Air pollution during Phase-1 and Phase-II of odd-even period in Delhi

Abstract

The latest WMO estimate shows that 13 of 20 most polluted cities in the world are in India, including the worst ranked city, Delhi. For the past couple of years, the level of pollutants in this city has been 3-4 times above the safe standards. The Supreme Court of India has directed the policy makers to take suitable steps to bring down the level of pollution to the safe standard. To decrease the pollution level, the Government of Delhi has taken several steps; one recent among them, as a test, is vehicle rationing for the period 1-15 January 2016 and 15-30 April 2016. By taking observations during these periods, Government wanted to know if the pollution had decreased. In this program, vehicles whose number end in odd like 1, 3, 5, 7, 9 were allowed to ply on odd days like January 1, 3 etc. and vehicles with numbers end in even like 0, 2, 4, 6, 8 were allowed to ply on even days like January 2, 4 etc. Sundays were exempted. In this short communication, we are reporting the pollution level of Delhi during these two periods. The average values of PM2.5 and PM10 (particulate matter) during these periods were 205 µg/m³ and 326 µg/m³ respectively during 1-15 January and 96 µg/m³ and 179 µg/m³ during 15-30 April which were much higher than the safe limit 60 and 100 µg/m³. There was an increase in the pollution level during the event fortnight compared to the pervious fortnight which decreased in the next fortnight. The average values of surface ozone during phase-I and phase-II were 24 ppb (parts per billion by volume) and 46 ppb against the safe limit of 180 ppb. During phase-I, PM2.5, PM10 and O₃ has a decreasing trend and during phase-II they show an increasing trend. We have also examined the effect of wind, humidity and temperature on pollution level. Pollutants do not appear to have been much affected by temperature and humidity, but their trend is in phase with the wind speed. Results are presented here.