青藏高原东缘上地幔顶部Pn波速度结构及各向异性研究

本研究使用中国地震局地壳应力研究所2010—2011年期间在云南地区布设流动地震台站以及青藏高原周边地区固定地震台站记录到的波形资料,提取了大量高质量Pn波到时资料.联合中国地震台网观测报告,我们获得了一个新的青藏高原东缘上地幔顶部Pn波速度和各向异性结构模型.结果显示,研究区内上地幔顶部存在明显横向不均匀性.古老盆地和稳定地台区如四川盆地、柴达木盆地、拉萨地块和阿拉善块体呈现为明显高波速异常,而祁连山至西秦岭褶皱带和川滇菱形块体北部等为相对弱高波速异常.在龙日坝断裂带以东的松潘—甘孜地块往南沿安宁河—则木河断裂至川滇菱形块体南部显示为一条近南北向明显低波速异常.三江褶皱系、缅甸弧俯冲带以及四川盆地东南等地区为明显低波速异常.地壳强震多发生在高波速异常边缘或高低波速异常过渡带上,表明地壳强震的孕育可能还与地幔构造作用存在一定相关性.青藏高原东构造结的各向异性快波方向呈顺时针旋转分布,与印度—欧亚碰撞密切相关.龙门山断裂带东西两侧的各向异性快波方向发生明显变化,由其西侧松潘—甘孜地块下方的NE向转变为四川盆地下方的近EW向,说明青藏高原物质流动遇四川盆地后分为NE和SW向两支.在川滇地区26°N以南地区上地幔顶部各向异性呈现近NS向与地表GPS观测相一致,但与SKS分裂结果存在较大差异,可能表明地壳与上地幔顶部形变表现为耦合现象,而上地幔顶部至岩石圈内部则存在解耦现象.     

The possible role of magnetic measurements in the discrimination of Sahara/Sahel dust sources

The mineral magnetic properties of deposited dusts collected along a broadly north‐to‐south transect across Niger have been investigated on both a bulk and particle size‐specific basis. Dusts display a general north‐to‐south gradient in fine‐grained ferrimagnetic mineral (magnetite/maghemite) concentrations, with samples south of the Sahara/Sahel transition (south of ~15·5^o N) generally containing greater concentrations than dusts from further north where the climate is much drier. This distinction is seen especially clearly in the clay (< 2 µm) fraction, which harbours the products of weathering and pedogenesis. This gradient in ferrimagnetic mineral concentrations broadly parallels that previously reported for surface soils/sands across a similar latitudinal range. We suggest that the regional distinction in both dust and surface soil/sand magnetic properties can be related to differences in weathering regime between the arid Saharan parts of the transect and the Sahel sites where higher rainfall has permitted stronger weathering and pedogenesis. Given that the weathering‐related magnetic signatures in the clays dominate the magnetic properties of the < 16 µm fractions in these samples, and that this particle size component is most likely to be involved in long‐range transport, magnetic measurements hold out the potential of discriminating Sahara and Sahel dusts deposited in remote areas. Copyright © 2011 John Wiley & Sons, Ltd.     

南非负责任旅游的兴起及其意义

南非负责任旅游对南非的社会经济发展、政治民主建设起着非常重要的作用,特别是推动了南非构建公平社会的进程。本文概括了南非负责任旅游的兴起背景,分析了南非政府实施负责任旅游后初见成效的原因,剖析南非负责任旅游在缓解种族歧视、减少贫困、公平分配利益等方面对建设公平社会的意义。     

WEST AFRICAN ENVIRONMENTAL NARRATIVES AND DEVELOPMENT‐VOLUNTEER PRAXIS*

ABSTRACT. Environmental narratives in Africa have been examined in a flurry of publications since the mid‐1990s. In this article we seek to offer insights into the role and motivations of volunteer development workers in perpetuating environmental narratives. We examine the factors that led to the questioning or nonquestioning of environment‐development discourses and their influence, if any, on the actual work undertaken by volunteers. As former development volunteers, we also explore the role that the development‐volunteer experience subsequently played in shaping our own research as academics. Our analysis is based largely on our tenure as U.S. Peace Corps volunteers in Mali from 1987 until 1989 and our later experiences as academics. We draw on our memories, interviews with former colleagues, and training materials to describe how volunteers were introduced to, and encouraged to act on, environmental problems in the West African Sudano‐Sahel. We adopt a reflexive approach to explore briefly how our experiences as volunteers influenced our research and writing as academics.     

六盘山东麓地区岩溶地质特征分析

六盘山东麓地区岩溶具有我国北方岩溶的基本特点,地表岩溶形态以常态山和干谷为主,地下岩溶以溶隙为主。该区岩溶发育程度除受岩性条件决定外,同时还受构造因素和水动力条件的控制。在分析影响岩溶发育因素的基础上,指出了岩溶在区域上的分布规律,同时划分了岩溶含水岩组,并论述了各岩组的富水性。     

黄、东海海洋黄色物质的卫星反演

在对物理特性分析的基础上, 建立了黄、东海海域卫星离水辐射率黄色物质反演模式, 并利用2003年4月15日SeaWIFS卫星获得的黄、东海海域离水辐射率(Lw)数据反演给出了黄海中部—东海南部(北起33°52′N, 南到22°00′N; 西起122°36′E, 东止125°28′E)海域的黄色物质分布图。结果分析表明, 研究区给出的黄、东海海域黄色物质吸收系数在0.003—0.13m-1范围内, 与大西洋北海测得的黄色物质吸收系数比较接近, 但明显低于波罗的海和地中海, 更低于世界各地沿海海湾。平均而言, 比在太平洋点测黄色物质吸收系数值高约80%, 达0.09m-1左右。在水平分布上, 黄海海域的黄色物质吸收系数明显高于东海海域, 沿岸水域明显高于远海水域。受长江水系和黄海环流以及沿岸排污等要素的影响, 在长江口以外和黄海中、南部水域及其沿岸附近有明显的高吸收系数值聚集区。同时发现, 在黄海西部沿岸, 由于有较高反射率的高泥沙含量的影响, 对该区黄色物质的反演产生了较大的影响, 特别在苏北沿岸和长江口水域尤其如此。而在韩国、日本西海岸、浙江及福建沿岸水域则比较正常的给出了黄色物质的分布。     

Stomach content analysis of juvenile Cape stumpnose Rhabdosargus holubi in the Swartkops Estuary,South Africa

Stomach content analyses were performed on the Cape stumpnose Rhabdosargus holubi. The contents were identified to species level and the dietary importance of each component assessed by employing unrelated quantifying methods, which were subsequently combined to determine an index of relative importance (IRI). The index was determined on a seasonal basis as well as for individual sampling stations. The aquatic macrophyte Zostera capensis was the single most abundant item and, together with filamentous algae, constituted the major proportion (IRI = 7 314) of the diet. Crustacea were the next most abundant (IRI = 6 534), followed by Mollusca (IRI = 160). Stomach contents from the sampling stations in the lower reaches were dominated by aquatic macrophytes and algae, whereas those from the middle and upper reaches had a higher incidence of Crustacea. Mollusca in the diet were uniformly distributed throughout the estuary. There was considerable flexibility in the feeding pattern of R. holubi.     

Life history of Plesionika edwardsi (Crustacea,Decapoda, Pandalidae) around the Canary Islands,Eastern Central Atlantic

The life history of Plesionika edwardsi (Brandt, 1851) around the Canary Islands in the Eastern Central Atlantic was investigated, based on a total of 11 434 shrimps ranging in length between 8 and 40 mm carapace length (CL). The species carries out seasonal migrations; they concentrate in deep water during winter, move shallower in summer and return to deep water again in autumn. Ovigerous females occur throughout the year, but a spawning peak was determined between April and September. The size at maturity for females was approximately 26 mm CL. Shrimp size generally increased with increasing water depth. The growth parameters for males were L _∞ = 25.75 mm CL and K = 0.55 year^?1, and L _∞ = 28.28 mm CL and K = 0.66·year^?1 for females. The species displays the typical reproductive pattern of tropical pandalids and is dioecious.     

The first African Marine Mammal Colloquium,South Africa,May 2010

The African Marine Mammal Colloquium (AMMC) was initiated to provide a platform for increased collaboration and communication between researchers working on marine mammals in and around Africa. The first meeting of the AMMC was held at Kleinbaai, South Africa, in May 2010. Talks were presented by each of the 48 participants and a number of discussion groups were held. Several countries were represented but most presentations and discussions were centred on research within the host country. In all, 13 papers that were based on presentations at the AMMC were selected after peer-review to appear in a special issue of the African Journal of Marine Science. Its theme, ‘Conservation biology of marine mammals in the southern African subregion’, reflects both the geographical area represented in these papers and their common subject.