Carbone organique total (COT) et magnésium (Mg2+) : deux traceurs complémentaires du temps de séjour dans l'aquifère karstique     

Christelle Batiot  Christophe Emblanch  Bernard Blavoux 《Comptes Rendus Geoscience》2003,335(2):205-214

The Total Organic Carbon (TOC) is an interesting tracer of fast infiltration within karstic systems [3,7]. Regular sampling on several aquifers, from the experimental site of Vaucluse, made it possible to demonstrate the high sensitivity of this tracer compared with other commonly used chemical and isotopic tracers in karstic hydrogeology. The complementarity of magnesium, indicator of the residence time of water within the system, and TOC appears as a relevant tool in order to characterize the behaviour of the aquifer, to differentiate the water types which participate to the karstic flow (fast infiltration, unsaturated zone, saturated zone) and then, to evaluate their vulnerability.  相似文献   

Elemental composition of calcites in late Quaternary pedogenic calcretes from Gujarat, western India     

Aniruddha S. Khadkikar 《Journal of Asian Earth Sciences》2005,25(6):893-902

Pedogenic calcretes commonly exhibit clotted micrite, circum-granular calcite (grain coats) and microspar/spar veins. The three calcite-types with different dimensions were analyzed for their magnesium content to determine the relationship between crystal elongation and magnesium incorporation. The results show a very low MgO content for grain coats and microspars and high values for clotted micrite indicating that the ideal kinetic model does not hold true and several variables govern the end composition of calcites. The magnesium concentrations of meteoric calcites are genetically linked to the evolutionary history of the soil and climate. Grain coats, which are elongated calcites, contain the least amount of Mg and is related to the initial stages of pedogenesis wherein the limiting factor is the Mg/Ca ratio of the parent fluid. Lower magnesium contents arise due to smaller quantities of Mg being released during incipient weathering. Micrite morphology and composition is controlled by the greater availability of Mg ions through weathering, higher pCO₂ in soil due to increased time-dependent soil respiration, which causes a rise in calcite precipitation rates and clay authigenesis. This in turn exerts a physical control on morphology by occluding pore space and providing numerous nuclei for calcite precipitation. The wide variability in spar cements is inherently controlled by inhomogeneties in parent fluid compositions with lower-than-micrite values on account of slower precipitation rates.  相似文献   

无机晶须研究进展Ⅲ:碱式硫酸镁晶须的制备及应用   总被引：8，自引：2，他引：8       下载免费PDF全文

乃学瑛  叶秀深  崔香梅  李武 《盐湖研究》2005,13(3):22-28

碱式硫酸镁晶须是新型的阻燃、增强纤维材料,有着广阔的应用前景。文章较详细地介绍了碱式硫酸镁晶须的性质、制备方法及用途。指出加强其应用基础研究,是镁资源综合利用的一条重要途径。  相似文献   

氢氧化镁阻燃剂的研究现状   总被引：6，自引：0，他引：6       下载免费PDF全文

闫修川  李召好  李法强  马培华 《盐湖研究》2005,13(3):58-61

通过分析氢氧化镁作为阻燃剂的优缺点,评述了现阶段对氢氧化镁的改性应用,并提出了今后氢氧化镁阻燃剂的发展趋势。  相似文献   

纳米氢氧化镁的制备   总被引：1，自引：0，他引：1       下载免费PDF全文

胡章文  汪兵  单承湘  陶庭先 《盐湖研究》2005,13(4):47-50

以氯化镁和氢氧化钠为原料,添加表面活性剂,直接利用表面活性剂在固/液界面的“双亲性”使其吸附在新生成的氢氧化镁微粒上,制备纳米氢氧化镁。并采用X-射线和透射电镜等对样品进行表征,结果表明样品晶型发育完善,样品为片状、粒径为85 nm、粒度均匀且分散性好的纳米氢氧化镁粉体。  相似文献   

天然石膏及其开发利用研究进展   总被引：11，自引：0，他引：11  

李爱玲 《矿产与地质》2004,18(5):498-501

在总结天然石膏的矿物特征及其开发利用发展变化的基础上，重点介绍了其开发利用研究的主要进展，即利用天然石膏制备超高强石膏材料、硫酸钙晶须、石膏超细粉，以及介绍了天然石膏先进的煅烧设备——Peter磨和单转子锤式烘干机。  相似文献   

辽宁大石桥花岗质岩石成因分析及其在硼矿勘查中的意义   总被引：8，自引：0，他引：8  

刘敬党  肖荣阁  王翠芝  周红春  费红彩 《吉林大学学报(地球科学版)》2005,35(6):714-719

通过大石桥硼矿区花岗质岩石成因的研究,提出花岗质岩石属层状混合花岗岩成因,并以此为指导,在辽宁大石桥地区找到了3个中型硼矿床.花岗质岩石与其围岩变(浅)粒岩为渐变过渡关系,并呈现一些特殊的结构构造.其岩石化学成分变化较大,Al过饱和,AKCN值较大,Ti含量高.其特殊的岩石化学组成及氧同位素δ18O值均＞10‰,显示为混合花岗岩特征.花岗质岩石与其围岩变(浅)粒岩的REE组成特征一致,LREE/HREE平均值为3.86;负Eu异常,δEu平均为0.62,Eu/Sm平均值为0.163,与地壳来源的花岗岩及沉积岩的数值相近.该区花岗质岩石并非岩浆底辟作用形成的岩浆型花岗岩,而是层状混合花岗岩.  相似文献   

一种硼酸盐的新矿物—袁复礼石   总被引：3，自引：0，他引：3  

黄作良  王濮 《岩石矿物学杂志》1994,13(4):328-334

袁复礼石是一种Mg、Fe2+、Al和Ti的硼酸盐新矿物，发现于辽宁省宽甸县砖庙硼矿区。该矿物黑色，近不透明，金刚光泽-半金属光泽。反射色亮灰，内反射深红褐色。非均质性弱，偏光色红褐。晶体呈细柱状，O.1×0.2×l mm。晶体化学式为:(Mg0.91Fe2+0.09)(Fe3+0.56Al3+0.19 Mg0.17Ti0.11Fe2+0.10)1.13(B0.92O3.00)O。空间群Pnam, a=9.258(6)A，b=9.351(4)A， c=3.081(2)A，V=266.80(2)A，Z=4。 D=3.80 g/cm3, H=5-6，VHN50=843 kg/mm2，｛100}解理完全。红外光谱吸收谱带为:1387, 1210, 1024, 951, 733, 600, 510和408 cm-1。穆斯堡尔谱证明，以三价铁为主，二价铁较少。Fe3+占据M(1)晶位，Fe2+占据M(1)和M(2)晶位。袁复礼石为硼钛镁石的富Fe3+类似物。  相似文献   

CO₂-driven cation leaching after tropical forest clearing     

Daniel Markewitz  Ricardo de O. Figueiredo  Eric A. Davidson 《Journal of Geochemical Exploration》2006,88(1-3):214

The objective of this study was to investigate the role of dissolved CO₂ (H₂CO₃*) as a mechanism of cation removal from surface soils under secondary land uses in the tropics. Soil leachate columns were prepared with 0–10 cm soils from mature and secondary forest, and managed pastures, and extracted with H₂CO₃* from deionized water equilibrated with 0%, 0.5%, 1%, and 10% CO₂ (g). Extraction of soil cations slowed over time following an exponential form for the cumulative data. The rate of cation concentration decline varied as a function of CO₂ concentration with the 10% solution resulting in a greater percent decline with extraction volume. Potassium removal from the exchange sites of all soils and for all solutions was nearly complete ranging from 85% to 97% while removals of Mg (31% to 71%) and Ca (12% to 42%) were lower. The asymptotic patterns of cation loss observed in this study suggest that H₂CO₃* acid-driven losses of cations may become self-limiting over time. Other stronger acids from atmospheric deposition or organic sources may serve to perpetuate cation removal, and re-forestation on these cleared lands would certainly re-distribute cations from soils to vegetation.  相似文献   

共沸蒸馏置换干燥法制备纳米氧化镁粉体的研究   总被引：2，自引：0，他引：2       下载免费PDF全文

王宝和  张伟  张文博  范方荣 《盐湖研究》2006,14(3):34-38

以六水氯化镁和尿素为原料,采用均匀沉淀法制备出氢氧化镁沉淀,利用不同共沸蒸馏置换干燥法除去沉淀中的湿分,再将干燥的氢氧化镁粉体经马弗炉煅烧得到纳米氧化镁粉体;通过透射电子显微镜和X射线衍射仪的表征与分析,研究不同共沸蒸馏置换干燥法对纳米氧化镁粉体形貌、颗粒尺寸和团聚情况的影响;探讨了共沸蒸馏置换干燥的基本原理、操作方法和置换剂的选择原则。  相似文献