Atmospheric hydrological budget with its effects over Tibetan Plateau     

BAI Jingyu  XU Xiangde 《地理学报》2004,14(1):81-86

Based on 1961-2000 NCEP/NCAR monthly mean reanalysis datasets, vapor transfer and hydrological budget over the Tibetan Plateau are investigated. The Plateau is a vapor sink all the year round. In summer, vapor is convergent in lower levels (from surface to 500 hPa) and divergent in upper levels (from 400 to 300 hPa), with 450 hPa referred to as level of non-divergence. Two levels have different hydrologic budget signatures: the budget is negative at the upper levels from February to November, i.e., vapor transfers from the upper levels over the plateau; as to the lower, the negative (positive) budget occurs during the winter (summer) half year. Evidence also indicates that Tibetan Plateau is a "vapor transition belt", vapor from the south and the west is transferred from lower to upper levels there in summer, which will affect surrounding regions, including eastern China, especially, the middle and lower reaches of the Yangtze. Vapor transfer exerts significant influence on precipitation in summertime months. Vapor transferred from the upper layers helps humidify eastern China, with coefficient -0.3 of the upper budget to the precipitation over the middle and lower reaches of the Yangtze (MLRY); also, vapor transferred from east side (27.5o-32.5oN) of the upper level has remarkable relationship with precipitation, the coefficient being 0.41. The convergence of the lower level vapor has great effects on the local precipitation over the plateau, with coefficient reaching 0.44, and the vapor passage affects the advance and retreat of the rainbelt. In general, atmospheric hydrologic budget and vapor transfer over the plateau have noticeable effects on precipitation of the target region as well as the ambient areas.  相似文献   

Refining the pre-industrial atmospheric Pb isotope evolution curve in Europe using an 8000 year old peat core from NW Spain   总被引：1，自引：0，他引：1  

M.E. Kylander  D.J. Weiss  A. Martínez Cortízas  R. Garcia-Sanchez 《Earth and Planetary Science Letters》2005,240(2):467-485

Pb pollution has existed for several millennia and remains relevant today. By using peat cores as environmental archives it is possible to reconstruct this long history on a regional scale. This is a significant contribution to the findings from ice core records, the only other archive recording purely atmospheric additions. Without information that allows linking and comparison between sites regionally, within Europe and elsewhere, our ability to make coherent global models of the natural Pb cycle, and anthropogenic forcing of this cycle, is limited. In this respect, the characteristics of the Pb pre-pollution aerosol (PPA) are important to define globally. We characterize for the first time a PPA in Southern Europe with [Pb] = 0.78 ± 0.86 μg g^− 1, net Pb accumulation rates of 0.032 ± 0.030 mg m^− 2 y^− 1 and a ²⁰⁶Pb / ²⁰⁷Pb signature of 1.25470 ± 0.02575. This PPA Pb isotope signature is more radiogenic than that found thus far in Western and Northern Europe. Spain is a historically important mining site. Using three-isotope plots and a pool of potential Pb isotope signatures, a detailed source appointment of both natural and anthropogenic Pb sources was made. We found evidence of Saharan aridification and its termination ∼4400 BP and/or agricultural signals and strong local control (from rock and soil) of the Pb PPA. Human impact is first recorded at 3210 BP but does not exceed 50% of deposited Pb until 3005 BP. Mines in SE Spain dominate early Pb pollution history at this site. During the rise of Roman rule, contributions come from mines in N, NW and SW Spain with no strong indication of other European mining activities. In Medieval and Industrial times local contributions to the peat bog are reduced.  相似文献   

Thermodynamic conditions of framework grain dissolution of clastic rocks and its application in Kela 2 gas field   总被引：2，自引：2，他引：2  

LAI Xingyun  YU Bingsong  CHEN Junyuan  CHEN Xiaolin  LIU Jianqing  MEI Mingxiang  JING Weiguang & CHENG Suhua School of Earth Sciences  Mineral Resources  China University of Geosciences  Beijing  China  Key Laboratory of Lithospheric Tectonics  Deep-level Process  Exploration of Ministry of Education  Beijing  China 《中国科学D辑(英文版)》2005,48(1):21-31

Feldspar and clastic debris are the most important constituent framework grains of sedimentary clastic rocks and their chemical dissolution plays an essential role in the formation and evolution of the secondary pore in the reservoir rocks. On the basis of thermodynamic phase equilibrium, this study investigates the chemical equilibrium relationships between fluid and various plagioclase and K-feldspar in diagenesis of the sediments, particularly, the impact of temperature and fluid compositions (pH, activity of K+, Na+, Ca2+ and so on) on precipitation and dissolution equilibria of feldspars. Feldspar is extremely easily dissolved in the acid pore water with a low salinity when temperature decreases. The dissolution of anorthite end-member of plagioclase is related to the Ca content of the mineral and the fluid, higher Ca either in the mineral or in the fluid, easier dissolution of the feldspar. Moreover, the dissolution of albite end-member of plagioclase is related to Na of both the mineral and fluid,  相似文献   

The lacustrine sedimentary records of coal-burning atmospheric pollution     

E. Appel  V. Hoffmann 《中国科学D辑(英文版)》2005,48(10)

With the acceleration of industrialization, coal- burning atmospheric pollution is getting more and more serious in many regions in China. However, there are only about ten odd years literature records about pollution in some large and mid-sized cities, where the atmosphere has perhaps been polluted for several decades, and therefore it is difficult to know the process and characteristic of pollution, and diffi-cult to evaluate its damage to environment. Lacustrine sediment, a natural record w…  相似文献   

Taxonomic composition and seasonality of diatoms in three Dinaric karstic lakes in Croatia     

Nenad Jasprica  Dubravka Hafner 《Limnologica》2005,35(4):304-319

The composition and temporal distribution of planktonic diatoms were studied in three small shallow karstic lakes – Modro Oko, Desne, and Kuti – throughout the seasons in 1994, 1995, 1997, and 1998. Physico-chemical parameters did not differ among the three lakes, except for NO₃ concentrations. Altogether, 137 diatom taxa within 41 genera were found in all three lakes combined. The highest number of taxa belonged to the genera Surirella (13), Navicula (12), andCymbella (9). Most taxa were tychoplanktonic, with true panktonic taxa contributing only 14% of the total. Despite their physical-chemical similarity, the lakes showed differences in the structure and dynamics of their diatom communities. Blooms occurred at different times in each of the lakes, and community similarity (Jaccard index) among all three was low (17.6–29.1%). The highest mean values of surface diatom abundance in Modro Oko (2199 cells L⁻¹), Desne (7900 cells L⁻¹), and Kuti (20690 cells L⁻¹) were not significantly different. Margalef's species richness index did not differ either among the lakes or seasonally. Only five diatom taxa in quantitative samples, and 22 taxa in net-samples, were common to all lakes. The most frequent diatoms were Cyclotella striata (56–93%), Fragilaria ulna (50–67%), and Asterionella formosa (27–83%). The most abundant taxa in Modro Oko, Desne, and Kuti were, respectively, Cymbella sp. 1 (402 cells L⁻¹), Cyclotella striata (3000 cells L⁻¹) and Asterionella formosa (20690 cells L⁻¹). Eighteen taxa were recorded for the first time in Croatia: Amphora commutata, Caloneis amphisbaena var. subsalina, C. silicula var. peisonis, Campylodiscus echeneis, Coscinodiscus lacustris, Denticula elegans, Gyrosigma acuminatum var. lacustre, G. distortum var. parkeri, G. fasciola, Navicula menisculus var. menisculus, N. pusilla, N. helensis, Stauroneis parvula var. prominula, Staurosira construens f. subsalina, Stephanodiscus sp. 1, Surirella gracilis, S. ovalis, and S. striatula. The genus Stephanodiscus was recorded for the first time in Croatia.  相似文献   

A Possible Detection of the 26 December 2004 Great Sumatra-Andaman Islands Earthquake with Solution Products of the International GNSS Service   总被引：1，自引：0，他引：1  

J. Kouba 《Studia Geophysica et Geodaetica》2005,49(4):463-483

The main goal of this work is to critically review the IGS solution products and Precise Point Positioning (PPP) in order to demonstrate their potential to contribute to studies of large earthquakes such as the one that devastated Southeast Asia on December 26th, 2004. In view of a possible detection of the Mw 9.0 Sumatra-Andaman Islands Earthquake of December 26, 2004, position solutions, ranging from intervals of years to one second, of four International GNSS Service (IGS) stations within 3000 km of the epicenter were examined. The IGS combined, cumulative solution product (IGS04P51), consisting of epoch and station velocity solutions and based on data spans of several years prior to the earthquake, was used as a reference. Four IGS combined weekly position solutions (igs04P1301-4), two weeks before and after the earthquake, were utilized for the weekly solution resolution. PPP static and kinematic solutions with IGS Final combined orbits and clocks were used for the mean daily and instantaneous 5-min and 1-sec epoch solutions, respectively. The most significant changes, detected by both weekly and daily solutions occurred in longitude. The nearest IGS station ntus, about 1000 km east of the epicenter, moved westward about 15 mm, while the more distant Indian station iisc (∼ 2300 km NW from the epicenter), shifted about 15 mm eastward. In spite of position errors caused by interpolation of the 5-min IGS clocks, the 1-sec solutions, based on separate data sets, available only for two stations (iisc, dgar), still showed seismic surface waves, in particular at the Indian station iisc. Precise daily IGS combined polar motion and length-of-day products, after correcting for the atmospheric effects, also likely detected, statistically significant, anomalistic excitations on December 26, 2004 that could be caused by this great earthquake.  相似文献   

Profondeur d'extraction racinaire et signature isotopique de l'eau prélevée par les racines des couverts végétaux     

Zakaria Boujamlaoui  Thierry Bariac  Philippe Biron  Laurent Canale  Patricia Richard 《Comptes Rendus Geoscience》2005,337(6):589-598

We seek to identify the depth to which water is extracted by the roots in the soil. Indeed, in an isotopic steady-state condition of leaf water, transpiration introduces into the atmosphere a vapour whose isotopic signature is identical to that of root water. In the isotopic models of atmospheric general circulation, it is classically allowed that the signature of transpiration belongs to the meteoric water line. This supposes that the water taken by the roots has escaped with the evaporation of the soil and comes thus from the deep layers of the soil. At the time of experimentation carried out on maize plants (Nemours, Seine-et-Marne, France), this extraction depth was inferred from the comparison between the signature of the water measured on the level of the first internode of the stems of the plants and the isotopic profile of water in the soil. When the flow of transpiration reaches a maximum value, the plant uptakes water resulting from precipitations and which preserves its non-evaporating character after having quickly infiltrated in the deep layers of the soil. This relates to only 55% of the flux transpired by the canopy, the remainder presenting an evaporating character more or less marked according to ambient conditions. This experiment invalidates the classical hypothesis used in isotopic models of general atmospheric circulation in temperate regions. In fact, only half the amount of water vapour transpired by the canopy during the day presents a signature similar to that of the rainwater sampled in deep soil layers. To cite this article: Z. Boujamlaoui et al., C. R. Geoscience 337 (2005).  相似文献   

“雪龙号”2003北极航次气相多环芳烃纬度分布观测          下载免费PDF全文

丁翔  谢周清  向彩红  麦碧娴  王新明  孙立广  盛国英  傅家谟 《极地研究》2005,17(4):272-278

2003年“雪龙号”北极科学考察期间,对沿途海洋大气进行采样,分析其中气相多环芳烃的空间分布。结果显示,气相中主要是2-4环的多环芳烃,其中菲为主要的化合物,平均占到总多环芳烃的55.1%。在整个航程的广泛区域尺度内,气相总多环芳烃浓度在1043.9-92993.1pg/m3。空间分布上,远东亚的海面>北太平洋海面>北极圈以内海面;总多环芳烃的浓度随纬度升高呈现显著降低的趋势。通过Clausius-Clapeyron方程对浓度和温度相互关系的分析表明,温度是控制气相多环芳烃长距离传输的主要因素。  相似文献   

The southern Norwegian Sea during the last 45 ka: hydrographical reorganizations under changing ice‐sheet dynamics     

《第四纪科学杂志》2017,32(7):908-922

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Runoff response of a small agricultural basin in the argentine Pampas considering connectivity aspects     

María Guadalupe Ares  Marcelo Varni  Celio Chagas 《水文研究》2020,34(14):3102-3119

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