The effect of acid deposition on base cation cycling in a karstic-forested catchment： Evidence from strontium isotopes

Bedrock weathering and atmospheric deposition are the two primary sources of base cations （K^＋, Na^＋, Ca^2＋ and Mg^2＋） to forest ecosystems. Therefore, the key problem is to understand the relative inputs from these two sources and the cycling in the ecosystem. This study focuses on the effects of acid deposition on cation cycling in a small-forested karstic catchment in Guizhou Province. Sr isotope ratios were used as a tracer for understanding the transport process between the different cation pools： rock, soil, surface water, atmospheric deposition and plant. The samples of wet deposition, total deposition, throughfall, surface and ground waters, vegetation, and soil were monthly collected. The exchangeable Sr^2＋ and Ca^2＋ in soil samples were extracted by using 1 M ammonium acetate. The leaf-tissue samples were ashed at 550℃, and the residue was digested in ultrapure HClO4 and HNO3. All water samples were filtrated through 0.45 μm aperture filter paper. Base cation concentrations and Sr isotopic composition were analyzed for all the samples. The results show that acid deposition （average pH 4.9） frequently occurred in the studied region. Cation abundance follows an increasing manner from rainwater, throughfall, to surface water or ground water samples, suggesting that acid deposition at first eiuviates Ca^2＋ , Mg^2＋ and Sr^2＋ from leaf, then the exchangeable cations from soil, and at last cations accumulate in surface water or ground water.     

新疆绿色电气石颜色成因研究

新疆绿色电气石颜色成因比较特殊,为了更好地了解其颜色的形成,主要采用化学分析、吸收光谱、穆斯堡尔谱等测试手段对绿色电气石颜色成因进行研究。化学分析结果显示每个样品中均含有少量不同过渡元素离子,如Fe2 、Ti4 、Cr3 等,影响着绿色的形成;利用吸收光谱测试方法确定了致色离子的吸收带位置及主要离子的种类、价态,并根据化学成分计算出相应的化学式,利用穆斯堡尔谱确定了铁离子在晶体中的占位。综合运用上述测试方法,确定了绿色电气石的颜色成因。     

An EFTEM/HRTEM high-resolution study of the near surface of labradorite feldspar altered at acid pH: evidence for interfacial dissolution-reprecipitation

Using an approach combining high-resolution and energy-filtered transmission electron microscopy (HRTEM and EFTEM), we have studied with Å to nm-spatial resolution the interfacial region that delimits the near-surface altered zone and non-altered labradorite feldspar after dissolution under acid pH conditions. The interface is characterized by extremely sharp and spatially coincident changes in structure and chemistry. The 500-nm-thick altered zone is depleted in interstitial cations (Ca, Na, K) and Al, a framework element, whereas it is enriched in H, O, and Si. Modeling H⁺-alkali interdiffusion within a 500-nm-thick altered zone shows that volume interdiffusion cannot reproduce the sharp chemical interfaces measured by EFTEM. Based on these new data, we propose that the near-surface altered zone is a result of interfacial dissolution-reprecipitation, and not of preferential leaching of cations and interdiffusion with H⁺. This implies an intrinsic dissolution process that is stoichiometric, where the breaking of bonds and release of interstitial cations and framework elements (Al, Si, and O) to solution occur contemporaneously at equal relative rates from the original fluid–mineral interface.     

Iron oxidation state in lower mantle mineral assemblages: II. Inclusions in diamonds from Kankan, Guinea

Inclusions of ferropericlase and former (Mg,Fe)(Si,Al)O₃ perovskite in diamonds from Kankan, Guinea believed to originate in the lower mantle were studied using Mössbauer spectroscopy to determine Fe³⁺/ΣFe. Fe³⁺ concentration in the (Mg,Fe)(Si,Al)O₃ inclusion is consistent with empirical relations relating Fe³⁺/ΣFe to Al concentration, supporting the inference that it crystallised in the perovskite structure at lower mantle conditions. In ferropericlase there is a nearly linear variation of trivalent cation abundance with monovalent cation abundance, suggesting a substitution of the form Na_0.5M_0.5³⁺O (M=Fe³⁺, Cr³⁺, Al³⁺). Excess positive charge is likely balanced by cation vacancies, where their abundance is observed to increase with increasing iron concentration, consistent with high-pressure experiments. The abundance of cation vacancies is related to oxygen fugacity, where ferropericlase inclusions from Kankan and São Luiz (Brazil) are inferred to have formed at conditions more oxidising than Fe-(Mg,Fe)O equilibrium, but more reducing than Re-ReO₂ equilibrium. Fe²⁺/Mg partition coefficients between (Mg,Fe)(Si,Al)O₃ and ferropericlase were calculated for inclusions co-existing in the same diamond using Mössbauer data and empirical relations based on high-pressure experimental work. Most values are consistent with high-pressure experiments, suggesting that these inclusions equilibrated at lower mantle conditions. The measured ferropericlase Fe³⁺ concentrations are consistent with diamond formation in a region of redox gradients, possibly arising from the subduction of oxidised material into reduced lower mantle. Reduction of carbonate to form ferropericlase and diamond is consistent with a slight shift of Kankan δ¹³C values to isotopically heavy compositions compared to the worldwide dataset, and could supply the oxygen necessary to satisfy the high Fe³⁺ concentration in (Mg,Fe)(Si,Al)O₃ perovskite, as well as account for the high proportion of ferropericlase in the lower mantle paragenesis. The heterogeneity of lower mantle diamond sources indicates that the composition of lower mantle diamonds do not necessarily reflect those of the bulk mantle.     

海洋沉积物孔隙水中阴阳离子含量的离子色谱法分析方法

分别采用Metrosep A Supp4-250型阴离子柱和Metrosep C 2-150型阳离子柱,以1.8 mmol/L Na2CO3 1.7 mmol/L NaHCO3和4 mmol/L酒石酸 0.75 mmol/L吡啶二羧酸为阴阳离子淋洗液,用离子色谱仪来测定海洋沉积物孔隙水中阴离子Cl-、Br-和SO42-浓度和阳离子Na 、NH4 、K 、Ca2 、Mg2 的浓度。特别是针对高Cl-和高Na 背景下Br-和NH4 的测定做了专门分析,得到了较理想的结果,建立了一套离子色谱法测定海洋沉积物孔隙水中常见的阴阳离子含量的实验方法。     

盱眙、明光、临泽坡缕石的八面体阳离子占位及对其性能的影响

坡缕石是一种21型链层状结构含水富镁铝硅酸盐矿物,具有重要的资源和材料属性。不同成因、产状坡缕石八面体中类质同象替代有很大差别,而八面体类质同象替代对坡缕石性能的影响未见研究报道。本文以中国最具代表性的安徽明光、江苏盱眙、甘肃临泽坡缕石为研究对象,研究了三种坡缕石的Al、Mg、Fe含量及在八面体中的占位,并探讨了八面体的Al、Mg、Fe占位对坡缕石中水的种类和含量、表面电位和酸位以及对Pb2+、Cd2+吸附性能的影响。结果表明：明光坡缕石相对富镁,八面体主要被Mg2+占据,具有三八面体特征;盱眙、临泽坡缕石相对富铝、铁,八面体主要被Al3+占据,表现出更多的二八面体特征。盱眙坡缕石由于M1位置空位较多,结构水含量较低;坡缕石类质同象替代对Zeta电位影响不大;具有二八面体特征的盱眙、临泽坡缕石由于八面体中Al含量较高,酸位较多,催化性能较好。在重金属吸附实验中,明光坡缕石对Cd2+的吸附效果最好,盱眙坡缕石对Pb2+的吸附效果最好,临泽坡缕石吸附性能较差。本文可为坡缕石的改性和应用提供指导和参考。     

低速十字路口交通流模型相图

研究由两个单车道构成低速十字路口交通流模型.模型中两车道上的车辆更新遵循无交通灯管制下的并行规则.依据构建相图的原则并采用局部占有概率方法,建立相图,给出相图中的各部分区域的流量表达式.两车道均采用周期边界条件和确定性FI模型进行数值模拟,模拟结果与理论分析精确一致.模型中两条车道的行车规则更接近实际道路交通,该结果为交通管理提供一定的指导作用.     

郑家-王庄地区沙一段粘土矿物特征及对储层敏感性影响

东营凹陷郑家—王庄地区沙一段砂岩储集层中蕴藏大量稠油油藏,但开发过程中粘土矿物的敏感性严重制约了该油类藏的有效开发。定向X射线衍射分析结果表明,本区沙一段砂岩储层中粘土矿物组成类型为伊/蒙无序间层矿物(S/I)、高岭石、伊利石和绿泥石,其中以伊/蒙无序间层矿物的相对含量居多。这就决定了研究区储层敏感性以水敏性为主,其余敏感性无或较弱。据定向X射线衍射谱图上S/I主峰d值大小,进一步识别出钙型S/I、钠型S/I及钙钠过渡型S/I。扫描电镜观察表明,S/I具有丝状、网状和蜂窝状三种形态,且大都包裹在岩石骨架颗粒的表面作为孔隙衬里而存在。阳离子交换容量和膨胀率研究结果显示,二者与样品中S/I含量和层间阳离子类型相关。膨胀率和阳离子交换量与S/I含量都呈较好的正相关关系。在S/I中蒙皂石层含量相当的情况下,钠型S/I的膨胀率和阳离子交换量值偏大,钙型偏小,钙钠过渡型居中。此外,粘土总量以及S/I产状对储层损害也有较大的影响。     

几个天然矿物中某些阳离子近邻结构的EXAFS研究

本文利用EXAFS方法对镁铝榴石、几种锰矿和不同铁含量的闪锌矿中有关阳离子的近邻结构进行了研究,得到了有关阳离子在相应矿物中的近邻结构参数.对闪锌矿的研究,得到了杂质Fe绝大部分以六配位的形式存在的结果,这与传统的观点不同;提出了闪锌矿不仅可作为地质温度计,还可能作为地质温度、压力变化记录仪的设想。     

溶胶－凝胶方法制取纳米级超导物质的研究

当前对超导物质的研究都集中于高临界温度的超薄型物质的研究上，本研究通过相对简单的方法获得高纯度的纳米级的钙钛矿型超导物质，其过程为：通过溶胶－凝胶方法合成一种含有Ｌａ和Ｎｉ的高纯度的有机物，然后利用天然蒙脱石的离子交换性将上述化合物渗入到其含水层中以获得超薄型的超导物质