近30年来长江源区土地覆被变化特征分析

长江源区是我国重要的水源涵养地。本文利用20世纪70年代中后期、90年代初期、2004年和2008年共4期土地覆被数据,通过土地覆被转类途径与幅度、土地覆被状况指数和土地覆被转类指数,分析评价了长江源区近30年来土地覆被与生态状况的时空变化特征。结果表明：草地是长江源区主要的土地覆被类型,2008年草地面积占该区总面积的66.93%。在70年代中后期-90年代初期、90年代初期-2004年和2004-2008年的3个时段内,土地覆被状况指数变化率分别为-0.15、-0.24和0.01;土地覆被转类指数分别为-0.20、-0.66和0.08。近30年来,长江源区土地覆被和生态状况总体经历了变差-显著变差-略有好转的过程。2004-2008年,长江源区年平均温度比前期（70年代中后期-2004年）升高了0.57℃,年平均降水量比前期增加了17.63mm。区域气候变化有助于自然生态系统的恢复。后期生态保护与建设工程的实施,对植被恢复产生了一定的积极作用。     

Water temperature behaviour in the River Loire since 1976 and 1881

Analysis of monthly mean river temperatures, recorded on an hourly basis in the middle reaches of the Loire since 1976, allows reconstruction by multiple linear regression of the annual, spring and summer water temperatures from equivalent information on air temperatures and river discharge. Since 1881, the average annual and summer temperatures of the Loire have risen by approximately 0.8?°C, this increase accelerating since the late 1980s due to the rise in air temperature and also to lower discharge rates. In addition, the thermal regime in the Orleans to Blois reach is considerably affected by the inflow of groundwater from the Calcaires de Beauce aquifer, as shown by the summer energy balance. To cite this article: F. Moatar, J. Gailhard, C. R. Geoscience 338 (2006).     

澜沧江某电站右坝肩复杂岩体质量分类

笔者通过对澜沧江某电站右岸坝肩复杂岩体的成因进行分析,采用岩体质量指数Z并结合水利水电工程围岩分级和RMR分级等岩体分类方法对电站右岸坝肩的复杂岩体进行了综合分类。     

太阳黑子和ENSO对日本吉野川流域水文要素影响

剖析"太阳-气候-水资源"体系作用机制对区域水资源科学管理具有重要科学意义。利用相关分析、主成分分析和小波分析方法,探究太阳黑子运动和厄尔尼诺（ENSO）对日本吉野川流域降雨、地表径流和地下水位影响。研究结果表明:太阳黑子活动和ENSO对研究区域水文过程显著影响分别发生在11 a和2~7 a周期上;太阳黑子运动能量以ENSO为"媒介"作用于流域降水和河川径流,但对地下水位波动影响不明显;太阳黑子活动在不同时频域对研究区域水文过程产生"直接"和"间接"影响,太阳黑子的"直接"影响可能通过调制ENSO外的气候模态来实现,其"间接"作用则通过"ENSO-西太平洋副高-东亚环流-水汽运动"系统作用实现。     

Inter- and intra-annual trend analysis of water level and flow in the middle and lower reaches of the Ganjiang River,China

ABSTRACT

The Ganjiang River is the largest tributary of Poyang Lake in China, and its hydrological regime variation greatly affects the utilization of regional water resources and the ecological environment of the lake. In this study, a novel trend analysis method, the Moving Average over Shifting Horizon (MASH), was applied to investigate the inter- and intra-annual trends of flow and water level from 1976 to 2016 at the Xiajiang and the Waizhou hydrological stations in the Ganjiang River. The Significant Change Rate Method (SCRM) was proposed to determine the MASH averaging parameters. The trend analysis results show a statistically significant decrease in water level series throughout the year and the relationship of flow and water level have changed greatly at the Waizhou station. The sediment load reduction, large-scale sand mining and water level decrease of Poyang Lake are identified as the main causes for the water level decrease.     

东昆仑阿拉克湖地区第四纪水系演化过程及其趋势

根据第四系沉积物的沉积时代、沉积类型及盆山耦合与迁移规律,将东昆仑阿拉克湖地区第四纪水系变迁划分了4个阶段：早更新世小型内陆盆地无序水系阶段;中更新世冰川水系与东流水系阶段;晚更新世柴达木盆地内陆水系向南溯源侵蚀阶段;全新世黄河外泄水系形成与发展阶段。根据研究区及相邻地区黄河水系和柴达木盆地内陆水系的溯源侵蚀发展历史及趋势分析,认为研究区未来水系发展趋势不一定是加鲁河袭夺鄂陵湖、扎陵湖两湖及黄河水系,而可能是黄河加快下蚀作用和溯源侵蚀,鄂陵湖和扎陵湖将逐渐消失成为河流,黄河水系最终将袭夺柴达木内陆盆地水系。     

Assessment of the natural and anthropogenic sources of chemical elements in alluvial soils from the Drava River using multivariate statistical methods

The objectives of this study are as follows: (a) an assessment of the geochemical background signature of the Drava Valley before the industrial revolution; (b) an evaluation of anthropogenic geochemical influences on the alluvial plains and river terraces in the valley; and (c) a determination of the spatial distribution of trace elements in the alluvial soils of the Drava River downstream of the Austrian–Slovenian border to the confluence of Mura and Drava Rivers.     

基于碎屑锆石特征的雅鲁藏布江山南宽谷风成沙丘物源示踪

雅鲁藏布江河谷（尤其是"一江两河"区域）风沙化较为严重,制约了当地社会经济的可持续发展,追踪河谷风沙来源对当地风沙治理意义重大。本研究聚焦于拉萨贡嘎机场附近的山南宽谷风沙地貌,采集2个河沙、3个风成沙丘和1个坡积物样品,以及引用前人研究的2个河沙样品。基于碎屑锆石U-Pb年龄及微量元素地球化学特征,进行沙源示踪研究,旨在为当地风沙治理提供科学依据。对360颗锆石进行LA-ICP-MS U-Pb定年,获得322个谐和年龄。分析结果表明,河沙、风成沙丘及坡积物样品碎屑锆石U-Pb年龄分布特征高度相似,主要峰值与冈底斯岩浆弧新生代的两期岩浆活动一一对应;非矩阵多维标度统计技术（MDS）分析也证实了样品与冈底斯岩浆弧有良好的亲缘性;地球化学判别图解显示锆石具有亏损轻稀土元素、富集重稀土元素、明显正Ce异常和明显负Eu异常的特征,亦指示其岩浆成因,表明冈底斯岩浆弧为沙丘、河沙与坡积物中碎屑锆石的主要来源。依据不同类型样品碎屑锆石年龄对比以及锆石年龄相似程度对比,结果发现：1）雅鲁藏布江地区风沙地貌主要是由于枯水季河床水位下降,导致河岸和河漫滩出露地表,就地起沙吹扬到山坡上所形成;2）研究区河沙并非主要从上游搬运而来,更多是拉萨河搬运汇入的泥沙。依据沙源分析结果,欲解决河谷风沙化问题,首要应在河岸和河漫滩种植适宜当地气候的耐旱植物固定河床上的泥沙,这是最直接有效的手段。     

Contrasting origins of Cenozoic silicic volcanic rocks from the western Cordillera of the United States

Two fundamentally different types of silicic volcanic rocks formed during the Cenozoic of the western Cordillera of the United States. Large volumes of dacite and rhyolite, mostly ignimbrites, erupted in the Oligocene in what is now the Great Basin and contrast with rhyolites erupted along the Snake River Plain during the Late Cenozoic. The Great Basin dacites and rhyolites are generally calc-alkaline, magnesian, oxidized, wet, cool (<850°C), Sr-and Al-rich, and Fe-poor. These silicic rocks are interpreted to have been derived from mafic parent magmas generated by dehydration of oceanic lithosphere and melting in the mantle wedge above a subduction zone. Plagioclase fractionation was minimized by the high water fugacity and oxide precipitation was enhanced by high oxygen fugacity. This resulted in the formation of Si-, Al-, and Sr-rich differentiates with low Fe/Mg ratios, relatively low temperatures, and declining densities. Magma mixing, large proportions of crustal assimilation, and polybaric crystal fractionation were all important processes in generating this Oligocene suite. In contrast, most of the rhyolites of the Snake River Plain are alkaline to calc-alkaline, ferroan, reduced, dry, hot (830–1,050°C), Sr-and Al-poor, and Nb-and Fe-rich. They are part of a distinctly bimodal sequence with tholeiitic basalt. These characteristics were largely imposed by their derivation from parental basalt (with low fH₂O and low fO₂) which formed by partial melting in or above a mantle plume. The differences in intensive parameters caused early precipitation of plagioclase and retarded crystallization of Fe–Ti oxides. Fractionation led to higher density magmas and mid-crustal entrapment. Renewed intrusion of mafic magma caused partial melting of the intrusive complex. Varying degrees of partial melting, fractionation, and minor assimilation of older crust led to the array of rhyolite compositions. Only very small volumes of distinctive rhyolite were derived by fractional crystallization of Fe-rich intermediate magmas like those of the Craters of the Moon-Cedar Butte trend. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.