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61.
Lan‐ping Feng Lian Zhou Lu Yang Donald J. DePaolo Shuo‐Yun Tong Yong‐Sheng Liu Thomas L. Owens Shan Gao 《Geostandards and Geoanalytical Research》2017,41(1):93-106
Calcium isotopic compositions of sixteen Ca‐bearing USGS geological reference materials including igneous and sedimentary rocks are reported. Calcium isotopic compositions were determined in two laboratories (GPMR, State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, Wuhan; and CIG, Centre for Isotope Geochemistry, University of California, Berkeley) using the 42Ca‐48Ca double‐spike technique by thermal ionisation mass spectrometry. As opposed to common cation exchange resin, a micro‐column filled with Ca‐selective resin (DGA resin) was used in order to achieve high recovery (> 96%) and efficient separation of Ca from the sample matrix. The intermediate measurement precision was evaluated at 0.14‰ (2s) for δ44/40CaSRM915a at GPMR, based on replicate measurements of pure Ca reference material NIST SRM 915a, NIST SRM 915b and seawater. Overall, the measurement uncertainties in both laboratories were better than 0.15‰ at the 2s level. Result validation was carried out for all available data sets. The Ca isotopic compositions of USGS reference materials are not only in agreement between GPMR and CIG, but also in agreement with previously published data within quoted uncertainties. The comprehensive data set reported in this study serves as a reference for both quality assurance and interlaboratory comparison of high precision Ca isotopic study. 相似文献
62.
W. R. Boynton J. D. Hagy J. C. Cornwell W. M. Kemp S. M. Greene M. S. Owens J. E. Baker R. K. Larsen 《Estuaries and Coasts》2008,31(4):623-651
Multi-year nitrogen (N) and phosphorus (P) budgets were developed for the Patuxent River estuary, a seasonally stratified
and moderately eutrophic tributary of Chesapeake Bay. Major inputs (point, diffuse, septic, and direct atmospheric) were measured
for 13 years during which, large reductions in P and then lesser reductions in N-loading occurred due to wastewater treatment
plant improvements. Internal nutrient losses (denitrification and long-term burial of particulate N and P) were measured in
tidal marshes and sub-tidal sediments throughout the estuary as were nutrient storage in the water column, sediments, and
biota. Nutrient transport between the oligohaline and mesohaline zones and between the Patuxent and Chesapeake Bay was estimated
using a salt and water balance model. Several major nutrient recycling terms were directly and indirectly evaluated and compared
to new N and P inputs on seasonal and annual time-scales. Major findings included: (1) average terrestrial and atmospheric
inputs of N and P were very close to the sum of internal losses plus export, suggesting that dominant processes are captured
in these budgets; (2) both N and P export were a small fraction (13% and 28%, respectively) of inputs, about half of that
expected for N based on water residence times, and almost all exported N and P were in organic forms; (3) the tidal marsh-oligohaline
estuary, which by area comprised ~27% of the full estuarine system, removed about 46% and 74% of total annual upland N and
P inputs, respectively; (4) recycled N and P were much larger sources of inorganic nutrients than new inputs during warm seasons
and were similar in magnitude even during cold seasons; (5) there was clear evidence that major estuarine processes responded
rapidly to inter-annual nutrient input variations; (6) historical nutrient input data and nutrient budget data from drought
periods indicated that diffuse nutrient sources were dominant and that N loads need to be reduced by about 50% to restore
water quality conditions to pre-eutrophic levels. 相似文献
63.
Linh Hoang Elliot M. Schneiderman Karen E.B. Moore Rajith Mukundan Emmet M. Owens Tammo S. Steenhuis 《水文研究》2017,31(12):2226-2243
Saturation‐excess runoff is the major runoff mechanism in humid well‐vegetated areas where infiltration rates often exceed rainfall intensity. Although the Soil and Water Assessment Tool (SWAT) is one of the most widely used models, it predicts runoff based mainly on soil and land use characteristics, and is implicitly an infiltration‐excess runoff type of model. Previous attempts to incorporate the saturation‐excess runoff mechanism in SWAT fell short due to the inability to distribute water from one hydrological response unit to another. This paper introduces a modified version of SWAT, referred to as SWAT‐Hillslope (SWAT‐HS). This modification improves the simulation of saturation‐excess runoff by redefining hydrological response units based on wetness classes and by introducing a surface aquifer with the ability to route interflow from “drier” to “wetter” wetness classes. Mathematically, the surface aquifer is a nonlinear reservoir that generates rapid subsurface stormflow as the water table in the surface aquifer rises. The SWAT‐HS model was tested in the Town Brook watershed in the upper reaches of the West Branch Delaware River in the Catskill region of New York, USA. SWAT‐HS predicted discharge well with a Nash‐Sutcliffe Efficiency of 0.68 and 0.87 for daily and monthly time steps. Compared to the original SWAT model, SWAT‐HS predicted less surface runoff and groundwater flow and more lateral flow. The saturated areas predicted by SWAT‐HS were concentrated in locations with a high topographic index and were in agreement with field observations. With the incorporation of topographic characteristics and the addition of the surface aquifer, SWAT‐HS improved streamflow simulation and gave a good representation of saturated areas on the dates that measurements were available. SWAT‐HS is expected to improve water quality model predictions where the location of the surface runoff matters. 相似文献
64.
The role of channel and floodplain storage in the suspended sediment budget of the River Ouse, Yorkshire, UK 总被引:2,自引:0,他引:2
This study attempts to quantify the amount of fine-grained (ca. < 150 μm) sediment stored on the floodplains and on the channel bed of the non-tidal sections of the main channels in the catchment of the River Ouse (3315 km2) and of one of its tributaries, the River Waarfe (818 km2), in Yorkshire, UK. Caesium-137 analyses of floodplain sediment cores were used to quantify the amount of Iloodplain deposition as a result of overbank flooding during the last ca. 40 years. A combination of bulk and sectioned cores were collected along transects perpendicular to the channel at 26 sites throughout the study basins. In general, rates of overbank sedimentation decrease with distance from the channel. The average values for individual transects range between 0.010 and 0.554 g cm−2 year−1. Floodplain storage along the main channels of the Ouse and Wharfe basins accounts for 60645 and 10325 t year−1, respectively, and represents a net loss from the system. The amount of fine-grained sediment stored on the channel bed was estimated by a survey undertaken in August 1996, during which the fine material deposited on the bed was resuspended and its mass estimated at 16 locations. The average values for the individual locations range between 0.017 and 0.924 g cm−2 and tend to increase downstream. The total channel bed storage at the time of sampling in 1996 was estimated to be 16076 and 1866 t for the Ouse and Wharfe basins, respectively. It is assumed that channel bed storage is seasonal and that no net loss to the system occurs at the annual timescale. Floodplain storage for the Ouse and Wharfe basins represents 39 and 49%, and channel bed storage equals 10 and 9%, respectively, of the annual suspended sediment load (1995–1996) delivered to the channel system. These results have important implications for the routing of fine-grained sediment and sediment-associated contaminants in drainage basins, and for the interpretation of downstream sediment yields in terms of upstream sediment mobilisation. 相似文献
65.
A two-dimensional finite difference numerical model, capable of predicting depth-averaged tidal flow fields in coastal and estuarine waters, has been extended to include tide-induced non-cohesive sediment transport processes. The partial differential equations governing the conservation of mass, momentum and suspended sediment in an incompressible turbulent flow are included in a depth-integrated form in the model. For the representation of the processes of erosion and deposition of sediment from the bed an empirically based source-sink term was refined, based on the results of three mobile bed flume studies. The model has been tested by simulating tidal flows and suspended sediment fluxes in two estuaries, with particular application to the Humber estuary in the U.K. The model was calibrated and found to produce an encouraging degree of agreement between the numerical predictions and corresponding field measurements for this estuary. Furthermore, the predicted gross deposition and erosion features of the estuary were found to be in close agreement with interpretations from Eulerian tidal residual predictions. 相似文献
66.
Susan Owens 《Global Environmental Change》2010,20(3):394-401
This paper is concerned with environmental governance and policy formation in the area of climate change. Specifically, it examines a decision by the UK Government in 2003 to adopt a demanding, long-term CO2 emissions reduction target, following the advice of one of its longest standing environmental advisory bodies, the Royal Commission on Environmental Pollution. It explores the origins of the Commission's recommendation and the reasons for its relatively rapid uptake in public policy. It argues that in both cases, a complex mix of structural and contingent, cognitive and non-cognitive factors can be identified, operating at different levels of governance. Finally, the paper reflects on what we might learn from this particular case about policy processes and the role of knowledge and expert advice within them. 相似文献
67.
T. Kosugi K. Matsuzaki T. Sakao T. Shimizu Y. Sone S. Tachikawa T. Hashimoto K. Minesugi A. Ohnishi T. Yamada S. Tsuneta H. Hara K. Ichimoto Y. Suematsu M. Shimojo T. Watanabe S. Shimada J. M. Davis L. D. Hill J. K. Owens A. M. Title J. L. Culhane L. K. Harra G. A. Doschek L. Golub 《Solar physics》2007,243(1):3-17
The Hinode satellite (formerly Solar-B) of the Japan Aerospace Exploration Agency’s Institute of Space and Astronautical Science (ISAS/JAXA) was successfully launched
in September 2006. As the successor to the Yohkoh mission, it aims to understand how magnetic energy gets transferred from the photosphere to the upper atmosphere and results
in explosive energy releases. Hinode is an observatory style mission, with all the instruments being designed and built to work together to address the science
aims. There are three instruments onboard: the Solar Optical Telescope (SOT), the EUV Imaging Spectrometer (EIS), and the
X-Ray Telescope (XRT). This paper provides an overview of the mission, detailing the satellite, the scientific payload, and
operations. It will conclude with discussions on how the international science community can participate in the analysis of
the mission data.
T. Kosugi deceased 26 November 2006. 相似文献
68.
69.
FVCOM model estimate of the location of Air France 447 总被引:2,自引:0,他引:2
Changsheng Chen Richard Limeburner Guoping Gao Qichun Xu Jianhua Qi Pengfei Xue Zhigang Lai Huichan Lin Robert Beardsley Breck Owens Barry Carlson 《Ocean Dynamics》2012,62(6):943-952
On June 1, 2009, Air France AF447 disappeared in the Equatorial Atlantic Ocean en route from Rio de Janeiro, Brazil, to Paris, France. On June 6–19, 2009, bodies and debris from the aircraft were recovered floating in the equatorial ocean. This paper describes efforts on using the global–local nested finite volume community ocean model (FVCOM) to model reversely the tracks of bodies and debris back to the time of the crash and to help searchers locate the cockpit voice and flight data recorders and learn why this tragic accident occurred. To validate the reliability and reality of FVCOM, eight surface drifters were deployed by the French Bureau d’Enquêtes et d’Analyses pour la sécurité de l’aviation civile (BEA) near the last known position in early June 2010 for a period of 3?weeks. These drifter data were used to optimize the spatial and temporal correlation scales of the adaptive sampling data assimilation method of FVCOM. Applying an optimized FVCOM system to assimilate all available drifter- and float-tracking-derived currents in May–June 2009 under three different wind conditions, we reproduced the June 2009 current fields in the area near the LKP and used these fields to reversely track bodies and debris from locations where they were found to the time when the crash occurred. Possible locations for the crashed plane were suggested based on our model results and were made available to the French investigators and the Woods Hole Oceanographic Institution REMUS autonomous underwater vehicle Operations Group who successfully located the aircraft debris field in April 2011 on the seafloor at a depth of 3,900?m. 相似文献
70.
We present the results of a study of solar wind velocity and magnetic field correlation lengths over the last 35 years. The
correlation length of the magnetic field magnitude λ
|B| increases on average by a factor of two at solar maxima compared to solar minima. The correlation lengths of the components
of the magnetic field lBXYZ\lambda_{B_{XYZ}} and of the velocity lVYZ\lambda_{V_{YZ}} do not show this change and have similar values, indicating a continual turbulent correlation length of around 1.4×106 km. We conclude that a linear relation between λ
|B|, VB
2, and Kp suggests that the former is related to the total magnetic energy in the solar wind and an estimate of the average
size of geoeffective structures, which is, in turn, proportional to VB
2. By looking at the distribution of daily correlation lengths we show that the solar minimum values of λ
|B| correspond to the turbulent outer scale. A tail of larger λ
|B| values is present at solar maximum causing the increase in mean value. 相似文献