定量的穆斯堡尔谱学中比值C＝Ca／Cb的实验测定

按定量斯堡尔谱学公式：Sa/Sb=(Ca/Cb)(Na/Nb），若两类铁原子的浓度a和Nb是已知的，并通过实验测得强度Sa和Sb，即可求得它们的相对强度系数（Ca/Cb)。但实际上这种测量有很多困难。本文介绍在特殊条件下的若干测量结果。选用铁白云石、橄榄石、钙铁榴石和铁铝石四种矿物；它们的含铁量已知，且各自只含有一种价态的铁原子，各自的谱图中只出现一组四极矩双线，制备了混合吸收体，它们各自由上述四种矿物之中的两种组成，每种矿物对吸收体含铁量的贡献Na和Nb是已知的，并让Na/Nb≈1。若将Ca相对于铁白云石、钙铁榴石和铁铝榴石分别改写为Cakr, Cadd和Cakm，将Cb相对于橄榄石改写为Colv，所求得的结果是：Cadd/Colv=0.964(±0.025),Calm/Colv=0.874(±0.020),Cakr/Colv=0.828(±0.015），对这些结果与矿物结构之间的进行了讨论。     

三江源生态保护和建设一期工程生态成效评估

基于生态系统结构--服务动态过程趋势分析,针对生态保护与建设工程预期目标,构建了由生态系统结构,质量,服务及其变化因素构成的生态成效评估指标体系,研究发展野外观测,遥感监测和生态过程定量模拟一体化的监测评估技术体系,评估了三江源生态保护和建设一期工程的生态成效.结果表明:工程实施8年以来,三江源区宏观生态状况趋好但尚未达到1970s比较好的生态状况,草地持续退化趋势得到初步遏制但难以达到预期"草地植被盖度提高平均20%~40%"的目标,水体与湿地生态系统整体有所恢复,生态系统水源涵养和流域水供给能力提高,区域水源涵养量达到了增加13.20亿m³目标;重点工程区内生态恢复程度好于非工程区,除了气候影响以外,工程的实施对促进植被恢复具有明显而积极的作用;然而,草地退化局面没有获得根本性扭转,工程实施尚未遏制土壤水蚀增加趋势,一期工程局部性和初步性特点突显出三江源区生态保护任务的长期性和艰巨性.     

永久散射体雷达差分干涉反演矿区时序沉降场

针对永久散射体差分干涉测量(PSIn SAR)算法流程,发展了基于周期函数模型的空间维解缠方法,并将其应用于矿区时间序列地表变形反演。通过在研究区域内安装人工角反射器(CR),将CR点上计算所得的周期模型参数分量作为整个网络的约束,通过空间约束平差以实现空间维解缠。选取了河南省境内白沙水库附近的煤矿密集区为主要研究区域,采用周期函数模型对矿区线性及非线性形变分量进行模拟,反演了2007年2月—2010年2月的时间序列形变场,并采用研究区域内的水准实测数据作为外部验证数据。实验结果表明:白沙水库周围区域存在着较为明显的沉降,在煤矿分布区域内累积最大沉降量超过了10 cm。沉降区域内以线性沉降趋势为主,非线性沉降较为缓慢,仅在水库的西南方向较为明显。应用已有的水准点实测形变值对实验结果进行验证分析,结果表明该方法精度可达约±2.1 mm,证实了本文采用的方法在矿区地表时序形变反演中的可行性和可靠性,对预防过度采矿导致的矿区塌陷具重要现实意义。     

地下水水质评价与预测方法综述

近年来,地下水水质安全引起了社会广泛的关注,国内外学者开展了大量水质评价与预测研究,本文综合了当前几种广泛应用的水质评价与预测方法,对比了各自的适用性与局限性,展望了今后水质评价与预测发展的趋势,以期为地下水管理、开发利用提供参考依据。     

建筑结构基础隔震技术的研究和应用

本文介绍了建筑结构基础隔震基本原理、隔震系统分类、隔震技术进展、隔震设计一般流程、隔震相关专著、隔震规范和应用软件,并提出隔震技术推广中有待解决的几个问题。     

树轮记录的阿尼玛卿山区过去 830年夏半年最高温变化*

利用采自黄河源区阿尼玛卿山的祁连圆柏(Juniperus prezewalskii)样芯,采用国际规范的树轮学研究方法对所有树轮样芯进行了精确定年。针对各样芯不同的生长趋势分别采用负指数函数、线性函数和样条函数拟合与树龄有关的树木生长趋势。对个别在样芯中存在缺失段或缺失年轮过多难以准确判定缺失位置的样芯,采用"搭桥"的方法建立完整序列,最后用ARSTAN软件计算合成树轮宽度年表,最长序列为1532a,在满足复本要求的基础上建立了长度为830a的树轮宽度年表,并对年表的基本统计特征进行了分析。初步的分析结果表明该年表的年轮指数与研究区夏季温度成显著负相关,并在此基础上重建了研究区过去830年来夏半年(4~9月)平均最高温的变化。重建序列包含有大量的高频变化信息,又有十分显著的低频变化趋势。研究区在重建时段内经历了3个较为显著的降温期,其中1820s~1900s的降温趋势不同于该时期全球平均温度的升高趋势。另外,分析表明在重建时段内升温期较短,但是升温幅度大于降温幅度,迅速升温可能导致研究区严重干旱事件的发生。     

Reconstructed droughts for the southeastern Tibetan Plateau over the past 568 years and its linkages to the Pacific and Atlantic Ocean climate variability

We present a Palmer Drought Severity Index reconstruction (r = 0.61, P < 0.01) from 1440 to 2007 for the southeastern Tibetan Plateau, based on tree rings of the forest fir (Abies forrestii). Persistent decadal dry intervals were found in the 1440s–1460s, 1560s–1580s, 1700s, 1770s, 1810s, 1860s and 1980s, and the extreme wet epochs were the 1480s–1490s, 1510s–1520s, 1590s, 1610s–1630s, 1720s–1730s, 1800s, 1830s, 1870s, 1930s, 1950s and after the 1990s. Comparisons of our record with those identified in other moisture related reconstructions for nearby regions showed that our reconstructed droughts were relatively consistent with those found in other regions of Indochina, suggesting similar drought regimes. Spectral peaks of 2.3–5.5 years may be indicative of ENSO activity, as also suggested by negative correlations with SSTs in the eastern equatorial and southeastern Pacific Ocean. Significant multidecadal spectral peaks of 29.2–40.9 and 56.8–60.2 years were identified. As indicated by the spatial correlation patterns, the decadal-scale variability may be linked to SST variations in the northern Pacific and Atlantic Oceans.     

Drought reconstruction in the Qilian Mountains over the last two centuries and its implications for large-scale moisture patterns

We present a composite tree-ring chronology from two sites of Qilian Juniper(Sabina przewalskii)in the northwestern Qilian Mountains(QM),Northwestern China.Precipitation in June was found to be the main limiting factor for tree-growth.The tree rings are also significantly and positively correlated with June precipitation over large areas of the northern Tibetan Plateau(TP).The authors thus consider that the tree- ring based drought reconstruction from 1803–2006 is representative of a large area drought hist...     

Moisture variability across China and Mongolia: 1951–2005

Moisture variability across China and Mongolia (hereafter, CM) during 1951–2005 was investigated using the recently developed monthly Palmer Drought Severity Index (PDSI) dataset. In total there are 206 PDSI grid points across CM, based on a 2.5° × 2.5° gridding system. For CM as a whole a significant decreasing trend in mean moisture availability was observed during 1951–2005, but with strong decadal (17.1-year) and interannual (5.0-year, 3.2-year, 2.4–2.8 year) variations. The areas affected by moderate and severe moisture deficit over CM have increased significantly since the mid-1950s. In contrast, there is a significant decreasing trend for areas affected by moderate wetness since the mid-1950s, and no significant trend was found for the areas affected by severe wetness. Ten moisture-related spatial patterns were objectively defined for CM using rotated Empirical Orthogonal Function (REOF) analysis. These patterns are related to distinct geographical areas and are associated with distinct temporal variations. Four of these patterns, in Northeast China (NE), North China (NC), Central China (CC), and East China (EC), generally demonstrate a significant decreasing trend in moisture availability. Two patterns located in western areas of Northwest China (NW) and the Tibetan Plateau (TP) show a significant moisture increase, while four patterns in Mongolia (MN), far western China (FW), South China (SC), and Southwest China (SW) do not have significant moisture trends during 1951–2005. Based on REOF results we propose that CM should be divided into ten coherent moisture divisions. Moisture variations within each division are generally coherent, but may show either similar or contrasting covariability with adjacent divisions.     

满洲里南部白音高老组流纹岩锆石U-Pb定年及岩石成因

满洲里南部白音高老组火山岩主要由流纹岩组成,含少量珍珠岩和流纹质凝灰岩。LA-ICPMS锆石U-Pb定年结果显示,流纹岩形成于141~139Ma的早白垩世早期。岩石地球化学研究表明,火山岩具有高硅富碱、贫钙镁和高FeO^T/MgO比值的特征; 稀土丰度总量较高(∑REE介于103×10^-6~488×10^-6),轻重稀土分馏明显［(La/ Yb)_N=4.12~30.94)］,Eu负异常显著(δEu=0.12~0.46); 微量元素以富集Rb、Th、U、K,强烈亏损Ba、Sr、P、Ti,中等亏损Nb、Ta和高Ga/Al值为特征,与A-型花岗岩特征相似。锆石¹⁷⁶Hf/¹⁷⁷Hf比值介于0.282785~0.282970之间,ε_Hf(t)值均为正值,介于3.78~9.98之间。流纹岩岩浆来源于斜长石稳定区玄武质下地壳物质的部分熔融,形成于非造山板内伸展构造环境。