干涸尾闾湖盆区泥漠地表磨蚀释尘特征

沙粒的表面磨蚀效应是地表产尘、释尘的重要机制,针对干湖盆泥漠地表开展磨蚀释尘实验研究,对理解干湖盆地表风蚀过程及盐碱尘暴形成机理具有重要意义。对采自西居延海干涸湖盆泥漠地表土样进行室内磨蚀模拟实验,研究了不同粒级（细、中、粗）沙粒不同落沙角度（30°,45°,60°）的磨蚀效应。结果表明：（1）泥漠地表磨蚀实验中能够产生明显释尘效应的沙粒粒级阈值为中沙（0.25 mm<M_d<0.50 mm）;（2）磨蚀粒径粒级相同时,磨蚀角度会对泥漠地表磨蚀释尘速率产生影响,磨蚀量的角度排序为60°>30°>45°,但同一粒级3种角度下的磨蚀释尘率差异不显著。（3）磨蚀角度为45°时,计算了泥漠地表的质量磨蚀率与能量磨蚀率,其中中沙为0.04 g·kg^-1、0.43 g·J^-1,粗沙为0.08 g·kg^-1、0.74 g·J^-1,极粗沙为0.26 g·kg^-1、2.54 g·J^-1;在磨蚀沙粒粒级倍增而磨蚀角度不变情况下,泥漠地表磨蚀释尘率与能量磨蚀率未发生正比例线性增长变化。     

从城镇体系的演变看清代东北地区的土地开发

清代东北地区的土地开发与城镇体系演变是两个互相促进、互相作用的过程,东北地区州、道、府、县等各级民事行政管理机构是为了管理从事农业开发的汉民而设立的。从城镇体系演变及城镇密度空间变化过程来看清代东北的土地开发,得出结论:清代东北地区城镇体系的发展可区分出4次城镇设置的增长时期;清代城镇体系在空间上呈现出从南向北、从中间向东西两侧的阶段性扩张的特点。与此相对应,清代东北土地开发也经历了几次规模较大的浪潮并发生了垦殖界线的北移;重点开垦区域是沿今沈阳-吉林、长春-哈尔滨一线不断往北的,且自该线往东西两边扩展,体现出自然区位条件、地形因素及政策等对土地开发的限制和影响。     

聚四氟乙烯平板型气态膜回收淡盐水中氯气

本文以离子膜电解氯化钾制取碳酸钾工艺产生的淡盐水为原料,系统地研究了聚四氟乙烯平板型气态膜回收氯过程中膜性能和次氯酸钠水溶液的制备。初步研究表明,次氯酸钠含量大于100g/L,氢氧化钠有效利用率为90％;聚四氟乙烯膜有传质快、对离子截留性能好、使用寿命长等优点,在工业上有较好的应用前景。     

白令海峡治理的合作机制研究

近年来随着北极冰盖的融化,北极通航已成为可能,而白令海峡作为北极航道重要的出口/入口,其战略地位也将逐步显现并被各国关注。在讨论白令海峡的治理与合作时,首先要明确白令海峡是用于国际航行的海峡,而作为海峡沿岸国的美国和俄罗斯对于白令海峡的管控与合作将成为影响未来北极航行的重要因素。为同时保障海峡沿岸国与使用国的利益,可借鉴马六甲海峡的治理经验,在现有治理机制的基础上进一步深化海峡沿岸国与海峡使用国的合作机制。中国作为海峡使用国也有必要积极参与白令海峡的合作治理。     

基于贝叶斯层次时空模型的甘肃省土地利用程度演变分析

以甘肃省为例,在基于Google Earth Engine (GEE)平台实现1995年、2000年、2005年、2010年、2015年和2020年土地变化监测的基础上,利用贝叶斯层次时空模型(BHM)分析土地利用程度的时空变化特征。结果表明：① 研究期间内甘肃省土地利用程度呈增长趋势,其中1995―2000年和2010―2015年增长速度较明显;② 土地利用程度空间格局“东高西低”,热点区域主要分布在陇中、陇东和陇南地区;③ 土地利用程度局部变化呈现明显区域差异,整体表现为“东弱西强”,局部变化热点区域主要分布在河西地区;④ 影响土地利用程度变化的主要因素是经济规模和产业结构,其中经济因素影响程度最高。     

树轮稳定同位素记录:进展、问题及展望

树轮稳定同位素比率(δ13 C、δ18O 和δD)变化与树木生长季的气候和环境条件密切相关。控制实验表明, 树轮稳定同位素比率变化可较好地记录树木叶片气孔活动、水分来源、水分利用效率等相关信息, 已成为古气候和全球变化生态学研究的重要代用指标和手段之一。树轮稳定同位素记录能够较好地保留低频气候环境变化信息, 与年轮宽度相结合, 可有效地进行区域古气候重建和全球变化生态学方面的研究。文章综述了树轮稳定同位素的分馏机理及其发展, 系统阐述和评价了利用树轮稳定同位素指标进行古气候和古环境的相关研究成果, 并指出树轮稳定同位素研究在中国未来亟须着重发展的方向。     

Two new records of Pyramidellidae (Gastropoda, Heterobranchia) from China seas

This paper reports two species of the family Pyramidellidae (Gastropoda, Heterobranchia), Otopleura nitida (A. Adams, 1854) and Rugadentia manzakiana (Yokoyama, 1922). The former was from the South China Sea and the latter was from the Yellow Sea and East China Sea. The study was based on the collections deposited in the Marine Biological Museum, Chinese Academy of Sciences. This is for the first time that these species have been recorded in China seas. In the current contribution, we describe and illustrate these two species, and compare them with similar species.     

SST variations of the Kuroshio from AVHRR observation

1 INTRODUCTION The Kuroshio Current (KC), being the western boundary current in the North Pacific subtropical gyre, is the second strongest current in the world af- ter the Gulf Stream and is famous as a strong and fast flow. KC plays an important role in…     

Implications of diverse sedimentation patterns in Hala Lake, Qinghai Province, China for reconstructing Late Quaternary climate

Hala Lake is located in the Qilian Mountains, Qinghai Province, China, at 4,078?m a.s.l. Its sediments contain an archive of climate and hydrologic changes during the Late Quaternary, as it is located close to the area influenced by the East-Asian summer monsoon and westerly-driven air masses. Sedimentation patterns and depositional conditions within the lake were investigated using eight sediment cores from different water depths, and this information was used to evaluate the feasibility of using a single core to reconstruct past climate and hydrological conditions. Long core H7, from the center of the lake (65?m water depth) and core H8 from a western, near-shore location (20?m water depth), were compared in detail using sediment composition and geochemical data (X-ray fluorescence, loss-on-ignition and CNS analysis). Age models were constructed using 17 AMS radiocarbon dates and indicate negligible reservoir error for sediments from the lake center and?~1,000?year errors for the near-shore sediment core. Cores H1?CH5 and HHLS21-1 revealed a sediment succession from sand and silty clay to laminated clay on the southern side of the lake. Undisturbed, finely laminated sediments were found at water depths???15?m. Core H5 (2.5?m long), from 31?m water depth, yielded abundant green algal mats mixed with clayey lake deposits and was difficult to interpret. Algae occurred between 25 and 32?m water depth and influenced the dissolved oxygen content of the stratified lake. Comparison of cores H7 and H8 yielded prominent mismatches for different time periods, which may, in part, be attributed to internal lacustrine processes, independent of climate influence. We thus conclude that data from a single sediment core may lead to different climate inferences. Common shifts among proxy data, however, showed that major climate shifts, of regional to global significance, can be tracked and allow reconstruction of lake level changes over the last 24,000?years. Results indicate advance of glaciers into the lake basin during the LGM, at which time the lake experienced lowest levels, 25?C50?m below present stage. Stepwise refilling began at ca. 16 kyr BP and reached the ?25?m level during the B?lling/Aller?d warm phase, ca. 13.5 kyr BP. A desiccation episode falls within the Younger Dryas, followed by a substantial lake level rise during the first millennium of the Holocene, a result of climate warming, which promoted glacier melt. By ca. 7.6 kyr BP, the lake reached a stable high stand similar to the present level, which persisted until ca. 6 kyr BP. Disturbed sediments in core H7 indicate a single mass flow that was most likely triggered by a major seismic event?~8.5 kyr BP. Subsequent lake development remains unclear as a consequence of data mismatches, but may indicate a general trend to deteriorating conditions and lake level lowstands at ca. 5.0?C4.2, 2.0 and 0.5 kyr BP.