MAGNETIC CHARACTERIZATION OF TRAFFIC-RELATED PM TO CHARACTERIZE URBAN AIR POLLUTION

With nearly 4.2 million premature deaths per year worldwide, WHO describes air pollution as "a silent killer". It is also regularly cited in the press as a major threat to health and the climate. If we are particularly interested in fine particles (PM) suspended in the air, they consist of a heterogeneous mixture of organic and inorganic materials. In urban areas, it is the traffic which represents the main source of emissions with the involvement of the processes of abrasion (tires, brakes and clutch), fuel combustion and resuspension of particles previously deposited on traffic lanes. Numerous studies have already shown the ability of environmental magnetism to relatively detect and map the concentrations of particulate matter deposits on accumulating surfaces such as plant leaves or passive filters.

In the interest of mitigation and thus to better understand the capability for trapping PM by urban accumulating surfaces, it seems important to magnetically characterize the potential sources. For this, we will present different parameters measured in rock magnetism such as hysteresis cycles, susceptibility versus temperature curves and cumulative isothermal remanent magnetization curves of different tires, brake pads, exhaust pipes (gasoline and diesel) as well as resuspended dust from anthropogenic (tar and street dust) and natural sources (Saharan sand and volcanic ash). These measurements will be compared with those carried out on plants taken from the vicinity of a motorway and passive filters collected in a canyon street in downtown Montpellier. We will then compare these data with analyzes carried out at the Mössbauer as well as with measurements in trace elements in order to characterize the nature and origin of PM (magnetic) and finally to be able to better constrain the limits of environmental magnetism in the evaluation of the air we breathe in the city.