Is Precipitation the Dominant Controlling Factor of High Inorganic Nitrogen Content in the Changjiang River and Its Mouth？   总被引：1，自引：1，他引：0  

沈志良 《中国海洋湖沼学报》2003,21(4):368-376

The main reasons for the high content of inorganic N and its increase by several times in the Changjiang River and its mouth during the last 40 years were analysed in this work. The inorganic N in precipitation in the Changjiang River catchment mainly comes from gaseous loss of fertilizer N, N resulting from the increases of population and livestock, and from high temperature combustions of fossil fuels. N from precipitation is the first N source in the Changjiang River water and the only direct cause of high content of inorganic N in the Changjiang River and its mouth. The lost N in gaseous form and from agriculture non-point sources fertilizer comprised about 60% of annual consumption of fertilizer N in the Changjiang River catchment and were key factors controlling the high content of inorganic N in the Changjiang River mouth. The fate of the N in precipitation and other N sources in the Changjiang River catchment are also discussed in this paper.  相似文献   

黑龙江省与呼伦贝尔盟土地类型的划分及其分布规律   总被引：1，自引：0，他引：1  

赵松乔  戴旭  申元村  杨柳林 《地理研究》1982,1(1):49-57

本文就土地研究的几个主要概念,即土地、土地分类、土地分级作了简要讨论,并结合黑龙江省及呼伦贝尔盟的具体条件,对为农、林、牧业服务的土地分类原则进行了初步探讨,还拟订了该区土地分级系统——土地类和土地型,及适合于大比例尺制图的土地组。在此基础上,将全区分为18个土地类、71个土地型。文章还从水平带性、垂直带性和土地结构三个方面,介绍了该区土地类型分布的一般规律。  相似文献   

北京零售业的空间分布及影响因素     

李哲  申玉铭 《地理教学》2021,(2):4-9

零售业是生活性服务业的重要组成部分,传统零售业通常通过零售商业网点形式展开。零售商业网点具有数量多、分布广、差异大等特点,其区位选择不仅影响居民的生活品质,也关乎商业网点空间布局的合理性。北京中心城区的零售业整体及其各细分行业均呈现出显著的空间集聚态势,集聚中心主要沿长安街及其延长线分布。影响零售业的区位选择因素包括交通通达性、地价成本、消费市场规模、消费偏好、政策引导、城市商业发展历史等。近年来,随着零售业与互联网的深度融合,零售业区位选择的影响因素及其作用方式不断发生变化,需要更多关注“新零售时代”对零售业空间布局的影响。  相似文献   

Urban planning construction land standard and its revision based on climate and topography in China     

XU Yong  ZHAO Shen  FAN Jie 《地理学报(英文版)》2021,31(4):603-620

Urban planning construction land standard is the technical specification for scientifically allocating various types of urban construction land, and it is the basis for drawing up and revising the overall urban planning scheme. Considering China's current urban planning construction land standard, many problems exist, such as the gap in the land use control threshold, the lack of regional differences in the climate revision, and failing to consider the topographic factors. To resolve these problems, this study proposed a step-by-step process framework and quantitative calculation method for the establishment and revision of standards in accordance with the principle of Total-Structure control. By setting the conditions, a universal basic standard for construction land was established. Quantitative analysis was then conducted on the relationship between the basic standard and the selected key indicators, such as urban population size, sunshine spacing coefficient, the width of river valleys or inter-montane basins, and terrain slope, among others. Finally, revised standards were formed for climate conditions, topography, and geomorphologic conditions, which were matched with the basic standards. The key results are three-fold:(1) The per capita construction land standard of 95 m~2/person can be used as the total indicator of China's urban planning basic standard, and the corresponding per capita single construction land comprises 32.50% of residential land, 7.42% of public management and public service land, 22.50% of industrial land, 17.50% of transportation facilities, 12.50% of green space, and 7.58% of other land-use types. The results of the revision of the urban population size indicate that the difference in population size has little effect on the total amount of per capita construction land.(2) The climate revision results of per capita residential land and per capita construction land in major cities reveal that the revised climate value varies greatly between north and south China. The revised climate values of the per capita area of construction land vary by latitude as follows: the value at 20°N is 93 m~2/person, the value at 30°N is 97 m~2/person, the value at 40°N is 103 m~2/person, and the value at 50°N is 115 m~2/person. The basic standard land value of 95 m~2/person is generally distributed across the Xiamen-Guilin-Kunming line.(3) The cities located in mountainous areas, hilly valleys, or inter-montane basins can reduce the allocation of community parks and comprehensive parks when the average width of an existing river valley or inter-montane basin is less than 2 km. When the average width of the valley or inter-montane basin is between 2 km to 4 km, the allocation of the comprehensive parks can be reduced. The revised results of per capita sloping construction land reveal that the terrain slope greatly affects the revised value of per capita construction land. Specifically, the revised value at 3° is 3.68% higher than the basic standard value, and the increase rates at 8°, 15°, and 25° are 11.25%, 26.49%, and 68.47%, respectively.  相似文献   

试论国外河流地貌学的进展   总被引：1，自引：0，他引：1  

沈玉昌  蔡强国 《地理研究》1985,4(2):79-88

本文分四个阶段论述国外河流地貌学研究的发展,阐述了现代河流地貌学在一些领域中取得的成就,以及研究方法和技术的进展。  相似文献   

论Eppley PIR精密红外辐射仪的测量精度   总被引：1，自引：0，他引：1  

江灏  沈志宝 《高原气象》1992,(4)

本文依据红外辐射表(PIR)的结构、性能和工作原理讨论了测量精度及有关影响因素,比较了粗测和精测两种方法的特点,在此基础上提出了各测量方法的适用范围和精度范围以及提高测量精度的措施,同时也给出了一些特定场合下的测量实例及提高测量精度的具体方法。分析表明:精测方法具有很好的测量精度以及很强的环境适应性。粗测在限定的温度范围内具有测量简单、换算方便、易于实现自动化等优点,精度尚能满足一般要求,但在限定的温度范围以外,测量精度急剧恶化。在影响测量精度的各因素中以温度响应中表体热辐射测量的影响最大,在粗测方法中表内电池的性能与测量精度关系重大。强烈日射对测量精度有一定影响,经订正后可基本消除。  相似文献   

全球不同构造环境蛇纹岩全岩和矿物微量元素组成及非传统稳定同位素(Fe- Zn- Cu同位素)特征     

杨凯  戴紧根  沈洁  张文仓  赵玲玲 《地质学报》2022,96(12):4149-4166

蛇纹岩对地球深部和浅部的元素循环以及氧化还原状态调节具有非常重要的作用。蛇纹岩中的流体活动性元素(fluid- mobile element, FME)是揭示地幔岩石水化、脱水以及元素循环的关键。本文系统收集和分析了前人报道的不同构造环境的蛇纹岩矿物化学、全岩微量元素和非传统稳定同位素(Fe、Zn、Cu)的组成特征，试图从多个角度总结蛇纹岩脱水过程的元素迁移规律及流体性质。蛇纹岩主要矿物蛇纹石微量元素含量具有以下主要特征：① 不同变质程度的蛇纹岩中的蛇纹石既包含轻稀土元素(light rare earth element, LREE)富集，又包含LREE亏损的特征；② 纤蛇纹石的REE和微量元素分布在利蛇纹石和叶蛇纹石的范围内，利蛇纹石重稀土元素(heavy rare earth element, HREE)整体上略高于叶蛇纹石且更加富集FME；③ 通过中度不相容元素与REE含量相结合，能够较好地区分橄榄石和辉石蛇纹石化所形成的蛇纹石，即辉石形成的蛇纹石富集相容元素(如Sc、Zn、Cr、Y和Ti等)并具有较高的HREE，而橄榄石形成的蛇纹石则表现为平坦且整体较低的REE分布型式。在蛇纹岩全岩微量元素和稀土元素(rare earth element, REE)含量方面，不同构造环境的蛇纹岩具有较大范围的重叠，但也有一定的差异：① 慢速扩张的印度洋中脊蛇纹岩REE和微量元素含量要整体高于快速扩张的大西洋中脊和太平洋中脊的蛇纹岩；② 马里亚纳蛇纹岩泥相比于蛇纹岩和蛇纹石化纯橄岩具有更高的REE和微量元素，而蛇纹石化纯橄岩相比于蛇纹岩则具有相对低的REE及流体不活动性元素含量。因此，利用微量元素的含量在区分不同环境的蛇纹岩方面存在一定的困难。但是，碱金属元素与U元素含量及其相应的比值，则可以较明显区分出大洋蛇纹岩和弧前蛇纹岩。目前已发表的蛇纹岩Fe、Zn、Cu同位素数据表明：① 蛇绿岩中的蛇纹岩Fe和Zn同位素的分馏与其变质程度密切相关。蛇纹岩在进变质过程中δ 56Fe值与Fe 3+/∑Fe值呈负相关，而Zn含量和δ 66Zn值则呈现正相关，表明蛇纹岩变质脱水能够释放氧化性流体；② 与橄榄岩相比，蛇纹岩具有明显低的δ 65Cu值，表明橄榄岩蛇纹石化过程中存在氧化性流体的加入。蛇纹岩Fe、Zn、Cu同位素在示踪流体性质和氧化还原状态方面有很大潜力，对壳幔系统的化学循环具有重要意义。  相似文献   

青藏高原东南缘次林错岩体晚白垩世- 早新生代快速剥蚀     

沈续文  沈晓明  刘静  曾令森  杨超群  葛玉魁  邢宇堃  曾宪阳  王子君  李云帅  李金阳 《地质学报》2022,96(10):3332-3344

青藏高原东南缘是研究构造、地貌演化和气候变化相互作用的理想场所，前人研究主要揭示了晚始新世—早中新世和晚中新世以来的快速剥蚀事件，缺乏晚白垩世—早新生代时期地貌演化过程的研究。次林错花岗岩已有的低温热年代学数据覆盖了整个新生代时期，为探索该区域新生代早期的剥露演化历史提供了重要资料。该岩体新生代早期冷却事件是岩浆冷却单一作用的结果，还是受快速剥蚀作用的影响，目前仍然存疑，需要定量研究。因此，本文结合已有的岩石地化和年代学数据，对次林错花岗岩开展了锆石饱和温度和一维岩浆冷却模拟研究。锆石饱和温度计算结果表明次林错花岗岩的岩浆结晶温度介于647~705℃之间，属低温花岗岩。一维岩浆冷却模拟结果显示岩体侵位时的最小围岩温度为160~120℃，对应深度约为3. 7~5. 0 km。结合锆石和磷灰石(U- Th)/He年代学数据，本文认为该岩体在晚白垩世—早新生代时期(67~40 Ma)经历了一期剥蚀量至少为2 km的快速剥蚀事件。已发表成果的综合分析表明，此次快速剥露事件可能是整个青藏高原地区广泛存在的构造剥蚀事件，新特提斯洋的俯冲闭合与印亚板块的初始碰撞可能是触发此次大规模区域剥蚀的主要原因  相似文献   

中国南部二叠、三叠纪“混生生物群”及二叠、三叠系界线     

何锡麟  沈树忠 《吉林大学学报(地球科学版)》1991,(2)

本文系统描述了中国南部二叠、三叠纪“混生生物群”。根据笔者的统计,目前巳经发现有“二叠纪型”分子36属53种与三叠纪菊石、双壳类、牙形剌共生。 笔者认为中国南部可以以牙形剌Anchignathodus parvus 的出现作为三叠系的底界,双壳类Pteria ussurica variabilis,菊石 Hypophiceras的出现可以作为三叠系开始的辅助标志。文中还将这一界线与世界上其它地区的二叠、三叠系界线进行了对比。  相似文献   

Increasing critical sensitivity of the Load/Unload Response Ratio before large earthquakes with identified stress accumulation pattern   总被引：2，自引：0，他引：2  

Huai-zhong Yu  Zheng-kang Shen  Yong-ge Wan  Qing-yong Zhu  Xiang-chu Yin   《Tectonophysics》2006,428(1-4):87-94

The Load/Unload Response Ratio (LURR) method is proposed for short-to-intermediate-term earthquake prediction [Yin, X.C., Chen, X.Z., Song, Z.P., Yin, C., 1995. A New Approach to Earthquake Prediction — The Load/Unload Response Ratio (LURR) Theory, Pure Appl. Geophys., 145, 701–715]. This method is based on measuring the ratio between Benioff strains released during the time periods of loading and unloading, corresponding to the Coulomb Failure Stress change induced by Earth tides on optimally oriented faults. According to the method, the LURR time series usually climb to an anomalously high peak prior to occurrence of a large earthquake. Previous studies have indicated that the size of critical seismogenic region selected for LURR measurements has great influence on the evaluation of LURR. In this study, we replace the circular region usually adopted in LURR practice with an area within which the tectonic stress change would mostly affect the Coulomb stress on a potential seismogenic fault of a future event. The Coulomb stress change before a hypothetical earthquake is calculated based on a simple back-slip dislocation model of the event. This new algorithm, by combining the LURR method with our choice of identified area with increased Coulomb stress, is devised to improve the sensitivity of LURR to measure criticality of stress accumulation before a large earthquake. Retrospective tests of this algorithm on four large earthquakes occurred in California over the last two decades show remarkable enhancement of the LURR precursory anomalies. For some strong events of lesser magnitudes occurred in the same neighborhoods and during the same time periods, significant anomalies are found if circular areas are used, and are not found if increased Coulomb stress areas are used for LURR data selection. The unique feature of this algorithm may provide stronger constraints on forecasts of the size and location of future large events.  相似文献