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91.
Jamie Lee Stevenson Christian Birkel Aaron J. Neill Doerthe Tetzlaff Chris Soulsby 《水文研究》2021,35(6):e14223
Isotopes are increasingly used in rainfall-runoff models to constrain conceptualisations of internal catchment functioning and reduce model uncertainty. However, there is little guidance on how much tracer data is required to adequately do this, and different studies use data from different sampling strategies. Here, we used a 7-year time series of daily stable water isotope samples of precipitation and streamflow to derive a range of typical stream sampling regimes and investigate how this impacts calibration of a semi-distributed tracer-aided model in terms of flow, deuterium and flux age simulations. Over the 7 years weekly sampling facilitated an almost identical model performance as daily, and there were only slight deteriorations in performance for fortnightly sampling. Monthly sampling resulted in poorer deuterium simulations and greater uncertainty in the derived parameter sets ability to accurately represent catchment functioning, evidenced by unrealistic reductions in the volumes of water available for mixing in the saturation area causing simulated water age decreases. Reducing sampling effort and restricting data collection to 3 years caused reductions in the accuracy of deuterium simulation, though the deterioration did not occur if sampling continued for 5 years. Analysis was also undertaken to consider the effects of reduced sampling effort over the driest and wettest hydrological years to evaluate effects of more extreme conditions. This showed that the model was particularly sensitive to changes in sampling during dry conditions, when the catchment hydrological response is most non-linear. Across all dataset durations, sampling in relation to flow conditions, rather than time, revealed that samples collected at flows >Q50 could provide calibration results comparable to daily sampling. Targeting only extreme high flows resulted in poor deuterium and low flow simulations. This study suggests sufficient characterization of catchment functioning can be obtained through reduced sampling effort over longer timescales and the targeting of flows >Q50. 相似文献
92.
Aaron S. Burton Jamie E. Elsila Jason E. Hein Daniel P. Glavin Jason P. Dworkin 《Meteoritics & planetary science》2013,48(3):390-402
Carbonaceous chondrites contain numerous indigenous organic compounds and could have been an important source of prebiotic compounds required for the origin of life on Earth or elsewhere. Extraterrestrial amino acids have been reported in five of the eight groups of carbonaceous chondrites and are most abundant in CI, CM, and CR chondrites but are also present in the more thermally altered CV and CO chondrites. We report the abundance, distribution, and enantiomeric and isotopic compositions of simple primary amino acids in six metal‐rich CH and CB carbonaceous chondrites that have not previously been investigated for amino acids: Allan Hills (ALH) 85085 (CH3), Pecora Escarpment (PCA) 91467 (CH3), Patuxent Range (PAT) 91546 (CH3), MacAlpine Hills (MAC) 02675 (CBb), Miller Range (MIL) 05082 (CB), and Miller Range (MIL) 07411 (CB). Amino acid abundances and carbon isotopic values were obtained by using both liquid chromatography time‐of‐flight mass spectrometry and fluorescence, and gas chromatography isotope ratio mass spectrometry. The δ13C/12C ratios of multiple amino acids fall outside of the terrestrial range and support their extraterrestrial origin. Extracts of CH chondrites were found to be particularly rich in amino acids (13–16 parts per million, ppm) while CB chondrite extracts had much lower abundances (0.2–2 ppm). The amino acid distributions of the CH and CB chondrites were distinct from the distributions observed in type 2 and 3 CM and CR chondrites and contained elevated levels of β‐, γ‐, and δ‐amino acids compared to the corresponding α‐amino acids, providing evidence that multiple amino acid formation mechanisms were important in CH and CB chondrites. 相似文献
93.
Paul H. Whitfield Donald H. Burn Jamie Hannaford Hélène Higgins Glenn A. Hodgkins Terry Marsh 《水文科学杂志》2013,58(8):1562-1579
Abstract Identifying climate-driven trends in river flows on a global basis is hampered by a lack of long, quality time series data for rivers with relatively undisturbed regimes. This is a global problem compounded by the lack of support for essential long-term monitoring. Experience demonstrates that, with clear strategic objectives, and the support of sponsoring organizations, reference hydrologic networks can constitute an exceptionally valuable data source to effectively identify, quantify and interpret hydrological change—the speed and magnitude of which is expected to a be a primary driver of water management and flood alleviation strategies through the future—and for additional applications. Reference hydrologic networks have been developed in many countries in the past few decades. These collections of streamflow gauging stations, that are maintained and operated with the intention of observing how the hydrology of watersheds responds to variations in climate, are described. The status of networks under development is summarized. We suggest a plan of actions to make more effective use of this collection of networks. Editor Z.W. Kundzewicz; Associate editor K. Hamed Citation Whitfield, P.H., et al., 2012. Reference hydrologic networks I. The status and potential future directions of national reference hydrologic networks for detecting trends. Hydrological Sciences Journal, 57 (8), 1562–1579. 相似文献
94.
Natasha M. JOHNSON Jamie E. ELSILA Mickey KOPSTEIN Joseph A. NUTH III 《Meteoritics & planetary science》2012,47(6):1029-1034
Abstract— Fischer‐Tropsch‐type (FTT) reactions have been hypothesized to contribute to the formation of organic compounds in the early solar system, but it has been difficult to identify a signature of such reactions in meteoritic organics. The work reported here examined whether temperature‐dependent carbon isotopic fractionation of FTT reactions might provide such a signature. Analyses of bulk organic deposits resulting from FTT experiments show a slight trend toward lighter carbon isotopic ratios with increasing temperature. It is unlikely, however, that these carbon isotopic signatures could provide definitive provenance for organic compounds in solar system materials produced through FTT reactions, because of the small scale of the observed fractionations and the possibility that signatures from many different temperatures may be present in any specific grain. 相似文献
95.
96.
Jamie E. Elsila Daniel P. Glavin Jason P. Dworkin 《Meteoritics & planetary science》2009,44(9):1323-1330
Abstract— Our previous analysis of cometary samples returned to Earth by NASA's Stardust spacecraft showed several amines and amino acids, but the origin of these compounds could not be firmly established. Here, we present the stable carbon isotopic ratios of glycine and ε‐amino‐n‐caproic acid (EACA), the two most abundant amino acids identified in Stardust‐returned foil samples measured by gas chromatography‐mass spectrometry coupled with isotope ratio mass spectrometry. The δ13C value for glycine of +29 ± 6‰ strongly suggests an extraterrestrial origin for glycine, while the δ13C value for EACA of ?25 ± 2‰ indicates terrestrial contamination by Nylon‐6 during curation. This represents the first detection of a cometary amino acid. 相似文献
97.
Janet Frame is a New Zealand writer who was institutionalized for nearly nine years in mental illness hospitals. Her experiences have been fictionalized in her novel, Faces in the Water, and it is these novelistic representations of the asylum that we explore in this paper. As Frame has suggested in her second volume of autobiography, An Angel at My Table, there is a personal, geographic and linguistic exclusiveness to the asylum in that the patients are stripped of their identity and forced to conform. How these themes are developed in Faces in the Water will be the focus of this paper. 相似文献
98.
Intertidal animals and sediment from Kachemak Bay, Alaska were analysed to determine the concentrations of hydrocarbons. At Coal Point the herbivorous limpet Collisella pelta contained petroleum within its tissues while intertidal algae of the area have previously been shown to accumulate petroleum as a surface coating. At Coal Bay, a locality where both petroleum and coal are present, the filter feeding mussel Mytilus edulis contained petroleum hydrocarbons whereas the deposit feeding clam Macoma balthica contained an array of hydrocarbons suggesting detrital coal as the source. Animals higher in the food web including the gastropod Nucella lima and the urchin Strongylocentrotus droebachiensis showed no evidence of petroleum. All samples contained biogenic hydrocarbons of algal and planktonic origin. 相似文献
99.
100.
This study examines the effect of severe wind events on the mean and variance of housing price indices of six metropolitan
statistical areas (MSA) that are vulnerable to hurricanes and/or tornadoes. The research focuses on three areas that experienced
significant tornado activity (Fort Worth-Arlington, Nashville, and Oklahoma City) and three hurricane-prone areas (Corpus
Christi, Miami, and Wilmington, NC). An econometric time series model that captures the housing market responses to severe
windstorms is utilized. The model estimates changes in the local housing price index (HPI) as a function of several control
variables as well as dichotomous variables that correspond to the tornadoes and hurricanes. As expected, the statistical findings
indicate an immediate but short-lived decline in housing prices following a tornado or hurricane. Somewhat surprising is the
result that the impact on the housing market is remarkably consistent whether the wind event was a hurricane or a tornado.
Hurricanes and tornadoes are vastly different in terms of the point probabilities of a hit, the scope of the affected area
and the lead time that supports last minute preparation to mitigate damage. It appears that the market response to destruction
of real property does not distinguish between the types of wind event that produced the damage to the region. Results suggest
that windstorms result in an immediate one-half to two percent reduction in total MSA housing value. This corresponds to a
range of $34 million to $580 million in lost housing value. Estimates indicate some differences in how long market values
continue to decline in the periods following the wind event; however, most of the decline occurs within four quarters after
the windstorm. These differences can be attributed to the particular time series characteristics of the specific housing markets
and their respective housing price indices. The market serves the purpose of integrating and normalizing the losses. In so
doing the market provides a metric— a method for calibrating and comparing structural damage caused by different phenomenon.
相似文献
Yongsheng WangEmail: |