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Global radionuclide dispersion from Fukushima nuclear accident urged several countries to begin evaluating the radiation effects from neighboring countries. The representative data selection simulation is one of the evaluation methods providing practical results with reasonable computational resources. However, it is mostly used in the domestic radiation effect evaluation. This study investigated and modified this simulation method for transboundary radiation effect evaluation. The effects of selected area boundaries, optional weather parameters, and sampling rate, critical parameters in the representative data selection scheme, are sequentially investigated on the calculated results. The evaluation is performed by Nuclear Accident Consequence Analysis Code (NACAC) with hypothetical accidents at Fangchenggang NPP in China. It is revealed that area boundary and optional weather parameter selection insignificantly impact the predicted results, but the sampling rate condition affects the predicted results. Good agreements comprising dispersion characteristics and total effective dose equivalent by simulation using representative and sequential data selections are shown with absolute mean bias error lower than 2.4 × 10−3 mSv, root mean square error lower than 5.7 × 10−4 mSv, and correlation coefficient value higher than 9.1 × 10−1. [ABSTRACT FROM AUTHOR]

In the early days of nuclear energy in Brazil, a reactor named Argonaut, designed at Argonne National Laboratory, reached criticality at the Institute of Nuclear Engineering (IEN). The presence of a nuclear research facility at the campus of Federal University of Rio de Janeiro is still a cause of concern with regard to the radiological safety of the surrounding community, even though this facility has been securely operating for more than 50 years. In addition, the risk premium paid to IEN workers has also been disputed by the National Office of Account Control. Thus, the aim of this study is to assess the radiological impact and potential risk from Argonaut reactor accidental releases. A recent accident scenario reassessment concluded that severe physical damage of the core after reactor shutdown should be the emergency situation with the greatest potential risk among feasible postulated accidents. The damage caused by failure of a handling crane dropping concrete shielding covers (each weighing 2.5 tons) on the core would lead to breaking of the aluminum coating and the nuclear fuel plates with their release to the reactor hall. This paper evaluates the short-term effective dose rates by inhalation and plume immersion for workers and members of the public, which would be induced by inventory partial release to the atmosphere. The conclusion is that potential risk remains above 1/10 of the limit of annual dose for workers while it stays below the transient levels for members of the public in unrestricted areas. [ABSTRACT FROM AUTHOR]

The prompt and accurate identification of transient pollution sources in urban regions is imperative for effective pollutant control and the mitigation to public health risks. Depending on sparse concentration distributions, multiple pollution sources identification is inherently complex and difficult, particularly when the pollutant sources exhibit time-varying release rates and are located in urban environments subject to dynamic wind flows. In this research, two niche-based Particle Swarm Optimization (PSO) algorithms, Niche-DPSO (niche pso for dynamic systems) and RSNM-DPSO (ranged subgroup pso with nelder mead for dynamic systems), were simultaneously proposed, aiming to localize multiple pollution sources under the background of unsteady wind flow fields. The MUST experiment, characterized by its complex layout replete with densely arranged obstacles, was adopted as the application scenario. Computational Fluid Dynamics (CFD) was employed to simulate the release of pollutant concentration at (−25.8 m, 0 m, 1.6 m) and (24.2 m, 41.6 m, 1.6 m), with flow velocities ranges from 1.8 to 7.6 m/s. Representative performance-influencing factors, including niche radius, population size, sensor response time, and sensor errors, were systematically evaluated. The results suggested that both Niche-DPSO and RSNM-DPSO algorithms were generally effective in positioning multiple pollution sources. Comparative analysis revealed that Niche-DPSO consistently outperformed RSNM-DPSO in terms of localization success rates, achieving a peak performance of approximately 98 %. Furthermore, Niche-DPSO could maintain its robust performance even under time-spatial-varying environmental and operational conditions, albeit at the expense of requiring more search steps and longer CPU processing time. • Two specialized algorithms were proposed for locating multiple pollution sources. • A CFD model was established and verified for application in the MUST experiment. • The algorithms' performance was rigorously evaluated in the simulation scenario. • Key performance factors were identified, and a sensitivity analysis was conducted. [ABSTRACT FROM AUTHOR]

The dispersion of hazardous gas in the environment presents dangerous risks for people living close to chemical plants or storages. Since heavy gases tend to stay at lower levels and disperse at a slower pace in the atmosphere, they are potentially more dangerous. In this paper, various mathematical models for turbulence (including k-ε, RNG k-ε, EARSM, LES, DES) and their associated parameters have been assessed, compared and validated against the experimental data in various scenarios to find the most suitable one for atmospheric dispersion of dense-gases. This topic has been investigated and validated by a computational fluid dynamics (CFD) simulation of the Kit-Fox experiment. The precision of the CAD models, practicality, computational resource requirements, and some other factors have been considered and addressed in this paper to achieve a comprehensive solution for atmospheric dispersion. The results here suggest that the proper selection of the turbulence model and the turbulent Schmidt number is crucial. Our results indicate that the most promising combination in the case of atmospheric dense-gas dispersion is the RNG k-ε model with the Schmidt number of 0.4, considering the demand for accuracy and computational resource. [ABSTRACT FROM AUTHOR]

Abstract The use of shade trees is among favorable urban planning strategies to improve outdoor thermal comfort and promote energy efficiency. Meanwhile, the presence of trees alters flow patterns and turbulent transport and influences the dispersion of air pollutants. In this study, we investigated the effects of urban trees on air pollutant dispersion in urban canopy layers using a coupled large-eddy simulation–Lagrangian stochastic modeling framework. The dispersions of two-way traffic emissions were simulated using a set of twenty four scenarios with varying canyon and tree geometries. Results show that tall trees lead to the strongest modification of the canyon flow and pollutant concentration, except in narrow canyons. Trees can exacerbate canyon pollution level in certain built environment owing to the presence of isolated canyon vortices. Trees with high leaf area density are beneficial to reducing concentration in broad street canyons, while trapping of pollutants is manifest in narrow canyons. The participatory role of trees, in conjunction with the effect of urban morphology, is crucial and needs to be meticulously evaluated in urban planning for promoting environmental quality. Graphical abstract Image 1 Highlights • We developed a coupled large-eddy simulation–Lagrangian stochastic model. • We quantified effects of trees and urban geometry on traffic pollutant dispersion. • The built environment is more susceptible to pollution with trees taller than roofs. • Isolated canyon vortex enhances the trapping effect and increases the pollution risk. [ABSTRACT FROM AUTHOR]

In the background region of the Tibetan Plateau (TP), the rapid urbanization probably results in the massive generation of persistent organic pollutants (POPs), which lacks monitoring and evaluation. Since landfill could serve as an important sink of the locally used POPs, the analysis of POPs in the Tibetan landfill area might help us to understand the source composition and their transport in the TP. In this study, the concentration variations of polybrominated diphenyl ethers (PBDEs) in five soil profiles and seven surficial sediments around the largest Tibetan landfill were investigated. The total concentrations of PBDEs ranged from 128 to 1219 ng/kg in soils, and from 447 to 7295 ng/kg in sediments. The dominance of nona- and deca-BDEs possibly indicated the wide usage of deca-BDE as flame retardant in the TP. The vertical and spatial distribution patterns of PBDEs within soils plausibly revealed their main transport pathways by atmospheric dispersion and leachate seepage from landfill. Based on principal components analysis and multiple linear regression, these two pathways were estimated to account for 61% and 39% of the total concentrations, respectively. Additionally, the spatial and vertical distributions of octa-to deca-BDEs within soils were significantly influenced by soil particle size. Although the PBDEs inventory in the study area was comparatively low, the rapid urbanization in the TP might dramatically accelerate the PBDE emissions in the future. This study firstly introduced the presence of local PBDEs in the TP, and the inventory already influenced the surrounding environment. Once involved in the regional cycle of the TP, the local source of PBDEs from waste might significantly serve to raise background level resulting otherwise primarily from long-range atmospheric transport. [ABSTRACT FROM AUTHOR]

In most hazardous materials (Hazmat for short) transportation systems, the purpose is to reduce the risk-cost from origins to destinations. This makes the hazmat system more complicated when compared to many other transportation systems. There are different models for considering risk in a hazmat transportation, the most broadly used is the so-called “traditional risk model”, through which the risk is defined as the product of two parameters: (a) the probability of an accident; and (b) the consequences of the accident. The consequences depend on other factors such the threat zone, which indicates the geographical area in which an atmospheric release of a substance would affect a given area during a specified time period. Moreover, the dispersion of pollutants within the accident area is a function of weather parameters such as wind direction, wind speed, atmospheric stability, which changes instantly in the real world. Thus, the weather system changes the risk parameters by changing the area impacted by a hazmat accident. Hence, it is difficult to identify and to tell the dispersion of a substance. The aim of this work is to develop the microservice that focuses on the computation of dispersion model and to identify the coverage of the affected area through the simulation software Areal location of Hazardous Atmosphere (ALOHA). The proposed microservice uses emission source, accident location and real-time meteorological data near to the sources, to provide necessary and accurate results rapidly. It can be used to more accurately simulate the atmospheric evolution of the released material in both time and space, for decision making and real-time response to save lives and to evacuate peoples to safety during a disaster release. [ABSTRACT FROM AUTHOR]

Copyright of Environmental Research, Engineering & Management / Aplinkos Tyrimai, Inžinerija ir Vadyba is the property of Institute of Environmental Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Revista Ambiente e Água is the property of Revista Ambiente e Agua and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

We present a methodology to identify multiple pollutant sources in the atmosphere that combines a data-driven dispersion model with Bayesian inference and uncertainty quantification. The dispersion model accounts for a realistic wind field based on the output of a multivariate dynamic linear model (DLM), estimated from measured wind components time series. The forward problem solution, described by an adjoint transient advection-diffusion partial differential equation, is then obtained using an appropriately stabilized finite element formulation. The Bayesian inference tool accounts for uncertainty in the concentration data and automatically states the balance between the prior and the likelihood. The source parameters are estimated by a Metropolis in Gibbs Monte Carlo Markov chain (MCMC) algorithm with adaptive steps. The MCMC algorithm is initialized with a maximum a posteriori estimator obtained with particle swarm optimization to accelerate convergence. Finally, the proposed methodology seems to outperform inversion techniques from previous works. • Stochastic wind model to jointly describe the wind intensity and direction. • The use of Metropolis in Gibbs MCMC algorithm with automatic step-size adaptation. • Data-driven approach to balance the likelihood function and the prior density weight. • Physical data to reduce the search region. • PSO to provide the initial step to the MCMC. [ABSTRACT FROM AUTHOR]

Temporal absences in observation records lead to release losses during the source term inversions of atmospheric radionuclide emissions. Consequently, objectively-estimated source terms for the Fukushima accident contain fewer release details and present large discrepancies when compared with the expert-judged one. This paper describes an objective method that can adaptively recover the missing releases caused by the temporal absences of observations. The proposed method assumes that the accident releases of radionuclides are piecewise-constant and comprise both peaks and constant releases. The missing releases are adaptively recovered as either peaks or constant releases by minimizing the total variation of the estimated source term. The proposed method is applied to the Fukushima accident and evaluated against regional airborne and deposited 137Cs observations. The results demonstrate that this method effectively recovers the missing releases, producing a source term that matches the timing of both on-site gamma dose rate peaks and accident events. The retrieved source term improves the simulation of air concentrations and reproduces most of the deposition patterns. This is the first time that an objective method has independently reproduced the details in the expert-judged one for the Fukushima accident. [Display omitted] • Recovery of missing releases caused by temporal absences of observations. • Preservation of both sharp peaks and constant releases. • First independent objective source term matching the expert-judged one. • Agreement with on-site gamma dose rate peak timing and accident events. • Improved spatiotemporal simulation of airborne 137Cs for the Fukushima accident. [ABSTRACT FROM AUTHOR]

CO 2 is recognized as one of the most important greenhouse gases. Many mitigating solutions to stabilize its atmospheric concentration are currently being investigated in order to control the so called Global Warming . Among these, the CCS ( Carbon Capture and Storage ) chain is one of the most promising solutions and is linked to the handling of large amounts of CO 2 through dedicated buried pipelines. As a consequence of any accidental release, a dry ice bank may be formed on the ground acting as a delayed emission source. This study aims at investigating different modeling approaches to face hazards related to this source and the mechanisms related to the near field atmospheric dispersion of CO 2 . Moving from simplified approaches to more complex ones relying on Computational Fluid Dynamics, some danger distances are classified under different stability classes. The analysis shows some discrepancies concerning the predicted gas dispersion. The most simplified approaches are not able to give a near–field reliable description that is instead captured by the CFD along with stratification phenomena. On the contrary, the CFD applicability is strictly linked to the computational burden that is usually not compatible with emergency–related responses but only with planning issues. [ABSTRACT FROM AUTHOR]

Carbon capture and storage (CCS) presents the short-term option for significantly reducing the amount of carbon dioxide (CO 2 ) released into the atmosphere from the combustion of fossil fuels, thereby mitigating the effects of climate change. Enabling CCS requires the development of capture, storage and transport methodologies. The safe transport of CO 2 in CCS scenarios can be achieved through pipelines or by shipping. Either way, transport and temporary storage of pressurised liquid CO 2 will be required and subject to quantitative risk assessment, which includes the consideration of the low-risk, low-probability puncture or rupture scenario of such a pipeline, ship or storage facility. In this work, we combine multiple experimental datasets all concerned with the atmospheric free release of pure and impure liquid CO 2 from CCS-transport-chain-relevant high pressure reservoirs and perform the first multiple dataset comparison to numerical models for both pure and impure CO 2 jets in dry ambient air with no water vapour. The results validate the numerical approach adopted and for the prediction of such releases, highlight the significance of the mixture fraction at the release point, over the mixture composition itself. A new method for impure CO 2 dispersion modelling is introduced and limited preliminary comparisons of impure CO 2 data and predictions are performed. No clear difference between pure and impure releases is found for the cases considered. [ABSTRACT FROM AUTHOR]

Carbon capture and storage (CCS) presents a short-term option for significantly reducing the amount of carbon dioxide (CO 2 ) released into the atmosphere. National Grid initiated the COOLTRANS research programme to consider the CCS pipeline transportation of high-pressure dense-phase CO 2 , including the development and application of a mathematical model for predicting the sonic near-field dispersion of pure CO 2 following pipeline venting or failure. In Part I ( Wareing et al., 2015a ) validation of this numerical model against experimental data was considered, with reasonably good agreement quantitatively and qualitatively demonstrated for a rupture of a 0.15 m external diameter pipeline. In this second part, the model is applied to the rupture of a 96 km pipeline with a nominal 0.61 m external diameter, the same as that proposed in the Don Valley CCS Project. In the base-case, six snapshots of the flow dispersing into dry air are numerically simulated. Integrated mass and momentum fluxes exiting the crater are calculated, with the intention that they can be directly employed as source conditions for far-field dispersion simulations. The amount of solid CO 2 deposited in the crater is estimated through particle tracking techniques and six sensitivity studies vary crater properties. [ABSTRACT FROM AUTHOR]

Carbon dioxide (CO 2 ) capture and storage presents a short-term option for significantly reducing the amount of CO 2 released into the atmosphere and mitigating the effects of climate change. To this end, National Grid initiated the COOLTRANS research programme to consider the pipeline transportation of high pressure dense phase CO 2 , including the development and application of a mathematical model for predicting the sonic near-field dispersion of pure CO 2 following the venting or failure of such a pipeline. Here, the application of this model to the rupture of a buried pipeline is considered and compared to experimental data obtained through the COOLTRANS programme. The rupture experiment was performed on a 230 m length of 152 mm external diameter pipeline with 300 mm soil cover, equivalent to approximately 1/4 scale when compared to the proposed full-scale 600 mm (24-inch) diameter pipelines with 1.2 m soil cover on average proposed in the UK. The experiment was performed in a pre-formed crater based on experimentally formed craters in other experiments. The comparison demonstrates reasonable quantitative and qualitative agreement. Such validated dispersion flow, to be applied to full-scale rupture modelling in Part II, defines novel, robust, thermodynamically accurate multi-phase source conditions, that enable far-field computational fluid dynamics studies and feed into pragmatic quantified risk assessment models. [ABSTRACT FROM AUTHOR]

Amine solvents used in CO 2 capture technologies result in the release of compounds such as nitrosamines and nitramines to the atmosphere. The reaction kinetics of monoethanolamine and the resulting degradation amines, methylamine and dimethylamine, are studied using transition state and collision theory. A simplified amine atmospheric chemistry scheme and three types of reactions,—with barrier, without a barrier and a photolysis reaction—are considered using geometric, energetic and thermodynamic data derived from quantum chemistry and kinetic modelling. The rate coefficients obtained are in excellent agreement with existing experimental and theoretical values. These coefficients are used within the Amine Chemistry Module of the atmospheric dispersion model ADMS 5 to solve the advection-dispersion-chemical equations. A case study on the Technology Centre Mongstad is conducted to estimate the dispersion, chemical transformation and transport pathways of these amines away from the emitting facility. Reliable estimates of the concentrations of the resulting nitrosamines and nitramines are determined and compared to safety guideline values to establish the risk these discharges may pose on the environment. This study illustrates the theoretical methodology developed and its implementation within the ADMS 5 atmospheric dispersion model, which can be used at any amine based CO 2 capture facility regardless of its geographical location. [ABSTRACT FROM AUTHOR]

Copyright of Estudos Tecnológicos em Engenharia is the property of Universidade do Vale do Rio dos Sinos and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Atmosphere -- Ocean (Taylor & Francis Ltd) is the property of Taylor & Francis Ltd and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Carbon capture and storage (CCS) presents a short-term option for significantly reducing the amount of carbon dioxide (CO 2 ) released into the atmosphere and mitigating the effects of climate change. To this end, National Grid initiated the COOLTRANS research programme to consider the pipeline transportation of high pressure dense phase CO 2 . Part of this work involved the development of a mathematical model for predicting the near-field dispersion of pure CO 2 following the venting, puncture or rupture of such a pipeline. This article describes the application of this model to the simulation of punctures in buried pipelines, and specifically three scenarios – a puncture at the side, at the base and at the top of the pipeline. Such scenarios following human interference with the pipeline are the most common type of pipeline failure and form an important part of the quantitative risk analysis (QRA) required in the development of such pipelines for CCS. In each scenario, a idealised crater is modelled, dispersing CO 2 into dry air. In two of the experiments, an idealisation of a naturally formed crater is used. In the third, the idealisation is based on the pre-formed crater. We present the steady state flow in each scenario and, using Lagrangian particle tracking techniques, give estimates on the amount of solid CO 2 deposited in the crater. In the case of the side puncture, experimental data above the crater are available and the model qualitatively and quantitatively predicts the nature of the flow in this case. The validated steady state flows at the top of the crater presented here for these three common scenarios provide the basis for developing robust source conditions for use in computational fluid dynamics (CFD) studies of far-field dispersion and for use with pragmatic QRA models, as well as representing a significant step towards modelling full-scale ruptures of CCS pipelines. [ABSTRACT FROM AUTHOR]

Highlights: [•] We present the validation of a novel model for near-field sonic CO2 dispersion. [•] We validate against experimental data from dense and gas phase releases. [•] Accurate predictions are obtained in the near and far-field. [•] This work is applicable to high pressure pipelines in CCS scenarios. [•] Robust far-field source models can be developed from this work. [ABSTRACT FROM AUTHOR]

Above ground level (ABL) discharges are commonly employed in northern climates to release radon-containing soil gases from sub-slab depressurization radon mitigation systems. While there are many practical reasons to employ this in cold climates (e.g., to avoid ice build-up), it does inherently elevate the outdoor radon concentrations, and raises the possibility of radon re-entrainment back into living spaces of the emitting house, and its neighbors. A method has been developed for assessing outdoor radon dispersion and re-entrainment risks. It links computational fluid dynamics calculations for evaluating outdoor concentrations, and regional multi-annual meteorological records that give the occurrence probability for different wind speed, wind direction, and atmospheric stability conditions. When combined with assumptions about indoor/outdoor concentration ratios, annual average exposure concentrations to radon can be estimated. Concentrations along surfaces of the emitting house are often quite high close to the exhaust vent, and air exchange into the house from nearby open windows, air intakes, etc., and can result in high indoor concentrations. Re-entrainment into the neighboring house is often less serious, though certain circumstances can lead to radon being trapped in the space between the two buildings, which leads to higher exposure. • CFD modeling of radon dispersion from above ground level exhausts. • Combine with frequencies of prevailing wind conditions. • Prevailing wind direction leads to formation of building cavities that traps radon. • Method for assessing annual exposure for emitting building and neighbor. [ABSTRACT FROM AUTHOR]

Highlights: [•] A novel multi-phase model capable of predicting CO2 releases is presented. [•] Measurements of temperatures and concentrations of CO2 releases are presented. [•] Validation of mathematical models is undertaken against new experimental data. [•] Excellent level of agreement with measurements of jet characteristics obtained. [•] Tools presented to aid evaluation of hazard consequences of CO2 pipeline failure. [Copyright &y& Elsevier]

Abstract: During the onshore Carbon dioxide transportation potential risks such as leakages or even pipeline breaches can occur. In such cases CO2 will be released and dispersed in the ambient having short-time impact on the environment and potentially on human health and long-time consequences on the climate. The hydrodynamical characterization of the released jet expansion and plume dispersion is decisive for understanding the pollutant impacts on the atmosphere and it is an essential part of risk assessment for the CCS-technology. Numerical simulations of gaseous CO2 expansion and dispersion will be used to analyze the release conditions influence on harmful concentration distances. [Copyright &y& Elsevier]

The modelling system RAMS/CALMET/CALPUFF was used to simulate the atmospheric dispersion and deposition of dioxins emitted from industrial sources over the Province of Lecce (Italy). Comparison between data and predictions shows that the model reasonably simulates the deposition patterns. Dry deposition of PCDD/F extends mainly downwind of the sources following the prevailing wind direction. Wet deposition of PCDD/F is limited to the neighborhood of the emission sources and is associated with the highest PCDD/F deposition values. [ABSTRACT FROM AUTHOR]

Field experiments with a Radioactive Dispersion Device (RDD) were performed by the National Radiation Protection Institute (NRPI) of the Czech Republic. We present the results of computer simulations of these experiments using a new microscale model, Charles University Large Eddy Microscale Model (CLMM). The model was first validated using wind tunnel data for the dispersion of continuous passive scalar release around a building with a similar aspect ratio to the building used in the experiments. The results for surface contamination by deposition are highly sensitivity to the particle size distribution, which in the present case has a large scatter. [ABSTRACT FROM AUTHOR]

Lagrangian dispersion models require estimates of the local dissipation rate (ε) of turbulent kinetic energy (κ). In this study, we evaluate the sensitivity of a Lagrangian model to different estimates of ε in simulating passive scalar dispersion in a turbulent boundary layer over a rough surface. Two different estimates of ε are used to simulate pollutant dispersion emitted by a linear elevated source with a Lagrangian model which integrates a macromixing and a micromixing scheme. Comparison between numerical and experimental results allows us to discuss the performance of the model and to define its sensitivity to ε. [ABSTRACT FROM AUTHOR]

A Bayesian inference scheme is used to address the problem of general source reconstruction. To this purpose, starting from a simple, physically motivated structure-based representation for a general source distribution, Bayesian probability theory is used to formulate the full joint posterior probability density function for the parameters in this representation. The exploration of the high-dimensional parameter space using simulated annealing and a Markov chain Monte Carlo sampler is described. The explicit linkage between the computational tools used for posterior sampling and concepts in statistical mechanics is emphasised. The proposed methodology is validated using a real dispersion experiment involving a multiple source release. [ABSTRACT FROM AUTHOR]

This study investigates the performance of different air pollution dispersion models in low wind conditions. The models have been applied to two sites frequently characterised by weak winds: the cities of Modena and Reggio Emilia, in the Po River Valley (Northern Italy). The emission sources are the municipal waste incinerator (Modena) and a turbogas plant (Reggio Emilia). Total Suspended Particulate (TSP) concentration levels are estimated by the gaussian Industrial Source Complex (ISC3) and WinDimula 3.0 models, and the Langrangian model SPRAY. WinDimula 3.0 and SPRAY simulations perform significantly better than ISC3, SPRAY shows the highest reliability close to the source. [ABSTRACT FROM AUTHOR]

The computational fluid dynamics code ADREA-HF is used to simulate atmospheric dispersion field experiments around an isolated cylindrical obstacle and two upwind sources of ammonia and propane, with the ammonia source located at different lateral positions. Model calculated concentrations and concentration fluctuations are compared with the experimental results, to investigate the effect of the lateral source displacement on the fluctuations intensity, showing a fair level of agreement. The observed differences were mainly attributed to the specificities of the cases, such as the interaction of a laterally displaced plume with the cylindrical obstacle, and to the variability observed in the field. [ABSTRACT FROM AUTHOR]

We have evaluated the performance of several urban Atmospheric Transport and Dispersion (AT&D) models by comparing model predictions to tracer gas concentrations measured during the Joint Urban 2003 field experiment in Oklahoma City, USA. These models include the Urban Canopy, Urban Dispersion Model (UDM), and Micro-SWIFT/SPRAY (MSS) modes within the HPAC modelling suite, QUIC-URB/QUIC-PLUME models, and the MESO/RUSTIC models. We discuss some of the results of these comparisons, including relative model performance according to bias and scatter metrics, differences in model behaviour for predictions of daytime vs. nighttime releases, and operational considerations such as runtime differences. [ABSTRACT FROM AUTHOR]

Abstract: Projects in carbon capture and storage technologies for energy production involve the transport of vapour, liquid and supercritical CO2 and CO2/hydrocarbon gas mixtures via pipelines and process systems with subsequent injection into wells, e.g. offshore under the seabed. In addition several chemical companies often store and transport large quantities of CO2 and this may also represent a hazard. There is a need to model potential loss of containment scenarios for risk assessment and design purposes for such installations. It is observed that several models used in quantitative risk analyses and hazard assessment studies are not able to take into account modelling of the thermodynamics of CO2 in case of accidental releases from dense or supercritical conditions. Statoil together with DNV therefore initiated a project to further improve the Phast code for modelling of CO2 releases. The work and methodology derived in this project have mainly been developed by Det Norske Veritas (DNV), but with significant co-operation and input by Statoil. The consequence modelling package Phast examines the progress of a potential incident from the initial release to the far-field dispersion including the modelling of rainout and subsequent vaporisation. The original Phast 6.54 models allow the released chemical to occur only in the vapour and liquid phases. The new Phast 6.6 models were extended to also allow for the occurrence of fluid to solid transition in case of CO2 releases. This applies both for the post-expansion state in the discharge model, as well as for the thermodynamic calculations by the dispersion model. Here it is assumed that no solid deposition occurs on the ground. The current paper documents work regarding modelling by Phast 6.6 of discharge and atmospheric dispersion of carbon dioxide, including a detailed sensitivity analysis for a wide range of scenarios (base cases) including high-pressure cold releases (liquid storage) and high-pressure supercritical releases (vapour storage) from vessels, short pipes or long pipes. The objectives of this work were to examine the effect of input parameters on key output data, to ensure robustness of the models, and to identify further model improvements where deemed to be necessary. [Copyright &y& Elsevier]

Dispersion in urban areas is determined by transport and mixing processes within the street network and ventilation into the external atmosphere. In order to improve the understanding of the exchange mechanisms within the urban canopy, wind tunnel and numerical investigations have been performed on two idealised typical urban configurations, the street intersection and the square. The numerical simulations were compared to the experimental values, in order to evaluate the reliability of the numerical approach in simulating local flow patterns and study the influence of the geometrical layout on mass and momentum exchange mechanisms. [ABSTRACT FROM AUTHOR]

Results from an evaluation of three dispersion models are presented: the currently operational OML model, a new, improved 'Research Version' of OML, and the US AERMOD model. The evaluation is based on the Prairie Grass data set. For these data the OML Research Version appears superior to the other two models. Further, the paper discusses problems and pitfalls of the Prairie Grass data set. The criteria for exclusion of data have tremendous impact on evaluation metrics. A new Wiki on Atmospheric Dispersion has the potential to become a very useful focal point to pool and communicate experiences on data sets such as Prairie Grass. [ABSTRACT FROM AUTHOR]

A Lagrangian stochastic (single particle) model is modified in order to account for simple chemistry reactions and tested against measured wind tunnel data. These data refers to a reactive plume generated by a single point source of NO inside a turbulent grid flow doped with ozone. The comparisons were made at different distances from the emission considering all the substances involved in the experiment. The cross correlation terms between the concentrations of the different chemical compounds are neglected or parameterised. Despite this simplification the results are rather satisfactory and seem to encourage practical applications in real atmosphere. [ABSTRACT FROM AUTHOR]

In the framework of the COST 732 action, several teams run models to verify the proposed Best Practice Guideline (Franke et al., 2007). The data set concerns the Mock Urban Setting Test (MUST) experiment, where wind field and dispersion measurements were conducted for an array of obstacles as a full-scale experiment, as well as in a wind tunnel. The pollutant transport research group at the Department of Fluid Mechanics of the BME started simulations of flow within this idealised city using two commercial CFD codes, FLUENT and MISKAM. The paper presents results of the flow simulations in the 0 degree MUST case through velocity profiles, contour plots and validation metrics. [ABSTRACT FROM AUTHOR]

An abstract of the article "An urban scale model for pollutant dispersion in Rome," by Giovanni Leuzzi, Paolo Monti, and Andrea Amicarelli is presented.

An abstract of the article "Simulations of the dispersion from a waste incinerator in the Turin area in three different meteorological scenarios," by Silvia Trini Castelli, D. Anfossi, and S. Finardi is presented.

Abstract: Understanding the potential impacts of unexpected surface releases of CO2 is an essential part of risk assessment for geologic carbon sequestration sites. We have extended a mesoscale atmospheric model to model dense gas dispersion of CO2 leakage. The hazard from CO2 leakage is greatest in regions with topographic depressions where the dense gas can pool. Simulation of dispersion in idealized topographies shows that CO2 can persist even under high winds. Simulation of a variety of topographies, winds, and release conditions allows the generation of a catalog of simulation results that can be queried to estimate potential impacts at actual geologic carbon sequestration sites. [Copyright &y& Elsevier]

Abstract: Safe transportation of carbon dioxide is an important issue in the developing field of Carbon Capture and Storage (CCS). A leakage from a high-pressure transportation facility could result in damage to the environment and be a hazard to people, depending on the total amount of carbon dioxide released to the atmosphere and the concentrations achieved. In the field of risk assessment, the atmospheric dispersion of gases has often been undertaken using Gaussian models. The starting point for the model calculations has often been a static CO2 cloud, avoiding the initial dispersion phase involving the jet. From high-pressure transportation facilities in CCS projects, any significant CO2 leak would initially be at high speed, with rapid entrainment of air. This would provide an early means of dispersion of the gas, mainly dependent on the speed of the flow. In this study on leakage from facilities within a modular transportation system, a CFD model is used, enabling the initial jet to be explicitly modeled. A comparison is made of the results with the no-jet case and suggestions for future risk assessment given. [Copyright &y& Elsevier]

In this work the impact of two different house-heating systems on pollution scenarios in the Turin town centre is evaluated by means of the three-dimensional modelling system RMS. The first scenario (present situation) refers to the NOx ground level concentration due to an existing Combined Heat and Power Plant (CHP-plant) and to domestic heating, whereas the second one (future situation) considers the possible advantages of substituting the domestic heating of a central town district with a second Combined Heat and Power Plant to be installed in the district itself. A five consecutive days simulation has been carried out in a particularly severe dispersion situation, characterised by thermodynamic stability and low wind conditions. This period was selected on the basis of in situ observations and its choice was then confirmed as appropriate by means of a statistical analysis of the meteorological model outputs. The main result of the study is that hourly NOx maxima g.l.c, in the centrally heated district is lower in the future scenario than in the present one; while maxima keep approximately the same in the rest of the town. Then, top-ten ground level concentrations of daily maxima over all the domain decrease in the new scenario. [ABSTRACT FROM AUTHOR]

The Urban Dispersion Model (UDM) [1] was developed to satisfy a need of the UK Ministry of Defence to predict the dispersion of atmospheric pollutants within the urban environment. It is being subjected to an extensive validation and verification programme, which includes comparing model predictions against a comprehensive selection of measurements drawn from a database of field experimental trials. The model is compared here with three different field trials covering ranges from tens of metres to kilometres. The model predictions for maximum concentration along a given sampling line shows an average fractional bias of 0.22, a typical error of greater than 50% of the mean, and over 54% of the predictions are within a factor of 2 of the observations for the three data sets examined. [ABSTRACT FROM AUTHOR]

We address the source characterization of atmospheric releases using adaptive strategies in Bayesian inference in combination with the numerical solution of the dispersion problem by a stabilized finite element method and uncertainty quantification in the measurements. The adaptive techniques accelerate the convergence of Monte Carlo Markov Chain (MCMC) algorithms, leading to accurate reconstructions of the source parameters. Such accuracy is illustrated by the comparison with results from previous works. Moreover, the technique used to simulate the corresponding dispersion problem allowed us to introduce relevant meteorological information. The uncertainty quantification also improves the quality of reconstructions. Numerical examples using data from the Copenhagen experimental campaign illustrate the effectiveness of the proposed methodology. We found errors in reconstructions ranging from 0.11% to 8.67% of the size of the search region, which is similar to results found in previous works using deterministic techniques, with comparable computational time. [Display omitted] • Combination of adaptive MCMC algorithms with a FEM solution of the dispersion model. • Incorporation of uncertainty quantification. • Adaptive rules in the MCMC algorithm. • The use of the Metropolis in Gibbs algorithm to solve the source identification problem. • Simultaneous estimation of source parameters and the uncertainty in the data. [ABSTRACT FROM AUTHOR]

We propose a methodology to estimate single and multiple emission sources of atmospheric contaminants. It combines hybrid metaheuristic/gradient-descent optimization techniques and Tikhonov-type regularization. The dispersion problem is solved by the Galerkin/Least-squares finite element formulation, which allows more realistic modeling. The accuracy of the proposed inversion model is tested under different contexts with experimental data. To identify single and multiple emissions, we use experimental field data. We consider different configurations for both the Tikhonov-type functional and optimization techniques. Several single and composite data misfit functions are tested. We also use a discrepancy-based choice rule for the regularization parameter. The resulting inversion tool is highly versatile and presents accurate results under different contexts with a competitive computational cost. Image 1 • The source identification is solved by Tikhonov-type regularization. • We use single and composite data misfit functions. • Minimization is performed by metaheuristic/gradient-descent techniques. • The methodology is tested with single and multiple emissions from experimental data. • The Algorithm provides accurate estimations of source parameters in both cases. A new Algorithm combining accurate dispersion models, Tikhonov regularization and hybrid optimization tools estimates pollutant emission sources. [ABSTRACT FROM AUTHOR]

Abstract unavailable. [ABSTRACT FROM AUTHOR]

There is an evident lack of reliable and detailed in situ measurement data for verifying numerical predictions of atmospheric dispersion in the urban environment on sub-meso scales. Wind-tunnel studies of dispersion around typical elements of the urban canopy (isolated buildings, groups of buildings, street canyons) could provide valuable substitutes for field datasets. They can achieve a high resolution of the measured concentration fields, and may be used for evaluation of numerical models and for expert estimates of air quality in the urban environment. This paper presents results of several case studies of gaseous pollutant dispersion in a neutrally stratified wind-tunnel flow. The following cases have been investigated: (1) Point source: (a) isolated rectangular building, and (b) isolated U-shaped building; (2)Line source in a street canyon: effects of the upwind building configuration and the roof shape; (3) Line source in a city quarter (four blocks separated by two perpendicular canyons with rectangular cross-sections). For the case of a line source in a street canyon, the wind-tunnel results are compared with numerical model calculations. [ABSTRACT FROM AUTHOR]

The results obtained in convective boundary layer dispersion by two Lagrangian particle models (according to Thomson's 1984 and 1987 papers) are compared. First, the sensitivity of the two models in accounting for the third-order moment of vertical wind speed fluctuations has been assessed, considering homogeneous non-Gaussian turbulence. Then, the ability of the two models to simulate the ground-level concentration field has been tested, by comparing their predictions with tracer data measured in two experiments. The first is one of the well-known water tank experiments performed by Willis and Deardorff in 1978,the second is the Katrex field experiment (Thomas et al., 1983). Theresults obtained in the case of the controlled conditions seem to recommend the use of the model based on Thomson's 1987 paper, whereas the performances of both models are comparable in simulating a real case. [ABSTRACT FROM AUTHOR]

The so-called Model Validation Kit has been used as a basis for modelling exercises at workshops in Manno (1993), Mol (1994) and at the present workshop. It is a practical tool, meant to serve as a common frame of reference for modellers. It consists of three experimental datasets, accompanied by software for model evaluation. Before the present workshop, a pilot study was conducted, aimed at extending the original toolkit with datasets from two additional experimental campaigns. These `new' datasets contain data from experimental campaigns at Indianapolis (urban) and Bull Run (moderately complex terrain). Both campaigns deal with emissions from a single stack, and include detailed tracer measurements from several hundred hours. The present paper gives an introduction to the two `new' datasets. A large part of the paper, however, is used to convey general experiences on the preparation and use of performance-evaluation datasets. The context of this work is discussed; particular emphasis is on its relation to a planned catalogue of models, which will become available through the World Wide Web. [ABSTRACT FROM AUTHOR]