Impact of land use change on groundwater recharge in Guishui River Basin,China

It is important to understand how land use change impacts groundwater recharge,especially for regions that are undergoing rapid urbanization and there is limited surface water.In this study,the hydrological processes and re-charge ability of various land use types in Guishui River Basin,China(in Beijing Municipality) were analyzed.The impact of land use change was investigated based on water balance modeling,WetSpass and GIS.The results indicate that groundwater recharge accounts for only 21.16% of the precipitation,while 72.54% is lost in the form of evapotranspiration.The annual-lumped groundwater recharge rate decreases in the order of cropland,grassland,urban land,and forest.Land use change has resulted in a decrease of 4 × 106 m3 of yearly groundwater recharge in the study area,with a spatially averaged rate of 100.48 mm/yr and 98.41 mm/yr in 1980 and 2005,respectively.This variation has primarily come from an increase of urban area and rural settlements,as well as a decrease of cropland.     

MOR型蛇绿岩中地幔橄榄岩的地质特征

地幔橄榄岩是指来自陆下、弧下或洋脊下的岩石圈地幔岩,通常通过构造侵位(冷侵位)的方式存在于造山带中,如造山带橄榄岩、蛇绿岩中的橄榄岩以及火山岩中的地幔橄榄岩等。本文选取了4个具有MOR型属性的蛇绿岩中地幔橄榄岩体,对比研究了其与深海橄榄岩在岩石学、地球化学、同位素地球化学和岩石成因等方面的特征,认为与深海橄榄岩性质的综合对比是识别MOR型蛇绿岩中地幔橄榄岩的有效方法之一,同时在蛇绿岩的分类中具有较好的参考价值。     

西双版纳雾在减少

利用西双版纳４０年雾的资料，揭示了西双版纳４０年雾日，雾时和雾量正在迅速减少。例如景洪市１９５４－１９６０年的年平均雾时高达８５８．０１小时，而１９９１－１９９４年仅为２１３．５６小时。雾减少的直接原因是相对湿度的降低，而相对湿度的降低是由于气温升高和降水量的减少。     

Occurrence and characteristics of sporadic sodium layer observed by lidar at a mid-latitude location

Na lidar observations of SSL during the past 5 years at a mid-latitude location (Wuhan, China, 31°N, 114°E) are reported in this paper. From 26 SSL events detected in about 230 h of observation, an SSL occurrence rate of 1 event/9 h at our location was obtained. This result, combined with that reported by Nagasawa and Abo (Geophys. Res. Lett. 22 (1995) 263) at Tokyo, Japan, reveals that the SSL occurrence can be relatively frequent at some mid-latitude locations. The statistical analyses of main parameters for the 26 SSL events were made, and the results were compared with those previously reported. By examining the corresponding data from a nearby ionosonde, it was found that there was a fairly good correlation between SSL and Es. Of the 18 pairs of SSL and Es events checked, 15 of SSL were accompanied by Es, and 8 pairs of them were correlated within 1 h in time and within 5 km in altitude. From the analyses of observed perturbations during SSL development, the role of dynamic processes of atmosphere in the SSL formations were emphasized.     

Changes of Warmer Winter and Winter Temperature over China During 1956-2005

 A reasonable warmer winter index (IWWI) in the framework of the three equiprobability categories (i.e. warmer, normal and colder categories) is proposed based on the winter temperature data observed at 565 stations in China during 1956-2005, where IWWI is defined as the ratio of the station number of warmer category over the total number of stations. The results suggest that the trend of IWWI was consistent with that of the winter temperature on decadal time scale, and their rates of change were 10%/10 a and 0.4 ℃/10 a, respectively. It is found that only 13 warmer winter events in total were detected by IWWI over the past 50 years, and 85% of them occurred after 1986.     

中国西部地震动衰减关系的适用性分析——以部分新疆地震为例

本文利用新疆地区丰富的烈度等震线资料和1985年乌恰7.1级地震的余震、1997伽师4次6级地震和2005年乌什6.2级地震的加速度记录,对中国西部地震烈度和地震动反应谱衰减关系的适用性进行了分析.结果表明,中国西部地震动衰减关系对新疆地区的适用性较好.其中加速度反应谱的相关系数达到0.94.     

First record of contourites from Lower Devonian Liptrap Formation in southeast Australia

Typical contourite deposits associated with submarine turbidite fan deposits are recognized for the first time from the Lower Devonian Liptrap Formation at Cape Liatrap, Victoria in southeast Australia. The contourites are well integrated within the turbidite fan deposits and are characterized by thin (5-8 cm), lenticular, well-sorted coarse-grained siltstones to fine-grained sandstones with current-ripples and cross beddings. The palaeocurrent directions of the turbidite fan and contourites are perpendicular to each other, with the former directed generally westward while the latter varying from 165° to 190° southward. In view of the facies types and architecture, we suggest that the turbidite fan was developed at the base of a westward inclined palaeo-slope, at the front of which the contourites were deposited as a result of southward flowing deep-sea contour (geostrophic) currents. The depositional setting inter- preted for the Liptrap Formation thus may provide a provisional model for the Lower Devonian conti- nental slope and abyssal basin environment in the southeastern part of the Melbourne Trough.     

The components and carbon isotope of the gases in inclusions in reservoir layers of Upper Paleozoic gas pools in the Ordos Basin,China

The components and carbon isotope of gases in inclusions are one of the most important geochemical indexes for gas pools. The analysis results of the components and carbon isotope of gases from inclusions in reservoir layers of Upper Palaeozoic gas pools in the Ordos Basin show that most inclusions grown in reservoir sandstone are primary inclusions. There is only a little difference about the components and carbon isotope between the well gases and the secondary inclusions gases. This indicated that the epigenetic change of gas pools is little. This difference between the well gases and the secondary inclusions gases is caused by two reasons: (i) The well gases come from several disconnected sand bodies buried in a segment of depth, while the inclusion gases come from a point of depth. (ii) The secondary inclusions trapped the gases generated in the former stage of source rock gas generation, and the well gases are the mixed gases generated in all the stages. It is irresponsible to reconstruct the palaeo-temperature and palaeo-pressure under which the gas pool formed using carbon dioxide inclusions.     

羌塘中央隆起带深部结构特征研究及其意义

羌塘含油气盆地是我国境内最大的中新生代海相沉积盆地.羌塘地体内的中央隆起将盆地分为南北两个盆地.中央隆起带构造属性认识存在两种截然不同的分歧,一是伸展环境下形成,整个羌塘盆地有着同一的基底.而另一认识其是一古特提斯缝合带,其两侧盆地具有不同的演化机制.调查羌塘中央隆起的深部结构特征及其与南北两侧的盆地间的构造关系是认识羌塘盆地基底性质及其油气远景之关键科学问题.尽管羌塘地体在青藏高原形成演化过程中遭到了强烈改造,但在收集并分析已有地球物理资料基础上认为其深部结构仍有可能被完整保存.因此,利用密集宽频带流动台网观测,获取其深部结构,进而研究其与两侧盆地关系,是当前羌塘含油气盆地研究之重要突破口,同时该项研究符合我国当前国家油气资源战略评估政策.