The output values of primary pollutants on Friday was observed high on the National Air Quality Index (NAQI) due to the wind blowing from North-West direction towards the the national Capital.
The SAFAR (System of Air Quality and Weather Forecasting and Research), a unit of Ministry of Earth Science (MoES) showed their advisory status as "very poor" which was "moderate" a day before.
Notably, two days before the output values of Particulate Matter (PM) 2.5 on the real time air ambient quality Indexes of the Delhi Pollution Control Committee (DPCC), US embassy and SAFAR oscillated between 7 µgm-3 to 61µgm-3 while it has now significantly increased.
The highest value of PM 2.5 at 6 PM on DPCC meters in R K Puram and Civil lines were 173 and 191 which was three times higher than its prescribed limit which is 60 µgm-3. Mass concentration value of primary pollutant on SAFAR meter was 125.9 µgm-3.
"Although humidity level was less in Delhi air but less wind speed may also be the reason for high concentration of primary pollutants ," said an environmentalist.
TERI, which did an analysis of air quality on Thursday, said the wind blowing from north-west direction was carrying the pollutants towards the national capital.
"PM10 (particles with diameter less than 10 micrometer) and PM 2.5 (particles with diameter less than 2.5 micrometer) concentrations violated the standards at most places in Delhi and NCR. The concentrations are 1-2.3 times above the standard of PM 2.5. These pollutants are responsible for respiratory and cardiovascular diseases," a TERI statement said while sharing April 14 analysis.
While TERI also gave the analysis of Wednesday, it said that Delhiites were breathing "better quality air" as particulate matters which cause respiratory diseases were under the prescribed limits.
The green body said last week the pollutant concentrations came down due to higher wind speeds and enhanced vertical thermal diffusion leading to better dispersion of pollutants but currently the concentrations were again violating the standards at most places in Delhi and NCR.
"Delhi's air quality is also being affected significantly by sources upwind (in North-West directions). Wind is predominantly blowing from North-West direction and carries pollutants towards the city of Delhi. For the same reason, the downwind towns in NCR like Gurgaon, Ghaziabad, and NOIDA show pollutant levels even higher than Delhi, with contributions from Delhi's emissions," it said.
Given the current pollution levels in the city and the Government's odd-even scheme, TERI is carrying out a trend analysis of the three main pollutants PM 10, PM 2.5 and NO2 at nine locations - Mandir Marg, RK Puram, Punjabi Bagh, Anand Vihar, Bahadurgarh, lodhi Road, Ghaziabad, Gurgaon and Noida.
The objective is to analyse the effect of the odd-even scheme on air pollutant concentrations in different parts of the city. The exercise will continue till April 30 to assess pre and post air quality scenarios, it said.