On the individual exposure from airborne hazardous releases: The effect of atmospheric turbulence
University of Western Macedonia, Department of Engineering and Management of Energy Resources, Sialvera & Bakola Str., 50100 Kozani, Greece.Journal of Hazardous Materials (Impact Factor: 4.53). 02/2008; 150(1):76-82. DOI: 10.1016/j.jhazmat.2007.04.078
One of the key problems in coping with deliberate or accidental atmospheric releases is the ability to reliably predict the individual exposure during the event. Furthermore, for the implementation of countermeasures, it is essential to predict the maximum expected dosage and the exposure time within which the dosage exceeds certain health limits. Current state of the art methods, which are based on the concentration cumulative distribution function (cdf) and require the knowledge of the concentration variance and the intermittency factor, have certain limitations especially when the exposure time becomes comparable with the peak spectral time. The proposed method aims at estimating maximum dosage as a function of the exposure time, mean concentration and the turbulence integral time scale. It is much simpler than the cdf models and it poses no restrictions on the exposure time length. One of the important consequences is that it can broaden the capability of the ensemble average computational models to estimate maximum dosage for any exposure time. The method has been tested successfully utilizing the ammonia field experiments FLADIS T16 and T17.
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- "This reduces the problem of C max () estimation to b parameter estimation. The decision of fixing the value is based on the experimental evidence of relatively mild variability . On the other hand any variability of will be absorbed on further variability of the b parameter. "
ABSTRACT: A key issue, in order to be able to cope with deliberate or accidental atmospheric releases of hazardous substances, is the ability to reliably predict the individual exposure downstream the source. In many situations, the release time and/or the health relevant exposure time is short compared to mean concentration time scales. In such a case, a significant scatter of exposure levels is expected due to the stochastic nature of turbulence. The problem becomes even more complex when dispersion occurs over urban environments. The present work is the first attempt to approximate on generic terms, the statistical behavior of the abovementioned variability with a beta distribution probability density function (beta-pdf) which has proved to be quite successful. The important issue of the extreme concentration value in beta-pdf seems to be properly addressed by the  correlation in which global values of its associated constants are proposed. Two substantially different datasets, the wind tunnel Michelstadt experiment and the field Mock Urban Setting Trial (MUST) experiment gave clear support to the proposed novel theory and its hypotheses. In addition, the present work can be considered as basis for further investigation and model refinements. Copyright © 2015 Elsevier B.V. All rights reserved.Journal of hazardous materials 06/2015; 300:182-188. DOI:10.1016/j.jhazmat.2015.06.057 · 4.53 Impact Factor
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- "Formulation of the peak time-averaged concentration equation Following Bartzis et al., (2007) "
ABSTRACT: Abstract: The concentrations fluctuations of a dispersing hazardous gaseous pollutant in the atmospheric boundary layer, and the hazard associated with short-term concentration levels, demonstrate the necessity of estimating the magnitude of these fluctuations using predicting models. Moreover the computation of concentration fluctuations and individual exposure in case of dispersion in realistic situations, such as built-up areas or street canyons, is of special practical interest for hazard assessment purposes. In order to predict or/and estimate the maximum expected dosage and the exposure time within which the dosage exceeds certain health limits, the knowledge of the behaviour of concentration fluctuations at the point under consideration is needed. In this study the whole effort is based on the ‘Mock Urban Setting Test – MUST’, an extensive field test carried out on a test site of the US Army in the Great Basin Desert in 2001 (Biltoft, 2001; Yee, 2004). The experimental data that was used for the model evaluation concerned the dispersion of a passive gas between street canyons which have been created by 120 standard size shipping containers. The computational simulations have been performed using the laboratory CFD code ADREA, which has been developed for simulating the dispersion and exposure of pollutants over complex geometries. The ADREA model is evaluated by comparing the model’s predictions with the observations utilizing statistical metrics and scatter plots. The present study has been performed in the frame of the Action COST 732 “Quality Assurance and Improvement of Micro-Scale Meteorological Models”.
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ABSTRACT: One of the key problems in coping with deliberate or accidental atmospheric releases is the ability to reliably predict the individual exposure during the event. Due to the stochastic nature of turbulence, the instantaneous wind field at the time of the release is practically unknown. Therefore for consequence assessment and countermeasures application, it is more realistic to rely on maximum expected dosage rather than actual one. Recently Bartzis et al. (2007), have inaugurated an approach relating maximum dosage as a function of the exposure time, concentration mean and variance and the turbulence integral time scale. Such approaches broaden the capability of the prediction models such as CFD models to estimate maximum individual exposure at any time interval. In the present work a further insight is given to this methodology and an alternative correlation is proposed based on theoretical considerations. The methodology to utilize such correlation types is further justified.NATO Security through Science Series C: Environmental Security 01/2008; DOI:10.1007/978-1-4020-8453-9_106
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