<p>In this work, we will present 4 different approaches to study and visualize the effects of motorway infrastructures such as precast noise barriers or vegetated flat-top earth berms on the dispersion of traffic-related pollutants. The micrometeorological characteristics that directly affect the dispersion of pollutants in the atmosphere were first computed with a pseudo-3-dimensional CFD model by means of the openFoam toolbox. The strengths of this model based on the Reynolds-Averaged Navier–Stokes (RANS) equations with K-ε first-order closure model is to consider the traffic-induced momentum and turbulence (Letaïef et al., 2020). A second approach was to directly visualize the microturbulence from a 1/100 scale model of the motorway cross-section in a wind tunnel. To this end, we refracted the beam of a laser light with a glass rod to observe eddies along a thin plane through a fog generated by a fog machine. Simple shots with a camera can reveal coherent patterns in the chaos. To complete these two models, we conducted two types of field measurements of fine particle concentrations on the studied motorway sector. Direct and indirect measurements were carried out with low-cost microsensors and with environmental magnetism tools applied on dust depositions on accumulating surfaces (Hofman et al., 2017), respectively.</p> <p>These four approaches indicates similar results. A large recirculation wake region formed on the leeward side of the wall that brings back to the wall the pollutant generated by the traffic is evidenced. On the contrary, flat-top earth berms favor the dispersion of pollutants in the atmosphere. These 4 different approaches allowed us not only to establish these conclusions but also to communicate with all the actors concerned by this study site: scientists specialized in the metrology of atmospheric pollutants, the persons in charge of the motorway company, the elected representatives and the inhabitants of the city where the study site is located. </p> <p>References:</p> <p>Hofman, J., Maher, B. A., Muxworthy, A. R., Wuyts, K., Castanheiro, A., and Samson, R.: Biomagnetic Monitoring of Atmospheric Pollution: A Review of Magnetic Signatures from Biological Sensors, Environ Sci Technol, 51, 6648–6664, https://doi.org/10.1021/acs.est.7b00832, 2017.</p> <p>Letaïef, S., Camps, P., Poidras, T., Nicol, P., Bosch, D., and Pradeau, R.: Biomagnetic monitoring vs. CFD modeling: A real case study of near-source depositions of traffic-related particulate matter along a motorway, Atmosphere, 11, 1–23, https://doi.org/10.3390/atmos11121285, 2020.</p>

<p>In the context of a double democratic and environmental crisis, participatory/collaborative action-research has multiplied in recent years with increased attention from institutions. Over the last ten years, many participatory research projects have taken up the democratic and environmental crises by proposing an emancipatory normative scheme to improve public participation and the effectiveness of environmental action.</p> <p>Our paper presents the first results of a participatory science project, BREATHE, funded by the ANR. It aims to articulate two components : (1) a participatory measurement of fine particulate matter (PM) concentration (PM 10 - PM 2.5 - PM 1 - PM 0.1) and an identification of pollution sources) from passive filters (plants and sensors) and micro-sensors subject to standardization (2) a component of accompaniment and support of public policies based.</p> <p>The project is based on a participatory science protocol (Chevalier and Buckles, 2009) based on participation engineering (Dosias-Perla et al., 2020). Our fieldwork covers three targets: (a) the incinerator (waste recovery center) - (b) a highways around a small town; (c) a street canyon, city of Montpellier, south of France. On the metrological level, the project aims at analyzing the implication and the effects of the Citizen Science device aiming at "co-constructing" at micro-scales a fine cartography of fine particles concentrations while discriminating the source and modeling the dispersion phenomena. On the political level, the project aims on the one hand to analyze the institutionalization process of the device and on the other hand to analyze its effects on the "co-production" of public policies and strategies through different regulatory frameworks (EPZ, PCAET, Mobility Plan, etc.).</p> <p>We will also discuss the limits and contributions of this type of interdisciplinary and participatory approach aiming at acting on pollution with and for society. We will present current results and first analyses concerning the complex intertwining of technical and political issues related to air quality metrology, the importance and difficulties of standardizing measurement and of truly developing metrology at relevant scale levels when it comes to supporting public action and addressing health issues</p>