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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    Fresh Water Lens Persistence and Root Zone Salinization Hazard Under Temperate Climate
    Stofberg, Sija F. ; Oude Essink, G.H.P. ; Pauw, Pieter S. ; Louw, Perry G.B. de; Leijnse, Anton ; Zee, Sjoerd E.A.T.M. van der - \ 2017
    Water Resources Management 31 (2017)2. - ISSN 0920-4741 - p. 689 - 702.
    Fresh water lens - Root zone salinization - Salinity - Simple model - salinization - fresh water - models - water supply - coastal areas - zoutgehalte - verzilting - zoet water - modellen - watervoorziening - kustgebieden

    In low lying deltaic areas in temperate climates, groundwater can be brackish to saline at shallow depth, even with a yearly rainfall excess. For primary production in horticulture, agriculture, and terrestrial nature areas, the fresh water availability may be restricted to so-called fresh water lenses: relatively thin pockets of fresh groundwater floating on top of saline groundwater. The persistence of such fresh water lenses, as well as the quantity and quality of surface water is expected to be under pressure due to climate change, as summer droughts may intensify in North-West Europe. Better understanding through modelling of these fresh water resources may help anticipate the impact of salinity on primary production. We use a simple model to determine in which circumstances fresh water lenses may disappear during summer droughts, as that could give rise to enhanced root zone salinity. With a more involved combination of expert judgement and numerical simulations, it is possible to give an appraisal of the hazard that fresh water lenses disappear for the Dutch coastal regions. For such situations, we derive an analytical tool for anticipating the resulting salinization of the root zone, which agrees well with numerical simulations. The provided tools give a basis to quantify which lenses are in hazard of disappearing periodically, as well as an impression in which coastal areas this hazard is largest. Accordingly, these results and the followed procedure may assist water management decisions and prioritization strategies leading to a secure/robust fresh water supply on a national to regional scale.

    Recirculatie bij Cymbidium
    Kromwijk, J.A.M. ; Voogt, W. - \ 2015
    cymbidium - zoutgehalte - teeltsystemen - glastuinbouw - tuinbouw - recirculatiesystemen - natrium - proeven - monitoring - cymbidium - salinity - cropping systems - greenhouse horticulture - horticulture - recirculating systems - sodium - trials - monitoring
    Tot voor kort had het gewas Cymbidium een vrijstelling voor recirculatie vanwege de zoutgevoeligheid van het gewas en lage EC in de gift. Daardoor is er weinig kennis en ervaring met recirculatie. Voor Cymbidium is nog niet bekend wat de effecten van Natrium zijn. Daarom is onderzoek gestart om vast te stellen bij welk Natriumniveau in de voeding nadelige effecten op gaan treden.
    Geen extra chips na zoutarm eten
    Janssen, A.M. - \ 2015
    WageningenWorld (2015)2. - ISSN 2210-7908 - p. 6 - 6.
    voedingsmiddelen - zoutgehalte - smaak - voedingsonderzoek bij de mens - reductie - gezondheidsgevaren - gezondheidsbevordering - behoeftenbevrediging - foods - salinity - taste - human nutrition research - reduction - health hazards - health promotion - need gratification
    Minder zout in etenswaren zorgt ervoor dat mensen daadwerkelijk minder zout eten; ze zoeken geen zoutcompensatie op andere momenten van de dag.
    Waterkwaliteit en landbouw: mag het ook een beetje zouter zijn?
    Bakel, J. van; Kielen, N. ; Clevering, O.A. ; Roest, C.W.J. - \ 2015
    H2O : tijdschrift voor watervoorziening en afvalwaterbehandeling 43 (2015)5. - ISSN 0166-8439 - p. 56 - 59.
    bodemwater - zoutgehalte - normen - beschadigingen door droogte - gewassen - gewasverliezen - akkerbouw - agrohydrologie - bodemtypen - soil water - salinity - standards - drought injury - crops - crop losses - arable farming - agrohydrology - soil types
    Door de te verwachten gevolgen van de klimaatverandering zal de zoetwatervoorziening van Nederland de komende jaren worden heroverwogen. Daarbij zijn de berekening van de zoutschade in de landbouw als gevolg van beregening met niet-zoet oppervlaktewater en de hantering van normen voor toelaatbare chlorideconcentraties in het oppervlaktewater belangrijke onderdelen. In 2009 is het hierop betrekking hebbende deel van het huidige Droogte-instrumentarium geëvalueerd, gebruik makend van het agrohydrologisch SWAP model. In het aandachtsgebied zijn vier gewassen (gras, aardappelen, suikerbieten en tulpen) op drie grondsoorten (zavel, zand en klei) het meest relevant. Als belangrijkste bevindingen dat de berekening van de zoutschade niet onjuist is, maar dat de gehanteerde normen voor toelaatbare chlorideconcentraties in het oppervlaktewater leiden tot te veel droogteschade en herziening behoeven
    Ion exchange membranes in seawater applications : processes and characteristics
    Galama, A.H. - \ 2015
    Wageningen University. Promotor(en): Huub Rijnaarts, co-promotor(en): Jan Post; Maarten Biesheuvel. - Wageningen : Wageningen University - ISBN 9789462572256 - 272
    drinkwater - ontzilting - ontziltingsinstallaties - elektrodialyse - omgekeerde osmose - membraanpermeabiliteit - zoutgehalte - economische haalbaarheid - drinking water - desalination - desalination plants - electrodialysis - reverse osmosis - membrane permeability - salinity - economic viability

    Officiële titel ENG: Ion exchange membranes in seawater applications. Processes and characteristics

    Officiële titel NL: Ionwisselende membranen in zeewatertoepassingen. Processen en eigenschappen

    Auteur: A.H.Galama

    Jaar: 2015

    ISBN: 978-94-6257-225-6

    Samenvatting

    Zeewaterontzouting stelt mensen in staat om zoet water te maken uit een schijnbaar oneindige water voorraad. Om water ook echt beschikbaar te maken is het een voorwaarde dat de kosten van het ontzoutingsproces zo laag mogelijk zijn. Door gebruik van elektrodialyse (ED), een elektrochemische membraantechnologie voor ontzouting, kunnen de kosten van het ontzoutingsproces mogelijk worden verlaagd. In deze thesis worden de energetische aspecten van ED nader bekeken. De opgelegde hoeveelheid stroom blijkt daarin erg bepalend. Tevens worden de ionwisselende membranen, die in deze toepassing worden gebruikt, nader onderzocht. In de huidige technologische staat kan ED, wat betreft energie en kosten, op grote schaal niet concurreren met omgekeerde osmose. Om ED echt concurrerend te kunnen maken zal de ionische membraanweerstand moeten worden verlaagd en zal de membraanprijs moeten dalen. Voor toepassingen waar een hoge waterefficiëntie nodig is, denk aan ‘zero-liquid-discharge’ ontzoutingsprocessen, lijkt ED aantrekkelijk om als voorontzoutingstechnologie in te zetten.

    Bloemkool geteeld op water 2013
    Blind, M. - \ 2013
    Zwaagdijk : Proeftuin Zwaagdijk - 50 p.
    teeltsystemen - vollegrondsgroenten - hydrocultuur - bloemkolen - proeven op proefstations - plantdichtheid - zoutgehalte - cultuurmethoden - cropping systems - field vegetables - hydroponics - cauliflowers - station tests - plant density - salinity - cultural methods
    In de afgelopen jaren is gebleken dat het mogelijk is bloemkool op het drijvende teeltsysteem te telen maar dat het percentage klasse 1 nog te laag is. Over het algemeen verloopt de gewasontwikkeling in de eerste fase zeer goed. In de eindfase – als de koolvorming plaatsvindt - ontstaan veelal problemen met verwelking. Een duidelijke oorzaak voor de snelle achteruitgang in vitaliteit is nog niet aan te wijzen. Een oorzaak zou kunen zijn een vorm van stress die in de laatste fase van de teelt ontstaat. Het gewas wordt topzwaar en is gevoelig voor wind, ook omdat de groei in de eerste fase juist erg weelderig is. Eén van de doelen van de proeven in 2013 was daarom te onderzoeken of een ruimere plantafstand leidt tot een betere kwaliteit. Een andere techniek om de planten compacter te laten groeien zou het telen bij een hoger zoutgehalte (EC) kunnen zijn. Doordat de planten bij een hoger zoutgehalte minder makkelijk water kunnen opnemen blijven ze compacter.
    Anaerobic wastewater treatment of high salinity wastewaters: impact on bioactivity and biomass retention
    Ismail, S. - \ 2013
    Wageningen University. Promotor(en): Jules van Lier, co-promotor(en): Hardy Temmink; Caroline Plugge. - Wageningen : Wageningen UR - ISBN 9789461738189 - 144
    afvalwaterbehandeling - waterzuivering - afvalwater - anaërobe behandeling - zoutgehalte - biomassa - waste water treatment - water treatment - waste water - anaerobic treatment - salinity - biomass

    Anaerobic sludge bed reactor systems like the upflow anaerobic sludge blanket (UASB) and expended granular sludge bed (EGSB) reactors are currently the mostly applied high-rate reactor systems for anaerobic wastewater treatment. The success of both systems has changed the world conception of wastewater treatment with energy recovery being an intrinsic part of the treatment process, avoidance of excess sludge problems and extremely low space requirement. Nevertheless, while broadening the UASB reactor application to a diverse type of wastewaters, high salinity wastewaters were found to give an adverse effect to the granulation processes. Accumulation of Na+at high concentrations produced weaker and fluffy granules endangering the applicability of the mentioned sludge bed systems. In this thesis, research was conducted to investigate the mechanisms of destabilization of the granules at high Na+concentrations, while trying to improve the granules’ properties. Chapter 1gives an overview of high salinity wastewaters, the application and the bottlenecks of anaerobic wastewater treatment (AnWT) technology under extreme conditions. Focus is given to the granulation process as a key factor in the operation of high rate anaerobic reactors. Indeed, it is a complex process that involves physicochemical as well as biological mechanisms. A short overview of the previous research on anaerobic wastewater treatment processes for high salinity wastewaters is discussed, followed by granulation theories and processes. Referring to the imbalance in the monovalent to divalent cation ratio, the Ca2+augmentation approach is discussed in this chapter as a tool to establish a favourable ratio for the required granulation process. The chapter also discusses the need for extracellular polymeric substances (EPS) production, depending on the types of substrates, as a major factor for a successful granulation process. Specifically for high Na+concentrations, also the importance of K+and more specifically the K+/Na+ratio is discussed as a control regulator to alleviate the negative effects of Na+. Finally, the review discusses microbiological aspects related to the anaerobic treatment of high salinity wastewaters such as the adaptation of sludge to high Na+concentrations and the presence of halophilic/halotolerent microorganisms and their application in anaerobic wastewater treatment.

    In Chapter 2, the effects of high Na+concentrations on methanogenic sludge bed reactor systems were investigated. In three different UASB reactors a rapid acclimation to 5 or 15 g Na+/L was observed, showing satisfactory results for a period of 100 days, when the reactors were fed with a mixture of acetate, gelatine and ethanol. Loading rates up to at least 18 kg COD/m3.d gave a good COD removal performance and the cultivated sludge showed high specific methanogenic activities (SMA) on acetate, propionate, butyrate and H2compared to the inoculated granules. Remarkably, only the reactor which was operated at a lower COD (5 instead of 50 g/L) exhibited severe washout, probably due to the much shorter HRT that was applied, i.e. 12 hours compared to 120 hours. Interestingly, the SMA of the biomass that washed out from this reactor showed considerably higher SMAs than the washed-out biomass from the other reactors. The performance of the granular sludge systems in this study shows the appropriateness of anaerobic inocula, pre-grown under saline conditions for the anaerobic treatment of high salinity wastewater.

    In Chapter 3the production of EPS in UASB reactor systems that were operated under high salinity conditions was investigated. Four different UASB reactors were operated at loading rates up to 22 kg COD/m3.d with different acetate:gelatine:starch ratios as the substrate. Reactors were fed with partially acidified and fully acidified substrates, i.e. PAS and FAS respectively, and Na+concentrations of either 10 or 20 g Na+/L. One of the reactors additionally received 1 g of Ca2+/L. All four reactors showed a good performance with COD removal efficiencies exceeding 90 %. Proteins were the dominant EPS and the PAS-fed granules gave much higher EPS concentrations than FAS-fed granules. However, the proteins concentration was found not dependent on the Na+ concentration in the feed. Interestingly, the granules from the reactors which were operated at a Na+/Ca2+ratio of 770 contained more polysaccharides than granules from reactors operated at a high Na+/Ca2+ratio of 1540. SEM images showed that that PAS-fed granule had a smoother granule surfaces than FAS-fed granule. PAS-fed granules also were considerably larger than FAS-fed granules. When the influent contained additional Ca2+, clear cracks or fissures could be observed on the surface of the granules. Na+ concentrations of 10 g/L seemed to increase the granule size, which may have been caused by swelling of the EPS matrix. Shear tests indicated that PAS-fed granules were stronger than the FAS fed granules and that Ca2+ addition had a positive effect on granule strength. The calcium content of these granules also was higher with 150 mg/g TSS compared to 60 mg/g TSS in the other reactors. Batch tests at high Na+concentrations confirmed calcium leaching from the granules. When granular sludge was exposed to 20 g Na+/L in batches, leaching of Ca2+from granules took place with a maximum obtained after 10 days. The calcium content of the granules decreased from approximately 85 to 52 mg/g TSS. Therefore, the highest Na+concentrations resulted in the weakest granules.

    Chapter 4describes the results of batch incubation studies in which anaerobic granular sludge was augmented with 0.3 g Ca2+/L at Na+concentrations of 20 g/L. Experiments followed the previously described results of Chapter 3 showing that high Na+concentrations caused Ca2+leaching from anaerobic granules. Extensive SEM-EDX and SEM-BSE measurements confirm leaching of calcium from the granules when these are exposed to higher Na+ concentrations. Moreover Ca2+additions seemed to indeed maintain the Ca2+content of granular sludge.

    Initial attachment of microorganism is very important for the development of granules and biofilms. Therefore, biofilm studies were conducted and explained in Chapter 5. Four different biofilm reactors with a non-woven carrier material were exposed to different Na+ concentrations (10 or 20 g/L) and inoculated with crushed granules. Acetate was used as the substrate. One of the reactors received 0.3 g Ca2+/L and another one 0.7 g K+/L. The reactors were operated as sequencing batches. The reactor fed with K+ gave the best performance. Lower salinity (10 compared to 20 g Na+/L) improved the performance and the reactor which received calcium gave the worst results. This finding contradicts with previous experiments in Chapter 3. However, the situation in the biofilm reactors is completely different because the biofilms had to form from scratch. FISH-CLSM images revealed no significant visible differences in microbial coverage (i.e. bacteria and archea) of the non-woven fabric, except for the calcium enriched reactor. After 40 days of operation, it was clearly observed that 20 g Na+/L does not prevent the initial microbial attachment under anaerobic conditions. From 16 sRNA DGGE measurements it was shown that the biofilms had a similar population and that this population did not change very much in time. The Archea were related to Methanosaeta harundinacae (acetoclastic), Methanolinea tarda and Methanobacterium subteraaneum (both hydrogenotrophic). Apparently these species can easily adapt to high salinity. However, the biofilms in the reactors did not show any of the known acetate-oxidizing bacteria that are expectedly needed for the production of H2from acetate as source for the growth of the found hydrogenotrophic Archea. Therefore, it is assumed that H2leakage by acetoclastic methanogen explain their presence in the reactor.

    Four identical UASB reactors treating concentrated wastewaters (10 – 30 g COD/L) were operated at 20 g Na+/L and in detail described in Chapter 6. PAS and FAS substrates were fed to different reactors to compare the effect of different organic substrates on granule activity, stability and growth. The effect of calcium augmentation on anaerobic granules’ properties was studied by feeding two of the reactors with additional calcium at a concentration of 0.3 g Ca2+/L. A beneficial effect of potassium was demonstrated in Chapter 5 and it therefore was added to all the reactors, at a concentration of 0.7 g K+/L. The treatment performance of the reactors was compared during a period of 120 days at increasing volumetric organic loading rates (OLRs). Physicochemical and microbiological properties of the anaerobic granules were determined and discussed. The results showed that high COD removal efficiencies are possible at 20 g Na+/L, up to an organic loading rate of at least 14 g COD/L.d. At a loading rate of 25 g COD/L.d the performance and stability of all reactors deteriorated. There were indications that calcium augmentation had a positive effect on biomass retention, but this could not be further quantified. The microbial assays gave similar results as in Chapter 5. Compared to the inoculum, bacterial diversity in FAS-fed granules did not change significantly but was changed considerably in PAS-fed granules. Complex organic PAS feed resulted in more complex bacterial populations that were not related to archea. The bacterial presence of a dominant phylotype, belonging to the family of Marinilabiliaceaeand specifically Alkaliflexus imshenetskiiwas evidenced. Members of Marinilabiliaceae are capable of degrading polymeric substances such as starch and gelatine. The dominant archeal species in the reactors was related to Methanosaeta harundinacea. Methanosaetahave been found to play a major role in granulation

    In Chapter 7the results of this research are discussed in a general context. Directions for further research are presented focussing on the increase in biomass activity and biomass retention in high salinity wastewaters by improving the adaptability of microbes and the anaerobic sludge granulation process.

    Capacitive technology for energy extraction from chemical potential differences
    Bastos Sales, B. - \ 2013
    Wageningen University. Promotor(en): Cees Buisman, co-promotor(en): Bert Hamelers. - S.l. : s.n. - ISBN 9789461737380 - 120
    capacitantie - bio-elektrische potentiaal - hernieuwbare energie - energiebronnen - zoutgehalte - elektrische kracht - temperatuur - capacitance - bioelectric potential - renewable energy - energy sources - salinity - electric power - temperature

    This thesis introduces the principle of Capacitive energy extraction based on Donnan Potential (CDP) to exploit salinity gradients. It also shows the fundamental characterization and improvements of CDP. An alternative application of this technology aimed at thermal gradients was tested.

    Chapter 2 introduces the principle and initial tests. The entropy increase of mixing two solutions of different salt concentrations can be harnessed to generate electrical energy. Worldwide, the potential of this resource, the controlled mixing of river and seawater, is enormous, but existing conversion technologies are still complex and expensive. Here we present a small-scale device that directly generates electrical power from the sequential flow of fresh and saline water, without the need of auxiliary processes or converters. The device consists of a sandwich of porous “supercapacitor” electrodes, ion-exchange membranes, and a spacer and can be further miniaturized or scaled-out. Our results demonstrate that alternating the flow of saline and fresh water through a capacitive cell allows direct autogeneration of voltage and current and consequently leads to power generation. Theoretical calculations aid in providing directions for further optimization of the properties of membranes and electrodes.

    In Chapter 3, traditional electrochemical techniques (galvanostatic charge–discharge and cyclic voltammetry) were used to investigate intrinsic properties of this open system. This study demonstrates the feasibility to characterize the capacitive behavior of the cell in low concentration (0.5 M). Presence of membranes, as well as the possibility of having the electrolyte flowing through the cell was investigated. In the studied cell, the presence of membranes showed a limitation by the anion exchange membrane at low current densities but no effect at high current densities. The flow rate did not influence the capacitance of the system either.

    Chapter 4uses again a stack of eight cells coupled in parallel to investigate the viability of this technology. An average power density of 0.055W/m2was obtained during the peak of the different cycles, though reasonable optimization suggests an expectation of 0.26W/m2at 6.2 A/m2. It was found that 83 ± 8% of the theoretical driving potential was obtained during the operating process. By studying the polarization curves during charging and discharging cycles, it was found that optimizing the feed fluid flow is currently among the most beneficial paths to make CDP a viable salinity difference power source. Another parallel route for increasing the efficiency is lowering the internal ohmic resistances of the cell by design modifications.

    A modification is proposed in Chapter 5, approaching the electrodes geometry that has a relevant impact on internal resistance and overall performance in CDP. In this work, we present the first effort to use wire-shaped electrodes and its suitability for improving CDP. Analytical evaluation and electrical measurements confirm a strong nonlinear decrease in internal resistance for distances between electrodes smaller than 3 mm. We also demonstrate that we get more power per material invested when compared to traditional flat plate designs. These findings show the advantages of this design for further development of CDP into a mature technology.

    Alternatively, in Chapter 6, we present a new principle for producing electricity from low temperature differences by using an affordable assembly combining ion exchange membranes and supercapacitor carbon electrodes. Our proposed design involves two isolated salty solutions, with equal concentration but different temperatures. The operation consists of an alternately and cyclic exposure of the electrodes to these electrolytes. This difference in temperature generates a thermomembrane potential that acts as a driving force for ionic adsorption/desorption cycles on the electrodes. Our simple system is interesting for exploiting the potential of low temperature waste heat. When two volumes with equal concentration have different temperatures, it is possible to immerse a pair of electrodes (anode and cathode) into the low temperature one and have ion adsorption. An electric current is then generated in the external circuit to achieve electro neutrality. After saturation, the same electrodes are immersed in the high T volume and then ions desorb from the electrodes and are released to the volume, leading to a reverse electric current in the external circuit compared to the first step. These experiments prove the principle and the direct dependence of the temperature gradient for energy extraction.

    Finally, Chapter 7discusses the internal energy losses identified and faced throughout this thesis. We summarize the solutions encountered for the major contributions hindering the CDP performance and give suggestions to further develop the technology.

    Ecological rehabilitation of Lac Bonaire by wise management of water and sediments
    Wosten, J.H.M. - \ 2013
    Wageningen : Alterra (Alterra-rapport 2448) - 40
    mangroves - zoutgehalte - sediment - vee - waterkwaliteit - waterbeheer - herstel - ecologisch herstel - bonaire - mangroves - salinity - sediment - livestock - water quality - water management - rehabilitation - ecological restoration - bonaire
    Lac Bonaire is confronted with a gradually decreasing open water area because mangrove is occupying this area. At the same time mangrove growth deteriorates at the back of the mangrove belt, the area of hyper saline flats gradually increases and sediment is deposited in the bay area. During a field visit, the most prominent problems are identified and concrete management actions are proposed for the ecological rehabilitation of Lac Bonaire.
    Modeling the effects of saline groundwater and irrigation water on root zone salinity and sodicity dynamics in agro-ecosystems
    Shah, S.H.H. - \ 2013
    Wageningen University. Promotor(en): Sjoerd van der Zee, co-promotor(en): R.W. Vervoort. - S.l. : s.n. - ISBN 9789461735256 - 201
    grondwater - zout water - modelleren - irrigatiewater - wortels - zoutgehalte - agro-ecosystemen - bodemfysica - bodemzoutgehalte - groundwater - saline water - modeling - irrigation water - roots - salinity - agroecosystems - soil physics - soil salinity

    Recent trends and future projections suggest that the need to produce more food and fibre for the world’ s expanding population will lead to an increase in the use of marginal-quality water and land resources (Bouwer, 2000; Gupta and Abrol, 2000; Wild, 2003). This is particularly relevant to less-developed, arid and semi-arid countries, in which problems of soil and water quality degradation are common (Qadir and Oster, 2004). The aim, therefore, should be to increase yield per unit of land rather than the area cultivated. More efforts are needed to improve productivity as more lands are becoming degraded. It is estimated that about 15% of the total land area of the world has been degraded by soil erosion and physical and chemical degradation, including soil salinization (Wild, 2003).

    The main sources of soil salinity and sodicity development are groundwater and irrigation water. In discharge areas of the landscape, water exits from groundwater to the soil surface bringing the salts dissolved in it. The driving force for upward movement of water and salts is evaporation from the soil plus plant transpiration. Salt accumulation is high when the water table depth is less than a threshold. However, this threshold depth may vary depending on soil hydraulic properties and climatic conditions. Groundwater associated salinity and sodicity affects around 350 X 104km2in the world (Szabolcs, 1989).

    In this thesis, the focus is to quantify and understand the salinity and sodicity dynamics, and the feedback on dynamics in groundwater dependent agro-ecosystems. First we have considered the impact of salt coming from groundwater on capillary fluxes and on the root zone water and salt dynamics. Groundwater can be a source of both water and salts in semi-arid areas, and therefore capillary pressure induced upward water flow may cause root zone salinization. To identify which conditions result in hazardous salt concentrations in the root zone, we combined the mass balance equations for salt and water, further assuming a Poisson-distributed daily rainfall and brackish groundwater quality. For the water fluxes (leaching, capillary upflow, and evapotranspiration), we account for osmotic effects of the dissolved salt mass using Van‘t Hoff’s law. Root zone salinity depends on salt transport via capillary flux and on evapotranspiration, which concentrates salt in the root zone. Both a wet climate and shallow groundwater lead to wetter root zone conditions, which in combination with periodic rainfall enhances salt removal by leaching. For wet climates, root zone salinity (concentrations) increases as groundwater is more shallow (larger groundwater influence). For dry climates, salinity increases as groundwater is deeper due to a drier root zone and less leaching. For intermediate climates, opposing effects can push the salt balance in either way. Root zone salinity increases almost linearly with groundwater salinity. With a simple analytical approximation, maximum concentrations can be related with the mean capillary flow rate, leaching rate, water saturation and groundwater salinity, for different soils, climates and groundwater depths.

    A Soil sodicity (quantified by ESP) model based on the soil salinity model (as discussed above) has been developed. For sodicity calculations, we have used the Gapon equation favored in salinity research. The simulation results show that soil salinity and sodicity development in groundwater driven agro-ecosystems play a major role in soil structure degradation. To identify which conditions can make soil sodic, we have modeled the coupled water, salt, and cation balances. The root zone salinity Cand sodicity ESPgradually change to their long term average values. These long term average values are independent of the cation exchange capacity CEC. The rate of change depends inversely on the size of the root zone reservoir, i.e., on root zone thickness for C, and additionally on CEC, for ESP.Soil type can have a large effect on both the rate of approach of the long term steady state salinity and sodicity, and on the long term levels, as it affects the incoming and out-going water and chemical fluxes. Considering two possible sources of salts, i.e., groundwater and irrigation water (here represented by rainfall), the long term salt concentration Cof the root zone corresponds well with a flux weighted average of infiltrating and upflowing salt mass divided by the average water drainage. In full analogy, the long term ESPcan be approximated very well for different groundwater depths and climates. A more refined analytical approximation, based on the analytical solution of the water balance of Vervoort and Van der Zee(2008), leads to a quite good approximation of long term salinity and sodicity, for different soils, groundwater depths, and climates.

    Modeling is an efficient tool to investigate water and solute movement in groundwater driven agro-ecosystems. However, in most available models (SWAP,MODFLOW/MT3D) continuing degradation of soil hydraulic properties as a result of rising Na+concentrations is ignored. Disregarding the soil hydraulic degradation due to sodicity level in some cases makes modeling water and solute movement within the soil profile questionable. We have translated the effects of soil salinity and sodicity into reduction in saturated hydraulic conductivity to quantify the feedback effects of reduction in saturated hydraulic conductivity on root zone fluxes, salinity, and sodicity under different groundwater depths and climates of Oenpelli and Tennant Creek Airport located in the North Territory of Australia. The reduction in saturated hydraulic conductivity due to salinity and sodicity (Ks(C,ESP))has been calculated by using the procedure developed by McNeal(1968). The significant feedback effects of Ks(C,ESP) on salt concentration and soil ESPdepend on many important parameters like groundwater depth, leaf area index, weather seasonality and non-seasonality, and soil type. Out of these important parameters, weather seasonality is the main driver that can develop significant feedback effects of Ks(C,ESP) onsalt concentration and soil ESP. Furthermore, Ks(C,ESP) although decreasing the capillary flux, leaching flux, and evapotranspiration, it increases the magnitude of runoff. Also when Ks(C,ESP)affects both capillary and leaching flux under seasonal rainfall, the feedback effects are significant compared to the partial feedback (Ks(C,ESP)affects only leaching flux, but not capillary flux).

    In the second theme of this thesis, we have focused on optimizing irrigation water between two farms under water scarcity and salinity regimes. In arid and semi-arid regions, irrigation water is scarce and often saline. To reduce negative effects on crop yields, the irrigated amounts must include water for leaching and therefore exceed evapotranspiration. The leachate (drainage) water returns to water sources such as rivers or groundwater aquifers and increases their level of salinity and the leaching requirement for irrigation water of any sequential user. We develop a sequential (upstream-downstream) model of irrigation that predicts crop yields and water consumption and tracks the water flow and level of salinity along a river dependent on irrigation management decisions. The model incorporates an agro-physical model of plant response to environmental conditions including feedbacks. For a system with limited water resources, the model examines the impacts of water scarcity, salinity and inefficient application on yields for specific crop, soil, and climate conditions. As a general pattern we find that, as salinity level and technical inefficiency increase, the system benefits when upstream farms use less water than is available to them, to provide downstream farms with more and better quality water. We compute the marginal value of water, i.e. the price water that would command on a market, for different levels of water scarcity, salinity and levels of water loss.

    In summary this thesis aims to understand theoretically how soil salinity and sodicity develop under different climates, groundwater depths, soil types, root zone thicknesses, and different groundwater salinities. The developed salinity sodicity model can be applied in potential salt affected areas to predict the long term salinity, sodicity trends. Furthermore, quantification of feedback effects of reduction in saturated hydraulic conductivity (Ks(C,ESP)) on root zone fluxes, salinity, and sodicity guide us towards better management of soil, vegetation, and irrigation/groundwater.

    Minder zout in brood goed mogelijk (interview met Anke Janssen)
    Rees, B. van; Janssen, A.M. - \ 2012
    Voedingsmiddelentechnologie 2012 (2012)14/15. - ISSN 0042-7934 - p. 24 - 25.
    brood- en bakkerijproductenindustrie - zout - natriumchloride - zoutgehalte - inname - voeding en gezondheid - sensorische evaluatie - bakery industry - salt - sodium chloride - salinity - ingestion - nutrition and health - sensory evaluation
    Terwijl minister Schippers de industrie het vuur aan de schenen legt om tot een stevige zoutreductie te komen, wisten de bakkers de afgelopen jaren het zoutgebruik al flink te beperken. Tijdens een workshop van Food & Nutrition Delta, RIVM, TNO en Wageningen UR bleek dat het zoutgebruik in brood nog verder is te verlagen. De meeste deelnemende bakkers zagen een verdere zoutreductie op termijn als een reële optie
    Minder zout in vleeswaren
    Meer, T. van der; Janssen, A.M. - \ 2012
    Eisma Voedingsmiddelenindustrie 2012 (2012)November. - p. 18 - 20.
    natriumchloride - vleeswaren - zout - reductie - zoutgehalte - houding van consumenten - smaak - voeding en gezondheid - sodium chloride - meat products - salt - reduction - salinity - consumer attitudes - taste - nutrition and health
    Het verlagen van zout in vleeswaren is lastig. Dit komt door de enorme variëteit aan producten en de verschillende rollen die zout hierin vervult. Dat bleek tijdens de workshop 'Zoutverlaging in vleeswaren. Het kan!' Minder zout is mogelijk. Nu de retail en de consument nog meekrijgen.
    Zoutgevoeligheid op de korrel genomen
    Hop, M.E.C.M. - \ 2012
    De Boomkwekerij 25 (2012)11. - ISSN 0923-2443 - p. 20 - 21.
    houtachtige planten - zouttolerantie - zoutgehalte - irrigatiewater - landbouwkundig onderzoek - woody plants - salt tolerance - salinity - irrigation water - agricultural research
    Zoutgevoeligheid is een niet zo bekende eigenschap van planten, die soms ineens belangrijk wordt. Denk maar aan vorig voorjaar, toen het zes weken droog was en het waterschap zilt water moest inlaten. Kwekers bij wie de bodem van het regenwaterbassin in zicht kwam, werden toen terecht ongerust.
    Zout, bloeddruk en hart- en vaatziekten
    Geleijnse, J.M. - \ 2011
    In: Hart- en vaatziekten in Nederland 2011 / Vaartjes, I., van Dis, I., Visseren, F.L.J., Bots, M.L., Den Haag : Hartstichting - ISBN 9789075131703 - p. 73 - 90.
    zout - reductie - hart- en vaatziekten - bloeddruk - hypertensie - natriumchloride - zoutgehalte - ziektepreventie - gezondheidsbevordering - salt - reduction - cardiovascular diseases - blood pressure - hypertension - sodium chloride - salinity - disease prevention - health promotion
    Dit hoofdstuk richt zich op het belang van zoutreductie in de Nederlandse bevolking, waarbij achtereenvolgens het verband met bloeddruk en hart- en vaatziekten, de dagelijkse zoutinname en bronnen van zout, de potentiële gezondheidswinst door zoutreductie en lopende initiatieven op het gebied van zoutreductie in de bevolking besproken worden.
    Abiotische kenmerken zoute habitattypen Natura 2000
    Jak, R.G. ; Dankers, N.M.J.A. ; Brinkman, A.G. ; Riegman, R. - \ 2011
    Den Helder : IMARES (Rapport / IMARES Wageningen UR C066/11) - 39
    natura 2000 - waterkwaliteit - habitats - eutrofiëring - zoutgehalte - inventarisaties - noordzee - natura 2000 - water quality - habitats - eutrophication - salinity - inventories - north sea
    Ten behoeve van profieldocumenten waarin habitattypen worden beschreven, zijn de biotische kenmerken van de zoute habitattypen in dit rapport nader gespecificeerd. Hiertoe zijn klassenindelingen voorgesteld voor de factoren voedselrijkdom, zoutgehalte, dynamiek en helderheid
    Quantification of Bacillus cereus stress responses
    Besten, H.M.W. den - \ 2010
    Wageningen University. Promotor(en): Marcel Zwietering; Tjakko Abee, co-promotor(en): Roy Moezelaar. - [S.l. : S.n. - ISBN 9789085857143 - 216
    bacillus cereus - stressreactie - zoutgehalte - zouttolerantie - hittetolerantie - adaptatie - weerstand - stresstolerantie - bacillus cereus - stress response - salinity - salt tolerance - heat tolerance - adaptation - resistance - stress tolerance
    The microbial stability and safety of minimally processed foods is controlled by a deliberate combination of preservation hurdles. However, this preservation strategy is challenged by the ability of spoilage bacteria and food-borne pathogens to adapt to stressing environments providing cell robustness. Bacillus cereus is a toxin-producing, spore-forming bacterium, and is able to survive minimal processing conditions. A quantitative approach was followed to gain insight in B. cereus’ stress adaptive behavior at population, individual cell and molecular level.
    B. cereus’ ability to adapt to salt stress and gain robustness towards subsequent heat challenge-stress exposure was quantified in detail using primary kinetics models. The adaptive salt stress response was influenced by the adaptation-stress concentration, the growth phase of the cells, strain diversity and the culturing temperature during adaptation-stress treatment. The nonlinear nature of the heat inactivation kinetics suggested heterogeneity within the population with respect to stress adaptive behavior. The direct-imaging-based Anopore technology was used to quantitatively describe the population heterogeneity of B. cereus upon mild and severe salt stress treatments and during low temperature growth. Fluorescent labeling of cells provided insights in the origin of stress-induced population heterogeneity. Then, to elucidate adaptive salt stress responses at molecular level, the genome-wide transcriptome profiles of mildly and severely salt-stressed cells were compared. Various transcriptome responses could be correlated to phenotypic features of salt stress-adapted cells. Comparison of the transcriptome profiles of salt stress-adapted cells to those that were exposed to mild heat, acid and oxidative stress, directed to potential cellular biomarkers for stress adaptation. The selected candidate-biomarkers  the transcriptional regulator B (activating general stress responses), catalases (removing reactive oxygen species), and chaperones and proteases (maintaining protein quality)  were measured upon adaptation-stress treatment at transcript, protein and/or activity level, and their induction was correlated to adaptation-stress induced robustness towards challenge-stress. Various candidate-biomarkers were suitable to predict the robustness level of adaptation-stress pretreated cells towards challenge-stress, and are therefore potential predictive cellular indicators for adaptation-stress induced robustness. The predictive potential of transcripts differed from that of proteins and activity level, underlining the significance to evaluate predictive potential of candidate-biomarkers at different functional cell levels. This quantitative understanding of B. cereus’ stress adaptive behavior provides mechanistic insights and opens up avenues to come to a mechanism-based approach for designing mild preservation strategies.
    Watergift sturen met sensoren voor vochtgehalte en EC bij containerteelten (FLOW-AID)
    Balendonck, J. ; Pardossi, A. ; Incrocci, L. ; Marzialetti, P. - \ 2010
    irrigatie - zoutgehalte - waterbeheer - emissie - potcultuur - irrigation - salinity - water management - emission - pot culture
    Poster met onderzoeksinformatie: doelstellingen, methode, resultaten en toepassing.
    Extracellular Polymeric Substances (EPS) in Upflow Anaerobic Sludge Blanket (UASB) Reactors Operated under High Salinity Conditions
    Ismail, S. ; Parra, C.J. de la; Temmink, B.G. ; Lier, J.B. van - \ 2010
    Water Research 44 (2010)6. - ISSN 0043-1354 - p. 1909 - 1917.
    afvalwaterbehandeling - zoutgehalte - kweekmedia - deeltjesgrootteverdeling - anaërobe afbraak - korrelslib - waste water treatment - salinity - culture media - particle size distribution - anaerobic digestion - granular sludge - activated-sludge - waste-water - microbial granules - calcium - performance - stability - strength - impact - growth
    Considering the importance of stable and well–functioning granular sludge in anaerobic high rate reactors, a series of experiments were conducted to determine the production and composition of EPS in high sodium concentrations wastewaters pertaining to anaerobic granule properties. The UASB reactors were fed with either fully acidified substrate (FAS) consisting of an acetate medium (reactor R1) or partly acidified substrate (PAS) consisting of acetate, gelatine and starch medium (reactors R2, R3, and R4). For EPS extraction, the cation exchange resin (CER) method was used. Strength and particle size distribution were determined by assessing the formation of fines sludge under conditions of high shear rate and by laser diffraction, respectively. Batch tests were performed in 0.25 L bottles to study Ca2+ leaching from anaerobic granular sludge when incubated in 20 g Na+/L in absence of feeding for 30 days. Results show a steady increase in the bulk liquid Ca2+ concentration during the incubation period. UASB reactor results show that the amounts of extracted proteins were higher from reactors R2 and R3, fed with PAS compared to the sludge samples from reactor R1, fed with FAS. Strikingly, the amount of extracted proteins also increased for all reactor sludges, irrespective the Na+ concentration applied in the feed, i.e. 10 or 20 gNa+/L. PAS–grown granular sludges showed an important increase in particle size during the operation of the UASB reactors. Results also show that, addition of 1 gCa2+/L to the high salinity wastewater increases the granules strength
    Blue energy: electricity production from salinity gradients by reverse electrodialysis
    Post, J.W. - \ 2009
    Wageningen University. Promotor(en): Cees Buisman, co-promotor(en): Bert Hamelers. - [S.l. : S.n. - ISBN 9789085855101 - 222
    zout water - zoet water - vermenging - osmotische druk - zoutgehalte - elektrische energie - energieterugwinning - elektrodialyse - osmose - afsluitdijk - saline water - fresh water - mixing - osmotic pressure - salinity - electrical energy - energy recovery - electrodialysis - osmosis - afsluitdijk
    Energie opwekken op grote schaal uit het mengen van zoet en zout water is technisch en praktisch mogelijk. Wereldwijd is de potentie van deze schone energie – ‘blauwe stroom’ – zeer groot. Ook in Nederland kunnen over minimaal tien jaar blauwe stroomcentrales worden geplaatst, onder meer aan de Afsluitdijk, die samen de helft van de huidige elektriciteitsbehoefte kunnen dekken. Het principe dat stroom kan worden opgewekt uit het mengen van zoet en zout water, door gebruik te maken van het verschil in lading, is al meer dan 100 jaar bekend en in de vijftiger jaren van de vorige in een laboratorium voor het eerst beproefd. Er zijn twee methoden voor de opwekking van blauwe stroom: ‘onderdrukte osmose’ en ‘omgekeerde dialyse’. In zijn onderzoek heeft Post zich met name gericht op de laatste methode omdat die aantrekkelijker is voor de opwekking van energie uit zee- en rivierwater. De Afsluitdijk is een ideale plaats volgens Post vanwege de vrij abrupte scheiding van zout en zoet water. Bovendien is de Afsluitdijk een zeer geschikte locatie voor een noodzakelijke praktijktest op grote schaal
    Drain for gain : making water management worth its salt : subsurface drainage practices in irrigated agriculture in semi-arid and arid regions
    Ritzema, H.P. - \ 2009
    Wageningen University. Promotor(en): E. Schultz, co-promotor(en): Wim Cofino. - [S.l.] : S.n. - ISBN 9789085853145 - 208
    drainage - drainagesystemen - irrigatie - zoutgehalte - waterverzadiging - drainage - drainage systems - irrigation - salinity - waterlogging
    De geïrrigeerde landbouw heeft te kampen met verzilting en/of wateroverlast, met als gevolg dat er jaarlijks ongeveer een half miljoen hectare landbouwgrond uit productie wordt genomen. In deze studie is de rol van de drainage voor de geïrrigeerde landbouw in de aride - en semi-aride gebieden geanalyseerd en zijn aanbevelingen geformuleerd om de negatieve tendens van wateroverlast en verzilting te keren. Hoewel de bestaande drainagesystemen technisch voldoen en kostendekkend zijn, blijft de ontwikkeling van drainage achter bij de ontwikkeling van de irrigatie. De belangrijkste oorzaak is dat de systemen zijn ontworpen en aangelegd door de overheid, waarbij te weinig rekening wordt gehouden met de belangen van de boeren en de lokale omstandigheden. Daarnaast ligt bij de aanleg het accent vooral op de technische aspecten terwijl de organisatorische aspecten ondergeschikt blijven. Er zijn een drietal aanbevelingen geformuleerd om de rol van drainage in de geïrrigeerde landbouw beter tot zijn recht te laten komen: (i) een betere balans tussen “top-down” en “bottom-up” (ii) van standaardisatie naar een meer flexibele aanpak en (iii) focus op capacity building.
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