Identification of chlorite and chlorite-related minerals in sediments     

H. W. van der Marel 《Contributions to Mineralogy and Petrology》1964,9(5):462-480

A scheme is presented for the identification and classification of chlorite and related minerals in sediments which is mainly based on X-ray characteristics of the orginal sample and the sample heated at 350°C and treated with K⁺ and with glycerol. Examples are given. It is emphasized that additional data about clay mineral genesis, electron microscopy, infrared spectroscopy and chemical analyses are needed for the ordening of a certain mineral in the proposed scheme. Many names of minerals so far found to occur in the clay separate of sediments proved to be synonymous (52 of a total of 88) and thus should be abandoned. They only give confusion and needlessly increase the many difficulties which already exist in the identification, classification and quantitative determination of this complicated group of minerals of about 36 well defined specimens which may be found in sediments.  相似文献   

An optimized method for automated analysis of algal pigments by HPLC   总被引：3，自引：0，他引：3  

M.A. van Leeuwe  L.A. Villerius  J. Roggeveld  R.J.W. Visser  J. Stefels 《Marine Chemistry》2006,102(3-4):267-275

A recent development in algal pigment analysis by high-performance liquid chromatography (HPLC) is the application of automation. An optimization of a complete sampling and analysis protocol applied specifically in automation has not yet been performed. In this paper we show that automation can only be successful if the various methodological aspects of the sampling and analysis protocol are considered in coherence. We introduce an optimized protocol that involves freeze-drying of the sample, subsequent extraction in 90% acetone and the application of water-packing during analysis. The method was evaluated on both natural plankton populations and a broad spectrum of microalgal cultures: Thalassiosira weisflogii (Bacillariophyceae), Emiliania huxleyi (Prymnesiophyceae), Phaeocystis globosa and Phaeocystis antarctica (Prymnesiophyceae) and Pyramimonas sp. (Prasinophyceae). Whereas pigment extracts were unstable in methanol, with recorded chlorophyll a losses from 10% to 60% per day, pigment degradation rates in acetone were generally less than 1% over 18 h storage in the autosampler (4 °C). In addition, it was found that the extraction efficiency of acetone significantly increased upon freeze-drying prior to extraction. Increases as high as 50–60% were measured in P. antarctica. The application of water-packing of the sample during injection resulted in improved peak shape and peak separation, without diluting the pigment concentrations. Automation is especially beneficial for application in the field, when mixed algal assemblages and low biomass put a high demand on the sensitivity as well as reproducibility of the method.  相似文献   

A quantitative evaluation of the impact of beam trawling on benthic fauna in the southern North Sea     

Piet  G. J.; Rijnsdorp  A. D.; Bergman  M. J. N.; van Santbrink  J. W.; Craeymeersch  J.; Buijs  J. 《ICES Journal of Marine Science》2000,57(5):1332-1339

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A new method for the generation of second-order random waves     

Peter Jan van Leeuwen  Gert Klopman 《Ocean Engineering》1996,23(2):167-192

In order to prevent the generation of spurious free sub- and superharmonics of random waves in a laboratory channel, the control signal for the wave board has to be derived according to a higher-order wave theory. An expression for this control signal has been derived with the perturbation method of multiple scales. It is much less complex and requires less computation time than the expressions obtained from the full second-order theory. The new method for second-order subharmonics was verified experimentally for waves with bichromatic and continuous first-order spectra. The data were analysed with the complex-harmonic principal-component analysis to reduce the influence of noise.  相似文献   

Measurement of the redox speciation of iron in seawater by catalytic cathodic stripping voltammetry     

Martha Gledhill  Constant M. G. van den Berg 《Marine Chemistry》1995,50(1-4)

Catalytic cathodic stripping voltammetry (CSV) preceded by adsorptive collection of complexes of 1-nitroso-2-napthol (NN) can be used to determine iron in seawater. It is shown here that iron(II) is effectively masked in the presence of 2,2-dipyridyl (Dp) so that iron(III) is measured selectively. The concentration of iron(II) is then calculated as the difference between the concentrations of reactive iron (Fe_R) in the absence and presence of 2 μM Dp, Fe_R being defined as that which was complexed by 20 μM NN at pH 6.9 in the presence of 1.8 mM H₂O₂ and 5 ppm sodium dodecyl sulphate. A 30 min reaction time was allowed for Dp to react with iron(II) in seawater prior to the determination of reactive iron(III) using the same conditions as used for Fe_R. Detection limits of 0.08 nM, 0.077 nM and 0.12 nM were obtained for Fe_R, iron(III) and iron(II), respectively, using a 60 s deposition time.The method was utilised to determine the redox speciation of iron in the northern North Sea. Concentrations of Fe_R ranged between 0.8 and 3.5 nM with nutrient-like depth profiles. Iron(II) was found to be present at concentrations up to 1.2 nM, the highest concentrations occurring in the upper 20 m of the water column.  相似文献   

Risk of dike failure due to flow slides     

M. B. de Groot  H. den Adel  T. P. Stoutjesdijk  C. J. van Westenbrugge 《Coastal Engineering》1995,26(3-4)

Flow slides may affect the stability of dikes. A flow slide is an instability of a submerged slope caused by liquefaction of loose, (medium) fine sand. Whether a flow slide will occur depends on the properties of the sand, which are a function of its density, and the geometry of the slope, as determined by wave and current induced scour and sedimentation. The influence of sand properties and the geometry parameters on the risk of flow slides are discussed. The application of a flow slide prediction method to an example and a risk analysis is briefly discussed.  相似文献   

Transient biouptake flux and accumulation by microorganisms: The case of two types of sites with Langmuir adsorption     

Josep Galceran  Josep Monn  Jaume Puy  Herman P. van Leeuwen 《Marine Chemistry》2006,99(1-4):162

The uptake of a chemical species by an aquatic microorganism is modelled considering two kinds of sites where Langmuirian adsorption is followed by first order internalisation kinetics. Simpler models, such as only one internalisation route (while most of the adsorption takes place on non-internalising sites) or a linear isotherm for adsorption on one or both sites, become limiting cases of this double-Langmuirian model. The model considers the sites located on the spherical (or semi-spherical) surface of the organism, and takes diffusion from the medium into explicit account. The numerical solution for the internalisation flux shows a maximum. We provide an estimate for the time needed to reach a certain proximity to steady state. The transient solution confirms that the analytical expressions for the steady-state flux are usually valid and that the accumulated amounts reflect the impact of the short-time uptake. The Instantaneous Steady-State Approximation (ISSA), where an intercept of the linear regression of accumulated amount as a function of time is interpreted as an adsorbed amount, can be critically assessed with the transient numerical code for two cases: (i) when the total burden of metal on the cell is the input data and (ii) when an extraction procedure provides further information on the adsorbed and internalised amount.  相似文献   

The expression of CYP1A,vitellogenin and zona radiata proteins in Atlantic salmon (Salmo salar) after oral dosing with two commercial PBDE flame retardant mixtures: absence of short-term responses     

Boon JP  van Zanden JJ  Lewis WE  Zegers BN  Goksøyr A  Arukwe A 《Marine environmental research》2002,54(3-5):719-724

The short-term effects of the commercial PBDE flame retardant mixtures Penta-BDE and cta-BDE on the expression of cytochrome P450 1A (CYP1A), vitellogenin (Vtg) and zona radiata proteins (Zrp) were investigated in juvenile salmon (Salmo salar). For this purpose, groups of fish were dosed twice (oral intake at days I and 4) with 10 and 50 mg/kg body weight of both commercial mixtures. The fishes were sacrificed at day 7 (n = 5 for each group) and 14 (n = 6 for each group), and blood, liver, fillet, and brain were collected. Blanks and positive controls were also part of the experiment. The expressions of Vtg, Zrp, and CYPIA were measured with several techniques (EROD, ELISA, Western, Northern and Slot Blot). The values in the groups of fish treated with Penta-BDE or Octa-BDE did not significantly differ from the reference group for any of the parameters tested. In contrast, the positive control groups treated with estradiol-17beta for Vtg and Zrp expression, and beta-naphthoflavone for CYP1A expression did show a significant response, indicating the potential sensitivity of the fishes for the parameters measured. Since the results of the chemical analyses showed concentrations of a number of PBDE congeners in liver, fillet, and brain that were about three orders of magnitude above those of fish from the North Sea, it is concluded that the short-term toxicity of both commercial PBDE mixtures for these endpoints was low.  相似文献   

The morphodynamic modelling of tidal sand waves on the shoreface     

P.K. Tonnon  L.C. van Rijn  D.J.R. Walstra 《Coastal Engineering》2007

An artificial sand wave on the Dutch shoreface of the North Sea has been studied in conditions with relatively strong tidal currents in the range of 0.5 to 1 m/s and sediments in the medium sand size range of 0.2 to 0.5 mm. The sand wave is perpendicular to the tidal current and has a maximum height and length of the order of 5 m and 1 km, respectively. The sand wave is dynamically active and shows migration rates of the order of a few metres per year. A numerical morphodynamic model (DELFT3D model) has been used to simulate the morphological behaviour of the sand wave in the North Sea. This model approach is based on the numerical solution of the three-dimensional shallow water equations in combination with a surface wave propagation model (wind waves) and the advection–diffusion equation for the sediment particles with online bed updating after each time step. The model results show that the sand wave grows in the case of dominant bed-load transport (weak tidal currents; relatively coarse sediment; small roughness height; low waves) and that the sand wave decays in the case of dominant suspended transport (strong currents, relatively fine sediment, large roughness height; storm waves).  相似文献   

Spatial variation in abundance and catch composition of Cancer pagurus in Norwegian waters: biological reasoning and implications for assessment     

Woll  Astrid K.; van der Meeren  Gro I.; Fossen  Inge 《ICES Journal of Marine Science》2006,63(3):421-433

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