Spatial variations in methane emissions from natural wetlands in China

Natural wetlands are thought to be one of the largest natural sources of atmospheric methane concentrations. Although numerous studies referred to the rate of methane fluxes in different geophysical regions, only a few had estimates of the overall geographical methane emissions in China. This study estimated the spatial variations of annual methane emissions with the pixel size of 1 km × 1 km from natural wetlands, excluding water surface, in China. The natural wetland areas were extracted from the database of the 2000 land covers, and geophysical divisions were used to represent different climate conditions. Methane emission in every geophysical region was calculated based on methane release factors obtained from an extensive overview of published literature and the data of elevation and vegetation proportion. The estimated annual methane emissions ranged from 0 to 5,702.8 kg per pixel within the area of 1 km², and the spatial variation in methane emissions was strongly correlated with proportion of wetlands in the area. The total methane emission from natural wetland in China ranged from 3.48 to 7.16 Tg (terrogram, unit of weight) per year, with the mean value of 4.94 Tg per year, based on the area 133,000 km² of natural wetlands. Specifically, the wetland in Northeast China had the highest contribution in China (39 %). Inner Mongolia and Qinghai-Tibet highland represented for about 25 and 21 %, respectively. The other 15 % of the measured methane was released in Northwest, North, Central, and South China.     

Large European earthquakes of the 20th century

The magnitudes of the largest events in the European area have not exceeded M = 8 (shallow shocks) and m = 7.8 (intermediate depth shocks), respectively during the 20th century. Their geographical and depth distributions are discussed. The magnitude frequency relationships and the Gumbel III model define the statistical expectancy of the extreme events within the whole area. The strain release has a relatively constant trend between 1901–1975.     

Problem of old marine shorelines in Russian geology during second half of nineteenth century

In Russia, as elsewhere, the study of paleogeography emerged near the end of the nineteenth century and was based on facies analysis and paleoecology. Determining former shorelines is the most important question in paleogeography. The actualist method, by which the results obtained from an examination of present-day facies could be extrapolated to the past, provided a reliable premise for the determination of ancient shorelines. Recent changes in coasts were observed and were attributed to rise and fall of ocean level, to uplifts and subsidences of the land, or to sediment compaction. Since much of the continental surface has still not been adequately studied, however, the picture of land-sea distribution throughout geological history was fragmentary. It was discovered that conglomerates formed the bulk of coastal sediments in mountainous littorals; sandy and argillaceous deposits were widespread in the shore zone of low-lying land. Golovkinskiy was of the opinion that coastal sedimentation was influenced by climatic factors. Influences of lagoons, barrier beaches, and rivers on shorelines were appreciated. In discovering the position of Russian Devonian and Carboniferous shorelines, Inostrantsev made use of well-known fossil forms. Kovalevskiy attempted to reconstruct the distribution of land and sea over Europe in the Jurassic and Cretaceous. Nikitin pointed out that many paleogeographic maps show only the area in which marine sediments are found today and the limits differ considerably from the former extent of the seas. In 1880, Karpinskiy made the first attempt to depict the configuration of land and sea during the Carboniferous, Devonian, Permian and Triassic. The works of many other geologists are also reviewed.—J. D. Haun     

The climate of Carpathian Region in the 20th century based on the original and modified Holdridge life zone system

The Holdridge life zone system has already been used a number of times for analysing the effects of climate change on vegetation. But a criticism against the method was formulated that it cannot interpret the ecotones (e.g. forest steppe). Thus, in this paper transitional life zones were also determined in the model. Then, both the original and modified life zone systems were applied for the climatic fields of database CRU TS 1.2. Life zone maps were defined in the Carpathian Region (43.5–50.5° N, 15.5–28° E) for each of five 20-year periods between 1901 and 2000. We estimated correctness of the result maps with another vegetation map using Cohen’s Kappa statistic. Finally, temporal changes in horizontal and vertical distribution of life zones were investigated. The coverage of boreal region decreased with 59.46% during the last century, while the warm temperate region became almost two and a half larger (257.36%). The mean centres of those life zones, which were not related to mountains, shifted northward during the investigation period. In case of the most abundant life zone types, the average distribution elevation increased. Using the modified model, the potential distribution of forest steppe could be also identified.     

20世纪暴雨和洪水极值的年代际变化

利用20世纪100年(特别是后50年)2万多个雨量站和175个大中河流水文站的实测和调查雨量和流量资料,分析了中国大陆(外流区)暴雨和洪水极值的年代际变化,其中包括长期站暴雨的年代均值变化、20世纪50年点雨量极值的前后期平均值对比、最大点雨量发生年代分布和特大洪峰流量的年代分布。分别就5种历时、不同地区的暴雨洪水极值随年代的变化作了分析,揭示了变化的事实,计算了多项年代比率,探讨了影响因子。     

Geochemical differentiation of Quaternary sediments from the Pampean region based on soil phosphorus contents as detected in the early 20th century

Data obtained in the early 20th century on the total phosphorus (TP) content in soil materials from the Pampean region have been processed and plotted on maps of the region. Approximately 1200 subsoil data and 1400 surface horizon data obtained using the same analytical method, have been processed. According to differences in phosphorus content, several areas have been demarcated. Limits and characteristics of these areas have been correlated with data from the more recent literature regarding the P distribution and with both mineralogical and sedimentological information on surface materials. Results suggest that a confluence of sediments from different provenances (i.e. the Andean Range, the Pampean Hills, and the Brazilian Shield) is found in the Argentine Pampean region.     

《翁同龢日记》记录的19世纪后半叶北京的沙尘天气?

依据清代《翁同龢日记》中天气状况的描述，整理出公元1860～1898年间逐月的沙尘天气日数，基于记录完整月份的沙尘天气日数，统计分析了公元1860～1898年北京沙尘天气日数的平均状况和变化特征。分析发现公元1860～1898年，北京年均沙尘天气记录为10.4天，即使不考虑与现代观测记录标准的差别，亦肯定高于1990年代7.7天/年的平均频次；春季是沙尘天气的高发季节，其占全年沙尘日数的百分比达到70%，其中4月和5月两个月的接近53%；其次为冬季，占20%。与公元1961～2000年相比，公元1860～1898年的春季沙尘天气日数百分比偏高10.9%，沙尘天气在春季的集中程度明显偏高。公元1860～1898年间，年沙尘日数和春季沙尘日数均呈波动减少之势；研究时段内，共出现23次2天以上连续（或持续）的沙尘天气过程，最长的一次持续了4天。这些发现将有益于研究气候变化对沙尘天气影响和分析北京沙尘天气的演变规律。     

Water pollution perspectives: Problem conceptualizations and abatement strategies in Sweden during the 20th century

Water pollution control has been a matter of public concern for more than a century. One focus of this study was the development of water pollution perspectives during the last 50 years, including social perceptions of water pollution problems and societal judgements of the feasibility and practicability of various ways to solve them. Another focus was the conceptualizations of water pollution, made by natural scientists and technicians, who are viewed as crucial suppliers of knowledge.The concern for health, dominating Swedish water policy since the middle of the 19'th century, gave priority to local hygienic improvement by the construction of drinking water supply and wastewater removal systems. The initial abatement strategy aimed at mitigating local effects by the maintenance of self-purifying capacities of the recipients and treatment of drinking water. In the middle of this century source-related pollution abatement methods were introduced in reply to increasing needs for drinking water and social recreational demands. The development was limited by administrative and technical capacity, cost estimations setting the standards of feasibility. In the 1960's time and space perspectives were extended. The holistic view of cycling within and between ecosystems made the impacts of non point sources upon water quality visible. The pollution control perspective is now gradually being replaced by the goal of sustainable resource management, adding the notion of pollution prevention.During the last 50 years temporal and spatial scales have been widened. Measures taken did not correspond to current conceptualizations of water pollution. Considerable lags of implementation were found and technical solutions accumulated into infrastructural networks of an increasing magnitude and complexity.     

基于第二代Curvelet变换的地震资料随机噪声衰减

噪声衰减是地震资料处理中的关键问题之一。根据Curvelet变换对含有光滑边界的二维二阶连续可微函数所具有的稀疏表示性能,给出了Curvelet变换域地震资料随机噪声衰减的阈值方法;并给出了基于地震资料中随机噪声是独立同分布的高斯白噪假设条件下的阈值估计方法。通过合成数据和叠后实际数据算例,对该方法的有效性进行验证。结果表明,Curvelet变换不仅可以很好地衰减随机噪声,并且能较好地保持有效信号。     

解燃眉之急：20世纪上半叶地方地质矿产调查机构探析

20世纪上半叶矿产资源在经济建设中的巨大作用,引起了地方政府的高度重视。除西藏以外,各地均组织开展了地质矿产资源的调查。本文通过对省档案、民国时期政府公报与期刊杂志等文献资料的梳理,对地方政府组织地质矿产资源的考察背景、组织形式及作用进行了宏观的整理和案例分析。希望本项研究通过探寻民国时期地方矿产调查的组织形式和总体特征,为地方资源调查的组织建设有所借鉴。     

Progradation and retrogradation of the Medjerda delta during the 20th century (Tunisia,western Mediterranean)

The aim of this study is the reconstitution of the recent morpho-sedimentary evolution of the Medjerda River delta. We examine the spatio-temporal evolution of the Medjerda shoreline between 1936 and 2016 using satellite images, complemented by sedimentological and geochemical analyses and ²¹⁰Pbex and ¹³⁷Cs radiometric data. The general tendency of the shoreline evolution shows an increasing progradation (300 ± 12 m) between 1936 and 2016. Yet the mesoscale Net Shoreline Movement position (NSM) and the End Point Rate (EPR) reveal an erosion pattern estimated to be −20 m ± 0.15 m/yr during the period 1988–1999.The sedimentological analyses reveal four main lithostratigraphic units. The fine sand substratum layer (Md = 0.08 mm) decreases toward clay and silt facies (Md < 0.063 mm), rich in continental plant debris. The geochemical results reveal gradual incoming of the terrigenous component instead of marine deposits. The ¹³⁷Cs/²¹⁰Pbex radiometric dating confirms the functioning of the new river flow by the 1950s with the highest sedimentation rate being 3.3 cm/yr. Our results show that the Sidi-Salem dam impoundment (1981) led to a dramatic reduction of sediment discharge, a decrease of the grain size with nearly no more sand reaching the coast, and the shoreline retreat.     

Government and urban management in the 20th century: policies,contradictions, and weaknesses of the New Right

Throughout the 20th century, government in the U.S. has gone through significant changes; initially responding to the disorder of early capitalism, and later, to the economic crisis of the 1970s. This article will explore the changes in the U.S. political landscape over the last century, as well as the recent rise of neo-liberalism. In addition, with the analysis of the model laissez-faire municipal government, the City of Houston, the article will illustrate how the basic weaknesses of neoliberalism at the national level are also evident at the local scale of government.

4种再分析气温资料在羌塘国家级自然保护区的适用性研究

利用1979 - 2018年羌塘国家级自然保护区边缘的3个气象站点狮泉河（西部）、 申扎（中部）和安多（东部）的观测气温（OT）, 与ERA-Interim（ET）、 NCEP/NCAR（NT1）、 NCEP/DOE（NT2）和JRA-55（JT）4种再分析气温资料, 从年际变化和年变化两方面采用多年气温变化趋势、 均方差、 相关性等参数方法在羌塘自然保护区进行了适用性研究。结果表明： 从多年平均气温年际变化来看, 4种再分析资料在狮泉河（西部）的适用性较差, JRA-55资料在安多（东部）和申扎（中部）的适用性较好, 且冬季再分析气温资料与观测气温的相关性好于夏季; 从多年平均气温年变化来看, 均表现为冬季（1月或12月）最低, 夏季（7月或8月）最高的“单峰型”变化。综合来看, JRA-55资料在羌塘自然保护区的适用性较好, ERA-Interim对多年气温趋势变化表现不准确, NCEP/NCAR和NCEP/DOE与观测气温相比显著偏低。     

Floodplain lakes as an archive for the metal pollution in the River Elbe (Germany) during the 20th century

The German Elbe River floodplains rank under the most polluted areas in Europe. A sudden concentration increase of potentially harmful elements (PHEs) is documented in sediment profiles of Elbe bayous. The increase is dated to the mid of the 20th century (¹³⁷Cs) and indicates industrialization of the former German Democratic Republic (GDR) as the source of intense pollution. The collapse of the GDR and the industries in the 1990s is traced by a concentration decrease in young sediments. The contamination is restricted to an increase of unstable binding forms; the hydroxide binding form is predominant. The geogenic concentration portions are of normal level and remain stable throughout the profiles (0–2 m). The equilibrium of contradictory binding forms in the sediments makes it mandatory not to interfere with the thermodynamic conditions and to keep the Elbe floodplain as an undisturbed ecological system.