Abstract

This paper presents the observations of continuous measurements of surface Ozone (O₃) and Oxides of Nitrogen (NO_x) present in the ambient air over Kannur University Campus (11.9º N, 75.4º E, 5m), Kerala State, India from November 2009 to October 2010. The diurnal cycle of surface O3 concentration exhibited a peak in the afternoon and declined during nighttime on all days of observation. Likewise, the annual average diurnal variation of O₃ mixing ratio showed a minimum of (3.2 ± 0.7) ppbv in the morning and a maximum of (30.3 ± 10.4) ppbv at noon. The highest mixing ratios of surface O₃ observed during winter and summer at this site were 44 ppbv and 33.4 ppbv respectively and that during the monsoon and post-monsoon seasons were 18.5 ppbv, and 28 ppbv respectively. The diurnal profile of NOx (NO+NO₂) showed a peak during the early morning hours and decreased during the noontime. Correlations between O₃ with NO, NO₂ and NO_x with NO, NO,sub>2 has discussed in detailed. The concept of total oxidant, OX (O₃+NO₂) has been introduced, and found to vary with the level of NO_x. The influence of relative humidity and temperature on the variation in O₃ is discussed. The variations of O₃ in different months were elucidated with the aid of backward air trajectories of CGER-METEX reanalysis data.

Keywords:  Surface ozone; Photochemical production; NOx ; Oxidant; Air quality