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961.
Theoretical analysis and computational simulations have been carried out to investigate how medium and pore‐fluid compressibility affects the chemical‐dissolution front propagation, which is associated with a fully‐coupled nonlinear problem between porosity, pore‐fluid pressure, pore‐fluid density and reactive chemical‐species transport within a deformable and fluid‐saturated porous medium. When the fully‐coupled nonlinear system is in a subcritical state, some analytical solutions have been derived for a special case, in which the ratio of the equilibrium concentration to the solid molar density of the chemical species is approaching zero. To investigate the effect of either medium compressibility or pore‐fluid compressibility on the evolutions of chemical dissolution fronts in supercritical chemical dissolution systems, numerical algorithms and procedures have been also proposed. The related theoretical and numerical results have demonstrated that: (i) not only can pore‐fluid compressibility affect the propagating speeds of chemical dissolution fronts in both subcritical and supercritical systems, but also it can affect the growth and amplitudes of irregular chemical dissolution fronts in supercritical systems; (ii) medium compressibility may have a little influence on the propagating speeds of chemical dissolution fronts, but it can have significant effects on the growth and amplitudes of irregular chemical dissolution fronts in supercritical systems; and (iii) both medium and pore‐fluid compressibility may stabilize irregular chemical‐dissolution‐fronts in supercritical chemical dissolution systems. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
962.
William C. Mahaney Volli Kalm Ronald G. V. Hancock Fred Michel Barbara Kapran 《第四纪科学杂志》2010,25(2):178-189
The concentrations of major, minor and trace elements in three Cryosols from northwestern Siberia were analysed to determine profiles of geochemical uniformity, element mobility and the release and build‐up of extractable Fe and Al. The scope of this study involves weathering processes over all or part of the Lateglacial to the Holocene Epoch (<10 ka) in a cold environment. Iron and Al extracts are investigated to elicit information regarding profile age and palaeoclimate. ‘Free’ iron (Fed) relative to total Fe increases in the Ah + Bw horizons compared with the lower horizons, where oxidation is weaker. Low total Fe reflects reworked felsic deltaic and shallow marine deposits from the Permian to the early Tertiary, thereafter emplaced by episodic flooding of glacial meltwater from the Arctic Urals and/or the Kara Sea Ice Sheet. Organically complexed Al (Alp), uniformly low in all soils, nevertheless shows trends indicating some downward movement, a rather unique occurrence in Arctic tundra soils. As indicated by the slow increase of oxihydrites, it may not be realistic to estimate the age of a profile by its physical characteristics. However, it appears possible to determine broad age ranges from the isotopic composition of water in soils. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
963.
Abstract The deposition of chemical elements in a catchment occurs through three different processes: wet, dry and cloud deposition. Total deposition cannot be inferred from measurements made with open-field raingauges, and still constitutes a challenge to scientific method. The chemical composition of samples from an open-field raingauge (bulk precipitation) was analysed over a period of several years in a small Mediterranean catchment in the Maures Massif, France. The input of chloride measured in this way was two times lower than the output, despite the fact that this element is reputed to be conservative, which means input and output should roughly balance. This implies that input has previously been underestimated. Analysis of the bulk precipitation data was carried out taking into account both the history of rain events and of sampling. This study allowed the relative parts of the different deposition processes to be quantified. Dry deposition can provide from 20% to more than 80% of the anthropogenic and terrigenic elements (Ca2+, Mg2+, K+, NO3 ?, SO4 2-, SiO2) to the rain samples. The occult deposition of marine elements on the catchment area (50% of total deposition) was found to be mostly due to cloud deposition during wet periods. 相似文献
964.
Altered crystalline rocks occur at the peneplain exposed in southern Israel and in other localities across North Africa and Arabia where they underlie an extensive blanket of Cambro–Ordovician sandstones. This study focuses on the petrography, mineralogy and geochemistry of top basement rocks of the northern Arabian‐Nubian Shield. The altered rocks are shown to be weathering profiles that can be subdivided into three horizons interpreted as apparently unweathered granite, or saprock, which grades upwards to a saprolite, topped by a thin clayey plasmic zone. The plasmic zone is enriched in iron and aluminium and is depleted in silicon, calcium, magnesium and potassium relative to the underlying saprolite. The chemical index of alteration increases upward, but does not exceed 90 and, therefore, lags behind values observed in strongly leached present‐day tropical soils. Petrographic examinations reveal iron mobility under local fluctuating redox conditions, similar to modern and Proterozoic soils. A variety of birefringence fabrics induced by shrinkage and expansion of clays during wetting and drying cycles and clay illuviation strongly indicate pedogenic processes rather than a post‐depositional alteration. Illite and ordered illite‐smectite phases coexist with smectitic illite‐smectite in the lower part of the saprolite and with kaolinite in the plasmic zone, in line with increasing chemical index of alteration. Observations are in accordance with the current profile being a remnant of a thick weathering profile whose top was truncated by fluvial incision just prior to deposition of the overlying Early Cambrian sequence. A previously documented Devonian thermal event reaching temperatures of at least 200°C overprinted the studied rocks. During burial diagenesis, illitization affected original smectite rather than kaolinite. However, in spite of the elevated temperatures, illitization was incomplete implying restricted potassium addition. The sub‐Cambrian weathering reflects warm and humid conditions in a tropical or sub‐tropical climate, in line with several plate reconstructions placing Israel at low latitudes during Cambrian time. 相似文献
965.
地下水是很重要的一部分水体,它与地表水不同,对人类的水源提供具有很重要的意义,然而在工程建设中,由于地下水的特殊性和其化学成分,对钢筋混凝土具有很大的侵蚀性。文章中采用化学分析的方法,对地下水进行分析,获取水中的物质定量指标,评价其对工程建筑的作用和影响。 相似文献
966.
改进BCR法测定公路两旁表层土壤中铂钯铑的化学形态 总被引:3,自引:2,他引:1
铂、钯、铑是汽车催化转换器中的主要成分,在有效治理汽车尾气污染的同时,不断排放并在环境中累积增加,随着元素的迁移、转化及地下水的循环,可能成为一种新的环境污染问题.本文将改进的BCR顺序提取法应用于铂族元素形态分析,结合铂族元素的性质,将公路两旁表层土壤样品中Pt、Pd、Rh分为酸溶态、可还原态、可氧化态和残渣态四种形态.实验优化了原始的BCR浸取条件,利用电感耦合等离子体质谱法测定Pt、Pd、Rh的各形态.各形态的精密度、检出限满足地质矿产实验室测试质量管理规范的监控要求,各形态浸取量之和与样品各元素的总量之比(回收率)在95.3% ~ 110.0%,说明方法具有较好的准确性和重现性.通过实际样品分析,公路两旁表层土壤样品中铂族元素非残渣态含量顺序为Pd (57.23% ~ 58.03%)>Rh (22.64% ~25.80%) >Pt(17.91 ~20.57%),研究认为铂族元素进入生物圈的几率是Pd> Rh> Pt. 相似文献
967.
新矿物汉江石的理想分子式为Ba2CaV23+[(Si3AlO10)(OH)2]F(CO3)2。矿物呈黄绿色、深绿色,显微镜下呈浅绿色、淡绿色;单斜晶系,空间群为C2,a=0.52050(12)nm,b=0.9033(2)nm,c=3.2077(8)nm,β=93.49(8)°,V=1.5054(8)nm3,Z=4;二轴晶,正延性,负光性,一组完全解理,干涉色为三级绿,多色性明显,浅绿色-黄绿-深绿色;折射率α=1.615,β=1.655,γ=1.700(589 nm),2Vobs=114°~115°,2Vcalc=88.8°;显微硬度平均值203 kg/mm2,相当于莫氏硬度4;实测密度平均3.69 g/cm3,计算密度3.78 g/cm3。X射线粉晶衍射的强谱线有1.5866 nm(7)(002)、0.5340 nm(91)(006)、0.4010 nm(10)(ī14)、0.3209 nm(23)(027)、0.2676 nm(100)(ī110)、0.2294 nm(29)(ī37)和0.2008 nm(11)(228)。汉江石的晶体结构由硅酸盐结构单元TOT(二八面体型)和碳酸盐结构单元Ba2Ca(CO3)2F交替组成,可能有3个多型,即1M型,2M型和3T型。 相似文献
968.
晶体矿物学理论认为不同成岩环境金伯利岩中尖晶石族矿物由于形成物理化学条件不同,其晶体结构和化学成分会发生明显的变化,通过对无矿、贫矿、富矿金伯利岩岩管中的尖晶石族矿物晶胞参数和化学成分的测定,研究尖晶石族矿物化学成分和晶胞参数变化与无矿、贫矿、富矿金伯利岩的内在关系,可以提高金伯利岩型金刚石矿床找矿效率。为了确定辽宁瓦房店金伯利岩中的尖晶石族矿物种属,探讨辽宁瓦房店金伯利岩中尖晶石族矿物化学成分和晶胞参数与金伯利岩含矿性关系,本文运用电子探针波谱仪对50件尖晶石族矿物中的MgO、FeO、TiO2、Al2O3、MnO及Cr2O3进行微区化学成分分析,运用单晶X射线衍射仪对136个尖晶石族矿物晶胞参数进行测定。数据统计显示:瓦房店金伯利岩中尖晶石族矿物为铬铁矿和镁铬铁矿,以化学分子式中A、B组主要阳离子占位特征为基础,可把矿区的尖晶石族矿物划分为10个亚种;如果用尖晶石族矿物化学成分中Cr2O3与(Cr2O3+Al2O3)含量的比值Cr'来表示尖晶石族矿物与金伯利岩含矿性的关系,金伯利岩岩体含矿性由富矿→中等含矿→贫矿,相应岩体中尖晶石族矿物Cr'值分别为89.5%、83.4%~87.1%和70.2%,逐渐变低;从无矿金伯利岩岩体→贫矿和中等含矿金伯利岩岩体→富矿金伯利岩岩体,金伯利岩体中第一世代尖晶石族矿物晶胞参数分别为0.831~0.832 nm、0.834~0.836 nm、0.837 nm,有逐渐变大的趋势。本文认为,辽宁瓦房店金伯利岩中第一世代尖晶石族矿物晶胞参数大小和Cr'参数可以作为判断辽宁瓦房店金伯利岩含矿性的指示标型。 相似文献
969.
以山西大同新生代玄武岩样品为例, 利用Quanta 200扫描电镜、GENESIS能谱仪对能谱仪PPA分析方法进行了实验研究, 该方法为粒度和物相自动分析方法.笔者首次把能谱仪PPA分析方法应用到地质学领域的岩石光薄片研究中, 快速得出了一系列不同物相的形态学数据及化学成分分析结果: 物相种类、每一种物相的颗粒数、每一个颗粒的平均直径、面积、周长、圆度、长宽比及化学成分等, 并得出了不同物相在该视域所占的面积百分比及每种物相颗粒的平均直径, 克服了传统光薄片粒度分析方法的所有缺点, 为矿物学、岩石学及矿床学研究提供了一套非常有意义的数据. 相似文献
970.
台湾花莲碧玉因其浓厚的颜色以及较细腻的结构和特殊光学效应受到广大消费者的喜爱.本文运用常规仪器、电子探针等测试手段研究台湾花莲碧玉宝石矿物学特征.通过科学全面系统的研究与前人资料对比可得,碧玉样品的颜色主要为淡绿-深绿色,颜色较为纯净,分布不均匀.内部可见黑色金属矿物杂质.具油脂-丝绢光泽,微透明-不透明,折射率为1.61,相对密度2.96~3.02 g/cm3,硬度为6~7.碧玉的主要组成矿物为透闪石或者阳起石,次要矿物包括铬铁矿、铬钙铝榴石、透绿泥石.电子探针结果显示,碧玉样品的主要元素成分为MgO、SiO2、CaO,以及少量的FeO和微量的Cr2O3、MnO、K2O、Na2O、Al2O3、TiO2.根据样品数据的对比可以推测,碧玉颜色的深度与FeO的含量呈正比,当碧玉含有铬钙铝榴石包体时,碧玉颜色更鲜艳. 相似文献