Concentrations of surface O₃, NO₂ and CO during winter seasons at a semi-arid region – Agra, India

Abstract

Surface measurements of O₃ (ozone) and its precursor gases such as NO₂ and CO have been made over an urban site of Agra (semi-arid region). Ozone and NO₂ show diurnal variations to an urban site during winter season. The overall increase of ozone is attributed to the increase in NO₂, CO and other precursor’s emissions by different sources in the proximity of both the sites, i.e. St. John’s College (SJC) and Dayalbagh. The average concentration of ozone was found to be 27.3 ppbv and it ranges from 1.2 to 69.0 ppbv, whereas the average concentration of NO₂ and CO were 66.3 ± 7.0 ppbv and 710.3 ± 159.4 ppbv, respectively. The coefficient of determination of regression curve between O₃ and NO₂ were r = 0.50 at SJC and r = 0.68 at Dayalbagh, whereas correlation between O₃ and CO were r = 0.75 at SJC and r = 0.50 at Dayalbagh, indicating positive correlation. Air samples from the two different locations of Agra city have indicated that the concentrations of ozone and CO were within the permissible limits but NO₂ concentration was above the limit.