Lockdown cuts PM2.5, PM10 levels by half in Delhi: CPCB

With very few vehicles on ros, only essential commercial units functioning due to coronavirus-forced lockdown and a wear favourable for dispersion of pollutants, Central Pollution Control Board (CPCB) has reported 46 percent reduction in PM2.5 levels and 50 percent depletion in PM10 concentrations in national capital.

apex pollution control body has analysed data from continuous ambient air quality monitoring network of 38 stations in Delhi between March 16 and April 15. Air quality trends have been studied in two phases pre-lockdown phase of March 16 to 21 and lockdown phase from March 25 to April 15. In its report, CPCB said, "Significant reduction in PM2.5, PM10 and 2 levels observed. Overall, 46 per cent reduction in PM2.5 and 50 per cent reduction in PM10 concentration observed during lockdown period."

PM2.5 refers to particulate matter having diameter less than 2.5 micrometers which can enter lungs and even bloodstream. CPCB said reduction in PM10 and PM2.5 levels primarily indicate depletion in combustion and industrial sources of pollution which are common to both fractions of particulate matter.

Since 81 per cent of Delhi's nitrogen oxide comes from transport sector, according to TERI Emission Inventory, 2018, restrictions on vehicular activity led to 56 per cent reduction in 2 levels and over 37 per cent cut in carbon moxide (CO) concentration during lockdown period, compared to pre-lockdown period, it said. Due to restrictions on transport sector and industrial operations, two major sources of benzene emissions, a 47 percent reduction in benzene level has been observed, CPCB report stated.

"However, only 19 percent reduction was seen in sulphur dioxide levels which may be due to fact that over 70 percent of Delhi's SO2 originates from power plants located around national capital (as per TERI Emission Inventory, 2018) and power plants were operational during lockdown period," it ded. Since most of eateries and industries in Delhi have shifted from coal to or less polluting energy sources, power plants appear to be most likely source of sulphur dioxide.

CPCB also analysed data from 13 pollution hotspots in Delhi. Anand Vihar recorded 62 percent, 69 percent and 72 percent reduction in PM2.5, PM10 and 2 levels respectively during lockdown period, report said, ding Vivek Vihar, which is near major traffic corridor GT Ro, saw a 60 percent reduction in 2 levels.

In Dwarka Sector-8, PM2.5, PM10 and 2 levels depleted by 48 per cent, 61 per cent and 68 per cent respectively, while Okhla recorded a 72 per cent reduction in nitrogen dioxide levels, CPCB said. apex pollution control body recorded 24 hourly aver PM2.5 and PM10 levels within National Ambient Air Quality Standards (NAAQS) for 20 and 15 days respectively in 22 days of lockdown period. 2 levels were 75 per cent less than ir 24 hourly standard.

Twenty-four-hour avers of PM10, PM2.5, 2 and SO2 levels dropped as low as 24 microgrammes per cubic meter, 39 µg/m3, 15 µg/m3 and 10 µg/m3 respectively during lockdown period, report said.

A 27 percent increase in PM2.5 level and a 65 percent increase in PM10 concentration was observed in between April 7 to April 15 compared to first two weeks of lockdown March 25 to April 6. However, CPCB said, PM2.5 and PM10 levels were still lower by 39 percent and 35 percent respectively than pre-lockdown concentrations. This may primarily be attributed to change in meteorological conditions.

onset of summers has led to dry and dusty conditions. A mild dust storm from western part of country and gulf region hit Delhi on April 14-15 rapidly increasing PM10 levels in Delhi and NCR, pollution control body said.