Plutonium oxidation state distributions in the Pacific Ocean during 1980–1981     

Donald M. Nelson  Anne E. Carey  Vaughan T. Bowen 《Earth and Planetary Science Letters》1984,68(3):422-430

The concentration of plutonium and its oxidation state distribution have been measured as a function of depth at three locations in the North Pacific Ocean. Concentration profiles were similar to those observed in the same area during 1974 with primary maxima at depths of a few hundred meters below the surface and secondary maxima near the bottom. Oxidation state distribution profiles were similar at the three locations with plutonium about equally divided between the reduced and oxidized forms except near the bottom. There the oxidized form was more abundant and comprised ～ 90% of the total plutonium. No major change in oxidation state occurred at the depths of the shallow concentration maxima suggesting that their formation and persistence were not dependent upon a redox change. The concentration maxima near the bottom coincided with the enhanced abundance of the poorly sorbed oxidized form suggesting that they resulted from the loss of oxidized plutonium from the sediments.  相似文献   

Pre-Impact Mid-IR and Optical Observations of Comet 9P/Tempel 1     

H.-U. Kaeufl  T. Bonev  H. Boehnhardt  Y. R. Fernandez  C. Lisse 《Earth, Moon, and Planets》2005,97(3-4):331-339

Comet 9P/Tempel 1, the target of the Deep Impact mission, has been intensively observed for a long time period before the encounter. Pre-impact ground based monitoring of the comet was an important prerequisite for the success of the first space experiment in which a comet is treated by an artificial impact. It provided the background data needed to disentangle the features caused by the impact from variations caused by the natural activity of the comet. In this paper we present results from the ESO-monitoring of the comet, conducted in the thermal infrared and optical spectral ranges during several months before the Deep Impact encounter with the comet.  相似文献   

Source-rock identification by isotope analyses of natural gases from fields in the Val Verde and Delaware basins,west Texas   总被引：1，自引：0，他引：1  

Wolfgang J. Stahl  Byrl D. Carey 《Chemical Geology》1975,16(4):257-267

Methane, ethane and propane carbon-isotope ratios are controlled by the maturity of the organic material in their source rocks. Isotope data of natural gases can be used in some instances to identify their source rocks. Migration seems to cause no essential changes in the carbon-isotopic composition of the gas components. Under certain circumstances the isotope-maturity relationship can be used in approximating displacement along fault systems or in determining the direction of gas migration.  相似文献   

Large-Scale Structure of the Carina Nebula     

Smith N  Egan MP  Carey S  Price SD  Morse JA  Price PA 《The Astrophysical journal》2000,532(2):L145-L148

Observations obtained with the Midcourse Space Experiment (MSX) satellite reveal for the first time the complex mid-infrared morphology of the entire Carina Nebula (NGC 3372). On the largest size scale of approximately 100 pc, the thermal infrared emission from the giant H ii region delineates one coherent structure: a (somewhat distorted) bipolar nebula with the major axis perpendicular to the Galactic plane. The Carina Nebula is usually described as an evolved H ii region that is no longer actively forming stars, clearing away the last vestiges of its natal molecular cloud. However, the MSX observations presented here reveal numerous embedded infrared sources that are good candidates for sites of current star formation. Several compact infrared sources are located at the heads of dust pillars or in dark globules behind ionization fronts. Because their morphology suggests a strong interaction with the peculiar collection of massive stars in the nebula, we speculate that these new infrared sources may be sites of triggered star formation in NGC 3372.  相似文献   

Lightning activity related to satellite and radar observations of a mesoscale convective system over Texas on 7–8 April 2002     

Nikolai Dotzek  Robert M. Rabin  Lawrence D. Carey  Donald R. MacGorman  Tracy L. McCormick  Nicholas W. Demetriades  Martin J. Murphy  Ronald L. Holle 《Atmospheric Research》2005,76(1-4):127

A multi-sensor study of the leading-line, trailing-stratiform (LLTS) mesoscale convective system (MCS) that developed over Texas in the afternoon of 7 April 2002 is presented. The analysis relies mainly on operationally available data sources such as GOES East satellite imagery, WSR-88D radar data and NLDN cloud-to-ground flash data. In addition, total lightning information in three dimensions from the LDAR II network in the Dallas–Ft. Worth region is used.GOES East satellite imagery revealed several ring-like cloud top structures with a diameter of about 100 km during MCS formation. The Throckmorton tornadic supercell, which had formed just ahead of the developing linear MCS, was characterized by a high CG+ percentage below a V-shaped cloud top overshoot north of the tornado swath. There were indications of the presence of a tilted electrical dipole in this storm. Also this supercell had low average CG− first stroke currents and flash multiplicities. Interestingly, especially the average CG+ flash multiplicity in the Throckmorton storm showed oscillations with an estimated period of about 15 min.Later on, in the mature LLTS MCS, the radar versus lightning activity comparison revealed two dominant discharge regions at the back of the convective leading edge and a gentle descent of the upper intracloud lightning region into the trailing stratiform region, apparently coupled to hydrometeor sedimentation. There was evidence for an inverted dipole in the stratiform region of the LLTS MCS, and CG+ flashes from the stratiform region had high first return stroke peak currents.  相似文献   

Heat as a groundwater tracer in shallow and deep heterogeneous media: Analytical solution,spreadsheet tool,and field applications          下载免费PDF全文

Barret L. Kurylyk  Dylan J. Irvine  Sean K. Carey  Martin A. Briggs  Dale D. Werkema  Mariah Bonham 《水文研究》2017,31(14):2648-2661

Groundwater flow advects heat, and thus, the deviation of subsurface temperatures from an expected conduction‐dominated regime can be analysed to estimate vertical water fluxes. A number of analytical approaches have been proposed for using heat as a groundwater tracer, and these have typically assumed a homogeneous medium. However, heterogeneous thermal properties are ubiquitous in subsurface environments, both at the scale of geologic strata and at finer scales in streambeds. Herein, we apply the analytical solution of Shan and Bodvarsson ( 2004 ), developed for estimating vertical water fluxes in layered systems, in 2 new environments distinct from previous vadose zone applications. The utility of the solution for studying groundwater‐surface water exchange is demonstrated using temperature data collected from an upwelling streambed with sediment layers, and a simple sensitivity analysis using these data indicates the solution is relatively robust. Also, a deeper temperature profile recorded in a borehole in South Australia is analysed to estimate deeper water fluxes. The analytical solution is able to match observed thermal gradients, including the change in slope at sediment interfaces. Results indicate that not accounting for layering can yield errors in the magnitude and even direction of the inferred Darcy fluxes. A simple automated spreadsheet tool (Flux‐LM) is presented to allow users to input temperature and layer data and solve the inverse problem to estimate groundwater flux rates from shallow (e.g., <1 m) or deep (e.g., up to 100 m) profiles. The solution is not transient, and thus, it should be cautiously applied where diel signals propagate or in deeper zones where multi‐decadal surface signals have disturbed subsurface thermal regimes.  相似文献   

The effect of riparian land use on transport hydraulics in agricultural headwater streams located in northeast Ohio,USA     

Kyle S. Herrman  Virginie Bouchard  Tim Granata  Anne E. Carey  Richard H. Moore 《水文研究》2010,24(1):1-12

This study examined if riparian land use (forested vs agricultural) affects hydraulic transport in headwater streams located in an agriculturally fragmented watershed. We identified paired 50‐m reaches (one reach in agricultural land use and the other in forested land use) along three headwater streams in the Upper Sugar Creek Watershed in northeast Ohio, USA (40° 51′42″N, 81° 50′29″W). Using breakthrough curves obtained by Rhodamine WT slug injections and the one‐dimensional transport with inflow and storage model (OTIS), hydraulic transport parameters were obtained for each reach on six different occasions (n = 36). Relative transient storage (A_S:A) was similar between both reach types (As: A = 0·3 ± 0·1 for both agricultural and forested reaches). Comparing values of F_med²⁰⁰ to those in the literature indicates that the effect of transient storage was moderately high in the study streams in the Upper Sugar Creek Watershed. Examining travel times revealed that overall residence time (HRT) and residence time in transient storage (T_STO) were both longer in forested reaches (forested HRT = 19·1 ± 11·5 min and T_STO = 4·0 ± 3·8 min; agricultural HRT = 9·3 ± 5·3 min and T_STO = 1·7 ± 1·4 min). We concluded that the effect of transient storage on solute transport was similar between the forested and agricultural reaches but the forested reaches had a greater potential to retain solutes as a result of longer travel times. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   

Mid-frequency measurements of array signal and noisecharacteristics     

Carey  W.M. Reese  J.W. Stuart  C.E. 《Oceanic Engineering, IEEE Journal of》1997,22(3):548-565

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Modal analysis of geoacoustic influences on shallow-waterpropagation     

Cederberg  R.J. Carey  W.M. Siegmann  W.L. 《Oceanic Engineering, IEEE Journal of》1997,22(2):237-244

Features observed in horizontal wavenumber spectra from low-frequency acoustic measurements taken off the New Jersey Shelf are analyzed through forward modeling using PE models. Environmental models which produce very good agreement with relative intensity data may only match wavenumbers of lower order modes. A prominent feature in contours of modal amplitude versus horizontal wavenumber and depth is the presence of double images of some higher order modes. Two possible causes of this phenomenon are examined. Range dependence in the environment can produce multiple modal images, but the magnitudes of variations required are much larger than those expected at the experiment site. The more likely cause of the double modes is shown to be a duct deep (two acoustic wavelengths) within the sediment. It produces modes with wavenumbers that are close together and with shapes that are very similar in the water column. Comparisons of model predictions with 50-Hz experimental wavenumbers and mode shapes show good agreement, except for amplitudes of some higher order modes. Predictions at 75 Hz typically require more detailed information about the sediment structure in order to accurately match all the features of higher order modes in the data  相似文献   

Stable isotopes of water reveal differences in plant – soil water relationships across northern environments     

Doerthe Tetzlaff  James Buttle  Sean K. Carey  Matthew J. Kohn  Hjalmar Laudon  James P. McNamara  Aaron Smith  Matthias Sprenger  Chris Soulsby 《水文研究》2021,35(1):e14023

We compared stable isotopes of water in plant stem (xylem) water and soil collected over a complete growing season from five well-known long-term study sites in northern/cold regions. These spanned a decreasing temperature gradient from Bruntland Burn (Scotland), Dorset (Canadian Shield), Dry Creek (USA), Krycklan (Sweden), to Wolf Creek (northern Canada). Xylem water was isotopically depleted compared to soil waters, most notably for deuterium. The degree to which potential soil water sources could explain the isotopic composition of xylem water was assessed quantitatively using overlapping polygons to enclose respective data sets when plotted in dual isotope space. At most sites isotopes in xylem water from angiosperms showed a strong overlap with soil water; this was not the case for gymnosperms. In most cases, xylem water composition on a given sampling day could be better explained if soil water composition was considered over longer antecedent periods spanning many months. Xylem water at most sites was usually most dissimilar to soil water in drier summer months, although sites differed in the sequence of change. Open questions remain on why a significant proportion of isotopically depleted water in plant xylem cannot be explained by soil water sources, particularly for gymnosperms. It is recommended that future research focuses on the potential for fractionation to affect water uptake at the soil-root interface, both through effects of exchange between the vapour and liquid phases of soil water and the effects of mycorrhizal interactions. Additionally, in cold regions, evaporation and diffusion of xylem water in winter may be an important process.  相似文献