Variation of ambient air pollutants concentration over Lucknow city, trajectories and dispersion analysis using HYSPLIT4.0

Abstract

The present study deals with the analysis of daily average concentrations of respirable suspended particulate matter (RSPM- PM10), sulfur dioxide (SO2), and nitrogen dioxide (NO2) at seven monitoring stations namely, Hazratganj, Talkatora, Mahanagar, Aliganj, Sarai Mali Khan, Gomtinagar, and Ansal TC in Lucknow city from 2016 to 2020. The analysis shows that the annual average concentration of RSPM varies from 148.74 to 323.05 µg/m3, SO2 varies from 7.11 to 8.94 µg/m3 and NO2 from 23.52 to 31.86 µg/m3 at all the locations. From the analysis of seasonal variation, it is found that the minimum concentration of RSPM found to be 81.59 µg/m3 in monsoon and maximum concentration was found to be 447.47 µg/m3 in post-monsoon. However, the seasonal variation of SO2 was found in the range of 5.55 to 10.94 µg/m3 and NO2 in the range of 20.23 to 38.40 µg/m3, which are below the prescribed standards. The pollution level decreased to some extent due to the COVID-19 lockdown in the year 2020 but not below the prescribed standard for RSPM. The levels of PM10 in Lucknow are not reducing despite the government of India banning industries and adopting other safeguards within the city. The Trajectory and Dispersion study using the HYSPLIT4.0 model shows insufficient local pollution control, and pollutants are carried from adjacent locations due to the wind blowing from north-west direction to keep daily pollution levels over the standards prescribed by Central Pollution Control Board (i.e., 100 µg/m3). The peak concentration of RSPM is recorded to be 323.05 µg/m3 for the year 2017 at the Hazratganj monitoring station. Over the study region, wavelet analysis of monthly averaged values of PM10 data sets at all seven stations revealed that the presence of semi-annual and annual periodicity. The findings reveal that controlling of particulate matter pollution in the city is a significant concern and has an alarming situation as compared to SO2 and NO2 pollutants.