共查询到20条相似文献，搜索用时 31 毫秒
1.
YU Yixin PENG Wenxu SHI Shengbao SUN Hefeng LU Man SHANG Peng Delores ROBINSON LU Yuehan 《《地质学报》英文版》2022,96(1):261-272
Despite the upsurge in hydrocarbon exploration in the Lake Albert Rift Basin(LARB)over the past three decades,systematic characterization of hydrocarbon compositions remains lacking,leading to uncertainties in source rock and oil generation determination.We characterized crude oil compositions and oil sand samples in the northern and southern subbasins of LARB.The relative abundance of normal and branched linear alkanes,hopanes,steranes,and aromatic hydrocarbon suggest that northern and southern hydrocarbons were deposited in anoxic to suboxic lacustrine environments and share similar biological source compositions(i.e.,a mixture of plants and aquatic algae and bacteria).Relative to southern samples,northern samples show more negative δ13C values for oils,saturates and aromatics,indicating longer migration paths,and exhibit higher MPI-1,DNR-1 and 4-/1-MDBT ratios,indicating higher maturity.Between the two possible sets of source rocks(upper Miocene and Jurassic strata),the positive δ13C values of saturated hydrocarbons(average=-20.5‰)suggest that the upper Miocene lacustrine shale is the most likely candidate.Oleanane index(<5% in our samples)does not exclude either source rock possibility,and C28/C29 regular sterane(average=0.63)may be biased by high terrestrial inputs in a lacustrine setting.Together,our data show that northern and southern oils originate from the same source rocks but different oil kitchens.Given the similar geochemical characteristics of southern and northern oils,previous exploration successes in the northern subbasin likely suggest similar potential in the southern sector,while other elements influencing exploration success must be also evaluated. 相似文献
2.
GeoJournal - Broad academic interest in measuring social relationships within an urban context has grown over recent decades. Significant research attention is focused on where social synergies... 相似文献
3.
Zhang Tingyu Fu Quan Wang Hao Liu Fangfang Wang Huanyuan Han Ling 《Natural Hazards》2022,110(2):823-846
Natural Hazards - Landslide hazards have attracted increasing public attention over the past decades due to a series of catastrophic consequences of landslide occurrence. Thus, the mitigation and... 相似文献
4.
da Silva Fabricio Polifke da Silva Alfredo Silveira da Silva Maria Gertrudes Alvarez Justi Pires Gisele Dornelles 《Natural Hazards》2022,110(1):695-718
Natural Hazards - The ability to forecast extreme precipitation events has become increasingly important over the last decades due to their significant impacts on society and properties. In this... 相似文献
5.
中国大陆现代降水表现出若干长期变化特征,对现代降水趋势性变化的原因,目前还没有很好了解。结合多种资料分析以及前人研究成果,对中国大陆近几十年降水变化趋势的原因进行了探讨,得到以下初步认识:① 现代降水量变化趋势具有明显的地域性差异,全国平均没有表现出显著增加或减少的长期变化,但强降水事件频率和降水量出现明显增多,而小雨事件特别是痕量降水事件显著减少。② 再分析资料表明,最近几十年全国水汽净收支量在一定程度上增加了,实际观测资料显示近地面和对流层中下层空气比湿或大气可降水量出现较明显上升趋势。③ 代用资料序列分析显示,全国大部地区近几十年降水变化仍处于晚近历史时期正常自然波动范围内;近百年观测的降水量序列也表明,黄淮海地区降水具有多重时间尺度相互叠加作用特点,低频自然气候变异的影响信号有清晰表现。④ 人类活动引起的大气中温室气体浓度增加对全国或东部季风区现代降水变化影响的信号,目前仍难以识别;区域性近地面风速减弱导致的雨量观测系统偏差以及大范围气溶胶浓度增加,可能是东部季风区大多数台站观测到的强降水事件频率增加和小雨频率显著减少的两个重要原因。⑤ 主要与城市化影响相关的地面观测资料系统偏差,可以部分解释现有分析表明的短历时强降水事件频率和累计降水量增加现象,同时也很可能是城市台站小雨和痕量降水事件频率明显下降的另一重要原因。 相似文献
6.
PAUL COLE ANGUS DUNCAN JOHN GUEST 《Geology Today》1996,12(2):68-72
The 1957–58 eruption of Capelinhos, on Faial, in the Azores, built a new volcano at the west end of the island. Erosion by the sea has subsequently destroyed over two-thirds of this structure and will probably continue to remove much of the rest of the volcano over the next few decades. 相似文献
7.
Acta Geotechnica - The identification of contaminated soils has gained increasing interest over the decades in the geoenvironmental issues. In this study, a probabilistic method based on the... 相似文献
8.
Landslides - Increasing number of landslides occurred in the cold regions over the past decades due to rising temperature or forest fires associated with climate change. The instability of thawing... 相似文献
9.
Natural Hazards - Due to a wide range of socio-economic losses caused by drought over the past decades, having a reliable insight of drought properties plays a key role in monitoring and... 相似文献
10.
Natural Hazards - There has been an increase in drownings over recent decades in Australia, particularly among rock fishers swept from the edge of rock platforms. Platform morphology is central to... 相似文献
11.
Natural Hazards - Arctic sea ice has declined rapidly over the past four decades at the rate of ??4.7% per decade leading to an imbalance in the oceanic heat flux. The study reported... 相似文献
12.
The emission of sulfur dioxide and metals from copper-nickel melting plants on Kola Peninsula (Russia) decreased pronouncedly over the last two decades. The decrease in the sulfate content and increase in the acid-neutralizing capability of waters were proven on the basis of the data of surveys on 75 small lakes repeated once every five years from 1990 to 2010. The variations of other parameters of the chemical composition of the waters of small lakes depend on the geological and landscape conditions of the formation of waters. The alkalinity and pH values increased in 46% of the lakes; 24% of them showed a further decrease of these parameters; and no reliable changes were traced in 31% of the lakes. The concentrations of Cu and Ni in the lacustrine water decreased 5-to 10-fold over the last two decades. 相似文献
13.
Peter M. Townroe 《Geoforum》1984,15(3):335-347
The prospects for economic growth among the developing countries of the world over the next two decades are not as promising as the experience of the last two decades. Aspects of the current world economic environment have implications for the pattern of urban growth in developing nations, and hence for the role of spatial policies. This paper outlines the U.N. projections for the growth of urban populations in the world. It then reviews the current external economic situation of the developing countries, faced by world economic recession and high levels of international indebtedness, before considering some of the implications of this situation for urban growth. 相似文献
14.
If we are to develop valid models for predicting the future of the global environment, anthropogenic forcing must become the major component of study. The technological developments needed to supply food, water and materials for 10 billion humans will dominate environmental change over thenext decades. 相似文献
15.
Conclusion This short article has made it possible to determine the current conditions of erosion in one sector of the coast of Prince
Edward Island, as well as to calculate, with as great a degree of accuracy as possible, the speed at which the ocean is destroying
the shoreline of this sector.
The intensity of shoreline erosion has varied over the years (Dubois and Longhurst 1984). The variation may perhaps be explained
in part by the fact that water temperature varies in the same proportion as the temperature of the surrounding air (Trites
1984), and that over a period of several decades, the air temperature, and the climate in general, do vary (Trites 1984).
Thus a study of the correlation between coastline erosion and climatological variations over several decades would certainly
be a useful aid for predicting the future state of the coastline.
There is also a need for a map of the various sectors of the PEI coast, showing their degree of susceptibility to various
systems of erosion. Such a map would be extremely useful both for land management purposes (construction, roads, agriculture)
and for security reasons (civil protection, ocean recreation. 相似文献
16.
A K SRIVASTAVA JAMES VOOGT S R KSHIRSAGAR KAVITA SRIVASTAVA 《Journal of Earth System Science》2016,125(1):85-93
This study examined hourly temperature data of two locations of Mumbai metropolitan city. One data point (Coloba, Mumbai) is in centre of the city and the other one (Santacruz, Mumbai) is at the airport. The study finds that there were many occasions when night-time hourly temperatures over the city centre were considerably higher than that of the airport, even though temperature at the time of sunset at both the places was nearly same. In this study, the occasions, when hourly night-time temperature over city was more than that of the airport by objectively defined threshold value (3.0 °C in this study) for most of the hours in the night, were termed as heat island events. Analysis of the study reveals that these events are mostly confined to November–February months. The study also found that frequency of such events has doubled in recent two decades in comparison to the earlier two decades. 相似文献
17.
Consistent seasonal snow cover depth and duration variability over the Western Himalayas (WH) 总被引：1，自引：0，他引：1
Precipitation in solid form, i.e., snow, during winter season over the Western Himalayas (WH) leads to the build-up of seasonal snow cover. Seasonal snow cover build-up (snow cover depth and duration) largely depends on atmospheric variables such as temperature, precipitation, radiation, wind, etc. Integrated (combined) influence of atmospheric variables on seasonal snow cover gets reflected in terms of spatial and temporal variability in seasonal snow cover build-up pattern. Hence spatial and temporal variability of seasonal snow cover build-up can serve as a good indicator of climate change in high altitude mountainous regions like the WH. Consistent seasonal snow cover depth and duration, delay days and early melt days of consistent seasonal snow cover at 11 stations spread across different mountain ranges over the WH were analyzed. Mean, maximum and percentiles (25th, 50th, 75th, 90th and 95th) of consistent seasonal snow cover depth and duration show decline over the WH in the recent past 2–3 decades. Consistent seasonal snow cover is found to melt early and snow cover build-up pattern is found to show changes over the WH. Decline in consistent seasonal snow cover depth, duration and changing snow cover build-up pattern over the WH in recent decades indicate that WH has undergone considerable climate change and winter weather patterns are changing in the WH. 相似文献
18.
O. S. R. U. Bhanu Kumar C. V. Naidu S. R. L. Rao 《Journal of Earth System Science》2004,113(3):313-319
An analysis of the mean monthly data of 124 years reveals that the relationship between the Southern Oscillation Index in
September and the winter monsoon rainfall (WMR) over Coastal Andhra Pradesh (CAP) is variable and non-stationary. In the recent
four decades, however, SOI (Sept) is negatively and significantly correlated with CAP WMR. A similar analysis is performed
using 50 years of mean monthly SSTs over Nino-3.4 region in August and September and CAP WMR to detect a possible relationship
and there is a striking positive relation between them. In both of the above cases, the September signal is more significant
in the recent four decades than for the other months and seasons for probable prediction of CAP WMR. Finally, to examine the
influence of SO on the winter monsoon rainfall, a non-parametric test “Mann-Whitney Rank Statistics” test has been applied
to the rainfall associated with extreme positive and negative SOI events 相似文献
19.
《Geoforum》1988,19(3):295-306
Although over the last three decades some of the gaps between Aboriginal and non-Aboriginal living standards and material wealth have narrowed, change has been very gradual, has been by no means universal and, in some areas, such as unemployment levels, the Aboriginal position has actually deteriorated. It seems likely that, in socio-economic terms, Aboriginal inequality will persist for many decades to come. Inequality cannot be attributed solely to lack of Government expenditure: considerable financial resources have been devoted to the improvement of Aboriginal welfare. It is clear, however, that resources have not always been used in appropriate ways and it is argued that such misallocations will continue to occur until the underlying causes of Aboriginal disadvantage, as perceived by the Aborigines themselves, are better understood. In this understanding the land question is crucial. This paper analyses Aboriginal socioeconomic transformation in the context of control over land as a vital resource. 相似文献
20.
青藏高原大气降水和气溶胶化学特征研究进展 总被引：19，自引：2，他引：17
近10 a来青藏高原大气降水和气溶胶化学研究取得了显著进展,特别是结合冰川考察和冰芯研究工作,在高海拔冰川区获得了一批降水化学资料.回顾了早期青藏高原大气降水和气溶胶化学研究的背景,从高海拔冰川区降水化学的区域分布、季节变化、全球对比以及台站降水和气溶胶化学等方面综述了近年来该领域的研究成果,并对其研究前景进行了展望. 相似文献