Groundwater mineralisation processes in Mediterranean semi‐arid systems (Cap‐Bon,North east of Tunisia): hydrogeological and geochemical approaches

The groundwater of the Korba plain represents major water resources in Tunisia. The Plio‐Quaternary unconfined aquifer of the Cap‐Bon (north‐east Tunisia) is subject to the intensive agricultural activities and high groundwater pumping rates due to the increasing of the groundwater extraction. The degradation of the groundwater quality is characterized by the salinization phenomena. Groundwater were sampled and analysed for physic‐chemical parameters: Ca²⁺, Mg²⁺, Na⁺, K⁺, Cl^‐, SO₄^2‐, HCO₃^‐, NO₃^‐, pH, electrical conductivity (EC), and the temperature (T°). The hydrochemical analysis is coupled with the calculation of the saturation indexes (SI gypsum, SI halite, SI calcite and SI dolomite), ionic derivation and with the ion correlations compared to chloride concentrations: Na⁺/ Cl^‐, Ca²⁺/ Cl^‐ and Mg²⁺/ Cl^‐ ratios. Seawater fractions in the groundwater were calculated using the chloride concentration. Those processes can be used as indicators of seawater intrusion progression. EC methods were also conducted to obtain new informations on the spatial scales and dynamics of the fresh water–seawater interface of coastal groundwater exchange. The mixing zone between freshwater and saltwater was clearly observed from the EC profile in the investigated area where a strong increase in EC with depth was observed, corresponding to the freshwater and saltwater interface. Results of hydrochemical study revealed the presence of direct cation exchange linked to seawater intrusion and dissolution processes associated with cations exchange. These results, together with EC investigation, indicated that the groundwater is affected by seawater intrusion and is still major actor as a source of salinization of the groundwater in Korba coastal plain. Further isotopic and hydrological investigations will be necessary to identify and more understood the underlying mechanisms. Copyright © 2012 John Wiley & Sons, Ltd.     

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.     

离子液体合成及其在萃取分离中的应用进展

作为环境友好型功能材料—离子液体以其独特的物理化学性质已引起人们的广泛关注。简要介绍了离子液体的组成、结构和性能,概述了离子液体的合成方法,详细介绍了离子液体在萃取分离有机物、金属离子、稀土、放射性元素及燃气脱硫等领域的应用进展。最后探讨了当前存在的问题及研究方向,展望了其应用前景。     

Iron oxidation state in lower mantle mineral assemblages: I. Empirical relations derived from high-pressure experiments

The oxidation state of iron can significantly influence the physical and chemical properties of lower mantle minerals. To improve methods for estimation of Fe³⁺/∑Fe, synthetic assemblages of (Mg,Fe)(Si,Al)O₃ perovskite and (Mg,Fe)O ferropericlase were synthesised from oxide starting mixtures in Re or Fe capsules at 26 GPa and 1650-1850 °C using a multianvil press. (Mg,Fe)(Si,Al)O₃ majorite was also present in some of the run products. Both electron energy loss spectra (EELS) and Mössbauer spectra were measured for each run product, and a robust fitting method was developed for Mössbauer spectra using EELS results as a standard that enabled Fe³⁺/∑Fe of (Mg,Fe)(Si,Al)O₃ perovskite to be determined from Mössbauer spectra of multiphase assemblages. There is a close to linear variation between Fe³⁺/∑Fe and Al concentration in (Mg,Fe)(Si,Al)O₃ perovskite, independent of oxygen fugacity. The concentration of Fe³⁺ in (Mg,Fe)O increases with increasing iron concentration along curves of constant oxygen fugacity, where higher oxygen fugacity stabilises greater Fe³⁺ concentrations. Fe²⁺/Mg partition coefficients calculated from chemical composition data corrected for measured Fe³⁺/∑Fe showed values nearly identical within experimental error for all samples, and independent of Al concentration and oxygen fugacity. Simple empirical relations were derived to calculate Fe³⁺/∑Fe in (Mg,Fe)(Si,Al)O₃ perovskite and (Mg,Fe)O ferropericlase samples for which no Mössbauer or EELS data were available, and tested by applying them to calculation of Fe²⁺/Mg partition coefficients from literature data for (Mg,Fe)(Si,Al)O₃ perovskite-(Mg,Fe)O assemblages where only total iron concentrations had been measured. Results showed Fe²⁺/Mg partition coefficients that were equal to existing values within experimental error, hence confirming the validity of the empirical relations.     

广东省丰良地热田高氟地热流体成因及热储温度评价

广东丰顺丰良地区出露的地热水温度高达96℃,热储层为裂隙发育的下侏罗统的英安斑岩,F^-含量较高。但关于其地热流体的补给来源、循环演化过程及热储温度研究较少。笔者等基于早期开展的勘探工作和补充采集、测试的地热水和气体数据,探讨了该地热系统的流体成因及热储温度。结果表明,丰良地区地热水存在2类,A类地热水温度普遍低于40℃,Ca²⁺含量高,Na⁺和K⁺含量低,以HCO^-₃—Ca²⁺型为主;B类地热水Na⁺含量高,Ca²⁺含量低,为HCO^-₃—Na⁺型。A类地下水可能受浅层地下水混入影响,但缺少直接证据。B类地下水由周边山区的大气降水补给,沿裂隙或者断裂系统进入英安斑岩储层,循环深度和水—岩相互作用时间分别可达5200～6300 m和22 ka;储层温度条件下铝硅酸盐矿物的溶解以及阳离子交换作用促进了富N₂、S...     

碱熔-阳离子交换树脂分离ICP-MS法测定厚覆盖区地球化学调查样品中硼锗溴钼锡碘钨

多目标地球化学填图是多目标区域地球化学调查中重要的区域性基础性工作之一,为了更好地反映出地球化学背景变化,要求分析方法具有更高的准确度、精密度以及更低的检出限。地球化学调查样品中的硼锗溴钼锡碘钨主要采用单独或分组熔矿的方法进行制备和测定,操作流程长且涉及6种测定方法。本文基于前人研究,对以上7种元素的分析方法进行系统总结,采用过氧化钠-氢氧化钠碱熔,分取溶液加入柠檬酸,利用阳离子交换树脂,静态交换2~3h,除去溶液中大量的阳离子减少基体干扰,利用电感耦合等离子体质谱法（ICP-MS）测定硼锗溴钼锡碘钨含量。结果表明：7种元素的检出限分别为0.66、0.096、0.78、0.11、0.15、0.29、0.27μg/g,相对标准偏差（RSD,n=11）在2.1%~7.5%之间,均小于10%。该方法操作简便、快速,应用成本低,并且整合了相关6种分析配套方法,应用于测定厚覆盖区地球化学调查样品,精密度和准确度均满足《多目标区域地球化学调查规范（1：250000）》（DZ/T 0258-2014）要求。     

两广大陆地区酸雨的时空分布规律和化学特点

自１９８８年１月至１９８９年１２月，建立了一个包括７０个监测点的酸沉降测网，进行了常规的干，湿沉降同步观测，获得了大量的监测数据，结果表明：两广地区大面积出现酸雨，酸雨污染较严重地区是广东省粤北和珠江三角洲及广西的“汀桂走廊”。这些地区经济发展迅速，又是ＳＯ２，ＮＯｘ排放量较多的地区。降水酸度季节分布明显，即：春季＞冬季＞秋季＞夏季。降水中主要离子是Ｃａ＾２＋，ＮＨ＾＋４和ＳＯ＾２－４，化学组成以     

膨润土吸附重金属离子的影响因素初探——以Zn~(2 )为例

对影响膨润土吸附重金属离子Zn2 的因素进行的初步研究表明 :在一定条件下 ,提高吸附温度 ,提高溶液的 pH值 ,增加溶液中Zn2 初始浓度 ,增加吸附作用时间 ,提高搅拌速度和减小膨润土的粒度都能不同程度地提高吸附量。同时讨论了吸附机理。     

新形势下的会计职业判断

会计的过程就是会计判断的过程,会计职业判断贯穿于会计的确认、计量、记录和报告的全过程。随着我国加入WTO和市场经济的全球化,新颁布的企业会计准则为会计带来了更大的机遇与挑战,要求会计人员必须运用职业判断对经济事项作出恰当处理,以提供更可靠、更相关、更有价值的会计信息。文章探讨了会计职业判断的现状、影响因素,并对新形势下改善会计职业判断质量的途径提出了建议。     

Lake‐level changes in central Patagonia (Argentina): crossing environmental thresholds for Lateglacial and Holocene human occupation

The role and extent of climate as a cause of the expansion and decline of human cultures is still debatable. It is clear, however, that human–environment interactions are enhanced and interplay more closely in climatically sensitive areas such as around hydrologically closed basins. Lago Cardiel is located at 49° S in the very arid rain shadow east of the Andes, providing an exceptionally receptive system to changes in hydrological balance. Results of a geophysical survey combined with sedimentological and geochemical studies provide a continuous Lateglacial–Holocene record of substantial water‐level changes. These variations, combined with archaeological results from the catchment area, offer a unique possibility to explore the pattern of peopling within this remote area of the globe and its possible relation to climate change. Human occupation in Patagonia is well documented towards the Andes throughout the entire Holocene. Archaeological data from the Lago Cardiel basin, however, show an apparent lack of human activity during the first part of this period, which coincides with well‐constrained high lake levels. Our results show an intriguing coincidence between low lake level and increasing human occupation, suggesting that the Lago Cardiel basin has focused human use during intervals with relatively lower effective moisture such as during the Late Pleistocene, but its evidence may have been submerged. This interpretation is confirmed by archaeological remains from Lago Strobel, another perennial lake with a comparable catchment located in the same climatic region and thus sharing the same climatic history as Lago Cardiel. Copyright © 2009 John Wiley & Sons, Ltd.