Short term fluctuations in dissolved organic matter concentrations in streamflow draining a forested watershed and their relation to the catchment budget     

I. D. L. Foster  I. C. Grieve 《地球表面变化过程与地形》1982,7(5):417-425

Dissolved organic matter (DOM) concentrations in throughfall, throughflow, and runoff were recorded in a small (95 ha) woodland catchment in North Warwickshire for a period of eight weeks following a prolonged dry spell. DOM is shown to be positively related to stream discharge over the sampling period, although distinctive flushing effects were identified. The net contribution of DOM to total dissolved solids load carried in the river was only 2.4 per cent, and represented significantly less than published carbon losses by mineralization of soil organic matter. Throughfall inputs were some 100 times higher than streamflow outputs from the catchment.  相似文献   

基于松弛迭代的快速路网平衡网格化算法     

陈云 《测绘与空间地理信息》2014,(5):103-106

网格化划分算法是一种道路数据预处理方法,但网格剖分均衡度和耗时之间存在矛盾。为了解决此矛盾,本文借鉴了平衡二叉树的思想,基于松弛迭代方法,动态自适应确定松弛因子,建立了一个数学模型,提出了一种将道路路网快速平衡网格化划分的算法。文章实现了算法并在实际数据中进行测试,验证了算法的可行性和模型的正确性,同时也验证了该方法的有效性。  相似文献   

To Decipher the Ocean Carbon Sink Through Interdisciplinarity and the Integration of the Past and Present     

Jiao Nianzhi  Zhang Chuanlun  Xie Shucheng  Liu Jihua  Zhang Fei 《地球科学进展》2014,29(11):1294-1297

The ocean is the world’s largest active carbon pool and buffers global climate change. Current scientific research focuses on ocean carbon cycling and carbon sequestration mechanisms. The new cognition can be successfully reached only through interdisciplinary and integrative studies of the past and present oceans.  相似文献   

平衡剖面技术研究进展综述     

卓鱼周 《地下水》2014,(6)

平衡剖面技术是地质学研究中的一种重要方法,其研究领域涉及地质学的方方面面。通过对国内外大量资料的调研,论述平衡剖面在盐构造恢复、海底斜坡构造恢复及在强烈挤压区中的应用等方面的最新进展。从地震观点与平衡观点的不统一性及平衡剖面的精度问题讨论该技术的不足。认为平衡剖面技术在处理复杂地质问题方面还有待完善。随着地质资料精度的提高,该技术必将有更加广阔的应用前景。  相似文献   

龙凤山气田易漏失井固井工艺技术研究与应用          下载免费PDF全文

马艳超 《探矿工程》2017,44(6):58-61

龙凤山气田属于典型的裂缝性储层,钻井过程中漏失问题突出。该气田地层压力系数低、气层活跃、井壁稳定性差,固井难度较大。针对本区块特点,强化固井工艺措施,做好钻完井过程的防漏、承压堵漏工作,优选完井方法,采用变排量顶替工艺技术,开展低密度水泥浆体系优选研究,合理设计浆柱结构,有效地解决了固井过程中的漏失和候凝期间气窜等问题,保证了固井质量,实现了油层的有效封固,现场应用效果良好。  相似文献   

Characterization of Mediterranean magnetotactic bacteria     

Lefèvre Christopher 《中国海洋大学学报(英文版)》2007,6(4):355-359

Magnetotactic bacteria are a diverse group of motile prokaryotes that are ubiquitous in aquatic habitats and cosmopolitan in distribution. In this study, we collected magnetotactic bacteria from the Mediterranean Sea. A remarkable diversity of morphotypes was observed, including multicellular types that seemed to differ from those previously found in North and South America. Another interesting organism was one with magnetosomes arranged in a six-stranded bundle which occupied one third of the cell width. The magnetosome bundle was evident even under optic microscopy. These cells were connected together and swam as a linear entire unit. Magnetosomes did not always align up to form a straight linear chain. A chain composed of rectangle magnetosomes bent at a posi- tion with an oval crystal. High resolution transmission electron microscopy analysis of the crystal at the pivotal position suggested uncompleted formation of the crystal. This is the first report of Mediterranean magnetotactic bacteria, which should be useful for studies of biogeochemical cycling and geohistory of the Mediterranean Sea.  相似文献   

金属稳定同位素示踪俯冲带挥发分循环SCIEI北大核心CSCD          下载免费PDF全文

刘盛遨 《岩石学报》2022,38(5):1512-1522

俯冲带挥发分的循环不仅深刻影响着地球各圈层之间的相互作用,而且在成矿金属元素迁移-富集以及全球气候变化等重要地质和环境过程中扮演着重要的角色。近年来,金属稳定同位素示踪俯冲带挥发分循环受到了广泛关注,取得了众多进展,但大多针对单个挥发性元素开展某个特定金属同位素的示踪研究。本文根据不同金属元素的地球化学性质差异及其与多种挥发分之间的结合形式,系统归纳了金属稳定同位素在示踪俯冲带不同挥发分循环方面的特点。整体上讲,镁和锌同位素体系示踪俯冲带碳循环最为有效;锂、镁、钾、钡、钼等金属同位素体系在示踪俯冲带水(流体)循环方面则具有各自的特点;锌同位素在示踪俯冲带硫循环方面有巨大潜力;铬同位素示踪俯冲带氯循环有独特优势;铁、铬、铜等变价金属同位素体系对挥发分的氧化还原状态较为敏感,有望示踪俯冲带氧循环。这些同位素体系对理解俯冲带挥发分循环提供了全新的视角,有望成为未来地球系统科学的重要研究方向。  相似文献   

The impacts of the district-level administrative restructuring on urban polycentricity and balanced regional development北大核心CSCD     

Chen Y.  Yu P.  Wang L.  Chen Y. 《地理科学进展》2023,(11):2084-2098

Administrative division adjustment as an institutional support for spatial governance is an important measure to optimize resource allocation, and it has profound effects on promoting balanced regional development. Based on the panel data of 272 cities in China from 2013 to 2021, this study used the spatial difference-in-differences method to explore the impact of district-level administrative restructuring, a special type of administrative division adjustment, on balanced regional development, and further analyzed the mediation mechanism of urban morphological polycentricity. The results show that district-level administrative restructuring is not only beneficial to promoting balanced regional development in local regions, but also has positive spatial spillover effects on neighboring regions. Mechanism analysis show that under the background of administrative division adjustment, urban form is an important driving factor for balanced regional development. Specifically, district-level administrative restructuring can reduce regional development inequality by improving the level of urban morphological polycentricity. Heterogeneity analysis show that the impact of district-level administrative restructuring on balanced regional development varies across regions. Compared to the western region, the positive effects of such restructuring on balanced regional development are more significant in the eastern and central regions. The restructuring has significant promotional effects in large cities and medium-sized cities, while the effects in mega-cities, super-large cities, and small cities are not significant. In the future, we should prudently carry out administrative division adjustment and urban spatial transformation according to the development conditions of different cities, and promote the construction of urban polycentricity by district-level administrative restructuring according to local conditions, in order to promote balanced regional development. © 2023, Editorial office of PROGRESS IN GEOGRAPHY. All rights reserved.  相似文献