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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Organizer-Derived WOX5 Signal Maintains Root Columella Stem Cells through Chromatin-Mediated Repression of CDF4 Expression.
Pi, L. ; Graaff, E. van der; Llavata Peris, C.I. ; Weijers, D. ; Henning, L. ; Groot, E. de; Laux, T. - \ 2015
Developmental cell 33 (2015)5. - ISSN 1534-5807 - p. 576 - 588.
histone deacetylase - arabidopsis-thaliana - transcriptional repression - gene-expression - wuschel - meristem - shoot - topless - protein - fate
Stem cells in plants and animals are maintained pluripotent by signals from adjacent niche cells. In plants, WUSCHEL HOMEOBOX (WOX) transcription factors are central regulators of stem cell maintenance in different meristem types, yet their molecular mode of action has remained elusive. Here we show that in the Arabidopsis root meristem, the WOX5 protein moves from the root niche organizer, the quiescent center, into the columella stem cells, where it directly represses the transcription factor gene CDF4. This creates a gradient of CDF4 transcription, which promotes differentiation opposite to the WOX5 gradient, allowing stem cell daughter cells to exit the stem cell state. We further show that WOX5 represses CDF4 transcription by recruiting TPL/TPR co-repressors and the histone deacetylase HDA19, which consequently induces histone deacetylation at the CDF4 regulatory region. Our results show that chromatin-mediated repression of differentiation programs is a common strategy in plant and animal stem cell niches.
Accurate assessment of the biodegradation of cationic surfactants in activated sludge reactors (OECD TG 303A)
Geerts, R. ; Ginkel, C.G. van; Plugge, C.M. - \ 2015
Ecotoxicology and Environmental Safety 118 (2015). - ISSN 0147-6513 - p. 83 - 89.
sewage-treatment - treatment-plant - ammonium-salts - fate - model - chemicals
The continuous-fed activated sludge test (OECD TG 303A) was used to predict the removal of cationic surfactants from wastewater in activated sludge plants. However, a method to differentiate between adsorption and biodegradation is not provided in these guidelines. Assessment of removal by biodegradation was possible with analysis of the surfactant present in mixed liquid suspended solids in combination with a simple equation. This equation was derived from the mass balance of the activated sludge unit in steady state. The removal by biodegradation of decylamine, tetradecylamine, octadecylamine, dioctadecylmethylamine and dioctadecyldimethylammonium chloride that have different capacities to adsorb was >99.9%, >99.9%, 98.2%, 94.2%, and 69.0%, respectively. The total removal of all five cationic surfactants from the influent was =98.8%. The removal of octadecylamine spiked at different influent concentrations indicated first order kinetics
Ecological risk assessment of the antibiotic enrofloxacin applied to Pangasius catfish farms in the Mekong delta, Vietnam
Rico Artero, A. ; Phu, T.M. ; Huong, D.T.T. ; Phuong, N.T. ; Brink, P.J. van den - \ 2015
Chemosphere 119 (2015). - ISSN 0045-6535 - p. 407 - 414.
veterinary antibiotics - ubiquitous occurrence - cell-wall - aquaculture - fate - oxytetracycline - ciprofloxacin - trimethoprim - sulfonamides - microcosms
Antibiotics applied in aquaculture production may be released into the environment and contribute to the deterioration of surrounding aquatic ecosystems. In the present study, we assessed the ecological risks posed by the use of the antibiotic enrofloxacin (ENR), and its main metabolite ciprofloxacin (CIP), in a Pangasius catfish farm in the Mekong Delta region, Vietnam. Water and sediment samples were collected in a stream receiving effluents from a Pangasius catfish farm that had applied ENR. The toxicity of ENR and CIP was assessed on three tropical aquatic species: the green-algae Chlorella sp. (72h - growth inhibition test), the micro-invertebrate Moina macrocopa (48h - immobilization test), and the Nile tilapia (Oreochromis niloticus). The toxic effects on O. niloticus were evaluated by measuring the cholinesterase (ChE) and catalase (CAT) activities in the fish brain and muscles, respectively, and by considering feed exposure and water exposure separately. Ecological risks were assessed by comparing maximum exposure concentrations with predicted no effect concentrations for cyanobacteria, green algae, invertebrates and fish derived with available toxicity data. The results of this study showed that maximum antibiotic concentrations in Pangasius catfish farm effluents were 0.68µgL-1 for ENR and 0.25µgL-1 for CIP (dissolved water concentrations). Antibiotics accumulated in sediments down-stream the effluent discharge point at concentrations up to 2590µgkg-1 d.w. and 592µgkg-1 d.w. for ENR and CIP, respectively. The calculated EC50 values for ENR and CIP were 111000 and 23000µgL-1 for Chlorella sp., and 69000 and 71000µgL-1 for M. macrocopa, respectively. Significant effects on the ChE and CAT enzymatic activities of O. niloticus were observed at 5gkg-1 feed and 400-50000µgL-1, for both antibiotics. The results of the ecological risk assessment performed in this study indicated only minor risks for cyanobacteria communities, suggesting that residual concentrations of ENR and CIP after medication are not likely to result in severe toxic effects on exposed aquatic ecosystems. However, more studies should be performed by considering other antibiotic treatments used in Pangasius catfish production and the potential ecotoxicological effects of relevant antibiotic mixtures on sediment communities.
The analysis of animal faeces as a tool to monitor antibiotic usage
Berendsen, B.J.A. ; Wegh, R.S. ; Memelink, J. ; Zuidema, T. ; Stolker, A.A.M. - \ 2015
Talanta 132 (2015). - ISSN 0039-9140 - p. 258 - 268.
antimicrobial resistance genes - veterinary antibiotics - manure storage - soil - environment - fate - chloramphenicol - sulfadiazine - agriculture - spread
The analysis of antibiotics in animal faeces is important to obtain more insight in the possible formation of bacterial resistance in the animals¿ gut, to learn about the dissemination of antibiotics to the environment, to monitor trends in antibiotic usage and to detect the illegal and off-label use of antibiotics. To facilitate these studies a comprehensive method for the analysis of trace levels of 44 antibiotic compounds including tetracyclines, quinolones, macrolides and sulfonamides in animal faeces by liquid chromatography in combination with tandem mass spectrometric (LC–MS/MS) detection is reported. The method is fully validated according to European regulation and showed satisfactory quantitative performance according to the stringent criteria adopted, with the exception of some of the macrolide compounds, which can be analysed with somewhat high measurement uncertainty. A large survey was carried out monitoring swine and cattle faeces and the outcomes were striking. In 55% of the swines, originating from 80% of the swine farms and in 75% of the calves, originating from 95% of the cattle farms, antibiotics were detected. Oxytetracycline, doxycycline and sulfadiazine were the most detected antibiotics, followed by tetracycline, flumequine, lincomycin and tylosin. Over 34% of the faeces samples contained two or more different antibiotics with a maximum of eight. Possible explanations for these findings are given and the effects are discussed.
Structural and functional response of the soil bacterial community to application of manure from difloxacin-treated pigs
Jechalke, S. ; Focks, A. ; Rosendahl, I. ; Groeneweg, J. ; Siemens, J. ; Heuer, H. ; Smalla, K. - \ 2014
FEMS Microbiology Ecology 87 (2014)1. - ISSN 0168-6496 - p. 78 - 88.
mediated quinolone resistance - antibiotic-resistance - sulfadiazine - genes - plasmid - fate - rhizosphere - evolution - integrons - residues
Difloxacin (DIF) belongs to the class of fluoroquinolone antibiotics that have been intensively used for the treatment of bacterial infections in veterinary and human medicine. The aim of this field study was to compare the effect of manure from DIF-treated pigs and untreated pigs on the bacterial community structure and resistance gene abundance in bulk soil and rhizosphere of maize. A significant effect of DIF manure on the bacterial community composition in bulk soil was revealed by denaturing gradient gel electrophoresis (DGGE) of bacterial 16S rRNA gene fragments amplified from total community DNA. In few samples, quinolone resistance genes qnrB and qnrS1/qnrS2 were detected by PCR and subsequent hybridization, while qnrA was not detected. Quantitative PCR revealed an increased abundance of the integrase gene intI1 of class I integrons and sulfonamide resistance genes sul1 and sul2 in DIF manure-treated bulk soil and rhizosphere, relative to 16S rRNA genes, while traN genes specific for LowGC-type plasmids were increased only in bulk soil. Principal component analysis of DGGE profiles suggested a manure effect in soil until day 28, but samples of days 71 and 140 were found close to untreated soil, indicating resilience of soil community compositions from disturbances by manure.
Soil bulk density and moisture content influence relatieve gas diffusivity and the reduction of nitrogen-15 nitrous oxide
Klefoth, R.R. ; Clough, T.J. ; Oenema, O. ; Groenigen, J.W. van - \ 2014
Vadose Zone Journal 13 (2014)11. - ISSN 1539-1663 - 8 p.
nitrifier denitrification - n2o emission - grassland soil - subsoil - nitrate - water - fate - availability - consumption - diversity
Soil bulk density and moisture influence N2O movement and its reduction. This isotope study shows the sensitivity reduction of N2O, a greenhouse gas, to soil physical properties and their effect on gas diffusion. Increasing soil bulk density and water content promoted N2O reduction. Nitrous oxide is a greenhouse gas and contributes to stratospheric ozone depletion. Soil physical conditions may influence N2O reduction and subsequent N2O emissions. We studied how soil water-filled pore space (WFPS) and soil bulk density (¿b) affect N2O reduction and surface fluxes. Columns were repacked with soil and arranged in a factorial design at three levels of WFPS (60, 75, and 90%) and three levels of soil ¿b (0.94, 1.00, 1.07 Mg m-3). Over 19 d, 15N-enriched N2O was introduced at the base of the soil columns and N2O fluxes were measured. Relative gas diffusivities (Dp/Do) were also calculated. Soil ¿b and WFPS interacted to affect the recovery of N2O-15N and the antecedent inorganic-N contribution to surface fluxes. Reduction rates of N2O-15N ranged from 0.15 to 0.47 mg N2O-N g-1 soil d-1. Calculated Dp/Do values correlated (P <0.01) with soil NH4+–N (r = -0.73), NO3-–N (r = 0.93), cumulative N2O-N flux (r = 0.76), and N2O-N 15N enrichment (r = 0.80) and were affected by a soil WFPS × soil ¿b interaction. Soil N transformations and the net surface N2O flux is dependent on the soil’s Dp/Do, and WFPS alone does not suffice to discriminate between N2O emission sources. Consequently, the soil surface N2O flux may be comprised of N2O originating from deeper soil layers transported upward and/or from production in the topsoil.
Chronic aquatic effect assessment for the fungicide azoxystrobin
Wijngaarden, R.P.A. van; Belgers, J.D.M. ; Zafar, M.I. ; Matser, A.M. ; Boerwinkel, M.C. ; Arts, G.H.P. - \ 2014
Environmental Toxicology and Chemistry 33 (2014)12. - ISSN 0730-7268 - p. 2775 - 2785.
fresh-water microcosms - herbicide linuron - primary producers - outdoor ponds - responses - 3,4-dichloroaniline - chlorpyrifos - sensitivity - fate - invertebrates
This study examined ecological effects of a range of chronic exposure concentrations of the fungicide azoxystrobin in freshwater experimental systems (1270 L outdoor microcosms). Intended and environmentally relevant test concentrations of azoxystrobin were 0, 0.33, 1, 3.3, 10, 33 µg ai/L, kept at constant values. Responses of freshwater populations and community parameters were studied. Over the 42-day experimental period, the time-weighted average concentrations of azoxystrobin ranged from 93.5 to 99.3% of intended values. Zooplankton, especially copepods and Daphnia group longispina, were the most sensitive groups. At the population level, a consistent NOEC of 1 µg ai/L was calculated for Copepoda. The NOEC at the zooplankton community level was 10 µg azoxystrobin/L. The principle of the EU pesticide directive is that lower-tier Regulatory Acceptable Concentrations (RACs) are protective of higher-tier RACs. This was tested for chronic risks from azoxystrobin. With the exception of the microcosm community chronic RAC (highest tier), all other chronic RAC values were similar to each other (0.5 – 1 µg ai/L). The new and stricter first-tier species requirements of the EU pesticide regulation (1107/2009/EC) are not protective for the most sensitive populations in the microcosm study, when based on the higher-tier population RAC. In comparison, the Water Framework Directive (WFD) generates Environmental Quality Standards (EQS) which are 5 - 10 times lower than the derived chronic RACs.
Different compositions of pharmaceuticals in Dutch and Belgian rivers explained by consumption patterns and treatment efficiency
Laak, T.L. ter; Kooij, P.J.F. ; Tolkamp, H. ; Hofman, J. - \ 2014
Environmental Science and Pollution Research 21 (2014)22. - ISSN 0944-1344 - p. 12843 - 12855.
waste-water treatment - personal care products - treatment plants - environmental concentrations - transformation products - aquatic environment - risk-assessment - drinking-water - removal - fate
In the current study, 43 pharmaceuticals and 18 transformation products were studied in the river Meuse at the Belgian-Dutch border and four tributaries of the river Meuse in the southern part of the Netherlands. The tributaries originate from Belgian, Dutch and mixed Dutch and Belgian catchments. In total, 23 pharmaceuticals and 13 transformation products were observed in samples of river water collected from these rivers. Observed summed concentrations of pharmaceuticals and transformation products in river water ranged from 3.5 to 37.8 µg/L. Metformin and its transformation product guanylurea contributed with 53 to 80 % to this concentration, illustrating its importance on a mass basis. Data on the flow rate of different rivers and demographics of the catchments enabled us to calculate daily per capita loads of pharmaceuticals and transformation products. These loads were linked to sales data of pharmaceuticals in the catchment. Simple mass balance modelling accounting for human excretion and removal by sewage treatment plants revealed that sales could predict actual loads within a factor of 3 for most pharmaceuticals. Rivers that originated from Belgian and mixed Dutch and Belgian catchments revealed significantly higher per capita loads of pharmaceuticals (16.0¿±¿2.3 and 15.7¿±¿2.1 mg/inhabitant/day, respectively) than the Dutch catchment (8.7¿±¿1.8 mg/inhabitant/day). Furthermore, the guanylurea/metformin ratio was significantly lower in waters originating from Belgium (and France) than in those from the Netherlands, illustrating that sewage treatment in the Belgian catchment is less efficient in transforming metformin into guanylurea. In summary, the current study shows that consumption-based modelling is suitable to predict environmental loads and concentrations. Furthermore, different consumption patterns and wastewater treatment efficiency are clearly reflected in the occurrence and loads of pharmaceuticals in regional rivers.
Mature osteoblasts dedifferentiate in response to traumatic bone injury in the zebrafish fin and skull
Geurtzen, K. ; Knopf, F. ; Wehner, D. ; Huitema, L.F.A. ; Schulte-Merker, S. ; Weidinger, G. - \ 2014
Development 141 (2014). - ISSN 0950-1991 - p. 2225 - 2234.
fibroblast-growth-factor - fracture repair - adult zebrafish - lining cells - regeneration - expression - defects - fate - gene - rats
Zebrafish have an unlimited capacity to regenerate bone after fin amputation. In this process, mature osteoblasts dedifferentiate to osteogenic precursor cells and thus represent an important source of newly forming bone. By contrast, differentiated osteoblasts do not appear to contribute to repair of bone injuries in mammals; rather, osteoblasts form anew from mesenchymal stem cells. This raises the question whether osteoblast dedifferentiation is specific to appendage regeneration, a special feature of the lepidotrichia bone of the fish fin, or a process found more generally in fish bone. Here, we show that dedifferentiation of mature osteoblasts is not restricted to fin regeneration after amputation, but also occurs during repair of zebrafish fin fractures and skull injuries. In both models, mature osteoblasts surrounding the injury downregulate the expression of differentiation markers, upregulate markers of the pre-osteoblast state and become proliferative. Making use of photoconvertible Kaede protein as well as Cre-driven genetic fate mapping, we show that osteoblasts migrate to the site of injury to replace damaged tissue. Our findings suggest a fundamental role for osteoblast dedifferentiation in reparative bone formation in fish and indicate that adult fish osteoblasts display elevated cellular plasticity compared with mammalian bone-forming cells.
Multimedia Modeling of engineered Nanoparticles with SimpleBox4Nano: Model Definition and Evaluation
Meesters, J. ; Koelmans, A.A. ; Quik, J.T.K. ; Hendriks, A.J. ; Meent, D. van de - \ 2014
Environmental Science and Technology 48 (2014)10. - ISSN 0013-936X - p. 5726 - 5736.
saturated porous-media - environmental exposure - manufactured nanoparticles - aquatic environments - particle deposition - double-layer - nanomaterials - aggregation - transport - fate
Screening level models for environmental assessment of engineered nanoparticles (ENP) are not generally available. Here we present SimpleBox for Nano (SB4N) as the first model of this type, motivate its validity and evaluate it by comparisons with a known material flow model. SB4N expresses ENP transport and concentrations in and across air, rain, surface waters, soil, and sediment, accounting for nano-specific processes such as aggregation, attachment and dissolution. The model solves simultaneous mass balance equations (MBE) using simple matrix algebra. The MBEs link all concentrations and transfer processes using first-order rate constants for all processes known to be relevant for ENPs. The first-order rate constants are obtained from the literature. The output of SB4N is mass concentrations of ENPs as free dispersive species, hetero-aggregates with natural colloids and larger natural particles in each compartment in time and at steady state. Known scenario studies for Switzerland were used to demonstrate the impact of the transport processes included in SB4N on the prediction of environmental concentrations. We argue that SB4N predicted environmental concentrations are useful as background concentrations in environmental risk assessment.
Partitioning of perfluorooctanesulfonate and perfluorohexanesulfonate in the aquatic environment after an accidental release of aqueous film forming foam at Schiphol Amsterdam Airport
Kwadijk, C.J.A.F. ; Kotterman, M.J.J. ; Koelmans, A.A. - \ 2014
Environmental Toxicology and Chemistry 33 (2014)8. - ISSN 0730-7268 - p. 1761 - 1765.
perfluorinated surfactants - perfluoroalkyl acids - firefighting foam - organic-compounds - water - sulfonate - sediment - sorption - biota - fate
In the summer of 2008, an accidental release of Aqueous Film Forming Foam (AFFF) took place at Schiphol Amsterdam Airport (The Netherlands). After the release, water, fish and sediment samples were collected and analyzed for perfluoroalkyl sulfonates (PFSA). In situ perfluorooctane sulfonate (PFOS) KD values, BAF and BSAF values showed a remarkable agreement among reference and impacted sites, 10 weeks after the incident as well as after 3 years.
Heteroaggregation and sedimentation rates for nanomaterials in natural waters
Quik, J.T.K. ; Velzeboer, I. ; Wouterse, M. ; Koelmans, A.A. ; Meent, D. van de - \ 2014
Water Research 48 (2014)1. - ISSN 0043-1354 - p. 269 - 279.
sedimentatie - zwevende deeltjes - aggregatie - nanotechnologie - emissie - schatting - colloïden - waterstroming - zeewater - oppervlaktewaterkwaliteit - sedimentation - suspended solids - aggregation - nanotechnology - emission - estimation - colloids - water flow - sea water - surface water quality - engineered nanomaterials - silver nanoparticles - carbon nanotubes - manufactured nanoparticles - aggregation kinetics - aquatic environments - ceo2 nanoparticles - organic-matter - fate - exposure
Exposure modeling of engineered nanomaterials requires input parameters such as sedimentation rates and heteroaggregation rates. Here, we estimate these rates using quiescent settling experiments under environmentally relevant conditions. We investigated 4 different nanomaterials (C60, CeO2, SiO2-Ag and PVP-Ag) in 6 different water types ranging from a small stream to seawater. In the presence of natural colloids, sedimentation rates ranged from 0.0001md-1 for SiO2-Ag to 0.14md-1 for C60. The apparent rates of heteroaggregation between nanomaterials and natural colloids were estimated using a novel method that separates heteroaggregation from homoaggregation using a simplified Smoluchowski-based aggregation-settling equation applied to data from unfiltered and filtered waters. The heteroaggregation rates ranged between 0.007 and 0.6Lmg-1 day-1, with the highest values observed in seawater. We argue that such system specific parameters are key to the development of dedicated water quality models for ENMs.
Short-term extractability of sulfadiazine after application to soils
Müller, T. ; Rosendahl, I. ; Focks, A. ; Siemens, J. ; Klasmeier, J. ; Matthies, M. - \ 2013
Environmental Pollution 172 (2013). - ISSN 0269-7491 - p. 180 - 185.
sulfonamide antibiotics - test-plot - manure - residues - fate - bioavailability - environment - extraction - transport - pathways
The long-term environmental fate of the veterinary antibiotic sulfadiazine (SDZ) in soils is determined by a reversible sequestration into a residual fraction and an irreversible formation of non-extractable residues (NER), which can be described as first-order rate processes. However, the concentration dynamics of the resulting fractions of SDZ in soil show an unexplained rapid reduction of extractability during the first 24 h. We therefore investigated the short-term extractability of SDZ in two different soils under different SDZ application procedures over 24 h: with and without manure, for air-dried and for moist soils. In all batches, we observed an instantaneous loss of extractability on a time scale of minutes as well as kinetically determined sequestration and NER formation over 24 h. Data evaluation with a simple kinetic model led to the conclusion that application with manure accelerated the short-term formation of NER, whereas sequestration was very similar for all batches.
Thin-Film Photovoltaic Cells: Long-Term Metal(loid) Leaching at Their End-of-Life
Zimmermann, Y.S. ; Schäffer, A. ; Corvini, P.F.X. ; Lenz, M. - \ 2013
Environmental Science and Technology 47 (2013)22. - ISSN 0013-936X - p. 13151 - 13159.
heterojunction solar-cells - daphnia-magna - comparative toxicity - aquatic environment - selenium toxicity - bulk zno - water - cadmium - health - fate
The photovoltaic effect of thin-film copper indium gallium selenide cells (CIGS) is conferred by the latter elements. Organic photovoltaic cells (OPV), relying on organic light-absorbing molecules, also contain a variety of metals (e.g., Zn, Al, In, Sn, Ag). The environmental impact of such technologies is largely unknown, in particular when the physical integrity deteriorates upon end-of-life, possibly facilitating cell constituent leaching. This study analyzed long-term inorganic leaching from damaged OPV and CIGS into different model waters. Leachate concentrations were put into perspective by calculating the predicted environmental concentrations (PEC) for several scenarios. Roof-top acidic rain runoff from CIGS was found to be the predominant emission source for metals and metalloids, with Cd released to such extents that PEC (173.4 µg Cd L–1) would considerably exceed acute toxicity concentrations for Daphnia magna. Other PEC for CIGS (9.9 mg Mo L–1 and 9.4 µg Se L–1) were in the range of teratogenic effects. In contrast, OPV released little metals with calculated PEC being below even conservative drinking water guidelines. Time-resolved single-particle ICP-MS indicated that some metals (Zn, Mo, Ag) were in nanoparticulate form, raising nanotoxicity concerns. Leaching kinetics called for revision of existing standardized (accelerated) leaching protocols because long-term release was most relevant.
Formation and degradation of ethylenethiourea (ETU) in soil and water under tropical conditions
Ruiz-Suárez, L.E. ; Geissen, V. ; Jarquin Sánchez, A. ; Castro Chan, R.A. ; Bello-Mendoza, R. - \ 2013
Journal of Plant Nutrition and Soil Science 176 (2013)1. - ISSN 1436-8730 - p. 40 - 46.
mancozeb - degradation - pesticides - fate
Mancozeb is a fungicide frequently used in tropical countries. It rapidly decomposes into ethylenethiourea (ETU), a more stable and toxic metabolite than mancozeb that is, therefore, regarded as a pollutant of concern. The objective was to study ETU formation and decay kinetics in soil and water under tropical conditions in order to assess its potential for accumulation. Batch experiments, spiked with either mancozeb or ETU, were carried out under natural (= active) as well as tyndallized conditions. In active soils, dissipation of ETU occurred significantly faster (half-life 1.5 h) than in tyndallized soils (half-life time 28 h). In water under natural and sterile conditions, decay was slower than in soils with an ETU half-life time of 115 and 99 h, respectively. Microbial activity was seen to play an important role in ETU dissipation in soil. However, in water nonbiological processes seem to be more important in the breakdown of the molecule, with hydrolysis being the most probable decay mechanism. Decay of both mancozeb and ETU was found to occur more rapidly than previously reported. The high humidity and temperatures under the simulated humid tropical conditions, and higher microbial activity, lead to more rapid decay of these molecules than under other conditions. Nevertheless, a concentration of 1.29 mg ETU L–1 was still observed 8 d after adding mancozeb (20.83 mg L–1) to water under humid tropical conditions. These results suggest that, in comparable regions in the humid tropics, it is unlikely that ETU would accumulate in soil but it represents a potential risk for accumulation in water bodies.
Natural colloids are the dominant factor in the sedimentation of nanoparticles
Quik, J.T.K. ; Cohen Stuart, M.A. ; Wouterse, M. ; Peijnenburg, W. ; Hendriks, A.J. ; Meent, D. van de - \ 2012
Environmental Toxicology and Chemistry 31 (2012)5. - ISSN 0730-7268 - p. 1019 - 1022.
engineered nanomaterials - aquatic environments - oxide nanoparticles - humic-acid - aggregation - fate - exposure - challenges - deposition - transport
Estimating the environmental exposure to manufactured nanomaterials is part of risk assessment. Because nanoparticles aggregate with each other (homoaggregation) and with other particles (heteroaggregation), the main route of the removal of most nanoparticles from water is aggregation, followed by sedimentation. The authors used water samples from two rivers in Europe, the Rhine and the Meuse. To distinguish between small (mainly natural organic matter [NOM]) particles and the remainder of the natural colloids present, both filtered and unfiltered river water was used to prepare the particle suspensions. The results show that the removal of nanoparticles from natural river water follows first-order kinetics toward a residual concentration. This was measured in river water with less than 1¿mg¿L-1 CeO2 nanoparticles. The authors inferred that the heteroaggregation with or deposition onto the solid fraction of natural colloids was the main mechanism causing sedimentation in relation to homoaggregation. In contrast, the NOM fraction in filtered river water stabilized the residual nanoparticles against further sedimentation for up to 12¿d. In 10¿mg¿L-1 and 100¿mg¿L-1 CeO2 nanoparticle suspensions, homoaggregation is likely the main mechanism leading to sedimentation. The proposed model could form the basis for improved exposure assessment for nanomaterials.
Ultrasonic or accelerated solvent extration followed by U-HPLC-high mass accuracy MS for screening of pharmaceuticals and fungicides in soil and plant samples
Chitescu, C.L. ; Oosterink, J.E. ; Jong, J. de; Stolker, A.A.M. - \ 2012
Talanta 88 (2012). - ISSN 0039-9140 - p. 653 - 662.
pressurized-liquid extraction - veterinary antibiotics - chromatography - spectrometry - environment - fate - food
Different veterinary pharmaceuticals are used in agricultural livestock becoming a source of environment contamination. Furthermore, no regulation exists for the concentration limits of pharmaceuticals in soil or water. Monitoring programs for environment contamination with pharmaceuticals are needed, requiring new sensitive and selective screening methods. The present study focuses on developing a method for the simultaneous scanning of forty-two compounds (pharmaceuticals, azole biocides and fungicides) in soil and plant material samples. For extraction purposes the use of ultrasonic assisted and accelerated solvent extraction (ASE) were compared. The extract was purified and concentrated by applying a solid phase extraction step followed by ultra-high-performance-chromatographic separation and accurate-mass spectrometric detection using Exacte Orbitrap technology (FWHM 50,000). The effects of the different extraction solvents and conditions on the extraction efficiency were tested. Although both extraction approaches are applicable the optimal extraction efficiency was obtained by applying accelerated solvent extraction using solvent mixtures containing acetone for soil and methanol for plant samples. An ASE process has been validated for the determination of selected pharmaceuticals and fungicides in soil and in plant material. The recoveries from soil samples were >70% for more than 68% of the compounds. The levels of detection were =10 µg kg-1 for 93% of the compounds tested. The recoveries from plant material were >70% for 64% of the compounds tested. The levels of detection were =10 µg kg-1 for 66% of the compounds. The developed method was used to screen soil and plant material collected throughout the Netherlands and oxytetracycline residues were detected. --------------------------------------------------------------------------------
Assessment of N and P status at the landscape scale using environmental models and measurements
Sonneveld, M.P.W. ; Vos, J.A. de; Kros, J. ; Knotters, M. ; Frumau, A. ; Bleeker, A. ; Vries, W. de - \ 2012
Environmental Pollution 162 (2012)March. - ISSN 0269-7491 - p. 168 - 175.
nitrogen - agriculture - netherlands - deposition - emissions - ammonia - fluxes - fate
We assessed the compliance of a Dutch landscape, dominated by dairy farming, with environmental quality standards using a combination of model calculations and measurements. The total ammonia emission of 2.4 kton NH3 yr-1 does not exceed the environmental quality standard (2.6 kton NH3 yr-1). Nevertheless, the total N deposition (on average 24.4 kg N ha-1 yr-1) is such that critical N loads are exceeded at 53% of the nature areas. The deposited N mainly results from non-agricultural sources and agricultural sources outside the area (72%). The calculated average NO3- concentration in the upper groundwater does not exceed the 50 mg l-1 threshold. Calculated annual average N-total and P-total concentrations in discharge water are relatively high but these cannot be directly compared with thresholds for surface water. The results suggest that compliance monitoring at the landscape scale needs to include source indicators and cannot be based on state indicators alone.
POPCORN Functions in the Auxin Pathway to Regulate Embryonic Body Plan and Meristem Organization in Arabidopsis
Xiang, D.Q. ; Yang, H. ; Venglat, P. ; Cao, Y.G. ; Wen, R. ; Ren, M.Z. ; Stone, S. ; Wang, E. ; Wang, H. ; Xiao, W. ; Weijers, D. ; Berleth, T. ; Laux, T. ; Selvaraj, G. ; Datla, R. - \ 2011
The Plant Cell 23 (2011)12. - ISSN 1040-4651 - p. 4348 - 4367.
stem-cell niche - cup-shaped-cotyledon - shoot meristem - wild-type - gene - embryogenesis - wuschel - fate - monopteros - thaliana
The shoot and root apical meristems (SAM and RAM) formed during embryogenesis are crucial for postembryonic plant development. We report the identification of POPCORN (PCN), a gene required for embryo development and meristem organization in Arabidopsis thaliana. Map-based cloning revealed that PCN encodes a WD-40 protein expressed both during embryo development and postembryonically in the SAM and RAM. The two pcn alleles identified in this study are temperature sensitive, showing defective embryo development when grown at 22 degrees C that is rescued when grown at 29 degrees C. In pcn mutants, meristem-specific expression of WUSCHEL (WUS), CLAVATA3, and WUSCHEL-RELATED HOMEOBOX5 is not maintained; SHOOTMERISTEMLESS, BODENLOS (BDL) and MONOPTEROS (MP) are misexpressed. Several findings link PCN to auxin signaling and meristem function: ectopic expression of DR5(rev):green fluorescent protein (GFP), pBDL:BDL-GFP, and pMP:MP-beta-glucuronidase in the meristem; altered polarity and expression of pPIN1:PIN1-GFP in the apical domain of the developing embryo; and resistance to auxin in the pcn mutants. The bdl mutation rescued embryo lethality of pcn, suggesting that improper auxin response is involved in pcn defects. Furthermore, WUS, PINFORMED1, PINOID, and TOPLESS are dosage sensitive in pcn, suggesting functional interaction. Together, our results suggest that PCN functions in the auxin pathway, integrating auxin signaling in the organization and maintenance of the SAM and RAM.
Nanomaterials for environmental studies: Classification, reference material issues, and strategies for physico-chemical characterisation
Stone, V. ; Nowack, B. ; Baun, A. ; Brink, N.W. van den; Kammer, F. von den; Dusinska, M. ; Handy, R. ; Hankin, S. ; Hassellöv, M. ; Joner, E. ; Fernandes, T.F. - \ 2010
Science of the Total Environment 408 (2010)7. - ISSN 0048-9697 - p. 1745 - 1754.
engineered nanoparticles - safety evaluation - hazard assessment - carbon nanotubes - identification - trends - fate
NanoImpactNet is a European Commission Framework Programme 7 (FP7) funded project that provides a forum for the discussion of current opinions on nanomaterials in relation to human and environmental issues. In September 2008, in Zurich, a NanoImpactNet environmental workshop focused on three key questions: 1. What properties should be characterised for nanomaterials used in environmental and ecotoxicology studies? 2. What reference materials should be developed for use in environmental and ecotoxicological studies? 3. Is it possible to group different nanomaterials into categories for consideration in environmental studies? Such questions have been, at least partially, addressed by other projects/workshops especially in relation to human health effects. Such projects provide a useful basis on which this workshop was based, but in this particular case these questions were reformulated in order to focus specifically on environmental studies. The workshop participants, through a series of discussion and reflection sessions, generated the conclusions listed below. The physicochemical characterisation information identified as important for environmental studies included measures of aggregation/agglomeration/dispersability, size, dissolution (solubility), surface area, surface charge, surface chemistry/composition, with the assumption that chemical composition would already be known. There is a need to have test materials for ecotoxicology, and several substances are potentially useful, including TiO2 nanoparticles, polystyrene beads labelled with fluorescent dyes, and silver nanoparticles. Some of these test materials could then be developed into certified reference materials over time. No clear consensus was reached regarding the classification of nanomaterials into categories to aid environmental studies, except that a chemistry-based classification system was a reasonable starting point, with some modifications. It was suggested, that additional work may be required to derive criteria that can be used to generate such categories, that would also include aspects of the material structure and physical behaviour.
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