The dry dredgers of Cincinnati, Ohio, USA     

President  JACK W. KALLMEYER & Professor of Geology  DAVID L. MEYER 《Geology Today》1997,13(6):228-230

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Baryte and calcite cements in the 'breccias' of Ogmore-by-Sea, South Wales     

CHRIS W. LEE 《Geology Today》1991,7(4):133-136

Each year many hundreds, if not thousands, of Earth-science students visit the coastline at Ogmore-by-Sea, mid-Glamorgan. They study the excellent exposures of Lower Carboniferous Limestone, with their well-preserved coral and other shelly faunas, together with the presumed late Triassic 'breccias'* that rest unconformably on top. A study of the cements within the breccias may give an insight into syndepositional mineralization and the formation of sedimentary basins linked to the opening of the Atlantic in early Mesozoic times.  相似文献   

A three-dimensional large-scale cloud model: testing the role of radiative heating and ice phase processes     

J. L. LEE  K. N. LIOU  S. C. OU 《地球，A辑:动力气象学与海洋学》1992,44(3):197-216

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针式微萃取结合GC-IRMS测定水溶液中甲酸、乙酸的稳定碳同位素组成     

李心清  黄代宽  章炎麟  江伟  安宁  胡璐  徐刚 《地球化学》2008,37(6)

甲酸和乙酸稳定碳同位素组成（δ^13C）的分析对环境、食品、制药和自然产品等的研究具有重要的应用价值。但目前尚缺乏有效的测定方法。本研究利用最近出现的针式固相微萃取技术（NeedlEX）,以吹扫．捕集方式对水溶液中的有机酸进行了萃取,然后利用气相色谱．同位素比值质谱联用仪（GC—IRMS）对所萃取的有机酸分子进行了占δ^13C的测定。结果显示,质谱计的信号强度与水溶液中有机酸的浓度存在显著的线性相关关系（R^2〉0．99,P〈0．05）,表明Needl EX对水溶液中有机酸具有稳定的萃取能力。在甲酸与乙酸含量分别不低于300μg／mL与200μg／mL的水溶液中,1000mL的吹扫体积可以使两者δ^13C多次分析结果的相对误差分别保持在3％和1％左右,且整个实验流程没有造成可检测的碳同位素分馏作用。低于这两个浓度界线,则分析误差随浓度的降低迅速增加。本研究虽然是针对水溶液中有机酸δ^13C的测定,其萃取方法对其他水溶性挥发和半挥发有机物δ^13C的分析也同样具有应用价值。  相似文献   

Ammonium nitrogen in surface soil of arid and semiarid Central East Asia     

HU Lu  LEE Xin-qing  HUANG Dai-kuan  CHENG Jian-zhong 《地球化学》2008,37(6)

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淡水双壳类壳体碳同位素研究:以河蚬(corbicula fluminea,Müller 1774)为例   总被引：2，自引：0，他引：2  

闫慧  李心清  周会 《地球化学》2008,37(3)

双壳类壳体碳酸盐(文石)稳定同位素组成已被广泛地用于古气候和古环境重建研究中,但是双壳类壳体碳同位素组成所指示的气候和环境意义一直是争议的问题.对双壳类河蚬(corbicula fluminea)进行了室内养殖,并选取两个壳体样品(壳高,A=13 mm,B=9mm),测定其生长部分壳体和生长期间水体碳同位素,研究表明,随着水体碳同位素的升高(δ13CDIC由-5.24‰升至1.41‰),两壳体碳同位素也随之升高,表明水体对壳体碳同位素的影响;δ13CA分布范围为-4.76‰～2.09‰,δ13CB为-8.49‰～2.89,壳体A和B碳同位素均比预测平衡值偏负,表明壳体在形成过程中利用了新陈代谢产生的富集12C的CO2.根据计算壳体A在实验中沉淀部分壳体利用新陈代谢碳的比例(M值)为24%～43%,平均值为33%;壳体B为33%～75%,平均值为58%.M值随生物的生长呈下降变化,这说明在实验中河蚬主要是通过增加对DIC的吸收和利用来满足壳体生长对物质量增加的需求.  相似文献   

Jarosit KFe3(S04)2(OH)6 aus Stassfurter Carnallit     

Professor Dr. . Braitsch  Dr. K. Keil 《Contributions to Mineralogy and Petrology》1965,11(3):247-249

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Zur Luftverunreinigung durch turbulente Diffusion     

Professor Dr. H. Reuter  Dr. K. Cehak 《Meteorology and Atmospheric Physics》1965,15(2):192-204

Zusammenfassung Nach einer kurzen Diskussion der theoretischen Grundlagen für die Berechnung der Ausbreitung von schädlichen Beimengungen der Luft auf Grund der Gesetzmäßigkeiten der turbulenten Diffusion wird mit Hilfe der vonPasquill angegebenen empirischen Beziehungen zwischen Streuungsmaßen und Quelldistanz die Formel für die Immissionskonzentration am Boden abgeleitet. An Hand einer Reihe von Beispielen wird das Bodenkonzentrationsfeld relativ zu dem Punkt maximaler Immissionskonzentration berechnet, wobei eine feste Schornsteinhöhe von 40 m und eine für mittlere Emittenten zutreffende Auswurfmenge an schädlichen Gasen vorausgesetzt wird. Die Abbildungen zeigen die starke Modifikation des Konzentrationsfeldes durch die meteorologischen Verhältnisse, je nachdem, ob ein stabiler, indifferenter oder labiler Ausbreitungstyp vorliegt.

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Summary After a short discussion of the theoretical background for the calculation of the spreading of the noxious pollutants of the air based on the laws of turbulent diffusion a formula is derived for the concentration of the immisison on the ground with help of the empirical relations between the dispersion measures and the distance from the source given byPasquill. In some examples the concentration field at the ground relative to the point of maximum immission is calculated, considering a fixed height of the funnel of 40 m and a quantity of noxious gases as usually found with average emittents. The figures show a strong modification of the concentration field by the meteorological situation according to whether the spreading type is stable, indifferent or unstable.

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Résumé On discute tout d'abord brièvement les fondements théoriques permettant de calculer la propagation des pollutions atmosphériques; pour ce faire, on se base sur les lois de la diffusion turbulente. On en tire ensuite une formule de calcul de la concentration des immissions à l'aide des relations empiriques dePasquill, relations existant entre les quantités répandues et la distance de la source. On calcule au moyen d'une série d'exemples le champ des concentrations au sol par rapport au point de concentration maximum; pour ce faire, on admet und chemineé fixe de 40 mètres de hauteur et une quantité de gaz nocifs correspondant à une moyenne de polluants. Les figures montrent la forte modification que subit la répartition des concentrations selon les conditions météorologiques, en d'autres termes si l'on a affaire à un type de propagation stable, indifférent ou instable.

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An investigation of the size frequency resolution of an aerosol by the static method of diffusion     

Professor of Experimental Physics Gerard McGreevy 《Pure and Applied Geophysics》1966,63(1):220-230

Summary Theoretical considerations are put forward for identifying the Dynamic and Static Methods of Diffusion measurements of aerosol particles. On the basic of this equality the Exhaustion Method of Diffusion developed byPollak andMetnieks for the size-frequency resolution of a heterogeneous aerosol by Dynamic Diffusion Methods should be applicable to Static Methods. This hypothesis is tested using a Pollak-Nolan nucleus counter as decay vessel. It is shown that turbulence in the counter is the most serious obstacle against this type of approach to finding the size components of an aerosol. The time involved, the high humidity in the counter and a hypothetical nucleus-free zone are other major difficulties for relatively large Aitken nuclei. It is established, however, that for particles whose diffusion coefficient is of the order of 10^–3 cm² sec^–1, the proposed method should be quite workable.  相似文献   

Numerical Experiment on Two-Dimensional Line Thermal     

J.H.W.LEE  G.Q.CHEN 《中国海洋工程》2002,16(4):453-467

The time evolution of a two-dimensional line thermal-a turbulent flow produced by an initial element with signifi-cant buoyancy released in a large water body, is numerically studied with the two-equation k - e model for turbulence closure. The numerical results show that the thermal is characterized by a vortex pair flow and a kidney shaped concentra-tion structure with double peak maxima; the computed flow details and scalar mixing characteristics can be described by self-similar relations beyond a dimensionless time around 10. There are two regions in the flow field of a line thermal: a mixing region where the concentration of tracer fluid is high and the flow is turbulent and rotational with a pair of vortex eyes, and an ambient region where the concentration is zero and the flow is potential and well-described by a model of doublet with strength very close to those given by early experimental and analytical studies. The added virtual mass coeffi-cient of the thermal motion is found to be approximat  相似文献