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 (PM_2.5) 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 PM_2.5 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.