Temporal and spatial variations in the discharge and dissolved organic carbon of drip waters in Beijing Shihua Cave,China

To detect the causal relationship between cave drip waters and stalagmite laminae, which have been used as a climate change proxy, three drip sites in Beijing Shihua Cave were monitored for discharge and dissolved organic carbon (DOC). Drip discharges and DOC were determined at 0 to 14‐day intervals over the period 2004–2006. Drip discharges show two types of response to surface precipitation variations: (1) a rapid response; and (2) a time‐lagged response. Intra‐annual variability in drip discharge is significantly higher than inter‐annual variability. The content of DOC in all drip waters varies inter‐ and intra‐annually and has good correlation with drip water discharge at the rapid response sites. High DOC was observed in July and August in the three years observed. The flushing of soil organic matter is dependent upon the intensity of rain events. The DOC content of drip water increases sharply above a threshold rainfall intensity (>50 mm d^?1) and shows several pulses corresponding with intense rain events (>25 mm d^?1). The DOC content was lower and less variable during the dry period than during the rainy period. The shape of DOC peak also varies from year to year as it is influenced by the intensity and frequency of rainfall. The different drip sites show marked differences in DOC response, which are dominated by hydrological behaviour linked to the recharge of the soil and karst micro‐fissure/porosity network. The results explain why not all stalagmite laminae are consistent with climate changes and suggest that the structure of the rainy season events could be preserved in speleothems. Copyright © 2008 John Wiley & Sons, Ltd.     

爆炸应力波对新浇混凝土衬砌的影响研究

爆炸应力波作用下新浇混凝土衬砌的破坏模式及安全振动速度是水电、铁道工程隧洞建设中需要解决的重要问题。根据弹性P波及SV波在介质中的传播规律,讨论了P波及SV波在薄层混凝土衬砌中的传播及近似处理方法,依照莫尔-库仑准则、极限拉应力准则、极限拉应变准则,研究了爆炸应力波作用下新混凝土衬砌的破坏模式及安全振动速度。结果表明,入射应力波及衬砌中的折射波对衬砌的破坏作用最主要,折射波在衬砌内产生的反、折射波将降低衬砌中的应力,具有卸载效果;混凝土衬砌的安全振动速度随着龄期的增大而增大,P波入射时,安全振动速度随着入射角的增大而增大,入射角较大时,胶结面容易发生剪切破坏,较小时,容易发生拉伸破坏,SV波入射时,较小角度下容易发生剪切破坏,较大角度时容易发生拉伸破坏;围岩弹性模量越高,衬砌的安全振动速度越小。     

基于Duncan-Chang本构的非线性土压力模型

假设基坑工程中挡土结构的变形和土压力服从双曲线模型,类比Duncan-Chang本构建模思想,在前人关于基坑主动区和被动区变形假设的基础上,建立了可以考虑位移变化的非线性土压力模型。把非线性土压力模型和Duncan-Chang本构模型联系起来,使得本文非线性土压力模型参数确定有根据。把弹性地基梁模型和该非线性土压力联系起来,使得弹性抗力系数的概念更加明确。以m法为例,深入分析了m法的影响因素。      

闽西山区旅游开发与脆弱生态环境耦合发展机制研究之展望

深入研究闽西山区旅游开发与脆弱生态环境耦合发展机制,即通过建立山区生态脆弱性评价指标体系、研究脆弱生态环境与旅游开发耦合发展、构建闽西生态脆弱区旅游资源开发模式及建立旅游发展预警系统等措施来实现闽西山区旅游开发与脆弱生态环境保护的良性耦合。学术贡献主要体现在：理论层面上可以建立一种适用于山区型生态脆弱区生态环境与旅游开发协调发展的分析框架,在应用层面上实现旅游资源适度开发与生态环境有效保护,促进山区型生态脆弱区生态资源可持续发展。为实现研究目标,本研究从人地关系角度出发提出自上而下、自下而上相结合的技术路线。     

三江平原浓江河湿地生态廊道区及其周边春季鸟类多样性研究

浓江河湿地生态廊道是连接三江平原洪河国家级自然保护区湿地和三江国家级自然保护区湿地的生态廊道.2008年春季,对浓浓江河湿地江湿地生态廊道鸟类资源开展了调查研究.在研究区5种鸟类栖息生境共设立11个调查点,共记录有鸟类14目26科68种,3 220只.浓江河湿地生态廊道鸟类多样性指数(H')较高,生境主要以沼泽湿地为主,不同栖息生境中鸟类多样性指数表现为H'沼泽(1.260 1)>H'水域(1.248 8)>H'居民区(0.903 1)>H'农田(0.872 8)>H'林地(0.871 6);均匀性指数(E)表现为E水域(0.182 3)>E农田(0.164 6)>E林地(0.142 9)>E沼泽(0.110 5)>E居民区(0).维持浓江河湿地生态廊道沼泽和水域的面积对于保护该廊道的功能具有重要意义.     

生草覆盖和植物篱措施对红壤坡地土壤侵蚀调控效应研究

以安溪官桥为研究区,在已有研究工作的基础上采取野外调查与人工降雨野外模拟试验相结合的方法,研究了植被对山坡地土壤侵蚀的调控机理.研究表明,翻耕地在生草覆盖的条件下,产流量与径流系数均减少70%左右,平均入渗率提高3倍多.说明生草覆盖条件下大量的降雨以入渗的形式流入土壤中,且径流含沙量与产流产沙量均显著低于生草覆盖前,其中平均含沙量减少87.5%,产沙量减少97%.根据对野外试验小区的多年观察,说明植物篱具有缓解坡度、提高土壤抗冲性等明显的保水保土效益.因此,采取适当措施减少产流量以及提高降雨向土壤水分的转化率,均可有效减少坡地土壤流失量.     

基于投入产出理论的城市群产业空间联系

在对城市群空间联系研究成果回顾的基础上,通过引入感应系数和影响系数,构建度量两两城市之间产业联系强度的指数,通过强度大小确定城市群内部产业联系的主要方向和次要方向,即空间结构。根据该指数大小,认为在同一城市群范围内,该指数存在较大的差异,差异程度与城市群的发育程度以及节点的空间配置关系耦合度较高,表现出较强的自组织性;根据主要联系方向和次要方向在不同节点的配置关系,确立了网络密集型、结构分散型、聚核居中型和聚核偏离型4种空间结构类型。基于空间发展战略和规划导向,分析了产业空间联系结构的应用价值,进一步明确城市群内部的空间开发时序以及不同城市群在不同时期的开发方向与重点等。最后指出了本文研究的理论意义及未来研究的主要方向。     

S-wave velocity structure beneath Changbaishan volcano inferred from receiver function

The S wave velocity structure in Changbaishan volcanic region was obtained from teleseismic receiver func-tion modeling. The results show that there exist distinct low velocity layers in crust in volcano area. Beneath WQD station near to the Tianchi caldera the low velocity layer at 8 km depth is 20 km thick with the lowest S-wave velocity about 2.2 km/s. At EDO station located 50 km north of Tianchi caldera,no obvious crustal low velocity layer is detected. In the volcanic re-gion,the thickness of crustal ...     

“十五”宁夏区域前兆台网建设与系统集成

概述了“十五”宁夏前兆项目系统运行平台及软硬件配置情况。详细地论述了省级区域前兆台网的构架特点,及部署过程中的关键技术与解决方法。     

Modern pollen rain in the Lake Qinghai basin,China

Lake Qinghai is the largest inland brackish lake in China and lies within the NE Tibetan Plateau. Our study shows that pollen assemblages in each vegetation belt are significantly correlated with the vegetation types of this area. Among the herbaceous and shrubby pollen assemblages, Artemisia is over-represented, while Poaceae, Cyperaceae and Polygonaceae are under-represented. Artemisia/ Chenopodiaceae (A/C) ratios with the regional vegetation characteristic can be used as a proper index to reconstruct the...