Multimedia Modelling of the Exposure to Cadmium and Lead Released in the Atmosphere—Application to Industrial Releases in a Mediterranean Region and Uncertainty/Sensitivity Analysis

International audienceTwo advanced models that respectively simulate the transport of heavy metals in the atmosphere at continental and regional scale, as well as the transfer of contaminants in the air–soil–plant system, were used to study the potential accumulation of lead and cadmium in vegetables in a French region submitted to global and local industrial releases. The dynamics of lead and cadmium in the atmosphere, the soil and two types of plants (leaf and fruit vegetables respectively) were simulated over 40 years. Kinetic best estimate calculations were conducted to simulate the potential accumulation of lead and cadmium in soils and plants. An uncertainty analysis was also performed to provide confidence intervals for the maximum contamination levels of leaf and fruit vegetables. A sensitivity analysis allowed to identify the most sensitive parameters of the modeling system. For this purpose, Probability Density Functions were proposed for the main parameters included in the air-soil-plant model. Different results were obtained for lead and cadmium respectively, lead being more sensitive to aerial processes (interception of deposits by leaves eventually followed by translocation to edible organs)

Modelling atmospheric dry deposition in urban areas using an urban canopy approach

Atmospheric dry deposition is typically modelled using an average roughness length, which depends on land use. This classical roughness-length approach cannot account for the spatial variability of dry deposition in complex settings such as urban areas. Urban canopy models have been developed to parametrise momentum and heat transfer. We extend this approach here to mass transfer, and a new dry deposition model based on the urban canyon concept is presented. It uses a local mixing-length parametrisation of turbulence within the canopy, and a description of the urban canopy via key parameters to provide spatially distributed dry deposition fluxes. Three different flow regimes are distinguished in the urban canyon depending on the height-to-width ratio of built areas: isolated roughness flow, wake interference flow and skimming flow. Differences between the classical roughness-length model and the model developed here are investigated. Sensitivity to key parameters are discussed. This approach provides spatially distributed dry deposition fluxes that depend on surfaces (streets, walls, roofs) and flow regimes (recirculation and ventilation) within the urban area

Long term modelling of the dynamical atmospheric flows over SIRTA site

International audienceThe atmospheric flow knowledge is important for its role in pollutant dispersion and wind energy. In this work, the hourly atmospheric flow output (8760 states) from Weather Research and Forcasting (WRF) model for the year 2011 over SIRTA (Site Instrumental de Recherche par Télédétection Atmosphérique) are analyzed and clustered into a finite number of representative atmospheric states using two clustering methods: non-controlled clustering and controlled clustering. The resulting representative situations of those clusters are used to specify boundary conditions for flow downscaling over the heterogeneous SIRTA. For flow downscaling, the CFD code Code_Saturne is used to simulate each representative atmospheric state. To assess the efficiency of WRF clustering and Code_Saturne downscaling, the measurements in SIRTA over the same year are used as reference. The Mean Absolute Error (MAE) and the Kullback-Leibler divergence (KL) metrics were computed for the distributions of the atmospheric flow features in order to: (i) compare the difference between the performance of the two clustering procedures, and (ii) compare the distribution of flow properties between WRF mesoscale model and Code_Saturne. It is clearly demonstrated that the two clustering methods are comparable in benefit, and that Code_Saturne improves considerably the flow features modeling in comparison to measurements

Modelling atmospheric effects on performance and plume dispersal from natural draft wet cooling towers

International audienc

Large eddy simulation of radiation fog: impact of dynamics on the fog life cycle

Large eddy simulations (LESs) of a radiation fog event occurring during the ParisFog experiment are studied with a view to analyse the impact of the dynamics of the boundary layer on the fog life cycle. The LES, performed with the Meso-NH model at 5 m resolution horizontally and 1 m vertically, and with a 2-moment microphysical scheme, includes the drag effect of a tree barrier and the deposition of droplets on vegetation. The model shows good agreement with measurements of near-surface dynamic and thermodynamic parameters and liquid water path. The blocking effect of the trees induces elevated fog formation, as actually observed, and horizontal heterogeneities during the formation. It also limits cooling and cloud water production. Deposition is found to exert the most significant impact on fog prediction as it not only erodes the fog near the surface but also modifies the fog life cycle and induces vertical heterogeneities. A comparison with the 2 m horizontal resolution simulation reveals small differences, meaning that grid convergence is achieved. Conversely, increasing numerical diffusion through a wind advection operator of lower order leads to an increase in the liquid water path and has a very similar effect to removing the tree barrier. This study allows us to establish the major dynamical ingredients needed to accurately represent the fog life cycle at very high-resolution

Parametrisation des nuages et des precipitations envisagees pour le code atmospherique Mercure

SIGLEAvailable at INIST (FR), Document Supply Service, under shelf-number : 26165 C, issue : a.1996 n.21 / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc

Etude de la reconstitution des flux de chaleur et de quantite de mouvement a partir des donnees de la campagne ECLAP

Available at INIST (FR), Document Supply Service, under shelf-number : 26165 C, issue : a.1996 n.11 / INIST-CNRS - Institut de l'Information Scientifique et TechniqueSIGLEFRFranc

A 3d Regional Scale Photochemical Air Quality Model. Application to a 3 Day Summertime Episode over Paris

This paper presents AZUR, a 3D Eulerian photochemical air quality model for the simulation of air pollution in urban and semi-urban areas. The model tracks gas pollutant species emitted into the atmosphere by transportation and industrial sources, it computes the chemical reactions of these species under varying meteorological conditions (photolysis, pressure, temperature, humidity), their transport by wind and their turbulent diffusion as a function of air stability. It has a modular software structure which includes several components dedicated to specific processes :-MERCURE, a meso-scale meteorological model to compute the wind field, turbulent diffusion coefficients, and other meteorological parameters. It is a 3D regional scale model accounting for different ground types and urban densities. It includes a complete set of physical parameterizations in clear sky. -MIEL, an emission inventory model describing the pollutant fluxes from automotive transportation, domestic and industrial activities. This model includes a mobile source inventory based on road vehicle countings together with global information on transportation fluxes extracted from statistical population data. It uses specific emission factors representative of the vehicle fleet and real driving patterns. -MoCA a photochemical gas phase model describing the chemistry of ozone, NOx, and hydrocarbon compounds. This model, with 83 species and 191 reactions, is a reduced mechanism well adapted to various air quality conditions (ranging from urban to rural conditions). For interpretative reasons, the identity of primary hydrocarbons is preserved. -AIRQUAL, a 3D Eulerian model describing the transport by mean wind flux and air turbulent diffusion of species in the atmosphere, associated with a Gear type chemical equation solver. The model has been applied to a 3-day summertime episode over Paris area. Simulation results are compared to ground level concentration measurements performed by the local monitoring network (Airparif)