土壤、大气尘中晶体的组成及其物源指示意义——以长沙、株洲和湘潭地区为例     

张广平吴堑虹  戴塔根方建武张建新  徐海珍苏调红 《地质通报》2007,26(11):1459-1462

基于长沙、株洲和湘潭地区大气尘(可吸入颗粒和近地表积尘)和表层土壤的X-射线衍射(XRD)分析数据,采用微量相鉴定方法获得的结果显示,大气尘和表层土壤中包含石英、石膏、方解石、白云石、硫酸镉等自然矿物及SiS_2、NiTi、Cd_3As_2、FeOCl等非自然源晶体。比较了长沙、株洲、湘潭地区大气尘与表层土壤的晶体组成,分析了大气尘矿物及非自然源晶体的空间分布,探讨了其环境指示意义。  相似文献   

Variations in dust event frequency over the past century reflected by ice-core and lacustrine records in north China   总被引：1，自引：0，他引：1  

WANG NingLian    YAO TanDong    YANG XiangDong  SHEN Ji & WANG Yong Key Laboratory of Cryosphere  Environment  Cold  Arid Regions Environmental  Engineering Research Institute  Chi- nese Academy of Sciences  Lanzhou  China  Institute of Tibetan Plateau Research  Chinese Academy of Sciences  Beijing  China  Nanjing Institute of Geography  Limnology  Chinese Academy of Sciences  Nanjing  China 《中国科学D辑(英文版)》2007,50(5):736-744

In this paper, we analyzed the variations of dust proxies in the Dunde, Malan and Chongce ice cores from the northern Tibetan Plateau and the Hongjiannao lacustrine sediment core from north Shaanxi Province, and found that they all showed a general decrease trend over the past century. Owing to the fact that all these ice cores and lacustrine core were retrieved from the margins and/or the leeward sides of the major areas of dust events in north China, their records could suggest that the dust event frequency in north China declined over the study period. This decrease trend might be attributed to increasing precipitation and weakening westerly. However, human activities have made the areal extent of desertification expand acceleratingly in north China. This status could make it possible that dust events would occur on a large spatial scale under the future climate change, which would be a big environmental issue we shall face.  相似文献   

塔克拉玛干沙漠腹地沙尘暴发生条件分析   总被引：4，自引：0，他引：4       下载免费PDF全文

李生宇雷加强  徐新文 《应用气象学报》2007,18(4):490-496

利用塔中气象站1997—2002年的气象资料, 从沙尘源丰富程度、风动力条件和空气稳定度等方面分析了塔克拉玛干沙漠腹地沙尘暴的成因。结果表明:在塔克拉玛干沙漠腹地, 沙尘源极为丰富, 为沙尘暴发生提供了必要条件, 降水基本不能改变沙面的湿润状况, 沙尘源丰富度不是沙尘暴发生的限制因子; 风动力是沙尘暴发生的重要条件, 而月平均风速和大风日数是风动力的重要定量表征指标; 空气稳定性也是沙尘暴发生的重要条件, 温度和天气过程是其重要标志, 沙尘暴发生与温度呈正相关, 沙尘暴多发生在夏季和午后; 降水是沙漠腹地天气过程的重要指标, 月降水日数和降水总量与沙尘暴日数呈正相关; 20世纪90年代以来沙尘暴逐年减少, 这种变化趋势可能与全球气候变化有关。  相似文献   

The expulsion and retention of dust grains by galactic discs     

J. I. Davies  P. Alton  S. Bianchi  & M. Trewhella 《Monthly notices of the Royal Astronomical Society》1998,300(4):1006-1014

We have constructed a numerical model of a galaxy that consists of a stellar, gas and dust disc imbedded within a dark halo. We have used this model to assess the radiation, gravitational and viscous forces on dust grains and to trace their motion through the interstellar medium over a period of 10⁹ yr. We conclude that the disc opacity is a crucial factor in understanding the motion of the grains. Large grains (≈0.1 μm) with low disc opacity will lead to dust expulsion from the stellar disc, while high opacity leads to dust retention. Reasonable disc opacities lead to the recycling of the larger grains from the outer to the inner regions of the galaxy. The larger grains travel at higher velocities than small grains (0.01−0.001 μm), and so the smaller grains remain relatively close to their formation sites. Dust can 'leak' out over the entire surface of the disc because of the imbalance of radiation and gravitational forces. The dust is dynamically coupled to the gas and so although the gas lags behind the dust it is carried along with it. This explains the close correlation between the far-infrared emission from dust and the gas column density. We use a simple analytical model to show how the dust mass of a galaxy may evolve with time and how a significant fraction (90 per cent) of the total dust mass produced may have been expelled into the intergalactic medium.  相似文献   

太阳系尘埃等离子体研究   总被引：1，自引：0，他引：1  

石志东  李中元 《天文学进展》1998,16(3):227-236

综述了太阳系尘埃等离子体中的充电机制和波动过程以及与之有关的若干空间物理现象,内容包括太阳系等离子体中尘埃表面的平衡电势,带电尘埃在空间环境中的受力与运动,行星环内沿的弥漫扩散,轮辐结构的成困,彗星环境中尘埃的静电爆裂,尘埃彗尾的形态演化,天王星窄环的稳定性等问题．  相似文献   

甘肃河西走廊沙尘暴与赤道中,东太平洋海温之间的遥相关分析   总被引：34，自引：14，他引：20  

尚可政  孙黎辉 《中国沙漠》1998,18(3):239-243

春、夏季甘肃河西走廊沙尘暴发生次数与赤道中、东太平洋海温之间遥相关分析结果表明：春、夏季河西走廊沙尘暴发生次数与前二年赤道中、东太平洋海温的负相关最好,时间过远或过近,相关性反而较差。利用前期的赤道中、东太平洋海温可以较好地预报出河西走廊春季沙尘暴发生的多寡。  相似文献   

吉林省南部宇宙尘的化学组成特征     

王志华  林文蔚 《地球化学》1998,27(5):465-474

在吉林省南部元古宇石英岩内发现磁性微球粒３９２枚,根据其产状,形貌及一般特征,微结构和化学组成表明为陨石消融型宇宙尘,由４亚４小类组成一个宇宙尘系列,（１）金属球粒;（２）纯铁球粒,（ｂ）ＦＣＮ型（天然不锈钢）球粒;（２）氧化物球粒（ａ）普通铁质宇宙尘（ｂ）铬铁氧化物球粒;（３）玻璃质球粒;（４）氧化物－金属过渡型球粒,其母体要能是一分异的ＦＣＮ型石－铁陨石质陨星体,核部为ＦＣＮ合金,经消融分异作  相似文献   

我国极端干旱区边缘阿羌砂尘堆积剖面的地质时代   总被引：11，自引：0，他引：11  

李保生  李森 《地质学报》1998,72(1):83-92

根据对昆仑山北麓阿羌地区第四纪风成砂尘沉积物的调查、地层对比和107组古地磁标本(321块样品)的测定结果认为,阿羌地层剖面记录了Brunhes时以来我国极端干旱区最完整的风成砂尘堆积序列;剖面中间冰期形成的生草层1PE和细粒风尘堆积29FGL、31FGL、33FGL、35FGL、37FGL、39FGL、42FGL在形成的地质时代上可依次与黄土高原古土壤S_0、S_1、S_2、S_3、S_4、S_5、S_6、S_7进行对比,而与1PE和细粒风尘堆积29FGL、……、42FGL互为叠覆的冰期气候形成的风成极细砂和粗粒风尘堆积则可与黄土高原黄土L_1、……、L_8进行对比。此外,在阿羌剖面砂尘堆积底部42FGL层中发现有0.7 Ma B P前的宇宙尘埃物质,这对于该地风成砂尘下限年代的确定、研究极端干旱区气候的发展历史和晚新生代地外灾变事件的对比具有重要意义。  相似文献   

Red quasars not so dusty     

C. R.Benn  M.Vigotti  R.Carballo  J. I.Gonzalez-Serrano  S. F.SÃ&#;¡nchez 《Monthly notices of the Royal Astronomical Society》1998,295(2):451-456

Webster et al. claimed that up to 80 per cent of QSOs may be obscured by dust. They inferred the presence of this dust from the remarkably broad range of B − K optical–infrared colours of a sample of flat-spectrum PKS radio QSOs. If such dust is typical of QSOs, it will have rendered invisible most of those which would otherwise have been detected by optical surveys. We used the William Herschel Telescope on La Palma to obtain K infrared images of 54 B3 radio QSOs selected at low frequency (mainly steep-spectrum), and we find that although several have very red optical–infrared colours, most of these can be attributed to an excess of light in K rather than a dust-induced deficit in B. We present evidence that some of the infrared excess comes from the light of stars in the host galaxy (some, as previously suggested, comes from synchrotron radiation associated with flat-spectrum radio sources). The B − K colours of the B3 QSOs provide no evidence for a large reddened population. Either the Webster et al. QSOs are atypical in having such large extinctions, or their reddening is not due to dust; either way, the broad range of their B − K colours does not provide evidence that a large fraction of QSOs has been missed from optical surveys.  相似文献   

Diffuse interstellar bands in low E (B – V) objects     

G.A. Galazutdinov  J. Krelowski  C. Moutou  F.A. Musaev 《Monthly notices of the Royal Astronomical Society》1998,295(2):437-442

We analyse spectra of slightly reddened, early-type stars in which the major diffuse interstellar bands at 5870 and 5797 Å are either strong or weak in relation to E(B – V) . It is demonstrated that among the low E(B – V) objects one can find stars obscured by 'sigma' as well as 'zeta' type clouds. The profiles of the diffuse bands seem not to be dependent on the total opacities of the interstellar clouds. We also discuss the physical conditions leading to the formation of the diffuse band carriers in low-opacity interstellar clouds; the carriers are apparently formed in media in which one can observe complex velocity fields.  相似文献