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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    Restoration of acidified and eutrophied rich fens: Long-term effects of traditional management and experimental liming
    Diggelen, J. van; Bense, I.H.M. ; Brouwer, E. ; Limpens, J. ; Schie, J.M. van; Smolders, A.J.P. ; Lamers, L.P.M. - \ 2015
    Ecological Engineering 75 (2015). - ISSN 0925-8574 - p. 208 - 216.
    laagveengebieden - eutrofiëring - verzuring - ecologisch herstel - bekalking - fens - eutrophication - acidification - ecological restoration - liming - vegetation development - nutrient availability - nitrogen deposition - surface-water - groundwater - phosphorus - level - limitation - wetlands
    Rich fens are known for their high botanical diversity encompassing many endangered species. For decades, several management measures, including mowing and burning, have been applied to maintain a high biodiversity by means of slowing down the natural succession from calcareous rich fens to acidic poor fens or woodland. In this study, we assessed the long-term effects of these traditional management measures, and explored the effectiveness of liming as a measure to restore rich fen vegetation. Effects of summer mowing, and of burning after winter mowing, were assessed by comparing current (2013) and historical (1967) vegetation data. Effects of experimental liming, using different levels of lime addition (0, 1000, 2000, and 4000 kg Dolokal/ha), were monitored in the field during 7.5 years. Summer mowing led to more acidic and nutrient-poor conditions as indicated by a shift from rich to poor fen vegetation, including a well-developed bryophyte cover dominated by Sphagnum with some threatened species. Burning (after winter mowing) counteracted acidification but increased nutrient availability, as indicated by dominance of vascular species characteristic of productive tall-herb grasslands and a sparse bryophyte cover with common species. We conclude that the traditional measures were unable to maintain rich fen composition in the long term. Given the fact that the restoration of hydrological conditions, favouring rich fens, is not always feasible, liming could be an alternative to counteract acidification and improve rich fen conditions in the short term. This measure, however, appeared to be unsustainable as the re-establishment and dominance of Sphagnum spp. seriously complicated the development of rich fen vegetation in the longer term.
    Climate-smart tank irrigation: A multi-year analysis of improved conjunctive water use under high rainfall variability
    Siderius, C. ; Boonstra, H. ; Munaswamy, V. ; Ramana, C. ; Kabat, P. ; Ierland, E.C. van; Hellegers, P.J.G.J. - \ 2015
    Agricultural Water Management 148 (2015). - ISSN 0378-3774 - p. 52 - 62.
    surface-water - tamil-nadu - india - groundwater - management - projections - efficiency
    Although water harvesting is receiving renewed attention as a strategy to cope with increasing seasonal and inter-annual rainfall variability, many centuries-old local water-harvesting reservoirs (tanks) in India are rapidly deteriorating. Easy access to groundwater is seen as one of the major threats to their maintenance and functioning. Potentially, however, conjunctive use of water from rain, tanks and groundwater reserves, supported by proper monitoring, could improve the resilience and productivity of traditional tank irrigation systems. To date, few quantitative multi-annual analyses of such climate-smart systems have been published. To redress this, we assess the sustainability of a rehabilitated tank irrigation system, by monitoring all inputs and outputs over a period of six years (12 cropping seasons). Our results show that during the period considered, improved conjunctive use resulted in a more stable cropping intensity, increased economic water productivity and higher net agricultural income. Groundwater tables were not negatively affected. We argue that improved conjunctive use can considerably reduce the vulnerability of tank irrigation to rainfall variability and thus is a valuable strategy in light of future climate change.
    Water quality status and trends in agriculture-dominated headwaters; a national monitoring network for assessing the effectiveness of national and European manure legislation in The Netherlands
    Rozemeijer, J.C. ; Klein, J. ; Broers, H.P. ; Tol-Leenders, T.P. van; Grift, B. van der - \ 2014
    Environmental Monitoring and Assessment 186 (2014)12. - ISSN 0167-6369 - p. 8981 - 8995.
    flow route contributions - long-term change - surface-water - nutrient concentrations - temporal variability - groundwater quality - catchment discharge - fresh-water - land-use - phosphorus
    Large nutrient losses to groundwater and surface waters are a major drawback of the highly productive agricultural sector in The Netherlands. The resulting high nutrient concentrations in water resources threaten their ecological, industrial, and recreational functions. To mitigate eutrophication problems, legislation on nutrient application in agriculture was enforced in 1986 in The Netherlands. The objective of this study was to evaluate this manure policy by assessing the water quality status and trends in agriculture-dominated headwaters. We used datasets from 5 agricultural test catchments and from 167 existing monitoring locations in agricultural headwaters. Trend analysis for these locations showed a fast reduction of nutrient concentrations after the enforcement of the manure legislation (median slopes of -0.55 mg/l per decade for total nitrogen (N-tot) and -0.020 mg/l per decade for total phosphorus (P-tot)). Still, up to 76 % of the selected locations currently do not comply with either the environmental quality standards (EQSs) for nitrogen (N-tot) or phosphorus (P-tot). This indicates that further improvement of agricultural water quality is needed. We observed that weather-related variations in nutrient concentrations strongly influence the compliance testing results, both for individual locations and for the aggregated results at the national scale. Another important finding is that testing compliance for nutrients based on summer average concentrations may underestimate the agricultural impact on ecosystem health. The focus on summer concentrations does not account for the environmental impact of high winter loads from agricultural headwaters towards downstream water bodies.
    Nitrous Oxide (N2O) emissions from human waste in 1970-2050
    Strokal, M. ; Kroeze, C. - \ 2014
    Current Opinion in Environmental Sustainability 9-10 (2014). - ISSN 1877-3435 - p. 108 - 121.
    water treatment-plant - coastal waters - climate-change - future-trends - sewage-sludge - anthropogenic nitrogen - reactive nitrogen - nutrient export - surface-water - united-states
    Nitrous oxide (N2O) is an important contributor to climate change. Human waste is an important source of N2O emissions in several world regions, and its share in global emissions may increase in the future. In this paper we, therefore, address N2O emission from human waste: collected (from treatment and from sewage discharges) and uncollected waste. We review existing literature on emissions and emission factors, and present region-specific estimates of N2O emissions and their past and future trends. We show that human waste may became an important source of N2O emissions in the coming years as a result of increasing urbanization. About two-thirds of the global emissions are from uncollected waste, and about half from South Asia. We argue that more research is needed to improve emission factors.
    Identification of Unknown Microcontaminants in Dutch River Water by Liquid Chromatography-High Resolution Mass Spectrometry and Nuclear Magnetic Resonance Spectroscopy.
    Leerdam, J.A. van; Vervoort, J.J.M. ; Stroomberg, G. ; Voogt, P. de - \ 2014
    Environmental Science and Technology 48 (2014)21. - ISSN 0013-936X - p. 12791 - 12799.
    accurate-mass - degradation-products - phenolic resins - waste-water - transformation products - polar pesticides - surface-water - catalyst type - contaminants - formaldehyde
    In the past decade during automated surface water monitoring in the river Meuse at border station Eijsden in The Netherlands, a set of unknown compounds were repeatedly detected by online liquid chromatography-diode-array detection in a relatively high signal intensity. Because of the unknown nature of the compounds, the consequently unknown fate of this mixture in water treatment processes, the location being close to the water inlet of a drinking water supply company and their possible adverse public health effects, it was deemed necessary to elucidate the identity of the compounds. No data are available for the occurrence of these unknowns at downstream locations. After concentration and fractionation of a sample by preparative Liquid Chromatography, identification experiments were performed using Liquid Chromatography-High Resolution Mass Spectrometry (LC-HR-MS) combined with High Resolution Nuclear Magnetic Resonance Spectroscopy (HR-NMR). Accurate mass determination of the unknown parent compound and its fragments obtained in MS/MS provided relevant information on the elemental composition of the unknown compounds. With the use of NMR techniques and the information about the elemental composition, the identity of the compounds in the different sample fractions was determined. Beside some regularly detected compounds in surface water, like caffeine and bisphenol-S, five dihydroxydiphenylmethane isomers were identified. The major unknown compound was identified as 4,4'-dihydroxy-3,5,3',5'-tetra(hydroxymethyl)diphenylmethane. This compound was confirmed by analysis of the pure reference compound. This is one of the first studies that employs the combination of high resolution MS with NMR for identification of truly unknown compounds in surface waters at the µg/L level. Five of the seven identified compounds are unexpected and not contained in the CAS database, while they can be presumed to be products generated during the production of resins.
    Supporting IWRM through spatial integrated assessment in the Lake Naivasha basin, Kenya
    Oel, P.R. van; Odongo, V.O. ; Mulatu, D.W. ; Muthoni, F.K. ; Ndungu, J.N. ; Ogada, J.O. ; Veen, A. van der - \ 2014
    International Journal of Water Resources Development 30 (2014)3. - ISSN 0790-0627 - p. 605 - 618.
    water-resources management - surface-water - african lake - human impact - catchment - ecology - availability - complexity - nutrients - framework
    This study describes the mismatch between required knowledge and efforts by scientists and stakeholders in the Lake Naivasha basin, Kenya. In the basin, integrated water resources management (IWRM) suffers from the absence of critically relevant knowledge. This study further presents a spatial integrated assessment framework for supporting IWRM in the basin. This framework resulted from an ongoing debate between stakeholders and scientists studying the basin's issues. It builds on jointly identified indicators for sustainable governance, and their interdependency, and knowledge gaps. For IWRM in the basin this is a first important step towards a more structured debate on the implementation of IWRM.
    Global water resources affected by human interventionss and climate change
    Haddeland, I. ; Heinke, J. ; Biemans, H. ; Eisner, S. ; Florke, M.F. ; Hanasaki, N. ; Konzmann, M. ; Ludwig, F. - \ 2014
    Proceedings of the National Academy of Sciences of the United States of America 111 (2014)9. - ISSN 0027-8424 - p. 3251 - 3256.
    integrated model - bias correction - surface-water - validation - fluxes - scheme
    Humans directly change the dynamics of the water cycle through dams constructed for water storage, and through water withdrawals for industrial, agricultural, or domestic purposes. Climate change is expected to additionally affect water supply and demand. Here, analyses of climate change and direct human impacts on the terrestrial water cycle are presented and compared using a multimodel approach. Seven global hydrological models have been forced with multiple climate projections, and with and without taking into account impacts of human interventions such as dams and water withdrawals on the hydrological cycle. Model results are analyzed for different levels of global warming, allowing for analyses in line with temperature targets for climate change mitigation. The results indicate that direct human impacts on the water cycle in some regions, e.g., parts of Asia and in the western United States, are of the same order of magnitude, or even exceed impacts to be expected for moderate levels of global warming (+2 K). Despite some spread in model projections, irrigation water consumption is generally projected to increase with higher global mean temperatures. Irrigation water scarcity is particularly large in parts of southern and eastern Asia, and is expected to become even larger in the future.
    Comparing projections of future changes in runoff from hydrological and biome models in ISI-MIP
    Davie, J.C.S. ; Falloon, P.D. ; Kahana, R. ; Dankers, R. ; Betts, R. ; Portmann, F.T. ; Wisser, D. ; Clark, D.B. ; Ito, A. ; Masaki, Y. ; Nishina, K. ; Fekete, B. ; Tessler, Z. ; Wada, Y. ; Liu, X. ; Tang, Q. ; Hagemann, S. ; Stacke, T. ; Pavlick, R. ; Schaphoff, S. ; Gosling, S.N. ; Franssen, W.H.P. ; Arnell, N. - \ 2013
    Earth System dynamics 4 (2013)2. - ISSN 2190-4979 - p. 359 - 374.
    climate-change - carbon-dioxide - integrated model - hadgem2 family - surface-water - river flow - vegetation - impact - co2 - evapotranspiration
    Future changes in runoff can have important implications for water resources and flooding. In this study, runoff projections from ISI-MIP (Inter-sectoral Impact Model Inter-comparison Project) simulations forced with HadGEM2-ES bias-corrected climate data under the Representative Concentration Pathway 8.5 have been analysed for differences between impact models. Projections of change from a baseline period (1981-2010) to the future (2070-2099) from 12 impacts models which contributed to the hydrological and biomes sectors of ISI-MIP were studied. The biome models differed from the hydrological models by the inclusion of CO2 impacts and most also included a dynamic vegetation distribution. The biome and hydrological models agreed on the sign of runoff change for most regions of the world. However, in West Africa, the hydrological models projected drying, and the biome models a moistening. The biome models tended to produce larger increases and smaller decreases in regionally averaged runoff than the hydrological models, although there is large inter-model spread. The timing of runoff change was similar, but there were differences in magnitude, particularly at peak runoff. The impact of vegetation distribution change was much smaller than the projected change over time, while elevated CO2 had an effect as large as the magnitude of change over time projected by some models in some regions. The effect of CO2 on runoff was not consistent across the models, with two models showing increases and two decreases. There was also more spread in projections from the runs with elevated CO2 than with constant CO2. The biome models which gave increased runoff from elevated CO2 were also those which differed most from the hydrological models. Spatially, regions with most difference between model types tended to be projected to have most effect from elevated CO2, and seasonal differences were also similar, so elevated CO2 can partly explain the differences between hydrological and biome model runoff change projections. Therefore, this shows that a range of impact models should be considered to give the full range of uncertainty in impacts studies.
    Global streamflow and thermal habitats of freshwater fishes under climate change
    Vliet, M.T.H. van; Ludwig, F. ; Kabat, P. - \ 2013
    Climatic Change 121 (2013)4. - ISSN 0165-0009 - p. 739 - 754.
    potential impacts - surface-water - temperature - ecosystems - model - biodiversity - organization - perspective - challenges - regimes
    Climate change will affect future flow and thermal regimes of rivers. This will directly affect freshwater habitats and ecosystem health. In particular fish species, which are strongly adapted to a certain level of flow variability will be sensitive to future changes in flow regime. In addition, all freshwater fish species are exotherms, and increasing water temperatures will therefore directly affect fishes’ biochemical reaction rates and physiology. To assess climate change impacts on large-scale freshwater fish habitats we used a physically-based hydrological and water temperature modelling framework forced with an ensemble of climate model output. Future projections on global river flow and water temperature were used in combination with current spatial distributions of several fish species and their maximum thermal tolerances to explore impacts on fish habitats in different regions around the world. Results indicate that climate change will affect seasonal flow amplitudes, magnitude and timing of high and low flow events for large fractions of the global land surface area. Also, significant increases in both the frequency and magnitude of exceeding maximum temperature tolerances for selected fish species are found. Although the adaptive capacity of fish species to changing hydrologic regimes and rising water temperatures could be variable, our global results show that fish habitats are likely to change in the near future, and this is expected to affect species distributions
    The links between global carbon, water and nutrient cycles in an urbanizing world — the case of coastal eutrophication
    Kroeze, C. ; Hofstra, N. ; Ivens, W. ; Löhr, A. ; Strokal, M. ; Wijnen, J. van - \ 2013
    Current Opinion in Environmental Sustainability 5 (2013)6. - ISSN 1877-3435 - p. 566 - 572.
    climate-change - surface-water - reactive nitrogen - rivers - boundaries - planetary - impacts - system - land - consequences
    The natural cycles of carbon (C), nitrogen (N), phosphorus (P) and water have been disturbed substantially by human activities. Urbanizing coastal drainage basins and large river deltas are located at the interface of freshwater and coastal components of the larger earth system and the process of urbanization is increasingly affecting these cycles. We take coastal water pollution as an example to illustrate this. To ensure sustainable development of urban-dominated water systems, future research challenges must include studies of the effects of the urbanization process on biogeochemical cycles that firstly, account for feedbacks and tipping points at the global scale; secondly, link to the Sustainability Development Goals; and finally, link to other forms of pollution. Urban coastal systems are of particular interest when exploring human–water–nutrient cycle interactions, and effective solutions for environmental and health problems associated with these interactions.
    Pesticide risk assessment and management in a globally chgangin world - report from a european interdisciplinary workshop
    Babut, M. ; Arts, G.H.P. ; Barra Caracciolo, A. ; Carluer, N. ; Domage, N. - \ 2013
    Environmental Science and Pollution Research 20 (2013)11. - ISSN 0944-1344 - p. 8298 - 8312.
    semipermeable-membrane devices - photosystem-ii inhibitors - passive sampling devices - climate-change - fresh-water - herbicide losses - surface-water - in-situ - environmental-protection - potential application
    Global River Discharge and Water Temperature under Climate Change
    Vliet, M.T.H. van; Franssen, W.H.P. ; Yearsley, J.R. ; Ludwig, F. ; Haddeland, I. ; Lettenmaier, D.P. ; Kabat, P. - \ 2013
    Global environmental change : human and policy dimensions 23 (2013)2. - ISSN 0959-3780 - p. 450 - 464.
    stream temperature - united-states - surface-water - change impact - potential impacts - ocean circulation - air temperatures - low flows - model - quality
    Climate change will affect hydrologic and thermal regimes of rivers, having a direct impact on freshwater ecosystems and human water use. Here we assess the impact of climate change on global river flows and river water temperatures, and identify regions that might become more critical for freshwater ecosystems and water use sectors. We used a global physically based hydrological-water temperature modelling framework forced with an ensemble of bias-corrected general circulation model (GCM) output for both the SRES A2 and B1 emissions scenario. This resulted in global projections of daily river discharge and water temperature under future climate. Our results show an increase in the seasonality of river discharge (both increase in high flow and decrease in low flow) for about one-third of the global land surface area for 2071–2100 relative to 1971–2000. Global mean and high (95th percentile) river water temperatures are projected to increase on average by 0.8–1.6 (1.0–2.2) °C for the SRES B1–A2 scenario for 2071–2100 relative to 1971–2000. The largest water temperature increases are projected for the United States, Europe, eastern China, and parts of southern Africa and Australia. In these regions, the sensitivities are exacerbated by projected decreases in low flows (resulting in a reduced thermal capacity). For strongly seasonal rivers with highest water temperatures during the low flow period, up to 26% of the increases in high (95th percentile) water temperature can be attributed indirectly to low flow changes, and the largest fraction is attributable directly to increased atmospheric energy input. A combination of large increases in river temperature and decreases in low flows are projected for the southeastern United States, Europe, eastern China, southern Africa and southern Australia. These regions could potentially be affected by increased deterioration of water quality and freshwater habitats, and reduced water available for human uses such as thermoelectric power and drinking water production
    Temporal variations in natural attenuation of chlorinated aliphatic hydrocarbons in eutrophic river sediments impacted by a contaminated groundwater plume
    Hamonts, K. ; Kuhn, T. ; Vos, J. ; Maesen, M. ; Kalka, H. ; Smidt, H. ; Springael, D. ; Meckenstock, R.U. ; Dejonghe, W. - \ 2012
    Water Research 46 (2012)6. - ISSN 0043-1354 - p. 1873 - 1888.
    dehalococcoides sp strain - isotope fractionation analysis - vinyl-chloride reductase - bearing soil minerals - surface-water - degradation - aquifer - biodegradation - dechlorination - identification
    Chlorinated aliphatic hydrocarbons (CAHs) often discharge into rivers as contaminated groundwater base flow. Biotrans formation, sorption and dilution of CAHs in the impacted river sediments have been reported to reduce discharge, but the effect of temporal variations in environmental conditions on the occurrence and extent of those processes in river sediments is largely unknown. We monitored the reduction of CAH discharge into the Zenne River during a 21-month period. Despite a relatively stable influx of CAHs from the groundwater, the total reduction in CAH discharge from 120 to 20 cm depth in the river sediments, on average 74 +/- 21%, showed moderate to large temporal variations, depending on the riverbed location. High organic carbon and anaerobic conditions in the river sediments allowed microbial reductive dechlorination of both chlorinated ethenes and chlorinated ethanes. delta C-13 values of the CAHs showed that this biotransformation was remarkably stable over time, despite fluctuating pore water temperatures. Daughter products of the CAHs, however, were not detected in stoichiometric amounts and suggested the co-occurrence of a physical process reducing the concentrations of CAHs in the riverbed. This process was the main process causing temporal variations in natural attenuation of the CAHs and was most likely dilution by surface water-mixing. However, higher spatial resolution monitoring of flow transients in the riverbed is required to prove dilution contributions due to dynamic surface water-groundwater flow exchanges. delta C-13 values and a site-specific isotope enrichment factor for reductive dechlorination of the main groundwater pollutant vinyl chloride (VC) allowed assessment of changes over time in the extent of both biotransformation and dilution of VC for different scenarios in which those processes either occurred consecutively or simultaneously between 120 and 20 cm depth in the riverbed. The extent of reductive dechlorination of VC ranged from 27 to 89% and differed spatially but was remarkably stable over time, whereas the extent of VC reduction by dilution ranged from 6 to 94%, showed large temporal variations, and was often the main process contributing to the reduction of VC discharge into the river.
    Accurate mass screening of pharmaceuticals and fungicides in water by U-HPLC-Exactive Orbitrap MS
    Chitescu, C.L. ; Oosterink, E. ; Jong, J. de; Stolker, A.A.M. - \ 2012
    Analytical and Bioanalytical Chemistry 403 (2012)10. - ISSN 1618-2642 - p. 2997 - 3011.
    liquid-chromatography - antifungal agents - surface-water - spectrometry - antibiotics - groundwater - suppression - resistance - residues - time
    The use of pharmaceuticals in livestock production is a potential source of surface water, groundwater and soil contamination. Possible impacts of antibiotics on the environment include toxicity and the emergence of antibiotic resistance. Monitoring programs are required to record the presence of these substances in the environment. A rapid, versatile and selective multi-method was developed and validated for screening 43 pharmaceutical and fungicides compounds, in surface and groundwater, in one single full-scan MS method, using benchtop U-HPLC-Exactive Orbitrap MS at 50,000 (FWHM) resolution. Detection was based on calculated exact masses and on retention time. Sample volume, pH conditions and solid-phase extraction (SPE) sample clean-up conditions were optimized. In the final method, 74 % of the compounds had recoveries higher than 80 %, 15 % of the compounds had recoveries between 60 % and 80 %, and 7 % of the compounds had recoveries between 40 % and 50 %. One of the compounds (itraconazole) had a recovery lower than 10 % and nystatin was not detected. The level of detection was 10 ng L-1 for 61 % of the compounds, 50 ng L-1 for 32 % and 100 ng L-1 for 5%. In-house validation, based on EU guidelines, proves that the detection capability CC beta is lower than 10 ng L-1 (for beta error 5 %) for 37 % of the compounds, lower than 50 ng L-1 for 35 % of the compounds and lower than 100 ng L-1 for 14 % of compounds. This study demonstrates that the ultra-high resolution and reliable mass accuracy of Exactive Orbitrap MS permits the detection of pharmaceutical residues in a concentration range of 10-100 ng L-1, applying a post target screening approach, in the multi-method conditions.
    Modeling global nutrient export from watersheds
    Kroeze, C. ; Bouwman, A.F. ; Seitzinger, S. - \ 2012
    Current Opinion in Environmental Sustainability 4 (2012)2. - ISSN 1877-3435 - p. 195 - 202.
    gulf-of-mexico - riverstrahler model - sampling frequency - reactive nitrogen - surface-water - river-systems - phosphorus - trends - ecosystems - budget
    We describe how global models can be used to analyze past and future trends in nutrient export from watersheds and how such models can be used to analyze causes and effects of coastal eutrophication. Future nutrient inputs to coastal waters may be higher than today, and nutrient ratios may depart from Redfield ratios, but not in all world regions. We discuss the strengths and weaknesses of available nutrient export models. We argue that future global nutrient export models are preferably dynamic, distributed and mechanistic. There is a need for agricultural and sanitation policies aimed at reducing coastal eutrophication. More measurements of nutrients in rivers are needed, especially in the tropics.
    Triple Bioaffinity Mass Spectrometry Concept for Thyroid Transporter Ligands
    Aqai, P. ; Fryganas, C. ; Mizuguchi, M. ; Haasnoot, W. ; Nielen, M.W.F. - \ 2012
    Analytical Chemistry 84 (2012). - ISSN 0003-2700 - p. 6488 - 6493.
    brominated flame retardants - ms-binding assays - human transthyretin - in-vitro - tetrabromobisphenol-a - disrupting chemicals - surface-water - pharmaceuticals - identification - metabolites
    For the analysis of thyroid transporter ligands, a triple bioaffinity mass spectrometry (BioMS) concept was developed, with the aim at three different analytical objectives: rapid screening of any ligand, confirmation of known ligands in accordance with legislative requirements, and identification of emerging yet unknown ligands. These three purposes share the same biorecognition element, recombinant thyroid transport protein transthyretin (rTTR), and dedicated modes of liquid chromatography-mass spectrometry (LC-MS). For screening, a rapid and radiolabel-free competitive inhibition MS binding assay was developed with fast ultrahigh performance-liquid chromatography-electrospray ionization-triple-quadrupole-MS (UPLC-QqQ-MS) as the readout system. It uses the nonradioactive stable isotopic thyroid hormone 13C6-l-thyroxine as the label of which the binding to rTTR is inhibited by any ligand such as thyroid drugs and thyroid endocrine disrupting chemicals (EDCs). To this end, rTTR is either used in solution or immobilized on paramagnetic microbeads. The concentration-dependent inhibition of the label by the natural thyroid hormone l-thyroxine (T4), as a model analyte, is demonstrated in water at part-per-trillion and in urine at part-per-billion level. For confirmation of identity of known ligands, rTTR was used for bioaffinity purification for confirmation of naturally present free T4 in urine. As a demonstrator for identification of unknown ligands, the same rTTR was used again but in combination with nano-UPLC-quadrupole time-of-flight-MS (nLC-Q-TOF-MS) and urine samples spiked with the model “unknown” EDCs triclosan and tetrabromobisphenol-A. This study highlights the potential of BioMS using one affinity system, both for rapid screening and for confirmation and identification of known and unknown emerging thyroid EDCs.
    Pesticides in South African fresh waters
    Ansara-Ross, T. ; Wepener, V. ; Brink, P.J. van den; Ross, M.J. - \ 2012
    African Journal of Aquatic Science 37 (2012)1. - ISSN 1608-5914 - p. 1 - 16.
    source insecticide pollution - ddt-sprayed area - lourens river - western-cape - azinphos-methyl - surface-water - oreochromis-mossambicus - risk-assessment - macroinvertebrate communities - fungicide carbendazim
    Public concern has recently escalated over pesticide contamination of South African aquatic ecosystems. This review of published literature on the occurrence of pesticides within South African freshwater systems indicates that fewer than 50 studies of selected pesticides have been undertaken, with emphasis being on organochlorines. Extensive historical usage has led to the widespread persistence of selected organochlorines. Few studies have established linkages between pesticides, exposure pathways, environmental concentrations and the monitoring of toxicological effects on non-target organisms. Emphasis is now being placed on developing more field-relevant assessments, including microcosm and mesocosm studies, in situ bioassays and field studies. There are few data relating to the extent of exposure and effects of pesticides in South African aquatic environments, and thus further research is needed. Research should focus on multidisciplinary approaches that increase effective decisionmaking in data-poor circumstances. A pesticide risk assessment programme for aquatic ecosystems needs to be implemented in South Africa, which could feed into the National Toxicity Monitoring Programme. Preliminary risk assessment models should be used to detect pesticides posing possible or definite risks, whereafter more detailed chemical, toxicological and biological monitoring assessments should be performed if risks are predicted.
    Microtopography as a driving mechnism for ecohydrological processes in shallow groundwater systems
    Ploeg, M.J. van der; Appels, W.M. ; Cirkel, D.G. ; Oosterwoud, M.R. ; Witte, J.P.M. ; Zee, S.E.A.T.M. van der - \ 2012
    Vadose Zone Journal 11 (2012)3. - ISSN 1539-1663
    acrotelm-catotelm model - peat bog growth - hydraulic conductivity - blanket peat - surface-water - micro-topography - flow - vegetation - runoff - infiltration
    Microtopography can have a large effect on flow processes at the soil surface and the composition of soil water. Microtopography is often represented by a roughness parameter in hydrological models. In areas without a strong topographical gradient, microtopography may be underestimated when accumulated in a single parameter, especially in shallow groundwater systems. This study reviews the intricate relationships between microtopography, surface runoff, and ecohydrology in systems featuring shallow water tables. We specifically focus on relations between microtopography and runoff, impact of microtopography on response times of shallow groundwater ecosystems, and microtopography and spatial distribution of groundwater quality parameters and site factors. We advocate the use of microtopography in modeling approaches by examples that feature typical ecosystems with shallow groundwater under influence of microtopography. With a simple modeling approach, we show how microtopography could add flexibility to the acrotelm–catotelm concept in raised bog hydrology. The classic acrotelm–catotelm concept hinders progress in understanding small scale hydrological variations and other ecohydrological relations. Furthermore, we illustrate possible self-organization properties of wetlands. Finally, we show how microtopography and surface runoff affect the mixing of water with different chemical signatures, resulting in variations of the occurrence of plant species.
    A novel method to determine buffer strip effectiveness on deep soils
    Heinen, M. ; Noij, I.G.A.M. ; Heesmans, H.I.M. ; Groenigen, J.W. van; Groenendijk, P. ; Thissen, J.T.N.M. - \ 2012
    Journal of Environmental Quality 41 (2012)2. - ISSN 0047-2425 - p. 334 - 347.
    vegetative filter strips - (h2o)-o-18 transport model - nonpoint-source pollution - stream riparian zones - shallow ground-water - stable-isotope hdo - nitrogen removal - nitrate removal - surface-water - agricultural watersheds
    Unfertilized buffer strips (BS) generally improve surface water quality. High buffer strip effectiveness (BSE) has been reported for sloping shallow aquifers, but experimental data for plain landscapes with deeply permeable soils is lacking. We tested a novel method to determine BSE on a 20-m-deep, permeable sandy soil. Discharge from soil to ditch was temporarily collected in an in-stream reservoir to measure its quantity and quality, both for a BS and a reference (REF) treatment. Treatments were replicated once for the first, and three times for the next three leaching seasons. No significant BSE was obtained for nitrogen and phosphorus species in the reservoirs. Additionally, water samples were taken from the upper groundwater below the treatments. The effect of BS for nitrate was much bigger in upper groundwater than in the reservoirs that also collected groundwater from greater depths that were not influenced by the treatments. We conclude that measuring changes in upper groundwater to assess BSE is only valid under specific hydrogeological conditions. We propose an alternative experimental set-up for future research, including extra measurements before installing the BS and REF treatments to deal with spatial and temporal variability. The use of such data as covariates will increase the power of statistical tests by decreasing between-reservoir variability.
    Influence of natural organic matter on the screening of pharmaceuticals in water by using liquid chromatography with full scan mass spectrometry
    Herrera Rivera, Z.E. ; Oosterink, J.E. ; Rietveld, L. ; Schoutsen, F. ; Stolker, A.A.M. - \ 2011
    Analytica Chimica Acta 700 (2011)1-2. - ISSN 0003-2670 - p. 114 - 125.
    surface-water - identification - antibiotics - contaminants - residue - samples - ms
    The influence of natural organic matter on the screening of pharmaceuticals in water was determined by using high resolution liquid chromatography (HRLC) combined with full scan mass spectrometry (MS) techniques like time of flight (ToF) or Orbitrap MS. Water samples containing different amount of natural organic matter (NOM) and residues of a set of 11 pharmaceuticals were analyzed by using Exactive Orbitrap (TM) LC-MS. The samples were screened for residues of pharmaceuticals belonging to different classes like benzimidazoles, macrolides, penicillins, quinolones, sulfonamides, tetracyclines, tranquillizers, non-steroidal anti-inflammatory drugs (NSAIDs), anti-epileptics and lipid regulators. The method characteristics were established over a concentration range of 0.1-500 mu g L(-1). The 11 pharmaceuticals were added to two effluent and two influent water samples. The NOM concentration within the samples ranged from 2 to 8 mg L(-1) of dissolved organic carbon. The HRLC-Exactive Orbitrap (TM) LC-MS system was set at a resolution of 50,000 (FWHM) and this selection was found sufficient for the detection of the list of pharmaceuticals. With this resolution setting, accurate mass measurements with errors below 2 ppm were found, despite of the NOM concentration of the different types of water samples. The linearities were acceptable with correlation coefficients greater than 0.95 for 30 of the 51 measured linearities. The limit of detection varies between 0.1 mu g L(-1) and 100 mu g L(-1). It was demonstrated that sensitivity could be affected by matrix constituents in both directions of signal reduction or enhancement. Finally it was concluded that with direct shoot method used (no sample pretreatment) all compounds, were detected but LODs depend on matrix-analyte-concentration combination. No direct relation was observed between NOM concentration and method characteristics. For accurate quantification the use of internal standards and/or sample clean-up is necessary. The direct shoot method is only applicable for qualitative screening purposes. The use of full scan MS makes it possible to search for unknown contaminants. With the use of adequate software and a database containing more than 50,000 entries a tool is available to search for unknowns.
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