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1.
几种亚热带土壤铁锰胶膜和基质的表面化学特征 总被引：1，自引：0，他引：1
以我国亚热带的黄褐土、黄棕壤和红壤为材料,研究了土壤铁锰胶膜和其基质的表面化学性质及其对重金属元素的吸附和氧化特点。结果表明,与基质土壤相比,铁锰胶膜的比表面积大,电荷零点(PZC)低,这与其富含粘粒、有机质和铁锰氧化物等有关;铁锰胶膜经脱锰处理后,比表面积明显降低。由盐滴定-电位滴定(STPT)法测得黄褐土、黄棕壤、红壤基质的PZC分别为3.13、3.65和3.90;黄棕壤和红壤铁锰胶膜的PZC分别为3.26和3.42。铁锰胶膜对Pb2 、Cu2 、Cd2 和Zn2 的吸附和对Cr3 的氧化能力比基质的强。铁锰胶膜经脱锰处理后,对Pb2 、Cu2 、Cd2 和Zn2 的最大吸附量比未处理时降低了53%～100%;其氧化Cr3 生成Cr6 的量比铁锰胶膜的降低了87%～100%。说明黄褐土、黄棕壤和红壤的铁锰胶膜中,氧化锰是吸附重金属离子和氧化Cr3 的主体。 相似文献
2.
本文采集了3种典型的富锰沉积物样品,即岩石漆、树枝晶与土壤铁锰胶膜,并制作了相应的纵切片。运用光学显微镜、原位微区拉曼光谱仪、扫描电镜、EDX能谱仪分别对其形貌学与矿物学特征进行了研究。结果表明岩石漆呈黑色致密层状、葡萄状,主要由水钠锰矿、赤铁矿、针铁矿、粘土矿物等组成,是一种高度混杂的沉积物。宏观上岩石漆与基岩有截然的接触面,发育有微层理结构,在微观上的表现即锰含量的周期性波动。树枝晶呈黑色分枝状,主要由锰钡矿组成,极端富锰而贫硅铝,与基质呈交织结构。土壤铁锰胶膜呈黑色粘稠层状,由水钠锰矿、赤铁矿、针铁矿、钛铁矿、粘土矿物等组成,可细分为外层黑褐色的富锰条带和内层黄棕色的富铁条带。这3种富锰沉积物的形貌学和元素分布特征与各自的成因机制密切相关。 相似文献
3.
新生代深海铁锰矿床的大规模成矿是地质历史上特有的现象,其形成的海底铁锰结核/结壳因富含巨量的有用金属而备受关注。水成型铁锰成矿的胶体成因模型自20世纪90年代中期提出以来已被广泛接受并采用。随着近20年来纳米地球科学的迅速发展,人们意识到纳米颗粒作为胶体的最小部分,能够以其独特的性质显著影响铁锰成矿过程。通过总结已有研究,发现铁氧化物与锰氧化物会以纳米颗粒的形式普遍共存于多种表生地质环境,还证实了水成型铁锰结核/结壳中的主要铁锰矿物（如水羟锰矿和水铁矿）都是纳米颗粒。铁氧化物纳米颗粒对二价锰[Mn(Ⅱ)]的表面催化氧化可能是水成型铁锰矿物通常在纳米尺度密切共生的原因。此外,在铁锰结壳中还观测到大量在以往研究中被普遍忽视的三价锰[Mn(Ⅲ)]矿物,其含量在结壳顶部最高,随深度增加逐渐下降,四价锰[Mn(Ⅳ)]矿物的含量则呈相反的变化趋势。不同价态锰氧化物纳米颗粒的表面能差异导致Mn(Ⅲ)矿物在Mn(Ⅱ)的氧化过程中最先沉淀,并可能在沉淀之后逐渐转化为Mn(Ⅳ)矿物。相信随着纳米地球科学与高精度原位实验技术的发展,必将不断深化对海水铁锰循环及海底铁锰成矿的认识。 相似文献
4.
广西下雷氧化锰矿床矿石特征及成因分析 总被引：3，自引：0，他引：3
广西下雷锰矿床由原生碳酸锰矿和次生氧化锰矿组成.其中氧化锰矿石的矿物主要有软锰矿、钡锰矿、隐钾锰矿、锂锰矿、钙锰矿、褐锰矿、黑镁铁锰矿等,与之伴生的其他表生矿物主要有赤铁矿、针铁矿、石英、高岭石和蒙脱石.矿石结构主要有交代、隐晶和细晶结构,矿石构造主要有葡萄状、块状、晶洞状、网脉状和条带状构造.与原生碳酸锰矿相比,次生氧化锰矿的矿石品位明显提高,平均在44%以上;Co、Ni、Cu、Zn等微量元素也有一定程度的富集.化学分析和单矿物成分分析结果表明,氧化锰矿石和锰氧化物中的w(Mn)/w(TFe)值均较高(一般大于10),说明风化强度大,铁、锰分离显著.与铁的氧化物相比,锰氧化物中Si和P等有害杂质元素的含量要低得多,因此,铁、锰分离是形成优质锰矿的重要条件.氧化锰矿的次生富集及其在空间上的分布受古气候、构造、含锰地层及地形地貌等多种因素的影响和控制. 相似文献
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6.
《吉林大学学报(地球科学版)》2015,(Z1)
<正>在干旱—半干旱环境中的岩石表面常有黑色薄膜状岩石漆发育,在内陆沙漠、海滨沙漠、南北极地、高山、洞穴、岩石裂隙等陆生风化环境中皆有分布,其主要包含黏土矿物、铁锰氧化物、有机质等成分。无独有偶,在亚热带地区的表层红壤中也存在着类似的"薄膜",其中的铁锰氧化物矿物晶粒小至纳米级,这些矿物"薄膜"多附着于土壤基质表面,亦被称为矿物胶膜。本研究采用同步辐射微区X射线衍射和透射电子显微镜技术对表层红壤铁氧化物矿物胶膜中铁氧化物矿物的成分与结构进行了矿物学表征。 相似文献
7.
以石英砂为载体在其颗粒表面合成锰胶膜运用X射线衍射(XRD)和扫描电镜(SEM)等手段对胶膜中矿物的结构进行表征,探讨体系中不同锰摩尔比R(Mn~(2+)、Mn~(7+)摩尔比分别为1:1、1:2、1:3、1:4)、合成温度(30、50、70、90、110℃)、搅拌时间(48、72、96 h)和石英砂添加量(5、10、20、30、40 g)等因素对锰胶膜合成的影响。研究结果表明,随着R的减小,锰胶膜中的锰钾矿向水钠锰矿转化且矿物的结晶度增大,锰含量减小,晶体颗粒逐渐增大;随着温度的升高,胶膜中矿物的结晶度增大,锰含量下降,但矿物类型没有变化;搅拌不会影响胶膜的矿物类型,但搅拌时间越长胶膜中锰矿物含量越高;随石英砂添加量的增大胶膜中锰矿物类型不变,但其结晶度减弱,锰含量先降低但在石英砂添加量为10 g时开始升高。 相似文献
8.
莫托萨拉铁锰矿床位于西天山阿吾拉勒成矿带东端,研究程度相对薄弱,在矿床成因方面存在热水沉积、沉积-热液改造、胶体化学沉积等争论。本文详细研究了莫托萨拉最上层锰矿及其围岩的矿物组成、结构构造和地球化学特征,并综合前人资料对整个铁锰矿床的成因做了进一步探讨。本研究首次在矿区发现了热液长石岩,其主要由钠长石、钾长石以及少量重晶石、霓石、锌铁黄长石等矿物组成,类似于"白烟型"热水沉积岩。莫托萨拉最上层锰矿主要由锰橄榄石、褐锰矿、红硅锰矿、磁锰铁矿以及少量重晶石、方铁锰矿等矿物组成,发育有典型的热水内碎屑结构,指示其沉积于海底热液喷流口附近。该层锰矿的Al/(Al+Fe+Mn)值很低(0～0.02)、Si/Al值较高(7.9～10.9)、Fe/Ti值很高(428～1353),通过UCC标准化后发现明显富集Zn、Ba、Pb等元素,而Co、Ni、Cu等元素未见富集,以上地球化学特征与现代海底热液成因铁锰沉积物一致。在Fe/Ti-Al/(Al+Fe+Mn)、Si O2-Al2O3、10×(Co+Ni+Cu)-Fe-Mn、100×(Zr+Ce+Y)-15×(Cu+Ni)-(Fe+Mn)/4等判别图中,莫托萨拉的锰矿层和铁矿层样品均落在海底热液沉积区。锰矿层和铁矿层的稀土元素经PAAS标准化后具有明显的Ce负异常、Eu正异常和Y正异常,与现代海底热液成因铁锰沉积物的稀土配分模式非常相似。综合分析本次研究的矿物学、岩石学、地球化学特征以及前人资料,本文认为莫托萨拉铁锰矿床为海相热水沉积成因,成矿与同期海底火山的间歇性活动密切相关,海底热液的化学组分、温度高低和活动强弱都具有明显的脉动性。莫托萨拉矿区铁锰共存但各自独立成矿,且铁锰分离程度较高,这在显生宙沉积型锰矿中独具特色。鉴于前人曾报道莫托萨拉铁矿石中存在菌藻类微生物化石,我们推测,该矿床的铁锰分离过程除了受控于沉积环境的氧化还原条件变化外,微生物的选择性氧化沉淀可能也发挥了重要作用,值得开展深入研究。 相似文献
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华中地区几种土壤铁锰胶膜及其基质中某些元素的地球化学特点 总被引：5，自引：1，他引：5
通过对华北地区几种土壤和胶膜中某些性质及元素的相关分析和因子分析。比较了铁锰胶膜和基质土壤的性质及元素含量之间的关系。研究表明，（1）铁锰胶膜的pH值，粘粒含量，K2O,Na2O,MnO2，非晶质铁，铁的活化度，微量元素等的含量均比基质土壤的高，且差异显著；（2）铁锰胶膜富集重金属元素，Co,Ni,Cu和Zn等元素主要富集于胶膜的氧化锰矿物中，而Pb主要富集在氧化铁矿物中；（3）Mg在铁锰胶膜的形成过程中进一步淋溶，以致含量减少。 相似文献
10.
富钴结壳是一种重要的海底矿产资源,具有独特的经济价值和科学意义,其不仅富含Mn、Co、Ni、Cu、PGE和REY等金属,而且在反演新生代以来古海洋环境记录等方面扮演着独特的角色。锰氧化物(MnO2·xH2O)和铁羟基氧化物(FeOOH)是构成富钴结壳的主要矿物,矿物颗粒十分微小(纳米级)。水羟锰矿和水钠锰矿具有层状结构且层电荷为负,通过吸附阳离子来补偿。前人通过连续浸出实验、元素相关性统计分析、吸附实验和拓展X射线吸收精细结构(EXAFS)光谱广泛研究了微量元素在矿物中的赋存状态,确定了微量元素在锰氧化物矿物中主要存在三种类型络合物:共六边(edge-sharing)、共双角(double-corner sharing)和共三角(triple-corner sharing)。综合研究表明,在最低含氧带之下铁锰氧化物(氢氧化物)从海水沉淀到周围海山坚硬基岩上形成富钴结壳的机制主要是无机胶体化学反应和矿物表面反应。最后针对已有的相关研究现状以及富钴结壳研究面临的挑战,富钴结壳的成矿物质来源及演化、微量元素富集机制、蕴含的古海洋信息等问题仍需要进一... 相似文献
11.
几种亚热带淋溶土基质和胶膜中1.4 nm过渡矿物组成的差异及其意义 总被引：5，自引：1，他引：5
以我国亚热带的黄褐土和黄棕壤的铁锰－粘粒混合胶膜为材料，分析了胶膜及其相应的淋溶土在粘土矿物类型和含量上的差别。研究结果表明：土壤和胶膜的粘土矿物均由1.4nm矿物、水云母、高岭石组成，土壤的1.4nm矿物为1.4nm过渡矿物和蛭石的混合相，而胶膜的1.4nm矿物全部由蛭石组成。由此认为，胶膜中的1.4nm过渡矿物主要来源于表层粘粒的淀积和裂隙周围基质土壤中粘土矿物的转化，胶膜的有机质含量、交换性盐基总量等性质明显不同于基质土壤，其微环境抑制了土壤中的蛭石向1.4nm过渡矿物的转化，并导致1.4nm过渡矿物向蛭石的转化。 相似文献
12.
《Applied Geochemistry》2004,19(6):973-979
The association of rare earth and other trace elements with Fe and Mn oxides was studied in Fe-Mn-nodules from a lateritic soil from Serra do Navio (Northern Brazil). Two improved methods of selective dissolution by hydroxylamine hydrochloride and acidified hydrogen peroxide along with a classical Na–citrate–bicarbonate–dithionite method were used. The two former reagents were used to dissolve Mn oxides without significant dissolution of Fe oxides, and the latter reagent was used to dissolve both Mn and Fe oxides. Soil nodules and matrix were separated by hand. Inductively coupled plasma atomic emission spectrometry and inductively coupled plasma mass spectrometry after fusion with lithium metaborate, and X-ray diffraction were used to determine the elemental and mineralogical composition of the nodules and soil matrix. The latter was composed of kaolinite, gibbsite, goethite, hematite, and quartz. In the nodules, lithiophorite LiAl2(MnIV2MnIII)O6(OH)6 was detected in addition to the above-mentioned minerals. The presence of hollandite (BaMn8O16) and/or coronadite (PbMn8O16) in the nodules is also possible. In comparison to the matrix, the nodules were enriched in Mn, Fe, K, and P, and relatively poor in Si, Al, and Ti. The nodules were also enriched in all trace elements determined. Phosphorus, As and Cr were associated mainly with Fe oxides; Cu, Ni, and V were associated with both Fe and Mn oxides; and Ba, Co, and Pb were associated mainly with Mn oxides. Distribution of rare earth elements indicated a strong positive Ce-anomaly in the nodules, compared to the absence of any anomaly in the matrix. Some of Ce was associated with Mn oxides. The improved methods achieved almost complete release of Mn from the sample without decreasing the selectivity of dissolution, i.e., without dissolving significant amounts of Fe oxides and other minerals, and provided reliable information on associations of trace elements with Mn oxides. These methods are thus proposed to be included in sequential extraction schemes for fractionation of trace elements in soils and sediments. 相似文献
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The most important source of yellow gem elbaite is the Canary mining area in the Lundazi District of eastern Zambia. The tourmaline has been mined since 1983 from both pegmatite and eluvial/alluvial deposits, in colors typically ranging from yellow-green to yellow to orange and brown; much of the orange-to-brown material is heated to attain a ‘golden’ or ‘canary’ yellow color. The elbaite is Mn-rich (up to 9.18 wt% MnO documented in the literature) and contains small amounts of Ti and little or no Fe. The distinctive composition of this tourmaline is probably the result of the early crystallization of abundant schorl from an unusual B-rich, Li-poor pegmatite melt, which depleted Fe while conserving Mn until the late-stage crystallization of gem pockets. The simple mineralogy of the pegmatite consists of feldspars, quartz, and tourmaline; the lack of micas, phosphates, or Li minerals, and the presence of very little garnet, allowed Mn to fractionate to high levels during pegmatite crystallization. The presence of abundant gem tourmaline in a Li-poor pegmatite is highly unusual. 相似文献
14.
The elemental geochemistry of major, minor and trace elements in iron–manganese cutans and the corresponding matrix soils, collected from three Alfisols in central China, are studied using their chemical compositions as well as correlation and factor analyses. Fe–Mn cutans accumulate high concentrations of MnO2 and Fe2O3. Mean values of these two elements in cutans are about 13.7 and 1.4 times higher than those in the matrix soils. pH, clay contents, extractable X-ray noncrystalline Fe (Feo) and the ratio of Feo to free Fe-oxide (Fed) in cutans are notably higher than those in the corresponding matrices. Cutans are also enriched in some bases and heavy metals. Averages of K, Na, Co and Pb concentrations are about 2.0, 1.4, 15.4 and 6.0 times higher than those in the matrices. Statistical analysis indicates that Co, Ni, Li, Cu and Zn are abundant in Mn minerals of cutans, while Pb exists mainly in iron minerals. Fe–Mn cutans constitute an active microzone of solid–solution–plant–air interaction, element movement and exchange in soils, which cause the contents of Fe- and Mn-oxides, elemental concentrations, and geochemical behavior of cutan to show marked differences in matrix soils. 相似文献
15.
Subterranean estuaries are characterized by the mixing of terrestrially derived groundwater and seawater in a coastal aquifer. Subterranean estuaries, like their river water-seawater counterparts on the surface of the earth, represent a major, but less visible, hydrological and geochemical interface between the continents and the ocean. This article is the first in a two-part series on the biogeochemistry of the subterranean estuary at the head of Waquoit Bay (Cape Cod, MA, USA). The pore-water distributions of salinity, Fe and Mn establish the salt and redox framework of this subterranean estuary. The biogeochemistry of Fe, Mn, P, Ba, U and Th will be addressed from the perspective of the sediment composition. A second article will focus on the groundwater and pore-water chemistries of Fe, Mn, U and Ba.Three sediment cores were collected from the head of Waquoit Bay where the coastal aquifer consists of permeable sandy sediment. A selective dissolution method was used to measure the concentrations of P, Ba, U and Th that are associated with “amorphous (hydr)oxides of iron and manganese” and “crystalline Fe and Mn (hydr)oxides.” The deeper sections of the cores are characterized by large amounts of iron (hydr)oxides that are precipitated onto organic C-poor quartz sand from high-salinity pore waters rich in dissolved ferrous iron. Unlike Fe (hydr)oxides, which increase with depth, the Mn (hydr)oxides display midcore maxima. This type of vertical stratification is consistent with redox-controlled diagenesis in which Mn (hydr)oxides are formed at shallower depths than iron (hydr)oxides. P and Th are enriched in the deep sections of the cores, consistent with their well-documented affinity for Fe (hydr)oxides. In contrast, the downcore distribution of Ba, especially in core 3, more closely tracks the concentration of Mn (hydr)oxides. Even though Mn (hydr)oxides are 200-300 times less abundant than Fe (hydr)oxides in the cores, Mn (hydr)oxides are known to have an affinity for Ba which is many orders of magnitude greater than iron (hydr)oxides. Hence, the downcore distribution of Ba in Fe (hydr)oxide rich sediments is most probably controlled by the presence of Mn (hydr)oxides. U is enriched in the upper zones of the cores, consistent with the formation of highly reducing near-surface sediments in the intertidal zone at the head of the Bay. Hence, the recirculation of seawater through this type of subterranean estuary, coupled with the abiotic and/or biotic reduction of soluble U(VI) to insoluble U(IV), leads to the sediments acting as a oceanic net sink of U. These results highlight the importance of permeable sediments as hosts to a wide range of biogeochemical reactions, which may be impacting geochemical budgets on scales ranging from coastal aquifers to the continental shelf. 相似文献
16.
Siderophores are biogenic chelating agents produced in terrestrial and marine environments that increase the bioavailability of ferric iron. Recent work has suggested that both aqueous and solid-phase Mn(III) may affect siderophore-mediated iron transport, but scant information appears to be available about the potential roles of layer type manganese oxides, which are relatively abundant in soils and the oligotrophic marine water column. To probe the effects of layer type manganese oxides on the stability of aqueous Fe-siderophore complexes, we studied the sorption of ferrioxamine B [Fe(III)HDFOB+, an Fe(III) chelate of the trihydroxamate siderophore desferrioxamine B (DFOB)] to two synthetic birnessites [layer type Mn(III,IV) oxides] and a biogenic birnessite produced by Pseudomonas putida GB-1. We found that all of these predominantly Mn(IV) oxides greatly reduced the aqueous concentration of Fe(III)HDFOB+ at pH 8. Analysis of Fe K-edge EXAFS spectra indicated that a dominant fraction of Fe(III) associated with the Mn(IV) oxides is not complexed by DFOB as in solution, but instead Fe(III) is specifically adsorbed to the mineral structure at multiple sites, thus indicating that the Mn(IV) oxides displaced Fe(III) from the siderophore complex. These results indicate that layer type manganese oxides, including biogenic minerals, may sequester iron from soluble ferric complexes. We conclude that the sorption of iron-siderophore complexes may play a significant role in the bioavailability and biogeochemical cycling of iron in marine and terrestrial environments. 相似文献
17.
Comparison of trace metal adsorption onto different solid materials and their chemical components in a natural aquatic environment 总被引：1，自引：0，他引：1
Solid materials such as suspended particulate matter (SPM), deposited sediment (DS) and natural surface coatings (NSC, composed of biofilms and associated minerals) are important sinks and potential sources of pollutants in natural aquatic environments. Although these materials can exist in the same water body, few studies have been conducted to compare their ability to adsorb trace metals. In this study, the adsorption of Pb, Cu and Cd by these solids, collected from an urban lake, was investigated. In addition, the metal adsorption properties of the main components of these solids, namely Mn and Fe oxides and organics, were also investigated using the method of selective extraction followed by metal adsorption. The solids that co-existed in water showed similarities and differences in their compositions. For each metal, adsorption to the solids occurred in the same order: NSC > SPM > DS. For Pb and Cd, Fe and Mn oxides and organics contributed to the adsorption by NSC and SPM, and the adsorption by DS was dominated by Fe oxides. For Cu, the organics were the main adsorptive phase. The specific adsorption capability of these components decreases in the following order: Mn oxides > Fe oxides > organics. Overall, the results presented herein indicate that different solids and their components played important roles in the adsorption of trace metals. 相似文献
18.
Chemical and structural control of the partitioning of Co, Ce, and Pb in marine ferromanganese oxides 总被引：3，自引：0，他引：3
Yoshio Takahashi Alain Manceau Matthew A. Marcus 《Geochimica et cosmochimica acta》2007,71(4):984-1008
The oxidation state and mineral phase association of Co, Ce, and Pb in hydrogenetic, diagenetic, and hydrothermal marine ferromanganese oxides were characterized by X-ray absorption near-edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) spectroscopy and chemical extraction. Cobalt is trivalent and associated exclusively with the Mn oxide component (vernadite). Cerium is tetravalent in all genetic-type oxides (detection limit for Ce(III) ∼ 5 at. %), including Fe-rich areas (ferrihydrite) of hydrogenetic oxides, and is associated primarily with vernadite. Thus, the extent of a Ce anomaly does not result from variations in redox conditions, but appears to be kinetically controlled, decreasing when the growth rate increases from hydrogenetic to diagenetic to hydrothermal oxides. Lead is divalent and associated with Mn and Fe oxides in variable proportions. According to EXAFS data, Pb is mostly sorbed on edge sites at chain terminations in Fe oxide and at layer edges in Mn oxide (ES complex), and also on interlayer vacancy sites in Mn oxide (TCS complex). Sequential leaching experiments, spectroscopic data, and electrochemical considerations suggest that the geochemical partitioning in favor of the Mn oxide component decreases from Co to Ce to Pb, and depends on their oxidative scavenging by Mn and Fe oxides. 相似文献
19.
Iron and manganese redox cycling in the sediment — water interface region in the Kalix River estuary was investigated by using sediment trap data, pore-water and solid-phase sediment data. Nondetrital phases (presumably reactive Fe and Mn oxides) form substantial fractions of the total settling flux of Fe and Mn (51% of Fetotal and 84% of Mntotal). A steady-state box model reveals that nondetrital Fe and Mn differ considerably in reactivity during post-depositional redox cycling in the sediment. The production rate of dissolved Mn (1.6 mmol m–2 d–1) exceeded the depositional flux of nondetrital Mn (0.27 mmol m–2 d–1) by a factor of about 6. In contrast, the production rate of upwardly diffusing pore-water Fe (0.77 mmol m–2 d–1) amounted to only 22% of the depositional flux of nondetrital Fe (3.5 mmol m–2 d–1). Upwardly diffusing pore-water Fe and Mn are effectively oxidized and trapped in the oxic surface layer of the sediment, resulting in negligible benthic effluxes of Fe and Mn. Consequently, the concentrations of nondetrital Fe and Mn in permanently deposited, anoxic sediment are similar to those in the settling material. Reactive Fe oxides appear to form a substantial fraction of this buried, non-detrital Fe. The in-situ oxidation rates of Fe and Mn are tentatively estimated to be 0.51 and 0.16–1.7 mol cm–3 d–1, respectively. 相似文献