Although nine other cities, whose ambient air quality figures were closely scrutinized during the March 25-May 3 period, also experienced a positive effect on air quality due to severely restricted human activities, the central watchdog of pollution does not endorse such restrictions for the sake of cleaner air, saying that “these air quality management strategies carry considerable economic costs.”
Therefore, it suggests irreversible emission reductions through sustainable process changes with an emphasis on reducing emissions at the source, including dust control, vehicular emissions and industrial operations.
Underlining the “strict application” of the rules to deal with the threat of air pollution, the CPCB also suggests “closing inefficient power plants” in the country and says that the lessons learned from the Covid-19 pandemic can be use “to target specific sources actions” that will lead to maximum improvement of ambient air quality.
The analysis of the data in the report, published on the 46th day of the founding of the CPCB, shows that Chennai, Bangalore and Mumbai reported that the 40 days of the first two phases of the blackout period were “good” or “satisfactory” in terms of having a clean air quality level.
However, Chennai shows the maximum number of days with ‘good’ air quality (26) followed by Bengaluru (7) and Mumbai (7). Delhi during the period reported only one day of “good” air quality and 21 days “satisfactory” and the remaining 18 days as “moderately” polluted.
Among the five cities in NCR, Noida reported the maximum number of “good” and “satisfactory” days (25), combined, followed by Delhi (22), Gurugram (19), Ghaziabad (16) and Faridabad (13).
The CPCB stresses that although the air quality in the 12 cities during the severely restricted human activities situation improved substantially with the reduction in the levels of different pollutants in the range of 30-60% during the pre-closure phase, it also improves. could have been influenced by the location. and number of monitoring stations, as well as the prevailing meteorological and topographic conditions.
“While cities like Delhi and Indore are landlocked, the influence of the sea affects atmospheric chemistry from cities like Mumbai, Chennai and Kolkata, ”says the report, prepared under the direction of CPCB member secretary Prashant Gargava.
Among its various suggestions for improving air quality in cities, the report, “Impact of the blockage on ambient air quality”, proposes an “air basin approach”, defining regional air basins to control the most polluting sources. beyond the city limits, to counteract long-distance pollutant transport. .
“It is important to note that weather conditions, local sources near monitoring stations, and the distribution of monitoring networks in a city also impact ambient air quality. The Delhi-NCR cities saw similar levels of reduction, which may be due to the fact that they are within the same air basin, ”he says.
Referring to the source distribution study of PM2.5 in Delhi, the report says that sources associated with vehicular emissions, domestic / local coal combustion, waste incineration and urban organic aerosols were drastically reduced from the previous phase at the close to the closing-I phase and it was found that Get up constantly with increasing relaxations in the confinement.
A reduction in PM2.5 levels was observed in all cities during the run-up to closure and the first closure, except Mumbai. However, reductions were also achieved in Mumbai during the second phase of closure. Similar reductions in PM10 were seen in all cities except Mumbai during the pre-closure period in 2020 compared to 2019 along with year-over-year reductions in PM10 levels in all cities during both phases of closure.
“Comparing pollutant levels before and during Closure Phases I and II in 2020 shows significant reductions in NO2, PM2.5, and PM10 in all cities,” the report says.
In terms of particulate matter levels, while PM2.5 was reduced by 24% during the pre-lockout phase, it was further reduced by almost 50% during both lockdown phases compared to the levels observed during 2019. The PM10 was reduced by a massive 60%, with NO2 levels dropping by 64%, benzene by 62% and SO2 by 35%, during the second phase of lockdown compared to levels in the same period in 2019.
“There has also been a reduction in pollutant concentrations compared to pre-closure levels. There was a 38% and 33% reduction in PM2.5 and a 37% and 30% reduction in PM10 during the periods of Phase I closure and Phase II closure respectively, compared to pre-closure levels, “the report says.
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