Delhi received its first winter rain over the weekend. Interestingly, this spell of rain considerably decreased air pollution across the national capital.
Rain and cold winds in Delhi also brought down the day temperature to 16°C on Sunday, which is 7 degrees below the normal average.
Air pollution generally increases with drop in temperatures but in this scenario, rain helped washing it down.
Air is full of pollutants including dust particles, particulate matters, salt and other gases. The particulate matter of size less than 2.5 microns (PM 2.5) remains suspended in the air and is known to have serious health consequences including respiratory problems. While gases disperse easily in the air, PM 2.5 remain suspended for longer duration. They are either blown away by strong winds and dispersed due to high temperatures or ideally, washed down by rain.
The figure below clearly shows that the PM 2.5 levels remained way above the permissible limits in R.K. Puram on December 12. With light drizzle on Saturday, air pollution levels started falling and reduced significantly after good showers on Sunday.
As rain subsided, pollution started increasing but fog was witnessed only at the Palam airport on Tuesday morning, thanks to tarmac and high concentration of pollutants and gases.
Fig; 1: PM 2.5 levels in R. K. Puram from December 13 to 16, 2014
Picture courtesy- Delhi Pollution Control Committee
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