A tale of two isotopes: differences in hydrograph separation for a runoff event when using δD versus δ18O     

Steve W. Lyon  Sharon L. E. Desilets  Peter A. Troch 《水文研究》2009,23(14):2095-2101

It is often assumed that stable water isotopes (δD and δ¹⁸O) provide redundant information for a given sample of water. In this note we illustrate that the choice of isotope used may influence the resultant hydrograph separation. This is especially true in light of the spatial and temporal variability in the isotopic composition of rainfall water at the catchment scale. We present several possible hydrograph separations based on both δD and δ¹⁸O observed in rainfall for a single runoff event occurring in the southwest USA. This study demonstrates the potential of using both stable water isotopes by showing that δD and δ¹⁸O may provide unique information for catchment hydrologists. We also report on the utility of new technology capable of simultaneous measurements of both δD and δ¹⁸O using off‐axis integrated cavity output spectroscopy (OA‐ICOS) methods. This may be of interest to catchment hydrologists seeking to incorporate this type of equipment into their laboratory. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   

Impact of a non-Gaussian density field on Sunyaev–Zeldovich observables     

Sharon Sadeh  Yoel Rephaeli  Joseph Silk 《Monthly notices of the Royal Astronomical Society》2006,368(4):1583-1598

The main statistical properties of the Sunyaev–Zeldovich (S–Z) effect – the power spectrum, cluster number counts and angular correlation function – are calculated and compared within the framework of two density fields which differ in their predictions of the cluster mass function at high redshifts. We do so for the usual Press & Schechter mass function, which is derived on the basis of a Gaussian density fluctuation field, and for a mass function based on a  χ²  distributed density field. These three S–Z observables are found to be very significantly dependent on the choice of the mass function. The different predictions of the Gaussian and non-Gaussian density fields are probed in detail by investigating the behaviour of the three S–Z observables in terms of cluster mass and redshift. The formation time distribution of clusters is also demonstrated to be sensitive to the underlying mass function. A semiquantitative assessment is given of its impact on the concentration parameter and the temperature of intracluster gas.  相似文献   

美国Paradox盆地盐构造新生代的拉伸活化     

戈红星  MOSHER Sharon 《高校地质学报》2008,14(1):49-63

美国科罗拉多高原Paradox盆地中的裂口盐墙和盐背斜,主要是在古生界和中生界沉积物的差异负载作用下发育起来的。盐构造顶部的平缓褶皱,通常被认为是晚白垩纪至古新世拉腊米挤压运动的产物,而其脊顶地堑与山谷,则被认为是挤压后的松弛拉伸及盐溶作用所造成的。基于野外调查、物理模拟以及现代盐构造学理论,研究认为这些平缓褶皱和脊顶地堑,主要是新生代始新世至渐新世北北东向区域拉伸作用的产物。因为岩盐较其围岩软弱,拉伸形变主要集中在早先形成的盐墙、盐背斜及其较薄的顶板中,使盐构造发生活化并形成新的拉伸构造。顶板中的拉伸构造主要包括正断层、地堑、断层滑移(断滑)褶皱以及滚动褶皱。由于区域拉伸方向斜交盐构造走向,断层分布多呈羽列状。在母盐层较厚地区,拉伸使盐刺穿在正断层之下次动上升;而在母盐层较薄地区,拉伸使盐刺穿下降。在初始盐刺穿较高地区,盐构造的侧翼下降;而在初始盐刺穿较低地区,盐构造整体下降。拉伸使盐刺穿变宽,脊顶地堑下沉,形成拉伸型下降盐刺穿特征性的尖角盐体构造。局部地区,盐体从破碎的顶板间溢出,覆盖了下沉的脊顶地堑。  相似文献   

Nucleation,growth and transformation of amorphous and crystalline solids condensing from the gas phase     

E. Krikorian  R. J. Sneed 《Astrophysics and Space Science》1979,65(1):129-154

The condensation of solids was investigated from the initial nucleation stage through continuous film growth, using evaporation and high-energy ion-beam sputtering. At all stages the kinetics of the nucleation process and the structural characteristics of the condensed phase (glassy, polycrystalline and monocrystalline) were defined. Although many condensates were explored, the specific system discussed is germanium condensing on a variety of amorphous and crystalline substrates.The kinetic behavior observed in crystalline deposits was found consistent with the accepted atomistic model for nucleation. This allowed determination of such nucleation parameters as: the activation energies of surface diffusion,Q _d and adsorption,Q _ad ,the critical nucleus size,n ^*, and others. Values of such parameters were found to be systematic functions of the kinetic energy and flux of incident particles and of the type and temperature of the substrate.Two flux and temperature dependent structural order transitions were observed in the very initial nucleation stages and found to coincide with corresponding transitions inn ^*. Correlation was also established between these transitions and two structural transitions occurring during continuous film growth. This was aided by the occurrence of all four transitions in intermediate condensation stages, i.e. prior to coalescence of nucleation clusters into continuous film.All results were very distinctly affected by the vapor state of the adsorbates, implying considerable correlation between condensation on solid surfaces and in a vapor.Invited contribution to the Proceedings of a Workshop onThermodynamics and Kinetics of Dust Formation in the Space Medium, held at the Lunar and Planetary Institute, Houston, 6–8 September, 1978.  相似文献   

SOME NOTES ON THE STATUS AND NATURE OF FIELD METHOD COURSES AT COLLEGES AND UNIVERSITIES IN THE UNITED STATES AND CANADA*     

Sharon M. Thomas 《The Professional geographer》1978,30(4):407-412

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Antioxidant responses to polycyclic aromatic hydrocarbons and organochlorine pesticides in green-lipped mussels (Perna viridis): do mussels "integrate" biomarker responses?   总被引：1，自引：0，他引：1  

Richardson BJ  Mak E  De Luca-Abbott SB  Martin M  McClellan K  Lam PK 《Marine pollution bulletin》2008,57(6-12):503-514

Polycyclic aromatic hydrocarbons (PAHs) and organochlorine pesticides (OCs) are generally present in the marine environment in complex mixtures. The ecotoxicological nature of contaminant interactions, however, is poorly understood, with most scientific observations derived from single contaminant exposure experiments. The objective of this experiment was to examine dose-response relationships between antioxidant parameters and body contaminant levels in mussels exposed to different exposure regimes under laboratory conditions. Accordingly, the green-lipped mussel, Perna viridis, was challenged with a mixture of PAHs (anthracene, fluoranthene, pyrene, benzo[a]pyrene) and OC pesticides (alpha-HCH, aldrin, dieldrin, p,p'-DDT) over a 4 week period. Contaminants were delivered under four different dosing regimes, with all treatments receiving the same total contaminant load by the end of the exposure period. Antioxidant biomarkers were measured after 1, 2, 3 and 4 weeks, including glutathione (GSH), gluathione-S-transferase (GST), superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), glutathione reductase (GR) and lipid peroxidase (LPO). GST and CAT were induced in hepatic tissues in most of the exposure regimes, with the majority of significant induction occurring in a constant exposure regime and a two-step alternate exposure regime. Significant differences among exposure regimes were detected in the body burden of contaminants after 28 days. Hepatic CAT and GSH are proposed as potentially useful biomarkers as they showed good correlation with target contaminants and were not readily affected by different dosing patterns.  相似文献   

A mid-winter, tropical extreme flood-producing storm in southern Israel: Synoptic scale analysis     

B. Ziv  U. Dayan  D. Sharon 《Meteorology and Atmospheric Physics》2005,88(1-2):53-63

Summary An exceptional rainstorm affected the Negev Desert, the southern part of Israel, during 20–23 December 1993 as a result of an active Red Sea trough (ARST). The latter refers to a low pressure trough that extends from eastern Africa northward, along the Red Sea, accompanied by an upper-level cyclonic system. Rainfall totals in certain parts exceeded December averages by a factor of 5. Major precipitating systems had a typical Meso-scale Convective System structure accompanied by showers, with peak intensities of 60–80mmh^–1, and by hail and flash floods, resulting in loss of life and heavy damage.The origin of rainfall systems and of the moisture at lower latitudes, as well as the type of precipitation involved, indicate its tropical nature. The timing of the storm around the winter solstice is unusual, since these tropical-like storms are most frequent in the region in October–November.Unusual synoptic circumstances explain the development and intensity of this storm and this exceptional timing. In contrast to the normal situation in December the mid-level subtropical high over the Sahara was replaced by a cyclone, while the persistent high over the Arabian Peninsula intensified. As a result, a southerly flow persisted over the Red Sea several days prior to the storm initiation and transported tropical moisture and heat northward. The ascending air motion observed along the Red Sea enhanced convection there, which transported lower-level moisture from the water surface and transported it to the surrounding regions. Finally, a moving upper-trough that approached the region from the west transported the tropical moisture further to the Negev and supplied the lifting that transformed this moisture and instability into heavy showers.  相似文献   

Uptake and depuration of PAHs and chlorinated pesticides by semi-permeable membrane devices (SPMDs) and green-lipped mussels (Perna viridis)     

Richardson BJ  Tse ES  De Luca-Abbott SB  Martin M  Lam PK 《Marine pollution bulletin》2005,51(8-12):975-993

Semi-batch seawater experiments were conducted to follow the uptake and release of selected PAHs (anthracene, fluorathene, pyrene and B[a]P) and organochlorine pesticides (-HCH, aldrin, dieldrin, p,p′-DDT) in semi-permeable membrane devices (SPMDs) and green-lipped mussels (Perna viridis). Mathematical models were applied to describe the uptake and elimination curves of the contaminants for SPMDs, and kinetic parameters, such as uptake rate constants, and equilibrium triolein/water partitioning coefficients were calculated. SPMD data showed a good fit to estimate rate constant and partition coefficient equations, but only those contaminants which partitioned mainly in the dissolved phase (-HCH and dieldrin) were well explained for mussels. Poor conformity of the other contaminants indicated mussels uptake by routes other than diffusion, such as ingestion of algae. An apparent equilibrium state was only noted for -HCH in mussels. Aldrin was not detected in mussels in the first few days of exposure, indicating potential metabolism of this compound. B[a]P was not detected in the triolein of SPMDs, which suggests that the membrane may act as a reservoir. Loss of spiked B[a]P from the triolein was evident in a depuration experiment, which may indicate transfer to the membrane. Rate constants for mussels were higher than those for SPMDs, but the reverse was true for partition coefficients. Overall, mussels and SPMDs had similar uptake rates for all compounds in this study, excluding p,p′-DDT and dieldrin. Contaminant elimination took place more rapidly in mussels, implying that SPMDs are better candidates for detecting episodic discharge of organic contaminants.  相似文献   

Interactive Effects of UV-B Radiation and Chemical Contamination on Physiological Parameters in the Lichen Ramalina lacera     

Jacob Garty  Tal Levin  Haya Lehr  Sharon Tomer  Ayala Hochman 《Journal of Atmospheric Chemistry》2004,49(1-3):267-289

To assess the impact of ultraviolet B (UV-B) radiation under laboratory conditions on lichens from different biomonitoring sites, thalli of the lichen Ramalina lacera were transplanted from a clean air site to nine different polluted sites in Israel. Our objective was to determine the probability of synergistic/antagonistic effects on physiological parameters by considering two stressors: chemical contamination and UV-B. Exposure to both airborne pollutants in the field and subsequent UV-B radiation in the laboratory which led to a severe disintegration of cell membranes, followed by electrolyte leakage, indicate the probability of a synergistic effect. The impairment of the potential quantum yield of electron transfer through photosystem II (PSII) of photosynthesis indicated by a significant decrease of the ratio F_v/F_m, further demonstrated the synergistic effect of both chemical contamination and UV-B radiation. Besides enlarged amounts of stress-ethylene in lichens at contaminated sites, the reduced levels of ethylene production upon UV-B radiation in the present study suggest the likelihood of an antagonistic effect of xenobiotic elements and UV-B radiation as a result of an impaired ethylene-producing system.  相似文献   

Thermal expansion coefficients for indialite,emerald, and beryl     

John L. Schlenker  G. V. Gibbs  Elizabeth G. Hill  Sharon S. Crews  R. H. Myers 《Physics and Chemistry of Minerals》1977,1(3):243-255

Thermal expansion coefficients ?₁ and ?₃ calculated for the hexagonal minerals indialite, emerald and beryl are, in general, small with ?₃ being negative near room temperature. This unusual behavior leads to low volume coefficients of thermal expansion (β=2?₁+?₃) making these materials ideal ceramic bodies for catalyst carriers in air-pollution control. The temperature at which the c-cell edge length of beryl is a minimum is strongly dependent upon the presence of trace amounts of impurity atoms. This effect is ascribed to changes in the Grüneisen parameters.  相似文献