Dear Colleagues,

Atmospheric dispersion is the indispensable physical process for understanding and regulating airborne pollutants. It has become the focus of researchers and governmental agencies regarding the protection of public health and welfare.

Regarding regulatory purposes, people investigate the atmospheric dispersion of pollutants (including SO₂, NOx, particulate matter, odor, and bioaerosols) emitted from key sources, e.g., industrial parks, airports, power plants, and farms. The information about the contributions of key sources to ambient pollution is of great importance to implement effective measures to alleviate the associated impacts.

Atmospheric dispersion is also of great concern during emergencies, e.g., the Fukushima Daiichi power plant accident, the volcano eruption of Eyjafjallajökull, and accidental releases of hazardous material. The atmospheric dispersion of hazardous materials, e.g., radioactive pollutants, volcanic ash, and toxic and explosive gases, is essential information for planning accurate countermeasures, e.g., sheltering, evacuation, and iodine-prophylaxis.

This Special Issue is devoted to all theoretical, modeling, and observational aspects of the atmospheric dispersion of pollutants from the key emission sources for regulatory purposes, and applications in accidental releases for emergency management. Both measurements and numerical modeling studies are welcome.

The topics of interest of this Special Issue include but are not limited to in situ and remote sensing measurements of atmospheric dispersion of pollutants, development of emission inventory, parameterization of meteorological processes related to atmospheric dispersion, atmospheric dispersion models at various scales (from local to continental scale), exposure assessment, data assimilation, and inverse modeling.

Dr. Xiaole Zhang
Guest Editor

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• atmospheric dispersion of pollutants
• atmospheric dispersion models
• in situ and remote sensing
• emission inventory
• data assimilation
• inverse modeling
• regulatory purposes
• emergency response

Title: A Potential Machine Learning Approach to Update Air Pollutants Emission Inventory Using Observed Surface Concentrations and Meteorology for Air Quality Modeling
Authors: Saloni Vijay¹, Xiaoxiao Feng^1,2 and Xiaole Zhang^1,2 Jing Wang^1,2,*
Affiliation: 1. Institute of Environmental Engineering (IfU), ETH Zürich, Zürich, 8093, Switzerland; 2. Swiss Federal Laboratories for Materials Science and Technology, Dübendorf 8600, Switzerland;
Abstract: Emission inventories provide indispensable information in predicting air pollution. However, the emission inventories have large bias from the reality, and the simulated ambient air concen-trations of the pollutants differed from their respective surface observations. A top-down method was thus used to update the baseline inventory. The rule guiding the relationship between the simulated ambient air concentrations and meteorology with the emissions was first learned with the algorithm of random forest. The baseline emission inventory was updated by replacing the simulated ambient air concentration with the observed concentrations. The updated inventory of all 4 pollutants showed more temporal variations for both weekends and weekdays, compared to almost time-static baseline inventory. The performance of predicting pollutants was improved by 10%, 19%, 20%, and 15% for ambient PM10, PM2.5, SO2, and NO2, respectively with the updated emissions. The top-down methodology developed can be extended to update daily emissions in other regions of the world, provided further optimization of the machine learning algorithm.

Title: Choosing the appropriate atmospheric dispersion model, from theoretical to application considerations for accidental situations
Authors: B Truchot, L Joubert and O gentilhomme
Affiliation: Ineris, French National Institute for Industrial Environment and Risks, Parc Technologique Alata BP 2, 60550 Verneuil-en-Halatte, France
Abstract: Toxic or flammable atmospheric releases on industrial facilities can lead to huge consequences for human beings and the environment. Predicting those consequences remains nowadays a challenge for several professionals, from industrial safety engineer during the design process to emergency services during the crisis management. Hopefully, many numerical models are available and can be used for these objectives. However, atmospheric flows are highly specific and such a modelling approach is not so obvious. Many model families exist, from simple Gaussian correlation to CFD (Computational Fluid Dynamics) codes. All approaches got their own advantages and drawbacks and attention should be paid when selecting the most relevant one. As a guideline, this paper presents the different family models in such a way that it will allow the reader to identify the limitations and prerequisite for each of them. Using some examples, this article also provides some validation cases and uncertainties evaluation that can be usefull for all users. The nature of the release and associated target is also discussed since looking for very long distance for dispersion as for the smoke resulting from the Lubrizol/Normandie Logistique fire or looking for flammable zone sizing improvement do not have the same constraints. The discussion is not only focused on the physical and theoretical approaches of each family model but also considers the constraints of each of them keeping in mind that, in emergency situation, the time scale and uncertainty acceptance are strongly different from those at the design stage.

Title: Experimental campaign of CO2 massive atmospheric releases in an urban area
Authors: L. Joubert; G. Leroy; T. Claude
Affiliation: French National Institute for Industrial Environment and Risks, Parc Technologique Alata BP 2, 60550 Verneuil-en-Halatte, France
Abstract: Over the last decades, several campaigns were carried out to collect data regarding releases and atmospheric dispersion of dense chemical products in an open field. All these experimental data are valuable information to challenge the predictions of numerical tools (gaussian, integral-type and CFD tools) and, if needed, to improve the code itself and the way we are using it. On the other hand, little attention has been paid to atmospheric dispersion releases with massive flow rates in a complex urban environment. To fill this gap, Ineris launched an experimental campaign intended to study atmospheric dispersion of massive CO2 releases on the Cenzub site (action training center in urban area located in Sissonne, France). Three CO2 releases were performed with mass flowrates between 8 and 10 kg/s in three different configurations: one axial street release and two impacting releases (against a small and high-rise building). Several technologies of CO2 sensors were used to ensure a better measurement accuracy. Main experimental campaign features and preliminary data analysis is presented.