Temporal and spatial dynamics of urea uptake and regeneration rates and concentrations in Chesapeake Bay     

Michael?W.?LomasEmail author  T.?Mark Trice  Patricia?M.?Glibert  Deborah?A.?Bronk  James?J.?McCarthy 《Estuaries and Coasts》2002,25(3):469-482

We examined the temporal and spatial variability of urea concentrations and urea uptake and regeneration rates collected on cruises along the longitudinal axis of the Chesapeake Bay between 1972 and 1998. Interannually, mean Bay-wide surface urea concentrations ranged between 0.49 and 0.91 μg-at N l^?1 with a nearly 50% decrease in surface concentrations observed between 1988 and 1998. Concentrations of urea from samples collected within ～1 m of the bottom were generally higher and much more varable than surface samples. Seasonally, two different patterns were observed in mean Bay-wide surface urea concentrations. Urea concentrations from near surface waters exhibited a clear summer peak for 1988 through 1994, while for 1973 and 1996 to 1998 a distinct winter-spring peak in concentration was observed. Urea concentrations from deeper waters showed a similar seasonal trend each year with peak concentrations measured in spring. Spatially, urea concentrations in the surface waters decreased in a conservative-type pattern from 0.91 μg-at N I^?1 at the freshwater end member to 0.46 μg-at N I^?1 at the ocean end member. Mean Bay-wide surface urea uptake rates displayed a seasonal pattern throughout the data set with maximum uptake rates (up to 0.33 μg-at N I^?1 h^?1) consistently observed during summer. Mean Bay-wide surface regeneration rates were highest but most variable during fall (1.63±0.82 μg-at N I^?1 h^?1). Mean urea uptake and regeneration rates displayed opposing spatial trends along the axis of the Bay with uptake rates being lowest in the North Bay where regeneration rates were highest. The average temporal and spatial patterns of urea concentration in Chesapeake Bay appear to reflect a balance between external inputs and internal biological recycling.  相似文献   

Ups and downs     

Peter Bond 《Astronomy& Geophysics》2000,41(5):5.25-5.27

Cluster goes up but will planetary programmes go down? Peter Bond reports on space mission plans and achievements.  相似文献   

Another Martian mystery     

Peter Bond  is the RAS PR Officer . 《Astronomy& Geophysics》2000,41(1):1.09-1.11

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“Placing” Interviews: Location and Scales of Power in Qualitative Research     

Sarah A. Elwood  Deborah G. Martin 《The Professional geographer》2000,52(4):649-657

For qualitative researchers, selecting appropriate sites in which to conduct interviews may seem to be a relatively simple research design issue. In fact it is a complicated decision with wide‐reaching implications. In this paper, we argue that the interview site itself embodies and constitutes multiple scales of spatial relations and meaning, which construct the power and positionality of participants in relation to the people, places, and interactions discussed in the interview. We illustrate how observation and analysis of interview sites can offer new insights with respect to research questions, help researchers understand and interpret interview material, and highlight particular ethical considerations that researchers need to address.  相似文献   

Application of hybrid numerical and analytical solutions for the simulation of coupled thermal,hydraulic, mechanical and chemical processes during fluid flow through a fractured rock     

Christopher McDermott  Alexander Bond  Andrew Fraser Harris  Neil Chittenden  Kate Thatcher 《Environmental Earth Sciences》2015,74(12):7837-7854

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The weathering and element fluxes from active volcanoes to the oceans: a Montserrat case study     

Morgan T. Jones  Deborah J. Hembury  Martin R. Palmer  Bill Tonge  W. George Darling  Susan C. Loughlin 《Bulletin of Volcanology》2011,73(3):207-222

The eruptions of the Soufrière Hills volcano on Montserrat (Lesser Antilles) from 1995 to present have draped parts of the island in fresh volcaniclastic deposits. Volcanic islands such as Montserrat are an important component of global weathering fluxes, due to high relief and runoff and high chemical and physical weathering rates of fresh volcaniclastic material. We examine the impact of the recent volcanism on the geochemistry of pre-existing hydrological systems and demonstrate that the initial chemical weathering yield of fresh volcanic material is higher than that from older deposits within the Lesser Antilles arc. The silicate weathering may have consumed 1.3% of the early CO₂ emissions from the Soufrière Hills volcano. In contrast, extinct volcanic edifices such as the Centre Hills in central Montserrat are a net sink for atmospheric CO₂ due to continued elevated weathering rates relative to continental silicate rock weathering. The role of an arc volcano as a source or sink for atmospheric CO₂ is therefore critically dependent on the stage it occupies in its life cycle, changing from a net source to a net sink as the eruptive activity wanes. While the onset of the eruption has had a profound effect on the groundwater around the Soufrière Hills center, the geochemistry of springs in the Centre Hills 5 km to the north appear unaffected by the recent volcanism. This has implications for the potential risk, or lack thereof, of contamination of potable water supplies for the island’s inhabitants.  相似文献   

A dearth of planetary transits in the direction of NGC 6940     

Ben Hood  rew Collier Cameron  Stephen R. Kane  D. M. Bramich  Keith Horne  Rachel A. Street  I. A. Bond  A. J. Penny  Y. Tsapras  A. Quirrenbach  N. Safizadeh  D. Mitchell  J. Cooke 《Monthly notices of the Royal Astronomical Society》2005,360(2):791-800

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Application of the finite difference method in seismic source and wave diffraction simulation     

M. Hong  L. J. Bond 《Geophysical Journal International》1986,87(3):731-752

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First results from the arcminute cosmology bolometer array receiver     

M. C. Runyan  P. A. R. Ade  J. J. Bock  J. R. Bond  C. Cantalupo  C. R. Contaldi  M. D. Daub  J. H. Goldstein  P. L. Gomez  W. L. Holzapfel  C. L. Kuo  A. E. Lange  M. Lueker  M. Newcomb  J. B. Peterson  D. Pogosyan  A. K. Romer  J. Ruhl  E. Torbet  D. Woolsey 《New Astronomy Reviews》2003,47(11-12):915

We review the first science results from the Arcminute Cosmology Bolometer Array Receiver (ACBAR); a multi-frequency millimeter-wave receiver optimized for observations of the Cosmic Microwave Background (CMB) and the Sunyaev–Zel’dovich (SZ) effect in clusters of galaxies. ACBAR was installed on the 2 m Viper telescope at the South Pole in January 2001 and the results presented here incorporate data through July 2002. We present the power spectrum of the CMB at 150 GHz over the range ℓ=150–3000 measured by ACBAR as well as estimates for the values of the cosmological parameters within the context of ΛCDM models. We find that the inclusion of Ω_Λ greatly improves the fit to the power spectrum. We also observe a slight excess of small-scale anisotropy at 150 GHz; if interpreted as power from the SZ effect of unresolved clusters, the measured signal is consistent with CBI and BIMA within the context of the SZ power spectrum models tested.  相似文献   

Hello Moon, goodbye Jupiter     

Peter Bond 《Astronomy& Geophysics》2003,44(6):6.29-6.31

The last Great Observatory takes its place, Europe heads for the Moon, and Galileo ends its Jovian adventure. Peter Bond reports.  相似文献