SUMMARY: The chronic exposure to particulate matter (PM) pollution causes societal and environmental issues, in particular in urban areas where most citizen are regularly exposed to vehicular traffic. Since almost two decades, environmental magnetic monitoring has demonstrated its efficiency to successfully map relative concentrations of airborne particle deposition on accumulative surfaces. A better understanding of the magnetic results requires discriminating the main traffic-related sources of the observed signal on particle collectors. To meet this objective, we investigated a sample set of exhaust and non-exhaust sources with respect to their magnetic fingerprints inferred from hysteresis loops, first-order reversal curve (FORC) diagrams, temperature dependency of initial susceptibility and unmixing of isothermal remanent magnetization acquisition curves. The source sample set comprises 14 diesel and gasoline exhaust smoke residues, 12 abrasive-fatigue wear test pieces from worn brake-pads, brake powders, worn tire-tread and three resuspension products: asphalt concrete, street dust and Saharan mineral dust deposited by precipitation after long-range eolian transport. Magnetic properties of the source samples were compared to those from various accumulative surfaces exposed to urban traffic (passive collectors, filters of facemasks for cycling, plant leaves and tree barks). We found some fingerprints of exhaust pipes and brake wear products on these collectors. The findings highlight the relevance of environmental magnetism tools to characterize different traffic-related source signals in accumulative surfaces in urban environment.

The sedimentological, geochemical, physical and magnetic properties of 40 surface and basal sediment samples of box cores collected throughout the Canadian Arctic Archipelago (CAA) from the Canadian Beaufort Shelf to Lancaster Sound were analyzed to determine the sedimentary processes that operate within the CAA during the pre‐ and post‐industrial periods (i.e., before and after 1900 Common Era or CE). In addition, the chronology of seven selected regional cores was established using ²¹⁰Pb measurements, where the base is dated between 1550 and 1820 CE. These cores provide an opportunity to robustly compare post‐1900 sedimentary conditions with those of the colder Little Ice Age period (LIA; ∼1500–1900 CE). The different properties combined with multivariate statistical analyses result in the identification of three regional provinces with distinct sedimentary characteristics: (a) the West province (Mackenzie Shelf/Slope, west Banks Island and M'Clure Strait) typified by detrital associations (Fe‐Rb‐Ti‐Zn), high organic matter inputs, dominance of magnetite and low‐coercivity minerals and high aluminosilicate contents; (b) the Intermediate Zone (Amundsen and Coronation gulfs) distinguished by Si‐Al‐Zr‐Sr‐K associations, Mn oxyhydroxides precipitation, constant high magnetic grain concentrations and a mixture between marine and terrigenous organic matter; and (c) the East Province (Queen Maud Gulf, Victoria and Barrow straits, and Lancaster and Eclipse sounds) described by high detrital carbonate inputs, marine organic matter, a dominance of high‐coercivity minerals and high magnetic concentrations in pre‐industrial samples. Our results confirm that the pre‐ and post‐industrial sedimentary dynamics are controlled by sediment supplies from the river discharges in the West and Intermediate provinces, whereas the East province is more influenced by sea ice and coastal erosion. Basal sediment samples from the seven ²¹⁰Pb‐dated cores suggest an intensification of the Mackenzie, Coppermine, and Ellice rivers runoff, extensive sea‐ice cover and consequently sediment transport by the latter during the LIA period.

A test site located along a 12-lane motorway east of Montpellier, France, is used to evaluate the potential of biomagnetic monitoring on traffic-related particulate matter (PM) to parametrize a computational fluid dynamics (CFD) simulation of the local airflow. Two configurations were established on the site with three vegetated flat-top earth berms of a basic design, and a fourth one was located windward to the traffic roofed with a 4-m-high precast concrete wall. As a first step, PM deposition simultaneously on plant leaves, on low-cost passive artificial filters, and on soils was estimated from proxies supplied by magnetic and X-ray fluorescence measurements on both sides of the motorway. These latter revealed that traffic-related pollutants are present on soils samples highlighted with a clear fingerprint of combustion residues, and wears of breaks, vehicles, and highway equipment. Maximum PM accumulations were detected in the lee of the berm–wall combination, while no significant deposition was observed on both sides of the flat-top earth berms. These results are in line with measurements from PM µ-sensors operated by the regional state-approved air quality agency. Finally, we compared the experimental measurements with the outcomes of a computational fluid dynamics (CFD) modeling based on the Reynolds-Averaged Navier–Stokes (RANS) equations that consider the traffic-induced momentum and turbulence. The CFD modeling matches the experimental results by predicting a recirculated flow in the near wake of the berm–wall combination that enhances the PM concentration, whereas the flat-top berm geometry does not alter the pollutants’ transport and indeed contributes to their atmospheric dispersion.

This paper details the operating experience about a case study carried out as a citizen science approach to monitor magnetic particulate matter (PM) in a street canyon in Montpellier, France. A total of 60 passive filters and 12 Hedera Helix pot plants were deployed in 29 households for a period of 3 months, from December 2020 to March 2021. This street canyon was chosen by the academic team because dwellers were already mobilized against the street traffic and its adverse environmental effect on air quality, and because they were in conflict on this issue with policy makers. Despite the project aimed at including all the stakeholders through co‐construction, dwellers, elected officials, and staff from technical department of the city were not fully embedded. The announcement of the closure of the street to through traffic during the metrological campaign and the absence of agreement curbed their involvement and motivation. However, the feedbacks from the citizen partners promote the fact that this study supported their claims and brought them a deeper understanding on the micro‐scale air quality monitoring. Indeed, it is increasingly difficult for citizens, who seemed specifically interested in what is happening right outside their front door, to understand this measure with the emergence of ever more low‐cost sensors. For that reason, we examined the citizen's degree of confidence in magnetic monitoring of air quality and how can this technique be useful in their claims. The results show that magnetism can be a measurement technique favorable to citizen participation because it provides a large amount of data at the micro‐scale of the street, while the data from the certified associations for monitoring air quality requires a spatial interpolation to map variations on a neighborhood scale. In this study, we proposed a magnetic air quality index to standardize and democratize the magnetic monitoring of air quality to facilitate the dialogue with all stakeholders.

The sedimentological, geochemical, physical and magnetic properties of 40 surface and basal sediment samples of box cores collected throughout the Canadian Arctic Archipelago (CAA) from the Canadian Beaufort Shelf to Lancaster Sound were analyzed to determine the sedimentary processes that operate within the CAA during the pre- and post-industrial periods. In addition, the chronology of seven selected regional cores was established using ²¹⁰ Pb measurements, where the base is dated between 1550 and 1820 CE. These cores provide an opportunity to robustly compare post-1900 sedimentary conditions with those of the colder Little Ice Age period (LIA; ~1500-1900 CE). The different properties combined with multivariate statistical analyses result in the identification of three regional provinces with distinct sedimentary characteristics: (1) the West province (the Mackenzie Shelf/Slope, West Banks Island and the M’Clure Strait) typified by detrital associations (Fe-Rb-Ti-Zn), high organic matter inputs, dominance of magnetite and low-coercivity minerals and high aluminosilicate contents; (2) the Intermediate Zone (the Amundsen and Coronation Gulfs) distinguished by Si-Al-Zr-Sr-K associations, Fe-Mn oxyhydroxyde precipitation and a mixture between marine and terrigenous organic matter; and (3) the East Province (the Queen Maud Gulf, Victoria and Barrow Straits, and Lancaster and Eclipse Sounds) described by high detrital carbonate inputs, marine organic matter, and dominance of high-coercivity minerals. Our results confirm that the pre- and post-industrial sedimentary dynamics are controlled by sediment supplies from the river discharges in the West and Intermediate provinces, whereas the East province is more influenced by sea ice and coastal erosion.