Publications

2022

• Detailed Speciation of Non-Methane Volatile Organic Compounds in Exhaust Emissions from Diesel and Gasoline Euro 5 Vehicles Using Online and Offline Measurements
  
  • Marques Baptiste
  • Kostenidou Evangelia
  • Valiente Alvaro Martinez
  • Vansevenant Boris
  • Sarica Thibaud
  • Fine Ludovic
  • Temime-Roussel Brice
  • Tassel Patrick
  • Perret Pascal
  • Liu Yao
  • Sartelet Karine
  • Ferronato Corinne
  • D’anna Barbara
  Toxics, MDPI, 2022, 10 (4), pp.184. The characterization of vehicle exhaust emissions of volatile organic compounds (VOCs) is essential to estimate their impact on the formation of secondary organic aerosol (SOA) and, more generally, air quality. This paper revises and updates non-methane volatile organic compounds (NMVOCs) tailpipe emissions of three Euro 5 vehicles during Artemis cold urban (CU) and mo- torway (MW) cycles. Positive matrix factorization (PMF) analysis is carried out for the first time on proton transfer reaction time-of-flight mass spectrometer (PTR-ToF-MS) datasets of vehicular emission. Statistical analysis helped to associate the emitted VOCs to specific driving conditions, such as the start of the vehicles, the activation of the catalysts, or to specific engine combustion regimes. Merged PTR-ToF-MS and automated thermal desorption gas chromatography mass spec- trometer (ATD-GC-MS) datasets provided an exhaustive description of the NMVOC emission factors (EFs) of the vehicles, thus helping to identify and quantify up to 147 individual compounds. In general, emissions during the CU cycle exceed those during the MW cycle. The gasoline direct injection (GDI) vehicle exhibits the highest EF during both CU and MW cycles (252 and 15 mg/km), followed by the port-fuel injection (PFI) vehicle (24 and 0.4 mg/km), and finally the diesel vehi- cle (15 and 3 mg/km). For all vehicles, emissions are dominated by unburnt fuel and incomplete combustion products. Diesel emissions are mostly represented by oxygenated compounds (65%) and aliphatic hydrocarbons (23%) up to C22, while GDI and PFI exhaust emissions are composed of monoaromatics (68%) and alkanes (15%). Intermediate volatility organic compounds (IVOCs) range from 2.7 to 13% of the emissions, comprising essentially linear alkanes for the diesel vehicle, while naphthalene accounts up to 42% of the IVOC fraction for the gasoline vehicles. This work demon- strates that PMF analysis of PTR-ToF-MS datasets and GC-MS analysis of vehicular emissions provide a revised and deep characterization of vehicular emissions to enrich current emission inventories. (10.3390/toxics10040184)
  DOI : 10.3390/toxics10040184
• Allophanes, a significant soil pool of silicon for plants
  
  • Cornu Sophie
  • Meunier Jean-Dominique
  • Ratie Céline
  • Ouedraogo Fréderic
  • Lucas Yves
  • Merdy Patricia
  • Barboni Doris
  • Delvigne Camille
  • Borschneck Daniel
  • Grauby Olivier
  • Keller Catherine
  Geoderma, Elsevier, 2022, 412, pp.115722. While in tropical soils recycling of plant phytoliths has been shown to represent a major pool of Si available for plants, the main Si pools available for plants in temperate soils are still poorly constrained. We characterised the various Si pools of temperate forested and cultivated soils in France by selecting seven paired sites (adjacent wheat and forest plots) for four soil groups: Luvisols, Albeluvisols, calcaric and hypereutric Cambisols. We showed that CaCl2-extracted Si (bioavailable) is mostly controlled by pH and allophanes (short-range ordered aluminosilicates) but not by phytoliths. Cultivation, by decreasing the soil organic carbon content increases the allophane content and the SiCaCl2 concentration. Our work highlights the importance of allophanes as the missing link between the soil solution and the clay minerals that could explain the reported correlation between the clay mineral content and bioavailable Si. (10.1016/j.geoderma.2022.115722)
  DOI : 10.1016/j.geoderma.2022.115722
• Free-surface flow simulations with a Lagrangian and an Arbitrary Lagrangian–Eulerian methods
  
  • Ferrand Martin
  , 2022. Free-surface flows have various natures in the environmental and industrial contexts. It may be a gentle mathematically regular surface with waves from which one may want to extract renewable energy, or an also smooth surface of an evaporating pool in case of recirculating pumps deficiency, but also a flow down a spillway with a really disturbed free-surface. Lagrange and/or Euler approaches can be used to solve the discretised Navier-Stokes equations with a free-surface.Among the Lagrangian methods, Smoothed Particle Hydrodynamics (SPH) is a mesh-less numerical method ideal for simulating potentially violent free-surface phenomena such as a wave breaking, or a dam-break for which many Eulerian methods can be difficult to apply.Gentle free-surface flows can also be tackled with the Arbitrary Lagrangian Eulerian (ALE) mesh-based Finite Volumes method, where the free-surface faces of the mesh move so that the kinematic boundary condition is fulfilled.The first Chapter is made to introduce SPH and ALE Finite Volumes and to draw links between the two methods.For SPH, dealing with boundary conditions (walls and open boundaries) is one of the most challenging parts as it is declared as one of the Grand Challenges of the international organisation representing the community of researchers and industrial users of Smoothed Particle Hydrodynamics (SPHERIC). Concerning walls, the proposed methodology introduced in Chapter 2 relies on the semi-analytical approach which consists in renormalising the density field near a solid wall with respect to the missing kernel support area, and intrinsic gradient and divergence operators that ensure conservation properties are employed. The accuracy of the physical field such as the pressure next to walls is considerably improved, and the consistent manner developed to wall-correct operators allows us to perform simulations with turbulence modelsAn axisymmetric formulation with a unified renormalisation factor taking both radial correction and wall renormalisation is proposed as an extension of this work in Appendix.The third Chapter deals with open-boundaries for the SPH approach with the resolution of a Riemann problem associated to the hyperbolic compressible SPH framework used. The discretisation of the boundary in surface elements (segments in 2-D) and vertices is adequate to make particles enter progressively so that no pressure wave are created by the release of new fluid particles. Some details or how to integrate the geometrical renormalisation factor used in the SPH boundary conditions is presented in Appendix. The fourth Chapter presents the ALE Finite Volumes algorithm developed in the massively parallel open-source code code_saturne. An original mixing of cell-based numerical scheme used to get conservation of mass and momentum on each cell control volume and a vertex-based scheme based on the Compatible Discrete Operators (CDO) approach is presented with a particular care on the free-surface condition both on fluid and mesh-displacement. Various verification and validation test cases are presented. Space discretisation of a Poisson equation, used for the mass correction step in the ALE Finite Volumes approach, is presented in Appendix. (10.70675/da1bc2d2zbf9bz46bfz9953z85abe865d07e)
  DOI : 10.70675/da1bc2d2zbf9bz46bfz9953z85abe865d07e
• Scale invariant relationship between rainfall kinetic energy and intensity in Paris region: An evaluation using universal multifractal framework
  
  • Jose Jerry
  • Gires Auguste
  • Tchiguirinskaia Ioulia
  • Roustan Yelva
  • Schertzer Daniel
  Journal of Hydrology, Elsevier, 2022, 609, pp.127715. To calculate the effect of rainfall in detaching particles and initiating soil erosion, or in eroding wind turbine leading edge, it is important to measure recorded drop size distributions (DSD) and fall velocity over long period. Commonly used relationships between kinetic energy (KE) and rainfall rate (R) exhibit strong dependence on the temporal resolution at which the analysis is carried out. Here we aim at developing a new scale invariant relationship relying on the framework of Universal Multifractals (UM), which is widely used to analyze and characterize geophysical fields that exhibit extreme variability across wide range of scales. Rainfall data is collected using three optical disdrometers working on different underlying technologies (one Campbell Scientific PWS100 and two OTT Parsivel 2 instruments) and operated by the Hydrology Meteorology and Complexity laboratory of École des Ponts ParisTech in Paris area (France). They provide access to the size and velocity of drops falling through sampling areas of few tens of cm 2. Such data enables estimation of rainfall DSD, R and KE at various resolutions. The temporal variations of this geophysical data over wide range of scales are then characterized in the UM framework, which was never done for KE. A new power law relation is developed and tested against the theoretical Preprint submitted to Elsevier framework assuming gamma DSD for describing the dependence between KE and R. The developed equation using scale invariant features of UM does not rely on gamma DSD assumption, performs as well as the existing tools, and is valid not only at a single scale, but also across scales. (10.1016/j.jhydrol.2022.127715)
  DOI : 10.1016/j.jhydrol.2022.127715
• Influence of emission size distribution and nucleation on number concentrations over Greater Paris
  
  • Sartelet Karine
  • Kim Youngseob
  • Couvidat Florian
  • Merkel Maik
  • Petäjä Tuukka
  • Sciare Jean
  • Wiedensohler Alfred
  Atmospheric Chemistry and Physics, European Geosciences Union, 2022, 22, pp.8579-8596. With the growing evidence that high particle number concentrations may impact health, modelling their emissions and understanding formation processes is necessary, especially in cities where many people are exposed. As emission inventories of particle numbers and size distribution over cities are usually not available, a methodology is defined to estimate them from PM<SUB>2.5</SUB> emissions and ratios of PM<SUB>1</SUB> / PM<SUB>2.5</SUB> and PM<SUB>0.1</SUB> / PM<SUB>2.5</SUB> by activity sector. In this methodology, a fitting parameter α<SUB>em</SUB> is used to redistribute the number concentrations in the lowest emission diameter range. This parameter is chosen by comparing measured and simulated number concentrations during non-nucleation days. The emission size distribution is then finely discretised by conserving both mass and number in each of the size ranges where emissions are specified. The methodology is applied over Greater Paris during the MEGAPOLI campaign (July 2009). Three-dimensional simulations are performed using the chemistry transport model Polair3D/Polyphemus coupled to the aerosol module SSH-aerosol to represent the evolution of particles by condensation, evaporation, coagulation, and nucleation, with a sectional approach for the size distribution. The model is first compared to measurements during non-nucleation days, and the influence over the month of July 2009 of three different nucleation parameterisations is assessed, i.e. binary (sulfuric acid, water), ternary (sulfuric acid, ammonia, water), and heteromolecular (extremely low-volatility organic compounds (ELVOCs) from monoterpenes and sulfuric acid). The modelled number concentrations compare very well to measurements, with an average normalised mean error of 42 % for the daily number concentrations of particles larger than 10 nm and 37 % for the number concentrations of particles larger than 100 nm. The influence of the binary nucleation is low, and the ternary nucleation scheme leads to better simulated number concentrations (in terms of bias and error) at only one site out of three, but it systematically reduces the model to measurement correlation, suggesting that ternary nucleation may not be the dominant process in new particle formation. However, the relative bias and error, as well as the correlation at suburban sites, are systematically improved using the heteromolecular nucleation scheme involving sulfuric acid and ELVOCs from monoterpenes. This suggests that heteromolecular nucleation may be important in cities, especially at suburban sites in summer, and that a better characterisation of the emissions of ELVOC precursors from traffic is needed. (10.5194/acp-22-8579-2022)
  DOI : 10.5194/acp-22-8579-2022
• Numerical Analysis of the Atmospheric Boundary-Layer Turbulence Influence on Microscale Transport of Pollutant in an Idealized Urban Environment
  
  • Nagel Tim
  • Schoetter Robert
  • Masson Valéry
  • Lac Christine
  • Carissimo Bertrand
  Boundary-Layer Meteorology, Springer Verlag, 2022. The mesoscale atmospheric model Meso-NH is used to investigate the influence of the mesoscale atmospheric turbulence on the mean flow, turbulence, and pollutant dispersion in an idealized urban-like environment, the array of containers investigated during the Mock Urban Setting Test field experiment. First, large-eddy simulations are performed as in typical computational fluid dynamics-like configurations, i.e., without accounting for the atmospheric boundary-layer (ABL) turbulence on scales larger than the building scale. Second, in a multiscale configuration, turbulence of all scales prevailing in the ABL is accounted for by using the grid-nesting approach to downscale from the meso-to the microscale. The building-like obstacles are represented using the immersed boundary method and a new turbulence recycling method is used to enhance the turbulence transition between two nested domains. Upstream of the container array, flow characteristics such as wind speed, direction and turbulence kinetic energy are well reproduced with the multiscale configuration, showing the efficiency of the grid-nesting approach in combination with turbulence recycling for downscaling from the meso-to the microscale. Only the multiscale configuration is able to reproduce the mesoscale turbulent structures crossing the container array. The accuracy of the numerical results is evaluated for wind speed, wind direction, and pollutant concentration. The microscale numerical simulation of wind speed and pollutant dispersion in an urban-like environment benefits from taking into account the ABL turbulence. However, this benefit is significantly less im (10.1007/s10546-022-00697-7)
  DOI : 10.1007/s10546-022-00697-7
• O3–NOy photochemistry in boundary layer polluted plumes: insights from the MEGAPOLI (Paris), ChArMEx/SAFMED (North West Mediterranean) and DACCIWA (southern West Africa) aircraft campaigns
  
  • Thera Baye
  • Dominutti Pamela
  • Colomb Aurélie
  • Michoud Vincent
  • Doussin Jean-François
  • Beekmann Matthias
  • Dulac François
  • Sartelet Karine
  • Borbon Agnès
  Environmental Science : Atmospheres, Royal Society of Chemistry, 2022, 2 (4), pp.659-686. The ozone–NOy photochemistry is explored in contrasting polluted plumes sampled with the Safire ATR 42 research aircraft during three summer field international campaigns in the megacity Paris, the North West Mediterranean basin (WMB) and southern West Africa (SWA). Various metrics derived from the photostationary steady state (PSS) and the ozone production efficiency (OPE) are calculated from airborne observations. A new metric, the oxidant production rate normalized to carbon monoxide (PROx), is introduced and quantified as a function of the processing time of the plume. In most of the polluted plumes, it is found that the Leighton ratio (F) characterizing the equilibrium between O3 and NOx is, on average, within the PSS range ([1 0.32]) or greater. The positive dependence of Ox to NO usually indicates a VOC-sensitive regime inside the plumes with some exceptions. In Paris, under oceanic westerly winds, and during DACCIWA, the plumes show a rural-like chemistry behaviour at moderate NOx levels (NOx-sensitive). Intense and frequent rapid changes in J(NO2), NO and NO2 explain the deviations from the PSS. The OPE for Paris plume suggests that the VOC-sensitive regime extends far beyond the urban plume. The mean ozone production is higher downwind of Paris (30 ppb h1 on average) compared to SWA (20 ppb h-1) and WMB (6 ppb h1). PROx values vary between 0 (no oxidantproduction) and 0.27 ppb[Ox] ppb[CO]1 h1. The determined uncertainty on the Leighton ratio value could affect the differences in the estimation of the photochemical oxidant production by PO3 and PROx. The emissions of CO along the flight path and the presence of vegetation and high humidity levels might shape the oxidant production depending on the explored environment. While limited in number, PROx values set a benchmark for future photochemical studies to compare with: Paris as representative of an anthropogenic urban plume and WMB as representative of a biogenic continental plume. (10.1039/d1ea00093d)
  DOI : 10.1039/d1ea00093d
• GENerator of reduced Organic Aerosol mechanism (GENOA v1.0): an automatic generation tool of semi-explicit mechanisms
  
  • Wang Zhizhao
  • Couvidat Florian
  • Sartelet Karine
  Geoscientific Model Development, European Geosciences Union, 2022, 15 (24), pp.8957-8982. This paper describes the GENerator of reduced Organic Aerosol mechanism (GENOA) that produces semi-explicit mechanisms for simulating the formation and evolution of secondary organic aerosol (SOA) in air quality models. Using a series of predefined reduction strategies and evaluation criteria, GENOA trains and reduces SOA mechanisms from near-explicit chemical mechanisms (e.g., the Master Chemical Mechanism – MCM) under representative atmospheric conditions. As a consequence, these trained SOA mechanisms can preserve the accuracy of detailed gas-phase chemical mechanisms on SOA formation (e.g., molecular structures of crucial organic compounds, the effect of “non-ideality”, and the hydrophilic/hydrophobic partitioning of aerosols), with a size (in terms of reaction and species numbers) that is manageable for three-dimensional (3-D) aerosol modeling (e.g., regional chemical transport models). Applied to the degradation of sesquiterpenes (as β-caryophyllene) from MCM, GENOA builds a concise SOA mechanism (2 % of the MCM size) that consists of 23 reactions and 15 species, with 6 of them being condensable. The generated SOA mechanism has been evaluated regarding its ability to reproduce SOA concentrations under the varying atmospheric conditions encountered over Europe, with an average error lower than 3 %. (10.5194/gmd-15-8957-2022)
  DOI : 10.5194/gmd-15-8957-2022
• Parameterizing the aerodynamic effect of trees in street canyons for the street network model MUNICH using the CFD model Code_Saturne
  
  • Maison Alice
  • Flageul Cédric
  • Carissimo Bertrand
  • Wang Yunyi
  • Tuzet Andrée
  • Sartelet Karine
  Atmospheric Chemistry and Physics, European Geosciences Union, 2022, 22 (14), pp.9369-9388. Trees provide many ecosystem services in cities such as urban heat island reduction, water runoff limitation, and carbon storage. However, the presence of trees in street canyons reduces the wind velocity in the street and limits pollutant dispersion. Thus, to obtain accurate simulations of pollutant concentrations, the aerodynamic effect of trees should be taken into account in air quality models at the street level. The Model of Urban Network of Intersecting Canyons and Highways (MUNICH) simulates the pollutant concentrations in a street network, considering dispersion and physico-chemical processes. It can be coupled to a regional-scale chemical transport model to simulate air quality over districts or cities. The aerodynamic effect of the tree crown is parameterized here through its impact on the average wind velocity in the street direction and the vertical transfer coefficient associated with the dispersion of a tracer. The parameterization is built using local-scale simulations performed with the computational fluid dynamics (CFDs) code Code_Saturne. The two-dimensional CFD simulations in an infinite street canyon are used to quantify the effect of trees, depending on the tree characteristics (leaf area index, crown volume fraction, and tree height to street height ratio) using a drag porosity approach. The tree crown slows down the flow and produces turbulent kinetic energy in the street, thus impacting the tracer dispersion. This effect increases with the leaf area index and the crown volume fraction of the trees, and the average horizontal velocity in the street is reduced by up to 68 %, while the vertical transfer coefficient by up to 23 % in the simulations performed here. A parameterization of these effects on horizontal and vertical transfers for the street model MUNICH is proposed. Existing parameterizations in MUNICH are modified based on Code_Saturne simulations to account for both building and tree effects on vertical and horizontal transfers. The parameterization is built to obtain similar tree effects (quantified by a relative deviation between the cases without and with trees) between Code_Saturne and MUNICH. The vertical wind profile and mixing length depend on leaf area index, crown radius, and tree height to street height ratio. The interaction between the trees and the street aspect ratio is also considered. (10.5194/acp-22-9369-2022)
  DOI : 10.5194/acp-22-9369-2022
• MUNICH v2.0: a street-network model coupled with SSH-aerosol (v1.2) for multi-pollutant modelling
  
  • Kim Youngseob
  • Lugon Lya
  • Maison Alice
  • Sarica Thibaud
  • Roustan Yelva
  • Valari Myrto
  • Zhang Yang
  • André Michel
  • Sartelet Karine
  Geoscientific Model Development, European Geosciences Union, 2022, 15, pp.7371-7396. A new version of a street-network model, the Model of Urban Network of Intersecting Canyons and Highways version 2.0 (MUNICH v2.0), is presented. The comprehensive aerosol model SSH-aerosol is implemented in MUNICH v2.0 to simulate the street concentrations of multiple pollutants, including secondary aerosols. The implementation uses the application programming interface (API) technology so that the SSH-aerosol version may be easily updated. New parameterisations are also introduced in MUNICH v2.0, including a non-stationary approach to model reactive pollutants, particle deposition and resuspension, and a parameterisation of the wind at roof level. A test case over a Paris suburb is presented for model evaluation and to illustrate the impact of the new functionalities. The implementation of SSH-aerosol leads to an increase of 11 % in PM<SUB>10</SUB> concentration because of secondary aerosol formation. Using the non-stationary approach rather than the stationary one leads to a decrease in NO<SUB>2</SUB> concentration of 16 %. The impact of particle deposition on built surfaces and road resuspension on pollutant concentrations in the street canyons is low. (10.5194/gmd-15-7371-2022)
  DOI : 10.5194/gmd-15-7371-2022
• Parametrization of Horizontal and Vertical Transfers for the Street-Network Model MUNICH Using the CFD Model Code_Saturne
  
  • Maison Alice
  • Flageul Cédric
  • Carissimo Bertrand
  • Tuzet Andrée
  • Sartelet Karine
  Atmosphere, MDPI, 2022, 13 (4), pp.527. Cities are heterogeneous environments, and pollutant concentrations are often higher in streets compared with in the upper roughness sublayer (urban background) and cannot be represented using chemical-transport models that have a spatial resolution on the order of kilometers. Computational Fluid Dynamics (CFD) models coupled to chemistry/aerosol models may be used to compute the pollutant concentrations at high resolution over limited areas of cities; however, they are too expensive to use over a whole city. Hence, simplified street-network models, such as the Model of Urban Network of Intersecting Canyons and Highways (MUNICH), have been developed. These include the main physico-chemical processes that influence pollutant concentrations: emissions, transport, deposition, chemistry and aerosol dynamics. However, the streets are not discretized precisely, and concentrations are assumed to be homogeneous in each street segment. The complex street micro-meteorology is simplified by considering only the vertical transfer between the street and the upper roughness sublayer as well as the horizontal transfer between the streets. This study presents a new parametrization of a horizontal wind profile and vertical/horizontal transfer coefficients. This was developed based on a flow parametrization in a sparse vegetated canopy and adapted to street canyons using local-scale simulations performed with the CFD model Code_Saturne. CFD simulations were performed in a 2D infinite street canyon, and three streets of various aspect ratios ranging from 0.3 to 1.0 were studied with different incoming wind directions. The quantities of interest (wind speed in the street direction and passive tracer concentration) were spatially averaged in the street to compare with MUNICH. The developed parametrization depends on the street characteristics and wind direction. This effectively represents the average wind profile in a street canyon and the vertical transfer between the street and the urban roughness sublayer for a wide range of street aspect ratios while maintaining a simple formulation. (10.3390/atmos13040527)
  DOI : 10.3390/atmos13040527