Abstract
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 feedbacksfrom 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.