2205 resultaten

  • GLOBIO-Aquatic, a global model of human impact on the biodiversity of inland aquatic ecosystems

    Auteurs: Janse, J.H.; Jeuken, M.H.J.L. (2015)
    Gepubliceerd in: Environmental science and policy, volume 48 (2015), pagina 99-114

    Biodiversity in freshwater ecosystems is undergoing rapid global decline. Major drivers are land use change, eutrophication, hydrological disturbance, climate change, overexploitation and invasive species. We developed a global model for assessing the dominant human impacts on inland aquatic biodiversity. The system consists of a biodiversity model, named GLOBIO-Aquatic, that is embedded in the IMAGE model framework, i.e. linked to models for demography, economy, land use changes, climate change, nutrient emissions, a global hydrological model and a global map of water bodies. The biodiversity model is based on a recompilation of existing data, thereby scaling-up from local/regional case-studies to global trends. We compared species composition in impacted lakes, rivers and wetlands to that in comparable undisturbed systems. We focussed on broad categories of human-induced pressures that are relevant at the global scale. The drivers currently included are catchment land use changes and nutrient loading affecting water quality, and hydrological disturbance and climate change affecting water quantity. The resulting relative mean abundance of original species is used as indicator for biodiversity intactness. For lakes, we used dominance of harmful algal blooms as an additional indicator. The results show that there is a significant negative relation between biodiversity intactness and these stressors in all types of freshwater ecosystems. In heavily used catchments, standing water bodies would lose about 80% of their biodiversity intactness and running waters about 70%, while severe hydrological disturbance would result in losses.

  • Future water quality monitoring : adapting tools to deal with mixtures of pollutants in water resource management

    Auteurs: Altenburger, R.; Gils, J.A.G. van (2015)
    Gepubliceerd in: Science of the total environment, volume 512-513 (2015), pagina 540-551

  • Improved time-lapse electrical resistivity tomography monitoring of dense non-aqueous phase liquids with surface-to-horizontal borehole arrays

    Auteurs: Power, C.; Karaoulis, M. (2015)

    Electrical resistivity tomography (ERT) has long-standing potential to improve characterization of sites contaminated with dense non-aqueous phase liquids (DNAPLs). However, ERT is rarely used at DNAPL sites due to the complexity of the DNAPL target coupled with the inherent limitations of traditional (surface and cross-hole) ERT configurations. Horizontal boreholes are being increasingly used in remedial strategies at contaminated field sites. This paper presents a novel surface-to-horizontal borehole (S2HB) ERT configuration for DNAPL site investigations. This array configuration is combined with four-dimensional (4D) inversion methods (applied on two-dimensional (2D) time-lapse monitoring datasets) to explore the potential benefit of S2HB ERT for mapping the spatial and temporal evolution of DNAPL mass during remediation. A field scale DNAPL remediation scenario was first simulated by a coupled DNAPL-ERT model. This demonstrated that S2HB ERT may provide significant improvements over surface ERT, particularly for delineating DNAPL mass removal at depth. A laboratory experiment was then performed to validate the S2HB ERT approach in a physical system. The experiment confirmed that 4D S2HB ERT provides improved time-lapsemonitoring of NAPL changes. Confidence in the ERT responses obtained fromthe experiment was increased by direct comparison to the actual distribution of NAPL mapped by excavation. Independent simulation of the experiment with the DNAPL-ERT model demonstrated that the model is reliable for simulating real systems. This initial study demonstrates significantly improved resistivity imaging with surface-to-horizontal borehole ERT and its potential as a non-destructive site characterization tool for mapping DNAPL mass changes during remediation.

  • Planning support system for climate adaptation : composing effective sets of blue-green measures to reduce urban vulnerability to extreme weather events

    Auteurs: Voskamp, I.M.; Ven, F.H.M. van de (2015)
    Gepubliceerd in: Building and environment, volume 83 (2015), pagina 159-167

    The risk of pluvial flooding, heat stress and drought is increasing due to climate change. To increase urban resilience to extreme weather events, it is essential to combine green and blue infrastructure and link enhanced storage capacity in periods of water surplus with moments of water shortage as well as ater availability with heat stress. ‘Blue-green measures’ is a collective term for sustainable green and blue infrastructure that utilises underlying ecosystem functions to deliver multiple benefits: for example, cooling via evapotranspiration, water storage for heavy rainfall events, discharge peak attenuation, seasonal water storage, and groundwater recharge. Measures contribute most to climate adaptation when implemented in combinations. Such packages of blue-green measures capitalize upon the synergistic interactions between ecosystem functions and hence enhance multiple vulnerability reduction capacities. Moreover, combining blue-green measures enables using their unique potential at different spatial scales and establishing hydrologic connectivity. This paper proposes a framework for a planning support system and a tool to select adaptation measures to support urban planners in collaboratively finding site-specific sets of blue-green measures for a particular urban reconstruction project. With the proposed framework users can evaluate appropriateness of specific adaptation measures for a particular location and compose effective packages of blue-green measures to handle flooding, drought and heat stress. It is concluded that the framework: 1) enables incorporating knowledge on urban climate adaptation and ecosystem services in a communicative urban planning process; 2) guides the selection of a coherent and effective package of blue-green adaptation measures.

  • Experiment inspired numericalmodeling of sediment concentration over sand–silt mixtures

    Auteurs: Yao, P.; Wang, Z.B.; Rijn, L.C. van (2015)
    Gepubliceerd in: Coastal engineering : an international journal for coastal, harbour and offshore engineers, volume 105 (2015), pagina 75-89

    A series of flume experiments has been conducted to investigate sediment transport of sand-silt mixtures in both wave-only and wave-with-current conditions. Two types of sediments collected from a typical silty tidal flat were used: a silt-sized mixture with median grain size of 46 μm, and a very fine sand-sized mixture with median grain size of 88 μm. A high concentration layer (HCL)was observed near the bottom together with ripples underwave only conditions. Sediment concentrations inside the HCL are quasi-stationary with the bulk Richardson number approaching a constant value. The thickness of the HCL can be scaled with approximately two times the damped wave boundary layer thickness. For the concentration profiles, we find that the vertical profile of the silt concentration appears different from the profile of the sand concentration, since the silt concentration decreases logarithmically within HCL, while homogeneously distributes outside the HCL. Finally, the reference concentration formulation of van Rijn (2007) was recalibrated for the silt classes and applied in a multi-fraction model to predict the vertical concentration profile for silt and sand classes. The results show a promising agreement with the measurements, for both wave-only and wave-with-current conditions.

  • The SOLUTIONS project : challenges and responses for present and future emerging pollutants in land and water resources management

    Auteurs: Brack, W.; Gils, J.A.G. van (2015)
    Gepubliceerd in: Science of the total environment, volume 503-504 (2015), pagina 22-31

    SOLUTIONS (2013 to 2018) is a European Union Seventh Framework Programme Project (EU-FP7). The project aims to deliver a conceptual framework to support the evidence-based development of environmental policies with regard to water quality. SOLUTIONS will develop the tools for the identification, prioritisation and assessment of thosewater contaminants that may pose a risk to ecosystems and human health. To this end, a new generation of chemical and effect-based monitoring tools is developed and integrated with a full set of exposure, effect and risk assessment models. SOLUTIONS attempts to address legacy, present and future contamination by integrating monitoring and modelling based approaches with scenarios on future developments in society, economy and technology and thus in contamination. The project follows a solutions-oriented approach by addressing major problems of water and chemicals management and by assessing abatement options. SOLUTIONS takes advantage of the access to the infrastructure necessary to investigate the large basins of the Danube and Rhine as well as relevant Mediterranean basins as case studies, and puts major efforts on stakeholder dialogue and support. Particularly, the EU Water Framework Directive (WFD) Common Implementation Strategy (CIS) working groups, International River Commissions, and water works associations are directly supported with consistent guidance for the early detection, identification, prioritisation, and abatement of chemicals in the water cycle. SOLUTIONS will give a specific emphasis on concepts and tools for the impact and risk assessment of complex mixtures of emerging pollutants, their metabolites and transformation products. Analytical and effect-based screening tools will be applied together with ecological assessment tools for the identification of toxicants and their impacts. The SOLUTIONS approach is expected to provide transparent and evidence based candidates or River Basin Specific Pollutants in the case study basins and to assist future review of priority pollutants under the WFD as well as potential abatement options.

  • The plumbing system of the Pagosa thermal Springs, Colorado : application of geologically constrained geophysical inversion and data fusion

    Auteurs: Revil, A.; Karaoulis, M. (2015)
    Gepubliceerd in: Journal of volcanology and geothermal research, volume 299 (2015), pagina 1-18

    Fault and fracture networks usually provide the plumbing for movement of hydrothermal fluids in geothermal fields. The Big Springs of Pagosa Springs in Colorado is known as the deepest geothermal hot springs in the world. However, little is known about the plumbing system of this hot spring, especially regarding the position of the reservoir (if any) or the position of the major tectonic faults controlling the flow of the thermal water in this area. The Mancos shale, a Cretaceous shale, dominates many of the surface expressions around the springs and impede an easy recognition of the fault network. We use three geophysical methods (DC resistivity, self-potential, and seismic) to image the faults in this area, most of which are not recognized in the geologic fault map of the region. Results from these surveys indicate that the hot Springs (the Big Spring and a warm spring located 1.8 km further south) are located at the intersection of the Victoire Fault, a major normal crustal fault, and two north-northeast trending faults (Fault A and B). Self-potential and DC resistivity tomographies can be combined and a set of joint attributes defined to determine the localization of the flow of hot water associated with the Eight Miles Mesa Fault, a second major tectonic feature responsible for the occurrence of warm springs further West and South from the Big Springs of Pagosa Springs.

  • Storm overwash of a gravel barrier : field measurements and XBeach-G modelling

    Auteurs: Almeida, L.P.; Masselink, G.; McCall, R.; Russell, P. ()
    Gepubliceerd in: Coastal engineering : an international journal for coastal, harbour and offshore engineers, volume 120 (2017), pagina 22-23

    Gravel barriers provide a natural form of coastal protection and flood defence for many sites around the UK and worldwide. Predicting their vulnerability to different storm impact regimes that cause overtopping and overwash is crucial as these processes can lead to hazardous consequences such as inundation of the back of the barrier or breaching. This paper presents the first field measurements of storm overwash events on a gravel beach (Loe Bar, Cornwall, England). High frequency in-situ observations (2 Hz) were performed using a 2D laser-scanner and allowed a complete characterization of the overwash flows (velocity and depth) and morphological response along a cross-shore section of the barrier. These novel measurements are used to validate the numerical model XBeach-G, to forecast overwash discharge. Several simulations were performed with XBeach-G to investigate the thresholds for the different storm impact regimes, given a variety of water levels and wave heights. Wave period and wave spectral shape are found to significantly affect these thresholds. While short period waves dissipate most of their energy by breaking before reaching the swash zone and produce short runup excursions, long period waves due to their low steepness arrive at the swash zone unbroken with enhanced heights (due to shoaling) thus promoting large runup excursions. When the offshore wave spectrum has a bimodal shape, wave transformation in shallow water causes the long period peak to dominate the swash giving large runup excursions. Long period waves or strongly bimodal waves result in enhanced runup thereby reducing the thresholds for barrier overtopping or overwashing.

  • Effects of clay minerals, hydroxides, and timing of dissolved organic matter addition on the competitive sorption of copper, nickel, and zinc : a column experiment

    Auteurs: Refaey, Y.; Markus, A.A. (2016)

    Infiltration of heavy metal (HM) polluted wastewater can seriously compromise soil and groundwater quality. Interactions between mineral soil components (e.g. clay minerals) and dissolved organic matter (DOM) play a crucial role in determining HM mobility in soils. In this study, the influence of the timing of addition of DOM, i.e. concurrent with or prior to HMs, on HM mobility was explored in a set of continuous flow column experiments using well defined natural soil samples amended with goethite, birnessite and/or smectite. The soils were subjected to concurrent and sequential additions of solutions of DOM, and Cu, Ni and Zn. The resulting breakthrough curves were fitted with a modified dose-response model to obtain the adsorption capacity (q0). Addition of DOM prior to HMs moderately enhanced q0 of Cu (8–25%) compared to a control without DOM, except for the goethite amended soil that exhibited a 10% reduction due to the blocking of binding sites. Meanwhile, for both Zn and Ni sequential addition of DOM reduced q0 by 1–36% for all tested soils due to preferential binding of Zn and Ni to mineral phases. In contrast, concurrent addition of DOM and HMs resulted in a strong increase of q0 for all tested metals and all tested soil compositions compared to the control: 141–299% for Cu, 29–102% for Zn and 32–144% for Ni. Our study shows that when assessing the impact of soil pollution through HM containing wastewater it is crucial to take into account the presence of DOM.

  • Methods to identify outliers in repetitions of UV/Vis spectra

    Auteurs: Lepot, M.; Masic, A.; Aubin, J.; Clemens, F.H.L.R. ()

    UV/Vis spectrophotometers have been used to monitor water quality since the early 2000s. Calibration of these devices requires sampling campaigns to elaborate relations between recorded spectra and measured concentrations. Recent sensor improvements allow recordings of a spectrum in as little as 15 seconds, making it possible to record several spectra for the same sample. Spectrum repetitions provide new opportunities to detect outliers, a task that is difficult in non-repetitive spectra recordings. A well-executed outlier detection can e.g. result in a more accurate calibration of the spectrophotometer or an improved construction of a regression model. In this work, two methods are presented and tested to detect outliers in repetitions of spectral data: one based on data depth theory (DDT) and one on principal component analysis (PCA). Results show that the two methods are generally consistent in identifying outliers, with only small differences between the methods.

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