地质雷达方法在上海市轨道交通明珠线工程中的应用

地质雷达方法在上海市轨道交通明珠线工程中的应用表明,此方法在探测地下障碍物中能依靠雷达图象识别其类型、材质、深度等,有利于快速、准确定位,有一定的优越性。     

欧亚大陆冬季雪深的时空演变特征及其影响因子分析

利用美国冰雪资料中心(National Snow and Ice Data Center)提供的前苏联1948~1994年逐日积雪深度资料,定义了冬季雪深增量的概念,探讨了欧亚大陆秋末雪深、冬季雪深、冬季雪深增量的时空演变规律,通过比较分析三者的异常变化特征,揭示了三者之间可能存在的联系。经验正交函数分解(EOF)结果表明:欧亚大陆冬季雪深、冬季雪深增量的第一模态的空间分布特征均为大致以50°N为界的南北反相变化,欧亚大陆北部的积雪深度和冬季雪深增量都呈现出一致性的变化趋势;两者对应的时间序列均反映了显著的年代际变化特征,且年代际转变均发生在20世纪70年代中期前后。第二模态则呈现出欧亚大陆东、西部反相的偶极型空间分布特征。进一步分析表明,欧亚大陆秋末雪深无论从空间分布还是时间演变来看与冬季雪深几乎不存在相关性。欧亚大陆冬季雪深变化主要是冬季雪深增量影响所致,与秋末雪深无关。     

柴达木河都兰区植被覆盖率变化特征

柴达木河都兰区位于青海柴达木盆地东南部,干旱少雨,生态环境脆弱。基于MODIS NDVI数据,应用遥感方法,对都兰区2000—2011年的植被覆盖率进行了计算,并分析了其影响因素。结果表明：研究区内裸土和低覆盖率植被的面积逐年减小,而较低覆盖率、中等覆盖率、较高覆盖率及高覆盖率植被的面积均逐年增加;研究区植被覆盖率与降水及相对湿度呈正相关关系,区域植被生长与地下水埋深的关系较为密切;宗加-诺木洪植被区的地下水埋深范围为0.7～3.5 m,在水埋深为1.7 m的地方,植被长势最好;当研究区的地下水水质矿化度小于3 g·L^-1时,植被发育较好。     

湖泊生态恢复的关键因子分析

中国是一个多湖泊的国家。由于经济快速发展及湖泊资源不合理的开发利用,中国湖泊的污染问题和生态系统退化相当普遍。特别是由于氮、磷等营养元素的富集造成的水体富营养化,导致蓝藻水华频繁发生,甚至出现了饮用水危机事件。由于缺乏基础理论的指导,中国湖泊富营养化治理曾经走过弯路。在没有实现控源截污的条件下,片面强调生态恢复来净化湖泊水环境,一度成为富营养化湖泊治理的主流思想。实际上,湖泊生态恢复是有条件的,而对这些条件的诊断和分析是开展湖泊生态恢复的前提和基础。通过对太湖水生植物分布及其影响因子分析,确定沉水植物恢复的核心条件是水下光照条件。水下光照条件受富营养水平、悬浮物浓度与水深等因子的影响。只有当一个水域的真光层深度接近水深的情况(比值>0.8),恢复水生植物才有可能。改善水下光照条件,包括降低水深,提高透明度,消除风浪等措施,实际上,都是增加真光层深度与水深的比值。在上述生态恢复条件不具备的情况下,湖泊治理与恢复的工作更多地应该聚焦在控源截污方面。这对中国湖泊污染治理与生态恢复具有普遍的意义。     

第四纪环境研究新理论

On the basis of extensive survey to the Quatemary paleosols, soils and weathering layers in the vast northern China and the Loess Plateau, we found some unusually special phenomena of chemical components such as unsuccessive illuvium, twin illuviums, unusually thick illuvium and multi-illuviums etc. According to the analysis on the content of CaCO3 and the data of penetrating experiment, a new theory of illuvial depth or removal depth of CaCO3 in weathering and leaching belt was constructed, which indicates that the time of CaCO3 removing to the illuvial depth is very short,and the effect of time factor on illuvial depth can be ignored. The theory can be taken as a credible foundation for studying many geological and geographical problems in weathering and leaching belt.When the illuvial depth of CaCO3 iS bigger than the thickness of developing belt of soil or paleosol, it can be determined that the paleosol has turned into weathering crust. When the illuvial depth of CaCO3 is bigger than the thickness of paleosol, paleosol is leaching moderately acid soil. When two, three layers or unusually thick CaCO3 illuviums exist in the same weathering section or at the bottom of the same paleosol, there were two or more periods forming paleosol and corresponding climatic stages at that time. On the basis of the equation of relationship between mean annual rainfall (y) and illuvial depth of CaCO3 (x) (y = 305.5x 168.5) determined in the paper, mean annual precipitation during the development of paleosol can be calculated.     

Re-evaluation of focal depths and source mechanisms of selected earthquakes in the Afar depression

We present a stepwise inversion procedure to assess the focal depth and model earthquake source complexity of seven moderate-sized earthquakes  (6.2 > M _w > 5.1)  that occurred in the Afar depression and the surrounding region. The Afar depression is a region of highly extended and intruded lithosphere, and zones of incipient seafloor spreading. A time-domain inversion of full moment tensor was performed to model direct P and SH waves of teleseismic data. Waveform inversion of the selected events estimated focal depths in the range of 17–22 km, deeper than previously published results. This suggests that the brittle–ductile transition zone beneath parts of the Afar depression extends more than 22 km. The effect of near-source velocity structure on the moment tensor elements was also investigated and was found to respond little to the models considered. Synthetic tests indicate that the size of the estimated, non-physical, non-isotropic source component is rather sensitive to incorrect depth estimation. The dominant double couple part of the moment tensor solutions for most of the events indicates that their occurrence is mainly due to shearing. Parameters associated with source directivity (rupture velocity and azimuth) were also investigated. Re-evaluation of the analysed events shows predominantly normal faulting consistent with the relative plate motions in the region.     

Assessing potential land suitable for surface irrigation using groundwater in Ethiopia

Although Ethiopia has abundant land for irrigation, only a fraction of its potential land is being utilized. This study evaluates suitability of lands for irrigation using groundwater in Ethiopia using GIS-based Multi-Criteria Evaluation (MCE) techniques in order to enhance the country's agricultural industry. Key factors that significantly affect irrigation suitability evaluated in this study include physical land features (land use, soil, and slope), climate (rainfall and evapotranspiration), and market access (proximity to roads and access to market). These factors were weighted using a pair-wise comparison matrix, then reclassified and overlaid to identify suitable areas for groundwater irrigation using a 1-km grid. Groundwater data from the British Geological Survey were used to estimate the groundwater potential, which indicates the corresponding irrigation potential for major crops. Results indicated that more than 6 million ha of land are suitable for irrigation in Ethiopia. A large portion of the irrigable land is located in the Abbay, Rift Valley, Omo Ghibe, and Awash River basins. These basins have access to shallow groundwater (i.e., depth of groundwater less than 20 m from the surface) making it easier to extract. The comparison between available groundwater and total crop water requirements indicate that groundwater alone may not be sufficient to supply all suitable land. The study estimates that only 8% of the suitable land can be irrigated with the available shallow groundwater. However, groundwater is a viable option for supplementing surface water resources for irrigation in several basins in the country.     

Effect of Ploughing Depth on the Growth and Yield of Heracleum candicans： a Threatened Medicinal Herb and a Less-explored Potential Crop of the Himalayan Region

This paper examines the effect of ploughing depths （A -- 60 cm, B -- 45 cm and C -- 30 cm） on the growth and yield of Heracleum candicans Wall （Apiaceae）, a threatened medicinal herb of the Himalayan region. This less-explored plant is being suggested as a potential crop for the mountain agriculture. The study was carried out in an orchard in Himachal Pradesh, India at 2500 m altitude, for two successive growth years. During the first year, all plants remained in juvenile state; in the second year, nearly 65 % plants produced flowers only under 60cm ploughing depth. Among its morphological traits, plant height, collar diameter and aboveground flesh weight were found to be strongly correlated （P 〈 0.01） with the belowground biomass during the first year （r =0.968, 0.925 and 0.973, respectively） and during the second year （r=0.945, 0.928 and 0.775, respectively）. Increase in the ploughing depth was significantly correlated （P〈0.01） with all growth parameters, including the belowground dry weight, marketable portion of the produce. The belowground biomass （commercial yield; 16.28 Qt/hec） at depth A was about 2.6 and 4.7 times higher than those recorded at depths B and C, respectively. The results clearly justify the importance of deep ploughing and this paper strongly recommends it for economically sustainable cropping.     

不同食物与放养水层对九孔鲍生长的影响

采用室内池子多层笼养殖方式 ,以加工海带、鲜江艹离 与 A,B2种片状饲料为饵料 ,试验了不同食物与不同放养水层对九孔鲍生长影响 ,结果表明 :( 1)从壳长增长上 ,海带与饲料 B近似 ,各为 11.3与 11.2 mm;其次为饲料 A,10 .2 mm;而江 艹离 最差 ,仅 7.7mm;( 2 )在体重增长上 ,以饲料 B最高 ,平均每只为 3.3g,其次为饲料 A与海带 ,平均每只 2 .9g,而江艹离 仅 1.8g;( 3)从试验期间所获体重增长比壳长增长看 ,两种饲料 ( B为 2 95,A为 2 84 mg/mm)均比两种海藻高 (海带为 2 57,江艹离 为 2 34mg/mm) ;( 4 )从垂直 11层笼子九孔鲍生长的比较 ,下层的好于上层 ,越是下层越好 ,投喂两种饲料在体重上差别更明显。