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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Microbial electrosynthesis of biochemicals : innovations on biocatalysts, electrodes and ion-exchange for CO2 supply, chemicals production and separation
Bajracharya, S. - \ 2016
Wageningen University. Promotor(en): Cees Buisman; David Strik; Deepak Pant. - Wageningen : Wageningen University - ISBN 9789462578531 - 181 p.
carbon dioxide - biofuels - chemicals - biocatalysis - ion exchange - electrodes - kooldioxide - biobrandstoffen - chemicaliën - biokatalyse - ionenuitwisseling - elektrodes

Microbial electrosynthesis (MES) is an electricity-driven production of chemicals from low-value waste using microorganisms as biocatalysts. MES from CO2 comprises conversion of CO2 to multi-carbon compounds employing microbes at the cathode which use electricity as an energy source. This thesis presents innovations on MES from CO2 using anaerobic mixed-cultures, circumventing the methane generation. Acetate was the primary product but other products including ethanol, butyrate were also produced. Establishment of active biocathode at the graphite felt cathode was achieved under long-term operation which led to the acetate accumulation up to 7-10 g L-1 at -1 V/Ag/AgCl cathode potential. CO2 reduction in MES requires continuous availability of CO2 and low cathode potential to ensure the supply of reducing equivalents/hydrogen. Use of gas diffusion biocathode doubled the CO2 mass-transfer rate which enhanced the production rates, reaching. Furthermore, a sustainable technology for manufacturing biochemicals/biofuels was demonstrated in this thesis by integrating the product separation in MES. The electricity-driven production of chemicals/biofuels from CO2/waste products and subsequent product recovery studies prospect an integration of microbial electrosynthesis with biorefineries for the up-scaling of both technologies.

Assessing the effects of chemicals on aquatic microbial ecosystems
Rocha Dimitrov, M. - \ 2016
Wageningen University. Promotor(en): Hauke Smidt; Paul van den Brink. - Wageningen : Wageningen University - ISBN 9789462576667 - 264 p.
aquatic ecosystems - microorganisms - macroinvertebrates - microbial ecology - aquatic fungi - chemicals - tebuconazole - fungicide residues - pesticides - marine sediments - toxicity - enrofloxacin - fluoroquinolones - zooplankton - phytoplankton - antibiotic resistance - periphyton - bacteria - ecological risk assessment - aquatische ecosystemen - micro-organismen - macroinvertebraten - microbiële ecologie - waterschimmels - chemicaliën - tebuconazool - fungicidenresiduen - pesticiden - mariene sedimenten - toxiciteit - enrofloxacine - fluoroquinolonen - zoöplankton - fytoplankton - antibioticaresistentie - perifyton - bacteriën - ecologische risicoschatting
Metabolic engineering of Escherichia coli for itaconate production
Vuoristo, K.S. - \ 2016
Wageningen University. Promotor(en): Gerrit Eggink; Johan Sanders, co-promotor(en): Ruud Weusthuis. - Wageningen : Wageningen University - ISBN 9789462576001 - 162 p.
fermentation - escherichia coli - aspergillus niger - biobased chemistry - bioengineering - acids - organic acids - glutamates - tca - production - chemicals - fermentatie - chemie op basis van biologische grondstoffen - zuren - organische zuren - glutamaten - productie - chemicaliën

Interest in sustainable development together with limited amounts of fossil resources have increased the demand for production of chemicals and fuels from renewable resources. The market potential for bio-based products is growing and a transition from petrochemicals to biomass-based chemicals is ongoing. Itaconic acid is a C5-dicarboxylic acid which can be produced by microbial conversion processes. It can be easily polymerized and is an appealing building block for the chemical industry with many potential applications. However, biobased chemicals have to compete with their petrochemical counterparts, and yield and productivity of the microbial processes are therefore of the utmost importance. Traditionally itaconic acid is produced using the ascomycete Aspergillus terreus. This process is not competitive with petrochemical processes due to high production costs caused by low yields, and difficult and expensive product recovery. Maximizing product yield is important to lower production costs. This thesis looked at ways to reach theoretical maximum yield in a recombinant production host, Escherichia coli.

Chapter 2 describes the construction of an itaconate biosynthesis pathway in E. coli. The key enzyme of microbial itaconate production is cis-Aconitate decarboxylase (CadA) that converts the citric acid cycle intermediate cis-aconitate into itaconate. We focused on optimizing heterologous expression of cadA from Aspergillus terreus in E. coli. Initially this resulted in low CadA activities and production of trace amounts of itaconate. CadA was primarily present as inclusion bodies, explaining the low activity. The activity was significantly improved by using lower cultivation temperatures and mineral medium and this resulted in enhanced itaconate titres. The itaconate titre was further increased in aerobic bioreactor cultures by introducing citrate synthase and aconitase from Corynebacterium glutamicum and by deleting genes encoding phosphate acetyltransferase and lactate dehydrogenase. The maximum itaconate yield from glucose obtained in this study was only 0.09 mol/mol, due to high flux of carbon to by-products such as acetate and pyruvate. Pyruvate is a precursor molecule for itaconate biosynthesis and its accumulation suggested that the activity of CadA might be one of the rate limiting steps. It was concluded that further optimization of cadA expression, and reduction of acetate formation should be achieved to obtain higher itaconate yield.

As sufficient cis-aconitate decarboxylase activity is crucial for itaconate production, in chapter 3 ways to increase the activity of CadA were investigated. A recently characterized cis-aconitate decarboxylase of mammalian origin was therefore expressed in E.coli. The novel cis-aconitate decarboxylase from Mus musculus encoded by immunoresponsive gene 1 (irg1) produced comparable amounts of itaconate as CadA from A. terreus. In addition, the effects of codon optimization and harmonization on enzymatic activities of heterologously expressed cadA and irg1 were studied. Codon harmonization increased the activity of CadA in cell free extracts, but this did not result in higher itaconate production in bioreactor cultures. This suggests that other factors such as itaconate transport may limit the production.

In chapter 4, proof of principle for an anaerobic fermentation process for the production of itaconic acid was obtained by using the mixed acid fermentation pathway of E. coli. Itaconic acid production was redox balanced by co-producing succinate or ethanol with H2 and CO2. Expression of cadA together with citrate synthase (gltA) and aconitase (acnA) from Corynebacterium glutamicum resulted in 0.66 mM (1.2 % Cmol) itaconate under anaerobic conditions. Unexpectedly, strains started to produce significant amounts of glutamate when the itaconate pathway was introduced. As glutamate production depends on the availability of nitrogen in the medium, a nitrogen-limited medium was tested to diminish glutamate production. This enhanced the production of itaconate to up to 2.9 mM (5.4 % C mol %). Here, anaerobic production of itaconate from glucose was reported for the first time. The observed itaconate yields and productivities were still modest. Eliminating the pathways to major by-products like glutamate, succinate, and acetate, and enhancing the pathway between pyruvate and itaconate is crucial to obtain a cost-competitive anaerobic itaconic acid process production.

To investigate how itaconate production can be improved, the insights from the previous chapters together with existing scientific literature were combined with our pathway design proposals in chapter 5. The tricarboxylic acid (TCA) cycle is an important source of precursors for biobased chemicals. The opinion article takes a closer look at the metabolic engineering of TCA cycle for the production of chemicals high yield. For most TCA cycle products the maximum pathway yield is much lower than the theoretical maximum yield. For succinate, this was solved by creating two pathways to the product, using both branches of the TCA cycle, connected by the glyoxylate shunt. A similar solution cannot be applied directly for production of compounds from the oxidative branch of the TCA cycle because irreversible reactions are involved: the conversion of acetyl-CoA and glyoxylate to malate in the glyoxylate shunt and the conversion of 2-oxoglutarate into succinyl-CoA in the TCA cycle. This way, the pathway yield for products originating from the oxidative TCA cycle branch such as citrate, itaconate and L-glutamate becomes identical to the theoretical maximum. Future research should focus on implementing these solutions in suitable production hosts, and increasing the ATP yield of the production pathways. This will minimize the oxygen requirement of the process, or even allow for anaerobic operation, and should lead to reduced operational costs and maximal product yields.

In chapter 6 the implications of the overall results of this thesis for the current research status of itaconate production are presented. Solutions to optimize itaconate production strains and production process were proposed.

Probabilistic dietary exposure models : relevant for acute and chronic exposure assessment of adverse chemicals via food
Boon, Polly E. ; Voet, H. van der - \ 2015
Bilthoven : RIVM (RIVM letter report 2015-0191) - 41 p.
exposure assessment - exposure - models - chemicals - toxic substances - intake - food consumption - food safety - probabilistic models - blootstellingsbepaling - blootstelling - modellen - chemicaliën - toxische stoffen - opname (intake) - voedselconsumptie - voedselveiligheid - waarschijnlijkheidsmodellen
Exposure models are used to calculate the amount of potential harmful chemicals ingested by a human population. Examples of harmful chemicals are residues of pesticides, chemicals entering food from the environment (such as dioxins, cadmium, lead, mercury), and chemicals that are generated via heating (such as acrylamide and furans). In this report we describe the characteristics of two types of models: the first for calculating the short term-intake, and the second for calculating long-term intake. These models currently result in the most realistic estimation of chemical intake via food.
Sediment toxicity testing and prospective risk assessment of organic chemicals
Diepens, N.J. - \ 2015
Wageningen University. Promotor(en): Bart Koelmans, co-promotor(en): Paul van den Brink. - Wageningen : Wageningen University - ISBN 9789462574991 - 346
sediment - toxiciteit - testen - sedimenttest - verontreinigde sedimenten - chemicaliën - risicoschatting - ecotoxicologie - toxicity - testing - sediment test - contaminated sediments - chemicals - risk assessment - ecotoxicology

While providing an option for development in coastal areas, shrimp farming is usually associated with high environmental cost due to the loss of mangrove forest and high social cost as farmers suffer heavy financial losses due to disease outbreaks. Planning shrimp farming requires to integrate risk as well as social and environmental cost. This thesis, using the Mekong Delta as a case, presents an approach to investigate, with local stakeholders, options to plan a resilient and sustainable shrimp farming sector. First, Olivier Joffre analyzed the different shrimp production systems from economic point of view before analyzing farmer’s strategies and providing insights on drivers that will push or, at the opposite, constraint farmers to choose integrated mangrove shrimp systems. This knowledge was integrated in an Agent Based Model (ABM) that was calibrated using Role Playing Games (RPG).

The effect of future scenarios and different policies on the farmers’ decisions was tested using a combination of RPG and ABM. For one coastal district of the Mekong Delta, the results showed that promotion of intensification of shrimp production has a high social cost and decreases the total production in the study area after 10 years. Policies for supporting the spread of integrated mangrove-shrimp systems, such as Payment for Ecosystem Services, or access to an organic value chain, are not strong enough to influence farmers’ decision toward adopting these systems. Without any adaptation to climate change a sharp decrease of the production is expected. The approach brought local farmers’ knowledge to the attention of decision makers.

Twee vliegen in één klap : duurzame vervangers voor zorgwekkende stoffen zijn kansrijk
Zundert, M. van; Es, D.S. van - \ 2015
Chemie Magazine 57 (2015)7/8. - ISSN 1572-2996 - p. 28 - 29.
chemicaliën uit biologische grondstoffen - biobased economy - marktverkenningen - vervangmiddelen - chemicaliën - biobased chemicals - market surveys - substitutes - chemicals
De lijst van zeer zorgwekkende stoffen is lang. Onderzoeker Daan van Es van de Wageningen UR liep de lijst door en ziet goede kansen voor biobased vervangers.
Actieve biologische Monitoring Zoete Rijkswateren: microverontreinigingen in zoetwatermosselen - 2015
Kotterman, M.J.J. - \ 2014
IJmuiden : IMARES (IMARES / Rapport C085/15) - 37
monitoring - waterbeheer - waterbeleid - watersystemen - mytilidae - chemicaliën - biologische monitoring - microbiële besmetting - waterverontreiniging - mossels - binnenwateren - water management - water policy - water systems - chemicals - biomonitoring - microbial contamination - water pollution - mussels - inland waters
Rijkswaterstaat van het Ministerie van Infrastructuur en Milieu is in 1992 gestart met de uitvoering van het monitoringprogramma “Monitoring Zoete Rijkswateren”. Dit vormt een onderdeel van de “Monitoring van de Waterstaatkundige Toestand des Lands” (MWTL). Doelstellingen van de metingen zijn: - het signaleren van langjarige ontwikkelingen in de biologische toestand van watersystemen (trend). - periodieke toetsing van de toestand aan criteria die voortvloeien uit de toegekende functies van wateren (controle). De opdracht is gebaseerd op het werkdocument “Actieve monitoring chemische stoffen zoetwatermosselen, projectplan chemisch meetnet MWTL 2014”, van 28 augustus 2014 en is uitgevoerd door IMARES. De uit te voeren werkzaamheden betroffen het bemonsteren van zoetwatermosselen en het analyseren van microverontreinigingen daarin. Dit rapport bevat zowel de analyseresultaten van quaggamosselen uit het oorspronkelijke onderzoek in 2014, als ook de resultaten van het aanvullende onderzoek betreffende driehoeksmosselen en quagga’s uit het Spaarne; op tijdstip 0 (niet uitgehangen) en tijdstip 1 (na uithangen, alleen locatie Keizersveer).
RIVM ZZS-2-BIO project : the biobased replacement potential of hazardous substances
Es, D.S. van - \ 2014
Wageningen : Wageningen UR - Food & Biobased Research (Report / Wageningen UR Food & Biobased Research no. 1506) - ISBN 9789462573529 - 74
chemicaliën uit biologische grondstoffen - biobased economy - marktverkenningen - vervangmiddelen - chemicaliën - biobased chemicals - market surveys - substitutes - chemicals
A quick scan of the ZZS (zeer zorgwekkende stoffen) list of 371 substances of very high concern shows that there is significant potential in biobased replacement of part of the list. It is shown that in many cases easily implementable biobased alternatives are already available or in advanced stages of development. However, in some cases safe, biobased alternatives are still in early development. This in spite of a growing need for replacement, as is the case for e.g. high polarity aprotic solvents such as DMF, or NMP. Since solvents like NMP enable the manufacturing of environmentally friendly water borne coatings and paints, as well as the development of various carbohydrate based materials, finding effective substitutes should be given high priority. Unfortunately, currently there are no Dutch national science programs that could support or initiate this. Also more advanced, indirect type of replacement appears feasible. An example of possible short term implementation is the partial replacement of toxic ethylene oxide for the production of ethylene glycol by the hydrogenolysis of glucose to ethylene glycol and propylene glycol. Other advanced level replacements require more time, and deeper analysis in order to assess the impact on product/value chains. A shortlist of nine substances that could be replaced by biobased alternatives on short term is also presented in this quick scan report. The suggested biobased alternatives for this shortlist are either already commercially available or close to commercialisation. This quick scan results in a number of recommendations.
Risk assessment of the dietary exposure to contaminants and pesticide residues in young children in the Netherlands
Boon, P.E. ; Bakker, R. ; Klaveren, J.D. van; Rossum, C.T.M. van - \ 2009
Bilthoven : RIVM (RIVM rapport 350070002) - 190
risicoschatting - peuters en kleuters - gezondheidsgevaren - voedselveiligheid - chemicaliën - waarschijnlijkheidsmodellen - voeding en gezondheid - risk assessment - preschool children - health hazards - food safety - chemicals - probabilistic models - nutrition and health
The diet of children aged 2 to 6 years in the Netherlands is safe regarding the exposure to fumonisin B1, deoxynivalenol, patulin (toxic compounds produced by fungi), nitrate and organophosphorus pesticides. For dioxins, that are mainly present in animal fats, there is a limited probability that an adverse health effect will occur. For acrylamide, that is present in baked and fried foods, there is also a probability of an adverse health effect occurring in young children. However, the extent to which this could happen is as yet unclear. For aflatoxin B1 and ochratoxin A (both also toxic compounds produced by fungi) it was not feasible to determine whether or not adverse health effects occur in this age group. These are the results of a study performed by the National Institute for Public Health and the Environment (RIVM) and the RIKILT-Institute of Food Safety. For acrylamide, aflatoxin B1, dioxins and ochratoxin A, more research is needed to refine the risk assessment. The most important requirements for this purpose are the generation of representative concentration data for aflatoxin B1 and ochratoxin A in food and a better understanding of the toxicological effect of acrylamide. The aim of the study described in this report was to assess the dietary exposure and the related possible health risk, to a selected group of compounds in young children in the Netherlands. For this purpose, food consumption data from the Dutch National Food Consumption Survey 2005/2006-Young children were linked to data on the concentration of these compounds in foods. The health risk of children was subsequently assessed with the help of the available literature regarding the toxicology of these compounds
Identification and handling of uncertainties in dietary exposure assessment
Ooijen, H.J. ; Voet, H. van der; Bakker, M.I. - \ 2009
Bilthoven : RIVM (RIVM report / National Institute for Public Health and the Environment 320103004/2009)
voedselveiligheid - voedselopname - risicoschatting - chemicaliën - onzekerheidsanalyse - blootstellingsbepaling - voeding en gezondheid - food safety - food intake - risk assessment - chemicals - uncertainty analysis - exposure assessment - nutrition and health
Het RIVM en het RIKILT-Instituut voor Voedselveiligheid schatten hoeveel chemische stoffen mensen via voeding binnenkrijgen. De huidige methode zou meer inzicht moeten kunnen geven in de mate waarin deze blootstellingsschattingen onzekerheden bevatten. Het kwantificeren van onzekerheden sluit aan bij de internationale wetenschappelijke activiteiten die momenteel op het gebied van onzekerheidsanalyse van blootstellingsschattingen gaande zijn. Naast het kwantificeren van meer onzekerheden moet de invloed van de (overgebleven) niet-gekwantificeerde onzekerheden op de blootstellingsschatting worden beschouwd
Aanvullende analyses prioritaire KRW-stoffen in vissen, aal en blankvoorn
Kotterman, M.J.J. - \ 2008
IJmuiden : IMARES (Rapport / Wageningen IMARES C117/08) - 20
palingen - rutilus rutilus - anguillidae - chemicaliën - sporenelementen - bemonsteren - kaderrichtlijn water - eels - chemicals - trace elements - sampling - water framework directive
In dit project zijn alen van negen locaties, bemonsterd in de late lente, geanalyseerd op de “nieuwe” KRW prioritaire stoffen; kortketenige gechloreerde paraffinen (SCCP short chain chlorinated paraffins), pentabromodiphenyl ethers (PBDE) en butyltinverbindingen (TBT). Blankvoorn van vijf overeenkomende locaties, bemonsterd in eind september, begin oktober, zijn geanalyseerd op dezelfde stoffen, inclusief de standaard-contaminanten van het MWTL-aal programma (PCB’s en OCP’s). De alen zijn geanalyseerd op basis van de visfilet, de blankvoorns zijn als hele vis geanalyseerd. In beide vissoorten zijn organische contaminanten goed meetbaar, afhankelijk van de locatie. In minder vervuilde gebieden zijn de concentraties soms beneden de rapportage-grens, vooral bij aal. In blankvoorn waren de concentraties van organische contaminanten op vetbasis soms hoger dan in de aal. Dit was vooral opvallend voor een aantal PBDE’s als ook TBT.
REACH en de biobased economy
Es, D.S. van; Harmsen, P.F.H. - \ 2008
chemicaliën - evaluatie - autoriteit - registratie - informatie - europa - biobased economy - chemicals - evaluation - authority - registration - information - europe
Deze info sheet geeft informatie over de Europese REACH verordening (Registratie, Evaluatie en Autorisatie van Chemische stoffen).
Hernieuwbare chemicaliën
Es, D.S. van; Harmsen, P.F.H. - \ 2008
grondstoffenindustrie - vervangbare hulpbronnen - chemicaliën - biomassa - biobased economy - input industries - renewable resources - chemicals - biomass
Hernieuwbare grondstoffen worden steeds interessanter als mogelijke grondstof voor de productie van (bulk) chemicaliën. Deze info sheet geeft informatie over de mogelijkheden van chemicaliën uit biomassa.
Ecologische risicobeoordeling: van boekhouden naar chemische stress ecologie
Brink, P.J. van den - \ 2008
Wageningen : Wageningen UR - ISBN 9789085852698 - 32
ecosystemen - risicoschatting - chemicaliën - pesticiden - ecologie - milieueffect - aquatische ecosystemen - ecotoxicologie - ecosystems - risk assessment - chemicals - pesticides - ecology - environmental impact - aquatic ecosystems - ecotoxicology
Om de negatieve effecten van chemische stoffen op het milieu in te schatten wordt een ecologische risicobeoordeling uitgevoerd die vaak bestaat uit simpele, niet realistische rekenregels en worstcase uitgangspunten. In deze oratie wordt betoogd dat deze procedures een gebrekkige ecologische onderbouwing hebben en daarom niet de werkelijke ecologische risico's kunnen bepalen. Van den Brink neemt in deze rede de bescherming van het zoetwater ecosysteem tegen de negatieve effecten van bestrijdingsmiddelen als uitgangspunt. De wetenschappelijke argumentatie is te extrapoleren naar andere chemische stoffen en milieucompartimenten, al zal deze hier en daar praktische aanpassing behoeven
Chemical biorefinery perspectives : the valorisation of functionalised chemicals from biomass resources compared to the conventional fossil fuel production route
Brehmer, B. - \ 2008
Wageningen University. Promotor(en): Johan Sanders; Remko Boom; Paul Struik. - [S.l.] : S.n. - ISBN 9789085049876 - 181
biomassa - energievoorraden - vervangbare hulpbronnen - brandstoffen - chemicaliën - bioraffinage - petrochemische industrie - biomass - energy resources - renewable resources - fuels - chemicals - biorefinery - petrochemical industry
In response to the impending problems related to fossil fuels (continued supply, price, and
regional and global pollution) alternative feedstocks are gaining interest as possible solutions.
Biomass, considered sustainable and renewable, is an option with the potential to replace a wide
diversity of fossil based products within the energy sector; heat, power, fuels, materials and
chemicals. All the proposed applications for biomass, however, require direct and indirect fossil
derived inputs. The maximum fossil fuel replacement potential of various biomass systems and
biorefinery concepts were determined using life cycle analysis (LCA) tools. Yet, as opposed to a
traditional LCA, the calculation matrix developed here revolves around energy flows and was
extended to incorporate process efficiency in terms of exergy, essentially compiling a comparative
exergetic cradle-to-factory gate analysis. Inclusion of exergy calculations requires a greater
understanding of the processes and reveals that several previous assumptions towards agricultural
systems are no longer suitable for non-biomass applications. It also revealed that by upholding
the functionality of the biochemicals present in biomass for use as chemical products and
precursors, sizeable reductions of fossil fuels can be achieved. Oriented towards existing bulkchemical
products, the analysis was expanded to systematically determine the optimal biorefinery
cropping system from 16 common bioenergy crops in their corresponding regions. Although no
concrete optimum was determined, the results all led to the conclusion that other biomass
systems based on combustion or conversion to combustible products are sub-optimal in
comparison. The best application of biomass for the replacement of fossil fuels is the
petrochemical industry.
Schadelijke stoffen in de dierlijke productieketen, niveaus van voorkomen, normen en overdracht : achtergrond en input voor ketenmodellering
Raamsdonk, L.W.D. van; Meijer, G.A.L. ; Bouwmeester, H. ; Kan, C.A. ; Beek, W.M.J. ; Kemme, P.A. - \ 2007
Wageningen : RIKILT (Rapport / RIKILT 2007.011) - 69
dierlijke producten - voer - besmetters - voedselbesmetting - chemicaliën - toxische stoffen - pesticiden - veterinaire producten - incidentie - normen - monitoring - voedselveiligheid - chemische verbindingen - animal products - feeds - contaminants - food contamination - chemicals - toxic substances - pesticides - veterinary products - incidence - standards - food safety - chemical compounds
Random Sampling of HOCNFs and Underlying Test Reports
Vries, P. de; Smit, M.G.D. ; Jongbloed, R.H. ; Karman, C.C. - \ 2007
Den Helder : IMARES (Report / Wageningen IMARES no. C082/07) - 13
mariene gebieden - verontreiniging - chemicaliën - registratie - willekeurige bemonstering - testrapporten - vergelijkingen - onderzoek - offshore - chemische verbindingen - marine areas - pollution - chemicals - registration - random sampling - test reports - comparisons - research - chemical compounds
Emissiearme kas loopt paar stappen vooruit
Ruijs, M.N.A. - \ 2006
Groenten en Fruit. Algemeen 2006 (2006)40. - ISSN 0925-9694 - p. 22 - 23.
kassen - technologie - gesloten systemen - emissie - licht - chemicaliën - duurzaamheid (sustainability) - glastuinbouw - energiebesparing - greenhouses - technology - closed systems - emission - light - chemicals - sustainability - greenhouse horticulture - energy saving
Met vallen en opstaan worden in de diverse gesloten en semi-gesloten kassen al behoorlijke resultaten met duurzaam telen geboekt. De meeste kassen zijn echter op een bepaalde manier afhankelijk van fossiele energie en beperking van de uitstoot aan licht en chemisch middel is vaak geen hoofddoel. In het project 'Emissiearme Kas' ligt de lat net even hoger
Alternative approaches can greatly reduce the number of fish used for acute toxicity testing
Hoekzema, C.C. ; Murk, A.J. ; Waart, B.J. van de; Hoeven, J.C.M. van der; Roode, D.F. de - \ 2006
Environmental Toxicology and Chemistry 25 (2006)5. - ISSN 0730-7268 - p. 1322 - 1325.
toxiciteit - chemicaliën - tests - toxicologie - testen - vissen - toxicity - chemicals - toxicology - testing - fishes - european-union - ecotoxicity - strategy - daphnia - embryo - algae
We first examined the uptake kinetics of Cd and Zn in the juvenile marine black sea bream (Acanthopagrus schlegeli) over a wide range of ambient Cd and Zn concentrations, and the relationships with metal accumulation (uptake rate and amount of nonexchangeable surface binding) were established for different fish tissues. Both Cd and Zn accumulation in the body increased linearly with exposure time after the initial metal surface binding. The dissolved Cd and Zn uptake rate constants were 2.64 and 6.50 L/kg/d, respectively, and the kinetics followed a first-order process. No evidence of biphasic transport was found, in contrast to the situation in freshwater fish. Viscera were the most important sites of metal uptake, and gills were the second most important sites. The black sea breams were then acclimated at different Cd or Zn concentrations from either waterborne or dietary source for one week, and the alteration of metal uptake kinetics or subcellular distribution and metallothionein (MT) induction were further quantified. The Cd body burden was enhanced up to 8.6- and 49-fold after waterborne and dietary Cd pre-exposure, respectively. Cadmium pre-exposure also altered the tissue-specific subcellular Cd distribution and significantly elevated tissue MT levels. In contrast, the black sea breams were able to regulate Zn accumulation, and waterborne or dietary Zn pre-exposure had only weak influences on Zn body burden and redistribution. Both Cd and Zn pre-exposures enhanced the metal uptake rate constants, whereas the nonexchangeable surface bindings were less impacted by these pre-exposures. We demonstrated a positive relationship between the Cd uptake rate and Cd or MT concentration in the fish. Pre-exposure to metals may substantially modify the kinetics of metal uptake.
Uptake of sediment-bound bioavailable polychlorobiphenyls by benthivorous carp (Cyprinus carpio)
Moermond, C.T.A. ; Roozen, F.C.J.M. ; Zwolsman, J.J.G. ; Koelmans, A.A. - \ 2004
Environmental Science and Technology 38 (2004)17. - ISSN 0013-936X - p. 4503 - 4509.
sediment - biologische beschikbaarheid - polychloorbifenylen - benthos - karper - zoetwatervissen - meren - waterinvertebraten - chemicaliën - opname (uptake) - organische scheikunde - ecotoxicologie - waterbodems - bioavailability - polychlorinated biphenyls - carp - freshwater fishes - lakes - aquatic invertebrates - chemicals - uptake - organic chemistry - ecotoxicology - water bottoms - hydrophobic organic contaminants - aquatic food webs - contact time - pore-water - ingested sediment - extraction - lake - pollutants - fish
It is unclear whether accumulation of sediment-bound chemicals in benthivorous fish depends on the degree of sequestration in the sediment like it does for invertebrates. Here, we report on the potential of slow and fast desorbing sediment-bound polychlorobiphenyl (PCB) fractions for accumulation in carp (Cyprinus carpio) in lake enclosures treated with different nutrient doses
It is unclear whether accumulation of sediment-bound chemicals in benthivorous fish depends on the degree of sequestration in the sediment like it does for invertebrates. Here, we report on the potential of slow and fast desorbing sediment-bound polychlorobiphenyl (PCB) fractions for accumulation in carp (Cyprinus carpio) in lake enclosures treated with different nutrient doses. Routes of PCB uptake were quantitatively evaluated for 15 PCBs (log K-0W range 5.6-7.8) using model analysis. Fast-desorbing PCB fractions in the sediment were defined as the ratio of 6-h Tenax-extractable to (total) Soxhlet-extractable concentrations. These fractions varied between 4 and 22% and did not show a clear trend with log K-0W. However, bioaccumulation of PCBs in carp correlated much better with Tenax-extractable concentrations than with total-extractable concentrations. Nutrient additions in the enclosures had a positive effect on PCB accumulation. Model results show that PCB uptake in carp can be explained from (1) uptake through invertebrate food, (2) uptake from fast-desorbing fractions in ingested sediments, and (3) uptake from water, where PCBs are in partitioning equilibrium with fast-desorbing fractions. The main implication of this research is that fast-desorbing PCB fractions in sediments have great predictive potential for bioaccumulation in benthivorous fish.
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