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   

The role of saline solution properties on porous limestone salt weathering by magnesium and sodium sulfates   总被引：4，自引：0，他引：4  

E. Ruiz-Agudo  F. Mees  P. Jacobs  C. Rodriguez-Navarro 《Environmental Geology》2007,52(2):269-281

Saline solution properties, viscosity in particular, are shown to be critical in salt weathering associated with sodium and magnesium sulfate crystallization in porous limestone. The crystallization of sodium and magnesium sulfate within a porous limestone has been studied at a macro- and microscale using different techniques, including mercury intrusion porosimetry, environmental scanning microscopy and X-ray computed tomography. Such analysis enabled the visualization of the crystallization process in situ, and at high magnification, yielding critical information as to where and how salts crystallize. Sodium sulfate decahydrate (mirabilite) tends to crystallize in large pores as euhedral micron-sized crystals formed at low supersaturation near to the surface of the stone. In contrast, magnesium sulfate heptahydrate (epsomite) tends to precipitate as anhedral wax-like aggregates formed at high supersaturation and distributed homogeneously throughout the stone pore system filling large and small pores. While the former crystallization behavior resulted in scale formation, the latter led to crack development throughout the bulk stone. Ultimately, the contrasting weathering behavior of the two sulfates is explained by considering differences in flow dynamics of solutions within porous materials that are mainly connected with the higher viscosity of magnesium sulfate saturated solution (7.27 cP) when compared with sodium sulfate saturated solution (1.83 cP). On the basis of such results, new ways to tackle salt weathering, particularly in the field of cultural heritage conservation, are discussed.  相似文献   

Determination of Trace Elements in Bauxite Using Laser Ablation‐Inductively Coupled Plasma‐Mass Spectrometry on Lithium Borate Glass Beads          下载免费PDF全文

Dewany A. Monsels  Manfred J. Van Bergen  Paul R. D. Mason 《Geostandards and Geoanalytical Research》2018,42(2):239-251

  相似文献   

利用盐湖老卤与元明粉制取七水硫酸镁工艺研究          下载免费PDF全文

牛韩根  李海民 《盐湖研究》2017,25(3):39-45

氯化镁和硫酸钠作原料,以K~+,Na~+,Mg~(2+)//Cl~-,SO_4~2-H_2O及Na~+,Mg~(2+)//Cl~-,SO_4~2-H_2O水盐体系相图为理论依据,研究了氯化镁和硫酸钠分解转化—冷却结晶法生产七水硫酸镁的工艺路线。考察氯化镁和硫酸钠分解转化温度、分解转化时间、各物料配比关系等因素对制备七水硫酸镁的影响,确定了各试验因素对试验结果的影响主次顺序,得出了试验结果。  相似文献   

高体积分数Mg2B2O5w／AZ91D复合材料的热疲劳性能          下载免费PDF全文

丁雨田  王府  金培鹏  胡勇  万国顺  李静 《盐湖研究》2009,17(1)

用真空气压渗流装置成功制备了硼酸镁晶须体积分数为52%的Mg2B2O5w/AZ91D镁基复合材料。观察了该材料在30~350℃热循环条件下热疲劳裂纹扩展的形貌,并分析了热疲劳短裂纹的产生和扩展机制。结果表明,材料的热疲劳裂纹的扩展与热循环的次数以及材料的内部结构有关。  相似文献   

不同类型氢氧化镁阻燃剂填充聚丙烯（PP）复合材料力学性能研究   总被引：1，自引：1，他引：0       下载免费PDF全文

姬连敏  李丽娟  孙秋菊  陈大福  聂峰  曾忠民  宋富根  刘志启 《盐湖研究》2009,17(4):46-52

研究了普通氢氧化镁(MH)、六角片状MH和硬脂酸改性MH分别填充聚丙烯(PP)复合材料的性能。用FTIR、SEM和TG对上述3种类型MH及其复合材料的结构和形貌进行了分析。试验结果表明:相比普通MH,六角片状MH和硬脂酸改性后的MH有效降低了表面极性,大大降低了对复合材料的力学性能的影响,显著提高了复合材料的热稳定性;4%SA改性MH比6%SA改性MH填充PP,界面相容性好,对复合材料力学性能的影响小。硬脂酸湿法表面处理氢氧化镁改性的最佳条件为:硬脂酸用量4%,处理温度85~90℃,处理时间60 min,料浆浓度10%。  相似文献   

辽东后仙峪地区元古界超镁橄榄岩岩石学及其成因   总被引：2，自引：0，他引：2  

肖荣阁  刘敬党  吴振  王斌  冯佳睿 《现代地质》2007,21(4):638-644

超镁橄榄岩是作者在辽东大石桥后仙峪地区发现并命名的一种新类型岩石,是以镁橄榄石分子组成为标准而定义、阳离子过剩的一种岩石。由于阳离子过剩而形成独立的铁镁氧化物矿物,因此岩石的主要矿物为镁橄榄石、硅镁石、水镁石及磁铁矿。该超镁橄榄岩中矿物呈粒状、板状结构,具有角砾状火山喷发构造、类鬣刺状熔岩冷凝构造及团块状熔离构造。岩石具有分层现象,下部为镁橄榄岩,上部为磁铁矿硅镁石岩,其中含有镍黄铁矿,并构成海绵陨铁结构。岩石学研究表明这是一套富镁质超基性火山岩,相当于科马提岩,作为辽东硼矿的容矿岩石,它为镁硼酸盐矿床的形成提供了丰富的镁质来源。  相似文献   

矿渣镁水泥初探          下载免费PDF全文

何荣昌  孙庆国 《盐湖研究》1999,7(3):45-51

研究了添加矿渣对传统镁水泥进行改性,同时探讨了磷酸盐对镁水泥耐水性能改善的效果,提高了镁水泥的经济价值和实用性。  相似文献   

硼酸铝晶须的性质、制备和开发前景   总被引：11，自引：1，他引：10       下载免费PDF全文

李武 《盐湖研究》2000,8(3):40-43

无机材料在国民经济和国防建设中均占有重要地位。简单介绍了一种重要的新型无机功能材料——硼酸铝晶须的性能、制备和应用前景。  相似文献