Intervening O vi Quasar Absorption Systems at Low Redshift: A Significant Baryon Reservoir     

Tripp TM  Savage BD  Jenkins EB 《The Astrophysical journal》2000,534(1):L1-L5

Far-UV echelle spectroscopy of the radio-quiet QSO H1821+643 (zem=0.297), obtained with the Space Telescope Imaging Spectrograph (STIS) at approximately 7 km s-1 resolution, reveals four definite O vi absorption-line systems and one probable O vi absorber at 0.15相似文献   

Hornblende geothermometry of amphibolite layers of the Popple Hill gneiss, north-west Adirondack Lowlands, New York, USA   总被引：1，自引：0，他引：1  

Liogys  & Jenkins 《Journal of Metamorphic Geology》2000,18(5):513-530

The exchange reaction tschermakite+2 diopside+2 quartz=tremolite+2 anorthite (HPCQ), in combination with the thermodynamic database TWQ (version 1.02, Berman, 1991), has been evaluated for its usefulness as a geothermometer. This reaction, which is both water conserving (independent of water fugacity) and which does not require the presence of garnet, is well suited for studying pyroxene‐bearing amphibolites. As an application of this geothermometer, we have re‐examined the amphibolites occurring in the Popple Hill gneiss of the Adirondack Lowlands of New York, USA, to better understand the magnitude of temperature variation preserved in the amphibolites themselves in this classic locality. At an assumed constant pressure of 7 kbar, the temperatures range from 619 to 682 °C from Edwards to Pierrepont and are uncorrelated with either distance along the strike of the region or with modal mineralogical variations. Hornblende exhibits a narrow compositional range suggesting that there has been little or no thermal gradient along the strike of the Lowlands. Temperatures recorded just north of Colton are, however, distinctly higher (694–758 °C). Although it is likely that the Popple Hill gneiss amphibolites experienced some effects of progressive metamorphism, particularly in the vicinity of Colton, the variations in modal mineralogy are most likely the result of such factors as local variations in the bulk chemistry of the protolith and in the fugacity of H₂O due to infiltration of diluting species (e.g. CO₂, CH₄), rather than a regional temperature variation. Temperatures recorded by the HPCQ geothermometer reported here are similar in magnitude and geographic trend to those reported for graphite–calcite carbon‐isotope thermometry by Kitchen & Valley (1995), suggesting that peak metamorphism in the Adirondack Lowlands involved laterally extensive and fairly uniform isotherms.  相似文献   

Lunar surface exposure models for meteorites Elephant Moraine 96008 and Dar al Gani 262 from the Moon     

Otto EUGSTER  Ernst POLNAU  Emma SALERNO  Dario TERRIBILINI 《Meteoritics & planetary science》2000,35(6):1177-1181

Abstract— We derived the cosmic‐ray and solar particle exposure history for the two lunar meteorites Elephant Moraine (EET) 96008 and Dar al Gani (DaG) 262 on the basis of the noble gas isotopic abundances including the radionuclide ⁸¹Kr. For EET 96008, we propose a model for the exposure to cosmic rays and solar particles in three stages on the Moon: an early stage ～500 Ma ago, lasting less than 9 Ma at a shallow shielding depth of 20 g/cm², followed by a stage when the material was buried, without exposure, until it was exposed in a recent stage. This recent stage, at a shielding depth in a range of 200–600 g/cm², lasted for ～26 Ma until ejection. This model is essentially the same as that previously found for lunar meteorite EET 87521; thus, pairing of the two Elephant Moraine lunar meteorites that were recovered on the same icefield in Antarctica is confirmed by our data. The cosmic‐ray‐produced isotopes, the trapped solar and lunar atmospheric noble gases, as well as the radionuclide ⁸¹Kr observed for the DaG 262 lunar meteorite are consistent with a one‐stage lunar exposure history. The average burial depth of the Dar al Gani material before ejection was within a range of 50–80 g/cm². The exposure to cosmic rays at this depth lasted 500–1000 Ma. This long residence time for Dar al Gani at relatively shallow depth explains the high concentrations of implanted solar noble gases.  相似文献   

Stable isotope evidence of late MIS 3 to middle Holocene palaeoenvironments from Sehonghong Rockshelter,eastern Lesotho          下载免费PDF全文

Emma Loftus  Brian A. Stewart  Genevieve Dewar  Julia Lee‐Thorp 《第四纪科学杂志》2015,30(8):805-816

  相似文献   

Fire,climate and the origins of agriculture: micro‐charcoal records of biomass burning during the last glacial–interglacial transition in Southwest Asia     

Rebecca Turner  Neil Roberts  Warren J. Eastwood  Emma Jenkins  Arlene Rosen 《第四纪科学杂志》2010,25(3):371-386

  相似文献   

High-frequency multi-solute calibration using an in situ UV–visible sensor     

Juan Pesántez  Christian Birkel  Giovanny M. Mosquera  Pablo Peña  Viviana Arízaga-Idrovo  Emma Mora  William H. McDowell  Patricio Crespo 《水文研究》2021,35(9):e14357

Monitoring the temporal variation of solute concentrations in streams at high temporal frequency can play an important role in understanding the hydrological and biogeochemical behaviour of catchments. UV–visible spectrometry is a relatively inexpensive and easily used tool to infer those concentrations in streams at high temporal resolution. However, it is not yet clear which solutes can be modelled with such an in-situ sensor. Here, we installed a UV–visible spectrometer probe (200–750 nm) in a high-altitude tropical Páramo stream to record the wavelength absorbance at a 5-min temporal resolution. For calibration, we simultaneously sampled stream water at a 4-h frequency from February 2018 to March 2019 for subsequent laboratory analysis. Absorbance spectra and laboratory-determined solute concentrations were used to identify the best calibration method and to determine which solute concentrations can be effectively inferred using in situ spectrometry through the evaluation of six calibration methods of different mathematical complexity. Based on the Nash – Sutcliffe efficiency (NSE) and Akaike information criterion metrics, our results suggest that multivariate methods always outperformed simpler strategies to infer solute concentrations. Eleven out of 21 studied solutes (Al, DOC, Ca, Cu, K, Mg, N, Na, Rb, Si and Sr) were successfully calibrated (NSE >0.50) and could be inferred using UV–visible spectrometry even with a reduced daily sampling frequency. It is worth noting that most calibrated solutes were correlated with wavelengths (WLs) in the low range of the spectra (i.e., UV range) and showed relatively good correlation with DOC. The latter suggests that estimation of metal concentrations could be possible in other streams with a high organic load (e.g., peat dominated catchments). In situ operation of spectrometers to monitor water quality parameters at high temporal frequency (sub-hourly) can enhance the protection of human water supplies and aquatic ecosystems as well as providing information for assessing catchment hydrological functioning.  相似文献   

The Multiscale TROPIcal CatchmentS critical zone observatory M-TROPICS dataset III: Hydro-geochemical monitoring of the Mule Hole catchment,south India     

Jean Riotte  Laurent Ruiz  Stéphane Audry  Benjamin Baud  Jean-Pierre Bedimo Bedimo  Laurie Boithias  Jean-Jacques Braun  Bernard Dupré  Jean-Louis Duprey  Mikael Faucheux  Christelle Lagane  Jean-Christophe Marechal  Hemanth Moger  Mandalagiri Subbarayappa Mohan Kumar  Harshad Parate  Olivier Ribolzi  Emma Rochelle-Newall  Buvaneshwari Sriramulu  Murari Varma  Muddu Sekhar 《水文研究》2021,35(5):e14196

Despite the importance of tropical ecosystems for climate regulation, biodiversity, water and nutrient cycles, only a few Critical Zone Observatories (CZOs) are located in the tropics. Among these, most are in humid climates, while very few data exist for semi-arid and sub-humid climates, due to the difficulty of estimating hydro-geochemical balances in catchments with ephemeral streams. We contribute to fill this gap by presenting a meteorological and hydro-geochemical dataset acquired at the Mule Hole catchment (4.1 km²), a pristine dry deciduous forest located in a biosphere reserve in south India. The dataset consists of time series of variables related to (i) meteorology, including rainfall, air temperature, relative humidity, wind speed and direction, and global radiation, (ii) hydrology, including water level and discharge at the catchment outlet, (iii) hydrogeology, including manual (monthly) and/or automated (from 15 min to hourly) groundwater levels in nine piezometers and (iv) geochemistry, including suspended sediment content in the stream and chemical composition of rainfall (event based), groundwater (monthly sampling) and stream water (storm events, 15 min to hourly frequency with an automatic sampler). The time series extend from 2003 to 2019. Measurement errors are minimized by frequent calibration of sensors and quality checks, both in the field and in the laboratory. Despite these precautions, several data gaps exist, due to occasional access restriction to the site and instrument destruction by wildlife. Results show that large seasonal and interannual variations of climatic conditions were reflected in the large variations of stream flow and groundwater recharge, as well as in water chemical composition. Notably, they reveal a long-term evolution of groundwater storage, suggesting hydrogeological cycles on a decadal scale. This dataset, alone or in combination with other data, has already allowed to better understand water and element cycling in tropical dry forests, and the role of forest diversity on biogeochemical cycles. As tropical ecosystems are underrepresented by Critical Zone Observatories, we expect this data note to be valuable for the global scientific community.  相似文献   

The effect of low‐permeability fault zones on groundwater flow in a compartmentalized system. Experimental evidence from a carbonate aquifer (Southern Italy)          下载免费PDF全文

Emma Petrella  Durante Aquino  Francesco Fiorillo  Fulvio Celico 《水文研究》2015,29(6):1577-1587

The hydrogeological behaviour of fault zones in carbonate aquifers is often neglected in conceptual and numerical models. Furthermore, no information is available regarding the relationships between piezometric levels when significant compartmentalization occurs due to the occurrence of low‐flow fault zones. The aim of this study was to refine the conceptualization of subsurface flow in faulted carbonate aquifers and to analyse relationships between sub‐basins within a compartmentalized aquifer system in Southern Italy. The interactions between compartments that straddle low‐flow faults were investigated over four hydrologic years using a statistical approach to compare (i) the hydraulic heads within two wells located up‐ and down‐gradient of tectonic discontinuities as well as (ii) the rainfall and piezometric levels. The results of this study suggest that a set of barriers exists between the wells, and, therefore, the total head loss observed between the wells (approximately 80 m) should be distributed across several aquitards, with one aquitard exhibiting a relatively high permeability or low degree of integrity. Due to slight differences in permeability, transient conditions in aquitards can occur over relatively short periods, which is in agreement with the results of the statistical data analysis. Consequently, rather than being caused by pure aquitards, aquifer system compartmentalization likely results from slight differences in the permeability between lower‐permeability fault zones and adjacent higher‐permeability protoliths. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   

On judging the credibility of climate predictions     

Friederike E. L. Otto  Christopher A. T. Ferro  Thomas E. Fricker  Emma B. Suckling 《Climatic change》2015,132(1):47-60

  相似文献   

Quantifying the impact of climate change on drought regimes using the Standardised Precipitation Index     

Katie Jenkins  Rachel Warren 《Theoretical and Applied Climatology》2015,120(1-2):41-54

  相似文献