Vertical distribution of particulate matter near a national highway and influence of roadside tree canopy: A drone/UAV based study

Measurement of PM near roadways has been of major interest due to high contributions of traffic to the overall PM. This paper presents the results from a study that used an unmanned aerial vehicle (UAV, also known as drones) platform to obtain measurements of PM and meteorological parameters up to 100 m above ground level near an open highway, and to understand the influence of tree canopy on the PM distribution. The study involved 42 flights over a period of two days, conducted adjacent to a national highway in India. The overall mean profile for flights conducted behind the tree canopy shows a decrease in PM mass concentrations with an increase in altitude. However, for the near-road flights, the PM concentrations tend to increase with altitude, followed by a gradual decline for a few flights. For the flights near the road, the results show that the mean values of PM1 1 and PM 2.5 mass concentrations at higher altitudes are 16% and 8% higher than the respective ground level concentrations. On the contrary, the mean PM10 10 mass concentrations at higher altitudes are 6% lower than that at the ground level. For the flights behind tree canopy, the results are different when compared to the flights near the road. The mean mass concentrations for all 3 p.m., PM 2.5 and PM10 10 particles at higher altitudes are 20%, 19% and 21% lower than the respective ground level measurements. Also, the PM1, 1 , PM 2.5 and PM10 10 mass concentrations for the flight behind tree canopy cover are 29 %, 24 % and 11 % lower than the near-road flights respectively. The results also showed the concentrations behind the tree canopy remained low for the entire altitude of-100 m.