Make the Invisible Visible: Reveal the Magnetic Field and Air Pollution to Foster Engagement in a Community-Based Participatory Research Project

Citizen science is increasingly recognized as essential for engaging the public in participatory sustainability research and for addressing the complex challenges of the Anthropocene. However, fostering meaningful dialogue between science and society remains difficult, often hindered by limited opportunities for interaction and varying levels of scientific understanding.Identifying outreach formats that foster citizen engagement and initiate productive exchanges between scientists and the public is therefore a key challenge.Here, we present a hands-on science outreach workshop designed to promote participation in science and foster dialogue between citizen and researchers. The workshop demonstrates the use of tree bark as a biomonitor of urban air quality through magnetic methods. It was conducted in schools and science fairs between 2018 and 2023, reaching 850 participants across nine scientific outreach events and 195 children in three elementary schools. The workshop, originally developed to engage with residents and introduce our approach and underlying concepts prior to participation in the NanoEnvi participatory research project, prompted more than 150 people to participate in the NanoEnvi community-based participatory research project, which offered to host passive biosensors to monitor air quality in their homes or at school in the Toulouse city (France). The workshop included three hands-on demonstrations and experiences. It invited participants to (i) discover the magnetic phenomena, (ii) extract airborne magnetic particles from soils, and (iii) measure air pollution trapped on bark like a scientist. The workshop was also accompanied by lectures and an exhibition.We observed that the workshop fostered two-way dialogue between researchers and a wide range of participants, creating opportunities for shared experimentation and knowledge co-production. We also found that the positive emotions raised by hands-on exploration of magnetic phenomena during the workshop led to engagement in a participatory project on potential air pollution in urban surroundings. These results led us to identify four key lessons: protocol evolution, science-society dialogue, inter-science communication, and eco-anxiety mitigation, highlighting the potential of hands-on geoscience outreach activities to strengthen science-society interactions.