Relationship of Surface Ozone (O3) with its precursors and meteorological parameters over New Delhi, India

Abstract

In the present study, continuous measurements of Surface Ozone (O₃), Oxides of Nitrogen (NOx (NO+ NO₂)), and carbon monoxide (CO), monitored at five different locations in Delhi National Capital Region have been studied for the period 2013 – 2019. The five monitoring locations used are namely IMD Lodi Road, IGI Airport Palam, CV Raman Dheerpur, CRRI Mathura Road, and NCMRWF Noida. The average hourly concentration of O₃, NO, NO₂, CO, NOx (NO + NO₂), and OX(NO₂ +O₃) are found in the range of  32.44 ppb to 36.57 ppb, 19.46 to 28.09 ppb, 20.83 to 26.89 ppb,1.67 to 1.89 ppm,43.04 to 54.99 ppb, and 54.06 to 60.99 ppb respectively during the study period. Diurnal variation of NOx and CO Concentrations show higher values during the morning (0600-0900h) and late evening (1900-2400h) hours while the highest concentrations of ozone have been observed during afternoon hours. The relationship between NO, NO₂, and surface O₃ as a function of NOx has also been examined during daylight hours (0500hrs IST to 1900 hrs IST) and chemical coupling of the three species i.e. NO, NO₂ and O₃ have been studied. The ground-level concentration of Ozone has been found to decrease with increasing NOx concentration during the daytime. The variations in concentrations of oxidants (NO₂ + O₃) with the concentration of [NOx] have been studied to examine the contributing pollution sources of oxidants at all the study sites. The average rate of change of O₃ concentrations (dO₃/dt) has been examined at all five locations. The monthly and diurnal variation of oxidants [OX] at all the study locations has shown a strong positive correlation with temperature whereas a negative correlation with humidity.