Seasonal changes in nitrogen and phosphorus transport in the lower Changjiang River before the construction of the Three Gorges Dam

Water and sediment samples were collected at Datong from June 1998 to March 1999 to examine seasonal changes in the transports of nitrogen (N) and phosphorus (P) from the Changjiang River (Yangtze River) to the East China Sea (ECS). Dissolved inorganic nitrogen (DIN; dominated by nitrate) concentration exhibited small seasonality, and DIN flux was largely controlled by water discharge. Dissolved inorganic phosphorus (DIP) concentration was inversely correlated with water discharge, and DIP was evenly delivered throughout a year. The transports of DIN and DIP from the Changjiang River were consistent with seasonal changes in nutrient distributions and P limitation in the Changjiang Estuary and the adjacent ECS. Dissolved organic and particulate N (DON and PN) and P (DOP and PP) varied parallel to water discharge, and were dominantly transported during a summer flood. The fluxes of DOP and particulate bioavailable P (PBAP) were 2.5 and 4 times that of DIP during this period, respectively. PBAP accounted for 12–16% of total particulate P (PP), and was positively correlated with the summation of adsorbed P, Al–P and Fe–P. Ca–P, the major fraction of PP, increased with increasing percent of CaCO₃. The remobilization of riverine DOP and PBAP likely accounted for the summer elevated primary production in DIP-depleted waters in the Changjiang Estuary and the adjacent ECS. The Changjiang River delivered approximately 6% of DIN (1459 × 10⁶ kg), 1% of DIP (12 × 10⁶ kg), and 2% of dissolved organic and particulate N and P to the totals of global rivers. The construction of the Three Gorges Dam might have substantially reduced the particulate nutrient loads, thereby augmenting P limitation in the Changjiang Estuary and ECS.     

宽甸岩金预测区指示元素的优选

本文介绍了在宽甸无已知金矿床地区岩金预测工作中优选指示元素的思路。依据金矿地球化学理论,参考成矿带内已知金矿地球化学资料初选指示元素作为化学分析项目。化学分析结果出来后,编制地球化学图件时,考虑到减轻图幅负担和编图工作量,突出有用找矿信息,我们利用元素的变异性和致矿系数筛选出具有明显变异性和较高致矿性的元素,在此基础上利用元素间统计相关性和空间相关性,保留与成矿元素Au有明显相关性的元素,作为优选出的指示元素。     

2021年、2022年中国大陆地震灾害损失述评

基于2021年、2022年中国5.0级及以上地震目录,结合应急管理部、有关省(自治区、直辖市)地震局的地震灾害评估报告和相关资料,对中国大陆地震灾害情况、主要地震灾害事件及其特点进行了总结和分析。此外,按省份总结了各省地震灾害事件及地震灾害特点。其中,云南省中强震多、强震少,震区房屋抗震能力较高,人员伤亡较小; 四川省中强震少、强震多,次生灾害较为发育,造成严重人员伤亡; 青海省虽然震级高、破坏性强、致灾范围广,但震区地广人稀,房屋抗震设防等级较高,人员伤亡少。最后,结合历史震害统计数据,分析对比近2年中国大陆地震灾害致灾特点。     

中国"互联网+"发展的空间关联网络及其影响因素——基于社会网络分析视角的实证研究

借助社会网络分析方法研究“互联网+”发展的空间关联网络特征,并利用QAP方法探究中国“互联网+”空间关联网络的影响因素。研究发现,“互联网+”发展的空间关联呈现显著网络特征,可划分为“净溢出”“经纪人”“主受益”以及“双向溢出”四大类型板块,并且板块内部具有较明显的“等级”属性。技术创新、基础设施、人力资本、市场发展、对外开放对“互联网+”发展的空间关联网络存在正向影响。地理距离对“互联网+”空间关联网络存在抑制作用,随着地理距离的不断增大,“互联网+”的知识溢出和流动效应逐步衰减。     

Trend and extreme occurrence of precipitation in a mid‐latitude Eurasian steppe watershed at various time scales

The confounding effects of step change invalidate the stationarity assumption of commonly used trend analysis methods such as the Mann–Kendall test technique, so previous studies have failed to explain inconsistencies between detected trends and observed large precipitation anomalies. The objectives of this study were to (1) formulate a trend analysis approach that considers nonstationarity due to step changes, (2) use this approach to detect trends and extreme occurrences of precipitation in a mid‐latitude Eurasian steppe watershed in North China, and (3) examine how runoff responds to precipitation trends in the study watershed. Our results indicate that annual precipitation underwent a marginal step jump around 1995. The significant annual downward trend after 1994 was primarily due to a decrease in summer rainfall; other seasons exhibited no significant precipitation trends. At a monthly scale, July rainfall after 1994 exhibited a significant downward trend, whereas precipitation in other months had no trend. The percentage of wet days also underwent a step jump around 1994 following a significant decreasing trend, although the precipitation intensity exhibited neither a step change nor any significant trend. However, both low‐frequency and high‐frequency precipitation events in the study watershed occurred more often after than before 1994; probably as either a result or an indicator of climate change. In response to these precipitation changes, the study watershed had distinctly different precipitation‐runoff relationships for observed annual precipitations of less than 300 mm, between 300 and 400 mm, and greater than 400 mm. Copyright © 2013 John Wiley & Sons, Ltd.     

Estimation of areas of sand and dust emission in the Hexi Corridor from a land cover database: an approach that combines remote sensing with GIS

The present study combined remote sensing with geographical information system (GIS) technology to interpret Landsat TM images from 1996 to 2000 and establish a land cover database for the Hexi Corridor of China’s Gansu Province. The areas of sand and dust emission and trends in their change were extracted by analyzing the database, with the following results: In 2000, the source area for sand and dust storms totaled nearly 170,000 km², accounting for 75.1% of the study region. The emission area decreases from as much as 70,000 km² in winter and spring to around 58,000 km² in summer and autumn, accounting for 41.1 and 34.1% of the source area, respectively. During the 4 years of the study period, the emission area decreased by nearly 57 km² in winter and spring (a 0.1% change); however, the vulnerability of the land surface to wind erosion increased in ca. 190 km² and decreased in ca. 102 km². Although the area of dust emission decreased from 1996 to 2000, the area vulnerable to wind erosion increased by ca. 87 km², and the increased number of sand and dust storm days in the region between 2000 and 2003 appears to be correlated with this increase.     

排水管网多尺度几何语义建模

针对排水管网管理业务的不同需求,研究排水管网的多尺度几何语义表达方法,本文提出了包含"源—网—厂—汇"的排水管网多尺度几何语义模型.通过对排水管网组成要素及其相互间的关系进行系统地分析,并参考CityGML规范,提出了排水管网多细节层次模型;根据不同排水管网要素的特点,采用符号化及BIM等建模方式分别构建了不同细节层次...     

Experiment on Coordinated Observation of Offshore Typhoon in China

The lack of sufficient direct observation data of typhoon fine structure is the main bottleneck that restricts the further development of typhoon discipline and forecasting. This paper briefly introduced the basic information of the National Key R&D Program of China, entitled “Experiment on Coordinated Observation of Offshore Typhoon in China”, which started in early 2019. Firstly, the importance and necessity of the program around the national needs on typhoon-related disaster reduction and prevention were explained. Then, the coordinated observation difficulties and frontiers in the current typhoon discipline situation from the development and improvement of the physical mechanism and key forecasting technologies were shown. The overview of the direct observation instrument and platform, the field campaign and the parameterization techniques related to physical process in typhoon numerical modeling was provided. Finally, the key scientific and technical issues and main research contents of the program were given.     

论德尔尼黄铁矿型铜钴矿床的地质特征及其与塞浦路斯铜矿的区别

通过对德尔尼铜钴矿床与塞浦路斯铜矿的对比,进一步明确了德尔尼铜钴矿床为与印支期黑云花岗岩有成因联系的岩浆热液矿床。矿区的超基性岩或超基性火山角砾岩都是不含矿的,与矿床无成因联系;底辟上升侵位也不存在。将德尔尼铜钴矿床作为火山岩块状硫化物矿床系列中的最基性端员缺乏依据。     

中学地理科学实验的六大类型及其案例分析

依据实验的根本目的,为拓展学生对地理过程的理解,体验真实的地理原理,笔者将中学地理科学实验划分为经典实验室实验、时间变化模型实验、类比实验、空间变化模型实验、物理模型实验以及计算机模型实验六大类型,并对每一类型实验进行举例分析,希望以此深化地理科学实验的理论研究、丰富地理科学实验的实践案例、培养学生的地理核心素养,为地理科学实验教学研究提供新的视角。