D/H ratios of atmospheric H₂ in urban air: results using new methods for analysis of nano-molar H₂ samples     

Thom Rahn  Nami KitchenJohn Eiler 《Geochimica et cosmochimica acta》2002,66(14):2475-2481

We present the results of a study of the concentration and D/H ratio of molecular hydrogen from air in the Los Angeles Basin and adjacent San Gabriel Mountains. These data define a mixing relationship in dimensions of D/H ratio vs. 1/(H₂) which constrains the δD_VSMOW of unpolluted winter air in this region to be ca. +100 to +125 ‰ and that of urban H₂ sources to be ca. −270 ‰. This study makes use of a new method for measuring the deuterium content of molecular hydrogen in small samples (∼100 to 500 cc) of air, which we describe in detail. The method consists of an off-line separation of H₂ followed by introduction to the mass spectrometer in a continuous flow of He. Off-line, all components of an atmospheric gas sample, with the exception of He, H₂, and Ne are condensed by exposure to a cold-trap held at 30 Kelvin. This separation is followed by cryo-transfer of non-condensable gases to a small volume molecular sieve finger, with assist from a mercury piston pump. At the mass spectrometer, the sample is put in line with a continuous flow of He where it is focused on to an additional column of molecular sieve before subsequent introduction into the ion source. Analyses of DH/H₂ ratio have accuracy and precision of ±4 to 7 per mil. Comparison of sample peak area to peak areas of standards of known size allows for determination of H₂ concentration with accuracy and precision of ∼±5%, relative. The method reduces sample size and processing time by several orders of magnitude compared to previous methods, allowing for sampling at proportionately higher spatial and temporal resolution.  相似文献   

Water quality impacts from mining in the Black Hills,South Dakota,USA   总被引：1，自引：0，他引：1  

P. H. Rahn  A. D. Davis  C. J. Webb  A. D. Nichols 《Environmental Geology》1996,27(1):38-53

The focus of this research was to determine if abandoned mines constitute a major environmental hazard in the Black Hills. Many abandoned gold mines in the Black Hills contribute acid and heavy metals to streams. In some areas of sulfide mineralization local impacts are severe, but in most areas the impacts are small because most ore deposits consist of small quartz veins with few sulfides. Pegmatite mines appear to have negligible effects on water due to the insoluble nature of pegmatite minerals. Uranium mines in the southern Black Hills contribute some radioactivity to surface water, but the impact is limited because of the dry climate and lack of runoff in that area.  相似文献   

Evaluating igneous sources of the Taveyannaz formation in the Central Alps by detrital zircon U–Pb age dating and geochemistry     

Gang Lu  Wilfried Winkler  Meinert Rahn  Albrecht von Quadt  Sean D. Willett 《Swiss Journal of Geoscience》2018,111(3):399-416

Late Palaeogene syn-tectonic volcanic products have been found in the Northern Alpine foreland basin and in the South Alpine hemipelagic basin. The source of abundant volcanic fragments is still in debate. We analyzed the geochronology and geochemistry of detrital zircons, and evaluated their temporal and genetic relationships with potential volcanic sources. The study shows that the detrital zircon U–Pb age patterns have two major age groups: a dominance (ca. 90%) of pre-Alpine zircons was found, as commonly observed in other Alpine flysch formations. These zircons apparently derived from erosion of the early Alpine nappe stack in South Alpine and Austroalpine units. Furthermore, a few Neo-Alpine zircons (ca. 10%) have ages ranging from Late Eocene to Early Oligocene (~ 41–29 Ma). Both source materials were mixed during long riverine transport to the basin margins before being re-deposited by gravity flows. These Palaeogene ages match with the activity of Peri-Adriatic magmatism, including the Biella volcanic suite as well as the Northern Adamello and Bergell intrusions. The values of REE and ¹⁷⁶Hf/¹⁷⁷Hf_(t) ratios of the Alpine detrital zircons are in line with the magmatic signatures. We observe an in time and space variable supply of syn-sedimentary zircons. From late Middle Eocene to Late Eocene, basin influx into the South Alpine and Glarus (A) basins from the Northern Adamello source is documented. At about 34 Ma, a complete reorganisation is recorded by (1) input of Bergell sources into the later Glarus (B) basin, and (2) the coeval volcaniclastic supply of the Haute-Savoie basin from the Biella magmatic system. The Adamello source vanished in the foreland basin. The marked modification of the basin sources at ~ 34 Ma is interpreted to be initiated by a northwestern shift of the early Alpine drainage divide into the position of the modern Insubric Line.  相似文献   

Hydrology and Chemistry of Thermal Waters Near Wells, Nevada     

Paul W. Jewell  Thomas A. Rahn  John R. Bowman 《Ground water》1994,32(4):657-665

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伊利石结晶度Kübler，Weaver和Weber指数关系式常数的确定与应用   总被引：1，自引：0，他引：1  

王河锦  陶晓风Rahn Meinert 《高校地质学报》2007,13(3):561-565

根据衍射峰具有的不同分布特点推导出了14个伊利石结晶度Kübler指数，Weaver指数和Weber指数关系式中常数项C1-C14的数值，提出了PearsonⅦ分布中形态参数μ与C5，C6，C11，C12的4个定量方程。由此，14个伊利石结晶度指数关系式可直接用于实际计算。根据阿尔卑斯复理石伊利石形态特征Sc=0.731，由这些关系式进行近变质带上下界线的转换得出与Kübler指数0.42～0.25。△2θ界线对应的Weaver指数和Weber指数的界线值分别为5.8～17.6和300～179。讨论了在自然干燥状态下直接进行伊蒙混层鉴定的基本原理。  相似文献   

Novel MVA tools to track CO<Subscript>2</Subscript> seepage,tested at the ZERT controlled release site in Bozeman,MT     

J. E. Fessenden  S. M. Clegg  T. A. Rahn  S. D. Humphries  W. S. Baldridge 《Environmental Earth Sciences》2010,60(2):325-334

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The Hydrogeology of an Induced Streambed Infiltration Area   总被引：1，自引：0，他引：1  

Perry H. Rahn 《Ground water》1968,6(3):21-32

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Generation of a stochastic precipitation model for the tropical climate     

Ng  Jing Lin  Abd Aziz  Samsuzana  Huang  Yuk Feng  Wayayok  Aimrun  Rowshon  MK 《Theoretical and Applied Climatology》2018,133(1-2):489-509

Theoretical and Applied Climatology - A tropical country like Malaysia is characterized by intense localized precipitation with temperatures remaining relatively constant throughout the year. A...  相似文献   

Isochron‐burial dating of glaciofluvial deposits: First results from the Swiss Alps          下载免费PDF全文

Naki Akçar  Susan Ivy‐Ochs  Vasily Alfimov  Fritz Schlunegger  Anne Claude  Regina Reber  Marcus Christl  Christof Vockenhuber  Andreas Dehnert  Meinert Rahn  Christian Schlüchter 《地球表面变化过程与地形》2017,42(14):2414-2425

In this study, we use isochron‐burial dating to date the Swiss Deckenschotter, the oldest Quaternary deposits of the northern Alpine Foreland. Concentrations of cosmogenic ¹⁰Be and ²⁶Al in individual clasts from a single stratigraphic horizon can be used to calculate an isochron‐burial age based on an assumed initial ratio and the measured ²⁶Al/¹⁰Be ratio. We suggest that, owing to deep and repeated glacial erosion, the initial isochron ratio of glacial landscapes at the time of burial varies between 6.75 and 8.4. Analysis of 22 clasts of different lithology, shape, and size from one 0.5 m thick gravel bed at Siglistorf (Canton Aargau) indicates low nuclide concentrations: <20 000 ¹⁰Be atoms/g and <150 000 ²⁶Al atoms/g. Using an ²⁶Al/¹⁰Be ratio of 7.6 (arithmetical mean of 6.75 and 8.4), we calculate a mean isochron‐burial age of 1.5 ± 0.2 Ma. This age points to an average bedrock incision rate between 0.13 and 0.17 mm/a. Age data from the Irchel, Stadlerberg, and Siglistorf sites show that the Higher Swiss Deckenschotter was deposited between 2.5 and 1.3 Ma. Our results indicate that isochron‐burial dating can be successfully applied to glaciofluvial sediments despite very low cosmogenic nuclide concentrations. Copyright © 2017 John Wiley & Sons, Ltd.  相似文献   

Chronology of Quaternary terrace deposits at the locality Hohle Gasse (Pratteln,NW Switzerland)     

Anne Claude  Naki Akçar  Susan Ivy-Ochs  Fritz Schlunegger  Philippe Rentzel  Christine Pümpin  Dmitry Tikhomirov  Peter W. Kubik  Christof Vockenhuber  Andreas Dehnert  Meinert Rahn  Christian Schlüchter 《Swiss Journal of Geoscience》2017,110(3):793-809

The Quaternary stratigraphy of the Alpine Foreland consists of distinct terrace levels, which have been assigned to four morphostratigraphic units: Höhere (Higher) Deckenschotter, Tiefere (Lower) Deckenschotter, Hochterrasse (High Terrace) and Niederterrasse (Lower Terrace). Here, we focus on the terrace gravels at Hohle Gasse, SSE of Pratteln near Basel, which are mapped as Tiefere Deckenschotter. Petrographic and morphometric data established from clasts allowed to infer the transport mechanisms and sources of the gravels. Sedimentological analyses indicate that the gravels were transported by a braided river and deposited in a distal glaciofluvial setting. In addition, it can be shown that the majority of the clasts display multiple reworking and only a minority maintained a distinct glaciofluvial shape. Cosmogenic multi-isotope dating using ¹⁰Be and ³⁶Cl allowed direct dating of the sediments at the study site. A depth-profile age of \(2 70_{ - 1 90}^{ + 8 30}\) ka for ¹⁰Be was achieved for the deposits at Hohle Gasse. Unfortunately, no age could be modelled from the ³⁶Cl concentrations as the blank correction was too high. Furthermore, this age proves that the studied terrace level should be assigned to the morphostratigraphic unit Hochterrasse.  相似文献