Air quality mapping using PM2.5 sensors on urban buses

Inés González de Castro1, Mar Viana1, José J. Ramasco2, Aina Maín-Nadal1 and Teresa Moreno1

1Institute for Environmental Assessment and Water Research (IDAEA-CSIC), c/ Jordi Girona, 18-26 08034-Barcelona, Spain
2Instituto de Física Interdisciplinar y Sistemas Complejos IFISC (CSIC-UIB), 07122 Palma de Mallorca, Spain.

(March 2026)

Six low-cost air quality sensors were installed on the front roof area of three buses to enable real-time monitoring of air quality across the city of Valladolid (Spain) over a 7-month period, capturing variability in meteorological conditions and emission sources. Prior to deployment, the sensors were placed at a reference station in Barcelona (Spain) for validation and calibration. Measurements deviating by more than 30% from reference values were discarded, and correlation coefficients (Rē) were calculated. After the monitoring campaign, the calibration procedure was repeated. The results (R2 = 0.85) suggest that bus-mounted sensors can effectively support real-time detection of urban air quality changes and contribute to detailed air quality mapping. Integrating data from reference air quality monitoring networks (AQMNs) with low-cost sensor (LCS) systems can strengthen evidence-based policymaking and help refine regulatory frameworks aimed at reducing urban air pollution.

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