Economical portable sensor based hybrid monitoring for high-resolution air pollution mapping at an urban hotspot

Urban areas in developing countries are facing challenges in air quality management due to high spatio-temporal variations in emission sources. This complexity requires innovative ways of assessment and management of air quality within the city. The present work provides a roadmap for hybrid monitoring-based air quality assessment and local air quality management plan (LAMP) for urban hotspot. In this study, fixed and mobile economical portable sensors (EPS) are deployed around a continuous ambient air quality monitoring station (CAAQMS) to assess the trends in air quality of the area. The pre-evaluated EPS are used to accurately capture the hyperlocal variations in the pollution level around an expensive regulatory monitoring station in Delhi, India. The micro-meteorology around the CAAQMS is also taken into account by fixing additional weather stations in different directions. The findings indicate high monthly variations in PM_2.5 (160-201 µg/m³) and NO₂ (41–56 µg/m³) concentrations within a small 2 km radial area around a CAAQMS. The polarplot analysis indicates that local sources are responsible for pollution level. Based on correlation analysis, PM_2.5 dispersion around CAAQMS is correlated well with relative humidity (RH) (r² = 0.58). It is also observed that green area enhance RH and reduce ambient temperature which ultimately influences the pollutant dispersion. This robust assessment of air quality variations at micro scale brings the need for designing of effective and efficient mitigation measures at the local level for hotspots.