| Popis: |
The chronic exposure to particulate matter (PM) pollution causes harmful effects on humans, especially in urban areas where most of them are notably exposed to vehicular traffic. Since a decade, magnetic monitoring demonstrates its efficiency for mapping relative concentration of those particles. To better understand what is measured with the magnetic techniques, it becomes essential to discriminate each traffic-related source in the total magnetic signal measured on accumulative surfaces acting as pollutant samplers. To achieve this goal, this study presents a set of measurements related to magnetic grain-size and/or to magnetic mineralogy (hysteresis parameters and FORCs diagrams, temperature dependency of low field susceptibility and unmixing of the IRM acquisition curves) for exhaust (14 diesel and gasoline tailpipes) and non-exhaust sources. Within the latter category we characterized abrasive-fatigue wear origin samples (six brake-pads and two brake dust samples, four tire tread samples), one asphalt concrete sample and one street dust sample from resuspension origin. We also analyzed mineral dust that are episodically deposited in the western part of Europe by wet process after erosion wear and long-range transport and can be found in traffic-related resuspension products. This study confirms and highlights the relevance of the magnetic approach by being able to identify magnetic properties to characterize and discriminate the different traffic-related source signals. These magnetic properties were compared to those measured on various type of accumulative surfaces (passive and filters of facemasks for cycling, plant leaves and barks). Whether for artificial or biological samplers, their magnetic signals appear to be a combination of source magnetic signals as exhaust pipes and brake wear products amongstothers. |
