One of the main reasons the scientists stress on knowing the APT index is to help keep a locality's air pollution under check. Like humans, trees also have the capacity to tolerate a certain level of pollution in their surroundings. A study to understand the tolerance to air pollutants among trees growing around the Lohegaon area of the city has found that peepal trees are the most tolerant, whereas tamarind trees are highly sensitive.
Researchers Satish Kulkarni and Erum FH Kazi calculated the Air Pollution Tolerance Index (APTI) of trees growing around the airport locality during two successive winters of 2017 and 2018. This index analyses the health of trees and such information can come in handy while planning location-specific tree plantation drives,
In order to calculate the APTI, concentrations of Particulate Matter (PM) 10, PM 2.5, NOx and SOx were considered. Their effect — on the total chlorophyll, water content, pH level and concentration of ascorbic acid in the leaves of the trees growing along the roads in Lohegaon— was studied.
“From the six samples of various trees collected, peepal trees were found to be the most tolerant to air pollution. More of these should be planted in the locality, so that it helps improve the air quality of an area,” said Kazi, lead author and assistant professor at the Department of Environmental Science, Abeda Inamdar Senior College.
The researcher-duo concluded that Rain tree, the Indian Rosewood, mango and neem trees had decreasing tolerance levels, respectively, in the locality. This air pollution tolerance level showcased by trees, Kazi said, could show area-wise variations, as she is presently studying 24 locations in Pune city.
One of the main reasons the scientists stress on knowing the APT index is to help keep a locality’s air pollution under check. “Ascorbic acid in the trees has a defence mechanism, wherein it absorbs unwanted gases present in the atmosphere and ensures only the required gases, like carbon di-oxide, reach the leaves. This ensures longevity for the trees which continue to purify the air in the surroundings,” explained Kulkarni, head of the Department of Environmental Science at the New Arts and Commerce College, Ahmednagar.
Every year, the number of vehicles hitting the city streets is increasing and this contributes directly to the observed deteriorating air quality in the city, noted Kulkarni. PM 10 level was at its peak during December and January months, while Nitrogen Oxide touched maximum level in February, the study noted.
“The peripheral areas of Pune city are seeing an increase in air pollution levels. New constructions and a decrease in the tree cover have left the air around areas of Yerwada, Pune camp, Wakad, Hinjewadi and Wakad areas highly polluted. The old Pune city is also no less polluted,” said Kulkarni.
Large trees with wide canopy mean that the surface available for absorbing pollutants, both gaseous and particulate, is higher. The air quality around Empress Garden was relatively less polluted, given that the wide variety of the large garden acts as a pollution sink for the locality, said Kulkarni.
On the pollution levels in the locality, Kazi said, ” Vehicle emissions were the major contributors for the high pollution during winter months around Lohegaon. This included contributions by aircraft from the neighbouring Pune airport.”