古里雅冰帽8米浅冰芯的化学成分组成特征及其来源   总被引：10，自引：3，他引：10  

李月芳  姚檀栋 《冰川冻土》1997,19(2):173-179

对古里雅冰帽８ｍ浅冰芯的８０个雪冰样品化学分析结果表明，化学成分主要来自陆源物质，陆源冰芯样品叶弱碱性，明显不同于一般的大气降水及南北极冰雪样品。  相似文献   

Investigating the Halogen Chemistry From High-Latitude Nighttime Stratospheric Measurements of OClO and NO2     

Emmanuel Damien Rivière  Michel Pirre  Gwenaël Berthet  Jean-Baptiste Renard  Franck Lefèvre 《Journal of Atmospheric Chemistry》2004,48(3):261-282

Two cases of simultaneous nighttime measurements of NO₂ and OClO in the winter polar stratosphere are analyzed in order to test our present knowledge of halogen chemistry in the presence of high amount of NO₂ at low temperature. Comparisons with Lagrangian model calculations using several hypotheses are performed. First simulations, using the admitted constant rates of chemical reaction, strongly underestimate the measured OClO while the NO₂ profiles are correctly reproduced. If uncertainties in actinic fluxes calculations are taken into account, simulation results do not show a significant reduction of the underestimation. A better agreement can be achieved if the formation of unstable isomers of ClONO₂ and of BrONO₂ occurs in the cold conditions of the polar stratosphere. An approximate value of the branching ratios of the channels leading to ClONO₂ and ClOONO, and to BrONO₂ and BrOONO, necessary to reproduce both OClO and NO₂ is given and discussed.  相似文献   

Physicochemistry and Mineralogy of Storm Dust and Dust Sediment in Northern China   总被引：2，自引：0，他引：2  

LIU Wei  FENG Qi  WANG Tao  ZHANG Yanwu  SHI Jianhua 《大气科学进展》2004,21(5):775-783

Dust sediments collected from 1995 to 1998 in Beijing, Dunhuang, Inner Mongolia, Kashi, the Kunlun Mountains, Lanzhou, Ningxia, the Taklimakan Desert, and Xi‘an, China, were characterized in terms of their physical, chemical, and mineralogical properties. Most aerosols and dust analysed ranged in texture from silty clay to clay loam. Their median particle diameters (Mds) generally ranged between 5 to 63μm,coinciding with those of loess from central China and the finest sand from northwestern China. The dust sediments were characterized by a predominance of SiO2 and Al2O3, followed by K2O. Their SiO2/Al2O3and K2O/SiO2 molar ratios ranged from 5.17 to 8.43 and from 0.009 to 0.0368, respectively. The mass concentration spectrum during a dust storm showed a single peak, rather than the triple peak generally observed under clear sky conditions. The dominant minerals were chlorite, illite, calcite, and dolomite.These physical, chemical, and mineralogical properties were consistent with those of aeolian soils and loess in western and central China. The results suggest that aerosols and fine-gained fractions of dust sediments collected in northern China are mainly composed of soil material transported from the arid and semiarid regions of China and Mongolia by prevailing winds. The rate of deposition and properties of dust falling on eastern China were strongly influenced by meteorological conditions, season, latitude, longitude, and altitude of the sampling sites.  相似文献   

A Modeling Study of the Effects of Anomalous Snow Cover over the Tibetan Plateau upon the South Asian Summer Monsoon   总被引：1，自引：0，他引：1  

刘华强  孙照渤王举 闵锦忠 《大气科学进展》2004,21(6):964-975

The effect of anomalous snow cover over the Tibetan Plateau upon the South Asian summer monsoon is investigated by numerical simulations using the NCAR regional climate model (RegCM2) into which gravity wave drag has been introduced. The simulations adopt relatively realistic snow mass forcings based on Scanning Multi-channel Microwave Radiometer (SNINIR) pentad snow depth data. The physical mechanism and spatial structure of the sensitivity of the South Asian early summer monsoon to snow cover anomaly over the Tibetan Plateau are revealed. The main results are summarized as follows. The heavier than normal snow cover over the Plateau can obviously reduce the shortwave radiation absorbed by surface through the albedo effect, which is compensated by weaker upward sensible heat flux associated with colder surface temperature, whereas the effects of snow melting and evaporation are relatively smaller.The anomalies of surface heat fluxes can last until June and become unobvious in July. The decrease of the Plateau surface temperature caused by heavier snow cover reaches its maximum value from late April to early May. The atmospheric cooling in the mid-upper troposphere over the Plateau and its surrounding areas is most obvious in May and can keep a fairly strong intensity in June. In contrast, there is warming to the south of the Plateau in the mid-lower troposphere from April to June with a maximum value in May.The heavier snow cover over the Plateau can reduce the intensity of the South Asian summer monsoon and rainfall to some extent, but this influence is only obvious in early summer and almost disappears in later stages.  相似文献   

低空急流与阿勒泰暖区大--暴雪   总被引：2，自引：0，他引：2  

晋绿生  赵俊荣 《沙漠与绿洲气象(新疆气象)》2004,27(2):13-15

分析了冬季产生新疆低空急流的大型环流特征及低空急流与阿勒泰暖区大-暴雪的关系。结果表明，在中高纬度欧亚范围内呈现“双阻型”，中亚中纬度高空维持纬向强急流锋区的情况下，若有巴尔喀什湖以南的暖湿气流向北输送，则有利于造成阿勒泰暖区大-暴雪的新疆低空急流产生。高低空急流的位置及强度可作为降雪量和大-暴雪落区的短期预报指标。  相似文献   

L'archivage des activités humaines par les neiges et glaces polaires : le cas du plomb     

Claude Boutron  Kevin Rosman  Carlo Barbante  Michael Bolshov  Freddy Adams  Sungmin Hong  Christophe Ferrari 《Comptes Rendus Geoscience》2004,336(10):847-867

The investigation of the occurrence of lead in dated snow and ice from Greenland and Antarctica has played a major role in our understanding of the history of the pollution of the atmosphere of our planet by this metal. Such studies have however proved to be very demanding, mainly because of the extreme purity of polar snow and ice. Reliable measurements can be obtained only if ultra-clean and highly sensitive procedures are used, as pioneered by Clair Patterson. The Greenland data show evidence of large-scale pollution of the atmosphere of the Northern Hemisphere for lead as early as two millennia ago during Greco–Roman times, especially because of mining and smelting activities in southern Spain. It peaked at the end of the 1960s, with lead concentrations in snow about 200 times higher than natural values, before declining during recent times because of the fall in the use of leaded gasoline. Lead pollution in Antarctica was already significant at the end of the 19th century as a consequence of whaling activities, the traffic of coal-powered ships crossing the Cape Horn, and mining activities in South America, South Africa and Australia. After declining because of the opening of the Panama Canal, the great economic depression and World War II, it reached a maximum during the 1980s, with lead concentrations 20 times higher than natural values. Other studies focus on past natural variations of lead in ancient ice dated from the last climatic cycles. To cite this article: C. Boutron et al., C. R. Geoscience 336 (2004).  相似文献   

Pollution history and recovery of a boreal lake exposed to a heavy bleached pulping effluent load   总被引：4，自引：0，他引：4  

Juhani Hynynen  Arja Palomäki  Jarmo J. Meriläinen  Allan Witick  Keijo Mäntykoski 《Journal of Paleolimnology》2004,32(4):351-374

We examined the effects of heavy pulp mill discharges on the Lake Lievestuoreenjärvi ecosystem and the later recovery of diatom and chironomid communities from age-dated short core samples. Beginning in 1927 the lake received a heavy effluent load from a sulphite pulp mill. Except for the recession during the Second World War and the temporary closure of the mill from 1967 to 1971, the industrial load, containing large quantities of nutrients, organic matter and toxic compounds, increased continuously. In the early 1980s, laboratory documents were falsified by the directors of the mill and the systematic illegal effluent overload led to a collapse of the whole lake ecosystem. In 1985, the outdated plant was finally closed down. Based on the assessment of chemical properties and biological remains of the sediment, we distinguished five developmental phases in the ecological state of the lake. In the pre-industrial phase, the pelagic and profundal benthic communities were dominated by species preferring ultraoligotrophic or oligotrophic lakes. Concomitant with the increasing discharge and deposition of chlorine compounds, resin acids, and mercury, as well as strong acidity and hypolimnetic and epilimnetic anoxia, the ecological status changed in a short period from excellent to bad. Finally, in the early 1960s, the majority of the lake was virtually dead and the aquatic life survived only in the uppermost littoral zone. Since 1985, a fast recovery in the water quality has led to a strong, but temporary eutrophy in pelagic communities. The main peak of eutrophication was caused by the invasion of a species new to the lake,Aulacoseira granulata var.angustissima. Later, the pelagic communities shifted towards oligotrophy, but the original, pre-industrial status has not been re-established. The profundal benthic communities have not achieved the pre-industrial structure, but at present indicate mesotrophy.  相似文献   

塔城市一次暴雪天气的分析     

唐秀李新东  刘妮娜庄晓翠 《沙漠与绿洲气象(新疆气象)》2005,28(3):14-15,18

2003年2月22日塔城市出现一次暴雪天气过程。文章着重分析了此次天气过程的高空环流形势、地面形势、T—Td等，指出暖湿气流是造成暴雪的主要原因。  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   

Environmental pollution impact on water and sediments of Kumaun lakes, Lesser Himalaya, India: a comparative study     

Brijraj K. Das 《Environmental Geology》2005,49(2):230-239

A study of the water and sediment chemistry of the Nainital, Bhimtal, Naukuchiyatal and Sattal Lakes of Kumaun, has shown that the water of these lakes are alkaline and that electrical conductivity, total dissolved solid and bicarbonate HCO ₃ ⁻ are much higher in Nainital than in the other three lakes. The weathering of limestone lithology and anthropogenic pollution, the latter due to the very high density of population in the Nainital valley, are the primary sources of enhanced parameters. The low pH of Nainital Lake water is due to low photosynthesis and enhanced respiration, increasing CO₂ in the water and the consequent enhancement of Ca²⁺ and HCO ₃ ⁻ . The dissolved oxygen in Nainital Lake is less compared to other lakes, indicating anoxic conditions developing at the mud–water interface at depth. The PO ₄ ³⁻ content in Nainital is higher (124 μg/l), showing an increasing trend over time leading to eutrophic conditions. The trace metals (Cu, Co, Zn, Ni, Mn, and Sr) are present in greater amounts in the water of Nainital Lake than in the other three lakes, though Fe and Cr are high in Bhimtal and Fe in Naukuchiyatal. The higher abundance is derived from the leaching of Fe–Mg from metavolcanic and metabasic rocks. Most of the heavy metals (Cr, Ni, Cu, Mn, Fe, Sr, and Zn) significantly enrich the suspended sediments of the lakes compared to the bed sediments which due to their adsorption on finer particles and owing to multiple hydroxide coating and organic content, except for Fe, which is enriched in the bed sediments. The high rate of sedimentation, 11.5 mm/year in Nainital, compared to Bhimtal with 4.70 mm/year, Naukuchiyatal with 3.72 mm/year, and Sattal with 2.99 mm/year, has resulted in shorter residence time, poor sorting of grains, and lesser adsorption of heavy metals, leading consequently, their depletion in the bed sediments of Nainital Lake.  相似文献