Geochemical Characteristics and Sedimentary Environment of the Salawusu Section

The chemical compositions of and the contents of CaCO3, free Fe2O3 and REE in the sediments of the Salawusu section have been analyzed to investigate the geochemical features of different sedimentary facies and explore their sedimentary enironmetnts during the Late Pleistocene.The con-tents of CaCO3, free Fe2O3 and ∑REE in lacustrine deposits of the middle part of the section are higher than those in the other parts ,except SiO2 which shows an opposite trend.According to the distribution characteristics of the components mentioned above, the section may be divided into four parts which are equivalent to those divided in terms of lithologic characters and sedimentary facies.More remarkable characteristics were observed with respect to the distribution of CaCO3, free Fe2O3,∑REE and SiO2/Al2O3 and FeO/Fe2O3 ratios, which can be adopted as the geochemical indices for paleoclimate division.From the above, four paleoclimate stages have been distinguished for the deposition process.The first stage ,dated at 0.20-0.15Ma, is characterized by a dry and cold climate,the second stage, ranging from 0.15 to 0.07 Ma ,by a warm and slightly dry climate,the third stage ,about 0.07-0.01Ma ,by a cold and humid climate;and prevailing in the last ten thorsand years is the fourth stage,with the climate changing graduall from warm-humid to warm-dry.     

无定形态游离氧化铁脱水老化对粘性土物理性质的影响

无定形态游离氧化铁以其自身的特性及其脱水老化作用,对粘性土的物理性质、水理性质乃至工程性质产生了一定程度的影响。本文就粘性土的物理性质、水理性质及力学性质在无定形态游离氧化铁脱水过程中的变化进行了初步研究,期望对粘性土的土工测试方法及参数的合理测定有所裨益。     

Cd(Ⅱ)水合/水解产物结构和稳定性的理论研究

用密度泛函(DFT)B3LYP方法研究了Cd(Ⅱ)水合与水解产物的几何结构、电子结构及稳定性.结果表明,水合产物的稳定性均优于水解产物,其稳定性顺序为:Cd(OH)2-4相似文献   

铁(氢)氧化物矿物对有机污染物的光催化氧化作用

对水溶液中(氢)氧化铁的光催化氧化反应的发展与机理研究进行了总结,着重对近十年来应用针铁矿／过氧化氢进行光催化氧化环境中有机物的研究进展及其环境矿物学意义作了概述和探讨。采用天然生物矿化的纳米针铁矿／过氧化氢以偶氮染料甲基橙为光解模型物进行了光催化氧化的初步研究,结果表明铁细菌形成的针铁矿具有降解生物难降解的有机污染物的能力。在甲基橙溶液初始浓度为30mg／L,铁细菌矿化的针铁矿用量2．5g／L,反应体系H2O2的初始浓度97mmol／L,pH值为6．92,15W紫外灯照射2h后,甲基橙浓度可降低33％。     

天然气水合物的晶体结构及水合系数和比重

天然气水合物具有巨大的资源前景和极强的环境和灾害效应，是目前地学研究中的热点，天然气水合物存在三种基本晶体结构，五种大小不同的气体占据空间，不同大小的气体分子进入大小相近的气体占据空间，形成稳定的天然气水合物，分子太大和太小的气体则不能形成水合物，天然气水合物的气体充填率常小于1.0，水合系数大于理想水合系数，而且受气体类型、组成、温度和压力等条件影响，气体类型明显影响天然气水合物的比重，烃类气体可形成比重小于海水的天然气水合物，CO2的水合物比重可明显高于海水比重。     

河北阳原盆地井儿洼钻孔岩心氧化铁变化的古环境记录

系统分析了阳原盆地西部井儿洼钻孔剖面的Fe2O3、FeO、TFe(全铁)、Fe3 /Fe2 的变化特点,探讨了阳原古湖氧化铁地球化学特征及其所记录的气候变迁规律。结果表明,阳原盆地的沉积环境相对富集铁,气候总体较温和,垂向上的变化记录了气候的变化过程分为7个明显的阶段。0.2Ma以前以还原环境为主,以后以氧化环境为主。井儿洼岩心沉积物中全铁谱分析表明,0.78Ma之后,具有显著的21.7ka岁差周期,证明了天文因素对气候的影响,而100ka的周期不明显,这与黄土、深海沉积物的记录存在差别。另外还存在390ka、156ka、52ka、33.9ka及14.4ka等周期,表现了湖泊记录的古气候周期的复杂性。     

Surface mineralogy of degraded agricultural lands affected by natural acid-saline seeps, southwestern Australia

Acid and saline seeps are an increasing problem in the most parts of the world and Australia as well. They are areas of bare soil or reduced crop production. Seasonal surface sampling through topo-sequence of the study area and analytical results of XRD, SEM and VNIR indicate that morphological and mineralogical changes within a natural acid saline seep affected landscape revealed that seasonal differences in surface mineralogy. These dynamic and seasonally influenced changes to surface and near surface mineralogy of an acid saline seep affected landform during the wet months, due to waterlogging, the sulfidization process dominates, while during the drier months, oxidative weathering of pyrite and iron hydrolysis results in precipitation of iron oxyhydroxides at and near the surface with the generation of acidity. During the dry season, the surface mineralogy of the natural seepage zone is dominated by salts （halite）, sulfates （gypsum and barite） and, importantly, iron oxyhydroxides gel precipitates and crusts （ferrihydrite, goethite, schwertmannite）. The study found the iron oxyhydroxide minerals present in the surface crusts and precipitates reflect acid conditions, as opposed to halite and gypsum that reflect only saline conditions. The visible near infra-red （VNIR） reflectance spectra of the surface minerals from unaffected, salt crusted and acid seep areas, showed spectral differences expressed in the VNIR region due to absorption bands of iron oxides and hydroxides. This difference in the surface mineralogy during summer months can be readily identified via multi-spectral and hyper-spectral remote sensing methods mainly during summer,     

Eu3+水合离子在纳米二氧化硅表面的吸附与结构

采用发射光谱研究了不同pH和不同Eu初始浓度条件下,Eu在纳米二氧化硅-水界面的吸附特征。研究发现,当pH低时,Eu在纳米二氧化硅表面的吸附很少,随着pH的增加,Eu在纳米二氧化硅表面的吸附急剧增加,当出〉6时,几乎所有Eu都被吸附。研究同时表明,吸附在纳米二氧化硅与水界面的Eu离子种类也取决于pH值：当pH〈5时,吸附的Eu主要为Eu^3＋水合离子,当pH〉5时,吸附的Eu主要为Eu（CO3）^＋,甚至Eu（CO3）2^-离子。吸附的机理除了静电吸引外,更重要的是这些离子与纳米二氧化硅表面形成化学键,即表面化学吸附。