Staff Publications

Staff Publications

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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

    Full text documents are added when available. The database is updated daily and currently holds about 240,000 items, of which 72,000 in open access.

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    Lowland stream restoration by sand addition: Impact, recovery, and beneficial effects on benthic invertebrates
    Reis Oliveira, Paula C. dos; Kraak, Michiel H.S. ; Verdonschot, Piet F.M. ; Verdonschot, Ralf C.M. - \ 2019
    River Research and Applications 35 (2019)7. - ISSN 1535-1459 - p. 1023 - 1033.
    channel incision - instream habitat restoration - macroinvertebrates - rheophilic species - sand addition - sedimentation

    Up to now, most lowland stream restoration projects were unsuccessful in terms of ecological recovery. Aiming to improve the success of stream restoration projects, a novel approach to restore sandy-bottom lowland streams degraded by channel incision was launched, consisting of the addition of sand to the stream channel in combination with the introduction of coarse woody debris. Yet it remained unknown whether this novel measure of sand addition is actually effective in terms of biodiversity improvements. The aim of the present study was therefore to evaluate if sand addition can improve hydromorphological stream complexity on the short term leading to an increase in macroinvertebrate biodiversity. To this end, particle transport, water depth, current velocity, dissolved oxygen dynamics, and sediment composition were measured. The response of the macroinvertebrate community composition was determined at different stages during the disturbance and short-term recovery process. Immediately downstream the sand addition site, transport and sedimentation of the sand were initially intense, until an equilibrium was reached and the physical conditions stabilized. The stream section matured fast as habitat formation took place within a short term. Macroinvertebrate diversity decreased initially but recovered rapidly following stabilization. Moreover, an increase in rheophilic taxa was observed in the newly formed habitats. Thus, although sand addition initially disturbed the stream, a relatively fast physical and biological recovery occurred, leading to improved instream conditions for a diverse macroinvertebrate community, including rheophilic taxa. Therefore, we concluded that sand addition is a promising restoration measure for incised lowland streams.

    Data from: Warming enhances sedimentation and decomposition of organic carbon in shallow macrophyte-dominated systems with zero net effect on carbon burial
    Velthuis, Mandy ; Kosten, S. ; Aben, Ralf ; Kazanjian, Garabet ; Hilt, Sabine ; Peeters, E.T.H.M. ; Donk, Ellen van; Bakker, Elisabeth S. - \ 2019
    NIOO-KNAW
    carbon cycle - decomposition - global warming - mineralization - phenology - primary production - sedimentation - submerged aquatic plant
    Temperatures have been rising throughout recent decades and are predicted to rise further in the coming century. Global warming affects carbon cycling in freshwater ecosystems, which both emit and bury substantial amounts of carbon on a global scale. Currently, most studies focus on the effect of warming on overall carbon emissions from freshwater ecosystems, while net effects on carbon budgets may strongly depend on burial in sediments. Here, we tested whether year‐round warming increases the production, sedimentation, or decomposition of particulate organic carbon and eventually alters the carbon burial in a typical shallow freshwater system. We performed an indoor experiment in eight mesocosms dominated by the common submerged aquatic plant Myriophyllum spicatum testing two temperature treatments: a temperate seasonal temperature control and a warmed (+4°C) treatment (n = 4). During a full experimental year, the carbon stock in plant biomass, dissolved organic carbon in the water column, sedimented organic matter, and decomposition of plant detritus were measured. Our results showed that year‐round warming nearly doubled the final carbon stock in plant biomass from 6.9 ± 1.1 g C in the control treatment to 12.8 ± 0.6 g C (mean ± SE), mainly due to a prolonged growing season in autumn. DOC concentrations did not differ between the treatments, but organic carbon sedimentation increased by 60% from 96 ± 9.6 to 152 ± 16 g C m−2 year−1 (mean ± SE) from control to warm treatments. Enhanced decomposition of plant detritus in the warm treatment, however, compensated for the increased sedimentation. As a result, net carbon burial was 40 ± 5.7 g C m−2 year−1 in both temperature treatments when fluxes were combined into a carbon budget model. These results indicate that warming can increase the turnover of organic carbon in shallow macrophyte‐dominated systems, while not necessarily affecting net carbon burial on a system scale.
    Warming enhances sedimentation and decomposition of organic carbon in shallow macrophyte-dominated systems with zero net effect on carbon burial
    Velthuis, Mandy ; Kosten, Sarian ; Aben, Ralf ; Kazanjian, Garabet ; Hilt, Sabine ; Peeters, Edwin T.H.M. ; Donk, Ellen van; Bakker, Elisabeth S. - \ 2018
    Global Change Biology 24 (2018)11. - ISSN 1354-1013 - p. 5231 - 5242.
    carbon cycle - decomposition - global warming - mineralization - phenology - primary production - sedimentation - submerged aquatic plant

    Temperatures have been rising throughout recent decades and are predicted to rise further in the coming century. Global warming affects carbon cycling in freshwater ecosystems, which both emit and bury substantial amounts of carbon on a global scale. Currently, most studies focus on the effect of warming on overall carbon emissions from freshwater ecosystems, while net effects on carbon budgets may strongly depend on burial in sediments. Here, we tested whether year-round warming increases the production, sedimentation, or decomposition of particulate organic carbon and eventually alters the carbon burial in a typical shallow freshwater system. We performed an indoor experiment in eight mesocosms dominated by the common submerged aquatic plant Myriophyllum spicatum testing two temperature treatments: a temperate seasonal temperature control and a warmed (+4°C) treatment (n = 4). During a full experimental year, the carbon stock in plant biomass, dissolved organic carbon in the water column, sedimented organic matter, and decomposition of plant detritus were measured. Our results showed that year-round warming nearly doubled the final carbon stock in plant biomass from 6.9 ± 1.1 g C in the control treatment to 12.8 ± 0.6 g C (mean ± SE), mainly due to a prolonged growing season in autumn. DOC concentrations did not differ between the treatments, but organic carbon sedimentation increased by 60% from 96 ± 9.6 to 152 ± 16 g C m−2 yaer−1 (mean ± SE) from control to warm treatments. Enhanced decomposition of plant detritus in the warm treatment, however, compensated for the increased sedimentation. As a result, net carbon burial was 40 ± 5.7 g C m−2 year−1 in both temperature treatments when fluxes were combined into a carbon budget model. These results indicate that warming can increase the turnover of organic carbon in shallow macrophyte-dominated systems, while not necessarily affecting net carbon burial on a system scale.

    Lift up of Lowlands : beneficial use of dredged sediments to reverse land subsidence
    Figueiredo Oliveira, Bruna Raquel - \ 2017
    Wageningen University. Promotor(en): Huub Rijnaarts, co-promotor(en): Tim Grotenhuis. - Wageningen : Wageningen University - ISBN 9789462578838 - 229
    dredgings - dredging - sedimentation - soil - sediment - subsidence - recycling - environmental engineering - bagger - baggeren - sedimentatie - bodem - sediment - bodemdaling - recycling - milieutechniek

    In this thesis, the beneficial use of dredged sediments to reverse land subsidence in lowlands and delta areas is explored. The major constraints for beneficial use of sediments are the contaminant concentrations, and the proper managing of supply and demand of sediments (Chapter 1).

    When sediments are transferred from waterways to upland conditions, a series of processes take place that transform the waterlogged sediments into aerated soils, a process known as ripening. To understand the relation between the sediments and the soils formed, physical/chemical and biological processes were studied at three scales: laboratory scale, mesoscale, and field scale. The knowledge obtained with these experiments can provide guidelines to effectively use dredged sediments to reverse land subsidence.

    In the laboratory experiments, the environmental conditions were controlled, leading to constant water content and optimal oxygen concentration for biological processes. In the mesoscale experiment, the environmental parameters such as wind, precipitation and temperature, were not controlled as the 1 m3 containers used for these experiments were placed outside, in open air conditions. Still, the water level could be monitored and controlled, and the subsidence of the dredged sediment could be monitored. In the field experiment, the environmental and filling conditions could not be controlled but the changes occurring in the deposit were monitored.

    In the first laboratory experiment (Chapter 2) the behaviour of dredged sediments with varying particle size distribution and organic matter content was studied. The dredged sediments were dewatered using suction chambers and then submitted to biochemical ripening during 141 days. The five types of dredged sediments had similar overall behaviour. The most significant observation was that most volume lost during dewatering and biochemical ripening was due to shrinkage and not to organic matter mineralization. Furthermore, the type of organic matter changed in the direction of humification, i.e., more stable compounds were formed. The soils formed from biochemical ripening of dredged sediments had very stable aggregates and the load-bearing capacity was enough to sustain cattle and tractors.

    The second laboratory experiment (Chapter 3) was designed to investigate the influence of mixing compost and the solid fraction of swine manure (low in nutrients) with dredged sediments on dewatering and biochemical ripening. When the supply of dredged sediments is too low to compensate for land subsidence, bio-wastes, such as compost and manure, can be mixed with the sediments to reverse land subsidence. The results of this experiment confirm that most volume lost during ripening was due to shrinkage and not due to organic matter mineralization. Adding compost or the solid fraction of manure to the dredged sediments enhances the changes in the type of organic matter and CO2 production, i.e., the addition results in increased rates of organic matter mineralization which is described in the literature as the priming effect. In addition, the undrained shear strength of the mixtures of sediments with compost or manure was three times higher than the measured values for the sediments alone, meaning that organic amendments will improve the characteristics of the soil formed from ripening of sediments.

    The mesoscale experiment (Chapter 4) was performed during 400 days in 1m3 containers which allowed to control the water level. Two scenarios were tested: upland deposits in which the sediments are allowed to dry; and underwater deposits in which the water level is always 2 cm above the sediments. It was expected that the upland deposit conditions would lead to a higher subsidence than the underwater conditions. However, subsidence of the sediments was very similar for the two scenarios. Also in these experiments it was observed that most subsidence could be attributed to shrinkage and not organic matter mineralization, and the type of organic matter changed in the direction of humification. Furthermore, the water balance indicated that evapotranspiration results in higher loss of water than drainage. Still, in this case the undrained shear strength after 400 days of experiment was not enough to sustain cattle or tractors even though it increased with time.

    The monitored field scale upland deposit of dredged sediments (Chapter 5) is located in the Wormer- en Jisperveld area – North Holland, the Netherlands. The deposit was filled in two stages reaching a maximum height of sediments of 195 cm. After 17 months of monitoring, the subsidence of the sediments was 119 cm to which an extra subsidence of 19.5 cm of the underlying soil due to the overburden pressure was added. The results observed in the upland deposit are in line with the laboratory and mesoscale results since subsidence could also be attributed to shrinkage and no significant changes in the organic matter content were observed. However, in the case of the upland deposit, the type of organic matter changed in the direction of humification during the first 8 months (March to November), then stabilized during 7 months (November to June), and changed in the direction of mineralization afterwards.

    The outcomes of this research indicate that dredged sediments have the potential to reverse land subsidence. This statement is supported by the consistent results showing that the decrease in volume of dredged sediments is caused by shrinkage and not to organic matter mineralization as traditionally reported (Chapters 2, 3, 4, and 5).

    In addition, in places where composted and stable bio-wastes are available, these can be added to dredged sediments to further reverse land subsidence. Still, in this case special attention should be given to the potential priming effect (Chapter 3).

    Finally it is recommended to adapt the current practices of disposal of dredged sediments in upland deposits, since 19.5 cm of subsidence observed for the underlying soil in the upland deposit (Chapter 5), was caused by the overburden pressure of the dredged sediment. From the point of view of avoiding/reversing land subsidence it is recommended to spread thin layers (in the order of cm) of sediments over the land, although this might lead to an increase in the time and costs for the stakeholders involved in dredging and in managing the water boards.

    Fate of nano- and microplastic in freshwater systems: A modeling study
    Besseling, Ellen ; Quik, Joris T.K. ; Sun, Muzhi ; Koelmans, Bart - \ 2017
    Environmental Pollution 220 (2017)Part A. - ISSN 0269-7491 - p. 540 - 548.
    microplastics - particles - water pollution - water quality - sedimentation - fresh water - hydrodynamics - microplastics - deeltjes - waterverontreiniging - waterkwaliteit - sedimentatie - zoet water - hydrodynamica
    Riverine transport to the marine environment is an important pathway for microplastic. However, information on fate and transport of nano- and microplastic in freshwater systems is lacking. Here we present scenario studies on the fate and transport of nano-to millimetre sized spherical particles like microbeads (100 nm–10 mm) with a state of the art spatiotemporally resolved hydrological model. The model accounts for advective transport, homo- and heteroaggregation, sedimentation-resuspension, polymer degradation, presence of biofilm and burial. Literature data were used to parameterize the model and additionally the attachment efficiency for heteroaggregation was determined experimentally. The attachment efficiency ranged from 0.004 to 0.2 for 70 nm and 1050 nm polystyrene particles aggregating with kaolin or bentonite clays in natural freshwater. Modeled effects of polymer density (1–1.5 kg/L) and biofilm formation were not large, due to the fact that variations in polymer density are largely overwhelmed by excess mass of suspended solids that form heteroaggregates with microplastic. Particle size had a dramatic effect on the modeled fate and retention of microplastic and on the positioning of the accumulation hot spots in the sediment along the river. Remarkably, retention was lowest (18–25%) for intermediate sized particles of about 5 μm, which implies that the smaller submicron particles as well as larger micro- and millimetre sized plastic are preferentially retained. Our results suggest that river hydrodynamics affect microplastic size distributions with profound implications for emissions to marine systems.
    Opslibbing en vegetatie kwelder Ameland-Oost, jaarrapportage 2015
    Groot, A.V. de; Regteren, M. van; Weide, B.E. van der - \ 2016
    Den Helder : IMARES Wageningen UR (Rapport / IMARES C049/16) - 32
    vegetatiemonitoring - vegetatie - sedimentatie - monitoring - bodemdaling - nederlandse waddeneilanden - vegetation monitoring - vegetation - sedimentation - monitoring - subsidence - dutch wadden islands
    In 2015 zijn op de kwelder van Ameland-Oost de opslibbing en vegetatieontwikkeling gemeten, als onderdeel van de lopende monitoring naar de effecten van de bodemdaling door gaswinning. De meting vindt plaats op twee raaien, in totaal bestaande uit 38 permanente kwadraten (pq’s) met SEBs (Sedimentatie-Erosiebalk). De observaties over 2015 passen grotendeels binnen de tot nu toe gemeten trends in maaiveldhoogte en vegetatieontwikkeling op Ameland en de natuurlijke variatie in opslibbing en vegetatieontwikkeling.
    Modelling foredune dynamics in response to climate change
    Keijsers, J.G.S. - \ 2015
    Wageningen University. Promotor(en): Coen Ritsema, co-promotor(en): Michel Riksen; Alma de Groot. - Wageningen : Wageningen University - ISBN 9789462575844 - 186
    klimaatverandering - duinen - kustgebieden - vegetatie - sedimentatie - hoogwaterbeheersing - modelleren - nederland - climatic change - dunes - coastal areas - vegetation - sedimentation - flood control - modeling - netherlands

    Coastal dunes are prominent features along many of the world’s sandy shorelines. They are valued for their contributions to flood protection, biodiversity, fresh water supply and recreation. The most seaward dune ridge or foredune is the most dynamic part, showing fluctuations in size and morphology in response to erosion by the sea and subsequent recovery by interactions between wind-blown sand and vegetation. Given their dependency on multiple natural processes, coastal dunes may be particularly sensitive to the effects of climate change, including sea-level rise (SLR) and changes in temperature and precipitation.

    To mitigate anticipated coastal erosion in the next decades, the Dutch sand nourishment regime will be intensified to raise the beach profile proportionally to the SLR. However, it is not clear how the added sand is distributed within the foredune system and whether this enables foredunes to keep up with sea-level rise. In addition, possibilities for dune re-mobilisation are investigated to enhance landward transport and biodiversity. However, effects of this intervention on foredune dynamics and the dune landscape are not entirely clear.

    This thesis has examined yearly to decadal scale foredune dynamics and the impacts of climate change and management options on these dynamics.

    Which factors control year-to-year variations in dune growth on the Dutch coast?

    Dunes depend on aeolian transport for sand supply. While measurements of aeolian transport show complex spatio-temporal variations, we find that the yearly sand supply to dunes along the Dutch coast is relatively constant, between 10-20 m3/m irrespective of the beach width (Chapter 2). This means that a wider beach does not necessarily provide more sand to dunes and beach width is not a limiting factor in sand supply to the dunes.

    In contrast to the sand input, the amount of sand lost during a storm surge does depend on the beach width. Wider beaches are able to dissipate more of the incoming wave energy and thus protect the dune better than narrow beaches. On a term of decades, this gives rise to steady dune growth on wider beaches and irregular, frequently interrupted growth on narrow ones.

    How do biogeomorphic interactions control foredune shape?

    The distribution of sand over the foredune, and therefore the morphological evolution, is strongly tied to vegetation patterns (Chapter 3). It was found that deposition patterns across foredunes show a characteristic distribution, starting with a sharp increase upon crossing the seaward vegetation limit, reaching a maximum between 5-20 m further landward and then gradually decreasing inland of the crest. The deposition pattern is further modified by the general vegetation pattern. On a timescale of years, there is no correlation between density of vegetation cover and the amount of accretion. However, by accounting for the gradual depletion of the sand load over the foredune, an empirical relationship can be defined between vegetation cover and its sand trapping efficiency. For fully covered surfaces, sand trapping efficiency is around 50%, indicating that sediment can pass densely covered foredunes.

    Although literature suggests a relation between the level of plant burial and plant growth, we found no evidence for enhanced vegetation growth in high-deposition zones. A gain in vegetation cover was found to occur for burial between 0 m/year and 1 m/year, which indicates that lower and upper tolerance limits of burial have not been exceeded. Other growth limiting factors are likely to be of similar importance, masking any possible dependency of vegetation growth on sand accretion.

    What are the effects of climate change on meso-scale evolution of coastal dunes?

    The results on yearly erosion/accretion and sedimentation patterns were implemented in a computer for dune evolution called DUBEVEG, developed in Wageningen (Chapter 4). Algorithms for aeolian transport and vegetation growth were taken from existing models and combined with a new module for wave action and dune erosion. The model was calibrated and validated against field measurements. The good agreement between observations and predictions indicates that the model successfully incorporates the suite of biogeomorphic and marine processes involved in dune building.

    Model simulations show that the evolution of a dune strongly depends on the sequence of storms and quiet periods. During quiet periods, dunes are able to build seaward at several metres per year as vegetation colonises the area near the dune foot, leading to dune accretion. Following the dune-foot position through time, we find an irregular pattern of seaward advance and regression. However, the average of a large number of runs with varying storm sequences reveals a clear trend. For a given wave climate and beach profile, we find that the model predicts a certain seaward limit to which the foredunes may build, or equilibrium position at which erosion and accretion are balanced. If the momentary position of the dune foot is seaward of this limit, seaward movement can be rapid. If, in contrast, the momentary position is at or seaward of the limit, periods of minor seaward growth are followed by periods of landward retreat, resulting in an oscillation around the equilibrium.

    Climate scenarios, consisting of SLR and a gradual change in vegetation growth, were developed to examine climate-change effects on dune dynamics. Sea-level rise largely determines the direction of dune evolution by forcing the dune-foot landwards. The rate of rising controls whether dunes are able to preserve their height or sand volume while migrating landwards. The effect of changing vegetation growth rates, resulting from climate change, is most manifest in dune response to large disturbances. If vegetation is removed halfway into the simulation, vegetation growth rate determines whether a foredune will re-vegetate and re-stabilise: a value below the threshold will preclude complete recovery and the dune remains bare.

    What management options are available to mitigate climate-change effects on coastal dune evolution?

    Sand nourishments are effective to mitigate the effect of SLR on coastal dunes. Model results show that by raising the beach proportionally to SLR, dunes are able to preserve their dunefoot position, height and volume. sHowever, the associated landward retreat is often not feasible.

    A reduction in vegetation cover, related to either (1) artificial remobilisation, (2) dunefoot erosion or (3) climate change promotes landwards transport and therefore contributes to the long-term preservation of a wider dune zone. If vegetation growth is reduced as a consequence of increasing summer drought, re-mobilisation becomes more effective, with high rates of landwards transport persisting for several decades.

    On the long term, it is recommended to use a combination of sand nourishments and remobilisation efforts to preserve the coastline, promote landwards transport and make benefit of a dune’s natural self-regenerating capacity. Under the precondition that safety requirements are met, these natural processes enable long-term preservation of flood protection, biodiversity and dynamic landscapes.

    Spatially explicit fate modelling of nanomaterials in natural waters
    Quik, J.T.K. ; Klein, J.J.M. de; Koelmans, A.A. - \ 2015
    Water Research 80 (2015). - ISSN 0043-1354 - p. 200 - 208.
    engineered nanomaterials - aquatic environments - nanoparticles - aggregation - systems - exposure - sedimentation - calibration - matrices - silver
    Site specific exposure assessments for engineered nanoparticles (ENPs) require spatially explicit fate models, which however are not yet available. Here we present an ENP fate model (NanoDUFLOW) that links ENP specific process descriptions to a spatially explicit hydrological model. The link enables the realistic modelling of feedbacks between local flow conditions and ENP fate processes, such as homo- and heteroaggregation, resuspension and sedimentation. Spatially explicit simulations using five size classes of ENPs and five size classes of natural solids showed how ENP sediment contamination ‘hot spots’ and ENP speciation can be predicted as a function of place and time. For the catchment modelled, neglect of spatial heterogeneity caused relatively small differences in ENP retention. However, simplification of the number of size classes to one average class, resulted in up to 3.3 times lower values of retention compared to scenarios that used detailed size distributions. Local concentrations in sediment were underestimated up to 20 fold upon simplification of spatial heterogeneity or particle size distribution. We conclude that spatial heterogeneity should not be neglected when assessing the risks of ENPs.
    Simplifying modeling of nanoparticle aggregation-sedimentation behavior in environmental systems: A theoretical analysis
    Quik, J.T.K. ; Meent, D. van de; Koelmans, A.A. - \ 2014
    Water Research 62 (2014). - ISSN 0043-1354 - p. 193 - 201.
    sedimentatie - bodemdeeltjes - waterkwaliteit - modellen - sedimentation - aggregates - water quality - models - engineered nanoparticles - carbon nanotubes - nanomaterials - exposure - heteroaggregation - coagulation - challenges - scenarios - kinetics - release
    Parameters and simplified model approaches for describing the fate of engineered nanoparticles (ENPs) are crucial to advance the risk assessment of these materials. Sedimentation behavior of ENPs in natural waters has been shown to follow apparent first order behavior, a ‘black box’ phenomenon that is insufficiently understood and therefore of limited applicability. Here we use a detailed Smoluchowski-Stokes model that accounts for homo- and heteroaggregation and sedimentation of ENPs and natural colloids (NCs), to simulate and interpret experimental ENP aggregation-sedimentation data. The model adequately simulated the observed time and initial concentration dependence of CeO2 settling data, and also predicted the conditions for aggregation rate-limitations of overall removal. Heteroaggregation with natural colloids was identified as the dominating removal process. Finally, the empirical apparent first order model data were calibrated against the mechanistic Smoluchowski-Stokes model simulation data, showing excellent fits for a range of NC initial concentrations. Using first order removal rates thus can be considered a valid and informed approximation when modeling ENP fate in the aquatic environment
    Heteroaggregation and sedimentation rates for nanomaterials in natural waters
    Quik, J.T.K. ; Velzeboer, I. ; Wouterse, M. ; Koelmans, A.A. ; Meent, D. van de - \ 2014
    Water Research 48 (2014)1. - ISSN 0043-1354 - p. 269 - 279.
    sedimentatie - zwevende deeltjes - aggregatie - nanotechnologie - emissie - schatting - colloïden - waterstroming - zeewater - oppervlaktewaterkwaliteit - sedimentation - suspended solids - aggregation - nanotechnology - emission - estimation - colloids - water flow - sea water - surface water quality - engineered nanomaterials - silver nanoparticles - carbon nanotubes - manufactured nanoparticles - aggregation kinetics - aquatic environments - ceo2 nanoparticles - organic-matter - fate - exposure
    Exposure modeling of engineered nanomaterials requires input parameters such as sedimentation rates and heteroaggregation rates. Here, we estimate these rates using quiescent settling experiments under environmentally relevant conditions. We investigated 4 different nanomaterials (C60, CeO2, SiO2-Ag and PVP-Ag) in 6 different water types ranging from a small stream to seawater. In the presence of natural colloids, sedimentation rates ranged from 0.0001md-1 for SiO2-Ag to 0.14md-1 for C60. The apparent rates of heteroaggregation between nanomaterials and natural colloids were estimated using a novel method that separates heteroaggregation from homoaggregation using a simplified Smoluchowski-based aggregation-settling equation applied to data from unfiltered and filtered waters. The heteroaggregation rates ranged between 0.007 and 0.6Lmg-1 day-1, with the highest values observed in seawater. We argue that such system specific parameters are key to the development of dedicated water quality models for ENMs.
    Ecosystem-based coastal defence in the face of global change
    Temmerman, S. ; Meire, P. ; Bouma, T.J. ; Herman, P.M.J. ; Ysebaert, T. ; Vriend, H.J. de - \ 2013
    Nature 504 (2013). - ISSN 0028-0836 - p. 79 - 83.
    tidal marsh - scheldt estuary - climate-change - storm surges - sea-level - restoration - sedimentation - strategies - mangroves - carbon
    The risk of flood disasters is increasing for many coastal societies owing to global and regional changes in climate conditions, sea-level rise, land subsidence and sediment supply. At the same time, in many locations, conventional coastal engineering solutions such as sea walls are increasingly challenged by these changes and their maintenance may become unsustainable. We argue that flood protection by ecosystem creation and restoration can provide a more sustainable, cost-effective and ecologically sound alternative to conventional coastal engineering and that, in suitable locations, it should be implemented globally and on a large scale.
    Controlling eutrophication by combined bloom precipitation and sediment phosphorus inactivation
    Lürling, M.F.L.L.W. ; Oosterhout, J.F.X. - \ 2013
    Water Research 47 (2013)17. - ISSN 0043-1354 - p. 6527 - 6537.
    meren - oppervlaktewaterkwaliteit - eutrofiëring - cyanobacteriën - sedimentatie - uitvlokking - lanthaan - bentoniet - tests - fosfor - ecologisch herstel - noord-brabant - lakes - surface water quality - eutrophication - cyanobacteria - sedimentation - flocculation - lanthanum - bentonite - tests - phosphorus - ecological restoration - noord-brabant - prymnesium-parvum haptophyceae - harmful cyanobacterial blooms - dissolved organic-matter - rare-earth-elements - of-the-art - microcystis-aeruginosa - lake restoration - local soils - polyaluminum chloride - phosphate adsorption
    The hypothesis that the combination of the flocculent polyaluminium chloride (PAC) with the lanthanum-modified bentonite Phoslock® (Flock & Lock) could sink effectively a water bloom of cyanobacteria and could shift a turbid, cyanobacteria infested lake to a clear water lake was tested in a controlled laboratory experiment and a whole lake experiment. In the laboratory, a relatively low dose of the flocculent PAC (2.2 and 4.4 mg Al l-1) was insufficient to sediment positively buoyant cyanobacteria (Microcystis aeruginosa). Similarly, the lanthanum modified clay (dosed at 390 mg l-1) was insufficient to sediment the positively buoyant cyanobacteria. However, the combination of PAC and Phoslock® effectively sedimented cyanobacteria flocks. Likewise, a combined treatment of 2 tons PAC and 18 tons Phoslock® in Lake Rauwbraken in April 2008 effectively sedimented a developing cyanobacteria bloom of Aphanizomenon flos-aquae. The average chlorophyll-a concentration in the two years prior to this Flock & Lock treatment was 19.5 (±36.5) µg l-1, while it was as low as 3.7 (±4.5) µg l-1 in the years following the treatment. The combined treatment effectively reduced the amount of total phosphorus (TP) in the water column from on average 169 (±126) µg P l-1 before the application to 14 (±15) µg P l-1 after the treatment. Based on mean summer chlorophyll-a and TP concentrations, the lake was shifted from a eutrophic/hypertrophic state to an oligo/mesotrophic state. From directly after treatment in April 2008 until and including 2013, Lake Rauwbraken remained in an oligo-mesotrophic clear water state with TP reduced to less than 10% of the pre-treatment. This result shows that eutrophication in relatively small, isolated, stratifying lakes can be restored by targeting both water column and sediment P using a combination of flocculent and solid phase P-sorbent
    Trade-offs between biodiversity and flood protection services of coastal salt marshes
    Loon-Steensma, J.M. van; Vellinga, P. - \ 2013
    Current Opinion in Environmental Sustainability 5 (2013)3-4. - ISSN 1877-3435 - p. 320 - 326.
    zoutmoerassen - kustgebieden - herstelbeheer - ecosysteemdiensten - hoogwaterbeheersing - klimaatadaptatie - biodiversiteit - natuurbeheer - salt marshes - coastal areas - restoration management - ecosystem services - flood control - climate adaptation - biodiversity - nature management - sea-level rise - vegetation - ecosystems - wetlands - sedimentation - restoration - attenuation - management - dynamics - systems
    Coastal salt marshes provide a range of ecosystem services. However, their area is steadily diminishing as a result of human-made modifications to the coastal zone. The accelerated rise of sea level is another challenge to the self-generating capacity of coastal salt marshes. This is a subject of extensive research, leading to conservation and restoration strategies. The value of salt marshes as a natural sea defense is an area of growing interest as well. This article reviews salt-marsh restoration options described in the literature, including the idea of sediment nourishment on the scale of the estuary or lagoon as a whole. It then considers trade-offs between enhancement of salt marshes’ flood protection service and the ecological quality of the ecosystem
    De invloed van de waterbodem op de waterkwaliteitsdoelen van het Noordzeekanaal : met specifieke aandacht voor de dioxineproblematiek
    Postma, J. ; Rozemeijer, M.J.C. ; Schobben, J.H.M. - \ 2013
    IJmuiden : IMARES (Rapport / IMARES Wageningen UR C092/13) - 210
    waterwegen - waterbodems - sedimentatie - dioxinen - bodemverontreiniging - ecotoxicologie - noord-holland - waterways - water bottoms - sedimentation - dioxins - soil pollution - ecotoxicology - noord-holland
    De waterbodem in het Noordzeekanaal is in het verleden ernstig verontreinigd geraakt met dioxines, onder andere door een explosie van een reactorvat bij Philips Duphar in 1963 bij de Jan van Riebeeckhaven. Een aanvankelijk geplande waterbodemsanering is in 2009 vanwege een bezuinigingstaakstelling komen te vervallen. Daaropvolgend is Rijkswaterstaat West-Nederland Noord in 2010 als beheermaatregel begonnen met monitoring van het gebied om na te gaan in hoeverre er verspreiding optreedt van dioxines naar de omliggende waterbodem en biota. De verkregen data zijn aangevuld met andere beschikbare monitoringgegevens en verwerkt tot een totaaloverzicht van het Noordzeekanaal van de waterbodem- en zwevend-stofkwaliteit en van bioaccumulatie van verontreinigingen.
    The impact of erosion protection by Stone Dams on Salt-Marsh vegetation on Two Wadden Sea Barrier Islands
    Loon-Steensma, J.M. van; Slim, P.A. - \ 2013
    Journal of Coastal Research 29 (2013)4. - ISSN 0749-0208 - p. 783 - 796.
    dammen - zoutmoerassen - habitats - erosiebestrijding - vegetatie - sedimentatie - biodiversiteit - nederlandse waddeneilanden - dams - salt marshes - habitats - erosion control - vegetation - sedimentation - biodiversity - dutch wadden islands - level rise - defense
    This paper describes and quantifies the effect of low stone dams on the extent and composition of salt-marsh habitats on two Dutch Wadden islands: Terschelling and Ameland. The stone dams were built to prevent erosion of the salt-marsh edge. Analyses of a series of aerial photographs taken between 1949 and 2010 show a strong reduction in retreat of the marsh edge on the island of Terschelling, from an average rate of 1.3 m per year before construction of the dam to 0.2 m per year after dam construction. Within 20 years of construction of the dam, sedimentation raised the mudflats between the dam and the former cliff, creating a broader foreshore and new marsh area with typical salt-marsh vegetation cover. The dam on the island of Ameland was built on the remnants of a previous low coastal defense. This reinforcement stopped cliff retreat and led to restoration of the eroded salt-marsh strip. Vegetation surveys along transects perpendicular to the coastline revealed that at both sites, typical pioneer salt-marsh vegetation had developed in the raised area between the erosion protection works and the former marsh edge. These habitats were not found in the reference transects without erosion protection. Based on these findings, we conclude that under favorable conditions for sedimentation, erosion protection by low stone dams may bring about a strong reduction in retreat of the salt-marsh edge while helping to restore an ecological attractive foreshore zone.
    Characterization of Escherichia coli nucleoids released by osmotic shock
    Wegner, S. ; Alexeeva, S.V. ; Odijk, T. ; Woldringh, C.L. - \ 2012
    Journal of Structural Biology 178 (2012)3. - ISSN 1047-8477 - p. 260 - 269.
    folded chromosome - salmonella-typhimurium - branched polymers - dna - sedimentation - fluorescence - chloroquine - compaction - dynamics - domains
    Nucleoids were isolated by osmotic shock from Escherichia coli spheroplasts at relatively low salt concentrations and in the absence of detergents. Sucrose-protected cells, made osmotically sensitive by growth in the presence of ampicillin or by digestion with low lysozyme concentrations (50–5 µg/ml), were shocked by 100-fold dilution of the sucrose buffer. Liberated nucleoids stained with 4',6-diamidino-2-phenylindole dihydrochloride hydrate (DAPI), the dimeric cyanine dye TOTO-1, or fluorescent DNA-binding protein appeared as cloud-like structures, in the absence of phase contrast. Because UV-irradiation disrupted the DAPI-stained nucleoids within 5–10 s, they were imaged by time-lapse microscopy with exposure times less than 2 s. The volume of nucleoids isolated from ampicillin- or low-lysozyme spheroplasts and minimally exposed to UV (4 s) UV irradiation. We interpret the measured volume in terms of a physical model of the nucleoid viewed as a branched DNA supercoil crosslinked by adhering proteins into a homogeneous network.
    DEB ensis vs. data
    Schellekens, T. ; Witbaard, R. - \ 2012
    Yerseke : IMARES (Rapport / IMARES Wageningen UR C155/12) - 29
    zandafgravingen - ensis - sedimentatie - zandsuppletie - monitoring - kustgebieden - noordzee - sand pits - ensis - sedimentation - sand suppletion - monitoring - coastal areas - north sea
    Along the Dutch coast (North sea) large quantities of sand are mined in certain locations to supply sand for coastal defence at other locations in order to retain the existing coastline. Without these nourishments of sand the coast would erode and eventually this erosion would lead to an increased risk of flooding. This project provides the opportunity to use measured environmental data to predict growth of Ensis directus using the DEBEnsis model and compare it to measured biotic data on Ensis. Here we report on the findings of the comparison of field data and model estimates and suggest improvements, both in field measurements, experiments and (adjustments to DEB) modelling. For this study, Ensis directus was taken as a model organism, because of its high dominance in biomass in the Dutch coastal zone.
    Modeling migration in sheared bidisperse suspensions using an effective termperature
    Sman, R.G.M. van der; Vollebregt, H.M. ; Boom, R.M. - \ 2012
    Faraday Discussions 158 (2012). - ISSN 1359-6640 - p. 89 - 103.
    pressure-driven flow - concentrated suspensions - polydisperse suspensions - numerical simulations - self-diffusion - fluidized beds - shear-flow - spheres - sedimentation - instabilities
    A model for the particle migration in a bidisperse flowing suspension is proposed and compared to experimental data. A mixture formulation, describing the suspension velocity and pressure and the concentrations of two solid fractions is derived from a multi-fluid model. In the multi-fluid model the liquid phase and both dispersed phases are interpenetrating phases. The closure relations are based on a mean field approach extending closure relations of a monodisperse suspension. The model is used to predict segregation based on particle size in channel flow where the particles are subjected to Brownian motion and shear-induced migration. The comparison of the model results with experimental data shows that particle migration is predicted well by the given formulation.
    Groei en conditie van zwaardschede (Ensis directus, Conrad) voor, tijdens en na geplande zandwinning in 2013 - 2017: Berekeningen voor het HHNK
    Schellekens, T. - \ 2012
    Yerseke : IMARES (Rapport / IMARES Wageningen UR C089/12) - 45
    zandafgravingen - ensis - kustgebieden - nadelige gevolgen - monitoring - noordzee - algen - sedimentatie - sand pits - ensis - coastal areas - adverse effects - monitoring - north sea - algae - sedimentation
    In dit project is het effect van zandwinning op de groei van Ensis directus geanalyseerd d.m.v. een Dynamic Energy Budget (DEB) model voor een zestal punten gelegen op drie raaien in de kustzone. Centrale vraag bij het gezamenlijke Deltares-IMARES onderzoek was: Wat is het effect van zandwinning op de slib- en algenconcentraties in de Noordzee en Waddenzee en op de groei en conditie van zwaardschede Ensis directus gegeven de berekende veranderingen in slib en algenconcentraties.
    Mind the gap: modelling event-based and millennial-scale landscape dynamics
    Baartman, J.E.M. - \ 2012
    Wageningen University. Promotor(en): Tom Veldkamp; Coen Ritsema, co-promotor(en): Jeroen Schoorl. - S.l. : s.n. - ISBN 9789461732668 - 216
    geomorfologie - erosie - sedimentatie - dynamica - tijdschalen - landschapsanalyse - modelleren - rivieren - regen - menselijke invloed - landschap - ontwikkeling - spanje - pleistoceen - holoceen - geomorphology - erosion - sedimentation - dynamics - time scales - landscape analysis - modeling - rivers - rain - human impact - landscape - development - spain - pleistocene - holocene

    This research looks at landscape dynamics – erosion and deposition – from two different perspectives: long-term landscape evolution over millennial timescales on the one hand and short-term event-based erosion and deposition at the other hand. For the first, landscape evolution models (LEMs) are often used, which describe landscape forming processes by geomorphic transport laws, usually on annual temporal resolutions. LEM LAPSUS is used in this research to evaluate the landscape dynamics in a study area in south-east Spain: the Guadalentín Basin. The model is calibrated on dated river terrace levels, which show an erosion – deposition – erosion sequence that the model could reproduce. Annual precipitation in this dryland area shows large inter-annual variability and erosion is supposed to be mainly the results of low-frequency, high magnitude rainfall events. Therefore, in this research, landscape dynamics are also assessed using the event-based erosion model OpenLISEM. Eventually, the role of extreme events in long-term landscape evolution are explored by comparing the two models and by incorporating annual rainfall variability into LEM LAPSUS. Another issue that is being addressed in this study is the relative influence of humans as compared to erosion as a natural process. A conceptual model, derived on the basis of dated sediment archives, is tentatively correlated to periods of human impact on the land. Using LAPSUS, the potential influence of historical tillage erosion is simulated, showing that the relatively slow process of tillage erosion added to floodplain aggradation over thousands of years.

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