A preliminary methods comparison for measurement of dissolved organic nitrogen in seawater   总被引：2，自引：0，他引：2  

Jonathan H. Sharp  Kathrine R. Rinker  Karen B. Savidge  Jeffrey Abell  Jean Yves Benaim  Deborah Bronk  David J. Burdige  Gustave Cauwet  Wenhao Chen  Marylo D. Doval  Dennis Hansell  Charles Hopkinson  Gerhard Kattner  Nancy Kaumeyer  Karen J. McGlathery  Jeffrey Merriam  Nick Morley  Klaus Nagel  Hiroshi Ogawa  Carol Pollard  Mireille Pujo-Pay  Patrick Raimbault  Raymond Sambrotto  Sybil Seitzinger  Georgina Spyres  Frank Tirendi  Ted W. Walsh  C. S. Wong 《Marine Chemistry》2002,78(4)

Routine determination of dissolved organic nitrogen (DON) is performed in numerous laboratories around the world using one of three families of methods: UV oxidation (UV), persulfate oxidation (PO), or high temperature combustion (HTC). Essentially all routine methods measure total dissolved nitrogen (TDN) and calculate DON by subtracting the dissolved inorganic nitrogen (DIN). While there is currently no strong suggestion that any of these methods is inadequate, there are continuing suspicions of slight inaccuracy by UV methods.This is a report of a broad community methods comparison where 29 sets (7 UV, 13 PO, and 9 HTC) of TDN analyses were performed on five samples with varying TDN and DIN concentrations. Analyses were done in a “blind” procedure with results sent to the first author. With editing out one set of extreme outliers (representing 5 out of 145 ampoules analyzed), the community comparability for analyzing the TDN samples was in the 8–28% range (coefficient of variation representing one standard deviation for the five individual samples by 28 analyses). When DIN concentrations were subtracted uniformly (single DIN value for each sample), the comparability was obviously worse (19–46% cv). This comparison represents a larger and more diverse set of analyses, but the overall comparability is only marginally better than that of the Seattle workshop of a decade ago. Grouping methods, little difference was seen other than inconclusive evidence that the UV methods gave TDN values for several of the samples higher than HTC methods. Since there was much scatter for each of the groups of methods and for all analyses when grouped, it is thought that more uniformity in procedures is probably needed. An important unplanned observation is that variability in DIN analyses (used in determining the final analyte in most UV and PO methods) is essentially as large as the variability in the TDN analyses.This exercise should not be viewed as a qualification exercise for the analysts, but should instead be considered a broad preliminary test of the comparison of the families of methods being used in various laboratories around the world. Based on many independent analyses here, none of the routinely used methods appears to be grossly inaccurate, thus, most routine TDN analyses being reported in the literature are apparently accurate. However, it is not reassuring that the ability of the international community to determine DON in deep oceanic waters continues to be poor. It is suggested that as an outgrowth of this paper, analysts using UV and PO methods experiment and look more carefully at the completeness of DIN conversion to the final analyte and also at the accuracy of their analysis of the final analyte. HTC methods appear to be relatively easy and convenient and have potential for routine adoption. Several of the authors of this paper are currently working together on an interlaboratory comparison on HTC methodology.  相似文献   

Vestan lithologies mapped by the visual and infrared spectrometer on Dawn     

Eleonora Ammannito  M. Cristina De Sanctis  Fabrizio Capaccioni  M. Teresa Capria  F. Carraro  Jean‐Philippe Combe  Sergio Fonte  Alessandro Frigeri  Steven P. Joy  Andrea Longobardo  Gianfranco Magni  Simone Marchi  Thomas B. McCord  Lucy A. McFadden  Harry Y. McSween  Ernesto Palomba  Carle M. Pieters  Carol A. Polanskey  Carol A. Raymond  Jessica M. Sunshine  Federico Tosi  Francesca Zambon  Christopher T. Russell 《Meteoritics & planetary science》2013,48(11):2185-2198

We present global lithological maps of the Vestan surface based on Dawn mission's Visible InfraRed (VIR) Spectrometer acquisitions with a spatial sampling of 200 m. The maps confirm the results obtained with the data set acquired by VIR with a spatial sampling of 700 m, that the reflectance spectra of Vesta's surface are dominated by pyroxene absorptions that can be interpreted within the context of the distribution of howardites, eucrites, and diogenites (HEDs). The maps also partially agree with the ground and Hubble Space Telescope observations: they confirm the background surface being an assemblage of howardite or polymict eucrite, as well as the location of a diogenitic‐rich spot; however, there is no evidence of extended olivine‐rich regions in the equatorial latitudes. Diogenite is revealed on the Rheasilvia basin floor, indicating that material of the lower crust/mantle was exposed. VIR also detected diogenites along the scarp of Matronalia Rupes, and the rims of Severina and a nearby, unnamed crater, and as ejecta of Antonia crater. The diogenite distribution is fully consistent with petrological constraints; although the mapped distribution does not provide unambiguous constraints, it favors the hypothesis of a magma ocean.  相似文献   

Inventory and Ventilation Efficiency of Nonnative and Native Phragmites australis (Common Reed) in Tidal Wetlands of the Chesapeake Bay     

Mirela G. Tulbure  Dana M. Ghioca-Robrecht  Carol A. Johnston  Dennis F. Whigham 《Estuaries and Coasts》2012,35(5):1353-1359

Nonnative Phragmites is among the most invasive plants in the U.S. Atlantic coast tidal wetlands, whereas the native Phragmites has declined. Native and nonnative patches growing side by side provided an ideal setting for studying mechanisms that enable nonnative Phragmites to be a successful invader. We conducted an inventory followed by genetic analysis and compared differences in growth patterns and ventilation efficiency between adjacent native and nonnative Phragmites stands. Genetic analysis of 212 patches revealed that only 14 were native suggesting that very few native Phragmites populations existed in the study area. Shoot density decreased towards the periphery of native patches, but not in nonnative patches. Ventilation efficiency was 300?% higher per unit area for nonnative than native Phragmites, likely resulting in increased oxidation of the rhizosphere and invasive behavior of nonnative Phragmites. Management of nonnative Phragmites stands should include mechanisms that inhibit pressurized ventilation of shoots.  相似文献   

Multitemporal ALSM change detection,sediment delivery,and process mapping at an active earthflow   总被引：1，自引：0，他引：1  

Stephen B. DeLong  Carol S. Prentice  George E. Hilley  Yael Ebert 《地球表面变化过程与地形》2012,37(3):262-272

Remote mapping and measurement of surface processes at high spatial resolution is among the frontiers in Earth surface process research. Remote measurements that allow meter‐scale mapping of landforms and quantification of landscape change can revolutionize the study of landscape evolution on human timescales. At Mill Gulch in northern California, USA, an active earthflow was surveyed in 2003 and 2007 by airborne laser swath mapping (ALSM), enabling meter‐scale quantification of landscape change. We calculate four‐year volumetric flux from the earthflow and compare it to long‐term catchment average erosion rates from cosmogenic radionuclide inventories from adjacent watersheds. We also present detailed maps of changing features on the earthflow, from which we can derive velocity estimates and infer dominant process. These measurements rely on proper digital elevation model (DEM) generation and a simple surface‐matching technique to align the multitemporal data in a manner that eliminates systematic error in either dataset. The mean surface elevation of the earthflow and an opposite slope that was directly influenced by the earthflow decreased 14 ± 1 mm/yr from 2003 to 2007. By making the conservative assumption that these features were the dominant contributor of sediment flux from the entire Mill Gulch drainage basin during this time interval, we calculate a minimum catchment‐averaged erosion rate of 0·30 ± 0·02 mm/yr. Analysis of beryllium‐10 (¹⁰Be) concentrations in fluvial sand from nearby Russian Gulch and the South Fork Gualala River provide catchment averaged erosion rates of 0·21 ± 0·04 and 0·23 ± 0·03 mm/yr respectively. From translated landscape features, we can infer surface velocities ranging from 0·5 m/yr in the wide upper ‘source’ portion of the flow to 5 m/yr in the narrow middle ‘transport’ portion of the flow. This study re‐affirms the importance of mass wasting processes in the sediment budgets of uplifting weak lithologies. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

Photometric redshifts in the SWIRE Survey     

Michael Rowan-Robinson  Tom Babbedge  Seb Oliver  Markos Trichas  Stefano Berta  Carol Lonsdale  Gene Smith  David Shupe  Jason Surace  Stephane Arnouts  Olivier Ilbert  Olivier Le Févre  Alejandro Afonso-Luis  Ismael Perez-Fournon  Evanthia Hatziminaoglou  Mari Polletta  Duncan Farrah  Mattia Vaccari 《Monthly notices of the Royal Astronomical Society》2008,386(2):697-714

  相似文献   

Exploring the role of the amateur in the production and circulation of meteorological knowledge     

Georgina H. Endfield  Carol Morris 《Climatic change》2012,113(1):69-89

There is a growing scholarship on the role of the amateur, and amateur societies, in the production and circulation of weather and climate knowledge in the past. Yet relatively little attention has been paid to the actual and potential contribution of contemporary amateur meteorologists in this respect. In this paper we first examine the importance of the amateur historically in the production of local weather knowledge and also in the emergence of professional meteorology. Drawing on semi-structured interviews with members of one contemporary UK based amateur meteorological organisation??the Climatological Observers Link (COL)??we then investigate the nature and extent of contemporary amateur meteorologists?? contributions to a wide range of different ??publics?? today, which include both popular and professional communities. Finally, we interrogate our interview data to identify whether COL members themselves recognise a wider role for their expertise at a time of increasing popular and scientific interest in weather and climate and in an era when the inclusion of non-certified experts in policy decision making processes is being advocated.  相似文献   

Mineralogical,geochemical, and microbial investigation of a sulfide-rich tailings deposit characterized by neutral drainage     

Matthew B.J. Lindsay  Peter D. Condon  John L. Jambor  Kerry G. Lear  David W. Blowes  Carol J. Ptacek 《Applied Geochemistry》2009

Mineralogical, geochemical and microbial characterization of tailings solids from the Greens Creek Mine, Juneau, Alaska, was performed to evaluate mechanisms controlling aqueous geochemistry of near-neutral pH pore water and drainage. Core samples of the tailings were collected from five boreholes ranging from 7 to 26 m in depth. The majority of the 51 samples (77%) were collected from the vadose zone, which can extend >18 m below the tailings surface. Mineralogical investigation indicates that the occurrence of sulfide minerals follows the general order: pyrite [FeS₂] >> sphalerite [(Zn,Fe)S] > galena [PbS], tetrahedrite [(Fe,Zn,Cu,Ag)₁₂Sb₄S₁₃] > arsenopyrite [FeAsS] and chalcopyrite [CuFeS₂]. Pyrite constitutes <20 to >35 wt.% of the tailings mineral assemblage, whereas dolomite [CaMg(CO₃)₂] and calcite [CaCO₃] are present at ?30 and 3 wt.%, respectively. The solid-phase geochemistry generally reflects the mineral assemblage. The presence of additional trace elements, including Cd, Cr, Co, Mo, Ni, Se and Tl, is attributed to substitution into sulfide phases. Results of acid–base accounting (ABA) underestimated both acid-generating potential (AP) and neutralization potential (NP). Recalculation of AP and NP based on solid-phase geochemistry and quantitative mineralogy yielded more representative results. Neutrophilic S-oxidizing bacteria (nSOB) and SO₄-reducing bacteria (SRB) are present with populations up to 10⁷ and 10⁵ cells g⁻¹, respectively. Acidophilic S-oxidizing bacteria (aSOB) and iron-reducing bacteria (IRB) were generally less abundant. Primary influences on aqueous geochemistry are sulfide oxidation and carbonate dissolution at the tailings surface, gypsum precipitation–dissolution reactions, as well as Fe reduction below the zone of sulfide oxidation. Pore-water pH values generally ranged from 6.5 to 7.5 near the tailings surface, and from approximately 7–8 below the oxidation zone. Elevated concentrations of dissolved SO₄, S₂O₃, Fe, Zn, As, Sb and Tl persisted under these conditions.  相似文献   

Ocean-bottom seismometer observations of seismic activity at Loihi Seamount,Hawaii     

Carol Bryan  Patricia Cooper 《Marine Geophysical Researches》1995,17(6):485-501

This study reports the result of deep ocean-bottom seismometer recording of an undersea volcanic event in progress. An array of five three-component, isolated sensor ocean-bottom seismometers (ISOBS) was deployed for 28 days on the summit and flanks of Loihi Seamount, Hawaii, to monitor seismicity. The deployment was prompted by reports from the Hawaiian Volcano Observatory (HVO) of a swarm of small-magnitude events located beneath the active submarine volcano in late September, 1986. Monitoring of this earthquake swarm by the University of Hawaii commenced 1 October 1986. Although seismicity tapered off rapidly after 11 October, more than 200 events were located. Systematic changes in spatial clustering during the initial swarm activity suggest changing patterns of stress within this crustal volume, possibly due to induced stress resulting from magma movement in the underlying crust or deep portions of the edifice.Most of the very shallow (< 10 km) events were located beneath the summit and southwest flank of the elongate edifice. No shallow tremor was observed despite a search through the data, although such tremor may have ceased prior to deployment of the ocean-bottom seismometers (OBS). Constraints on the association between seismicity and observed topographic and tectonic elements of Loihi are also of primary importance. Many of the earthquakes located near the steep flanks generated rock falls that were recorded on the OBSs. This is consistent with the results of dredge and bottom photography data indicating that the flanks are covered with fragments of shattered lava pillows and flows. Dike intrusion and mass wasting are major influences on the morphology of Loihi. Intact flows have been observed near the deep portion of the south rift zone; however, few events were located in that region during this swarm.  相似文献   

Copenhagen,Climate Science and the Emotional Geographies of Climate Change     

Carol Farbotko  Helen V. McGregor 《The Australian geographer》2010,41(2):159-166

The Pacific island nation-state of Tuvalu featured significantly at the Copenhagen Conference of Parties (COP) 15 climate change negotiations, where the vulnerability of Tuvalu to sea level rise and emotional outpourings of the Tuvaluan delegation contributed to the nation's prominence. In this paper we discuss the likely impacts for Tuvalu of a 1.5°C versus 2°C global warming target and explore sadness and discomfort surrounding discussion of these targets during COP 15. We highlight tensions between science and emotion, arguing that affective encounters can be significant in climate change decision-making. Weeping by a member of the Tuvalu delegation evoked discomfort in the conference plenary. This discomfort briefly unsettled the apparently stable boundaries of convention and protocol that seek to separate emotion from science and politics. We argue that possibilities for change arise when emotions enter climate change negotiations, even though (or perhaps because) these are arenas that privilege rational exchange. Our conclusion urges that more attention be paid to how climate science and emotion are intertwined in climate change politics.  相似文献   

Determination of heterogeneities in the hydraulic properties of a phreatic aquifer from tidal level fluctuations: a case in Argentina     

Eleonora S. Carol  Eduardo E. Kruse  Jorge L. Pousa  Alejandro R. Roig 《Hydrogeology Journal》2009,17(7):1727-1732

A well-known analytical solution of Jacob (1950) for groundwater flow due to tidal-wave propagation, together with field measurements along a complete tidal cycle and geological data, were used to evaluate the heterogeneities in the hydraulic properties of a phreatic aquifer located next to the River Ajo in the coastal plain environment of the southern sector of the Samborombon Bay wetland, Argentina. From the analysis of water-table fluctuations in a set of monitoring wells located along a riverbank-normal transect, it was possible to quantify the piecewise spatial variations of the hydraulic diffusivity of the phreatic aquifer. The results show the strong lateral variations of the sedimentary environment due to the influence of the different transport and deposition agents that characterize the coastal plain. The known thickness of the phreatic aquifer and the estimated range of the specific yield allowed the hydraulic conductivity to be identified as the most influential factor. [Jacob CE (1950) Flow of ground water. In: Rouse H (ed) Engineering Hydraulics. Wiley, New York]  相似文献