土工膜应变计的研制及其应用(II):应用

将研制的土工膜应变计应用于三峡工程二期上游围堰现场,以监测防渗土工膜在工程中产生的实际应变,并获得了满意的大应变监测成果。埋设于上游围堰不同高程的18支土工膜应变计,在较长时段内,不仅全部观测到防渗土工膜在施工阶段围堰填土碾压产生的应变规律,如0 500断面的10支土工膜应变计均测得11%～19%的大应变值,而且大部份应变计一直工作到极限量程才损坏。其中除了0 500断面因施工加载速率过快而导致防渗土工膜较早产生较大的变形,使得10支应变计在埋设后的施工填土3个多月内即陆续超量程损坏之外,其余的土工膜应变计工作寿命长达3年多。埋设于0 500子堰和0 930断面的土工膜应变计,在2000年和2001年夏季汛期中及汛期后,有些监测点的应变陡增到16%～20%之间,据此可以推测,此时该测点处的堰体产生了较大的变形。防渗土工膜的应变监测结果不仅与围堰构筑时的加载速率相关,并与围堰拆除时所发现的变形情况相吻合。     

Fe(II)-Na(I)-Ca(II) Cation Exchange on Montmorillonite in Chloride Medium: Evidence for Preferential Clay Adsorption of Chloride – Metal Ion Pairs in Seawater

Fe(II)–Ca(II), Fe(II)–Na(I), and Fe(II)–Ca(II)–Na(I) exchange experiments on montmorillonite were performed in chloride background. These experiments show the possible sorption of Fe²⁺ and FeCl⁺ ion pairs in exchange site positions, a result confirmed with 77 K ⁵⁷Fe Mössbauer experiments. The sorption data were modeled and the cation exchange selectivity for Fe(II) were found to be nearly equal to that of Ca(II). Vanselow selectivity coefficients, for Na–Fe²⁺ and Na–FeCl⁺ reactions, were found to be equal to 0.4 (0.5 for Ca²⁺) and 2.3 (2.5 for CaCl⁺) respectively. High affinity of montmorillonite for chloride ion pairs seems to be a common mechanism as first stated by Sposito et al., (Soil Sci. Soc. Am. J. 47, 51–56, 1983a), and should have implications e.g., on the chemistry of suspended particles in seawater. Exchange selectivity coefficients derived from this study and others were used to model experimental data on river water and seawater equilibrated particles. The agreement between simulations and experimental data is very good. The simulation shows the predominance of monovalent ion (Na⁺ and chloride ion pairs) sorption on clay particles in seawater. This sorption of monovalent ions leads to the dispersion of particles in seawater and to the extension of a plume of particles spreading away from river deltas, such as that of the River Amazon.     

岩石细观统计渗流模型研究(II):实例分析

进一步分析了第I部分中提出的岩石细观统计渗流模型[1]。讨论了由细观统计渗流模型得到岩石宏观渗透系数的方法。为了利用细观统计渗流模型对岩石损伤破坏过程中的渗透性演化进行分析,引入了各向异性损伤模型,用以对岩石的细观损伤和裂纹的扩展过程进行力学分析,并讨论了细观统计渗流模型与各向异性损伤模型的联合分析方法。对Lac du Bonnet花岗岩损伤过程中的渗透性演化进行了计算分析和验证。结果表明,细观统计渗流模型可以较精确地描述裂纹充分贯通前岩石渗透性的演化。     

How to overcome inter-electrode variability and instability to quantify dissolved oxygen, Fe(II), mn(II), and S(?II) in undisturbed soils and sediments using voltammetry

Background

Although uniquely capable of measuring multiple redox constituents nearly simultaneously with no or minimal sample pretreatment, voltammetry is currently underutilized in characterizing redox conditions in aquatic and terrestrial systems. Investigation of undisturbed media such as pore water requires a solid-state electrode, and such electrodes can be difficult to fabricate reproducibly. An approach to determine the concentrations of electroactive constituents using indirectly calibrated electrodes has been developed, but the protocol for and accuracy of this approach??the pilot ion method??has not been documented in detail.

Results

A detailed procedure for testing electrode quality is provided, and the application and limitations of the pilot ion method have been documented. To quantify Fe(II) and Mn(II), subtraction of non-linear baseline functions from voltammetric signals produced better calibration curves than did linear baselines, enabled lower detection limits and reliable deconvolution of overlapping signals, and was successfully applied to sediment pore water signals. We observed that electrode sensitivities often vary by tens of percent, and that the sensitivity declines over time. The ratio of calibration slopes of Mn(II) to Fe(II) varied by no more than 11% from one Hg/Au electrode to another and Fe(II) concentrations predicted by the Mn(II) pilot ion were, on average, 13% different from their actual values. However, concentration predictions by the pilot ion method were worse for less than 15???M Fe(II) (46% different on average). The ratio of calibration slopes of Mn(II) to S(?II) varied by almost 20% from one Hg/Au electrode to another, and S(?II) predicted concentrations were as much as 58% different from their actual values. These predictions of Fe(II) and S(?II) concentrations indicate that the accuracy of the pilot ion method depends on how independent calibration slope ratios are from the electrode used. At medium-to-high concentration for the ocean, naturally derived dissolved organic carbon did not significantly affect the baseline-corrected electrode response of Mn(II) and Fe(II), but did significantly affect the response of S(?II).

Conclusions

Despite their intrinsic variability, Hg/Au electrodes fabricated by hand can be used to quantify O₂, S(?II), Fe(II), and Mn(II) without calibrating every electrode for every constituent of interest. The pilot ion method can achieve accuracies to within 20% or less, provided that the underlying principle??the independence of slope ratios??is demonstrated for all voltammetric techniques used, and effects of the physicochemical properties of the system on voltammetric signals are addressed through baseline subtraction.     

新疆冰川、积雪对气候变化的响应(II):灾害效应

新疆地区冰川、积雪广泛分布,在其融水补给河川径流的同时,也常伴有冰川洪水、融雪洪水、冰湖突发洪水、冰川泥石流、冰雪崩和风吹雪等冰雪灾害发生,这些灾害对当地居民居住地以及重要国防干线的安全运营形成较大威胁.冰川、积雪变化直接影响到冰雪灾害发生的程度与影响范围,新疆的冰川洪水和冰湖突发洪水灾害主要发生在塔里木河流域的喀喇昆仑山、昆仑山以及天山南坡西部一带,融雪洪水灾害主要发生在新疆北部的阿勒泰地区、塔城地区和天山北坡一带,冰川泥石流、冰雪崩灾害主要发生在帕米尔高原、天山西段和西昆仑山地区,风吹雪主要在天山中、西段地区.随着全球气候变暖,尤其是新疆从1987年开始的气候由暖干向暖湿的转型,冰川退缩加剧,融水量增大,冰川洪水和冰川泥石流灾害随着冰川融水径流的增加而增多;而融雪洪水、雪崩和风吹雪随着气候变化引起的冬季积雪增加和气温升高,其灾害强度在增强;冰崩灾害随着气温升高引起的高山冰体崩解而呈增加趋势.在新疆地区,冰雪灾害主要表现为冰雪洪水,已观测到近十几年来在气候变化影响下冰雪洪水发生的频次和强度有增加的趋势,塔里木河流域的冰湖溃决洪水和冰川洪水及北疆春季的冰凌和融雪洪水已对当地的生命财产和社会经济发展带来巨大危害,新疆的水资源安全、灾害等问题日益凸显.预计未来,随着气候增温引起的冰雪融水径流的增加,相关的冰雪灾害增多,因而增加了冰雪灾害的危险程度,并可能形成若干新的灾害点.面对气候变化诱发的众多冰川、积雪灾害,目前还缺乏对灾害监测、预测预警方面的适应对策.因此,在全球气候变化不断加速的趋势下,冰雪灾害应引起有关方面的足够重视,加强气候变化对冰雪灾害的影响评估和适应性管理对策研究,使科学技术在减灾方面发挥主导作用.     

大型现场室内两用直剪仪研制(II):试验测试

利用新近研制的大型现场室内两用直剪仪,对两种不同性质的砂样进行了剪切试验。在对干砂的直接剪切试验特性进行综述的基础上,从多方面对该大型直剪仪得出的干砂剪切试验数据进行了分析验证,结果表明该大型直剪仪得出的试验数据一致性好、可靠性较高,说明该大型直剪仪的基本剪切性能稳定,可进一步应用于相关岩土材料的试验研究。     

Influence of microbial hydroxamate siderophores on Pb(II) desorption from α-FeOOH

Siderophores are low-molecular weight organic molecules secreted by plants and micro-organisms in response to Fe stress. With stability constants commonly exceeding 10³⁰, siderophores are considered to have higher affinities for Fe(III) than for any other major or trace element dissolved in soil solution. However, several siderophores have affinities for trace metals that approach those for Fe(III), and certain actinides form siderophore complexes of surprisingly high stability. The purpose of this study was to examine the role of hydroxamate siderophores in controlling Pb sorption to an Fe(III) oxide adsorbent. Goethite [α-FeOOH], prepared by standard methods and identified by X-ray diffraction, gave a specific surface of 36 m² g⁻¹ as determined by N₂ multipoint BET analysis. Adsorption experiments were performed aseptically using a batch method with a goethite concentration of 1.0 g l⁻¹ and an ionic strength of 0.01 M NaClO₄. Soluble Pb and Fe were measured between pH 3 and 8 by first adding Pb (10 μM) and then siderophore (10, 20, or 40 μM) to the goethite suspension. Three hydroxamate siderophores were employed: desferrioxamine B (DFB), ferrichrome (FC), and rhodotorulic acid (RA). Following 20 h reaction, Pb and Fe in solution were measured by ICP–MS and ICP–AES, respectively. The efficacy of siderophore-mediated Pb desorption varied with siderophore type and generally increased with pH and siderophore/Pb molar ratio. Desferrioxamine B, at pH 6.5 and a DFB/Pb molar ratio of 4, solubilised nearly 25% of the total sorbed Pb. In the presence of 10 μM FC, Pb adsorption largely mimicked that for the siderophore-free system, whereas significant amounts of Pb were desorbed with 20 μM FC at pH >5.5. The dihydroxamate siderophore, RA, was the least effective Pb chelator, requiring 20 μM to desorb detectable amounts of Pb.     

绿片岩三轴流变力学特性的研究(II):模型分析

首先,基于在岩石全自动流变伺服仪上得到的绿片岩三轴流变试验曲线,采用五元件线性粘弹性模型对表现为粘弹性流变特性的曲线进行了辨识,获得了绿片岩的粘弹性流变参数;然后,提出了一个新的非线性粘性元件,并将其与塑性体并联起来,得到一个新的非线性粘塑性体(NVPB),该体能充分反映岩石的加速流变特性:同时,将NVPB模型与五元件粘弹性模型串联起来,建立了一个新的岩石七元件非线性粘弹塑性流变模型。采用绿片岩加速流变全过程曲线,对提出的岩石七元件非线性粘弹塑性流变模型进行了辨识,得到了岩石七元件非线性粘弹塑性流变模型的材料参数。流变模型与试验结果的比较,显示了所建模型的正确性与合理性。     

Fe(II) reduction of pyrolusite (β-MnO<Subscript>2</Subscript>) and secondary mineral evolution

Iron (Fe) and manganese (Mn) are the two most common redox-active elements in the Earth’s crust and are well known to influence mineral formation and dissolution, trace metal sequestration, and contaminant transformations in soils and sediments. Here, we characterized the reaction of aqueous Fe(II) with pyrolusite (β-MnO₂) using electron microscopy, X-ray diffraction, aqueous Fe and Mn analyses, and ⁵⁷Fe Mössbauer spectroscopy. We reacted pyrolusite solids repeatedly with 3 mM Fe(II) at pH 7.5 to evaluate whether electron transfer occurs and to track the evolving reactivity of the Mn/Fe solids. We used Fe isotopes (56 and 57) in conjunction with ⁵⁷Fe Mössbauer spectroscopy to isolate oxidation of Fe(II) by Fe(III) precipitates or pyrolusite. Using these complementary techniques, we determined that Fe(II) is initially oxidized by pyrolusite and that lepidocrocite is the dominant Fe oxidation product. Additional Fe(II) exposures result in an increasing proportion of magnetite on the pyrolusite surface. Over a series of nine 3 mM Fe(II) additions, Fe(II) continued to be oxidized by the Mn/Fe particles suggesting that Mn/Fe phases are not fully passivated and remain redox active even after extensive surface coverage by Fe(III) oxides. Interestingly, the initial Fe(III) oxide precipitates became further reduced as Fe(II) was added and additional Mn was released into solution suggesting that both the Fe oxide coating and underlying Mn phase continue to participate in redox reactions when freshly exposed to Fe(II). Our findings indicate that Fe and Mn chemistry is influenced by sustained reactions of Fe(II) with Mn/Fe oxides.

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地下圆形衬砌隧道对沿线地震动的影响(II):数值结果

利用地下圆形衬砌隧道对入射平面P波和SV波散射级数解答，定量分析了入射波长、入射角度、隧道直径、衬砌刚度等因素对沿线地表位移放大作用的影响。计算结果表明，当入射频率较低时，地下隧道的存在对地表位移幅值影响不大；而当入射频率较高时，地表位移幅值可以达到无隧道情况的4．5倍以上；衬砌情况下地表位移幅值可以高出非衬砌情况的87．8％。建议在地铁的规划设计中考虑地下隧道的建设对隧道沿线设计地震动的影响。     

Pottery glaze—An excellent adsorbent for the removal of Cu(II) from aqueous solution

In the present study,pottery glaze was investigated as an excellent adsorbent for the removal of Cu(Ⅱ) ions from aqueous solution.Effect of concentration,contact time,pH,and effect of electrolyte concentration,adsorbent doses and temperature were studied by using batch process to optimize conditions for maximum adsorption. Equilibrium isotherm data were analyzed using Langmuir,Freundlich and Temkin isotherms at 30,40 and 50℃. Thermodynamic parameters such as standard enthalpy change(ΔH0),free energy change(ΔG 0)and entropy change (ΔS0)were also evaluated.These parameters indicated that adsorption process is endothermic and spontaneous in nature.The mean energy calculated from Dubinin-Radushkeuich(D-R)isotherms showed chemical nature of adsorption.The kinetic data were evaluated using the pseudo-first-order and pseudo-second order kinetic equations and it was found that data best fitted pseudo-second-order model over a wide range of initial Cu(Ⅱ)concentrations supporting that chemisorption process was involved.The adsorption and desorption studies carried out by batch process suggested 100% desorption of Cu(Ⅱ)ions with 0.1 N HCl solution.     

静止环境中有阻力圆盘浮力射流特性的研究——(II)流场特性分析

在数值计算成果的基础上,对阻力圆盘浮力射流的流场进行了分析和总结,基于轴线流速的变化规律将盘后流场分为3个区域:回流区、过渡区和自相似区。得到了回流区的长度随弗劳德数F0、孔口直径D/d以及盘离孔口的距离H/d的变化规律,并得到了工况为H/D=1,D/d=2,6和H/D=3,D/d=2在不同弗劳德数F0条件下的横截面上的流速分布和达到自相似区的最小长度;结果表明弗劳德数F0的大小是决定绕流流态的主要因素;同时分析了由正常绕流发展到非正常绕流的压力场变化,发现由于弗劳德数F0的增大而导致流场中出现的第三个负压中心的大小和位置与绕流是否能正常发生存在密切的关系。     

Pyrolusite surface transformations measured in real-time during the reactive transport of Co(II)EDTA2−

Oxidation of Co(II)EDTA²⁻ to Co(III)EDTA⁻ by manganese and iron hydrous oxide minerals enhances the transport of ⁶⁰Co in subsurface environments. Until now, reduction of the oxidant MnO₂ has not been identified in hydrodynamic systems, leaving the fate and transport mechanisms involving ⁶⁰Co in natural environments unresolved. We investigated the transport of Co(II)EDTA²⁻ through packed beds of β-MnO₂ and identified the reaction mechanism using a novel hydrodynamic flow cell coupled with X-ray absorption near edge structure (XANES) spectroscopy. Using this technique we are able to determine both solution and solid-phase species of cobalt and manganese in real-time. Co(II)EDTA²⁻ is produced while Mn(IV) is reduced to Mn(III) which forms an α-Mn₂O₃layer on pyrolusite. This layer passivates the surface after an initial reaction period and ultimately limits the production of Co(III)EDTA⁻. As a consequence, the enhanced transport of ⁶⁰Co by oxidative processes may be diminished by continual exposure to pyrolusite—an advantage from an environmental quality perspective. It has also been clarified that Mn(III) is formed rather than Mn(II) resulting in formation of a stable trivalent manganese solid (α-Mn₂O₃).     

(八) 河床演变(一)

沿长江顺流而下,可以看到千山万谷,汹涌澎湃的三峡,也可以看到九曲回肠的荆江和潮平岸阔的江苏江段。在宜昌南津关,“山随平野尽,江入大荒流”(李白《渡荆门送别诗》)。长江就在这里由山区进入平原。一般说来,天然河流都可象长江一样,分为山区和平原两段。山区河流是水流改造山谷的产物。地壳运动,增加了河床演变的复杂性。山区河流具有下列特点:(1)河床纵比降大;(2)水流湍急紊乱;(3)山谷沿程宽窄不一,河道在平面上具有藕节状外形;     

(2)PALEOBOTANY (3)PALEOZOOLOGY

971349 Che;19 Jie(China Universityseienees,Beijing)The MammaljanShowjng ClimatieF盆uetuat应on—ExamPle of the Early Pleistoceneof Ge。FaunaS AS anMam-malian Faunas from Zhoukoudian,Beijing,China(ESI矛,ISSN 1 005一2321,CN 11一3370/P,4(2),1997,p·275一279,1 graph,1 table,10 ref) By analyses of the four local marnmalianfaunas from Zhoukoudian,Beijing,the EarlyPleistoeene elimatie and eeologieal environ-CN 11一1 905/Q1 53,1 graph,1735(2).1997,P.145一mental ehangespaper.One of1 .90M…     

铁(II)-5-Br-PADAP-乳化剂OP体系析相光度法测定微量铁的应用研究

研究了铁 (Ⅱ ) 5 Br PADAP 乳化剂OP体系中的析相、显色反应的条件及其吸收光谱的分析特征 ,拟定了直接测定不同种类样品中痕量铁的分析方法。在pH =5 .0的HAC NaAC缓冲溶液中 ,Fe(Ⅱ ) 5 Br PADAP络合物具有两个吸收峰 ,分别位于λ1 =5 6 1nm与λ2 =75 4nm处。本文选择λ =75 4nm进行测定 ,其摩尔吸光系数为 :ε75 4 =3.9× 10 4L·mol- 1 ·cm- 1 。铁含量在 0～ 2 4μg范围内服从比尔定律。此方法用于样品中痕量铁的测定 ,结果准确     

(九)河床演变(二)

自然河流或者处于单向演变状态,或者处于准平衡状态。这是按平均概念而言。实际河床演变就是围绕这种均衡状态或正或负地交替进行。河流一旦受到外力干扰,均衡状态被破坏之后,河床演变过程也将随之改变。有的干扰、改变甚至破坏会很强烈。这种演变开始时都比较急剧,然后逐渐衰减,最终达到新的均衡状态。干扰河床演变均衡状态的途径有二:(1)改变河道的来水来沙条件。如河段以上的水土保持工程、拦沙工程、水库枢纽工程、分流堵汊工程和引水工程等的作用。它们增减水量、沙量,改变水流过程和输沙过程以及水沙搭配关系等。(2)改变河段河床形     

Structure and stability of the Fe(II)–Fe(III) green rust “fougerite” mineral and its potential for reducing pollutants in soil solutions

Fe(II)–Fe(III) layered double hydroxysalt green rusts, GRs, are very reactive compounds with the general formula, [Fe^II_(1−x) Fe^III_x (OH)₂]^x+·[(x/n) Aⁿ⁻·(m/n) H₂O]^x−, where x is the ratio Fe^III/Fe_tot, and reflects the structure in which brucite-like layers alternate with interlayers of anions Aⁿ⁻ and water molecules. Two types of crystal structure for GRs, GR1 and GR2, represented by the hydroxychloride GR1(Cl⁻) and the hydroxysulphate GR2(SO₄²⁻) are distinguished by X-ray diffraction due to different stacking. By analogy with GR1(Cl⁻) the structure of the fougerite GR mineral, [Fe^II_(1−x) Fe^III_x (OH)₂]^x+·[x OH⁻·(1−x) H₂O]^x-  Fe(OH)_(2+x)·(1−x) H₂O, is proposed displaying interlayers made of OH⁻ ions and water molecules (in situ deprotonation of water molecules is necessary for explaining the flexibility of its composition). The space group of mineral GR1(OH⁻) would be R3̄m, with lattice parameters a≅0.32 and c≅2.25 nm. Stability conditions and the E_h-pH diagram of Fe(OH)_(2+x) (the water molecules are omitted) are determined from hydromorphic soil solution equilibria with GR mineral in Brittany (France). Computed Gibbs free energies of formation from soil solution/mineral equilibrium fit well with a regular solid solution model: μ°[Fe(OH)_(2+x)]=(1−x) μ°[Fe(OH)₂]+x μ°[Fe(OH)₃]+RT [(1−x) ln (1−x)+x ln x]+A₀ x (1−x), where μ°[Fe(OH)₂]=−492.5 kJ mol⁻¹, μ°[Fe(OH)₃]=−641 kJ mol⁻¹ and A₀=−243.9 kJ mol⁻¹ at the average temperature of 9±1°C. The upper limit of occurrence of GR mineral at x=2/3, i.e. Fe₃(OH)₈, is explained by its unstability vs. α-FeOOH and/or magnetite; Fe(OH)₃ is thus a hypothetical compound with a GR structure which cannot be observed. These thermodynamic data and E_h-pH diagrams of Fe(OH)_(2+x) can be used most importantly to predict the possibility that GR minerals reduce some anions in contaminated soils. The cases of NO₃⁻, Se(VI) or Cr(VI) are fully illustrated.     

Clay-salt slimes of the JSC “Belaruskali” as potential engineering barriers in the radioactive waste repositories: sorption of Cs(I), Sr(II), Eu(III) and Am(III)

Results of sorption of caesium(I), strontium(II), europium(III) and americium(III) ions on the aluminosilicates separated from the clay-salt slimes (CSS) depending on the contact time, pH, initial metal concentration are presented. CSS 1A and CSS 1B sorbents appear to be sufficiently chemically and radiation stable for practical application in treatment of the radioactive wastewaters.