察尔汗盐湖固体钾盐溶解对溶剂注入速率响应机制研究

察尔汗盐湖浅部储卤层赋存有储量可观的固体钾盐资源, 目前正处于溶解液化开采阶段。储卤层中固体钾盐矿物溶解及储卤层结构变化特征受到溶剂注入速率控制, 但其控制机制尚不明确。本文以察尔汗盐湖浅部储卤层典型钻孔岩芯为研究对象, 通过开展室内岩芯柱渗流模拟实验, 研究岩芯在三种流速条件下储卤层渗透系数和固体钾盐矿物溶出的变化规律。结果表明: (1)随着注入溶剂速率的增大, 岩芯渗透系数呈现逐渐增大的趋势, 渗出液中钾离子浓度呈现持续减小的趋势, 但在流速改变的时间节点处, 岩芯渗透系数和其对应溶出液中钾离子浓度均出现异常增加现象。矿物的溶解引起储层孔隙度增加, 而溶剂流速的改变会导致松散盐类矿物颗粒重组。(2)储卤层岩芯固体钾盐矿物溶解受到溶剂注入速率的影响明显。注入速率增加引起矿物颗粒重组以及滞留孔隙高浓度水体释放是造成渗出液中K+浓度短暂性升高的主要原因。本次实验研究对于研究区低品位固体钾盐的水溶开采具有一定理论指导意义。     

矿物之间的元素和同位素平衡:地质测温和等时线定年的热力学和动力学控制

在特定的地质事件过程中,矿物等时线放射体系是否达到并且保持了平衡是变质岩Sm-Nd和Rb-Sr同位素年代学中的一个重要问题。在这个问题上矿物对O同位素测温与矿物等时线定年相似,因此两者之间可以相互制约。在岩浆岩和变质岩中,矿物中Sm-Nd、Sr和O之间的扩散速率在无水的条件下一般具有可比性,因此矿物之间O同位素的平衡状态可以用来对Sm-Nd和Rb-Sr定年的有效性进行检验。对大别-苏鲁造山带超高压变质岩的Sm-Nd和Rb-Sr等时线矿物进行O同位素测温,得到Sm-Nd等时线有时给出三叠纪年龄,有时给出非三叠纪年龄;对应的矿物O同位素分馏分别处于平衡和不平衡状态。对于引起非三叠纪等时线年龄的原因,一方面可以是由于榴辉岩相变质过程中同位素体系没有达到平衡,另一方面则可能角闪岩相退变质作用打破了平衡。等时线矿物中初始同位素比值的均一化速率主要受慢扩散矿物的影响,而矿物等时线时钟的启动主要受高母/子比值矿物控制。因此在变质作用过程中,只有当高母/子比值矿物同时具有快的放射成因同位素扩散速率,才可能得到有效的矿物等时线来用于变质年龄的测定。根据不同矿物中不同元素在扩散速率上的差异,能够定量估计大陆碰撞过程中榴辉岩相变质的持续时间。应用增量方法和离子孔隙度经验模型,不仅分别能够从理论上准确计算所有固体矿物的氧同位素分馏系数和获得不同矿物中元素的扩散参数,而且分别能够定量预测热力学平衡条件下共生矿物之间的¹⁸O富集顺序和相同条件下矿物中元素扩散速率的相对快慢。     

Etch pit formation on iron silicate surfaces during siderophore-promoted dissolution

Understanding the effects of microbiota on mineral alteration requires the ability to recognize evidence of bacteria-promoted dissolution on mineral surfaces. Although siderophores are known to promote mineral dissolution, their effects on mineral surfaces are not well known. We have utilized atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), and Mirau vertical scanning interferometry (VSI) to investigate surfaces after incubation with the siderophore desferrioxamine-B mesylate (DFAM) and under colonies of bacteria. Iron-silicate glass planchets chemically similar to hornblende were incubated in buffered growth medium with siderophore-producing bacteria (Bacillus sp.) for 46 days with parallel abiotic experiments conducted with and without 240 μM DFAM, with and without 0.01 g l^− 1 of microbially produced extracellular polysaccharides (EPS, alginate or xanthan gum). Some glass planchets were protected by dialysis tubing from direct contact with the EPS. Weekly sampling and analysis of all filtered sample solutions showed negligible Fe and Al release in the control experiments and significant release of Fe and Al in the presence of DFAM, with negligible changes in pH. Concentration of Fe in the filtered solutions after incubation with bacteria was below detection, consistent with uptake of Fe by cells. Release of Fe, Al, and Si in control, xanthan-only, and alginate-only experiments was negligible. Release of these elements was enhanced in all experiments containing DFAM, and greatest in alginate + DFAM experiments.

AFM and VSI analyses reveal widespread, small etch pits and greater root mean squared roughness on siderophore-exposed surfaces and fewer, localized, larger etch pits on bacteria-exposed surfaces. This is the first documented case of etch pit development during siderophore-promoted dissolution. Roughness was not affected by the growth medium, alginate, or xanthan gum alone. The roughness trends among samples correlate with trends in Fe depletion documented by XPS. Enhanced dissolution and roughness cannot be attributed to direct contact with EPS because no significant chemical or physical differences were observed between surfaces directly exposed to EPS and those protected by dialysis tubing. Acetate released from the EPS may have enhanced the siderophore-promoted dissolution. Siderophores produced by Bacillus sp. may be responsible for some of the ‘biopits.’ The difference in size and distribution of the biopits may be related to colonization.     

Selective separation of pyrite from chalcopyrite and arsenopyrite by biomodulation using Acidithiobacillus ferrooxidans

This paper discusses the selective depression of pyrite from chalcopyrite and arsenopyrite by biomodulation using Acidithiobacillus ferrooxidans under natural conditions of pH. The effect of bacteria–mineral interaction on the surface charge of mineral and bacterial cell was studied by microelectrophoresis. Adhesion experiments were conducted to establish the relationship between cell adhesion to specific minerals and the electrokinetic behaviour of the minerals subsequent to interaction with cells. Effect of bacterial interaction on the xanthate-induced flotation of all the minerals was assessed. Adhesion of A. ferrooxidans on pyrite was rapid and tenacious and subsequent to interaction with cells, pyrite remained hydrophilic even in presence of xanthate collector. The collector, on the other hand, was able to render good flotability to chalcopyrite even after interaction with bacterial cells. Copper activated arsenopyrite was able to retain its hydrophobicity in presence of cells due to poor attachment kinetics of cells to the mineral surface. Thus, by suitably conditioning with the cells and collector, it was possible to effectively depress pyrite from chalcopyrite and arsenopyrite.     

地壳浅部导电性矿物的一种新的压溶机制：应力原电池过程

以黄铁矿为例,通过导电性矿物的力学-电化学相互作用实验,得出：导电性矿物的电极电位与弹性轴压应力是较好的负线性相关关系。以此为基础,通过电化学理论分析,得出：地壳浅部与溶液接触的导电性矿物颗粒内部存在各种各样的应力原电池,通过应力原电池过程,压溶作用得以实现。导电性矿物应力原电池引起压涛作用的发现,无疑对诸如构造地球化学、地电化学甚至湿法冶金等领域的有关研究具有重要意义。     

Partition of trace elements in co-existing biotite,muscovite and potassium feldspar of granitic rocks,northern Portugal

Chemical analyses are given for Na, K, and trace elements of muscovite and potassium feldspar of granitic rocks. The distribution of trace elements in co-existing minerals suggests that equilibrium was attained and that muscovite is a primary mineral. These observations and the comparison of the trace-element chemistry of megacrysts and groundmass potassium feldspars of porphyritic rock types lead to the conclusion that the megacrysts are in face phenocrysts which crystallized in equilibrium with the other minerals of the rock.The ranges of values of the distribution coefficients K_D(Rb/K) and K_D(Cs/K) in mineral pairs confirm other observations on the equilibrium among various minerals. However, application of experimental data on the temperature effect on K_D leads to results conflicting with the petrologic observations. The possible influence of other factors on K_D is analyzed and among these factors the composition of the feldspar and the solidus-liquidus temperature interval may play a dominant role.     

Nanoscale mechanical property variations concerning mineral composition and contact of marine shale

Mechanical properties of shales are key parameters influencing hydrocarbon production – impacting borehole stability, hydraulic fracture extension and microscale variations in in situ stress. We use Ordovician shale (Sichuan Basin, China) as a type-example to characterize variations in mineral particle properties at microscale including particle morphology, form of contact and spatial distribution via mineral liberation analysis (MLA) and scanning electron microscopy (SEM). Deformation-based constitutive models are then built using finite element methods to define the impact of various architectures of fracture and mineral distributions at nanometer scale on the deformation characteristics at macroscale. Relative compositions of siliceous, calcareous and clay mineral particles are shown to be the key factors influencing brittleness. Shales with similar mineral composition show a spectrum of equivalent medium mechanical properties due to differing particle morphology and mineral heterogeneity. The predominance of small particles and/or point-point contacts are conducive to brittle failure, in general, and especially so when quartz-rich. Fracture morphology, length and extent of filling all influence shale deformability. High aspect-ratio fractures concentrate stress at fracture tips and are conducive to extension, as when part-filled by carbonate minerals. As fracture spacing increases, stress transfer between adjacent fractures weakens, stress concentrations are amplified and fracture extension is favored. The higher the fractal dimension of the fracture and heterogeneity of the host the more pervasive the fractures. Moreover, when fractures extend, their potential for intersection and interconnection contributes to a reduction in strength and the promotion of brittle failure. Thus, these results provide important theoretical insights into the role of heterogeneity on the deformability and strength of shale reservoirs with practical implications for their stimulation and in the recovery of hydrocarbons from them.     

Analyse des circuits mineralurgiques par cascadographie—Caracterisation de l'alimentation et evaluation de la fonction de selection

Cascadography is a generic, laboratory, instrumentational method of separating and characterizing mixes of mineral or particle species based on subtle physical and physiochemical differences. Like gas chromatography, cascadography characterizes a sample by the temporal separation of mineral species. Using a number of identical unit operations in series, the sample feed is injected into the first unit operation at time equals zero, and samples are taken at regular intervals from the last cell product. From the n-th cell, the product becomes the feed to the (n+1)th cell. Other than as a product, no material is removed from any cell—there is no circulating load or feedback. First to appear in the product are the rapidly moving particles followed by the more slowly moving particles. For example, if there exists a number of identical particles, then the particles will appear together in the output of the system. As the number of cells in series increases, so does the resolution between batches of particles with similar properties. If the system being studied is flotation, pure mineral species as well as locked particle assays can be made of the feed and waste streams, and from this information, the flotation cell selection function can be calculated.     

Arsenic release from chlorine-promoted alteration of a sulfide cement horizon: Evidence from batch studies on the St. Peter Sandstone,Wisconsin, USA

Elevated As concentrations have been measured in wells in the St. Peter Sandstone aquifer of eastern Wisconsin, USA. The primary source is As-bearing sulfide minerals (pyrite and marcasite) within the aquifer. There is concern that well disinfection by chlorination may facilitate As release to groundwater by increasing the rate and extent of sulfide oxidation. The objective of this study was to examine the abiotic processes that mobilize As from the aquifer solids during controlled exposure to chlorinated solutions. Thin sections made from sulfidic aquifer material were characterized by quantitative electron probe micro-analysis before and after 24 h exposure to solutions of different Cl₂ concentrations. Batch experiments using crushed aquifer solids were also conducted to examine changes in solution chemistry over 24 h. Results of the combined experiments indicate that Cl₂ addition affects As release and uptake in two ways. First, Cl₂ increases oxidation of sulfide minerals, releasing more As from the mineral structure. Chlorine addition also increases the rate of Fe(II) oxidation and subsequent hydrous ferric oxide (HFO) precipitation, allowing for increased uptake of As onto the mineral surface. Although HFOs can act as sinks for As, they can release As if biogeochemical conditions (e.g. redox, pH) change. These results have implications not only for disinfection of drinking water wells in the study area, but also suggest that introduction of oxidants may adversely affect water quality during aquifer storage and recovery programs in aquifers containing As-bearing minerals.     

On the separation of fine particles by centrifugation

An investigation of recovering finely divided mineral particles by centrifugal forces has been carried out.A theoretical analysis of the separation efficiency for various heavy minerals with density ranging between 5 and 19.3 g/cm³ against silica particles has been made initially. The size range considered in this study was 1–5 microns. The separation efficiency of these heavy minerals from silica was found to show typically a recovery over 95% with 80% purity.A system containing cassiterite and silica particles with 1–5 microns has been chosen as a model system in experiments. The experimental results were in good agreement with the theoretical predictions. Better separations were observed at higher pH's than pH 4 due to better dispersion of these minerals at the higher pH range.     

卡林型金矿自然重砂特征及其找矿意义——以黔西南地区为例

黔西南地区是中国西南低温成矿域中卡林型金矿最重要的矿化集中区,由于该地区金的粒径极小,难以构成自然重砂异常,故不能直接运用自然金矿物来指示寻找黔西南的卡林型金矿。在贵州省矿产资源潜力评价项目的工作过程中,对黔西南地区的自然重砂矿物特征进行了较为系统的研究,发现采用细粒黄铁矿(载金矿物)、砷矿物(伴生矿物)、锑矿物和汞矿物的自然重砂组(综)合异常对寻找黔西南地区的卡林型金矿具有一定的指导作用和找矿意义。     

Prograde and retrograde equilibria in garnet-cordierite gneisses in south-central Massachusetts

Partial electron microprobe analyses of garnet, biotite and cordierite in sillimanite-K feldspar gneisses of the Brimfield Formation in south-central Massachusetts indicate that the compositions of these minerals are not constant in a thin section. The FeO/MgO mol ratio of biotite is sensitive to the nature of other FeO-MgO minerals occurring in close proximity. The most iron-rich biotites are those that do not contact either cordierite or garnet. The most iron-poor biotites occur as inclusions in garnet. Biotites in direct contact with either cordierite or garnet have intermediate FeO/MgO ratios. The bulk of a given grain of garnet or cordierite is homogeneous in composition. Chemical zoning is absent. All grains of garnet and cordierite in a thin section are constant in composition. However, where garnet and cordierite abut biotite, the FeO/MgO ratio of the garnet rim is increased and that of cordierite is decreased. The FeO/MgO ratios of garnet, cordierite and biotite bare a regular relation to each other indicating a possible equilibrium state. However the distribution coefficient defined by the compositions of minerals in direct contact are greater than those defined by the compositions of the interiors of garnet and cordierite matched with the compositions of biotites removed from these phases. This pattern is believed to be the result of two thermal events. The first event produced the mineral assemblages and widespread equilibrium was obtained. A subsequent retrograde event left the mineralogy intact but caused cation exchange reactions at immediate contacts between garnet, cordierite and biotite. The physical conditions of the first event are estimated at P=5–6 kb, T=700–750° C. The retrograde event occurred at lower temperatures and very low activities of H₂O since no muscovite is developed at microcline-sillimanite contacts.     

Inducing mineral precipitation in groundwater by addition of phosphate

Background

Induced precipitation of phosphate minerals to scavenge trace elements from groundwater is a potential remediation approach for contaminated aquifers. The success of engineered precipitation schemes depends on the particular phases generated, their rates of formation, and their long term stability. The purpose of this study was to examine the precipitation of calcium phosphate minerals under conditions representative of a natural groundwater. Because microorganisms are present in groundwater, and because some proposed schemes for phosphate mineral precipitation rely on stimulation of native microbial populations, we also tested the effect of bacterial cells (initial densities of 10⁵ and 10⁷ mL^-1) added to the precipitation medium. In addition, we tested the effect of a trace mixture of propionic, isovaleric, formic and butyric acids (total concentration 0.035 mM).

Results

The general progression of mineral precipitation was similar under all of the study conditions, with initial formation of amorphous calcium phosphate, and transformation to poorly crystalline hydroxylapatite (HAP) within one week. The presence of the bacterial cells appeared to delay precipitation, although by the end of the experiments the overall extent of precipitation was similar for all treatments. The stoichiometry of the final precipitates as well as Rietveld structure refinement using x-ray diffraction data indicated that the presence of organic acids and bacterial cells resulted in an increasing a and decreasing c lattice parameter, with the higher concentration of cells resulting in the greatest distortion. Uptake of Sr into the solids was decreased in the treatments with cells and organic acids, compared to the control.

Conclusions

Our results suggest that the minerals formed initially during an engineered precipitation application for trace element sequestration may not be the ones that control long-term immobilization of the contaminants. In addition, the presence of bacterial cells appears to be associated with delayed HAP precipitation, changes in the lattice parameters, and reduced incorporation of trace elements as compared to cell-free systems. Schemes to remediate groundwater contaminated with trace metals that are based on enhanced phosphate mineral precipitation may need to account for these phenomena, particularly if the remediation approach relies on enhancement of in situ microbial populations.     

微生物对碳酸盐岩的风化作用

微生物-矿物相互作用可以促进许多表生生物地球化学反应过程,是表生地球化学研究的重要内容。通过综合岩石表面的微生物类群及其地质作用,分析碳酸盐岩微生物风化的各种现象,特别是微观尺度上的各种形态,阐述碳酸盐岩的微生物风化机制与风化产物,笔者提出微生物对碳酸盐岩风化的4种途径:(1)通过微生物在岩石表面和缝隙中生长,导致岩石表层发生生物溶蚀、生物磨蚀和生物钻孔作用,加速岩石风化进程;(2)微生物群体形成的钻孔网络可以增强岩石化学溶蚀的有效表面积并导致其表面强度减弱而促进机械侵蚀作用,微生物对周围岩石颗粒胶结结构的破坏、疏松作用也会导致岩石矿物颗粒的分解;(3)微生物的持水作用,微生物分泌的有机酸以及微生物呼吸所释放的CO2对岩表水分的酸化过程亦加速岩石矿物的分解;(4)微生物生长过程中从岩石内摄取营养元素和产生复杂的有机配体,能促进矿物元素的释放。文中提出在开展微生物对碳酸盐岩风化过程和机理研究的基础上,有必要引入微生物生物技术来综合开发本地低品位含钾磷矿产资源,加速岩溶地区山地土壤的形成与演化。     

真菌-玄武岩相互作用过程中真菌属种差异对元素释放行为的影响

真菌在矿物、岩石风化和元素溶解过程中发挥着重要作用。土壤中分布和生长着多种真菌,这些不同真菌在矿物和岩石风化,以及元素溶解过程中发挥的作用可能存在显著差异。为限定此差异,本研究从玄武岩风化土壤中分离获取了4种真菌(Aspergillus pesudofelis、Aspergillus viridinutans、Aspergillus undagawae和Aspergillus clavatus),设计批式溶解实验,探究了实验室条件下(28℃、30天内)4种真菌对玄武岩的风化作用,主要通过分析元素(包括Mg、Al、Si、Ca、Ti、Mn、Fe、Ni和Sr)的溶解速率和机制揭示不同属种真菌造成的玄武岩风化差异,并选取其中两种典型真菌所在的体系进行分析。实验结果显示不同属种真菌对玄武岩的风化和元素溶解的作用确实存在显著差异:1)与无机对照组相比,真菌A.pseudofelis的生长使得溶液pH值发生显著变化,元素的线性释放速率(Ril)显著升高;2)不同种真菌对体系pH值和Ril的影响差别巨大,且并非所有真菌均能加快玄武岩风化,如经过30天反应,含真菌A.pseudofelis体系溶液pH值上升了2.1,元素Mg的线性释放速率是无机对照组的22.5倍;而含真菌A.viridinutans体系溶液pH值仅上升了0.1,Mg的线性释放速率与无机对照组近似相等;3)Mg、Al、Ca、Ti元素的线性释放速率Ril最大值均出现在溶液最低pH值条件下,表明这4种元素的释放行为很大程度上受控于质子交换作用,而Fe和Ni的释放则由真菌代谢的草酸主导。由此可知,不同种真菌对有机酸代谢水平的差异影响了玄武岩中元素的释放行为。这也可能表明,在岩石早期风化过程中,具有较强有机酸(如草酸)代谢能力的真菌在Fe和Mg等生命必需元素的释放过程中起着重要作用。     

Solubilization of potassium containing minerals by high temperature resistant <Emphasis Type="Italic">Streptomyces</Emphasis> sp. isolated from earthworm’s gut

A potassium solubilizing bacterial strain designated EGT, which is tolerant of high temperature, was isolated from an earthworm’s gut to obtain a bacterium that can weather potassium-bearing rock effectively through solid-state fermentation. Molecular phylogeny and 16S rRNA gene sequence analysis demonstrated the bacterial strain was a member of the Streptomyces genus. To assess its potential to release potassium from silicate minerals, this strain was used to degrade potassium-bearing rock powder by solid-state fermentation. After fermentation, the amount of water-soluble Al, Fe and K of the substrate with active inoculum was higher than those of the control, which had autoclaved inoculum, and those of the fresh substrate. The result indicated that the strain had the ability to weather potassium-bearing rock and could be used as an inoculum in the production of potassium bio-fertilizer, due to its potassium release activity from rock and tolerance to high temperature.     

土壤固钾与释钾机制研究进展

根据钾素在土壤中对作物的有效性，可将其分为速效钾、缓效钾和无效钾。各种形态钾素之间存在着渐变性，并处于一种动态平衡，其中，土壤钾素固定与释放对这一平衡产生重要影响，进而影响钾素的有效性。富含 2∶ 1型粘土矿物的土壤，不仅有丰富的缓效钾储量和较强的供钾能力，而且固钾能力也较强。在淋溶性较强的砂质土壤上，固钾作用可使钾素免受淋失，有利于保存肥力和提高肥效。但是，对于多数土壤来说，将使施入土壤的大部分钾素转化为非交换性钾，其中，只有小部分可被当季作物利用。在集约农业条件下，土壤的固定已成为提高钾素利用效率的主要障碍因素。系统阐述了钾素释放与固定的概念与过程，综述了影响钾素固定与释放的主要因素；系统分析了粘土矿物类型及其结构、土壤铵态氮肥和磷肥水平、土壤水分状况、有机物和羟基铝影响钾素固定、释放过程的作用机理；并指出了土壤钾素固定和释放研究领域的发展现状和重要动向。     

含钾岩石微生物转化的分子机制及其碳汇效应

岩石矿物的微生物风化是地球表层系统最为活跃和普遍发生的地质营力之一。微生物对含钾岩石(以硅酸盐矿物为主)的风化能够释放其中的钾、硅和钙等元素,并在合适的环境条件下促进矿物元素的碳酸化沉淀,这是地表元素地球化学循环的重要环节之一。微生物对岩石的生物转化作用既涉及微生物的生长繁殖和代谢调控,也与元素的迁移转化和次生矿物的演化序列有关,具有重要研究价值。采用矿物学、微生物学和分子生物学等相结合的研究方法,有助于系统地研究微生物促进含钾硅酸盐矿物的风化并耦联碳酸化过程及其分子调控机制。研究证实,在纯培养条件下,微生物风化含钾矿物主要采用酸解、螯合、氧化还原等多种方式的协同作用,并可通过调控相关功能基因的表达来响应缺钾的环境以实现其对含钾矿物的有效风化,显然这有赖于微生物通过长期进化而形成的精细的分子调控机制。在土壤生态环境中,微生物对矿物风化的显著特征是该生态环境中微生物群落协同互作的群体作用效应。微生物碳酸酐酶参与的硅酸盐矿物风化伴随碳酸盐矿物的形成过程可能是个长期被忽视的地表碳增汇过程,对该问题的深入探索有助于进一步理解地质演化历史中微生物对碳素迁移转化的驱动机制。加入含钾硅酸盐矿粉的有机肥已经显示出其在土壤改良、作物生长和增加土壤碳汇等方面的正面应用效果,这为利用硅酸盐矿物的生物风化作用来延缓大气CO₂浓度的持续升高提供了新的思路。介绍了有关微生物对含钾岩石生物转化释放钾素的分子机理及其碳汇效应方面的研究进展,以期抛砖引玉,推动该领域研究的快速发展。     

使用微观试验确定软土中晶质矿物的类型与含量

土中矿物成分的类型与含量是软土物理力学性质研究的基础,可以使用微观试验进行研究。本次研究以上海软土为例,使用X射线荧光（XRF）分析得到土中不同元素的含量,使用X射线衍射（XRD）分析和XRF分析得到了晶质矿物的类型,根据元素含量和矿物类型得到不同矿物的含量,对不同土层中矿物含量的分布特征进行了分析。结果表明,上海软土主要矿物中的元素为O,Si,Al,Fe,C,K,Mg,Ca和Na;所有土层中,元素含量最多的是O,其次是Si,主要矿物成分为石英、钠长石、方解石、白云石、伊利石、鲕绿泥石和黑云母,石英的含量最高、含量为35.8%~50.8%,其它矿物的含量均不超过21%;黏性土中,元素Al要略多于砂性土或粉性土,伊利石和鲕绿泥石含量明显高于砂性土或粉性土,钠长石和方解石含量要明显小于砂性土或粉性土。研究结果对从微观上研究不同土的物理力学性质有一定的参考价值。     

Biotite weathering and nutrient uptake by ectomycorrhizal fungus, Suillus tomentosus, in liquid-culture experiments

Ectomycorrhiza-forming fungi (EMF) alter the nutrient-acquisition capabilities of vascular plants, and may play an important role in mineral weathering and the partitioning of products of weathering in soils under nutrient-limited conditions. In this study, we isolated the weathering function of Suillus tomentosus in liquid-cultures with biotite micas incubated at room temperature. We hypothesized that the fungus would accelerate weathering by hyphal attachment to biotite surfaces and transmission of nutrient cations via direct exchange into the fungal biomass. We combined a mass-balance approach with scanning electron microscopy (SEM) and atomic force microscopy (AFM) to estimate weathering rates and study dissolution features on biotite surfaces. Weathering of biotite flakes was about 2-3 orders of magnitude faster in shaken liquid-cultures with fungus compared to shaken controls without fungus, but with added inorganic acids. Adding fungus in nonshaken cultures caused a higher dissolution rate than in inorganic pH controls without fungus, but it was not significantly faster than organic pH controls without fungus. The K⁺, Mg²⁺ and Fe²⁺ from biotite were preferentially partitioned into fungal biomass in the shaken cultures, while in the nonshaken cultures, K⁺ and Mg²⁺ was lost from biomass and Fe²⁺ bioaccumulated much less. Fungal hyphae attached to biotite surfaces, but no significant surface changes were detected by SEM. When cultures were shaken, the AFM images of basal planes appeared to be rougher and had abundant dissolution channels, but such channel development was minor in nonshaken conditions. Even under shaken conditions the channels only accounted for only 1/100 of the total dissolution rate of 2.7 × 10⁻¹⁰ mol of biotite m⁻² s⁻¹. The results suggest that fungal weathering predominantly occurred not by attachment and direct transfer of nutrients via hyphae, but because of the acidification of the bulk liquid by organic acids, fungal respiration (CO₂), and complexation of cations which accelerated dissolution of biotite. Results further suggest that both carbohydrate source (abundant here) and a host with which nutrients are exchanged (missing here) may be required for EMF to exert an important weathering effect in soils. Unsaturated conditions and physical dispersal of nutrient-rich minerals in soils may also confer a benefit for hyphal growth and attachment, and promote the attachment-mediated weathering which has been observed elsewhere on soil mineral surfaces.