Surface ozone scenario and air quality in the north-central part of India

Tropospheric pollutants including surface ozone (O-3), nitrogen dioxide (NO2), carbon monoxide (CO) andmeteorological parametersweremeasured at a traffic junction (78 degrees 2'E and 27 degrees 11'N) in Agra, India from January 2012 to December 2012. Temporal analysis of pollutants suggests that annual average mixing ratios of tropospheric pollutants were: O-3 - 22.97 +/- 23.36 ppbV, NO2 - 19.84 +/- 16.71 ppbV and CO - 0.91 +/- 0.86 ppmV, with seasonal variations of O-3 having maximummixing ratio during summer season (32.41 +/- 19.31 ppbV), whereas lowestwas found in post-monsoon season (8.74 +/- 3.8 ppbV). O-3 precursors: NO2 and CO, showed inverse relationship with O-3. Seasonal variation and high O-3 episodes during summer are associated with meteorological parameters such as high solar radiation, atmospheric temperature and transboundary transport. The interdependence of these variables showed a link between the daytime mixing ratios of O-3 with the nighttime level of NO2. The mixing ratios of CO and NO2 showed tight correlations, which confirms the influence of vehicular emissions combined with other anthropogenic activities due to office/working hours, shallowing, and widening of boundary layer. FLEXTRA backward trajectories for the O-3 episode days clearly indicate the transport from the NWandWto S/SE and SWdirection at Agra in different seasons. (C) 2017 The Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences. Published by Elsevier B.V.