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.
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.
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
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.
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.
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.
Proefsuppletie Galgenplaat Oosterschelde Monitoring effect op productiviteit van mosselpercelen
Mesel, I.G. de; Craeymeersch, J.A.M. ; Wijsman, J.W.M. ; Gool, A.C.M. van - \ 2009
Yerseke : IMARES (Rapport / IMARES Wageningen UR C143/09) - 39
mossels - mosselteelt - sedimentatie - slikken - groei - kwaliteit - baggeren - effecten - oosterschelde - mussels - mussel culture - sedimentation - deglutition - growth - quality - dredging - effects - eastern scheldt
Sinds de aanleg van de stormvloedkering en de compartimenteringsdammen wordt het ecosysteem van de Oosterschelde aangetast door een fenomeen dat ‘zandhonger’ wordt genoemd. Doordat er minder water wordt getransporteerd zijn de geulen overgedimensioneerd. Door de verminderde stroomsnelheden in de geulen sedimenteert daar zand. Dit zand is afkomstig van de omliggende slikken en platen, waardoor deze afkalven. De slikken en platen komen hierdoor steeds lager te liggen. De laatste jaren wordt nagedacht over ingrepen die het proces van de zandhonger kunnen vertragen of. In onderhavige studie is onderzocht hoe de werkzaamheden de groei en kwaliteit van mosselen in de omgeving hebben beïnvloed. De resultaten van deze studie duiden niet op een negatief effect van bagger- en suppletiewerkzaamheden op de groei en ontwikkeling van de mosselen in de omgeving.
Time dependence in jamming and unjamming
Parker, A. - \ 2009
Wageningen University. Promotor(en): Erik van der Linden. - [S.l. : S.n. - ISBN 9789085853879 - 99
gels - stabiliteit - dynamica - reologie - verouderen - sedimentatie - thixotropie - verarming - uitvlokking - xanthan - gelatine - evenwicht - gels - stability - dynamics - rheology - aging - sedimentation - thixotropy - depletion - flocculation - xanthan - gelatin - equilibrium
Three different food systems have been studied: emulsion/polymer mixtures, gelatin gels and carrageenan gels. Typically, samples are trapped, or jammed, far from equilibrium. The simple jamming paradigm suggests that, once in the jammed state, these systems are static. This useful approximation is often too simple, since these systems frequently evolve in time. Their evolution has been measured systematically. Where possible, these results have been placed in the context of the physics of out-of-equilibrium systems.
The emulsion/polymer mixtures are a model for salad dressing. The emulsions alone are colloidally stable, but become inhomogeneous, due to the effects of gravity. With sufficient polymer, they can be apparently stable (jammed) for months, but then quite suddenly start to sediment – the system unjams. The kinetics of this delayed sedimentation is measured as a function of the key parameters. A new model is proposed for the mechanism by which polymers stabilize emulsions.
Solutions of gelatin form gels when cooled, due to the formation of portions of helix. A new model relating the amount of helix to the elasticity is described. The gels always evolve slowly. At steady state, the rate of evolution of the elasticity is constant in log(time), so this system conforms to Struick’s physical aging scenario. The effect of temperature changes on the evolution of gels is extremely complex. The results show that there is a deep analogy between this behavior and that of spin glasses, which are exotic magnetic phases.
Gels of iota carrageenan, a seaweed polysaccharide, have unique rheological properties: they regel almost instantly after strong mixing. This property is used in the dairy industry, but has not been studied previously. The kinetics of recovery after shear has been measured for water gels and milk gels.
Wal, J.T. van der; Dalfsen, J.A. van - \ 2008
Den Helder : IMARES (Rapport / Wageningen IMARES C014/08) - 114
kustbeheer - kustgronden - bodemfauna - benthos - vastleggen van zand - inventarisaties - bescherming - sedimentatie - zandsuppletie - coastal management - coastal soils - soil fauna - benthos - sand stabilization - inventories - protection - sedimentation - sand suppletion
In dit rapport wordt gerapporteerd over onderzoek naar het bodemleven (benthos) in een viertal gebieden voor de Noord-Hollandse kust. Het doel van de studie is om in vier suppletievakken een inventarisatie uit te voeren van de aanwezige bodemfauna. Hierbij wordt vooral aandacht gegeven aan het voorkomen van concentraties (banken) van de schelpdiersoorten Halfgeknotte strandschelp, Spisula subtruncata en mesheften, Ensis spec. Daarnaast wordt ook specifiek aandacht gegeven aan het voorkomen van kokerwormen, waaronder de Schelpkokerworm, Lanice conchilega, die mogelijk een stabiliserende werking hebben op de bodem en indien voorkomend in hoge dichtheden (banken) tevens een habitatstructurerende rol kunnen spelen voor andere soorten. De inventarisatie dient inzicht te geven in de verspreiding van de bodemfauna in de suppletiegebieden en vooral van de genoemde specifieke aandachtssoorten. Deze beschrijving kan gebruikt worden in de toetsing van de suppletieactiviteit aan de Flora- en Faunawet en de Natuurbeschermingswet.
The impact of floodplain sedimentation on vegetation; quantifying nutrient input
Sival, F.P. ; Makaske, B. ; Maas, G.J. ; Runhaar, J. - \ 2004
geologische sedimentatie - sedimentatie - vegetatie - voedingsstoffenopname (planten) - voedingsstoffen - voedingsstoffenbalans - vegetatiemonitoring - vegetatiekunde - geological sedimentation - sedimentation - vegetation - nutrient uptake - nutrients - nutrient balance - vegetation monitoring - vegetation science
Poster outlining a research on the impact of floodplain sedimentation on vegetation; quantifying nutrient input
Bezinklagen: een bron van mineralen
Timmerman, M. ; Smolders, M.M.A.H.H. - \ 2002
Praktijkkompas. Varkens 16 (2002)4. - ISSN 1570-8578 - p. 10 - 11.
mest - varkensmest - varkensdrijfmest - dierlijke meststoffen - varkenshouderij - varkens - afvalverwijdering - mineralen - boekhouding - opslag - chemische samenstelling - stikstof - fosfaat - afvalverwerking - sedimentatie - sediment - mestverwerking - manures - pig manure - pig slurry - animal manures - pig farming - pigs - waste disposal - minerals - accounting - storage - chemical composition - nitrogen - phosphate - waste treatment - sedimentation - sediment - manure treatment
Veel varkensbedrijven kampen met het zogenaamde 'Minas-gat' op hun Minas-aangifte. Uit onderzoek op Praktijkcentrum Rosmalen blijkt dat hoge fosfaat- en stikstofgehalten van de bezinklagen in de mestput een belangrijke oorzaak vormen van het achterblijven van mineralen op het bedrijf. Het is van belang te voorkomen dat de mest bezinkt en de putten goed leeg te zuigen
Avulsions, channel evolution and floodplain sedimentation rates of the anastomosing upper Columbia River, British Columbia, Canada
Makaske, B. ; Smith, D.G. ; Berendsen, H.J.A. - \ 2002
Sedimentology 49 (2002)5. - ISSN 0037-0746 - p. 1049 - 1071.
Canada - fysische geografie - rivierkunde - sedimentatie - Noord-Amerika - Canada
Ages of channels of the anastomosing upper Columbia River, south-eastern British Columbia, Canada, were investigated in a cross-valley transect by C-14 dating of subsurface floodplain organic material from beneath levees. The avulsion history within the transect was deduced from these data, and morphological stages in channel development were recognized. Additionally, floodplain sedimentation rates were established. The new data demonstrate that the upper Columbia River is a long-lived, dynamic anastomosing system. Results show that anastomosis at the study location has persisted since at least 2700 cal. years BP, with avulsions occurring frequently. At least nine channels have formed in the studied cross-valley transect within the past 3000 years. Channel lifetimes from formation to abandonment appear to be highly variable, ranging from approximately 800 to 3000 years. Log jams provoking avulsions and/or silting up of old channels are proposed as reasons for this variability. Long-term average floodplain sedimentation rates appear to be significantly lower than previously proposed by Smith (1983, Int. Assoc. Sedimentol. Spec. Publ., 6, 155-168). A long-term (4550 years) average of 1.75 mm per year (after compaction) was based on C-14 dates, whilea short-term sedimentation rate of 0.8 mm was determined for a single, relatively small, seasonal flood in 1994 using sediment traps. However, short-term sedimentation rates vary considerably over the floodplain, with levees aggrading up to four times faster than floodbasins. Channels of the upper Columbia River anastomosed reach follow a consistent pattern in their development, with each stage being characterized by different morphology and processes. Channel evolution comprises the following succession: (1) avulsion stage, in which a crevasse splay channel deepens by scour and levee sedimentation; (2) widening and deepening stage, in which bank slumping and bed scouring dominates; (3) infilling stage, in which either channel narrowing (bank accretion) or channel shallowing (bed accretion) takes place; and (4) abandonment stage, in which the residual (remnant) channel is filled exclusively by silt, clay and organic material. Vertical stacking (super-imposition) of active channels on recent channel-fill sand bodies is a notable feature of the upper Columbia River, which suggests that reoccupation of residual channels is a common process.
Ecoslib; de ecologische rol van slib
Groenewold, S. ; Dankers, N.M.J.A. - \ 2002
Wageningen : Alterra (Alterra-rapport 519) - 74
slib - bodemfauna - ecosystemen - bodem - sediment - delta's - waterbodems - bodemecologie - bodemtextuur - ecologie - kustgebied - sedimentatie - zeebodem - sludges - soil fauna - ecosystems - soil - sediment - deltas - water bottoms
Slib is een belangrijke parameter in het ecosysteem van kust en zee. Door menselijke activiteiten zoals kustbescherming, ingrepen in rivieren, aanleg van eilanden en havens, openhouden van geulen, en zandwinning wordt de slibhuishouding beonvloed. Ditkan positieve en negatieve effecten op het bestaande ecosysteem hebben. Het is onduidelijk wanneer van negatieve of positieve effecten gesproken kan worden. Ook is onduidelijk in hoeverre slib bepalend is voor het voorkomen van organismen, of dat factoren zoals golfwerking en stroming zowel het voorkomen van organismen als sedimentkarakteristieken zoals slibgehalte bepalen. Daarom werd een studie uitgevoerd waarin op basis van literatuur en ervaringen van specialisten uitgezocht werd wat de ecologische rol van slib is.
The biorotor system for post-treatment of anaerobically treated domestic sewage
Tawfik, A. - \ 2002
Wageningen University. Promotor(en): G. Lettinga; F. El-Gohary; A. Klapwijk. - S.l. : S.n. - ISBN 9789058085658 - 140
anaërobe behandeling - rioolafvalwater - sedimentatie - escherichia coli - anaerobic treatment - sewage effluent - sedimentation - escherichia coli
This thesis describes the evaluation of the applicability of biorotor system for post-treatment (polishing) of different effluent qualities of an UASB reactor treating raw domestic sewage, with emphasis on the elimination of various COD fractions, ammonia and E.Coli.
The removal mechanism of E.Coli from UASB effluent using a RBC has been investigated. The results obtained revealed that an adsorption process and sedimentation comprise the most important removal mechanism of E.Coli in the biofilm. Die-off is relatively minor importance as removal mechanism in a RBC system.
The performance of an anaerobic versus aerobic RBC system treating a high quality UASB reactor effluent was investigated at the same HRT and OLR. The results obtained indicated that the removal efficiency of the COD fractions and of E.Coli fractions found in the aerobic RBC significantly exceeds that of the anaerobic unit. Therefore, the results of our investigations strongly support the use of an aerobic RBC as a post-treatment step of UASB reactor effluents.
When applying a single and two stage aerobic RBC at the same OLR of 14.5 g COD total .m -2.d -1and at a HRT of 2.5 h., but at different temperatures of 24 and 17 °C respectively, both systems provided the same residual effluent values for COD total (72 mg l -1), for COD suspended (16 mg l -1), for COD colloidal (5 mg l -1) and for COD soluble (51 mg l -1). Moreover, also the removal efficiency of E.Coli was almost the same, viz. amounting to 94 %. However, the ammonia removal in the single stage RBC amounted to 50 % of which 71 % was nitrified, compared to only 23 % in the two-stage system. This better performance can be attributed to the higher temperature of the wastewater during the operation of the single stage RBC system. In view of these results, we recommend to use a single stage RBC system for COD removal and for a partial nitrification and E.Coli removal at OLR of 14.5 g COD total .m -2.d -1and at HRT of 2.5 h for post-treatment of a high quality UASB reactor effluent.
We investigated the use of anoxic reactor followed by a segmental two stage aerobic RBC for nitrogen removal from the nitrified effluent. The results obtained reveal that the introduction of an anoxic reactor as a 1 ststage combined with recirculation of the nitrified effluent of the 2 ndstage RBC is accompanied with a conversion of nitrate into ammonia, at least in case the content of COD biod. in the UASB effluent is low. Therefore, the introduction of a separate anoxic reactor for denitrification as final post-treatment step can not be recommended in such a situation.
In one of the experiments the UASB reactor was operated at two different operational temperatures viz. of 30 and 11°C resulting in quite different COD biod. concentrations in the UASB effluent. For the post-treatment of this highly different effluent a single stage RBC was operated at a constant HRT of 1.25 h., consequently at COD biod. loading rates of 17.7 and 36.8 g m -2. d -1. The results clearly show that the residual values of COD fractions and E.Coli are significantly lower at the lower imposed COD biod. loading rate of 17.7g COD biod. m -2. d -1. We also compared the efficiency of the two-stage RBC system for this highly different UASB effluent, viz. once again at the same HRT (2.5 h) and at COD biod. loading rate of 9 and 18 g m -2. d -1. The results reveal that with the two-stage RBC system the residual values of distinguished COD fractions in the final effluent were almost the same, but the residual value of E.Coli in the final effluent amounted to 3.4 x 10 5at the higher COD biod. loading rate and to 7.6 x 10 4/100 ml at the lower one. Moreover, the calculated nitrification rate in the 2 ndstage of two stage RBC system dropped from 1.56 to 1.1 g NO 3 -N.m -2.d -1with an increase the COD biod. loading rate from 11.3 to 16 g m -2.d -1. The results clearly demonstrate that the introduction of a well performing UASB reactor not only improves the nitrification rate but also the E.Coli removal in the post-treatment system.
We compared the performance of the single with that of a two-stage RBC for the treatment of poor quality UASB reactor effluent. The results obtained showed that the COD fractions and the E.Coli content in the final effluent of a two stage were lower than in the effluent of the single stage RBC. Moreover, The calculated nitrification rate in the single stage was much lower compared with the two stages RBC. Based on these results we recommend a two stage RBC system for post-treatment of poor quality UASB reactor effluent. The two-stage system was operated at different HRT's and OLR's in order to assess better design criteria for the system. The removal efficiencies for the various COD fractions decreased only slightly when decreasing the HRT from 10 to 2.5 h., and increasing the OLR from 6.45 to 24 g COD total m -2.d -1. However, the overall nitrification efficiency and E.Coli were negatively affected when increasing the loading conditions in the range investigated. The results found for E.Coli removal revealed that the major part of suspended E.Coli (>4.4 µm) was eliminated by sedimentation or by adsorption in the biofilm of the 1 ststage (99.66 %). However, E.Coli present in the colloidal fraction (< 4.4 - > 0.45 µm) was eliminated in the 2 ndstage of two stage RBC (99.78 %). Based on these results we recommend for the treatment of a poor UASB effluent quality the use of two stages RBC system for the removal of COD fractions and ammonia and for a partial removal of E.Coli at HRT of 10 h and OLR of 6.45 g COD total .m -2.d -1.
The effluent of two stages still cannot be used for unrestricted irrigation purposes, at least according to the standards provided by the WHO with respect to the E.Coli content. Therefore, in order to meet these (very stringent) standards, we investigated the use of a three stage RBC-system for post-treatment of an effluent from a rather poorly performing UASB reactor. This three stage RBC was first operated at a HRT of 3.0 h. Under these conditions the E.Coli count in the final effluent was still too high. However, when applying an HRT of 10 h., the E.Coli content complied almost the WHO standards for unrestricted irrigation purposes. Therefore, when such high removal efficiency for E.Coli really would be required, the best solution is to use three independent stages at HRT of 10 h., which then obviously implies very significantly investment and operational costs.