By Polash Mukerjee:
Note: This story has been republished from Down To Earth.
Winter mornings in Delhi are hardly the best time of the day. Every night, a large number of trucks pass through the city, spewing dirty diesel into the air. Add to that smoke from small fires lit by people for warmth and you end up with a massive build-up of pollutants in the atmosphere. Low temperatures and little or no wind leave even the greenest areas of the capital in the grip of deadly pollution.
Delhi-based non-profit Centre for Science and Environment (CSE) conducted real-time monitoring of particulate matter concentration at Lodi Garden, Nehru Park, Buddha Jayanti Park and Sanjay Jheel, four of the city’s largest parks, in the early morning hours on December 9. In the late morning hours, monitoring shifted to prominent arterial crossings such as Noida link road-NH-24 intersection, Ashram flyover and Nehru Place flyover.
The monitoring, conducted using portable air quality monitoring equipment, revealed that while PM2.5 levels were alarmingly high in both parks and at road intersections, green areas had much higher PM2.5 levels than road crossings.
This trend can be explained by several factors. Firstly, there is a difference in the moisture levels of parks and intersections. Green spaces tend to have a higher accumulation of moisture in the form of dew and humidity, which traps the pollutants close to the ground and contributes to higher PM2.5 concentrations. Secondly, open areas such as arterial roads and spaces near them are windier and see the dispersal of pollutants due to a constant movement of vehicular traffic and high turbulence. In comparison, green spaces see less dispersal of pollutants and act as sinks where the particulate matter tends to settle down and accumulate.
Lastly, there is a marked correlation of temperature with PM2.5 levels. For the exposure study, the parks were monitored during the early morning when temperatures were still low. Arterial roads were monitored in the late morning hours when temperatures were much higher.
These pollution levels could put the health of people, especially children and the elderly, at risk. While many people exercise in public parks in the morning, children and adults are exposed to accumulated pollutants on their way to school and workplaces respectively.