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Registros recuperados: 26
Primeira ... 12 ... Última
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A room temperature procedure for the manual determination of urea in seawater OMA
Goeyens, L.; Kindermans, N.; Yusuf, M.A.; Elskens, M..
Several earlier studies underpin the important role of dissolved organic matter and more particularly urea in phytoplanktonic nitrogen uptake fluxes. Generally, the determination of urea concentrations relies on the formation of an imidazolone-thiosemicarbizide complex, a complexation which requires very accurate temperature control when carried out at high temperature. It is also possible, however, to obtain reliable results with a room temperature procedure. The measured abundances for both complexation at high temperature (85 degree C, 20 min) and at ambient temperature (22 degree C, 72 h) are closely comparable. Lower values are observed for temperatures <10 degree C though. Moreover, a comparison of both techniques reveals similar precision...
Tipo: Info:eu-repo/semantics/article Palavras-chave: Dissolved organic carbon; Sea water; Temperature; Urea; Water analysis.
Ano: 1998 URL: http://www.vliz.be/nl/open-marien-archief?module=ref&refid=7858
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Accumulation of suspended barite at mesopelagic depths and export production in the Southern Ocean OMA
Dehairs, F.A.; Baeyens, W.F.J.; Goeyens, L..
Tipo: Info:eu-repo/semantics/article
Ano: 1992 URL: http://www.vliz.be/nl/open-marien-archief?module=ref&refid=10162
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Ammonium regeneration in the Scotia-Weddell Confluence area during spring 1988 OMA
Goeyens, L.; Tréguer, P.; Lancelot, C.; Mathot, S.; Becquevort, S.; Morvan, J.; Dehairs, F.A.; Baeyens, W.F.J..
Tipo: Info:eu-repo/semantics/article
Ano: 1991 URL: http://www.vliz.be/imisdocs/publications/279128.pdf
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An automated method for the assessment of mercury adsorption rates on particulate suspended matter OMA
Baeyens, W.F.J.; Decadt, G.; Dehairs, F.A.; Goeyens, L..
A continuous filtration system connected to a mercury auto-analyzer has been constructed for obtaining mercury adsorption rates on particulate suspended matter. The capabilities of this device have been demonstrated by carrying out a series of experiments under controlled physicochemical parameter conditions on samples of the Scheldt estuary. Duplicate measurements showed coefficients of variation ranging from 1 to 6 %. Depending on the physico-chemical conditions, the initial adsorption rate per unit of dissolved mercury concentration varied between 1.2 and 8.1 x 10<sup>-2</sup> mn<sup>-1</sup>.
Tipo: Info:eu-repo/semantics/article Palavras-chave: Adsorption; Mercury; Methodology; Particulates; Suspended matter.
Ano: 1982 URL: http://www.vliz.be/nl/open-marien-archief?module=ref&refid=3413
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An experiment on the relative importance of denitrification, nitrate reduction and ammonification in coastal marine sediment OMA
Goeyens, L.; De Vries, R.T.P.; Bakker, J.F.; Helder, W..
Simultaneous determinations of <sup>15</sup>N-nitrogen gas production, <sup>15</sup>N-ammonia formation by nitrate reduction and ammonia production from organic nitrogen were carried out after addition of <sup>15</sup>N-nitrate to anaerobically incubated sediment slurries from a location in the Dutch Wadden Sea. The rate of nitrogen gas production was 1.75 µmol N.cm<sup>-3</sup> wet sediment.d<sup>-1</sup>, nitrate reduction to ammonia occurred to a rate of 0.79 µmol N.cm <sup>-3</sup>.d <sup>-1</sup> and ammonification at 1.17 µmol N-cm <sup>-3</sup>.d <sup>-1</sup>. At the end of the incubation experiment (after 30 h) 63% of the originally added...
Tipo: Info:eu-repo/semantics/article Palavras-chave: Ammonia; Biogeochemical cycle; Coastal zone; Denitrification; Nitrates; Nitrogen cycle; Sediments.
Ano: 1987 URL: http://www.vliz.be/nl/open-marien-archief?module=ref&refid=3169
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Barite formation in the Southern Ocean water column OMA
Stroobants, N.; Dehairs, F.A.; Goeyens, L.; Vanderheijden, N.; Van Grieken, R..
The intensity of past biological activity can be correlated with the occurrence of suspended and sedimented barite (BaSO<sub>4</sub>). To date, there is a lack of information on the processes controlling the production of pelagic barite. During the EPOS-2 cruise (November-December 1988), situated in the Scotia Sea-Weddell Sea Confluence, suspended water samples were taken for analysis of total Ba by inductively coupled plasma-atomic emission spectroscopy (ICP-AES) and for scanning electron microscopy-electron microprobe (SEM-EMP).The vertical profiles of particulate barium generally show a Ba maximum between 200 and 500 m. SEM-EMP investigation on Scotia-Weddell Sea Confluence profiles provide a possible explanation for the origin of this...
Tipo: Info:eu-repo/semantics/article Palavras-chave: Artemia.
Ano: 1992 URL: http://www.vliz.be/nl/open-marien-archief?module=ref&refid=2865
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Biogeochemical behaviour of Cd, Cu, Pb and Zn in the Scheldt estuary during the period 1981-1983 OMA
Baeyens, W.F.J.; Elskens, M.; Gillain, G.; Goeyens, L..
Cu, Zn, Cd and Pb have been analysed in suspended matter and water samples from the Scheldt estuary, collected during five cruises between May 1982 and May 1983. In order to evaluate the overall metal behaviour in the estuary, continuous longitudinal profiles of the total, the particulate and the dissolved metal concentrations are discussed in relation to various specific physico-chemical parameters. By means of correlation and multi-regression techniques, several estuarine processes could be identified which dominate and/or control the behaviour of the individual trace metals in three distinct areas of the Scheldt estuary. The behaviour of the four selected metals was found to show some common features, but is besides this also characterised by many...
Tipo: Info:eu-repo/semantics/article
Ano: 1998 URL: http://www.vliz.be/nl/open-marien-archief?module=ref&refid=7043
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Determination of methylmercury in biological samples by semiautomated headspace analysis OMA
Decadt, G.; Baeyens, W.F.J.; Bradley, D.; Goeyens, L..
Gas-liquid distribution coefficients of methylmercury halides dissolved in water or benzene have been assessed by using a headspace injection system coupled to a gas chromatograph-microwave-induced plasma system. Vapor concentrations decreased in the following order: CH<sub>3</sub>HgI > CH<sub>3</sub>HgBr > CH<sub>3</sub>HgCl. To transform all methylmercury iodide, iodoacetic acid (IAc) is used as the liberating agent. Methylmercury iodide degradation is prevented by the addition of sodium thiosulfate (0.05 M). The results obtained with internal standard addition are not influenced by other volatile compounds including other mercury compounds. The method has been applied to a series of biological samples. The...
Tipo: Info:eu-repo/semantics/article Palavras-chave: Analytical techniques; Chemical analysis; Mercury compounds.
Ano: 1985 URL: http://www.vliz.be/nl/open-marien-archief?module=ref&refid=3198
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Distribution, transport and fate of Bi, Cu, Cd, Hg, Pb, Sb and Zn in the Belgian coastal marine environment. Part II: Spatial, temporal and compartmental distribution in the water column OMA
Decadt, G.; Gillain, G.; Dehairs, F.A.; Dedeurwaerder, H.; Goeyens, L.; Baeyens, J..
Tipo: Info:eu-repo/semantics/article
Ano: 1984 URL: http://www.vliz.be/imisdocs/publications/268322.pdf
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Distribution, transport and fate of Bi, Cu, Cd, Hg, Pb, Sb and Zn in the Belgian coastal marine environment. Part V: Interaction kinetics between dissolved inorganic mercury and estuarine suspended matter OMA
Baeyens, W.F.J.; Decadt, G.; Dehairs, F.A.; Goeyens, L.; Dedeurwaerder, H.; Gillain, G..
Tipo: Info:eu-repo/semantics/article
Ano: 1982 URL: http://www.vliz.be/imisdocs/publications/286410.pdf
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d<sup>13</sup>C of Southern Ocean suspended organic matter during spring and early summer: Regional and temporal variability OMA
Dehairs, F.A.; Kopczynska, E.; Nielsen, C.; Lancelot, C.; Bakker, D.; Koeve, W.; Goeyens, L..
Observations are presented for stable carbon isotope abundance (&#x3b4;<sup>13</sup>C) and organic carbon and nitrogen content of suspended organic matter from the Southern Ocean (Circumpolar Current and Polar Front) during spring and early summer. The Polar Front Zone was characterized by elevated plankton biomasses and phytoplankton activity, which also increased significantly over the one-month investigation period. From the beginning of the phytoplankton bloom &#x3b4;<sup>13</sup>C values of suspended organic matter in the Polar Front were high, exceeding values predicted from the relationship with CO<sub>2(aq)</sub> concentration observed in other areas of the Southern Ocean. Later in the season...
Tipo: Info:eu-repo/semantics/article
Ano: 1997 URL: http://www.vliz.be/nl/open-marien-archief?module=ref&refid=10202
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Dynamic patterns of dissolved nitrogen in the Southern Bight of the North Sea OMA
Baeyens, W.F.J.; Mommaerts, J.-P.; Goeyens, L.; Dehairs, F.A.; Dedeurwaerder, H.; Decadt, G..
Spatial and temporal variations of dissolved inorganic nitrogen (DIN) have been assessed in onshore and offshore areas of the Southern Bight on the basis of several years' measurements. They indicate that both the residual flow lines and DIN isoconcentration lines run parallel with the coast except in the vicinity of important freshwater discharge points such as the Scheldt estuary. Evidence was found that the seasonal DIN oscillations are not created through fluctuations in input conditions at the lateral boundaries, despite considerable fluctuations in these inputs which include the English Channel (from 500 tons(t) N day<sup>-1</sup> in June up to approximately 2000 t N day<sup>-1</sup> in February) and also rivers such as the...
Tipo: Info:eu-repo/semantics/article Palavras-chave: Dissolved organic nitrogen ANE; North Sea; Southern Bight.
Ano: 1984 URL: http://www.vliz.be/nl/open-marien-archief?module=ref&refid=3310
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Effect of organic complexation on the behaviour of dissolved Cd, Cu and Zn in the Scheldt estuary OMA
Baeyens, W.F.J.; Goeyens, L.; Monteny, F.; Elskens, I..
Samples from the Scheldt estuary have been assayed for dissolved Cd, Cu and Zn using differential pulse anodic stripping voltammetry, either as total (after UV irradiation) or labile concentrations. Under these experimental conditions, labile concentrations ranged between 51-65% of total Cu, 16-66% of total Zn and 53-91 % of total Cd. The metal-organic interactions were assessed by evaluating (a) the distribution coefficient K<sub>d</sub> for the distribution of the metals between the liquid phase (complexation) and their binding to particulate matter, and (b) the competitive effect exerted by inorganic complexing ligands using a multi-element interaction model. The proportion of organically bound metals (strong and labile) was estimated, in...
Tipo: Info:eu-repo/semantics/article
Ano: 1998 URL: http://www.vliz.be/nl/open-marien-archief?module=ref&refid=7051
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General description of the Scheldt estuary OMA
Baeyens, W.F.J.; Van Eck, B.T.M.; Lambert, C.; Wollast, R.; Goeyens, L..
A general description of the Scheldt estuary, including the hydrology, the sediment transport, the productivity and the biodegradation with respect to their influence on the trace metal behaviour in the Scheldt estuary, is given. The river basin can be divided in several sections according to their morphological, hydrodynamical and sedimentary properties. The zone from km 78 to 55, which corresponds roughly with the salinity zone from 2 to 10 psu, is the zone of high turbidity, high sedimentation and of oxygen depletion, especially in the summer period. That area is called the geochemical filter because the solid/dissolved distribution of the trace metals is controlled by redox, adsorption/desorption, complexation and precipitation/coprecipitation...
Tipo: Info:eu-repo/semantics/article Palavras-chave: ANE; Netherlands; Westerschelde.
Ano: 1998 URL: http://www.vliz.be/nl/open-marien-archief?module=ref&refid=7040
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Improved estimation of f-ratio in natural phytoplankton assemblages OMA
Elskens, M.; Goeyens, L.; Dehairs, F.A.; Rees, A.; Joint, I.; Baeyens, J..
Statistical properties in non-linear regression models of <i>f</i>-ratio versus nitrate relationships were investigated using a case study conducted at the European continental margin (Project OMEX). Although the OMEX data fit within the family of empirical models introduced by Platt and Harrison (1985) Nature 318, 55&#x2013;58), it is shown that the discrepancy between experimental and fitted values is larger than expected, assuming that the data are accurate. Since the ambient ammonium concentration plays a leading role in regulating new production, the present analysis was extended to include explicitly the effect of ammonium on <i>f</i>-ratio versus nitrate plots. Experimental results based on controlled ammonium additions...
Tipo: Info:eu-repo/semantics/article
Ano: 1999 URL: http://www.vliz.be/nl/open-marien-archief?module=ref&refid=10269
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Nitrogen cycles in a coastal open sea zone off the Belgian coast OMA
Baeyens, J.; Goeyens, L.; Dehairs, F.A.; Decadt, G.; Mommaerts, J.-P..
Tipo: Info:eu-repo/semantics/article Palavras-chave: Coastal waters Nitrogen cycle ANE; Belgium; Belgian Coast.
Ano: 1983 URL: http://www.vliz.be/nl/open-marien-archief?module=ref&refid=10068
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Nitrogen uptake regime and phytoplankton community structure in the Atlantic and Indian sectors of the Southern Ocean OMA
Semeneh, M.; Dehairs, F.A.; Elskens, M.; Baumann, M.E.M.; Kopczynska, E.E.; Lancelot, C.; Goeyens, L..
Phytoplankton nitrogen uptake is studied in relation to the biomass and structure of phytoplankton community in the Atlantic and Indian sectors of the Southern Ocean. Two scenarios of seasonal evolution of uptake regime and phytoplankton community structure are described. The first scenario includes the Marginal Ice Zone areas of the Weddell Sea and adjacent areas where a predominantly nitrate based, diatom dominated assemblage, thriving in a stable water column at the beginning of the season was transformed into a mainly ammonium based, flagellate dominated assemblage, towards the end of the season. The change in phytoplankton community structure was caused by selective grazing by large grazers and reduced stability of the water column and the shift in...
Tipo: Info:eu-repo/semantics/article Palavras-chave: Biogeochemical cycle Biomass Community composition Continental shelves Ice edge Nitrogen Pelagic environment Phytoplankton Size distribution Uptake PS; Southern Ocean PSE; Antarctic Ocean.
Ano: 1998 URL: http://www.vliz.be/nl/open-marien-archief?module=ref&refid=10255
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On suspended barite and the oxygen minimum in the Southern Ocean OMA
Dehairs, F.A.; Goeyens, L.; Stroobants, N.; Bernard, P.; Goyet, C.; Poisson, A.; Chesselet, R..
Particulate Ba profiles were measured in the Indian sector of the southern ocean. The largest fraction (>80%) of this barium is present as barite microcrystals. The profiles of total barium are characterized by a subsurface maximum between 200 and 500 m depth in the vicinity of the oxygen minimum. Highest barium values are found just south of the Polar Front, while lowest values occur close to the Antarctic Divergence. Between the divergence and the Polar front a tight inverse relationship is observed between oxygen in the oxygen minimum and barium in the barium maximum. This relationship disappears north of the Polar Front. Since suspended barite is known to be of biological origin, the correlation of barite with oxygen suggests that the observed...
Tipo: Info:eu-repo/semantics/article Palavras-chave: Barite Oxygen PS; Southern Ocean.
Ano: 1990 URL: http://www.vliz.be/nl/open-marien-archief?module=ref&refid=3076
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Oxidation rate of organic carbon in the mesopelagic water column as traced by suspended barium-barite OMA
Dehairs, F.A.; Goeyens, L..
Tipo: Info:eu-repo/semantics/article
Ano: 1996 URL: http://www.vliz.be/nl/open-marien-archief?module=ref&refid=7108
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Particulate barium stocks and oxygen consumption in the Southern Ocean mesopelagic water column during spring and early summer OMA
Dehairs, F.A.; Shopova, D.; Ober, S.; Veth, C.; Goeyens, L..
Particulate barium was analysed in the upper 600 m of the Southern Ocean water column during repeated transects along the 6 degree W meridian in October-November 1992. The transects extended between the northern edge of the Weddell Gyre (57 degree 30'S) in the south to 47 degree S within the Polar Front Zone (PFZ) in the north. From earlier studies, it is known that the largest fraction of Ba in oceanic suspended matter occurs as barite micro-crystals. In the PFZ, an increase in the particulate Ba content in surface waters and at mesopelagic depths can be significant over the investigation period (1 month) and follows the increase of primary production during bloom development. Using an inverse one-dimensional advection-diffusion-consumption model,...
Tipo: Info:eu-repo/semantics/article Palavras-chave: Barium Biogeochemical cycle Carbon cycle Mixed layer Oxygen consumption Primary production PSW; Antarctic Ocean.
Ano: 1997 URL: http://www.vliz.be/nl/open-marien-archief?module=ref&refid=10209
Registros recuperados: 26
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