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

Tropospheric pollutants including surface ozone (O₃), nitrogen dioxide (NO₂), carbon monoxide (CO) and meteorological parameters were measured at a traffic junction (78°2' E and 27°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: O₃ - 22.97±23.36ppbV, NO₂ - 19.84±16.71ppbV and CO - 0.91±0.86ppmV, with seasonal variations of O₃ having maximum mixing ratio during summer season (32.41±19.31ppbV), whereas lowest was found in post-monsoon season (8.74±3.8ppbV). O₃ precursors: NO₂ and CO, showed inverse relationship with O₃. Seasonal variation and high O₃ 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 O₃ 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 O₃ episode days clearly indicate the transport from the NW and W to S/SE and SW direction at Agra in different seasons.