The first week of odd-even II saw a "decrease" in pollutants but air quality fell thereafter owing to reduced wind speed, crop burning, with blazes at landfill sites and forest fires in Uttarakhand being added factors, a report by the Delhi Pollution Control Committee (DPCC) has said.
The DPCC report, based on monitoring at three levels undertaken before, during and after the scheme was enforced, has concluded that pollution levels increased due to dip in wind speed and farm fires from April 22, in line with the findings of green body CSE.
Analysis of data obtained from the six fixed stations, that conduct real-time monitoring of pollutants across the year, show that levels of fine respirable pollutants PM 2.5 and PM 10 rose marginally during the first week as well, although the spike was sharper in the second week.
The average value of PM 2.5, recorded at 89 micrograms per cubic metre (ug/m3) between April 6-14, went up to 111 during the first week of the scheme and 154 in its second week. Wind speed fell from 1.6 to 1.1 metres per second during the period.
PM 10 rose from 323 ug/m3 in the first week to 360 ug/m3 while level of NO2 rose from 63 ug/m3 to 93 ug/m3. The safe standards of PM 2.5 and PM 10 are 60 and 100 respectively.
"The analysis of the data generated before, during event and after the event shows that the total period was highly influenced by metrological parameters like wind speed, wind direction, ambient temperature.
"It is also observed that local and trans-state movement of pollutants also influenced the air quality of Delhi. The probable factors are crop residue burning in Haryana, Punjab, local fire in Delhi including fire in land fill sites and Uttrakhand fire might also had effect on ambient air quality," the report said.
The three-tier monitoring was done at the level of the
six fixed stations, through the application of light scattering technique at 74 locations and manual monitoring at 20 residential, 15 industrial locations. The report will be submitted to National Green Tribunal on Monday.
The 74 locations included 21 locations on the seven borders of Delhi where one sample was taken inside Delhi (1-2 km), second sample was on border and third sample around two kilometres inside the neighboring state and also the ring roads which see heavy traffic volume.
The level of PM 2.5 and PM 10 decreased between April 15-21 in areas such as ITO, Pragati Maidan, Delhi Secretariat, Munirka, Sarai Kale Khan, Model Town while they shot up in areas like Ghazipur, Anand Vihar, Noida border, Bhajanpura and Wazirabad.
"The analysis of data shows that for PM 10, range was almost same in the locations of Delhi central and Outer ring road. However, at borders slight increase from pre event concentrations was observed and a decrease from 1-6 May (post event) was observed.
"While at inner ring road, a decrease was observed in the first week. In PM 2.5 concentration, the reduction was observed at the locations Delhi's central areas and inner ring road. In the second half, increase was observed at all the locations for PM 2.5 and PM 10," it said.
Same trends emerged in the results of the manual monitoring in residential and transport impacted areas where PM 2.5 levels decreased during the first week although the same increased in industrial areas, the report said.
