Monitoring airborne fine particles with biological and technological sensors for preventive conservation of cultural heritage sites.

Ambient particulate pollution in cities may lead to poor indoor air quality in cultural heritage (CH) institutions if preventive actions are not considered and implemented accordingly. This is one of the first studies to propose using technological and biological sensors to monitor both outdoor and indoor environments at CH sites. We studied particulate matter (PM) concentrations in real time using low-cost sensors in three Mexican museums and an archeological zone, where median PM2.5 concentrations exceed the 24-h Air Quality Guidelines level. Leveraging the biological sensor's ability (Tillandsia recurvata) to capture particles, we deployed biomonitoring networks to monitor both outdoor and indoor environments at CH sites over three months and to characterize the magnetic fraction. Micron- and submicron-sized magnetite with spherical and irregular morphologies, co-associated with Cr, Mn, Ni, Cu, and Ba, were detected using magnetic and SEM-EDS techniques. The mean (standard deviation) content of airborne magnetic particles (AMP) decreased from the city center museums to the archeological zone, and from outdoor sites (AMP = 0.12 (0.05) mg) to museums' indoor sites (AMP = 0.06 (0.03) mg). Among urban trees, Ficus benjamina and Fraxinus species were identified as reducing atmospheric particulate matter by retaining it on their leaves; hence, a nature-based solution for preventive conservation in these cultural heritage institutions is proposed.