Organotin accumulation in an estuarine food chain: comparing field measurements with model estimations     

Veltman K  Huijbregts MA  van den Heuvel-Greve MJ  Vethaak AD  Hendriks AJ 《Marine environmental research》2006,61(5):511-530

The bioaccumulation model OMEGA (optimal modelling for ecotoxicological applications) is used to explore accumulation of organotins in the Western Scheldt food chain, consisting of herbi-detritivores, primary and secondary carnivorous fish and a piscivorous bird. Organotins studied are tributyltin (TBT) and triphenyltin (TPT) and the respective di- and mono-organotin metabolites. Empirical elimination rate constants are compared to model predictions for organic substances and metals. It is found that field bioaccumulation ratios are higher than predicted based on elimination kinetics relevant for organic compounds. The results indicate that uptake of organotins mainly occurs via hydrophobic mechanisms, whereas elimination may occur via metal-like kinetics. This results in very low elimination rates, which are comparable to model predictions for metals.  相似文献   

Extreme storm surge modelling in the North Sea     

Nina Ridder  Hylke de Vries  Sybren Drijfhout  Henk van den Brink  Erik van Meijgaard  Hans de Vries 《Ocean Dynamics》2018,68(2):255-272

This study shows that storm surge model performance in the North Sea is mostly unaffected by the application of temporal variations of surface drag due to changes in sea state provided the choice of a suitable constant Charnock parameter in the sea-state-independent case. Including essential meteorological features on smaller scales and minimising interpolation errors by increasing forcing data resolution are shown to be more important for the improvement of model performance particularly at the high tail of the probability distribution. This is found in a modelling study using WAQUA/DCSMv5 by evaluating the influence of a realistic air-sea momentum transfer parameterization and comparing it to the influence of changes in the spatial and temporal resolution of the applied forcing fields in an effort to support the improvement of impact and climate analysis studies. Particular attention is given to the representation of extreme water levels over the past decades based on the example of the Netherlands. For this, WAQUA/DCSMv5 is forced with ERA-Interim reanalysis data. Model results are obtained from a set of different forcing fields, which either (i) include a wave-state-dependent Charnock parameter or (ii) apply a constant Charnock parameter (α _{C h} =?0.032) tuned for young sea states in the North Sea, but differ in their spatial and/or temporal resolution. Increasing forcing field resolution from roughly 79 to 12 km through dynamically downscaling can reduce the modelled low bias, depending on coastal station, by up to 0.25 m for the modelled extreme water levels with a 1-year return period and between 0.1 m and 0.5 m for extreme surge heights.  相似文献   

High-resolution optical dating of Late Holocene storm surge deposits – a showcase from Schokland (Noordoostpolder,the Netherlands)     

D.F.A.M. van den Biggelaar  J. Wallinga  R.T. van Balen  C. Kasse  S. Troelstra  S.J. Kluiving 《地球表面变化过程与地形》2019,44(4):886-899

Storm surges have a major impact on land use and human habitation in coastal regions. Our knowledge of this impact can be improved by correlating long-term historical storm records with sedimentary evidence of storm surges, but so far few studies have applied such an approach. Here we apply, for the first time, state-of-the-art optically stimulating luminescence (OSL) methods to obtain high-resolution age information on a sequence of Late Holocene storm surge deposits. By combining this chronological framework of storm surges with other reconstruction methods, we investigate the storm surge impact on the former island Schokland, located in a former inlet of the North Sea (central Netherlands).During the Late Holocene, Schokland transformed from a peat area that gradually inundated (~800 CE) via an island in a marginal marine environment (~1600 CE) to a land-locked island in the reclaimed Province of Flevoland (1942 CE). These transitions are recorded in the sediment archive of the island, consisting of silty clay with sandy intervals deposited during storm surges. A series of ten quartz OSL ages, obtained using best-practice methods to deal with incomplete resetting of the OSL signal and dose rate heterogeneity, reveal two periods of storm surge deposition, around 1600 CE and between 1742 and 1822 CE. Historical sources indicate that major storm surges hit Schokland during these periods. Laboratory analyses (thermogravimetry, grain-size, foraminifera, bivalves and ostracods) corroborates the existence of the two sets of storm surge deposits within the clay sequence. Our study sets a benchmark for obtaining robust depositional age constraints from storm surge sediments, and demonstrates the great potential of modern OSL methods to contribute to improved assessment of storm surge risk. © 2018 John Wiley & Sons, Ltd.  相似文献   

Efficient Representation of Laguerre Mosaics with an Application to Microstructure Simulation of Complex Ore     

Menzel  Peter  Teichmann  Jakob  van den Boogaart  Karl Gerald 《Mathematical Geosciences》2020,52(6):731-757

Mathematical Geosciences - Laguerre mosaics have been an important modeling approach in astronomy, physics, crystallography, geology and mathematics for several decades. In materials science, they...  相似文献   

Benthic fluxes of copper,complexing ligands and thiol compounds in shallow lagoon waters     

Conrad S. Chapman  Gabriele Capodaglio  Clara Turetta  Constant M.G. van den Berg 《Marine environmental research》2009,67(1):17-24

Benthic fluxes of copper, copper complexing ligands and thiol compounds in the shallow waters of Venice Lagoon (Italy) were determined using benthic chambers and compared to porewater concentrations to confirm their origin. Benthic copper fluxes were small due to small concentration differences between the porewaters and the overlying water, and the equilibrium concentration was the same at both sites, suggesting that the sediments acted to buffer the copper concentration. Thiol fluxes were ～10 × greater at 50–60 pmol cm^?2 h^?1, at the two sites. Porewater measurements demonstrated that the sediments were an important source of the thiols to the overlying waters. The overlying waters were found to contain at least two ligands, a strong one, L1 (log K′_CuL1 = 14.2) and a weaker one, L2 (log K′_CuL2 = 12.5). The concentration of L1 remained relatively constant during the incubation and similar to that of copper, whereas that of L2 was in great excess of copper, its concentration balanced by porewater releases and breakdown, probably due to uptake by microorganisms, similar to that of the thiol compounds. Similarity of the thiol and L2 concentrations and similar complex stability with copper suggest that L2 was dominated by the thiols. The free copper concentration ([Cu´]) in the Lagoon waters was lowered by a factor of 10⁵ as a result of the organic complexation.  相似文献   

Sediment segregation by biodiffusing bivalves   总被引：1，自引：0，他引：1  

F. Montserrat  C. Van Colen  P. Provoost  M. Milla  M. Ponti  K. Van den Meersche  T. Ysebaert  P.M.J. Herman 《Estuarine, Coastal and Shelf Science》2009,83(4):379-391

The selective processing of sediment fractions (sand and mud; >63 μm and ≤63 μm median grain size) by macrofauna was assessed using two size classes of inert, UV-fluorescent sediment fraction tracers (luminophores). The luminophores were applied to the sediment surface in 16 m² replicated plots, defaunated and control, and left to be reworked by infauna for 32 days. As the macrofaunal assemblage in the ambient sediment and the control plots was dominated by the common cockle Cerastoderma edule, this species was used in an additional mesocosm experiment. The diversity, abundance and biomass of the defaunated macrobenthic assemblage did not return to control values within the experimental period. Both erosion threshold and bed elevation increased in the defaunated plots as a response to the absence of macrofauna and an increase in microphytobenthos growth. In the absence of macrobenthos, we observed an accretion of 7 mm sediment, containing ca. 60% mud. Image analysis of the vertical distribution of the different luminophore size classes showed that the cockles preferentially mobilised fine material from the sediment, thereby rendering it less muddy and effectively increasing the sand:mud ratio. Luminophore profiles and budgets of the mesocosm experiment under “no waves–no current” conditions support the field data very well.  相似文献   

Long-term influence of maritime access works on the distribution of cohesive sediments: analysis of historical and recent data from the Belgian nearshore area (southern North Sea)     

Michael Fettweis  Jean-Sébastien Houziaux  Isabelle Du Four  Vera Van Lancker  Cecile Baeteman  Mieke Mathys  Dries Van den Eynde  Frederic Francken  Stanislas Wartel 《Geo-Marine Letters》2009,29(5):321-330

  相似文献   

Evidence for organic complexation of iron in seawater   总被引：1，自引：0，他引：1  

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

Iron occurs at very low concentrations in seawater of oceanic origin and its low abundance is thought to limit primary production in offshore waters (Martin and Fitzwater, 1988). A new electrochemical method, cathodic stripping voltammetry (CSV), is used here to determine the speciation of iron in seawater originating from the Western Mediterranean taking advantage of ligand competition of an added electroactive ligand with the natural organic complexing matter to evaluate whether iron is organically complexed. The measurements indicate that iron occurs 99% (or 99.9% depending on which value is selected for α_Fe′) complexed by organic complexing ligands throughout the water column of the Western Mediterranean and by analogy probably also in other oceanic waters. The composition of the organic complexing ligands is as yet unknown, but the data indicate a major source from microorganisms (bacteria or phytoplankton) in and immediately below the fluorescence maximum in the upper water column. The organic complexes are apparently reversible releasing iron when the competing ligand is added and binding more iron when its concentration is increased. The organic complexing ligands occur at concentrations well above those of iron ensuring full complexation of this biologically essential element, and buffer the free iron concentration at a very low level against fluctuations as a result of removal by primary producers or inputs from atmospheric sources. The new data indicate that a re-evaluation of the concept of the bioavailable fraction of iron is required.  相似文献   

Experiments on the resuspension of estuarine sediments containing benthic diatoms     

V. N. de Jonge  J. van den Bergs 《Estuarine, Coastal and Shelf Science》1987,24(6)

A laboratory system was used to test the effect of water flow on the resuspension of mud and sand sediments and, specifically, benthic diatoms from the Ems estuary, The Netherlands. Current velocities generated by two rotating cylinders in a cylindrical tank were determined by a small float and a laser Doppler velocimeter. At low angular velocities, the amount of suspended matter increased linearly with angular velocity and the float current velocity. However, at higher angular velocities, the increase in current velocity was less because of the strong turbulence: concomitantly, the current velocity boundary layer (δ) became thinner and the suspended matter concentration increased rapidly. The dominant diatom species from the sandy sediment were suspended in two distinct groups, one of which consisted of the species Navicula aequorea, Navicula salinicola, Ophephora martyi and Opephora pacifica, and was more exclusively bound to sand grains than the other. The benthic diatom species inhabiting the silty sediment did not show this difference. The most important shortcoming in the experiments was the inability to determine the radial and vertical velocity components. This precluded reliable calculations of the shear stress. The data presented emphasize the importance of finding a method to determine the shear stress under experiments and field conditions so that direct comparisons can be made. Despite this it is assumed that, just as under the experimental conditions discussed, under natural conditions in shallow waters resuspension starts at current velocities as low as ca. 10 cm s⁻¹.  相似文献   

On the assembly history of dark matter haloes     

Yun Li  H. J. Mo  Frank C. van den Bosch  W. P. Lin 《Monthly notices of the Royal Astronomical Society》2007,379(2):689-701

We study the mass assembly history (MAH) of dark matter haloes. We compare MAHs obtained using (i) merger trees constructed with the extended Press–Schechter (EPS) formalism, (ii) numerical simulations and (iii) the Lagrangian perturbation code pinocchio . We show that the pinocchio MAHs are in excellent agreement with those obtained using numerical simulations, while the EPS formalism predicts MAHs that occur too late. pinocchio , which is much less CPU intensive than N -body simulation, can be run on a simple personal computer, and does not require any labour intensive post-simulation analysis, therefore provides a unique and powerful tool to investigate the growth history of dark matter haloes. Using a suite of 55 pinocchio simulations, with 256³ particles each, we study the MAHs of 12 924 cold dark matter (CDM) haloes in a ΛCDM concordance cosmology. This is by far the largest set of haloes used for any such analysis. For each MAH we derive four different formation redshifts, which characterize different epochs during the assembly history of a dark matter halo. We show that haloes less massive than the characteristic non-linear mass scale establish their potential wells much before they acquire most of their mass. The time when a halo reaches its maximum virial velocity roughly divides its mass assembly into two phases, a fast-accretion phase which is dominated by major mergers, and a slow-accretion phase dominated by minor mergers. Each halo experiences about 3 ± 2 major mergers since its main progenitor had a mass equal to 1 per cent of the final halo mass. This major merger statistic is found to be virtually independent of halo mass. However, the average redshift at which these major mergers occur is strongly mass dependent, with more massive haloes experiencing their major mergers later.  相似文献