The drone with the payloads PM-LCS, AE-51 micro-Aethalometer, and meteorological sensors. Credit: Ajit Ahlawat
Air pollution in Delhi’s post-winter haze season has long posed a threat to public health, yet most measurements focus on ground-level PM 2.5 concentrations, leaving vertical profiles poorly understood.
Researchers from IIT Delhi, Post Graduate Institute of Medical Education and Research, Chandigarh and collaborators used drones1 equipped with low-cost particulate matter sensors to record vertical PM2.5 profiles during March 2021. They found unexpectedly high concentrations of 160 µg/m³ at 100 m, around 60% higher than near the surface.
Humidity above 70% promoted the growth of secondary inorganic aerosols, particularly ammonium nitrate and chloride, suggesting that multiphase chemistry aloft plays a critical role in early-morning haze formation.
Comparisons with the WRF-Chem atmospheric model revealed significant underestimation of PM2.5 during hazy mornings, linked to a dry bias that prevents the model from capturing aerosol water uptake and secondary aerosol formation.
The study shows that drone-mounted low-cost sensors are an effective tool for probing the lower atmospheric boundary layer, providing insights that can improve air quality monitoring, model evaluation, and mitigation strategies in megacities like Delhi.
