3838 resultaten

  • Aerobic nonylphenol degradation and nitro-nonyphenol formation by microbial cultures from sediments

    Auteurs: Weert, J.P.A. de; Rijnaarts, H.H.M.; Langenhoff, A.A.M. (2010)
    Gepubliceerd in: Applied microbiology and biotechnology, volume 86 (2010) nummer 2, pagina p. 761-771

  • Description of the long-term (1991-2005) temporal and spatial distribution of phytoplankton carbon biomass in the Dutch North Sea

    Auteurs: Baretta-Bekker, J.G.; Baretta, J.W.; Latuhihin, M.J.; Desmit, X.; Prins, T.C. (2009)

    Since the beginning of the 1990s phytoplankton species composition and abundance have been monitored at a high frequency (bi-weekly in the growing season and monthly in winter) at a number of fixed stations on the Dutch Continental Shelf, of which 18 are used in this study. Phytoplankton carbon biomass has been calculated from species-specific biovolume/cell data and summed over all species per functional group enumerated in the samples. The species are divided into four functional groups i.e. diatoms, flagellates, autotrophic and mixotrophic dinoflagellates and Phaeocystis spp. The total number of phytoplankton samples analysed up to and including 2005 is almost 4000. The annualmeanphytoplankton biomass over all stations remained stable at around 145mg C m−3. However, the phytoplankton composition has changed significantly, with increases in diatoms and dinoflagellates and compensating decreases in flagellates and Phaeocystis. With increasing distance from the shore, coinciding with a decrease in nutrient availability and increasingwater depth, total phytoplankton biomass as well as the biomass of diatoms, flagellates and Phaeocystis spp. decreased. This pattern was not true for the dinoflagellates, which occurred at more or less the same biomass throughout the region. Stations near river mouths and in the Wadden Sea outlets had much higher phytoplankton biomass than stations further from freshwater discharges. The data, split in two periods (1991–1998) and (1999–2005) and averaged over thewhole Dutch Continental Shelf, had been aggregated into seasonal biomass distributions. The seasonal phytoplankton biomass distribution was unimodal in both periods, with similar spring maxima of around 300 mg C m−3. The spring maximum occurred one month earlier, in April, in the second period. Phaeocystis over the whole study period remained the dominant near-shore species as it has been since the first phytoplankton observations at the end of the 19th century.

  • Wave overtopping and rubble mound stability under combined loading of waves and current

    Auteurs: Eslami Arab, S.; Gent, M.R.A. van (2010)

    This paper focusses on wave loading in combination with a strong current. The study is based on physical model tests in a wave-current basin. The results show to what extent wave overtopping and rubble mound stability are affected by wave loading in combination with a current. Wave overtopping and the damage to rock slopes generally reduce due to the presence of a current compared to the situation without a current.

  • Modelling of Singapore's coastal waters

    Auteurs: Xin, S.T.H.; Sisomphon, P.; Babovic, V. (2009)

    Being between the two large water bodies the Andaman Sea in the west and the South China Sea in the east, the Singapore Strait's hydrodynamics are highly complex. An accurate hydrodynamic model is essential for a complete understanding of the flow pattern in the area. Using the Delft3D modelling system, the so-called Singapore Regional Model was developed to simulate tidal and wind-driven flows for the whole water body.

  • Sea level anomalies from satellite altimetry : retrieval and validation

    Auteurs: Calkoen, C.J.; Wensink, H.; Twigt, D.J.; Sisomphon, P.; Mynett, A.E. (2009)

    This paper discusses techniques to extract tidal constants and sea level anomaly signatures from a variety of altimeter sensors, for a case study in a wide area around Singapore. As a next step, to determine how good (and useful) the results of these techniques are for subsequent data analysis and combination with models through data assimilation, validation studies were carried out on the consistency of the results of different altimeters and by comparing these with in-situ measurements.

  • On the dynamics of mud deposits in coastal areas

    Auteurs: Vinzon, S.B.; Calliari, L.J.; Holland, K.T.; Winterwerp, J.C. (2009)
    Gepubliceerd in: Continental shelf research, volume 29 (2009) nummer 3, pagina 501-502

    Introduction to the Proceedings of the International symposium on mud deposit in coastal areas (Porto Alegre, Brazil, 13-17 November 2006).

  • Effect of soil sample preservation, compared to the effect of other environmental variables, on bacterial and eukaryotic diversity

    Auteur: Tzeneva, V.A. (2009)
    Gepubliceerd in: Research in microbiology, volume 160 (2009) nummer 2, pagina 89-98

  • Determination of total nitrogen in atmospheric wet and dry deposition samples

    Auteurs: Karthikeyan, S.; Burger, D.F. (2009)
    Gepubliceerd in: Talanta : the international journal of pure and applied analytical chemistry, volume 77 (2009) nummer 3, pagina 979–984

    A microwave-assisted persulfate oxidation method followd by ion chromatogrhapic determination of nitrate was developed for total nitrogen determination in atmospheric wet and dry deposition samples. Various operating parameters such as oxidation reagent concentrations, microwave power, and extraction time were optimized to maximize the conversion of total nitrogen to nitrate for subsequent chemical analysis. Under optimized conditions, 0,012M K2S2O8 and 0,024M NaOH were found to be necessary for complete digestion of wet and dry deposition samples at 400W for 7min using microwave.

  • Role of perceptions and knowledge in the impact assessment for the extension of Mainport Rotterdam

    Auteurs: Hommes, S.; Mulder, J.P.M.; Otter, H.S. (2009)

    The Dutch government wants to expand Mainport Rotterdam, one of the largest ports in the world, by land reclamation in the NorthSea.This may affect the Wadden Sea, a unique wetlands area protected by the European Bird and Habitat Directives. To assess the impact of the port extension on the WaddenSea, an Appropriate Assessment procedure was carried out.We investigated how stakeholders’ perceptions were dealt with and how knowledge was used in this decision-making process. Our findings form an argument for practitioners in marine and coastal management to choose a process-oriented approach to deal withcomplex issues.

  • Impact of dredging and dumping on the stability of ebb-flood channel systems

    Auteurs: Wang, Z.B.; Winterwerp, J.C. (2001)

     The impact of dredging and dumping on the morphologic stability of the tidal channels is investigated using morphologic field observations for the Westerschelde estuary dating back to 1955. The results are used to verify the theoretical concept presented by Wang and Winterwerp (2001). This concept states that a critical threshold for the amount of sediment dumping exists above which a channel system in equilibrium may become unstable and degenerate.

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