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“Atmospheric nitrogen fluxes at the Belgian coast: 2004-2006”. Bencs L, Krata A, Horemans B, Buczyńska AJ, Dirtu AC, Godoi AFL, Godoi RHM, Potgieter-Vermaak S, Van Grieken R, Atmospheric environment : an international journal 43, 3786 (2009). http://doi.org/10.1016/J.ATMOSENV.2009.04.002
Abstract: Daily and seasonal variations in dry and wet atmospheric nitrogen fluxes have been studied during four campaigns between 2004 and 2006 at a coastal site of the Southern North Sea at De Haan (Belgium) located at coordinates of 51.1723° N and 3.0369° E. Concentrations of inorganic N-compounds were determined in the gaseous phase, size-segregated aerosol (coarse, medium, and fine), and rainwater samples. Dissolved organic nitrogen (DON) was quantified in rainwater. The daily variations in N-fluxes of compounds were evaluated with air-mass backward trajectories, classified into the main air-masses arriving at the sampling site (i.e., continental, North Sea, and Atlantic/UK/Channel). The three, non-episodic campaigns showed broadly consistent fluxes, but during the late summer campaign exceptionally high episodic N-deposition was observed. The average dry and wet fluxes for non-episodic campaigns amounted to 2.6 and 4.0 mg N m−2 d−1, respectively, whereas during the episodic late summer period these fluxes were as high as 5.2 and 6.2 mg N m−2 d−1, respectively. Non-episodic seasons/campaigns experienced average aerosol fluxes of 0.91.4 mg N m−2 d−1. Generally, the contribution of aerosol NH4+ was more significant in the medium and fine particulate fractions than that of aerosol NO3−, whereas the latter contributed more in the coarse fraction, especially in continental air-masses. During the dry mid-summer campaign, the DON contributed considerably (15%) to the total N-budget. Exceptionally high episodic aerosol-N inputs have been observed for the late summer campaign, with especially high deposition rates of 3.6 and 2.9 mg N m−2 d−1 for Atlantic/UK/Channel and North Sea-continental (mixed) air-masses, respectively. During this pollution episode, the flux of NH4+ was dominating in each aerosol fraction/air-mass, except for coarse continental aerosols. High deposition of gaseous-N was also observed in this campaign with an average total N-flux of 22.5-times higher than in other campaigns.
Keywords: A1 Journal article; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
DOI: 10.1016/J.ATMOSENV.2009.04.002
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“Inferring episodic atmospheric iron fluxes in the Western South Atlantic”. Evangelista H, Maldonado J, dos Santos EA, Godoi RHM, Garcia CAE, Garcia VMT, Johnson E, da Cunha KD, Leite CB, Van Grieken R, van Meel K, Makarovska Y, Gaiero DM, Atmospheric environment : an international journal 44, 703 (2010). http://doi.org/10.1016/J.ATMOSENV.2009.11.018
Abstract: Iron (Fe) and other trace elements such as Zn, Mn, Ni and Cu are known as key-factors in marine biogeochemical cycles. It is believed that ocean primary productivity blooms in iron deficient regions can be triggered by iron in aeolian dust. Up to now, scarce aerosol elemental composition, based on measurements over sea at the Western South Atlantic (WSA), exist. An association between the Patagonian semi-desert dust/Fe and chlorophyll-a variability at the Argentinean continental shelf is essentially inferred from models. We present here experimental data of Fe enriched aerosols over the WSA between latitudes 22°S62°S, during 4 oceanographic campaigns between 2002 and 2005. These data allowed inferring the atmospheric Fe flux onto different latitudinal bands which varied from 30.4 to 1688 nmolFe m−2 day−1 (October 29thNovember 15th, 2003); 5.831586 nmolFe m−2 day−1 (February 15thMarch 6th, 2004) and 4.73586 nmolFe m−2 day−1(October 21stNovember 5th, 2005).
Keywords: A1 Journal article; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
DOI: 10.1016/J.ATMOSENV.2009.11.018
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“Speciation and diurnal variation of thoracic, fine thoracic and sub-micrometer airborne particulate matter at naturally ventilated office environments”. Horemans B, Van Grieken R, Atmospheric environment : an international journal 44, 1497 (2010). http://doi.org/10.1016/J.ATMOSENV.2010.01.010
Abstract: Thoracic (PM10), fine thoracic (PM2.5) and sub-micrometer (PM1) airborne particulate matter was sampled during day and night. In total, about 100 indoor and outdoor samples were collected for each fraction at ten different office environments. Energy-dispersive X-ray fluorescence spectrometry and ion chromatography were applied for the quantification of some major and minor elements and ions in the collected aerosols. During daytime, mass concentrations were in the ranges: 1129, 8.124, and 6.618 μg m−3, with averages of 20 ± 1, 15.0 ± 0.9, and 11.0 ± 0.8 μg m−3, respectively. At night, mass concentrations were found to be significantly lower for all fractions. Indoor PM1 concentrations exceeded the corresponding outdoor levels during office hours and were thought to be elevated by office printers. Particles with diameters between 1 and 2.5 μm and 2.5 and 10 μm were mainly associated with soil dust elements and were clearly subjected to distinct periods of settling/resuspension. Indoor NO3 − levels were found to follow specific microclimatic conditions at the office environments, while daytime levels of sub-micrometer Cl− were possibly elevated by the use of Cl-containing cleaning products. Indoor carbon black concentrations were sometimes as high as 22 μg m−3 and were strongly correlated with outdoor traffic conditions.
Keywords: A1 Journal article; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
DOI: 10.1016/J.ATMOSENV.2010.01.010
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“Chemkar PM10 : an extensive look at the local differences in chemical composition of PM10 in Flanders, Belgium”. Vercauteren J, Matheeussen C, Wauters E, Roekens E, Van Grieken R, Krata A, Makarovska Y, Maenhaut W, Chi X, Geypens B, Atmospheric environment : an international journal 45, 108 (2011). http://doi.org/10.1016/J.ATMOSENV.2010.09.040
Abstract: The results of Chemkar PM10, the first large scale chemical characterisation project of PM10 in Flanders are presented. Between September 2006 and September 2007 a total of 365 PM10 samples were collected by sampling every sixth day at six different sites in Flanders (Belgium) varying in character from urban background to rural. Samples were analysed for a series of elements, elemental and organic carbon, 13C/12C- and 15N/14N-isotopic ratios, and water-soluble ions. At three sites extra sampling was carried out to determine PAHs by means of a novel technique that uses sorption tubes consisting of polydimethylsiloxane (PDMS) foam, PDMS particles and a TENAX TA bed. Results showed that the most important fractions were secondary inorganic ions (nitrate, sulphate and ammonium): 41% (12.6 μg m−3), organic matter: 20% (6.1 μg m−3), crustal matter: 14% (4.3 μg m−3), sea salt: 8% (2.4 μg m−3) and elemental carbon: 4% (1.2 μg m−3). Although the general composition profile was rather similar for the six sites, substantial differences could be observed for some main components and for several trace metals such as chromium, copper, zinc, arsenic and lead. Although the average sum of the PAH 16 was quite variable between the three sites (between 132 and 248 ng m−3) the average sum of the PAH 7 was between 7 and 9 ng m−3 for the three sites. The largest relative differences between sites were found for elemental carbon and crustal matter, thereby indicating that there is some potential for local measures to reduce the concentrations of particulate matter by a few μg m−3. Both for carbon and nitrogen isotopic ratios significant differences in time were observed. Isotopic differences in location could only be detected for carbon.
Keywords: A1 Journal article; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
DOI: 10.1016/J.ATMOSENV.2010.09.040
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“Quantifying inflow uncertainties in RANS simulations of urban pollutant dispersion”. García Sánchez C, Van Tendeloo G, Gorle C, Atmospheric environment : an international journal 161, 263 (2017). http://doi.org/10.1016/J.ATMOSENV.2017.04.019
Abstract: Numerical simulations of flow and pollutant dispersion in urban environments have the potential to support design and policy decisions that could reduce the population's exposure to air pollution. Reynolds-averaged Navier-Stokes simulations are a common modeling technique for urban flow and dispersion, but several sources of uncertainty in the simulations can affect the accuracy of the results. The present study proposes a method to quantify the uncertainty related to variability in the inflow boundary conditions. The method is applied to predict flow and pollutant dispersion in downtown Oklahoma City and the results are compared to field measurements available from the Joint Urban 2003 measurement campaign. Three uncertain parameters that define the inflow profiles for velocity, turbulence kinetic energy and turbulence dissipation are defined: the velocity magnitude and direction, and the terrain roughness length. The uncertain parameter space is defined based on the available measurement data, and a non-intrusive propagation approach that employs 729 simulations is used to quantify the uncertainty in the simulation output. A variance based sensitivity analysis is performed to identify the most influential uncertain parameters, and it is shown that the predicted tracer concentrations are influenced by all three uncertain variables. Subsequently, we specify different probability distributions for the uncertain inflow variables based on the available measurement data and calculate the corresponding means and 95% confidence intervals for comparison with the field measurements at 35 locations in downtown Oklahoma City. (C) 2017 Elsevier Ltd. All rights reserved.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 3.629
Times cited: 17
DOI: 10.1016/J.ATMOSENV.2017.04.019
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“CFD modelling of small particle dispersion: the influence of the turbulence kinetic energy in the atmospheric boundary layer”. Gorlé, C, van Beeck J, Rambaud P, Van Tendeloo G, Atmospheric environment : an international journal 43, 673 (2009). http://doi.org/10.1016/j.atmosenv.2008.09.060
Abstract: When considering the modelling of small particle dispersion in the lower part of the Atmospheric Boundary Layer (ABL) using Reynolds Averaged Navier Stokes simulations, the particle paths depend on the velocity profile and on the turbulence kinetic energy, from which the fluctuating velocity components are derived to predict turbulent dispersion. It is therefore important to correctly reproduce the ABL, both for the velocity profile and the turbulence kinetic energy profile. For RANS simulations with the standard kå model, Richards and Hoxey (1993. Appropriate boundary conditions for computational wind engineering models using the kå turbulence model. Journal of Wind Engineering and Industrial Aerodynamics 4647, 145153.) proposed a set of boundary conditions which result in horizontally homogeneous profiles. The drawback of this method is that it assumes a constant profile of turbulence kinetic energy, which is not always consistent with field or wind tunnel measurements. Therefore, a method was developed which allows the modelling of a horizontally homogeneous turbulence kinetic energy profile that is varying with height. By comparing simulations performed with the proposed method to simulations performed with the boundary conditions described by Richards and Hoxey (1993. Appropriate boundary conditions for computational wind engineering models using the kå turbulence model. Journal of Wind Engineering and Industrial Aerodynamics 4647, 145153.), the influence of the turbulence kinetic energy on the dispersion of small particles over flat terrain is quantified.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 3.629
Times cited: 79
DOI: 10.1016/j.atmosenv.2008.09.060
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“Stack gas dispersion measurements with large scale-PIV, aspiration probes and light scattering techniques and comparison with CFD”. Nakiboglu G, Gorlé, C, Horvath I, van Beeck J, Blocken B, Atmospheric environment : an international journal 43, 3396 (2009). http://doi.org/10.1016/j.atmosenv.2009.03.047
Abstract: The main purpose of this research is to manage simultaneous measurement of velocity and concentration in large cross-sections by recording and processing images of cloud structures to provide more detailed information for e.g. validation of CFD simulations. Dispersion from an isolated stack in an Atmospheric Boundary Layer (ABL) was chosen as the test case and investigated both experimentally and numerically in a wind tunnel. Large Scale-Particle Image Velocimetry (LS-PIV), which records cloud structures instead of individual particles, was used to obtain the velocity field in a vertical plane. The concentration field was determined by two methods: Aspiration Probe (AP) measurements and Light Scattering Technique (LST). In the latter approach, the same set of images used in the LS-PIV was employed. The test case was also simulated using the CFD solver FLUENT 6.3. Comparison between AP measurements and CFD revealed that there is good agreement when using a turbulent Schmidt number of 0.4. For the LST measurements, a non-linear relation between concentration and light intensity was observed and a hyperbolic-based function is proposed as correction function. After applying this correction function, a close agreement between CFD and LST measurements is obtained. (C) 2009 Elsevier Ltd. All rights reserved.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 3.629
Times cited: 15
DOI: 10.1016/j.atmosenv.2009.03.047
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