Significant decrease observed in levels of PM10, PM2.5 and nitrogen dioxide during lockdown period across all stations
The Rajasthan Pollution Control Board (RSPCB) has been regularly tracking the impact on air quality of nationwide lockdown imposed to curb the novel coronavirus disease (COVID-19) outbreak.
The observations bear the potential to examine how different cities are witnessing changes in air quality with the industrial and vehicular activities largely shut during the period. This may also help in designing future air quality management strategies.
The RSPCB has a network of 10 continuous ambient air quality monitoring stations (CAAQMS) in the state — three in Jaipur and one each in Alwar, Ajmer, Bhiwadi, Jodhpur, Kota, Pali and Udaipur.
The Board released the trend data for air quality in the state — the first state pollution control board to do so.
A brief analysis of data generated from these CAAQMS stations regarding Air Quality Index (AQI) and prominent pollutants such as PM10, PM2.5 and nitrogen dioxide showed varying trends during pre- and post-lockdown periods.
A 27 per cent decrease in PM10 levels was witnessed at Shrinath Puram. The improvement in air quality can be attributed to vehicles remaining off roads and all non-essential industrial units shut.
The city also registered a pronounced decrease in pollution levels due to stringent restrictions on travel, movement of vehicles, commercial activities and reduced contribution of road dust re-suspension.
The AQI deteriorated in all towns except Alwar and Kota in post-lockdown-II as compared to lockdown-I. The air quality in the two cities improved by 2-18 per cent in lockdown-I. Concentration of PM10 under lockdown-II also increased at all stations except Ajmer, Alwar and Kota.
The city recorded a 69 per cent decrease in PM10 at Bhiwadi- RIICO Ind. Area III, while the percentage decrease of PM2.5 was 71 per cent. The average AQI moved to satisfactory form poor during the lockdown phase.
Bhiwadi has been categorised as one of the critically polluted industrial clusters of Rajasthan by CPCB, but the lockdown resulted in substantial improvement in air quality there.
Closure of industrial units and subsequent reduction in vehicular traffic and re-suspension of road dust helped the situation. The city observed high reduction in individual pollutants — around 70 per cent — in the concentration of PM10, PM2.5 and oxides of nitrogen.
In the lockdown-II, the average AQI of all cities except Bhiwadi and Alwar remained in satisfactory category. In Bhiwadi, the air quality moved to moderate from satisfactory.
The average AQI of all the cities except Bhiwadi remained in satisfactory/good categories even in the lockdown-II.
The average AQI has moved to satisfactory from moderate in the lockdown period. The concentration of PM2.5 under lockdown-II increased at all the stations except Ajmer, Alwar and Jodhpur.
The average AQI moved to satisfactory from moderate at Police Commissionerate and Shastri Nagar. A significant percentage decrease in PM10, PM2.5 and nitrogen dioxide was observed during lockdown-I and II at all monitored stations except Adarsh Nagar and Science Park in the city.
The PM10 concentration during lockdown-II did not show any decline. The NO2 concentration reduced in all towns during lockdown-II as compared to lockdown-I except at Jaipur (Shastri Nagar), where it increased marginally.
Ajmer recorded a notable reduction of 87 per cent in the concentration of oxides of nitrogen and around 60 per cent decline in the concentration ofPM10and PM2.5 during lockdown -II.
The city witnessed a 27 per cent decline in PM2.5 and a 21 per cent decrease in NO2 at Pali-Indira Colony during the entire lockdown period as compared to pre-lockdown period. The average AQI moved to satisfactory levels from moderate.
The lockdown improved ambient air quality in the state. The AQI at all stations improved to satisfactory from moderate/poor.
Cities where the dominant source of air pollution was vehicular and road dust re-suspension also witnessed significant decrease in the concentration of major pollutants. Reduction of PM2.5 was more pronounced in lockdown-II.
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