Résumé
Can the magnetic measurements of relative fine particle concentrations be brought to a degree of confidence such that they could be used in future public policies? Through the participation of more than thirty households, a micro-scale air quality measurement study was made possible in a canyon street in Montpellier (France) where the traffic is about 7000 veh/day on a single line. Indeed, a kit containing the instructions, the installation protocol and two types of prototype passive dust filters: one for magnetic measurements and one other for chemical measurements have been distributed to the citizens. Some of them also received pots of ivy. The charge accumulation time was set to 3 months. The idea is to confront chemical measurements (providing information about the source of pollutants) with magnetic measurements of the relative concentration of traffic pollutants. The results from isothermal remanent magnetization measurements (IRM) at 100, 300 and 1000 mT show a magnetic saturation at 100 mT, suggesting a predominance of magnetite. Maximum IRM values are found for the balconies situated at the street level and the first floors. These results assume that the fine traffic-related particles remain trapped near to the source before dispersion. Hence, the magnetic method seems to be a suitable tool, able to precisely 3D-map relative concentration of pollutants at a street level.In order to suggest some mitigation solutions, we built a wind tunnel to perform analogical experiments on different Mediterranean endemic species. Particle matter (PM) concentrations upwind and downwind of natural reconstituted hedges are provided by two optical particle counters (LOAC). The interest would ultimately combine PM concentrations measured by size bins from the LOACs with magnetic measurements (ARM, IRM100mT, IRM 300mT and SIRM) of plant leaves and be eventually able to precisely determine the in situ dust removal rate by urban greens with environmental magnetism measurements.