Investigation of Surface Ozone by Exploring Chemical Kinetics in the Urban and Rural Locations of Kannur - A Tropical Site in India

Abstract

The photolysis of nitrogen dioxide (NO₂) is the only known source of ozone forming chemistry in the troposphere in the daytime. This paper presents the theoretical investigation of the photolysis rate coefficient of NO₂ - J_NO2^, using solar flux data for the estimation of surface ozone concentration at two sites in Kannur, Kerala, India. For this purpose, the variations of solar flux and NOx observed during winter months in 2009 and 2010 have been used. The study was carried out at two locations of different characteristics: at Kannur University Campus (KUC) at Mangattuparamba, a rural location and at Kannur Town (KT), an urban location. The observations revealed that surface ozone abundance is higher at rural area than at urban area. The mixing ratio of O₃ measured in the troposphere is often greater than those calculated from the photo stationary state relationship. Surface ozone is mainly produced by the photo dissociation of nitrogen dioxide (NO₂) by solar UV radiation. This observation could confirm the role of other prominent ozone precursors like CO, CH₄ and VOCs present over these locations. This study contributes to the understanding of ozone producing chemistry and to explore the air quality over this unexplored region.