Sulphur contents of conifer needles in Great Britain     

John L. Innes Dr.  Roger C. Boswell 《GeoJournal》1989,19(1):63-66

There is currently a lack of convincing evidence linking air pollution and tree health in Great Britain. Field surveys have not revealed a clear association between the spatial distribution of crown thinning and air pollution; the crown condition of some species is apparently better in more polluted areas. This has been attributed to the confounding effects of climate, which is known to have a marked effect on crown condition. In this study, analysis of total sulphur contents of needles ofPicea sitchensis ((Bong.) Carr.),P. abies ((L.) Karst.) andPinus sylvestris (L.) reveals marked patterns that are correlated with modelled atmospheric concentrations of sulphur dioxide. Correlations with other indices of sulphur pollution, including wet and dry deposition and sulphate aerosol concentrations, are less consistent. However, no association has been found between the sulphur contents of needles and the crown densities of trees in Britain.  相似文献   

地震尾波的某些特性的探讨          下载免费PDF全文

顾瑾平  虞雪君  吕广庭  盛国英 《地震工程学报》1985,7(2):31-39

本文在对人工地震资料的尾波特性进行探讨的基础上,进一步以天然地震的资料为对象,讨论了尾波振幅衰减特性α的变化情况和尾波频率随时间的变化特性。天然地震的资料分两类,一是用本区(强震震源区)发生的小震资料,二是用外区(强震震源区以外)发生的中小震资料。两类地震均由同一组台站记录。通过一些天然地震震例的分析、对此,可得到以下结果: (1)对尾波散射区的考虑。(2)尾波特征参量携带强震前兆信息的可能性。(3)不同物量参量变化一致性的初步认识。(4)天然地震源,人工地震源、实验三者的尾波参量随时间变化的良好吻合。(5)品质因素相对变化趋势的简易估计。不可否认方法的局限性及各种干扰因素的存在。  相似文献   

On inertial currents over a sloping continental shelf     

Roger L. Hughes 《Dynamics of Atmospheres and Oceans》1985,9(1):49-73

Using simple mathematical models, it is shown that an equatorward flowing coastally confined eastern boundary current (or poleward flowing western boundary current) may have two conjugate forms which transport the same flux of each water type. In a slowly varying environment, these two conjugate forms coalesce at some critical latitude which depends on the flow. For lower latitudes there is no defined form. As the coalescence latitude is approached from higher latitudes, one of the two conjugate forms narrows, while the other widens. Furthermore, in the neighborhood of the critical latitude the wider form is subcritical and the narrower form is supercritical to possible long small amplitude shelf waves. It is also shown that a poleward flowing coastally confined eastern boundary current (or an equatorward flowing western boundary current) may be traced poleward to some critical latitude beyond which the possibility of a current in juxtaposition with the coast terminates. For latitudes higher than this terminating latitude the current separates from the coast.  相似文献   

A method for the elimination of the compositional dependence of trace element distribution coefficients     

Roger L. Nielsen 《Geochimica et cosmochimica acta》1985,49(8):1775-1779

In an investigation of Sm, Sc, Sr, and Ti partitioning between diopside and silicate melt, Rayet al. (1983) showed that the compositional dependence of multicomponent exchange equilibria can not be eliminated by the application of the melt model of Bottinga and Weill (1972), and that the propagation of analytical error is an important contributor in the observed internal error in the calculated equilibria for those exchange reactions. We can demonstrate that the compositional dependence of single component distribution coefficients can be reduced below analytical error by the application of the two-lattice melt model first reported by Nielsenand Drake (1979) in a study of major element partitioning between pyroxene and melt. This model was later used for the calculation of major, minor and trace element partitioning by Nielsen and Dungan (1983). The two-lattice model is a modified version of the Bottinga-Weill model used by Drake (1976) for plagioclase-melt equilibria, and differs from that model in the assumed role of Al. The Nielsen and Dungan (1983) model has been modified here to assume Ti to mix in silicate melts as a network former. Single component distribution coefficients were used in place of multicomponent reactions in order to reduce the propagated analytical and experimental error.  相似文献   

1986年门源6.4级地震前的波速比异常与模糊数学方法的应用          下载免费PDF全文

顾瑾平  虞雪君  李清河  盛国英  闵祥仪  侯晓玉 《地震工程学报》1987,9(3):103-106

1986年8月23日门源6.4级地震前,地震波速度比异常从1984年起即开始出现,异常过程中由于受1985年7月14日冷龙岭3.6级地震的影响而略有回升,以后继续呈负异常,最大幅度达7%。震前在震中以西地区的波速比值未出现回升以后的明显高值,而震中以东的九条岭地区虽然长趋势波速比值负异常不明显,但震前的趋势上升及高值的出现却十分清楚。  相似文献   

Tectonics of the Nazca-Antarctic plate boundary     

Sandra Anderson-Fontana  Joseph F. Engeln  Paul Lundgren  Roger L. Larson  Seth Stein 《Earth and Planetary Science Letters》1987,86(1)

We have constructed a new bathymetric chart of part of the Chile transform system, based mainly on an R/V “Endeavor” survey from 100°W to its intersection with the East Ridge of the Juan Fernandez microplate at 34°30′S, 109°15′W. A generally continuous lineated trend can be followed through the entire region, with the transform valley being relatively narrow and well-defined from 109°W to approximately 104°30′W. The fracture zone then widens to the east, with at least two probable en echelon offsets to the south at 104° and 102°W. Six new strike-slip mechanisms along the Chile Transform and one normal fault mechanism near the northern end of the Chile Rise, inverted together with other plate motion data from the eastern portion of the boundary, produce a new best fit Euler pole for the Nazca-Antarctic plate pair, providing tighter constraints on the relative plate motions.  相似文献   

Perspectives for research in wet chemistry and unintentional cloud modification from the discipline of purposeful cloud modification     

Roger F. Reinking 《Boundary-Layer Meteorology》1987,41(1-4):381-405

Fundamental goals and scientific problems facing researchers in purposeful cloud modification and applicable to air quality pertaining to unintentional cloud modification are defined. These encompass experimental design and verification, transport and dispersion, aerosol and hydrometeor evolution and removal, and the interactive nature of chemical, microphysical, dynamical and other cloud processes on micro- to mesoscales. Some recent advances in purposeful weather modification are reviewed and parallels are drawn to wet chemistry and unintentional cloud modification. Gains to be made in further cross-fertilization of the disciplines are suggested.Paper originally presented at the International Conference on Energy Transformations and Interaction with Small and Mesoscale Atmospheric Processes. Lausanne, Switzerland, 2–6 March 1987.  相似文献   

Alkyl nitrate formation from the reaction of a series of branched RO2 radicals with NO as a function of temperature and pressure     

Roger Atkinson  Sara M. Aschmann  Arthur M. Winer 《Journal of Atmospheric Chemistry》1987,5(1):91-102

Alkyl nitrate yields from the NO _x photooxidations of neopentane, 2-methylbutane and 3-methylpentane have been determined over the temperature and pressure ranges 281–323 K and 54–740 torr, respectively. The formation of the alkyl nitrates is attributed to the reaction pathway (1b) $${\text{RO}}_{\text{2}} + {\text{NO}}^{{\text{ }}\underrightarrow {\text{M}}} {\text{ RONO}}_{\text{2}}$$ and rate constant ratios k _1b/(k _1a+k _1b) are estimated, where (1a) is the reaction pathway (1a) $${\text{RO}}_{\text{2}} + {\text{NO}} \to {\text{RONO}}_{\text{2}} .$$ A method for estimating this rate constant ratio for primary, secondary and tertiary alkyl peroxy radicals is presented.  相似文献   

Tectonics of the East Pacific Rise near 12°50′N: a submersible study     

Pierre Choukroune  Jean Francheteau  Roger Hekinian 《Earth and Planetary Science Letters》1984,68(1):115-127

Using the diving saucer “Cyana”, a portion of the East Pacific Rise between 12°38′ and 12°54′N has been studied and mapped. Four main zones are defined: (1) an active volcanic zone located in the central graben; the graben displays a variable relief along strike from less than 10 m up to 55 m and has an en-échelon pattern in plan view; (2) an active tectonic zone comprising the central graben and extending up to about 2 km from either side of the rise axis; (3) an inactive tectonic zone starting 2 km away from the axis and formed by discontinuous horst and graben type of structures; and (4) off-axis volcanoes (seamounts) located less than 20 km on either side of the rise axis. At 12°50′N, the active tectonic zone is extremely narrow and the mode of deformation is through fissuring in strong contrast with that observed in slow or intermediate rate ridges. The presence or absence of a magma reservoir at shallow depth explains the difference in the width of the active tectonic zone. The state of isostatic equilibrium or lack of equilibrium explains the different modes of deformation.  相似文献   

Chemical characteristics of minerals in ultrabasic rocks and their relations to metallogenesis     

Peng Gu 《中国地球化学学报》1984,3(4):355-363

The most productive chromite ore deposits are formed through crystallization of chromite-ore magmas under definite physico-chemical conditions. The formation of chromite ore is controlled mainly by the degree of differentiation of ultrabasic magma. How to measure the degree of ultrabasic magmatic differentiation is key to understanding the mechanism of formation of chromite ore. Many geologists base their understanding of ultrabasic magmatic differentiation on whether there are obvious petrographical-facies zones in ultrabasic rocks. This viewpoint needs further discussing because most ultrabasic rock bodies showing petrographical zonation contain no mineral deposits. On the contrary mineral deposits may occur in the ultrabasic rocks without obvious petrographical zonation. Therefore, the author suggests to use the chemical characteristics of minerals to determine the degree of ultrabasic magmatic differentiation as a guide to search for chromite ore deposits.  相似文献