and XRD showed the formation of large amounts of gypsum with increasing pyrite oxidation and for the highly oxidised sample also the formation of hydroniumjarosite. The budget of acidity consuming processes followed the order (i) release of Fe(III) into the solution phase (51% of produced acidity); (ii) Al release into solution and exchangeable phases (probably mainly due to silicate weathering, 22% of produced acidity); and (iii) CEC reducing processes (11% of produced acidity). Modeling of the sequential equilibration experiments with water and CaCl₂ gave satisfactory agreements between modeled and measured pH and sorption values, indicating that the main processes governing pH and ion sorption were quite well understood. However, model results of the alkaline additions at larger pyrite oxidation states differed considerably from the experimental results.     

Chemical and Mineralogical Properties of Norwegian Alum Shale Soils,with Special Emphasis on Heavy Metal Content and Availability

Abstract

Alum shale and till soils overlying alum shale bedrock were analysed for aqua regia and NH₄OAc/EDTA extractable Pb, Cu, Zn, Ni, Mn and Cd. The means of these determinations were compared with those of Norwegian, Finnish and Swedish non-alum shale soils. Alum shale soils seemed to contain higher amounts of both total and easily extractable Cu, Zn, Ni and Cd. Total Pb content also seemed to be higher in the alum shale soils. The relative availability of Cd, Ni and Mn, expressed as the ratio of NH₄OAc/EDTA to aqua regia extractable, was found to be greater than that of Pb, Cu and Zn in the alum shale and till soils.     

磷酸铁盐涂层: 控制黄铁矿氧化的新手段

A novel coating technique was develped for controlling pyrite oxidation .The technique involved leaching pyrite particles with a solution containing low concentrations of phosphate and hydrogen peroxide.During the leaching rpocess,the iron released from pyrite by hydrogen proxide was precipitated by phosphate as a ferric phosphate coating .This coating was shown to be able to effectively prevent pyirte from oxidation and it could be established at the expense of only surface portions of pyrite.The emergence of this technique could provide a unique potential route for abating acid mine draingage and reclaiming sulfide-containing degraded mining land.     

Secondary minerals from extrapedogenic per latus acidic weathering environments at geomorphic edges, Eastern Nebraska, USA

Acidic weathering of the sulfidic Upper Cretaceous Carlile and Pierre Shales in Nebraska has led to the precipitation of the Al sulfate–hydroxide minerals aluminite, alunite, “basaluminite”/felsöbányaite (e.g.,), the aluminum hydroxides gibbsite and bayerite, and the rare Al phosphate hydroxide vashegyite. Kaolinite has also been produced as a result of this acidic weathering. These minerals do not appear as neoformed constituents in any extant soils in the region, and their existence underscores the ability of pyrite oxidation to produce major changes in mineralogy on a Holocene to Recent time scale. Jarosite, hydronium jarosite, gypsum, halotrichite, and melanterite also appear as secondary minerals in the weathered shales. Acidic weathering and the formation of new minerals is extrapedogenic because it occurs well below the limit of modern soil sola. These processes also occur at the edges of major landscape elements and can be considered to have a strong lateral component processes, making them “per latus” processes in our usage.     

黄土的连续提取实验及Rb/Sr值意义

通过连续提取实验 ,将黄土和古土壤中元素的赋存状态分成六种形态 :水可溶态、可交换态、碳酸盐结合态、铁锰氧化物结合态、有机物结合态和残留态。结果表明 ,K和Rb等元素 ,主要赋存于残留态中 ,而Ca、Sr等元素主要赋存于碳酸盐结合态和残留态中。Sr在黄土和古土壤中的赋存状态明显与Ca的分布有关。在风化成壤作用中 ,碳酸盐的淋溶和含Ca硅酸盐矿物的分解 ,引起Sr的淋失 ,而Rb保持稳定。因此 ,Rb Sr值指示了黄土和古土壤遭受的淋溶程度 ,反映了黄土高原的降雨量 ,是夏季风强度变化的替代性指标     

Water and Element Fluxes of Red Oak Ecosystems during Stand Development on Post-Mining Sites (Lusatian Lignite District)

Most spoils in the Lusatian lignite district have been afforested successfully. However, since soil chemical status remains very different compared to unmined locations even after decades it is still unclear if forest ecosystems develop to a self-sustainable status or if restoration will fail in the long term. To clarify this question water and element fluxes of different-aged red oak(Q. rubra L.) stands on both Quaternary pure sands and Tertiary, pyritic loamy sands were investigated and compared to a nearby, unmined location. Due to increasing interception and evapotranspiration, the deep percolation rates of red oak forests decline drastically within30 yr. Annual groundwater recharge is about 300 mm yr^-1(41–46% of precipitation) initially. Deep percolation of the older stands decrease to less than 15% of precipitation, independent of substrate type. Tertiary substrates are characterized by intensive leaching of H, Fe, Al, Mg, Ca, NH₄-N and SO₄-S due to pyrite oxidation and therefore enhanced silicate weathering. Despite of drastically declining output rates with progressing ecosystem development, they remain remarkably higher as compared to Quaternary sands. However, despite differences in soil chemistry, the aged stands act as an almost complete sink for N, P and K. Compared to adjacent oak forests on undisturbed soils the stands on reclamation sites show very similar patterns with regard to N, P, K, Ca and Mg turnover.     

亚热带花岗岩地区土壤矿物风化过程中盐基离子的释放特征

矿物风化过程中盐基离子释放遵从一定的化学计量关系,这种化学计量关系一般只能通过模拟实验来获取。本研究采用pH 7.0的EDTA-乙酸铵溶液将土壤中的交换性盐基离子完全洗脱出来,然后用Batch方法模拟不同pH溶液淋溶洗脱盐基和未洗脱盐基土壤,旨在消除土壤中交换性盐基离子的影响后更为准确地判断土壤矿物风化的盐基离子释放特征。结果表明:未洗脱盐基土壤的淋出液pH由3.73±0.14逐渐上升到4.23±0.06,主要原因是淋溶液中有高浓度的NH_4~+;洗脱盐基土壤矿物风化后淋出液pH从7.39±0.02逐渐下降到5.39±0.17,主要是由于土壤中可风化矿物减少。土壤交换性盐基离子会改变盐基离子释放特征、释放总量:未洗脱盐基土壤经酸雨淋溶后,各盐基离子释放均呈现急速下降后逐渐平缓的趋势,洗脱盐基土壤矿物风化后,K~+及盐基离子释放总量呈波动上升趋势,且盐基离子释放总量比未洗脱盐基土壤低。土壤交换性盐基离子的存在还会改变淋出液中的盐基离子化学计量关系:未洗脱盐基土壤的K~+︰Ca~(2+)︰Mg~(2+)︰Na+化学计量关系为11︰13︰4︰1(当量比),而洗脱盐基土壤为7︰2︰2︰1。K~+是盐基离子中风化释放量最多的,大部分K~+来自于土壤中云母的风化。因此,只有利用洗脱盐基土壤的盐基离子释放量才能准确计算矿物风化速率并获得准确的化学计量关系。土壤矿物风化作用随着淋溶液酸度增大而增强,但模拟一年降雨量的情况下,p H 3.5、4.5和5.5三种不同p H溶液对矿物风化后盐基离子的释放在实验期间没有显著性影响,较长时间后的差异性有待观察。本研究表明,可以通过预洗脱盐基土壤然后模拟酸雨淋溶的方法,观察矿物风化特征,特别是盐基离子释放的化学计量特征。     

Quantitative evaluation of pedon formation in calcareous glacial deposits in Ohio

The genesis of 24 pedons derived from calcareous glacial deposits in Ohio was studied with quantitative (reconstruction) techniques. This report summarizes refinements in quantitative techniques and discusses problems encountered during those studies.In most of our studies, elemental Zr was employed as the stable index constituent. Unit volume factors, which are based on Zr distribution, were found to be a function of size separates employed for analysis. Therefore, it is suggested that the index constituent should be determined on all fractions > 2 μm in order to provide the most reliable estimations of gains and losses. Elemental ratios of Ti/Zr were employed in our studies as the primary indicators of parent-material uniformity; however, additional lines of evidence are advisable because: (1) micro-occlusions of rutile and zircon have been found in host light minerals, (2) elemental Ti exhibits depth distributions indicative of weathering trends, and (3) Ti is preferentially lost from gravel and sand due to the disintegration of shale. Calculated particle-size distribution in the reference base supposing carbonate removal and/or shale disintegration can be employed to partition computed clay gains and losses to such processes as attrition of sand- and gravel-size shale, carbonate leaching, in situ neoformation of clay, and clay translocation. Sub-sampling can greatly increase the sensitivity of reconstruction analysis, but even the most precise sampling scheme will not permit identification of differences in soil development below 10%.     

Ausfilterung von Schwefelverbindungen aus der Luft durch einen Buchenbestand

Filtering of Sulfur compounds from air by beech forest In a mature beech (Fagus silvatica) forest the amounts of sulfate-S per ha and year in open land precipitation, throughfall, stem flow and seepage in 100 cm soil depth have been measured from 1969 to 1976. From the fluxes measured quantitative data on plant leaching and dry deposition in the form of plant filtering are derived. Dry deposition amounts to 26kg S · ha^?1 · y^?1 and is of the same size as wet deposition (24 kg). The leaching of sulfate takes place only in autumn and amounts to ca. 3 kg S. The acid soil in the range of Al-buffering increases its sulfate storage annually by ca. 17 kg S/ha.     

Estimation of the Maximum Critical Load for Sulfur in South Korea

The maximum critical load of sulfur and its exceedance by the sulfur deposition of 1994–1997 were mapped for South Korea with a spatial resolution of 11 × 14 km using the steady-state mass balance method. The Korean soil and geological maps were used as basis for the estimations of the critical alkalinity leaching and the weathering rate of base cations. The normalized difference vegetation index data obtained from the Advanced Very High Resolution Radiometer (AVHRR) together with the observed primary productivity of plants were used for the estimation of the critical uptake of base cations. Wet deposition of the non-sea-salt base cations was derived from measured base cation concentrations in precipitation, precipitation rate and air concentration of total suspended particulate while dry deposition of base cations was estimated using the inferential technique using scavenging ratios. The predominant ranges of base cation weathering, uptake and deposition were estimated to be of 200 – 600 eq ha^?1 yr^?1, 200 – 400 eq ha^?1 yr^?1 and 400 – 600 eq ha^?1 yr^?1, respectively. Critical alkalinity leaching was mainly in the range of 1000 – 2000 eq ha^?1 yr^?1 due to relatively high value of precipitation runoff. Exceedance of sulfur critical load was found at 40 % of the ecosystems considered mainly in the southeastern part of Korea, and about 60 % of Korea ecosystems were sustainable against sulfur acidity loadings.     

Soil slips on weathering-limited slopes underlain by coarse-grained granite or fine-grained gneiss near Seoul,Republic of Korea

The chemical, mineral, physical, and mechanical properties of two soil layers on soil-slip scars in slopes underlain by coarse-grained granite and fine-grained granitic gneiss near Seoul, Republic of Korea, were examined. Our aim is to study the effect of the mineral grain size of the bedrock on the soil layer structure and the return period of shallow soil slips. Because of the coarser slope materials in granite resulting from weathering, the permeability is larger and the weathering front has a copious water supply; also, because of the smaller specific surface area of the minerals, restricted leaching produces grus from the bedrock, so that the rate of formation of soil (and in particular the slip plane) due to chemical weathering is faster. Since, on granite slopes, the leaching proceeds toward the surface, the sliding plane is deeper with coarser soft grus, resulting in the existence of a minimum c value in the soil layer. On gneiss slopes, by contrast, leaching cannot proceed with decreasing soil depth, and the sliding plane is deeper with finer soft grus just above hard grus and has similar c and ϕ values as the upper soft grus because the grain size of both soils is the same. In the granite soil layers, the sliding plane corresponds to the minimum shearing resistance, whereas in the gneiss soil layers, the shearing resistance increases gradually with soil depth, and the sliding plane is formed when the weathering front is located deeper. Because of the faster soil formation rate and the shallower slip depth in granite slopes, the return period of occurrence of soil slips should be shorter in granite slopes than in gneiss slopes.     

Types of recent weathering crusts and their global distribution

Recent weathering crusts are defined as those formed and in process of formation under present or closely similar climatic conditions. Such crusts are classified on the basis of their composition and profile form into four types: nonleaching, weak periodic leaching, strong leaching, and freezing. Each but the last of these types is divided into a pair of subtypes according to the intensity of eluvial processes. All subtypes are divided into lithogenic groups reflecting the composition and properties of the parent materials.Recent weathering crusts of the nonleaching, weak periodic leaching, and freezing types are the most extensive and widespread over the world. Crusts of the strong leaching type, especially of the extra-humid subtype, are being formed only to a limited extent at the present time, although they were formed extensively in past geologic periods. Sedimentary parent materials with high proportions of quartz-kaolinite and goethite-gibbsite-kaolinite minerals, inherited from earlier periods, are common in many regions with arid and semi-arid climates at the present time.The potential for intensive weathering under humid and extra-humid, tropical climates has been realized in few recent weathering crusts because of the presence on the land surface of former weathering crusts that were subjected to strong hypergenic processes in the past. Where fresh parent rocks are exposed in small areas under such climates, profound weathering does now occur with the formation of new minerals.     

Pyrite and siderite oxidation in swamp sediments

Differences in the processes of pyrite and siderite oxidation, in reclaimed swamp sediments of the Skjernå delta (Denmark), are described from sediment chemistry, mineralogy and pore water chemistry. Pyrite oxidation leads to extreme soil acidification, with pH dropping to about 2, the release of large amounts of weathering products to the pore water, and the precipitation ofiron oxides, jarosite and gypsum. Siderite oxidation results only in moderate soil acidification where the pH does not drop below 3.5, while part of the acidification is due to the oxidation of small amounts of sulphur compounds together with siderite. The release of weathering products to the pore water is limited and only iron oxide is precipitated. Calculations indicate that equilibrium with amorphous FeOOH, gypsum and amorphous Al(OH)₃ sets an upper limit to the Fe³⁺, SO₄ and Al concentrations in the pore water.     

ANDESITE WEATHERING

Petrographic and quantitative mineralogical analyses of two andesites and their saprolite (weathered rock) from the Cascade Range in California reveal a mineral weathering sequence in the rocks related to crystal size and composition and to weathering environment. Both the hypersthene andesite and the olivine andesite studied have been subjected to moderate to intensive leaching by acid solutions percolating through the superjacent soil bodies. Although the two parent rocks differ in chemical and mineralogical composition, their weathering to saprolite has followed a similar progression. During early stages of weathering of both rocks, relatively large hypersthene phenocrysts are most resistant. Following in decreasing order of resistance in both cases are plagioclase phenocrysts and finegrained mafic minerals, olivine, and glassy matrix material. Quartz is relatively stable in the earliest weathering stages, but it decreases rapidly with increased weathering. Free iron oxides and clay increase with increased weathering. Amorphous clay dominates the early weathering stages, but as weathering progresses, kaolin increases relative to amorphous clay.     

Laboratory Investigation of the Control of Acid Mine Drainage Using Alkaline Paper Mill Waste

A great deal of research effort has been undertaken to find an effective solution to the problem of acid mine drainage. Indeed, Canadian legislation requires mining companies to respect environmental regulations by providing a rehabilitation plan with a financial guarantee. In order that the Canadian mining industry remains competitive, the proposed solutions have to be not only efficient but also economic, that is why the use of another waste material is attractive. The main objective of this study was to investigate the technical and environmental feasibility of stabilizing acid mine residues using alkaline paper mill waste produced by the pulp and paper industry as a basic source. The mineralogical characterization of the alkaline paper mill shows that calcite is the dominant mineral with hydrated lime (portlandite) present at a low content. The mineralogical characterization of the mining residues shows a polyphasic system where silica dominates the oxidized zone. On the other hand, a high pyrite content is present in the non-oxidized zone. The essential observations that emerge from the leaching tests undertaken in the laboratory can be summarized by the efficiency of the incorporation of the alkaline paper mill waste (1/3 waste and 2/3 mining residue) on the production of acid mine drainage. In fact, it can be observed that there is a reduction of the high toxicity elements like heavy metals. The increase in pH permits the reduction of catalytic bacterial activity and reduces the rate of oxidation in the mining residue.     

Removal of Arsenic, Boron, and Selenium from Excavated Rocks by Consecutive Washing

This paper describes the leaching behavior and release mechanisms of arsenic (As), boron (B), and selenium (Se) from excavated rocks using sequential extraction for solid-phase fractionation, batch experiments with pH variation, and consecutive batch experiments with changes in the solid?Cliquid mixing ratios. Arsenic in the excavated rock was mostly found with the sulfides/organic matter fraction while majority of the leachable B and Se were associated with the exchangeable phases. The leaching of As was strongly pH dependent, Se was pH dependent only around the acidic region, and B was pH independent. Consecutive washing technique with deionized water effectively lowered the B and Se concentrations in the leachate below the drinking water standards of Japan, but was inefficient in the removal of As. Arsenic exhibited non-conservative leaching behavior and its movement was affected by processes like dissolution, precipitation, and pyrite oxidation. In contrast, B and Se behaved more conservatively, resulting in their easy removal from the excavated rock by simple washing and dilution.     

Determining weathering rates of soils in China

As an important parameter for critical load calculation and soil acidification simulation, weathering rates of soils in China were studied using different methods of calculation. The approaches used were the mass balance approach, the soil mineralogical classification, the total analysis correlation, the PROFILE model, the MAGIC model and a simulated leaching experiment. Since chemical weathering of secondary minerals usually plays a much more important role in neutralizing the long-term acidification of soils in China than that of parent material, soil mineralogy rather than parent rock/material type, which is regarded as the most suitable factor representing weathering rates in Europe, should be adopted as the basis for soil classification. The weathering rate assigned to each soil should also be corrected when the effect of temperature is considered. Due to the variation in experimental conditions, the weathering rates of soils from laboratory experiment may be difficult to compare with field determined rates, and should be adjusted by pH and percolation rate. The comparison of various methods in this study shows that the weathering rates of soils estimated by the PROFILE model coincide well with those from other independent methods such as the dynamic modeling by MAGIC and the modified leaching experiment. The weathering rates were very low (usually lower than 1.0 kEq·ha⁻¹·year⁻¹) for Allites (including Latosol, Lateritic Red Earth, Red Earth, Yellow Earth and Yellow-Brown Earth) in south China and Silalsols (consisting of Dark Brown Forest Soil, Black Soil and Podzolic Soil) in northeast China, and very high for Alpine Soils, Desert Soils and Pedocals in west China. The content of weatherable minerals in soil is the most important factor in determining the spatial distribution of weathering rate in China, while the difference in temperature may be the reason why the weathering rate of soil in northeast China was lower than that in southeast China.     

某铅锌矿开采区土壤镉的污染及有关界面过程

本文根据不同的采样设计 ,定量推算并证实了某铅锌矿区采矿裸露岩矿的加速风化过程、堆置于土壤上的采矿碎石和尾砂的雨水淋洗过程、采矿散发的含镉物质通过大气的回降过程以及有关的界面过程的存在 ,和对该矿区土壤镉污染的重要贡献 ,表明它们对土壤健康质量的损害确实起着十分重要的作用