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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    Foam properties of proteins, low molecular weight surfactants and their complexes
    Lech, F.J. - \ 2016
    Wageningen University. Promotor(en): Harry Gruppen; Peter Wierenga; Marcel Meinders. - Wageningen : Wageningen University - ISBN 9789462576247 - 122
    surfactants - proteins - bovine serum albumin - beta-lactoglobulin - lysozyme - foams - chemical properties - stability - mixtures - food chemistry - oppervlaktespanningsverlagende stoffen - eiwitten - runderserumalbumine - bèta-lactoglobuline - lysozym - schuim - chemische eigenschappen - stabiliteit - mengsels - voedselchemie

    This thesis shows the effects that the addition of low molecular weight surfactants (LWMS) to proteins has on the foam stability of the mixture. For this, the bulk, interfacial, thin liquid films and foam properties are determined for different protein-LWMS mixtures at different molar ratios (MR). It was shown that the MR as well as the charge of the protein and LMWS determine the foam stability of the mixtures. For all mixtures it was found that the proteins have a select number of high affinity binding sites. So, the concentration of free LMWS in the solution is 0 until a critical MR (MRcr), at which all high affinity binding sites are saturated. Above this MRcr, part of the LMWS binds to low affinity binding sites of the proteins. The low affinity binding sites have a binding ratio < 1, which determines the concentration of bound and free LMWS. For similarly charged protein-LMWS mixtures (i.e. b-lactoglobulin (BLG) and sodium dodecyl sulphate (SDS) and bovine serum albumin (BSA) and SDS at pH 7) the foam stability typically decreases from the foam stability of the pure protein solution (MR 0) until MRcr is reached. At MR > MRcr the foam stability is dominated by the amount of free LMWS. For oppositely charged protein-LMWS mixtures, the binding of the LMWS to the proteins can be described in a similar way, although the number of high affinity sites and low affinity binding ratio are different. There is also a regime of MRs in which the protein-LMWS complexes form large aggregates. These aggregates were in some cases found to increase foam stability (lysozyme (LYS) and SDS and BLG-SDS at pH 3), while in another case (BLG and cetyltrimethylammonium bromide (CTAB)) they lead to decreased foam stability. Still, in all cases it was found that above MRD the aggregates dissociate and the foam stability becomes dominated by free surfactants, equivalent to what was observed for similarly charged protein-LMWS mixtures.

    A multi-scale model was developed to describe the stability of thin liquid films in terms of rupture time and thickness. Initially, the model was used to predict the stability of surfactant free films of water and electrolyte solutions. Later, it was used to predict the foam stability in LYS-SDS mixtures. For that purpose, the model was combined with a foam drainage model to provide theoretical estimations of foam stability. This model is the basis to understand coalescence of bubbles in foam. Finally, the concept of the critical MRs and the free LMWS was introduced. Using this, the foam properties of protein-LMWS mixtures can partly be predicted by relative charge of the components and the binding to both high and low affinity binding sites.

    Baseline survey B11-5 on the German Continental Shelf
    Glorius, S.T. ; Weide, B.E. van der; Kaag, N.H.B.M. - \ 2013
    Den Helder : IMARES (Rapport / IMARES Wageningen UR C098/13) - 45
    waterbodems - noordzee - chemische eigenschappen - fysische eigenschappen - biologische eigenschappen - sediment - textuur - inventarisaties - water bottoms - north sea - chemical properties - physical properties - biological properties - sediment - texture - inventories
    A consortium, consisting of Wintershall Holding GmbH, GdF Suez, RWE Dea and EWE AG, is planning an exploration well in block B11-5, located within the Doggerbank (N2000 area). In order to assess any effect from this activity on the biological, physical and chemical properties of the seafloor Wintershall Noordzee BV asked IMARES to perform a baseline study prior to the drilling activities. In this baseline study the following environmental elements are included; seafloor texture and presence of any structures (including stones and boulders), the physical (grain size and organic content), chemical (oil and metal content) and biological (abundance and structure of benthic species) properties of the sediment. At 29 stations located at different angles and distances of the drill site, sediment samples were taken and video recordings of the seafloor made. In an area of 2000 x 2000 m around the centre, side scan sonar footage were made as well.
    Abiotische randvoorwaarden en natuurdoelen in kunstmatige wateren dl. 3 Matige grote, ondiepe laagveenplassen
    Keizer-Vlek, H.E. ; Lange, H.J. de; Verdonschot, P.F.M. - \ 2010
    Wageningen : Alterra (Alterra-rapport 2089) - 88
    laagveengebieden - plassen - fauna - vissen - waterplanten - oppervlaktewater - biologische indicatoren - zoetwaterecologie - habitats - chemische eigenschappen - waterkwaliteit - nederland - kwaliteit - macrofauna - kaderrichtlijn water - natura 2000 - abiotiek - fens - ponds - fauna - fishes - aquatic plants - surface water - biological indicators - freshwater ecology - habitats - chemical properties - water quality - netherlands - quality - macrofauna - water framework directive - natura 2000 - abiotic conditions
    Het doel van deze studie is het gekwantificeerd invullen van de abiotische randvoorwaarden behorende bij de (Zeer) Goede Ecologische Toestand ((Z)GET) van het KRW type M27 ‘Matig grote, ondiepe laagveenplassen’. Meetgegevens van de twaalf ‘best beschikbare’ plassen in Nederland zijn voor dit doel geanalyseerd. De resultaten geven aan dat de biologische kwaliteitselementen in geen van de twaalf plassen voldoen aan de GET. De relatief slechte ecologische toestand van de plassen wordt onder andere veroorzaakt door hoge concentraties totaal-stikstof en totaal-fosfor, beperkt doorzicht en een hoge pH. Deze abiotische variabelen voldoen in bijna alle gevallen niet aan de GET-norm. De resultaten van het onderzoek impliceren dat de GET-norm/KRW referentie¬waarde(n) voor de abiotische variabelen EGV, chloride, ammonium en sulfaat naar beneden moeten worden bijgesteld om de GET van matig grote, ondiepe laagveenplassen te kunnen garanderen. Voor deze abiotische variabelen moet echter eerst nog worden bepaald of hogere concentraties dan vastgesteld in dit onderzoek leiden tot een verminderde ecologische toestand. Verder zal meer inzicht moeten komen in de voor de macrofauna- en waterplantengemeenschap sturende factoren door middel van experimenteel onderzoek. Hiervoor is naast informatie over fysisch-chemische milieuvariabelen ook informatie nodig over hydro¬morfologische milieuvariabelen. Tot slot is niet mogelijk gebleken om op basis van deze studie een eenduidige relatie te leggen tussen de abiotische randvoorwaarden noodzakelijk voor de realisatie van de GET in matig grote, ondiepe laagveenplassen (KRW) en de abiotische randvoorwaarden noodzakelijk voor de realisatie van aquatische habitattypen (VHR). Wel is vastgesteld dat habitattype 3140 niet voorkomt in de onderzochte plassen, terwijl zes van de twaalf onderzochte plassen liggen in een Natura 2000-gebied met een doelstelling voor habitattype 3140.
    Influence of pectin characteristics on complexation with ß-lactoglobulin
    Sperber, B.L.H.M. - \ 2010
    Wageningen University. Promotor(en): Fons Voragen; Willem Norde, co-promotor(en): Henk Schols. - [S.l. : S.n. - ISBN 9789085858355 - 174
    pectinen - bèta-lactoglobuline - ladingskenmerken - fysische eigenschappen - chemische eigenschappen - binding (scheikundig) - pectins - beta-lactoglobulin - charge characteristics - physical properties - chemical properties - bonding
    Pectin and proteins are both common food constituents. The type of pectin that forms complexes with protein is known to be of great influence on the structure and stability of liquid foods. Therefore, the aim of this thesis is to investigate the influence of the overall charge and local charge density of pectin on the formation of soluble complexes with β-lactoglobulin (β-lg).
    Combination of state diagrams and binding isotherms shows that a high local charge density of pectin is a prerequisite to form soluble complexes with β-lg at higher ionic strength. A high overall charge of pectin results in the close proximity of the GalA blocks. Therefore, β-Lg neighbours bind close together on pectin with a high overall charge, which leads to lateral repulsion and hence, maxima in the binding constant and the pH where insoluble complexes form with increasing ionic strength.
    The formation of soluble complexes has an enthalpic driving force from electrostatic attraction and an entropic driving force from the release of small counterions from the electric double layer and water molecules from hydrophobic surroundings. A high local charge density, at low ionic strength results in complex formation dominated by an enthalpic driving force. A low local charge density gives a more even distribution between enthalpic and entropic contributions. An increase in ionic strength decreases the enthalpic contribution, with a relative increase in the entropic contribution, supporting the idea of water release from hydrophobic surroundings.
    Adsorption from β-lg–pectin mixtures to a hydrophobic surface leads to low adsorption rates due to a low concentration of free protein. Sequential adsorption of β-lg and pectin shows that low overall charge pectin protrudes more into the solution than high overall charge pectin, resulting in a more negative ζ-potential for low overall charge pectin. After sequential adsorption, β-lg is most stable against wash-out with a terminal pectin layer.
    Coffee brew melanoidins Structural and Functional Properties of Brown-Colored Coffee Compounds
    Bekedam, E.K. - \ 2008
    Wageningen University. Promotor(en): Gerrit Smit; Tiny van Boekel, co-promotor(en): Henk Schols. - [S.l.] : S.n. - ISBN 9789085049517 - 168
    koffie - kleurstoffen in voedsel - roosteren - chemische eigenschappen - coffee - food colourants - toasting - chemical properties
    The aim of the work presented in this thesis was the identification of structural and functional properties of coffee brew melanoidins, and their formation mechanisms, that are formed upon roasting of coffee beans.
    H-Bond stabilized columnar discotic liquid crystals
    Paraschiv, I. - \ 2007
    Wageningen University. Promotor(en): Ernst Sudhölter, co-promotor(en): Ton Marcelis; Han Zuilhof. - [S.l.] : S.n. - ISBN 9789085045588 - 150
    chemische eigenschappen - synthese - vloeibare kristallen - organische scheikunde - chemical properties - synthesis - liquid crystals - organic chemistry
    Since 1977, more than 2300 publications on discotic (disk-like) liquid crystalline materials have appeared. Discotic liquid crystals, which usually consist of polyaromatic molecules surrounded by long peripheral alkyl tails, can form liquid crystalline mesophases in a wide temperature range. Within these mesophases, the molecules self-assemble in large columnar stacks viap-stacking interactions between the aromatic cores. These assemblies can provide an efficient charge transport pathway, as indicated by their informal designation as " molecular-wires ". As a result, they nowadays attract significant interest for optoelectronic applications. Several possible applications where discotic liquid crystals could be used are field effect transistors (FETs), light emitting diodes (LEDs) and photovoltaic solar cells.

    In all the discotic materials described so far, the molecules inside the columns, can still rotate around the columnar axis, slide out of the columns or oscillate within the columnar stack. This represents a limitation of their applicability as " molecular-wires ". Therefore, in this research, an additional stabilization of columnar discotic mesophases was envisaged in order to increase their organization, without the frequently concomitant loss of processability that would result from extensions of the aromatic core. The research described in this thesis focuses on the stabilization of columnar mesophases by highly tunable (i.e. controlled) H-bonding interactions, without enlarging the aromatic cores and thus maintaining their processability. Functional H-bonding groups, such as urea, amide, thiourea or 1,3,5-benzenetrisamide, have been used in this work, in order to create a H-bonding network parallel to the columnar axis, alongside the existing π-π stacking interactions between the disk-like molecules.

    In Chapter 1 an overview of the different types of liquid crystalline phases is presented, with emphasis on the organization of columnar discotic mesophases. Since this work focuses on the hydrogen bond stabilization of the triphenylene-based discotic liquid crystals, the most important synthetic approaches towards these materials are discussed. Several of these methods were applied to prepare the materials investigated in Chapters 2 to 5. Besides the synthetic aspect, several characterization techniques, which are normally used to investigate the properties of the liquid crystal materials, are shortly discussed.

    Chapter 2deals withthe synthesis and thermotropic properties ofa series of hexaalkoxytriphenylenes that contain one amide, urea or thiourea group in one of their alkoxy tails, as H-bond forming group. The biphenyl route turns out to be the best with respect to yields and versatility, as compared to other methods. The optical polarization microscopy, differential scanning calorimetry and X-ray studies show that the intermolecular hydrogen bonding has a negative influence on the formation and stability of the columnar liquid crystalline phases: The stronger the hydrogen bonding, the more the liquid crystallinity is suppressed. This is probably due to disturbance of thep-pstacking of the triphenylene disks and a lower flexibility of the alkyl tails. So far, the urea and amide containing triphenylene derivatives do not exhibit liquid crystalline properties, probably because an H-bond stabilization of the crystalline state is obtained. However, several thiourea derivatives show columnar hexagonal (Col h ) mesophases, because in these compounds thep-pinteractions are more important than the relatively weak thiourea hydrogen bonding.

    Because in the columnar mesophases the motions of the aromatic core and the alkyl tails are strongly correlated, the length of the alkyl chains, which surround the disk-like aromatic cores, is an important factor that determines the stability of the columns. Since in the previous chapter long substituents carrying an urea, amide or thiourea group have been used, a complementary study, with focus on the synthesis and phase behavior of unsymmetrically substituted hexaalkoxytriphenylenes, is described in Chapter3. Inthis study, one of the hexyloxy chains in hexahexyloxytriphenylene (HAT6) is replaced by either a shorter or longer chain. In the series HAT-(OC 6 H 13 ) 5 -(OCn H 2 n +1 ), with n ranging from 2 to 18, the compounds with n³13 are not liquid crystalline anymore. For all compounds with n£12, Col h phases are found. Furthermore, X-ray investigations show that the intercolumnar distance gradually increases from 20.19 Å to 22.03 Å, with increasing n , while a small odd-even effect on the increase of the intercolumn distance with n is observed. This odd-even effect is also found in the change of ΔH of isotropization with n . The interdisk distance remains constant (3.6 Å).

    Since the stabilization of the columnar mesophase by H-bonding interactions still remains an unsolved issue, Chapter 4 describes a 1,3,5-benzenetrisamide with three pendant hexaalkoxytriphenylene groups, as a new approach for the intermolecular H-bond-stabilization of columnar discotic liquid crystalline materials. This compound forms a columnar hexagonal plastic (Col hp ) discotic phase with a clearing point at 208°C. Surprisingly, the material does not crystallize on cooling from the isotropic phase, even after annealing for a few days at room temperature, but goes into a glassy state due to the enforced H-bonding network formed between the benzenetrisamide units. Modeling studies show that the central 1,3,5-benzenetrisamide cores are rotated 60°with respect to each other, which makes the adjacent triphenylene moieties to stack with a small 15°rotation. This small rotation observed between the adjacent triphenylene units plays a key role, since for such a rotation ~85 % of the maximum charge transfer integral is achieved. This result is correlated to the very high charge carrier mobility of 0.12 cm 2 V -1 s -1 at 180°C, found for this particular compound. This value is the second highest ever reported for liquid crystalline triphenylene systems. This is a first proof for the intermolecular H-bonding stabilization of the columnar organization of triphenylene moieties, without loosing the ease of processing provided by the liquid crystalline phase.

    Since the modeling discussed in the previous chapter suggests that the conformation of the butyl spacer, which is used for that particular compound, dictates thep-poverlap of the triphenylene units within the liquid crystal phase, a new series of 1,3,5-benzenetrisamide derivativeswith threehexaalkoxytriphenylene pendant groups is prepared and their properties discussed in Chapter5. Inthis case, the length of the spacer, as well as the size of the ortho -substituent at the triphenylene core is varied. Taking into account these modifications, all these materials show liquid crystalline behavior with high isotropization points (170-200°C). Different columnar hexagonal phases have been identified going from a columnar hexagonal plastic (Col hp ) phase, when using a butyl spacer, with a shorter butyl ortho -substituent of the triphenylene core, to a columnar hexagonal disordered (Col hd ) phase, when a pentyl spacer is used and a hexyl ortho -substituent is present on the triphenylene groups.Achiral 1,3,5-benzenetrisamide was shown to form columnar stacks with a single helical organization, both in an apolar solvent and in a film, as found by circular dichroism studies. By using pulse-radiolysis time-resolved microwave conductivity, charge carrier mobilities as high as 0.25 cm 2 V -1 s -1 are found for the liquid crystalline phase (Col h ) of this chiral derivative. This mobility is twice the highest value ever reported for triphenylene-based liquid crystalline materials, approaching mobilities found for hexabenzocoronene-based liquid crystals, with a much larger aromatic core. This is a substantial improvement regarding the stabilization of disk-like molecules within their liquid crystal phase, without expanding the aromatic cores, but by tuning the H-bonding and the length of the spacer.
    Studies on the intra- and intermolecular distributions of substituents in commercial pectins
    Guillotin, S.E. - \ 2005
    Wageningen University. Promotor(en): Fons Voragen, co-promotor(en): Henk Schols. - [S.l.] : S.n. - ISBN 9789085042655 - 155
    pectinen - chemische eigenschappen - fysische eigenschappen - voedseladditieven - pectins - chemical properties - physical properties - food additives
    Commercial pectins are mainly used for the gelling, thickening and stabilizing properties in food products. The different physical properties of pectins strongly depend on the galacturonic acid level and the level of methyl-esterification as well as on the molecular weight distribution. However, the conventional chemical analysis of the pectins does not always show differences between pectins while they behave differently. Two highly methyl-esterified pectins with similar chemical characteristics but different reactivity towards calcium were analysed. They were found to be a mixture of pectic populations differing in the degree of methyl-esterification as well as in the distribution of these methyl-esters. Amidated pectins with similar chemical features but different calcium sensitivity were also found to be a mixture of different pectic populations. Even for pectins having a similar degree of substitution, the ratio of amide groups versus methyl-esters varied significantly. In addition, the distribution of these substituents was found to differ.
    Effects of different treatments of cattle slurry manure on water-extractable phosphorus
    Chapuis-Lardy, L. ; Temminghoff, E.J.M. ; Goede, R.G.M. de - \ 2003
    Netherlands Journal of Agricultural Science 51 (2003)1-2. - ISSN 0028-2928 - p. 91 - 102.
    rundveemest - rundveedrijfmest - behandeling - fosfor - toevoegingen - oplosbaarheid - chemische eigenschappen - waterverontreiniging - mestverwerking - cattle manure - cattle slurry - treatment - phosphorus - chemical properties - additives - solubility - water pollution - manure treatment - runoff phosphorus - animal manure - nitrogen - soil - netherlands - strategies - management - excretion - recovery - losses
    Cattle slurry manure applied to land increases the risk of phosphorus (P) movement to surface waters, which may lead to eutrophication. The water-extractable fraction of P in slurry manure is correlated with P concentration in runoff from soils amended with slurry smanure, and thus is an effective indicator of environmental P loss. We evaluated the water-extractable P (WEP) and readily soluble P (RSP; i.e., P extractable in a single water extract) contents in slurry manure from nine farms. On some farms, the additive Euromestmix® (MX) is used to complex N-compounds in the slurry manure, but the effect of MX on P in the slurry manure is not known. We also focused on methodological factors affecting the measurement of P in slurry manure. Drying the slurry manure before analysis decreased WEP and RSP contents. Dilution of slurry manure by varying the dry matter-to-distilled water ratio increased the water-extractable fractions. Analysis of calcium and magnesium contents in water showed that these minerals are involved in the release of P in water. Total RSP content of slurry manures from the nine farms ranged from 1.83 to 4.06 mg P per g dry matter. A substantial portion of total P in the slurry manure occurred in the water-extractable (46–71%) and the readily soluble P fractions (24–51%). The addition of MX tended to decrease the readily soluble inorganic P content of slurry manures.
    Ambergris fragrance compounds from labdanolic acid and larixol
    Bolster, M.G. - \ 2002
    Wageningen University. Promotor(en): Æ. de Groot; B.J.M. Jansen. - S.l. : S.n. - ISBN 9789058086662 - 214
    diterpenen - welriekendheid - aromatische verbindingen - biosynthese - chemische eigenschappen - oxidatie - biologische eigenschappen - diterpenes - fragrance - aromatic compounds - biosynthesis - chemical properties - oxidation - biological properties

    Since ancient times, ambergris has been one of the most highly valued perfumery materials. Ambergris is a metabolic product of the spermwhale ( Physeter macrocephalus L.), which accumulates as concretions in the gut. (-)-AmbroxÒ, the commercially most important constituent of natural ambergris, is recognized as the prototype of all ambergris odorants. For this reason, various synthetic routes to (-)-AmbroxÒand its racemate have been developed, preferrably starting from cheap, abundantly available natural labdanes. Sclareol is nowadays the industrially used starting material for the preparation of (-)-AmbroxÒ. Labdanolic acid and larixol are both easily and abundantly available from labdanum gum of Cistus ladaniferus L. ("Rock-rose") and turpentine of the Larix decidua , respectively, but have found little use as starting material in syntheses of Ambergris odour compounds. In this thesis new chemistry in that field is described.

    From the acetate of labdanolic acid short procedures are developed for the synthesis of AmbroxÒ. Also a standard method has been developed for the oxidation of the side chain of several labdanes. Generally good to high yields of single products can be obtained using anhydrous potassium permanganate in the presence of a phase-transfer catalyst. In this way larixol can be converted into suitable synthons for the synthesis of several Ambrox-like compounds. 6a-hydroxy Ambrox can be considered to be a key intermediate in such syntheses and conversions of larixol into this intermediate are described. From 6a-hydroxy Ambrox a number of simple Ambrox derivatives have been synthesized. By heating with acid a mixture was formed consisting ofD5- andD6-Ambroxene, which both are pleasant smelling.D5-Ambroxene was produced in a more selective way by elimination of methanesulfonic acid from the corresponding mesylate of 6a-hydroxy Ambrox. A selective synthesis ofD6-Ambroxene proved to be more difficult and laborious. Several approaches were investigated, and ultimately the one via ringclosure of an allylic alcohol proved to give good results. It turned out that this new approach could not be extended to the selective synthesis of six-membered cyclic ethers, e.g.D6-Ambra oxides. In the latter case, elimination of the 6b-hydroxyl group to the correspondingD6,8-dienes was observed as the major reaction.

    Measuring acid volatile sulphide in floodplain lake sediments: effect of reaction time, sample size and aeration
    Griethuysen, C. van; Gillissen, F. ; Koelmans, A.A. - \ 2002
    Chemosphere 47 (2002). - ISSN 0045-6535 - p. 395 - 400.
    bodemchemie - chemische eigenschappen - sulfiden - analyse - laboratoriumdiagnose - sediment - meren - waterbodems - soil chemistry - sediment - lakes - chemical properties - sulfides - analysis - laboratory diagnosis - water bottoms
    Zelfcontrole stikstofgit levert besparingen op
    Brouwer, J. ; Derkx, M.P.M. - \ 2001
    De Boomkwekerij 14 (2001)18. - ISSN 0923-2443 - p. 18 - 19.
    bosbouw - plantenvoeding - stikstof - stikstofmeststoffen - mestbehoeftebepaling - analyse - chemische eigenschappen - bodem - fraxinus excelsior - bos- en haagplantsoen - forestry - plant nutrition - nitrogen - nitrogen fertilizers - fertilizer requirement determination - analysis - chemical properties - soil - woody nursery stock
    Stikstofbemestingsadvies voor bos- en haagplantsoen: onderdeel van het project 'Innovatieve teelt van bos- en haagplantsoen'. Gegevens in bijgaande tabel en figuren: 1) N-min metingen in de bouwvoor bij verplante Fraxinus excelsior; 2) Restwaarden N-min in bodem (0-90 cm) bij verplante Fraxinus excelsior; 3) Maatverdeling bij verplante Fraxinus excelsior na drie methoden N-bemesting
    Mineralenbalans en grondwaterkwaliteit bij deelnemers Bioveem
    Snijders, P. ; Everts, H. - \ 2000
    Praktijkonderzoek Rundvee, Schapen en Paarden. Praktijkonderzoek 13 (2000)6. - ISSN 1386-8470 - p. 31 - 33.
    melkveehouderij - biologische landbouw - zandgronden - mineralen - boekhouding - grondwater - chemische eigenschappen - nitraten - dairy farming - organic farming - sandy soils - minerals - accounting - groundwater - chemical properties - nitrates
    Het nitraatgehalte in het grondwater voldoet aan de EU norm van 50 mg per l. Ook het stikstof en fosfaat overschot op de mineralenbalans voldoet op de meeste bedrijven.
    Hormoonontregelaars in water opsporen met biologische effectmetingen
    Murk, A.J. ; Belfroid, A. ; Vethaak, D. - \ 2000
    H2O : tijdschrift voor watervoorziening en afvalwaterbehandeling 33 (2000)1. - ISSN 0166-8439 - p. 20 - 23.
    toxische stoffen - hormonen - geslachtshormonen - oestrogenen - synthetische oestrogenen - oestrogene eigenschappen - waterverontreiniging - waterkwaliteit - oppervlaktewater - afvalwater - rioolwater - samenstelling - eigenschappen - chemische eigenschappen - chemische analyse - tests - testen - assays - in vitro - Nederland - xenobiotica - toxic substances - hormones - sex hormones - oestrogens - synthetic oestrogens - oestrogenic properties - water pollution - water quality - surface water - waste water - sewage - composition - properties - chemical properties - chemical analysis - tests - testing - assays - in vitro - Netherlands - xenobiotics
    Uitleg over de pricipes van verschillende in-vitro testen gebruikt voor het bepalen van de oestrogene potentie van monsters oppervlaktewater en afvalwater, en enige resultaten voor verschillende locaties in Nederland
    Dioxinetest RIKILT heeft zijn waarde bewezen
    Mengelers, M.J.B. ; Hoogenboom, L.A.P. ; Traag, W.A. - \ 1999
    Voedingsmiddelentechnologie 4 (1999)23. - ISSN 0042-7934 - p. 13 - 16.
    dioxinen - heterocyclische zuurstofverbindingen - analytische methoden - testen - controle - kwalitatieve analyse - toxische stoffen - chemische samenstelling - chemische eigenschappen - voedselbesmetting - voedingsmiddelen - voedselindustrie - voedseltechnologie - analytische scheikunde - dioxins - heterocyclic oxygen compounds - analytical methods - testing - control - qualitative analysis - toxic substances - chemical composition - chemical properties - food contamination - foods - food industry - food technology - analytical chemistry
    Sinds 1992 werkt het Rikilt in samenwerking met de Wageningen Universiteit aan een biologische methode voor het screenen van agrarische producten op dioxinen en dioxineachtige PCB's. De methode is gevalideerd voor het aantonen van dioxinen in melk en in citruspulp uit Brazilie
    The use of upscaling procedures in the application of soil acidification models at different spatial scales
    Vries, W. de; Kros, J. ; Salm, C. van der; Groenenberg, J.E. ; Reinds, G.J. - \ 1998
    Nutrient Cycling in Agroecosystems 50 (1998)1-3. - ISSN 1385-1314 - p. 223 - 236.
    zure gronden - kattekleigronden - neerslag - chemische eigenschappen - zuurgraad - zure regen - modellen - onderzoek - geostatistiek - acid soils - acid sulfate soils - precipitation - chemical properties - acidity - acid rain - models - research - geostatistics
    Different soil acidification models have been developed for use on different scales, i.e., NUCSAM for the local scale, RESAM for the regional (national) scale and SMART for the continental scale. This paper focuses on the uncertainties associated with scale transfer by a simpler model description by (i) temporal aggregation of process descriptions, (ii) neglection of processes associated with vertical aggregation of soil layers and (iii) the use of less detailed formulations of processes (process aggregation) and by spatial aggregation of input data. Results obtained for simulations in acid (sandy) soils indicate that (i) temporal aggregation and process aggregation have a limited impact on the long-term (decades) annual response of soil solution chemistry to atmospheric deposition, (ii) vertical aggregation mainly affects predictions of solutes which show a strong concentration gradient with depth and (iii) spatial aggregation hardly affects the average output for a given forest/soil combination. However, ignoring the variability in input parameters, largely affects the frequency distribution of model outputs in a region. Results imply that model simplification is an adequate step in the upscaling of modelling results from a local to a regional scale.
    Assessment of weathering rates in Dutch loess and river-clay soils at pH 3.5, using laboratory experiments
    Salm, C. van der; Köhlenberg, L. ; Vries, W. de - \ 1998
    Geoderma 85 (1998). - ISSN 0016-7061 - p. 41 - 62.
    zware kleigronden - lössgronden - bodemvorming - chemische eigenschappen - fysicochemische eigenschappen - nederland - clay soils - loess soils - soil formation - chemical properties - physicochemical properties - netherlands
    Weathering rates in 12 horizons of soils developed in loess and clay sediments were measured by means of laboratory experiments. The experiments were carried out by percolating thin columns containing approximately 2 g of soil material. Despite the small amount of sample used, the results were fairly reproducible. Weathering rates in loess soils were 0.8 to 8 times higher than rates measured in sandy soils. The rates in river-clay soils were 4 to 90 times the rates in sandy soils. The weathering rates of the base cations (BC), especially Ca and Mg, strongly increased with clay content. Significant relations were found between the mineralogical composition, total element content and texture characteristics of the samples and the measured weathering rates.
    Exposure of non-target plants to pesticides: a review on atmospheric concentrations and no-effect levels with special attention for herbicide vapours
    Kempenaar, C. ; Tonneijk, A.E.G. ; Eerden, L.J. van der - \ 1998
    Wageningen : AB-DLO - 20
    gewasbescherming - pesticiden - herbiciden - lucht - hygiëne - luchtverontreiniging - neerslag - chemische eigenschappen - zuurgraad - zure regen - chemische samenstelling - planten - chemische analyse - plant protection - pesticides - herbicides - air - hygiene - air pollution - precipitation - chemical properties - acidity - acid rain - chemical composition - plants - chemical analysis
    Optimale meetnetdichtheid van routinematige fysisch-chemische waterkwaliteitmeetnetten.
    Blind, M.W. ; Wiele, P.J. van der; Aalderink, R.H. - \ 1998
    H2O : tijdschrift voor watervoorziening en afvalwaterbehandeling 31 (1998). - ISSN 0166-8439 - p. 89 - 91.
    oppervlaktewater - fysische eigenschappen - chemische eigenschappen - waterkwaliteit - monitoring - optimalisatiemethoden - surface water - physical properties - chemical properties - water quality - monitoring - optimization methods
    De uiteenzetting toont dat voor het uitvoeren van een meetnetdichtheidsanalyse consensus moet bestaan over wat verstaan wordt onder een optimale meetnetdichtheid. Uitgangspunt bij de ruimtelijke inrichting is dat de meetinspanning informatie moet opleveren
    Gevolgen van het beperken van de waterinlaat en doorspoeling van het gebied Voorne-West : beknopte versie
    Hamaker, Ph. ; Aarnink, W.H.B. ; Peerboom, J.M.P.M. - \ 1997
    Wageningen : DLO-Staring Centrum (Rapport / DLO-Staring Centrum 435.2) - 52
    hydrologie - wateraanvoer - waterbeheer - kanalen - oppervlaktewater - chemische eigenschappen - modellen - zuid-holland - glastuinbouw - zuidhollandse eilanden - hydrology - water advance - water management - canals - surface water - chemical properties - models - zuid-holland - greenhouse horticulture - zuidhollandse eilanden
    Gevolgen van het beperken van de waterinlaat en doorspoeling van het gebied Voorne - West : uitgebreide versie
    Hamaker, P. ; Aarnink, W.H.B. ; Peerboom, J.M.P.M. - \ 1997
    Wageningen : DLO-Staring Centrum (Rapport / DLO-Staring Centrum 435)
    hydrologie - wateraanvoer - waterbeheer - kanalen - oppervlaktewater - chemische eigenschappen - modellen - zuid-holland - glastuinbouw - zuidhollandse eilanden - hydrology - water advance - water management - canals - surface water - chemical properties - models - zuid-holland - greenhouse horticulture - zuidhollandse eilanden
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