Seasonal connections between meteoric water and streamflow generation along a mountain headwater stream     

Sam J. Leuthold  Stephanie A. Ewing  Robert A. Payn  Florence R. Miller  Stephan G. Custer 《水文研究》2021,35(2):e14029

In snowmelt-driven mountain watersheds, the hydrologic connectivity between meteoric waters and stream flow generation varies strongly with the season, reflecting variable connection to soil and groundwater storage within the watershed. This variable connectivity regulates how streamflow generation mechanisms transform the seasonal and elevational variation in oxygen and hydrogen isotopic composition (δ¹⁸O and δD) of meteoric precipitation. Thus, water isotopes in stream flow can signal immediate connectivity or more prolonged mixing, especially in high-relief mountainous catchments. We characterized δ¹⁸O and δD values in stream water along an elevational gradient in a mountain headwater catchment in southwestern Montana. Stream water isotopic compositions related most strongly to elevation between February and March, exhibiting higher δ¹⁸O and δD values with decreasing elevation. These elevational isotopic lapse rates likely reflect increased connection between stream flow and proximal snow-derived water sources heavily subject to elevational isotopic effects. These patterns disappeared during summer sampling, when consistently lower δ¹⁸O and δD values of stream water reflected contributions from snowmelt or colder rainfall, despite much higher δ¹⁸O and δD values expected in warmer seasonal rainfall. The consistently low isotopic values and absence of a trend with elevation during summer suggest lower connectivity between summer precipitation and stream flow generation as a consequence of drier soils and greater transpiration. As further evidence of intermittent seasonal connectivity between the stream and adjacent groundwaters, we observed a late-winter flush of nitrate into the stream at higher elevations, consistent with increased connection to accumulating mineralized nitrogen in riparian wetlands. This pattern was distinct from mid-summer patterns of nitrate loading at lower elevations that suggested heightened human recreational activity along the stream corridor. These observations provide insights linking stream flow generation and seasonal water storage in high elevation mountainous watersheds. Greater understanding of the connections between surface water, soil water and groundwater in these environments will help predict how the quality and quantity of mountain runoff will respond to changing climate and allow better informed water management decisions.  相似文献   

Testing accretion mechanisms of the H chondrite parent body utilizing nucleosynthetic anomalies     

Sren Grube Pedersen  Martin Schiller  James N. Connelly  Martin Bizzarro 《Meteoritics & planetary science》2019,54(6):1215-1227

Planetary bodies a few hundred kilometers in radii are the precursors to larger planets but it is unclear whether these bodies themselves formed very rapidly or accreted slowly over several millions of years. Ordinary H chondrite meteorites provide an opportunity to investigate the accretion time scale of a small planetary body given that variable degrees of thermal metamorphism present in H chondrites provide a proxy for their stratigraphic depth and, therefore, relative accretion times. We exploit this feature to search for nucleosynthetic isotope variability of ⁵⁴Cr, which is a sensitive tracer of spatial and temporal variations in the protoplanetary disk's solids, between 17 H chondrites covering all petrologic types to obtain clues about the parent body accretionary rate. We find no systematic variability in the mass‐biased corrected abundances of ⁵³Cr or ⁵⁴Cr outside of the analytical uncertainties, suggesting very rapid accretion of the H chondrite parent body consistent with turbulent accretion. By utilizing the μ⁵⁴Cr–planetary mass relationship observed between inner solar system planetary bodies, we calculate that the H chondrite accretion occurred at 1.1 ± 0.4 or 1.8 ± 0.2 Myr after the formation of calcium‐aluminum‐rich inclusions (CAIs), assuming either the initial ²⁶Al/²⁷Al abundance of inner solar system solids determined from angrite meteorites or CAIs from CV chondrites, respectively. Notably, these ages are in agreement with age estimates based on the parent bodies’ thermal evolution when correcting these calculations to the same initial ²⁶Al/²⁷Al abundance, reinforcing the idea of a secular evolution in the isotopic composition of inner disk solids.  相似文献   

Mineralogy and temperature of crater Haulani on Ceres          下载免费PDF全文

F. Tosi  F. G. Carrozzo  A. Raponi  M. C. De Sanctis  G. Thangjam  F. Zambon  M. Ciarniello  A. Nathues  M. T. Capria  E. Rognini  E. Ammannito  M. Hoffmann  K. Krohn  A. Longobardo  E. Palomba  C. M. Pieters  K. Stephan  C. A. Raymond  C. T. Russell 《Meteoritics & planetary science》2018,53(9):1902-1924

We investigate the region of crater Haulani on Ceres with an emphasis on mineralogy as inferred from data obtained by Dawn's Visible InfraRed mapping spectrometer (VIR), combined with multispectral image products from the Dawn Framing Camera (FC) so as to enable a clear correlation with specific geologic features. Haulani, which is one of the youngest craters on Ceres, exhibits a peculiar “blue” visible to near‐infrared spectral slope, and has distinct color properties as seen in multispectral composite images. In this paper, we investigate a number of spectral indices: reflectance; spectral slopes; abundance of Mg‐bearing and NH₄‐bearing phyllosilicates; nature and abundance of carbonates, which are diagnostic of the overall crater mineralogy; plus a temperature map that highlights the major thermal anomaly found on Ceres. In addition, for the first time we quantify the abundances of several spectral endmembers by using VIR data obtained at the highest pixel resolution (~0.1 km). The overall picture we get from all these evidences, in particular the abundance of Na‐ and hydrous Na‐carbonates at specific locations, confirms the young age of Haulani from a mineralogical viewpoint, and suggests that the dehydration of Na‐carbonates in the anhydrous form Na₂CO₃ may be still ongoing.  相似文献   

An algorithm to resolve γ-rays from charged cosmic rays with DAMPE     

Zun-Lei Xu  Kai-Kai Duan  Zhao-Qiang Shen  Shi-Jun Lei  Tie-Kuang Dong  Fabio Gargano  Simone Garrappa  Dong-Ya Guo  Wei Jiang  Xiang Li  Yun-Feng Liang  Mario Nicola Mazziotta  Maria Fernanda Munoz Salinas  Meng Su  Valerio Vagelli  Qiang Yuan  Chuan Yue  Jing-Jing Zang  Ya-Peng Zhang  Yun-Long Zhang  Stephan Zimmer 《天文和天体物理学研究(英文版)》2018,(3)

The DArk Matter Particle Explorer(DAMPE),also known as Wukong in China,which was launched on 2015 December 17,is a new high energy cosmic ray and γ-ray satellite-borne observatory.One of the main scientific goals of DAMPE is to observe Ge V-Te V high energy γ-rays with accurate energy,angular and time resolution,to indirectly search for dark matter particles and for the study of high energy astrophysics. Due to the comparatively higher fluxes of charged cosmic rays with respect to γ-rays,it is challenging to identify γ-rays with sufficiently high efficiency,minimizing the amount of charged cosmic ray contamination. In this work we present a method to identify γ-rays in DAMPE data based on Monte Carlo simulations,using the powerful electromagnetic/hadronic shower discrimination provided by the calorimeter and the veto detection of charged particles provided by the plastic scintillation detector. Monte Carlo simulations show that after this selection the number of electrons and protons that contaminate the selected γ-ray events at～10 Ge V amounts to less than 1% of the selected sample.Finally,we use flight data to verify the effectiveness of the method by highlighting known γ-ray sources in the sky and by reconstructing preliminary light curves of the Geminga pulsar.  相似文献   

Numerical Analysis of Groundwater Ridging Processes Considering Water‐Air Flow in a Hillslope          下载免费PDF全文

Yong Ge Zang  Dong Mei Sun  Ping Feng  Stephan Semprich 《Ground water》2018,56(4):594-609

In this study, a water‐air two‐phase flow model was employed to investigate the formation, extension, and dissipation of groundwater ridging induced by recharge events in a hypothetical hillslope‐riparian zone, considering interactions between the liquid and gas phases in soil voids. The simulation results show that, after a rain begins, the groundwater table near the stream is elevated instantaneously and significantly, thereby generating a pressure gradient driving water toward both the stream (the discharge of groundwater to the stream) and upslope (the extension of groundwater ridging into upslope). Meanwhile, the airflow upslope triggered by the advancing wetting front moves downward gradually. Therefore, the extension of groundwater ridging into upslope and the downward airflow interact within a certain region. After the rain stops, groundwater ridging near the stream declines quickly while the airflow in the lower part of upslope is still moving into the hillslope. Thus, the airflow upslope mitigates the dissipation of groundwater ridging. Additionally, the development of groundwater ridging under different conditions, including rain intensity, intrinsic permeability, capillary fringe height, and initial groundwater table, was analyzed. Changes in intrinsic permeability affect the magnitude of groundwater ridging near the stream, as well as the downward speed of airflow, thereby generating highly complex responses. The capillary fringe is not a controlling factor but an influence factor on the formation of groundwater ridging, which is mainly related to the antecedent moisture. It was demonstrated that groundwater ridging also occurs where an unsaturated zone occurs above the capillary fringe with a subsurface lateral flow.  相似文献   

Mechanisms linking active rock glaciers and impounded surface water formation in high‐mountain areas          下载免费PDF全文

Nicola Colombo  Luigi Sambuelli  Cesare Comina  Chiara Colombero  Marco Giardino  Stephan Gruber  Gaetano Viviano  Livia Vittori Antisari  Franco Salerno 《地球表面变化过程与地形》2018,43(2):417-431

Rock glaciers are slowly flowing mixtures of debris and ice occurring in mountains. They can represent a reservoir of water, and melting ice inside them can affect surface water hydrochemistry. Investigating the interactions between rock glaciers and water bodies is therefore necessary to better understand these mechanisms. With this goal, we elucidate the hydrology and structural setting of a rock glacier–marginal pond system, providing new insights into the mechanisms linking active rock glaciers and impounded surface waters. This was achieved through the integration of waterborne geophysical techniques (ground penetrating radar, electrical resistivity tomography and self‐potentials) and heat tracing. Results of these surveys showed that rock glacier advance has progressively filled the valley depression where the pond is located, creating a dam that could have modified the level of impounded water. A sub‐surface hydrological window connecting the rock glacier to the pond was also detected, where an inflow of cold and mineralised underground waters from the rock glacier was observed. Here, greater water contribution from the rock glacier occurred following intense precipitation events during the ice‐free season, with concomitant increasing electrical conductivity values. The outflowing dynamic of the pond is dominated by a sub‐surface seepage where a minor fault zone in bedrock was found, characterised by altered and highly‐fractured rocks. The applied approach is evaluated here as a suitable technique for investigating logistically‐complex hydrological settings which could be possibly transferred to wider scales of investigation. Copyright © 2017 John Wiley & Sons, Ltd.  相似文献   

The brecciated texture of polymict eucrites: Petrographic investigations of unequilibrated meteorites from the Antarctic Yamato collection     

Christian Vollmer  Stella Rombeck  Julia Roszjar  Adam R. Sarafian  Stephan Klemme 《Meteoritics & planetary science》2020,55(3):558-574

We report on the petrography and mineralogy of five Yamato polymict eucrites to better constrain the formation and alteration of crustal material on differentiated asteroids. Each sample consists of different lithic clasts that altogether form four dominant textures and therefore appear to originate from closely related petrological areas within Vesta′s crust. The textures range from subophitic to brecciated, porphyritic, and quench‐textured, that differ from section to section. Comparison with literature data for these samples is therefore difficult, which stresses that polymict eucrites are extremely complex in their petrography and investigation of only one thick section may not be representative for the host rock. We also show that sample Y‐793548 consists of more than one lithic unit and must therefore be classified as polymict instead of monomict. The variety and nature of lithic textures in the investigated Yamato meteorites indicate shock events, intense post‐magmatic thermal annealing, and secondary alteration. These postmagmatic features occur in different intensities, varying from clast to clast or among coexisting mineral fragments on a small, local scale. Several clasts within the eucrites studied have been modified by late‐stage alteration processes that caused deposition of Fe‐rich olivine and Fe enrichment along cracks crosscutting pyroxene crystals. However, formation of these secondary phases seems to be independent of the degree of thermal metamorphism observed within every type of clast, which would support a late‐stage metasomatism model for their formation.  相似文献   

Technologies for adaptation to climate change. Examples from the agricultural and water sectors in Lebanon     

Sara Trærup  Jean Stephan 《Climatic change》2015,131(3):435-449

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Identification of the uranium speciation in an underground acid mine drainage environment     

Thuro Arnold  Nils Baumann  Sina Brockmann  Udo Zimmermann  Stephan Weiß 《Geochimica et cosmochimica acta》2011,75(8):2200-3065

The subsurface acid mine drainage (AMD) environment of an abandoned underground uranium mine in Königstein/Saxony/Germany, currently in the process of remediation, is characterized by low pH, high sulfate concentrations and elevated concentrations of heavy metals, in particular uranium. Acid streamers thrive in the mine drainage channels and are heavily coated with iron precipitates. These precipitates are biologically mediated iron precipitates and related to the presence of Fe-oxidizing microorganisms forming copious biofilms in and on the Fe-precipitates. Similar biomineralisations were also observed in stalactite-like dripstones, called snottites, growing on the gallery ceilings.The uranium speciation in these solutions of underground AMD waters flowing in mine galleries as well as dripping from the ceiling and forming stalactite-like dripstones were studied by time resolved laser-induced fluorescence spectroscopy (TRLFS). The fluorescence lifetime of uranium species in both AMD water environments were best described with a mono-exponential decay, indicating the presence of one major species. The detected positions of the emission bands and by comparing it in a fingerprinting procedure with spectra obtained for acid sulfate reference solutions, in particular Fe(III) - SO₄²⁻ - UO₂²⁺ reference solutions, indicated that the uranium speciation in the AMD environment of Königstein is dominated in the pH range of 2.5-3.0 by the highly mobile aquatic uranium sulfate species UO₂SO_4(aq) and formation of uranium precipitates is rather unlikely as is retardation by sorption processes. The presence of iron in the AMD reduces the fluorescence lifetime of the UO₂SO_4(aq) species from 4.3 μs, found in iron-free uranium sulfate reference solutions, to 0.7 μs observed in both AMD waters of Königstein and also in the iron containing uranium sulfate reference solutions.Colloids were not observed in both drainage water and dripping snottite water as photon correlation spectroscopy analyses and centrifugation experiments at different centrifugal accelerations between 500g and 46000g revealed. Thus transport and uranium speciation at the investigated AMD sites is neither influenced by U(IV) or U(VI) eigencolloids nor by uranium adsorbed on colloidal particles.This study shows that TRLFS is a suitable spectroscopic technique to identify the uranium speciation in bulk solutions of AMD environments.  相似文献   

Measuring long-run economic effects of natural hazard     

Robert McComb  Young-Kyu Moh  Anita R. Schiller 《Natural Hazards》2011,58(1):559-566

This paper studies the long-run economic effects of severe weather on regional economies. A catastrophic event, such as a hurricane, will have an effect on both the directly impacted region and adjacent regions. With dramatically increasing damage from catastrophic weather events over the past few decades, comprehensive assessment of the long-run economic impact of natural disasters across the broader region becomes more important than ever for planning for post-disaster recovery. We estimate the long-run effect of Hurricane Katrina on the unemployment rate of Houston, TX by employing time-series and fixed-effect models. Using Dallas as a control, we find that Katrina is associated with a higher long-run unemployment rate in Houston than would otherwise have been expected. This implies that the hurricane-generated adverse relative effects on Houston. Our findings suggest that areas that are geographically proximate to the directly impacted region can sustain lasting negative economic consequences.  相似文献