Seasonal Variation of Tropospheric Ozone and Its Association with the Chemical and Meteorological Precursors in Delhi, India

Abstract

In the present study, profile of tropospheric ozone and its variation with its chemical and meteorological precursors has been assessed in Delhi. The ambient air of Anand Vihar ISBT was found to be mainly dominated by NOx (335 ug/m3) and BTX (Benzene-12.2 ug/m3, Toluene -37 ug/m3 and pXylene -8.2 ug/m3) amongst the selected sites of Delhi. NOx was found to be predominately high due to high vehicular traffic, fireworks during festivals and crop burning in and around Delhi during November 2015. The concentration of benzene was exceeding the permissible standards in all the selected sites of Delhi. The study also revealed that the highest annual concentration of tropospheric Ozone (56.2 ± 23.5 ug/m3 ) was reported from Punjabi Bagh among the selected sites of Delhi and was recorded primarily in summers (March 2016-June 2016). The results indicate that higher temperature, lower humidity and high intensity of solar radiation contribute to the formation of tropospheric ozone in Delhi. The minimum concentration of ozone was recorded during the monsoons (July, 2016-September, 2016). This indicates the high humidity, large cloud cover, low intensity of solar radiation which could have been the reason for slowdown of the photochemical process. A positive correlation was observed between tropospheric ozone and ambient temperature in Delhi.