地貌形态指数反映的青藏高原东北部宛川河流域新构造活动

宛川河为黄河的一级支流,位于青藏高原东北部的兰州盆地东部.该区域历史时期曾发生多次6级以上地震.以DEM数据为基础,通过河流水系分析和地貌形态指数的计算,讨论了区域新构造活动特征.山前曲折度指数(SMF)在宛川河北为1.03~1.18,在兴隆山北前缘为1.83~2.88;河谷宽高比指数(VF)在宛川河北部为0.36~2.34,在南部的兴隆山为0.55~13.SMF与VF值的大小和分布特征表明研究区新构造活动活跃,且宛川河以北(前人推测有断层存在)新构造活动的活跃程度更高.流域盆地非对称性指数(AF)在宛川河北部东南端的异常揭示存在掀斜断块和褶皱运动;结合裂点分布和沟谷错断等地貌特征,发现宛川河北正断裂的东南端也存在西北--东南向走滑活动.     

早、中更新世东亚冬季风强度的快速变化

对黄土高原中部洛川黄土堆积进行了系统的粒度和磁化率测量,以黄土－古土壤中的粗颗粒组分,即＞３０μｍ颗粒的百分含量作为冬季风强度代用指标,根据一个独立的时间标尺,发现在１４５～１６５、２４０～２８０、３２０～３５０、３９０～４４０、６００～６４０、８６０～８９０、９００～９３０和１３３０～１４００ｋａＢ．Ｐ．东亚冬季风强度存在千年尺度快速变化的特征,冬季风加强事件的持续时间在１．４～７．２ｋａ之间,变化幅度也不相同;周期分析结果表明,这些古气候变化存在１．８９～４．０ｋａ之间的周期,由于时间标尺的精度还有待于进一步提高,在这里没有把冬季风强度变化与北大西洋沉积物记录的古气候事件进行对比,但是,实验结果证明在早、中更新世的某些阶段东亚冬季风强度存在快速变化的现象     

城市土地承载力研究进展

开展城市土地承载力研究既是对土地承载力研究体系的深化,也是对城市持续发展的有益探索。总结城市土地承载力研究的起源、发展、内容、方法以及在相关领域的应用,发现其多出自于城市规划、土地利用、资源环境、生态系统等领域的延伸,或为某一领域的一部分,而其自身的研究体系尚未形成。已有研究主要从承载主体、承载对象和影响因素3个视角探讨了与城市土地承载力相关的内容,重在分析和评价城市各类土地与人口规模、经济增长、社会发展以及生态环境之间的关系。在研究方法上,数理分析、模型方法、指标体系等被普遍采用,但各评价方法根据评价对象和城市特点有所不同,评估结果在很大的程度上依赖于选择的不同方法,从而使得到的结果之间缺乏可比性。在实践层面,城市土地承载力分析的实际应用还很薄弱,但其指导作用已经凸现。研究认为,城市土地承载力从基本概念到量化方法、再到实践应用的研究中还存在不足之处,今后的研究应当侧重于完善城市土地承载力自身的研究体系,并结合社会发展需求进行城市土地承载力的功能分区研究和预警研究,建立城市土地承载力状态与土地政策调控的互动机制,逐步加强研究方法的更新和研究成果的应用推广。     

1992-2015年中国沙漠面积变化的遥感监测与气候影响分析

目前,关于中国全域年际分辨率长时间序列沙漠面积变化及影响机制的研究较少。利用1995-2015年全国土地利用数据对1992-2015年地表覆被数据中的裸地进行校正,并采用2000年和2002年腾格里沙漠遥感影像解译结果对校正后的沙漠面积的精度进行验证,同时分析不同大气环流区沙漠面积变化的气候变化影响机制。结果表明：1992-2015年中国沙漠面积减少了86 704 km²,东部季风区沙漠面积减少最明显,其次是青藏高寒区,西北干旱区减少最小,减少面积分别是46 109、23 470、17 125 km²。其中,东部季风区沙漠面积减少占比最为明显,达到18.13%。土壤湿度是影响西北干旱区和青藏高寒区沙漠面积年际变化的关键因素,降水、相对湿度和土壤湿度对东部季风区沙漠面积变化有直接影响,林业生态建设工程、退耕还林还草等措施也有一定关系。近20年来中国北方风力减小和人类保护可能是东部季风区沙漠面积减少的主要因素。     

2009—2017年南沙群岛珊瑚礁砾洲演变

通过对南沙群岛永暑礁、西门礁和安达礁3个砾洲结合现场实测数字高度模型（DEM）的遥感影像分析,重建了2011（2009）、2013、2015、2017年4个时段的砾洲DEM,分析揭示出珊瑚礁砾洲不同时段的地形地貌特征及其演变过程。结果显示：2009—2017年间,安达礁砾洲以侵蚀为主,砾洲不断缩小,平均高度、面积和体积呈下降趋势;2011—2017年间,永暑礁砾洲以水平和垂直加积为主,砾洲不断扩大增高,平均高度、面积和体积呈增长趋势;西门礁砾洲以水平加积为主,面积呈增大趋势,而平均高度呈下降趋势,体积变化趋势不明显。2011—2017年间,永暑礁和西门礁砾洲呈现向东或东南礁坪内侧潟湖方向的移动,而安达礁砾洲2009—2017年间则向西北方向礁坪外侧移动,移动距离明显大于永暑礁和西门礁砾洲。3个砾洲的演变主要受季风浪和台风浪的控制,表现为砾洲缩减向礁坪外侧迁移和砾洲扩展向礁坪内侧潟湖迁移的2种不同演变模式,这与砾洲各自所在礁坪在珊瑚环礁中的位置,以及礁坪形态造成的礁坪水动力环境的差异有关。南沙群岛珊瑚礁砾洲地貌的演变为深入研究南海珊瑚礁灰沙岛地貌发育演化及动力机制提供了重要的科学基础。     

库姆塔格沙漠地表物质组成、来源和风化过程(英文)

Kumtagh Desert is one of the eight biggest deserts in China, but poorly investigated before our interdisciplinary study because of the difficulty of access. In this paper, 33 representative surface sediment samples were collected from the Kumtagh Desert and analyzed in the laboratory to obtain heavy mineral components and geochemical element contents. Results show that various kinds of heavy minerals are present in these samples, with high levels of epidote and hornblende. Si and Al take up a large part of chemical composition. Compared with the average composition of geochemical elements of the upper continental crust (UCC), except Si and Ca, all elements are depleted to a certain degree; Fe, Mg, Ca, P, Ti and Mn have high correlation coefficients in their contents. The mineral and geochemical composition of the Kumtagh Desert sediments have a similarity with that of rocks of Altyn Tagh Mountains, and the surface sediments of the alluvial/diluvial fans around the Altyn Tagh Mountains and that of the Taklamakan Desert, indicating that one major source of the Kumtagh Desert sediments is located in the Altyn Tagh Mountains. Alluvial deposits and lake sediments in Aqik valley and lower reaches of Shule River are prone to be eroded and transported by the strong northeasterly wind into the Kumtagh Desert, forming another source of the desert deposits. An A-CN-K ternary diagram shows that a weak degree chemical weathering by the loss of Na and K occurred in these sediments, whereas A-CNK-FM ternary diagram suggests that Fe and Mg have undergone a significant chemical differentiation. Physical weathering processes cause easy erosion and enrichment in fine particles for mafic minerals, thus coarse desert sand particles can be relatively depleted in Fe and Mg. The mineral and geochemical composition of sediments in arid regions experiencing less chemical weathering are mostly affected by physical weathering.     

以气候变化为标志的中国第四纪地层对比表

随着新技术方法的不断引入和地层学多元划分理论的提出,除了传统的岩石地层、生物地层和年代地层,又开拓了地貌地层、磁性地层、土壤地层、同位素地层、事件地层和旋回地层等新的分支。高分辨率古气候研究的需要,促使我们去探索第四纪地层,特别是陆相地层新的划分方案。本文作者在各自对不同的成因类型的第四纪沉积物的研究中,都或多或少参照深海氧同位素阶段进行过地层的划分和对比的尝试,自然就产生了以氧同位素阶段为参照的划分和对比第四纪地层的设想。我们“抛砖引玉”,提出了中国第四纪ＭＩＳ地层表,只求“有”,尚不能求“准”,希望我们的工作能够推进我国第四纪地层的研究,对第四纪科学的发展作出贡献。     

Differentiations of geographic distribution and subsistence strategies between Tibetan and other major ethnic groups are determined by the physical environment in Hehuang Valley

The people of the Tibetan Plateau have received extensive attention from scholars because of their unique adaptability to the low temperature and anoxic environments. However, the Tibetan communities and their habitats in the low-altitude regions of the plateau have rarely been studied in a scientific manner. Based on the extraction of geographic information of 197 towns in the Hehuang Valley and on variance analysis, this study examines the habitats and subsistence strategies of the Tibetans and other major ethnic groups in the low-latitude region of the Tibetan Plateau. Our statistical results show that the annual average temperature of Tibetan habitats in the Hehuang Valley is relatively high. The relatively warm environment of the valley allows the Tibetans in that area to cultivate wheat and barley and raise cattle and sheep—a subsistence strategy significantly different from that of other Tibetans in the high-altitude regions in the Tibetan Plateau. In addition, the Tibetan communities in the Hehuang Valley include similar agri-pastoral ethnic groups (including Hui and Salar), both of which adopt similar subsistence strategies. The agricultural ethnic groups (Han and Tu) live in a relatively cool and humid environment facilitating agricultural production, while the agri-pastoral ethnic groups (Tibetan, Hui, and Salar) inhabit relatively warm and arid environment in the valley. Due to the lack of agricultural activities, agri-pastoral groups must also engage in animal husbandry to supplement their diet. In the Ando Tibetan region, the subsistence strategies of the ethnic groups are closely related to their physical environment.Those ethnic groups communicate among themselves, integrate, and influence each other, resulting in a diversified culture. This study proves that the habitat variation at a regional scale corresponds significantly to the variation of subsistence strategies. Our findings may further refine knowledge about the human-environmental relationships of Tibetans and lead future research towards using quantitative methods to analyse the intersection of physical environment and ethnic groups' distribution.     

The sorption behavior of DDT onto sediment in the presence of surfactant cetyltrimethylammonium bromide

The sorption behavior of p,p′- and o,p′-dichlorodiphenyltrichloroethane (DDT) in the presence of a cationic surfactant cetyltrimethylammonium bromide (CTAB) on sediment was studied. Batch experiments were carried out to investigate the kinetics and thermodynamics of the process. The kinetic behavior of these three chemicals on sediment was described by pseudo-second-order kinetic equations, and the isotherms followed the Freundlich model well. The presence of CTAB was able to remarkably accelerate and enhance the sorption of DDT, whereas DDT showed no effect on the sorption of CTAB in our considered concentration ranges. The thermodynamic parameters, such as standard enthalpy change (ΔH⁰), standard entropy change (ΔS⁰) and standard Gibbs free energy change (ΔG⁰) showed that the sorption process of p,p′- and o,p′-DDT was physical, spontaneous and exothermic, and the randomness at the solid-liquid interface increased during the process. In the presence of CTAB, the sorption of DDT showed significantly negative ΔG⁰ and ΔH⁰ values.