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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    Bioflocculation of wastewater organic matter at short retention times
    Faust, L. - \ 2014
    Wageningen University. Promotor(en): Huub Rijnaarts, co-promotor(en): Hardy Temmink. - Wageningen : Wageningen University - ISBN 9789462571716 - 153
    afvalwaterbehandeling - uitvlokking - bioreactoren - geactiveerd slib - organische verbindingen - biopolymeren - energieterugwinning - waste water treatment - flocculation - bioreactors - activated sludge - organic compounds - biopolymers - energy recovery
    Organic monolayers and fluoropolymer brushes : functionalization, stability and tribology
    Bhairamadgi, N.S. - \ 2014
    Wageningen University. Promotor(en): Han Zuilhof; Cees van Rijn. - Wageningen : Wageningen University - ISBN 9789461739636 - 178
    unimoleculaire films - organische verbindingen - organische fluorverbindingen - colloïden - polymeren - adhesie - frictie - oppervlakteverschijnselen - unimolecular films - organic compounds - organofluorine compounds - colloids - polymers - adhesion - friction - surface phenomena

    This thesis deals with the adhesion and friction properties of densely grafted and covalently bound fluoropolymer brushes on silicon surfaces with varying thickness and fluorine content. A novel surface-functionalizing method is described using the thiol-yne click (TYC) reaction. The TYC reaction is highly useful for the attachment of functional (bio-)molecules and immobilization of radical initiators onto a surface with high density. Next, the hydrolytic and thermal stability of 24 different types of monolayers on Si(111), Si(100), SiC, SiN, SiO2, CrN, ITO, PAO, Au and stainless steel surfaces was evaluated. Subsequently, based on this outcome, highly stable fluorinated polymers are described as obtained using surface-initiated atom transfer radical polymerization (SI-ATRP) reactions. The effects of thickness and fluorine content on tribological properties of these layers were studied. The adhesion and friction properties were investigated using colloidal probe atomic force microscopy under dry and ambient conditions. The solvent-free lubricating properties of obtained fluoropolymer brushes have been characterized in detail, and demonstrate their potential for e.g., MEMS/NEMS devices.

    Transport and biodegradation of volatile organic compounds : influence on vapor intrusion into buildings
    Picone, S. - \ 2012
    Wageningen University. Promotor(en): Huub Rijnaarts, co-promotor(en): Tim Grotenhuis; P.F.M. van Gaans. - S.l. : s.n. - ISBN 9789461732767 - 149
    vluchtige verbindingen - organische verbindingen - biodegradatie - biochemisch transport - gebouwen - grondwaterverontreiniging - binnenklimaat - volatile compounds - organic compounds - biodegradation - biochemical transport - buildings - groundwater pollution - indoor climate

    Vapor intrusion occurs when volatile subsurface contaminants, migrating from the saturated zone through the unsaturated zone, accumulate in buildings. It is often the most relevant pathway for human health risks at contaminated sites, especially in urban areas; yet its assessment is controversial. Field assessment of vapor intrusion risk is complicated by two interrelated main factors that are controlled by the contaminant’s properties: transport processes in the unsaturated zone and biodegradation in the unsaturated zone. Commonly available vapor intrusion models either overlook significant properties at the field scale or, conversely, are too complex to be applicable at this scale. Specifically, moisture variation, liquid diffusion, dynamic processes such as water table variations, and biodegradation are not adequately accounted for. As a result, the soil gas and indoor air concentrations predicted by existing models frequently overestimate measured concentrations by several orders of magnitude.
    This thesis addressed transport and biodegradation processes of volatile organic compounds, focusing on aerobic unsaturated zones. The main aims were to i) characterize significant transport processes influencing vapor intrusion and ii) quantify and mechanistically describe biodegradation in unsaturated soils. Field experience, numerical modeling and laboratory experiments with toluene and vinyl chloride as reference compounds were combined to separate out the relevant processes influencing vapor intrusion.
    The main conclusions from this thesis indicate that soil moisture variations and aerobic biodegradation are crucial aspects to be jointly considered for the assessment of vapor intrusion. These may contribute to a significant reduction in the risk associated with dissolved volatile organic contaminants. Specific and relevant implications for modeling and monitoring vapor intrusion can be derived. With respect to vapor intrusion modeling, when including unsaturated zone biodegradation, the use of liquid phase biodegradation rates as derived from liquid mixed batches may underestimate by several orders of magnitude the liquid degradation rates in the unsaturated system. Therefore, biodegradation rates derived from unsaturated system appear more appropriate. With respect to monitoring, vertical soil moisture variations and contaminant/oxygen concentration profiles need to be measured in the field, in order to account for the above processes.

    Impacts of manipulated regime shifts in shallow lake model ecosystems on the fate of hydrophobic organic compounds
    Roessink, I. ; Moermond, C.T.A. ; Gillissen, F. ; Koelmans, A.A. - \ 2010
    Water Research 44 (2010). - ISSN 0043-1354 - p. 6153 - 6163.
    organische verbindingen - meren - biologische beschikbaarheid - polychloorbifenylen - zoetwaterecologie - ecologisch evenwicht - sediment - polycyclische aromatische koolwaterstoffen - aquatische ecosystemen - bioaccumulatie - organic compounds - lakes - bioavailability - polychlorinated biphenyls - freshwater ecology - ecological balance - sediment - polycyclic aromatic hydrocarbons - aquatic ecosystems - bioaccumulation - polycyclic aromatic-hydrocarbons - fresh-water microcosms - food webs - community structure - suspended-solids - fish - responses - polychlorobiphenyls
    Regime shifts in shallow lakes may significantly affect partitioning of sediment-bound hydrophobic organic chemicals (HOCs) such as polychlorobiphenyls (PCB) and polycyclic aromatic hydrocarbons (PAH). In replicated experimental model ecosystems mimicking the alternative stable states ‘macrophyte-dominated’ and ‘suspended solid – phytoplankton dominated’, we tested the effects of macrophytes and benthivorous fish presence on mass distribution and bioaccumulation of hexachlorobenzene, PCBs and PAHs. HOC mass distributions and lipid-normalized concentrations in sediment (Soxhlet- and 6-h Tenax-extractable), suspended solids, macrophytes, periphyton, algae, zooplankton, invertebrates and carp revealed that mobile, i.e. less hydrophobic or less aged HOCs were more susceptible to ecological changes than their sequestered native counterparts. Macrophytes were capable of depleting considerable percentages of the bioavailable, fast desorbing HOC fractions in the sediment upper (bioactive) layer, but did not have a significant diluting effect on lipid-normalized HOC concentrations in carp. Carp structured invertebrate communities through predation and stimulated partitioning of HOCs to other system compartments by resuspending the sediment. These results show that shifts in ecosystem structure have clear effects on fate, risks and natural attenuation of sediment-bound organic contaminants.
    Organic monolayers on oxide-free silicon : self-assembly, functionalization, patterning and electronic characterization
    Scheres, L.M.W. - \ 2010
    Wageningen University. Promotor(en): Han Zuilhof. - S.l. : s.n. - ISBN 9789085856641 - 201
    silicium - unimoleculaire films - organische verbindingen - zelf-assemblage - organische scheikunde - silicon - unimolecular films - organic compounds - self assembly - organic chemistry - cum laude
    cum laude graduation (with distinction)
    Modification of silicon nitride and silicon carbide surfaces for food and biosensor applications
    Rosso, M. - \ 2009
    Wageningen University. Promotor(en): Han Zuilhof; Remko Boom, co-promotor(en): Karin Schroen. - [S.l. : S.n. - ISBN 9789085853794 - 221
    organische verbindingen - unimoleculaire films - microfiltratie - nanotechnologie - oppervlaktechemie - oppervlakteverschijnselen - organic compounds - unimolecular films - microfiltration - nanotechnology - surface chemistry - surface phenomena
    Silicon-rich silicon nitride (SixN4, x > 3) is a robust insulating material widely used for the coating of microdevices: its high chemical and mechanical inertness make it a material of choice for the reinforcement of fragile microstructures (e.g. suspended microcantilevers, micro-fabricated membranes-“microsieves”) or for the coating of the exposed surfaces of sensors (field-effect transistors, waveguide optical detectors). To a more limited extent, silicon carbide (SiC) can find similar applications, and this material also starts to be more and more applied in coating and sensor technologies.
    In all these applications, control over the surface properties of inorganic materials is crucial, for example to avoid blockage of membranes during filtration, or to provide sensor surfaces with specific (bio-)recognition properties. In this thesis, a variety of methods is developed to obtain and study robust functional coatings on SixN4 and SiC. These enable a whole new range of applications involving biocompatible and bio-specific surfaces, while retaining the bulk mechanical, structural, electrical or optical properties of the inorganic substrates.
    Chapter 2 and 3 of the thesis give an overview of the great potential of covalent organic monolayers: Chapter 2 presents the formation of alkylthiol, alkylsilane and alkene monolayers, as well as a number of applications in biocompatible surfaces, micro- and nanopatterning of surfaces and sensing. The emphasis of this review chapter is put on the possible combinations of the bulk properties of inorganic materials (electrical, optical, structural) and the surface properties of organic monolayers (wettability, biospecificity, biorepellence). Chapter 3 is focused on biorepellent surfaces in the field of filtration with microfabricated membranes. Indeed, silicon nitride microsieves, despite their high permeability and structural homogeneity, are prone to pore blocking, when submitted to biological solutions. The chapter gives a review of the available surface modification techniques involving organic coatings that can minimize or even prevent this surface contamination. These coatings involve highly hydrophilic oligomers and polymers, which have been widely explored for organic surfaces. Covalent organic monolayers formed onto inorganic surfaces can extend the applications of these biorepellent coatings to microdevices like SixN4 microsieves (as also discussed in Chapters 7 and 8)
    Chapter 4 and 5 present the thermal functionalization with highly stable alkene-based organic monolayers of the surfaces of silicon-rich silicon nitride (Chapter 4) and silicon carbide (Chapter 5). This work was motivated by the substantial knowledge of similar monolayer formation on silicon surfaces1,2 and the initial success of simple functionalizations on silicon nitride.3 The strong covalent attachment of the coating molecules with the substrates makes the obtained hybrid structures much more resistant to chemical degradation than other types of monolayers on these substrates. The reaction proceeds via attachment of the terminal double bond of alkenes with the surface groups (Si-H in the case of silicon nitride surfaces or –OH for silicon carbide surfaces). Besides methyl-terminated surfaces, functional coatings can be obtained by the use of bi-functionalized alkenes (Figure 1), also allowing further surface reactions and the attachment of bio-recognition elements, through covalent attachment of diverse chemical (carboxylic acid, amine) or biological (oligo-peptides, protein) moieties.

    Figure 1. Modification of SiC and Si¬xN4 surfaces with alkyl monolayers
    Chapter 6 describes a modification of this method, where UV irradiation is used instead of heat to initiate the modification of both silicon nitride and silicon carbide. For both materials, this method allows the grafting of heat-sensitive compounds, needs less starting material (using only a liquid film) and provides monolayers with higher quality (as e.g. indicated by grafting density and stability) and higher reproducibility. Here again the attachment of diverse functionalities is possible, via formation of activated esters. After hydrolysis and activation of such grafted ester, amines can be attached in high yield (> 80 %), as demonstrated using X-ray photoelectron spectroscopy (XPS). Besides the homogeneous modification of plain surfaces, this method also opens the way to surface patterning of silicon nitride and silicon carbide and the modification of mechanically sensitive microfabricated devices.
    In Chapters 4 to 6, the chemical functionalizations are studied using X-ray photoelectron spectroscopy (XPS), infrared reflection absorption spectroscopy (IRRAS), atomic force microscopy (AFM), time-of-flight secondary ion mass spectrometry (ToF-SIMS) and static water contact angles. Si-C bonds are formed preferentially upon reaction of SixN4 surfaces with alkenes, similarly to what is reported for pure silicon surfaces, albeit that no measurement could totally exclude the presence of C-N bonds. The wet etching of SiC yields hydroxyl-terminated surfaces, and an IRRAS study reveals the attachment of alkenes via a Markovnikov-type addition (O-C bond formed on the second carbon of the double bond). The stability of these monolayers is reported in acidic and basic conditions, and it was shown that UV initiation yields even more stable monolayers, probably due to some cross-linking of the alkyl chains.
    Chapter 7 explores the biorepellence of UV-initiated monolayers on silicon nitride surfaces Oligomers of ethylene glycols (3 or 6 units: methoxy-tri(ethylene oxide) undec-1-ene (CH3O(CH2CH2O)3(CH2)9CH=CH2; EO3, and methoxy-hexa(ethylene oxide) undec-1-ene (CH3O(CH2CH2O)6(CH2)9CH=CH2; EO6) are attached on the silicon nitride surfaces. The adsorption of two proteins, bovine serum albumin (BSA) and fibrinogen is used to test the biorepellence of the monolayers, in comparison with bare oxidized silicon nitride. Both proteins adsorb readily onto bare SixN4 surfaces, with adsorbed amounts of 1.25 and 2.7 mg.m-2 for BSA and fibrinogen, respectively, of which more than 80 % is irreversibly bound. In contrast to this, when oligomers are attached to the surface, this adsorption decreases to under the detection limit of the method used for this experiment (optical reflectometry). The ex situ study of surfaces with AFM and water contact angles also indicates that some of the monolayers completely prevent the adsorption of proteins.

    Figure 2. Biorepellent behavior of oligoethylene oxide coated SixN4 surfaces
    Chapter 8 describes the applications of the biorepellent coatings used in Chapter 7 (EO6) to silicon nitride microsieves, in order to improve the filtration of biological solutions and liquid food products. The EO6 coatings are successfully formed on microfabricated membranes with pore diameters of 0.45 micrometer, using the UV-initiated monolayer formation described in Chapter 6. This work shows that these coatings could be applied without loss of permeability due to wettability or pore blocking. Moreover, AFM showed that these coatings significantly decrease the adsorption of proteins on the surface between the pores.
    Chapter 9 describes an alternative functionalization technique for inorganic surfaces, namely the use of plasma oxidation of alkyl monolayers to reproducibly form aldehydes (among other oxidized species) onto surfaces. The method described here for silicon and silicon nitride surfaces, is developed for the functionalization of sensitive devices and substrates. The formation of methyl-terminated alkyl monolayers from linear terminal alkenes is one of the easiest to perform, since linear monofunctional alkenes are readily available, their purification is easy (distillation) and their grafting conditions are very flexible (liquid state, heat-resistant, UV-resistant > 250 nm). Once these stable monolayers are formed, a short plasma treatment (0.5 to 2 s) is able to form oxidized functionalities within the top few angstroms of the surface, while the underlying alkyl chains retain their initial packing and insulation properties of the inorganic substrate. The grafting of gold nanoparticles shows that micron-sized patterns can be formed using a soft contact mask to protect a limited area of the monolayer. Alternatively, the aldehydes can be used to attach biotin and avidin onto SixN4 surfaces. The selective adsorption of biotinylated BSA onto the avidin-modified surfaces shows that the plasma treatment of methyl-terminated monolayers is a fast and efficient method to produce surfaces displaying high specific biochemical interactions.
    In the chapter 10, some of the most striking effects that are described in the previous chapters are put into a wider perspective. Especially the formation and stability of monolayers is discussed, also in relation to biofunctionalization, biorepellence, and opportunities for surface engineering are proposed.
    International sediment exchange for tests on organic contaminants
    Eijgenraam, A. - \ 2009
    Wageningen : Wageningen University, Environmental Science (Quarterly report / SETOC 2009.1) - 96
    bodem - bodemchemie - bodemgiftigheid - toxische stoffen - bodemsamenstelling - bepaling - vochtgehalte - organische verbindingen - soil - soil chemistry - soil toxicity - toxic substances - soil composition - determination - moisture content - organic compounds
    Nalevering van stoffen vanuit de waterbodem naar oppervlaktewater
    Schipper, C.A. ; Smedes, F. ; Vink, J.P.M. ; Joziasse, J. ; Noort, P.C.M. van; Smits, J. ; Beek, J. van; Wijdeveld, A. ; Roskam, G.D. ; Oste, L. ; Rijnaarts, H.H.M. ; Lange, H.J. de; Koelmans, A.A. ; Harmsen, J. ; Korytar, P. ; Velz, I. - \ 2009
    Delft : Deltares - 112
    oppervlaktewater - waterkwaliteit - waterverontreiniging - bemonsteren - organische verbindingen - zware metalen - bodemchemie - kanalen - havens - oppervlaktewaterkwaliteit - waterbodems - kaderrichtlijn water - aquatische ecosystemen - uiterwaarden - surface water - water quality - water pollution - sampling - organic compounds - heavy metals - soil chemistry - canals - harbours - surface water quality - water bottoms - water framework directive - aquatic ecosystems - river forelands
    The advent of the Water Framework Directive and the introduction of the Water Act will place the focus of the assessment of aquatic systems on the quality of surface water. This raises the question of the extent to which aquatic sediments act as a source of pollution due to the release of substances. This study examines whether substances are released from aquatic sediments to the water column by means of diffusive transport, and the degree to which this occurs. It also considers what routine or specialist methods are available to measure this subsequent release of substances. Three very different locations (IJmuiden, the Afferdensche and Deestsche Waarden, and the Ghent-Terneuzen Canal) were sampled. A range of measuring techniques were used, and experiments were conducted to quantify emission fluxes of organic compounds (PAHs, PCBs), heavy metals and nutrients
    Nalevering Waterbodems: Uitvoeren meetcampagne en analyseren naleveringPBDE's en HBCD's uit waterbodems
    Velzeboer, I. ; Korytar, P. - \ 2007
    IJmuiden : IMARES (Rapport / Wageningen IMARES C131/07) - 46
    waterkwaliteit - oppervlaktewater - waterverontreiniging - bemonsteren - organische verbindingen - organische verontreinigende stoffen - waterbodems - kaderrichtlijn water - aquatische ecosystemen - water quality - surface water - water pollution - sampling - organic compounds - organic pollutants - water bottoms - water framework directive - aquatic ecosystems
    In het Deltares koploperproject “Biobeschikbaarheid en gedrag van stoffen”, onderdeel A: “Nalevering van stoffen uit waterbodems” (NSW) wordt het belang van nalevering voor de kwaliteit van het oppervlaktewater onderzocht. Dit project moet leiden tot inzicht in de situaties waarin nalevering van stoffen uit de waterbodem naar het oppervlaktewater een significante (secundaire) verontreinigingsbron vormt. Dit met het oog op normoverschrijding in het oppervlaktewater (chemische doelstelling KRW), of het niet bereiken van een goede ecologische toestand (ecologische doelstelling KRW). Het project “Nalevering van stoffen uit waterbodems” is erop gericht om de nalevering via de verschillende verspreidingsroutes te kwantificeren. Onder nalevering wordt zowel stoftransport via de opgeloste fase verstaan (het chemische spoor, met diffusie of kwel als drijvende kracht), als ook transport via resuspensie van waterbodemdeeltjes (het fysische spoor). Daarnaast kunnen biota (benthische macrofauna, vissen, waterplanten) een factor van verontreinigingen zijn, door in de groeifase verontreinigingen uit het sediment in biomassa op te slaan, die na afsterven vrijkomen in de waterfase (het biotische spoor).
    Analyse van natuurlijke stoffen in sediment en baggerslib
    Leonards, P.E.G. ; Stein, A. ; Brandsma, S.H. ; Kwadijk, C.J.A.F. - \ 2005
    IJmuiden : RIVO (Rapport /Nederlands Instituut voor Visserij Onderzoek (RIVO) C077.05) - 10
    sediment - chemische analyse - organisch bodemmateriaal - organische verbindingen - mariene gebieden - verontreinigde sedimenten - sedimentkwaliteit - sediment - chemical analysis - soil organic matter - organic compounds - marine areas - contaminated sediments - sediment quality
    Een validatieonderzoek naar het voorkomen van vier groepen van natuurlijke stoffen (isoflavonen, flavaononen, en fenolcarboxylzuren en anthoraquinonen) in sediment werd uitgevoerd waarbij gebruik werd gemaakt van een analysemethode die voor dioxine-achtige stoffen en endocrien werkende stoffen eerder werd gevalideerd. Het doel van het onderzoek was na te gaan of de natuurlijke stoffen met een dergelijke methode konden worden geanalyseerd. Hiervoor werd de opwerkingsmethode van sedimenten met analytische standaarden en gespiked sediment onderzocht gebruikmakend van het gevalideerde extractie- (ASE) en zuiveringsprotocol voor dioxine-achtige en endocrien werkende stoffen.
    Afbraak van organisch materiaal en bacteriële biomassa in aquacultuur productiesystemen
    Verdegem, M.C.J. ; Torres Beristain, B. - \ 2005
    Aquacultuur 2 (2005). - ISSN 1382-2764 - p. 15 - 19.
    aquacultuur - visteelt - viskwekerijen - visvijvers - waterkwaliteit - organische verbindingen - anaërobe afbraak - aquaculture - fish culture - fish farms - fish ponds - water quality - organic compounds - anaerobic digestion
    Ophoping van mest, voerresten en ander organisch materiaal kan in de vijverteelt tot waterkwaliteitsproblemen leiden. In het laboratorium van de Leerstoelgroep Visteelt en Visserij, Wageningen Universiteit, is de afgelopen jaren onderzoek gedaan naar de omstandigheden die de afbraak van mest, voerresten en ander organisch materiaal bepalen. Dit artikel vat enkele resultaten samen
    Organic matter decomposition in simulated aquaculture ponds
    Torres Beristain, B. - \ 2005
    Wageningen University. Promotor(en): Johan Verreth, co-promotor(en): Marc Verdegem. - [S.I.] : S.n. - ISBN 9789085041702 - 138
    visvijvers - visteelt - aquacultuur - organische verbindingen - decompositie - microbiële afbraak - microbiële ecologie - biomassa productie - recycling - fish ponds - fish culture - aquaculture - organic compounds - decomposition - microbial degradation - microbial ecology - biomass production - recycling

    Different kinds of organic and inorganic compounds (e.g. formulated food, manures, fertilizers) are added to aquaculture ponds to increase fish production. However, a large part of these inputs are not utilized by the fish and are decomposed inside the pond. The microbiological decomposition of the organic matter is a critical factor for water quality control and nutrient recycle. Usually, management practices are developed to control the survival and health of the cultured animals and to maintain good water quality. The microbiological processes are affected by these practices but usually unintentionally. A better control of culture conditions and sustainability of aquaculture ponds is possible with an improvement of the microbiological processes. The present thesis is divided in two parts, the first is a literature review of the microbial ecology of aquaculture ponds and the second is the description of a series of experiments in lab-sc ale aquaculture ponds.

    In the first part, the role of the microorganisms in aquaculture ponds is reviewed, focusing on the decomposition of organic matter and its influence on pond dynamics. It was theoretically estimated that the addition of I kg of formulated feed would yield approximately 125 g bacterial biomass. This bacterial biomass is potentially a valuable nutrients source for higher trophic levels. Sedimentation and resuspension processes are important factors affecting the decomposition pathways. Both processes are directly related with the feeding rate and the stocking density applied. The rate of organic matter loading, environmental factors and pond management practices influence the functioning of algae-bacteria interactions, which are extremely important in pond processes. Included is a literature that describes commercial probiotic products that claim to solve: nutritious, water quality and pathogens problems in pond aquaculture, were analyzed. Alternative management practices to steer the decomposition process were also presented (Chapter 2).

    The second part describes all the experiments that were conducted in lab scale microcosm systems, simulating the conditions of an intensive fish-less aquaculture pond with daily feeding rates. In Chapter 3 the influence of aerobic and anaerobic conditions and the organic C/N ratios on the decomposition process is described. Under aerobic decomposition less organic carbon remained in the systems. The results from this experiment suggest that a C/N ratio ranging between the tested values (6.3 and 12.8) does not have a significant influence on the carbon mineralization in the short term " 50 days). However, a C/N ratio decrease was observed in all the treatments during the experimental period; this reduction was especially fast and steep under aerobic conditions. This decrease in C/N ratio of the organic matter might explain why in all treatments the rate of decomposition slowed down at the end of the experiment. The C/N ratio also determined the concentration of inorganic nitrogen compounds in the water. Higher concentrations were found for the richest protein diet treatments. No nitrification was measured even though oxygen and ammonia were present.

    Bacterial biomass production was quantified testing two formulated fish feed with different protein content under aerobic and anaerobic conditions (Chapter 4). The oxic status significantly influences the bacterial abundance, bacterial biomass, bacterial respiration and bacterial efficiency. More bacterial biomass was produced under aerobic conditions. The two diets did not influence significantly the bacterial growth. The bacterial abundance at the end of the experiment was 3.4 x 109 cells ml-1 in aerobic treatments and 1.9 x 109 cells m1-1 in anaerobic treatments. The remaining amount of carbon, fixed in bacterial biomass and expressed on a per area basis, was 19 g m-2 day-t for aerobic system and 8 g m-2 day-1 for anaerobic systems.

    In Chapter 5 the effect of the oxic-anoxic range on fish feed decomposition was investigated. Different ranges, from completely aerobic to completely anaerobic, were tested. To establish intermediate oxic levels the following treatments were used: 1) alternated flows of 02 or N2 at different periods and 2) maintaining the coexistence of aerobic and anaerobic layers while applying short resuspension events. Similar amounts of carbon were converted to CO2 under completely aerobic conditions and under the different ranges of aerobic-anaerobic conditions. Under anaerobic conditions much less carbon was converted into CO2. This means that actually only limited periods of oxic conditions (or resuspension) are needed to stimulate complete organic matter decomposition. From our results it appears that only 6h per day of aerobic conditions or only once mixing of aerobic and anaerobic layers (i.e. resuspension) per four days are needed to reach the same carbon mineralization as in continuous aerobic conditions. Very limited nitrification was observed in the completely aerobic treatment. Nitrification and denitrification were registered for all the systems when aerobic and anaerobic conditions coexisted in time or space. The highest nitrogen removal (around 70%) was found in the resuspension treatments (and 12 h O2 flow treatment).

    The use of controlled lab scale microcosm simulating intensive aquaculture ponds allowed us to follow the fate of carbon and nitrogen during particular decomposition processes. The results found in the different chapters are discussed in Chapter 6. Both the quality and the quantity of the organic matter influenced the decomposition process and its products. The use of high protein diets increased the concentration of nitrogen species affecting the water quality. The aerobic and anaerobic conditions determined the nutrients pathway (mineralized, assimilated or partially decomposed). More bacterial biomass was produced under aerobic conditions than under anaerobic. The coexistence of aerobic and anaerobic conditions stimulated organic matter decomposition; it avoided the accumulation of ammonia while maintaining good water quality conditions.

    A better understanding and control of the organic matter decomposition in aquaculture ponds is crucial. The anaerobic decomposition only becomes a problem when it predominates in the sediment, causing the aerobic-anaerobic interface to move up into the water column, and thus remains disconnected from the aerobic decomposition. Management practices that link aerobic and anaerobic processes can stimulate fish production by recycling carbon and nitrogen compounds. The recycling of surplus organic matter through bacterial processes, however, has a limit. Increasing fish pond productivity should come along with practices to stimulate the autotrophic and heterotrophic food webs, without exceeding the capacity of this aquatic system.

    Effecten van organische bodemverbeterende middelen op de beschikbaarheid van fosfaat in de bodem op korte en lange termijn
    Ehlert, P.A.I. ; Pasterkamp, H.P. ; Bolhuis, P.R. - \ 2004
    Wageningen : Alterra (Alterra-rapport 991) - 56
    bodemverbeteraars - fosfaat - voedingsstoffenbeschikbaarheid - organische verbindingen - soil conditioners - phosphate - nutrient availability - organic compounds
    De beschikbaarheid van fosfaat uit stalmest en compost voor het gewas is onderzocht. Onderscheid is gemaakt naar de werking op korte termijn dat wil zeggen binnen een groeiseizoen en de lange termijn werking over verschillende jaren. De fosfaatwerking van organische mest¬stoffen op korte termijn is vastgesteld door de mate van wijziging van de fosfaattoestand (Pw-getal en P-AL-getal) te bepalen ten opzichte van die veroorzaakt door tripelsuperfosfaat. Op de korte termijn is de fosfaatwerking van stalmest of compost geringer dan die van tripelsuperfosfaat. De lange termijn werking is vastgesteld met behulp van grondmonsters van veeljarige veldproeven met bodemverbeterende middelen waaronder stalmest en compost. Op de lange termijn is de fosfaatwerking van stalmest of compost vergelijkbaar met die van tripelsuperfosfaat of tripelsuperfosfaat. Veeljarig gebruik van organische bodemverbeterende middelen verlaagt doorgaans de sorptiemaxima ten opzichte van het gebruik van uitsluitend minerale meststoffen.
    Modelling maximum adsorption capacities of soot and soot-like materials for PAHs and PCBs
    Noort, P.C.M. van; Jonker, M.T.O. ; Koelmans, A.A. - \ 2004
    Environmental Science and Technology 38 (2004)12. - ISSN 0013-936X - p. 3305 - 3309.
    aromatische koolwaterstoffen - polycyclische koolwaterstoffen - adsorptie - sorbaten - hydrofobiciteit - organische verbindingen - monitoring - waterkwaliteit - waterbodems - aromatic hydrocarbons - polycyclic hydrocarbons - adsorption - sorbates - hydrophobicity - organic compounds - monitoring - water quality - water bottoms - polycyclic aromatic-hydrocarbons - hydrophobic organic-chemicals - partition-coefficients - aqueous solubilities - black carbon - sorption - water - sediment - extraction - biphenyls
    Recent studies have shown that not partitioning but adsorption is the main mechanism for sorption of hydrophobic organic compounds to soot and soot-like materials. For compounds that adsorb by van der Waals forces only, variation in soot-water distribution coefficients will result from differences in these forces for adsorption, as well as the maximum number of accessible sites. This maximum number of accessible sites may a priori be expected to vary due to differences in both sorbent characteristics and sorbate dimensions. In this modeling study, variation in maximum adsorption capacities is explained from sorbent and sorbate properties. Maximum adsorption capacities were calculated using (a) literature values for soot-water distribution coefficients for polycyclic aromatic hydrocarbons and polycholorobiphenyls on 10 different soot and soot-like materials and (b) Langmuir affinities for adsorption at a carbonaceous surface estimated using a recently reported method
    Recent studies have shown that not partitioning but adsorption is the main mechanism for sorption of hydrophobic organic compounds to soot and soot-like materials. For compounds that adsorb by van der Waals forces only, variation in soot-water distribution coefficients will result from differences in these forces for adsorption, as well as the maximum number of accessible sites. This maximum number of accessible sites may a priori be expected to vary due to differences in both sorbent characteristics and sorbate dimensions. In this modeling study, variation in maximum adsorption capacities is explained from sorbent and sorbate properties. Maximum adsorption capacities were calculated using (a) literature values for soot-water distribution coefficients for polycyclic aromatic hydrocarbons and polychlorobiphenyls on 10 different soot and soot-like materials and (b) Langmuir affinities for adsorption at a carbonaceous surface estimated using a recently reported method. The variation in maximum adsorption capacities could be explained by the variation in sorbent specific surface area, sorbent organic carbon content, and the sorbent-sorbate contact area. Furthermore, increasing sorbate thickness was related to a decrease in maximum adsorption capacities, which points to adsorption in micropores. Maximum adsorption capacities decreased by 1-2 orders of magnitude as the contact area increased by 50%. This points to adsorption sites being hardly larger than sorbates.
    Mycorrhizapaddestoelen als leidraad voor beheeradviezen voor bossen op voedselarme zandgrond
    Ozinga, W.A. ; Arnolds, E.J.M. - \ 2003
    De Levende Natuur 104 (2003)5. - ISSN 0024-1520 - p. 177 - 183.
    paddestoelen - plantengemeenschappen - schimmels - bosbouw - zandgronden - bodemchemie - organische verbindingen - mushrooms - fungi - forestry - plant communities - soil chemistry - organic compounds - sandy soils
    In dit artikel wordt ingegaan op de mogelijkheden en beperkingen van het gebruik van mycorrhizapaddestoelen bij vegetatiekarteringen ten behoeve van natuurbeheer, met een kartering van het Dwingelderveld als voorbeeld
    Compost houdt organischestofgehalte op peil
    Guiking, F.C.T. ; Pronk, A.A. - \ 2003
    De Boomkwekerij 16 (2003)34. - ISSN 0923-2443 - p. 14 - 15.
    houtachtige planten als sierplanten - organische meststoffen - bodemvruchtbaarheid - organische verbindingen - mineralen - stikstof - fosfaten - normen - milieubeleid - mineralenboekhouding - ornamental woody plants - organic fertilizers - soil fertility - organic compounds - minerals - nitrogen - phosphates - standards - environmental policy - nutrient accounting system
    Bemestingsnormen voor organische mest: aanscherping van de MINAS-normen heeft in de boomkwekerij niet geleid tot onoverkomelijke problemen. Gebruik van organische mest is noodzakelijk om natuurlijke afbraak van organische stof na een teelt te compenseren. Gegevens in bijgaande tabellen: 1) Gehalte aan organische stof en effectieve organische stof in organische meststoffen, vergeleken met wettelijk maximaal aan te voeren hoeveelheden (maxima op basis van MINAS of BOOM (Besluit Overige Organische Meststoffen)); 2) Voorbeeldberekening van de bijdrage van compost aan het in stand houden van de organische stof op bedrijfsniveau, met een aanvoer van beperkte hoeveelheden N en P
    Non-halogenated organic compounds including semi-volatile organic compounds (SVOCs)
    Harmsen, J. ; Frintrop, P. - \ 2003
    In: Chemical analysis of contaminated land / Thompson, K.C., Nathanail, C.P., Oxford (UK) : Blackwell (Analytical Chemistry Series ) - ISBN 9781841273341 - p. 189 - 215.
    bodemverontreiniging - bodemonderzoek - monitoring - organische verbindingen - soil pollution - organic compounds - soil testing - monitoring
    Substrates today
    Costa, J.M. ; Heuvelink, E. - \ 2003
    Fruit & Veg tech 3 (2003)4. - ISSN 1569-2930 - p. 29 - 33.
    substraten - kweekmedia - voedingsstoffen - plantenvoeding - anorganische verbindingen - organische verbindingen - agronomische kenmerken - karakteristieken - soortenkeuze - kwaliteitscontroles - substrates - culture media - nutrients - plant nutrition - inorganic compounds - organic compounds - agronomic characteristics - characteristics - choice of species - quality controls
    Een kort overzicht van substraten die in de commerciële tuinbouw gebruikt worden. Karakteristieken van de meest relevante substraten voor de groenteteelt
    Innovative reactor technology for selective oxidation of toxic organic pollutants in wastewater by ozone
    Boncz, M.A. ; Bruning, H. ; Rulkens, W.H. - \ 2003
    Water Science and Technology 47 (2003)10. - ISSN 0273-1223 - p. 17 - 24.
    oxidatie - ozon - organische verbindingen - toxische stoffen - afvalwaterbehandeling - selectiviteit - oxidation - ozone - organic compounds - toxic substances - waste water treatment - selectivity - rate constants - inorganic-compounds - wastewaters
    Ozonation can be a suitable technique for the pre-treatment of wastewater containing low concentrations of toxic or non-biodegradable compounds that cannot be treated with satisfactory results when only the traditional, less expensive biological techniques are applied. In this case, the oxidation process has to be made as efficient as possible, in order to reduce the costs of ozone addition and energy use. An efficient oxidation process with ozone can be obtained by focusing the oxidation with ozone selectively on the direct oxidation of toxic pollutants and to minimize ozone losses due to the decay of ozone in water. Supported by data of the rate constants of the reactions involved, a mathematical model was developed. It quantifies the ozone consumption by the process, and the share of ozone consumption by undesired side reactions, in several different reactor systems
    Ozonation can be a suitable technique for the pre-treatment of wastewater containing low concentrations of toxic or non-biodegradable compounds that cannot be treated with satisfactory results when only the traditional; less expensive biological techniques are applied. In this case, the oxidation process has to be made as efficient as possible, in order to reduce the costs of ozone addition and energy use. An efficient oxidation process with ozone can be obtained by focusing the oxidation with ozone selectively on the direct oxidation of toxic pollutants and to minimize ozone-losses due to the decay of ozone. in water. Supported by data of the rate constants of the reactions involved, a mathematical model was developed. It quantifies the ozone consumption by the process, and the share of ozone consumption by undesired side reactions, in several different reactor systems. Results obtained with this model indicate that a plug flow reactor (PFR) will be the most efficient design for the oxidation reactor. As an alternative, the cascaded tank reactor system (CTR), in which the ozone feed may be realized with less practical problems, might be considered: The traditional continuous flow stirred tank reactor (CFSTR) is shown to be the least efficient system.
    Use of semi-permeable membrane devices and solid-phase extraction for the wide-range screening of microcontaminants in surface water by GC-AED/MS
    Stee, L.L.P. van; Leonards, P.E.G. ; Loon, W.M.G.M. van; Hendriks, A.J. ; Maas, J.L. ; Struijs, J. ; Brinkman, U.A.T. - \ 2002
    Water Research 36 (2002). - ISSN 0043-1354 - p. 4455 - 4470.
    oppervlaktewater - waterverontreiniging - chemicaliën - verontreinigende stoffen - organische verbindingen - rivieren - landbouwchemicaliën - besmetters - toxiciteit - nederland - gc-ms - surface water - water pollution - chemicals - pollutants - organic compounds - rivers - agricultural chemicals - contaminants - toxicity - netherlands - gc-ms - organic pollutants - contaminant identification - solid-phase
    An automated GC-MS-based screening method was developed for over 400 industrial, agrochemical and household chemicals. Extracted ion chromatograms were used and the method was aimed at creating a minimum number of false positives. The compound polarity range usually associated with solid-phase extraction was extended to include very apolar, bioaccumulative, compounds by using the complementary semi-permeable membrane device technique. Real-life samples were taken at four locations in the main Dutch river systems and one in an agricultural area. Some 150 compounds were detected in the low-ng/l to low-g/l range. Next to the target compounds, several brominated and chlorinated non-target compounds were detected by means of GC with atomic emission detection and tentatively identified using mass spectral library searching.
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