Characteristics of near-surface air pollutants at an urban station in the central Indo-Gangetic Basin

Abstract

Measurements of near-surface air pollutants at an urban station, Lucknow have been studied at two contrasting sites as residential and industrial during three-year period from 2015 to 2017 to understand their variability on different temporal scales. The annual mean mass concentrations of sulphur dioxide (SO2), nitrogen dioxide (NO2), nitric oxide (NO) and particulate matter of size less than 2.5 µm (PM2.5) at an industrial site were about 10 ± 5, 28 ± 17, 10 ± 11 and 128 ± 99 µg m-3 and at the residential site were about 8 ± 5, 30 ± 21, 9 ± 7 and 102 ± 81 µg m-3 respectively. It was observed that the annual mean mass concentration of PM2.5 was about 3 times higher than its annual National Ambient Air Quality Standards (NAAQS) level. However, SO2 and NO2 were about 5 and 1.5 times lower to their annual NAAQS levels, respectively. The seasonal mean mass concentrations of all the pollutants were found to be highest during the winter/post-monsoon season at both the sites, which are more pronounced at industrial site compared to residential site. The observed high pollutants over the station during the winter/post-monsoon season were found to be largely associated with the air mass back-trajectories from N-NW direction.