三门湾表层沉积物黏土矿物特征及来源分析

利用XRD方法分析了三门湾表层沉积物中的黏土矿物组成和含量,结合沉积物粒径趋势分析及长江和三门湾流域中小河流的黏土矿物组合特征,开展了三门湾沉积物的来源分析。结果表明,三门湾表层沉积物中黏土矿物以伊利石为主,其次为高岭石和绿泥石,蒙脱石含量最低。其中,伊利石高值区位于海湾中部,高岭石和绿泥石高值区分布在港汊附近,蒙脱石则在近岸呈斑块状分布。三门湾现代表层沉积物主要来源于长江入海物质,海湾周边短源山溪性河流带来的物质仅影响了河口近岸区。     

近2.1 Ma以来帕里西维拉海盆黏土矿物输入变化及其对中更新世气候转型的响应

对帕里西维拉海盆PV090102孔2.1 Ma以来沉积物中黏土矿物的含量、特征参数和形貌特征进行了分析,结果表明,黏土矿物以伊利石(48%)和蒙皂石(34%)为主,绿泥石(13%)和高岭石(6%)含量较低。伊利石结晶度平均为0.29°△2θ,表明其形成于气候寒冷且水解作用弱的陆地源区;伊利石化学指数平均为0.32,表明该孔伊利石为富Fe-Mg伊利石,且经历了较强的物理风化。黏土矿物的组合特征和形貌特征表明,蒙皂石主要来源于周围火山岛弧,伊利石、绿泥石和高岭石主要来源于亚洲大陆风尘。在中更新世气候转型期,伊利石通量、绿泥石通量和高岭石通量均呈增加趋势,这与该孔总的风尘通量和风尘石英通量的变化趋势一致,且与亚洲大陆干旱化一致,表明其响应了中更新世气候转型期亚洲内陆的干旱变化,因而可以作为亚洲内陆干湿变化的示踪指标。此外,第四纪以来PV090102孔蒙皂石通量的变化与该孔火山物质通量的变化趋势具有很好的一致性,因而可以作为火山物质输入西菲律宾海的替代指标。     

Solar Type III Bursts and the Generation of Backward Langmuir Wave

It is generally believed that the conversion of Langmuir wave (LW) to electromagnetic wave is the generating mechanism of solar type III bursts. The Langmuir wave can be easily excited by the instability of the electron-beam current, and the interaction of the forward and backward Langmuir waves is considered to be the cause for the second harmonic of a type III burst, but, so far, the dispersion equation and generating mechanism of the backward Langmuir wave have not yet been thoroughly studied. For the equation of two-stream instability with temperature included, an analytical solution is derived. It is found that the dispersion relation of the forward LW strongly depends on the beam-current speed, while that of the backward LW depends only on the thermal velocity, when the other parameters are fixed. These analytical results are partially confirmed by particle-in-cell (PIC) simulations. With the PIC simulation, the generating mechanism of the backward LW is studied, and it is revealed that the backward LW can not be excited directly by the electron-beam current, and that its energy is obtained basically from the scattering of the forward LW. However, the electron-beam current does cause a direct amplification of the second harmonic of the forward LW.     

Modeling fluvial response to in‐stream woody vegetation: implications for stream corridor restoration

River restoration and bank stabilization programs often use vegetation for improving stream corridor habitat, aesthetic and function. Yet no study has examined the use of managed vegetation plantings to transform a straight, degraded stream corridor into an ecologically functional meandering channel. Experimental data collected using a distorted Froude‐scaled flume analysis show that channel expansion and widening, thalweg meandering and riffle and pool development are possible using discrete plantings of rigid, emergent vegetation, and the magnitudes of these adjustments depend on the shape of the vegetation zone and the density of the vegetation. These experimental results were verified and validated using a recently developed numerical model, and model output was then used to discuss mechanistically how rivers respond to the introduction of in‐stream woody vegetation. Finally, a hybrid method of meander design is proposed herein where managed vegetation plantings are used to trigger or force the desired morphologic response, transforming a straight, degraded reach into a more functional meandering corridor. It is envisioned that such numerical models could become the primary tool for designing future stream restoration programs involving vegetation and assessing the long‐term stability of such activities. Copyright © 2007 John Wiley & Sons, Ltd.     

东亚季风研究的进展

降水所释放的潜热是驱动全球大气环流主要的能量来源,是太阳能向大气热动力能转化的重要途径。准确测量降水云中各高度层的潜热释放率是人类长期努力而未实现的目标。本文阐述了降水潜热在气候系统水循环和能量平衡中的重要意义,以及已有的对热带降水潜热垂直结构的理解和共识,并介绍了遥感降水及其潜热三维结构的主要卫星计划和传感器。特别分析了卫星遥感降水潜热的两大类方法,即查表法和物理反演法。对美国宇航局的CSH算法、日本空间局的SLH算法以及中国科学技术大学的VPH算法的原理做了较为详细的介绍,着重分析了不同算法的思路、特点、适用性和不确定性。

     

PHYSICO‐GEOCHEMICAL AND MINERAL COMPOSITION OF NEEM TREE SOILS AND RELATION TO ORGANIC PROPERTIES

The Neem tree, the oil of which has a long history of pesticide, fertilizer and medicinal use in India, has been studied extensively for its organic compounds. Here we present a physical, mineralogical and geochemical database resulting from the analyses of two Neem soil profiles (epipedons) in India. Neem tree derivatives are used in the manufacture of a variety of products, from anti‐bacterial drugs and insecticides to fertilizers and animal feeds. A preliminary geochemical and mineralogical analysis of Neem soils is made to explore the potential for chemical links between Neem tree derivatives and soils. Physical soil characteristics, including colour, texture and clay mineralogy, suggest the two pedons formed under different hydrological regimes, and hence, are products of different leaching environments, one well‐drained site, the other poorly drained. Geochemically, the two Neem soils exhibit similarities, with elevated concentrations of Th and rare earth elements. These elements are of interest because of their association with phosphates, especially monazite and apatite, and the potential link to fertilizer derivatives. Higher concentrations of trace elements in the soils may be linked to nutritional derivatives and to cell growth in the Neem tree.     

3种水稻土时间序列黏粒矿物的组合特征与物源指示意义

对南方丘陵区3种不同母质水稻土时间序列黏粒矿物的X-射线衍射（XRD）进行分析发现：① 紫色砂页岩（PS）母质起源土壤的黏粒矿物以高岭石类似矿物为主;第四纪红黏土（RC）母质起源土壤的黏粒矿物以高岭石类似矿物、伊利石类似矿物与三羟铝石为主;红砂岩（RS）母质起源土壤的黏粒矿物以1.4 nm过渡矿物、高岭石类似矿物与三羟铝石为主。② 这3种母质土壤种稻后黏粒矿物的变化大体可分为2种情况。RC与RS母质的起源土壤种稻后,土壤黏粒矿物的变化相对较小,伊利石类似矿物相对含量有所增加,这可能主要与钾肥的持续施用有关。PS母质的起源土壤种稻后,土壤黏粒矿物变化相对较大,表现为高岭石类似矿物相对含量降低,低结晶度的伊利石或次生绿泥石与三羟铝石相对含量上升。PS母质发育的土壤种稻后脱钾明显且主要集中在原生矿物部分。这种原生矿物的脱钾作用对土壤黏粒含量和黏粒矿物的类型都有较大影响。③ 起源土壤的黏粒矿物通常会被水稻土所继承,并在水稻土发育过程中相对稳定,可以用其来指示起源土壤（或母质）的物源组分。     

Effects of Poplar Plantations on the Physical and Chemical Properties of Soils: A Case Study in the North China Plain

In recent years, large areas of farmland in the North China Plain have been converted into short-rotation poplar plantations. To analyze the impacts of poplar plantations on soil, 22 soil samples were collected and assayed from the soil profiles of a corn field and a poplar plantation. The results showed that the average soil moisture content of the soil profile in the poplar field was 2.6 percent lower than that of the arable land. The maximum difference in soil moisture content was found in the upper 0-10 cm of topsoil. Soil organic matter and nitrogen, phosphorus and potassium in the cornfield were significantly higher than in the poplar field. Higher nutrient content in the corn field may result from higher fertilizer inputs and the practice of returning straw to the cropped field. The analysis also showed no significant increase in soil organic matter content in deeper soil layers of the poplar field, which means that the conditions are not favorable for the formation of soil organic matter, or that soil organic matter needs a longer time to develop. Elements such as magnesium, iron, manganese and copper in both the corn field and the poplar field had a tendency to accumulate with increasing soil depth. Magnesium, iron, manganese and copper in the 0-80 cm soil layer of the poplar field were higher than those of the cornfield, but the situation was reversed at depths greater than 80 cm. It is concluded that poplar trees consume a large amount of soil moisture and soil nutrients. Local governments should prevent the development of new plantations of fast-growing trees in farmland and help farmers to recover their farmland from forestry plantations.     

Climato-limnological signals during the past 260 000 years in physical properties of bottom sediments from Lake Baikal

The St.16 core obtained from the Academician Ridge of Lake Baikal in eastern Siberia may span about 260 000 years, and some physical properties of the core samples are closely related to aquatic paleoproductivity and climatic change. The median of grain size, grain density, and water content fluctuate synchronously. They also are connected with change in the abundance of biogenic silica (diatoms). The physical parameters indicate that there were high aquatic productivity periods around interglacial periods (MIS 5 and 7; 70 000-125 000 yr B.P. and 180 000-250 000 yr B.P.). Comparatively large clastics were transported from outside of the lake through various routes (ice rafting, etc.) in addition to fluvial routes during the glacials or 'stadials. There are ca. 20 000 yr, 40 000 yr and 100 000 yr periods in the variations of physical properties. These are related to the three Milankovitch parameters of solar insolation.     

湖泊沉积物的矿物组成、成因、环境指示及研究进展

湖泊沉积物是不同地质、气候、水文条件下各类碎屑、黏土、自生/生物成因矿物以及有机物质等的综合体。沉积矿物蕴含着丰富区域和全球环境演变信息,如湖水的化学组成、流域构造、气候、水文以及人类活动的相互作用等。相关信息可以赋存在矿物外部微形貌、内部微结构、化学组成、物理和化学性质、同位素组成、谱学特征、成因以及共生组合等方面。因此,湖泊科学的许多关键课题都离不开矿物学,特别是在利用湖泊沉积物进行区域及过去全球变化研究中,深入的机理研究归根到底都要涉及矿物学,如流域化学风化作用、粒度组成、生物壳体化学组成、测年材料的选择等。然而,由于湖泊沉积物中矿物的多源性、复杂性,如何有效提取和解译其中的环境信息,是一项长期困扰研究者的课题,湖泊沉积矿物学的研究往往被许多研究者所忽视,中国的相关研究也较为薄弱。笔者综述了湖泊沉积物中碎屑、黏土、自生/生物矿物的矿物组合、特征、成因在(古)环境反演中的作用及最新研究进展,提出除了继续加强对湖泊沉积物中矿物来源、成因和古环境示踪的深入研究以外,矿物相间的转变及其对湖水和孔隙水组成的响应、一些非晶质或隐晶质及低丰度矿物相在湖泊化学和动力学中的作用也是很有潜力的研究领域,最后提出了研究中存在的一些问题、面对的挑战以及对研究前景的展望。