Field Comparison of Analytical Results from Discrete-Depth Ground Water Samplers     

Dawn A. Zemo  Thomas A. Delfino  John D. Gallinatti  Virgil A. Baker  Laurence R. Hilpert 《Ground Water Monitoring & Remediation》1995,15(1):133-141

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SERIAL PUBLICATIONS FOR GEOGRAPHICAL RESEARCH ON COMMUNIST CHINA FROM HONG KONG     

Laurence J. C. Ma 《The Professional geographer》1969,21(1):38-39

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Society news     

G. C. Amstutz  Robert A. Laurence 《Mineralium Deposita》1971,6(3):262-264

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A closer look at regime shifts based on coastal observations along the eastern boundary of the North Pacific     

Laurence C. Breaker 《Continental Shelf Research》2007

At least six regime shifts have been reported in the North Pacific since 1920. They occurred in 1925, 1939, 1946, 1976–1977, 1989 and 1999. The major change in 1976–1977 corresponds to a regime shift that is now widely accepted as a canonical event since it had a significant impact on virtually all climatic and ecosystem indicators. We seek to determine if daily sea surface temperature (SST) from Pacific Grove, in central California, and Scripps Pier, in southern California, and coastal observations from several other locations along the west coast of North America can be used to detect and resolve these events. Cumulative sums (CUSUMs) were initially calculated to enhance the detection process. The CUSUM trajectories during the 1976–1977 event at Pacific Grove and Scripps Pier were distinctive, highly correlated, and in phase. The turning point patterns from this event were then used to search for other events that have been reported since 1920. Turning point patterns very similar to the 1976–1977 event were detected in 1946 and 1989. The events in 1925 and 1939 were generally similar, but the CUSUM patterns for the event in 1999 departed significantly from the other events. Further examination of the 1976 and 1989 events revealed inflection points in the CUSUMs near the beginning and end of each transition that correspond to critical values or extrema in the original data. The inflection points and/or critical values provide an improved basis for determining the duration of these events.  相似文献   

Episodic mineralization of hydrothermal illite in the Soultz-sous-Forêts granite (Upper Rhine Graben, France)     

Anja M. Schleicher  Laurence N. Warr  Bernd Kober  Emmanuel Laverret  Norbert Clauer 《Contributions to Mineralogy and Petrology》2006,152(3):349-364

Episodic and localized illite mineralization is documented in the hydrothermally altered Soultz-sous-Forêts granite (Upper Rhine Graben, France). Separated grain-size fractions of altered granite and argillite vein samples contain mixtures of 2M₁ and 1M trans-vacant illite varieties. The platy pseudohexagonal 2M₁ illite phases dominate the vein fillings, whereas the 1M illite occurs largely as a fibrous pore-filling variety, which is particularly abundant in the granite matrix. Multiple phases of fluid injections into the granite body have resulted in different illite assemblages, each sample containing a mixture of polytype generations formed during different crystal growth events. On the basis of mineralogical and K–Ar isotopic constraints, the ages of these vein-mineralizing events are determined by plotting the K–Ar values of the various grain-size fractions against polytype abundance and the fitted volume-weighted crystallite thickness distributions. The results suggest a Permian age for the formation of the studied argillite veins, characterized by successive injections of hydrothermal fluids. Secondary episodes of illite crystallization occurred during Jurassic and Cretaceous (or even younger times) in both the veins and the granite matrix. There are indications that the polytype structure and composition of illite were strongly influenced by variations in fluid chemistry and the degree of fluid–rock interaction as the granite was progressively sealed during post-Variscan, episodic hydrothermal activity.  相似文献   

Degradation of methyl bromide and methyl chloride in soil microcosms: Use of stable C isotope fractionation and stable isotope probing to identify reactions and the responsible microorganisms     

Laurence G Miller  Karen L Warner  Ronald S Oremland  Stefan Radajewski 《Geochimica et cosmochimica acta》2004,68(15):3271-3283

Bacteria in soil microcosm experiments oxidized elevated levels of methyl chloride (MeCl) and methyl bromide (MeBr), the former compound more rapidly than the latter. MeBr was also removed by chemical reactions while MeCl was not. Chemical degradation dominated the early removal of MeBr and accounted for more than half of its total loss. Fractionation of stable carbon isotopes during chemical degradation of MeBr resulted in a kinetic isotope effect (KIE) of 59 ± 7‰. Soil bacterial oxidation dominated the later removal of MeBr and MeCl and was characterized by different KIEs for each compound. The KIE for MeBr oxidation was 69 ± 9‰ and the KIE for MeCl oxidation was 49 ± 3‰. Stable isotope probing revealed that different populations of soil bacteria assimilated added ¹³C-labeled MeBr and MeCl. The identity of the active MeBr and MeCl degrading bacteria in soil was determined by analysis of 16S rRNA gene sequences amplified from ¹³C-DNA fractions, which identified a number of sequences from organisms not previously thought to be involved in methyl halide degradation. These included Burkholderia, the major clone type in the ¹³C-MeBr fraction, and Rhodobacter, Lysobacter and Nocardioides the major clone types in the ¹³C-MeCl fraction. None of the 16S rRNA gene sequences for methyl halide oxidizing bacteria currently in culture (including Aminobacter strain IMB-1 isolated from fumigated soil) were identified. Functional gene clone types closely related to Aminobacter spp. were identified in libraries containing the sequences for the cmuA gene, which codes for the enzyme known to catalyze the initial step in the oxidation of MeBr and MeCl. The cmuA gene was limited to members of the alpha-Proteobacteria whereas the greater diversity demonstrated by the 16S rRNA gene may indicate that other enzymes catalyze methyl halide oxidation in different groups of bacteria.  相似文献   

人文主义与后现代化主义之兴起及西方新区域地理学之发展   总被引：50，自引：5，他引：45  

马润潮 《地理学报》1999,54(4):365-372

近４０年来,西方人文地理学发生了巨大的变化。５０年代末期开始计量革命。７０年代初开始,人文主义、行为主义、结构主义与后现代化主义等观念涌现,它们对西方地理界起了不同程度的影响。演变至今,人文地理学可说是一个百花齐放的多元化时代。人文主义与后现代化主义在７０年代与８０年代期间,先后出现于西方地理学。二者与上列其他观点有根本不同。在地理学上,它们强调各地情况都有其特性。同时,批判性的社会理论也在地理学  相似文献   

The mercury “tromol” mill: an innovative gold recovery technique, and a possible environmental concern     

Laurence P. James 《Journal of Geochemical Exploration》1994,50(1-3)

In Indonesia and other developing countries, an ingenious pebble mill and amalgamation drum serves both for gold production and bulk sample assay. Known as “tromol” mills, these locally-fabricated devices are carried to remote mountain areas for frontier small-scale mining and basic prospecting. Many hundreds of tromol drums now turn at plants in rural areas.The steel drum is filled with a standard quantity of rock, topped with hard river cobbles, and rotated by an engine or water power. Mercury, imported illegally at high cost, is added to amalgamate gold and silver Waste, containing any lost mercury, typically washes into streams. Limited studies in North America and Russia suggest some biological uptake occurs from metallic mercury lost long ago by obsolete gold processing methods. Levels regarded as hazardous are noted in river fish in Nevada and Quebec, but no major health problems are attributed to mercury from gold mining in temperate climate regions. No published data on mercury discharges in Indonesia was found. Application of simple metallurgical techniques at Indonesian mining camps could greatly decrease mercury (and probably also gold) loss.  相似文献   

Terrigenous input response to glacial/interglacial climatic variations over southern Baja California: a rock magnetic approach     

Ccile L. Blanchet  Nicolas Thouveny  Laurence Vidal  Guillaume Leduc  Kazuyo Tachikawa  Edouard Bard  Luc Beaufort 《Quaternary Science Reviews》2007,26(25-28):3118-3133

The sediments deposited off south-western Baja California have recorded millennial-scale fluctuations in biogenic compounds and trace metals accumulation during the last glacial period [Ortiz, J.D., O’Connell, S.B., DelViscio, J., Dean, W.E., Carriquiry, J.D., Marchitto, T., Zheng, Y., van Geen, A., 2004. Enhanced marine productivity off western North America during warm climate intervals of the past 52 ky. Geology 32, 521–524; Dean, W.E., Zheng, Y., Ortiz, J.D., van Geen, A., 2006. Sediment Cd and Mo accumulation in the oxygen-minimum zone off western Baja California linked to global climate over the past 52 ka. Paleoceanography 21, PA4209]. Since the variations in trace metals concentration appear to result from dilution with nonbiogenic matter, the variability of the terrigenous sedimentation needs to be addressed. Therefore, we performed rock magnetic and geochemical analysis on a 38 m-long sediment core collected from the slope off Baja California. The temporal framework provided by ¹⁴C dating and identification of palaeoclimatic transitions allows assigning the sequence to the last glacial–interglacial cycle (last 120 ka). The comparison of magnetic and geochemical properties led to retain the hypothesis of a primary modulation of iron oxides quantity and quality by terrigenous input variations, with a secondary diagenetic amplification. Two magnetic mineral input regimes are distinguished: (i) magnetic susceptibility variations reveal changes in titano-magnetite concentration related to fluvial transport of the terrigenous fraction; (ii) coercivity changes allow detecting variations of hematite or goethite concentrations, minerals generally issued from aeolian deflation of weathered rock surfaces. These two regimes are paced by two distinct climatic forcing: the millennial-scale changes in titano-magnetite input are related to the northern hemisphere climatic variability whilst the record of wind-blown magnetic mineral input contains its major power in the precessional frequency band, with higher input during low insolation periods (and conversely). This record highlights the great sensibility of this region to high and low latitudes climatic regimes.  相似文献   

Evidence of the theoretically predicted seismo-magnetic conversion     

Clarisse Bordes  Laurence Jouniaux  Stéphane Garambois  Michel Dietrich  Jean-Pierre Pozzi  Stéphane Gaffet 《Geophysical Journal International》2008,174(2):489-504

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